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ASME Conference Presenter Attendance Policy and Archival Proceedings

2017;():V001T00A001. doi:10.1115/POWER-ICOPE2017-NS1.
FREE TO VIEW

This online compilation of papers from the ASME 2017 Power Conference Joint With ICOPE-17 (POWER2017-ICOPE-17) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Boilers and Heat Recovery Steam Generators

2017;():V001T01A001. doi:10.1115/POWER-ICOPE2017-3014.

The paper introduces four kinds of new combustion ways, namely reverse combustion, open fire counter burning, double layers and two-way combustion, forward and reverse combustion, to solve the environmental pollution of manual coal-fired oven in China from the aspect of the combustion technology. And it also designs the environment-friendly structure of the manual oven with the forward and reverse staged combustion and exchange filter via the coal seam staged combustion and exchange filtration technology on the basis of the forward and reverse combustion ways, and proposes specific measures from the prospective of policy, which have provided new technology to solve the environmental pollution of the manual coal-fired oven.

Topics: Combustion , Design , Filters , Ovens
Commentary by Dr. Valentin Fuster
2017;():V001T01A002. doi:10.1115/POWER-ICOPE2017-3264.

The trace element mercury (Hg0) released from fossil fuel combustion in thermal power plants is difficult to be collected by pollution control equipment as its high volatility, high volatility and low solubility. The removal of Hg0 is the most critical part of mercury removal technology. The existing technologies of mercury removal include activated carbon adsorption, fly ash adsorption, calcium-based adsorbent adsorption, and wet scrubbing method. While these existing technologies have some disadvantages, like high absorbent consumption, high absorption cost and existence of secondary pollution. Much attention has been devoted to the development of new mercury removal technology in recent years.

In this study, the Ca(ClO)2 solution was proposed for the absorption of elemental mercury as its strong oxidizing property and low expenditure. The chemical reaction mechanism, reaction kinetics and reaction thermodynamic in both absorption and regeneration processes were explored, which verified the feasibility of mercury removal and absorbent regeneration. Effects of solution concentration, absorption temperature and solution pH value on absorption performance of Ca(ClO)2 solution were investigated in micro bubbling reactor. The experimental results revealed that acid environment (pH = 1–5) and high solution concentration were beneficial to mercury removal. A high removal efficiency (over 90%) and a low outlet mercury concentration (below 0.01mg·m3) was obtained under optimal experimental parameters (with the pH value of 3, the solution concentration of 15 mmol·L−1 and the temperature of 25 °C). The performance of electrolytic regeneration in Ca(ClO)2 rich solutions were carried out, and the effect of electrolysis time on current efficiency and energy consumption in electrolytic regeneration processes were specifically studied. The regeneration results showed that the oxidation reaction of Cl with a series of other oxidation reactions will occur at the anode, and the reduction reaction of Hg2+ will occur at the cathode. The results verified the feasibility of the electrolytic regeneration of Ca(ClO)2 rich solution using an ion-exchange membrane insulating the catholyte and the anolyte. The Ca(ClO)2 solution is a promising absorbent for elemental mercury which can accomplish the cyclic utilization of solution and the reuse of mercury.

Commentary by Dr. Valentin Fuster
2017;():V001T01A003. doi:10.1115/POWER-ICOPE2017-3283.

The shell-and-tube waste heat boiler is a common facility to recover and utilize the energy of flue gas in industries. To improve the ability and efficiency of the boiler, a steam dome is configured above the drum so as to arrange more heat exchange tubes. Simulation and analysis of vapor-liquid two-phase flow across tube bundles arranged in the drum are of vital importance to design and safety operation. Numerical simulation of boiling two-phase flow across tube bundles in the drum was carried out to analyze the shell side thermal-hydraulics. Commercial software ANSYS FLUENT 14.5 was adopted for modeling and computational calculations. The applied modeling approach was validated against experimental results with a good agreement. In order to analyze the vapor-liquid two-phase flow performance under various working conditions, the inlet velocity of downcomer tubes of 3m·s−1, 4m·s−1 as well 5m·s−1 for saturated water were simulated, respectively. The pressure field, flow characteristic, void fraction distribution and heat transfer characteristic were analyzed to have a good knowledge of the boiler operation. The following conclusions have been drawn through analyzing simulation results. (1)The total pressure drop on shell side increased with increasing the inlet velocity of downcomer tubes of saturated water. (2)The velocity of saturated water decreased after flowing into the drum less than z = 0.1m as the flow area increasing, and then increased rapidly as the volume of the mixture two-phase flow increasing. (3)The integral average void fraction of the drum decreased as the mass flow rate of inlet saturated water increasing. (4)The HTC (heat transfer coefficient) of the heat exchange tubes varied with the flow direction, which is related to the vapor-water void fraction. The conclusions obtained above can be used as a reference for the design of the separated structure shell-and-tube waste heat recovery boiler.

Commentary by Dr. Valentin Fuster
2017;():V001T01A004. doi:10.1115/POWER-ICOPE2017-3291.

The ash deposition on low-temperature heat transfer surface is a key factor that deteriorates the heat transfer performance and leads to corrosion in the low pressure economizer. In the low temperature flue gas, ash deposition is closely related with acid condensation. The sulfuric acid vapor and water vapor contained in the flue gas will condense on heat transfer surface under low flue temperature, which will aggravate ash deposition. In order to evaluate the influence factors of ash deposition on low-temperature heat transfer surface, a laboratory experiment is carried out in this paper. The acid concentration of flue gas, the ash content, the ash component, the flue temperature and the temperature of heat transfer surface are considered to be the most important influence factors on ash deposition characteristics. The viscosity of ash deposition samples on the outer wall of the double-pipe is measured to describe ash deposition characteristics. The fouling factor is calculated. Meanwhile, the scanning electron microscope SEM is used to the analysis of ash samples obtained from the outer wall of the double-pipe. As conclusion, the changing regulation of viscosity of ash deposition on low-temperature heat transfer surface is obtained. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T01A005. doi:10.1115/POWER-ICOPE2017-3292.

This paper experimentally studied the heat transfer and frictional characteristics of a single rifled tube with vertical upward flow under the parametric range of pressures P = 10.5–32 MPa, mass fluxes G = 300–1300 kg·m−2·s−1, heat fluxes q = 275–845 kW·m−2. The results show that in the subcritical pressure region, dryout is the predominant mode of heat transfer deterioration. In the near critical pressure region, departure from nuclear boiling (DNB) occurs when the q/G value increases. In the supercritical pressure region, heat transfer and frictional characteristics will be strongly influenced by the sharp changes of the thermophysical properties of supercritical water when the value of mass flux is approximately lower than 1000 kg · m−2 · s−1 in this experiment. The mass flux and the pressure are two crucial factors to the variations of total pressure drop and frictional pressure drop. An empirical correlation is selected to estimate the frictional pressure drop. The results indicate that in the low mass flux circumstances, the calculated value significantly underestimates the experimental data in the large specific heat region. Whereas, when the value of mass flux is larger than 1000 kg · m−2 · s−1, the calculated value agrees well with the experimental data. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T01A006. doi:10.1115/POWER-ICOPE2017-3296.

Supercritical steam generator is a complex system, many factors affect its safety. According to relevant laws, regulations and standards, from three aspects including equipment conditions, operating conditions and technical management, the risk factors of supercritical steam generator are comprehensively analyzed. And a multi-level structure model is developed on the basis of above analysis. The results improve the safety management level of supercritical steam generator, and provide an important and scientific basis for the safety evaluation of supercritical steam generator.

Commentary by Dr. Valentin Fuster
2017;():V001T01A007. doi:10.1115/POWER-ICOPE2017-3303.

A new type of bypass staged economizer system is presented in this paper. The calculation model of the bypass staged economizer and ordinary LPE were established based on a 600 MW unit. The performance analysis for important operating parameters of the presented economizer system such as exhaust gas temperature and bypass flue gas ratio are carried out. Simulation results showed that, when the scheme of the bypass staged economizer was adopted, the temperature of the flue gas entering the electrostatic precipitator (ESP) can be reduced to 95°C, which can greatly improve unit efficiency, reduce standard coal equivalent (SCE) consumption by 2.8g/kWh. Compared with the traditional LPE, it can reduce SCE consumption by 1.59g/kWh. In addition, the technology can also achieve the active control of the exhaust flue gas temperature by changing the bypass flue gas ratio. The different flue gas temperatures correspond to different bypass flue gas ratios. And the optimum bypass flue gas ratio was calculated in different exhaust gas temperature conditions.

Commentary by Dr. Valentin Fuster
2017;():V001T01A008. doi:10.1115/POWER-ICOPE2017-3416.

Sanicro 25 material is approved for use in pressure vessels and boilers according AMSE code case 2752, 2753 and VdTüV blatt 555. It shows good resistance to steam oxidation and flue gas corrosion, and has higher creep rupture strength than any other austenitic stainless steels available today. It is a candidate material for superheater and reheaters, enabling higher steam parameters of up to about 650 °C steam (ie about max 700 °C metal) without the need for expensive nickel based alloys. The effect of cold-forming on time and temperature-dependent deformation and strength behavior has been examined in a comprehensive study. The objective was to determine the maximum allowable degree of cold-forming to be used without additional heat treatment. The findings of these investigations indicate that the maximum allowed cold deformation could be possible to increase from today’s maximum 20 % (VdTüV 555), 15 % (540–675 °C) and 10 % (higher than 675 °C) respectively (ASME 2011a Sect I PG19). A solution annealing after the cold bending will recover creep ductility but will also at the same time increase manufacturing costs. Higher allowed degree of cold-forming without the need for post bend heat treatments, would allow for more narrow bending radii and thereby a more compact construction that would result in a significant decrease in production costs. This paper presents the findings in the mentioned study and is to be a background for possible coming discussions with involved entities on a revision of the max allowed deformation of this material without the need for solution annealing.

Commentary by Dr. Valentin Fuster
2017;():V001T01A009. doi:10.1115/POWER-ICOPE2017-3463.

Recovering the waste heat of flue gas to reduce its temperature with avoiding low-temperature corrosion is an effective way to improve the economic efficiency of coal-fired power plant. A coupled high-low energy level flue gas heat recovery system was introduced in the paper. The inlet air temperature of air preheater and the temperature of turbine condensate can be increased by using this system. Thermal economy model of the system was built based on equivalent heat drop method. The system was successfully applied in 1000MW ultra-supercritical double reheat coal-fired unit in Laiwu Power Plant of China Huaneng Group, and the operation data showed the boiler flue gas temperature was not higher than 90° C, and the coal consumption was reduced by using the system. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T01A010. doi:10.1115/POWER-ICOPE2017-3471.

Supercritical and ultra-supercritical pressure boilers have been widely used in China because of its advantages of high capability, high thermal efficiency and low pollutants emission. In view of the high working parameters and complicated working conditions of such boilers, safe and stable operations of these boilers have become the focus of attention of related researchers and engineers for many years. As one of the most important phenomena that may occur in thermal power plants, flow instabilities of water in boilers’ water-cooled wall may result in heat transfer deterioration, thermal fatigue of pipes and even breakdown of the supercritical units, and have thus attracted much attention of developers and researchers of the boilers.

However, due to difficulties in carrying out experiments on the density wave oscillation of water under supercritical pressures, the related experimental data is very rare, and moreover, the characteristics of density wave oscillations of water under supercritical pressures has not been well understood.

A series of experiments have been conducted on the density wave oscillation of water flowing at supercritical pressures in a 6-m long vertical upward tube with 20.0-mm internal diameter. The experimental parameters cover the pressures from 23 to 27 MPa, the mass fluxes from 300 to 600 kg·m−2·s−1, and the heat fluxes from 225 to 500 kW·m−2. Three types of density wave oscillation were found in the present study: 1) stable periodic density wave oscillation, 2) attenuated density wave oscillation, 3) divergent density wave oscillation. Effects of pressures, mass fluxes and heat fluxes on the density wave oscillation were analyzed. With the increase in pressures and mass fluxes, the density wave oscillation of supercritical pressure water can be postponed, and is difficult to occur. And the density wave oscillation will be triggered and enhanced by increasing the heating flux. The mechanism of density wave oscillation of supercritical pressure water in tubes was also analyzed, and a dataset was established for the verification of related numerical calculations and modeling.

Commentary by Dr. Valentin Fuster
2017;():V001T01A011. doi:10.1115/POWER-ICOPE2017-3782.

Global warming is one of the most important topics in power generation field. Wood pellet is carbon neutral fuel and it is expected to reduce CO2 emission from fossil fuel. Recently in Japan, wood pellet is already utilized in many pulverized coal fired boilers in a limited range of a few percent. For the further CO2 emission reduction, high co-firing ratio of wood pellet is expected. The firing system of wood pellet is required to be separated from the coal firing system in the view point of technique, and it is desired to slightly modify the existing coal firing system from the view point of dissemination. IHI developed a wood pellet mill which equipped some devices to the coal mill. By modifying one coal mill in a commercial power plant to the pellet mill, grinding wood pellet was succeeded, and co-firing rate of 25 % was achieved. This paper shows the economic and technical evaluations of wood pellet utilization in coal fired power plant including the impact of lumbering to the forest.

Commentary by Dr. Valentin Fuster

Combustion Turbines

2017;():V001T02A001. doi:10.1115/POWER-ICOPE2017-3141.

Turbulent combustion flows in the partially premixed combustion field of a dry low-emission gas-turbine combustor were investigated numerically by large-eddy simulation with a 2-scalar flamelet model. Partially premixed combustion was modelled with 2-scalar coupling based on the conservative function of the mixture fraction and the level set function of the premixed flame surface; the governing equations were then used to calculate the gas temperature in the combustion field with flamelet data. A new combustion model was introduced by defining a nondimensional equilibrium temperature to permit the calculation of adiabatic flame temperatures in the combustion field. Furthermore, a conventional G-equation was modified to include spatial gradient terms for the adiabatic flame temperature to facilitate smooth propagation of a burnt-state region in a predominantly diffusion flame. The effect of flame curvature was adjusted by means of an arbitrary parameter in the equation. The simulation results were compared with those from an experiment and a conventional model. Qualitative comparisons of the instantaneous flame properties showed a dramatic improvement in the new combustion model. Moreover, the experimental outlet temperature agreed well with that predicted by the new model. The model can therefore reproduce the propagation of a predominantly diffusion flame in partially premixed combustion.

Commentary by Dr. Valentin Fuster
2017;():V001T02A002. doi:10.1115/POWER-ICOPE2017-3247.

In pursuit of a reduction in environmental loading, gas turbines equipped with lean premixed combustor technology that use a hydrogen-enriched fuel instead of pure methane have entered practical service. An accurate numerical simulation method is therefore needed to reduce product-development costs to a minimum. We performed a numerical analysis of an industrial combustor with a mixed methane-hydrogen fuel by large-eddy simulation and extending the 2-scalar flamelet approach to a multi-scalar one. The calculation object was the combustor of an L30A-DLE gas-turbine. Two calculations were conducted with different fuel compositions at the supplemental burner. In the first simulation, the inflow gas was composed of methane and air, whereas in the second simulation, the inflow gas was composed of methane, air, and hydrogen. The inlet boundary conditions were set so that both cases have the same adiabatic flame temperature at the outlet. The temperature distributions throughout the combustor were approximately equal in both cases. This study therefore suggests that equivalent performance can be obtained by setting the inflow condition at the supplemental burner so that the outlet adiabatic temperatures are equal for both monofuel combustion and mixed combustion.

Commentary by Dr. Valentin Fuster
2017;():V001T02A003. doi:10.1115/POWER-ICOPE2017-3301.

Acoustic coupling effect in the combustion of fuel is the root of causing the combustor liner vibration. When the excitation frequency and the combustor liner structure natural frequency coincides or nearly, the combustor liner will resonate even cause structural damage. In order to regulate natural frequencies of combustor liner structure to avoid the oscillation frequency effectively that under the working condition, combustor liner design must include appropriate research and experimental verification of its vibration characteristics. The effectiveness of the combustor liner vibration design method and the reliability of combustor liner safe operation are verification effectively by vibration analysis and measurement investigation of gas turbine combustor liner. Technical support and follow-up to ensure safe operation of the new combustor liner design can be provided.

Commentary by Dr. Valentin Fuster
2017;():V001T02A004. doi:10.1115/POWER-ICOPE2017-3304.

The tip clearance of the compressor has always been a key part in both the design and operation of gas turbine. Surge margin and aerodynamic performance of the compressor will be affected if the tip clearance is too large, while risk of rubbing between the blades and casing will arise if the tip clearance is too small. Generally speaking, the calculation and analysis of tip clearance under stable design condition is relatively easy, because the metal temperature field of both rotor and stator components that significantly affect the tip clearance is in stable condition at that time. However, the transient tip clearance under start-up and shut-down condition is difficult to be calculated and analyzed, due to the fact that both the aerodynamic parameters and metal temperature field are instable, and complicated heat-exchange occurs between the metal components and gas.

In this paper, the transient deformation of both rotor and stator components of compressor of a certain gas turbine is analyzed in detail by using thermo-solid coupling analysis technology, finally obtained real-time tip clearance. The non-contact measurement technology is used to measure the tip clearance during operation of the unit. The experimental result indicates that the real-time tip clearance value obtained by the calculation method in the paper is in a very good agreement with the measured value. In addition, both the analysis and experimental results show that the moment of smallest tip clearance usually happens at shut-down progress and the influence of tip clearance must be considered when designing unit’s running curve.

Commentary by Dr. Valentin Fuster
2017;():V001T02A005. doi:10.1115/POWER-ICOPE2017-3374.

A novel concept for shear flow driven gas compression that could enable next generation turbomachinery has been designed and experimentally demonstrated. In order to achieve this, a prototype proof-of-concept compliant foil-based bladeless turbo-compressor device was developed and used to conduct a gas compression parametric study. The principle underpinning the operation of this device is the conversion of shaft power into hydrodynamically generated pressure that occurs in the shear flow between a smooth rotating disk and a compliant surface. The present compliant foil bladeless turbocompressor (CFBT) is an evolutionary derivative of self-acting compliant foil bearings and seals, which operate in the hydrodynamic regime. Thus, as in these devices, the process of compression induced by shear flow is dominated by the balance between pressure and viscous forces, which are in turn enhanced and controlled by tribological effects arising between the shear layer and the deformable geometry of the compliant surface. The single shaft foil bearing based proof-of-concept CFBT presented is powered by a permanent magnet motor capable of reaching speeds up 360,000 rpm, and consists of two independent compression stages mounted on opposite ends of the shaft. Each compression stage consists of a smooth disk with the effective corresponding counterface of radii 7.6 mm < r < 14.1 mm, with one of each disk’s surfaces facing a four-pad compliant foil surface mounted on the housing. The nominal initial gap separating each of the disks from their corresponding compliant foils is nominally h0 = 0.025 mm and 0.4 mm, respectively. In this configuration, air is entrained from opposite directions through axial intakes and turned 90° as it undergoes shear between the rotating disk and the compliant foil pads of each of the stages, inducing a net radially-oriented outward flow, which is then collected in the quasi-volute of the respective stage. The system is heavily instrumented, with each of the quasi-volutes fitted with thermocouples, pressure probes and a flow meter. An experimental parametric study was performed compressing standard temperature and pressure air for varying speeds up to 360,000 rpm. Performance curves reporting flow vs. pressure as well as compression power requirements vs. speed were obtained for the individual compression stages. The experimental results on the proof of concept turbocompressor are analyzed in the context of the theoretical foundations presented in a companion paper (Heshmat and Cordova, 2017), showing excellent correlation. It is anticipated that due to its simple bladeless geometry, application of this novel technology in conjunction with foil bearings will result in low cost, ultra-high speed, high efficiency, high specific power, miniaturized turbocompressors and high power density oil-free and maintenance-free machines, such as compressors, meso-scale gas turbines, or turbogenerators. Attractive applications for this technology range from military micro-UAV propulsion and portable power systems, to domestic combined heat and power (CHP) turboalternators and medical devices such as portable oxygen concentrators and CPAP (Continuous Positive Air Pressure) machines.

Commentary by Dr. Valentin Fuster
2017;():V001T02A006. doi:10.1115/POWER-ICOPE2017-3375.

The theory underlying a novel method of gas compression driven by shear flow for next generation turbo-machinery is presented. The concept is based on the conversion of shaft power into hydrodynamic pressure and fluid flow that occur in the shear flow between a smooth rotating disk and a compliant surface counterface. This also holds for the inverse process, where gas expansion through the gap between the compliant surface and a shaft-mounted disk converts gas pressure into rotating power and torque.

This is a logical evolutionary step that leverages the proven functionality of self-actuated fluid film compliant foil bearings and seals which operate in the hydrodynamic regime. Thus, as in these devices, the process of compression induced by shear flow is dominated by the balance between pressure and viscous forces which are in turn enhanced and controlled by tribological effects arising between the fluid film and the geometry of the counterface compliant surface.

A model based on the compressible Reynolds equation coupled to the thin-plate theory formulation for compliant foil deflection is presented and parametrically solved to predict pressure, flow rate, and shear losses. The smooth disk and four-pad (sectored) compliant counterface effective size (7.6 mm < r < 14.1 mm), disk operating speed (50,000 to 360,000 rpm), nominal initial gap (0.03 mm < h0 < 0.635 mm), and overall operating conditions chosen for the parametric study correspond to those envisioned for eventual practical integration of miniaturized external combustion bladeless gas turbine engines and turbocompressors. Theoretical performance curves reporting flow versus pressure as well as compression power requirements versus speed were obtained. The predictions of the analysis are compared to results obtained experimentally on a proof of concept engine and presented in a companion paper.

The simplicity of the bladeless geometry makes it amenable to deployment in multistage configurations, so that in conjunction with its foil bearing predecessors, this novel technology will result in low cost, ultra-high speed, high specific power and power density, high efficiency, oil-free and maintenance-free engines — attractive for many practical applications, ranging from military micro-UAV propulsion and portable power systems, to domestic combined heat and power turboalternators, and even micro-compressors for portable medical devices. As a point of reference, it is anticipated that a 10-stage bladeless compressor based on a compression stage as described herein would have a size comparable to that of a 355 mL soda can delivering a flow of 1 kg/min of compressed air.

Commentary by Dr. Valentin Fuster
2017;():V001T02A007. doi:10.1115/POWER-ICOPE2017-3409.

This paper has studied the stress distribution and deformation of the fourth stage turbine blades and disk of a certain kind of heavy gas turbine with FEM method. The calculating model is assembled turbine blades and disk, and the analysis includes 2-D and 3-D situations. By calculating under centrifugal force and thermal loads, the conclusion of whether the turbine blades and disk were safe and the strength characteristics were drawn. The results shown that stress concentration of the structure is a problem that can’t be ignored. To enhance the security of structure, optimizing of the structure is recommended. Also, the results shown that structure deformation is caused mostly by thermal load and structure stress is caused mostly by centrifugal force. ( CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T02A008. doi:10.1115/POWER-ICOPE2017-3419.

Toshiba has been developing a turbine and a combustor for a semi-closed recuperated Brayton cycle of supercritical carbon dioxide called the Allam cycle, which is capable of both sequestrating 100% of carbon dioxide generated by combustion and providing electricity with competitive efficiency as the advanced combined cycle. The 25 MWe class demonstration plant with natural gas for this innovative cycle is being constructed in the USA by NET Power LLC and its operation is expected to be in 2017. Toshiba is going to provide the main components of its turbine and combustor.

This paper describes the specification of the turbine and the combustor and consideration necessary to realize them in the first of a kind design condition of 30MPa with a supercritical carbon dioxide as its working fluid. This paper also describes some of the validation tests to realize new technologies before this turbine and combustor are installed and operated in the demonstration plant.

Commentary by Dr. Valentin Fuster
2017;():V001T02A009. doi:10.1115/POWER-ICOPE2017-3624.

The current development of detonation based combustors has triggered the necessity to develop new turbomachinery design procedures to achieve operable and efficient fluid machines. The high-speed flow typically observed at the outlet of a rotating detonation combustors leads to a rather challenging turbine design. The present paper reports the development of a tailored methodology to predict the non-isentropic operation of turbines exposed to supersonic inlet conditions. This one-dimensional design procedure starts by identifying the operable design space, and uses empirical loss models to estimate the main sources of inviscid and viscous losses. The turbine performance is analyzed for different design choices and compared with three dimensional computational fluid dynamic results.

Topics: Turbines
Commentary by Dr. Valentin Fuster

Energy Water Sustainability

2017;():V001T03A001. doi:10.1115/POWER-ICOPE2017-3763.

A new dataset released by the Energy Information Administration (EIA) — which combines water withdrawal, electricity generation, and plant configuration data into a single database — enables detailed examination of cooling system operation at thermoelectric plants at multiple scales, most importantly at the unit level. This dataset was used to explore operations across the population of U.S. thermoelectric plants, leading to the conclusion that roughly 32% of all thermoelectric water withdrawal occurs while power plants are not generating electricity. Based on interviews with industry representatives, a unit’s location on the dispatch curve will largely dictate how the cooling system is operated. Peaking plants and intermediate plants might keep their cooling system running to maintain dispatchability. Other considerations include minimizing wear and tear on the pumps and controlling water chemistry.

This observation has implications for understanding water use at thermoelectric plants, policy analysis, and modeling. Previous studies have estimated water use as a function of cooling technology, fuel type, prime mover, pollution controls, and ambient climate (1) or by calculating the amount of water that is thermodynamically necessary for cooling (2). This, however, does not capture all the water a plant is withdrawing simply to maintain dispatchability. This paper uses the new data set from EIA and interviews with plant operators to illuminate the role cooling systems operations play in determining the amount of water a plant withdraws.

Topics: Cooling systems
Commentary by Dr. Valentin Fuster
2017;():V001T03A002. doi:10.1115/POWER-ICOPE2017-3767.

Energy and water are mutually dependent, limited resources that are critical to the development and economic stability of the United States. Energy production requires large volumes of water, and water treatment and distribution requires large amounts of energy. In 2010, water and wastewater treatment accounted for roughly 1.8% of total electricity use in the United States, which corresponded to 69 TWh per year or, in terms of power-generating capacity, over 7.8 GW. Population growth and climate change will result in increased demand on these limited resources, making them not sustainable at present use levels.

In recent years, both forward osmosis (FO) and membrane distillation (MD) have garnered significant attention as next-generation water desalination and reuse technologies with the potential to significantly reduce the energy cost associated with wastewater treatment. Critical technical hurdles and lack of operational understanding, however, have limited development of these individual technologies beyond the laboratory scale. In FO, a draw solution that produces high osmotic pressure but is still easily separable is a major challenge limiting the applicability of this process. The use of MD has been limited by membrane flooding due to oily and surfactant like compounds in industrial wastewaters and the transfer of volatile compounds across the membrane. Combining these technologies in a hybrid process overcomes their individual limitations, while exploiting the benefits of each. Effectively the FO unit pretreats the resulting diluted FO draw solution that is sent to the MD for regeneration via low-grade heat and product water recovery. The regenerated (re-concentrated) draw solution is then recycled to the FO unit. A key advantage of MD is that it is not limited by feed-solution osmotic backpressure, making it ideal for regenerating high-osmotic-pressure FO draw solutions. This, in turn, leads to strong potential for the integrated FO/MD process to treat high-salinity wastewaters that are difficult to treat economically by conventional technologies. The product water leaving the MD unit will be extremely high quality and directly suitable for reuse.

With funding from the U.S. Department of Energy, RTI, in collaboration with industrial partner Veolia, has developed an integrated FO/MD process from lab to small pilot scale. In this presentation, pilot-scale testing efforts of this process technology with real industrial wastewater will be presented. Process performance data obtained on full-size FO and MD membrane modules as well as lessons learned from piloting scale-up and best application areas for the technology will be discussed.

Commentary by Dr. Valentin Fuster

Fuels, Combustion and Material Handling

2017;():V001T04A001. doi:10.1115/POWER-ICOPE2017-3015.

Reactive structures of hot diluted methane counter-flow diffusion flames have been characterized under air-fuel and oxy-fuel combustion condition, by using a standard OPPDIF code with a WSGGM model and a validated detail chemical mechanism. The result shows the gaseous radiation makes the peak temperature be lower and the distributions of temperature change greatly.

Characteristic of vanishing of pyrolytic region and increasing of thickness of heat release zones are investigated in detail. The reason for these is the overlap of zones for the positive heat release and the negative heat release. Meanwhile, the combustion regions are established based on Xf –Tf –ΔT sketch map. The results show that MILD combustion is easier to be achieved under oxy-fuel conditions but it is also easier to blown off.

Moreover, reaction pathways for feedback combustion and MILD combustion under both air- and oxy-fuel conditions are analyzed. The chemical reaction rate decreases one order of magnitude under MILD combustion. Also, the decreasing of the production of OH and H and the addition of CO2 makes the C1 branch the C2 branch changes greatly under both conditions for MILD combustion.

Commentary by Dr. Valentin Fuster
2017;():V001T04A002. doi:10.1115/POWER-ICOPE2017-3018.

Emissions reduction requirements lead to modification of the firing system to control NOx emission reduction, and/or the post combustion treatment of the flue gas to remove NOx, SO2 & particulates. It has also leads to installation of new renewable energy production systems. All of these measures are very expensive both in installation and operation costs, while utilities are looking for low cost options with a minimum impact on unit performance and reliability. Firing of methanol and its blends with other liquid fuels, in comparison with other renewable sources, is one of the main alternatives for meeting this target. Methanol is a clean burning fuel that is made from non-petroleum energy sources such as natural gas, coal, biomass and carbon dioxide. Using CO2 for methanol production leads to reducing of greenhouse gas emissions so that methanol can actually be called as enviro fuel. The blending of methanol with light fuel oil is one of the quickest and cheapest means for both replacing costly petroleum energy consumed in the existing power generation fleet and reducing emissions that lead to air pollution such as nitric oxides, carbon monoxide, air toxics and PM. Hence, methanol is a good candidate as an alternative fuel for power generation, since it is liquid and has several physical and combustion properties similar to fuel oil. For this reason, this study is aimed to evaluate gas turbine performance and emissions characteristics for different blends of methanol and light fuel oil. The results obtained from simulation of different light fuel blends were compared to those of actual burning. In this study we experimented with methanol fractions (from 0 to 100 % by heat) at different GT loads and found that the methanol and light fuel oil blends enabled us to significantly reduce NOx emissions with increasing of the methanol fraction. SO2 emissions were also reduced according to the methanol heat fraction. The final blend ratio optimization should be based upon environmental requirements and fuel price. CO emissions are slightly higher than the required level. Based on performed tests, the main reason for CO formation is high excess air, especially at partial loads and as a result of low combustion temperature (this conclusion is right for any fuel and its blends). In order to reduce CO emissions, proper air /fuel control is necessary (IGV, IBH etc). This conclusion is very important for conceptual design of gas turbines in general and particularly for GT conversion to methanol firing. Firing of methanol and its blends had no impact on GT performance and provides safe operation. The computer simulations provide support for these experimental findings and conclusions. The results of the performed tests analysis indicate that methanol firing is a potentially promising low cost technology for emissions’ reduction and may be implemented in existing and new gas turbines.

Commentary by Dr. Valentin Fuster
2017;():V001T04A003. doi:10.1115/POWER-ICOPE2017-3024.

Coal is regarded as important fuel because of its stable supply and low price, but coal is blamed for its CO2 emission. Japanese utilities are making efforts to improve thermal efficiency and to expand biomass co-firing. On the other hand, CCS technologies are under development as a countermeasure for global warming and demonstration projects planned in several power stations are announced in world wide. As CO2 capture from power station requires huge in-house power, thermal efficiency is deteriorated. To make a breakthrough, NEDO started a project to develop the high-efficiency oxy-fuel IGCC system. This system recirculates gas turbine exhaust gas to both gasifier and gas turbine combustor. Recirculated exhaust gas is used both to feed pulverized coal to gasifier and to dilute syngas in gas turbine combustor. The target efficiency is 42% at HHV basis, equivalent to state of the art coal-fired power station. Various studies were done to confirm the concept of this system and to develop fundamental technologies necessary for the system since 2008 to 2014 as NEDO project. Based on the achievements, the project made another step since 2015 as a five-year joint NEDO project with MHI and MHPS. This paper introduces the latest status of this project executed by CRIEPI by referring several related papers.

Commentary by Dr. Valentin Fuster
2017;():V001T04A004. doi:10.1115/POWER-ICOPE2017-3037.

Today there is a growing concern about the ramifications of global warming resulting from the use of fossil fuels and the associated carbon dioxide emissions. Oxy-fuel combustion is a promising response to this issue, since the product of the combustion is a CO2 rich flue gas, which requires no further separation from other emission gases and thus can be sequestrated, or utilized.

Here we present an analysis of a novel technology for combining oxy-fuel combustion with utilization of the CO2 rich flue gas for syntetic fuel production. The technology concept involves a new method of using concentrated solar energy for the dissociation of carbon dioxide (CO2) to carbon monoxide (CO) and oxygen (O2). Simultaneously, the same device can dissociate water (H2O) to hydrogen (H2) and oxygen (O2). The CO, or the mixture of CO and H2 (called Syngas), can then be used as a gaseous fuel (e.g. in power plants), or converted to a liquid fuel (e.g. methanol), which is relatively easy to store and transport, and can be used in motor vehicles and electricity generation facilities. The oxygen produced in the process can be used in oxy-fuel combustion or other advanced combustion methods in power plants.

In this study it is assumed that a typical sub-critical, 575 MW, coal firing power plant is converted to oxy-fuel combustion. The flue gases from that power plant are then used as raw material for fuel production. The aim of the study is to estimate the optimal conceptual design of a power generation plant, including liquid/gaseous fuel generation facility.

In the present study we used a series of special models for simulating the heat balance, heat transfer, performance and emissions of an oxy-fuel converted utility boiler. We also employed cycle simulation software that facilitates the optimization of an electricity generation plant with CO2 conversion to liquid fuel and usage of the fuel produced from CO2 for additional electricity production.

The simulation results show that the amount of fuel produced, additional power generated and power station self consumption may be changed over a wide range, depending on the size of the solar field, which provides the energy for the liquid fuel production.

The paper includes an overview of some of the key technical considerations of the new concept of CO2 conversion to fuel. Based on the obtained results it may be concluded that the methodology presented in this study is an attractive option for CO2 emission reduction, which can be implemented in existing and/or new power generation units. The technology proposed in this paper is not indented as an alternative for replacing coal combustion with natural gas, however may be used effectively with oxy-fuel combustion of either coal or natural gas.

Commentary by Dr. Valentin Fuster
2017;():V001T04A005. doi:10.1115/POWER-ICOPE2017-3055.

The current work presents the results of an experimental study that is conducted to investigate the effect of nanoparticles added to biodiesel-diesel fuel mixture. Nano-biodiesel-diesel mixture fuels were prepared by adding of multi-walled carbon nanotubes (MWCNTs). These nanoparticles were blended with biodiesel-diesel fuel in varying mass fractions using an ultrasonic stabilization. A diesel engine test rig was used to examine the effect of nanoparticles on engine performance and emission characteristics with a constant speed of 2500 rpm and different engine loads. The engine test results indicated that the biodiesel-diesel fuel blend slightly decreased the engine performance and increased its emission characteristics at all tested engine operating conditions. The use of nanoparticles was found to improve all engine performance parameters. Specifically, the maximum emission reduction was obtained at a dose level of 20 mg/l, where considerable emission reduction was observed; NOx by 14 %, CO by 30 %, and UHC by 34 %. Also, the best of both engine combustion characteristics and performance were reached at a dose level of 40–50 mg/l. Where the reduction in the brake specific fuel consumption was by 16 %, the increase in both the cylinder peak pressure Pmax, and maximum gross heat release rate dQg/dθmax. were 4 % and 1%, respectively. Finally, the recommended dose level to achieve a significant enhancement in all engine performance is 40 mg/l.

Commentary by Dr. Valentin Fuster
2017;():V001T04A006. doi:10.1115/POWER-ICOPE2017-3057.

Low rank or grade coals (LGC) are widely distributed over the world. Coal plays a vital role in the global energy demand especially through power generation and it mitigates the energy poverty. The major challenges by the utility of coal as regarding to energy security, a risk of climate change, and increasing of the energy demands are the main portfolio to develop the advanced technology for coal beneficiation. The gradual depletion of high quality coal and cost effective which become a significant issue for power generation while the low grade coals were served as low cost fuel and as an alternative energy security issue. In current research the low grade coal (>35% ash) has been upgraded to higher grade (<10%) by chemical cleaning method. The low grade coal was selected from Mahanadi Coalfields Limited, Odisha, India. Each test was conducted of 50 g coal (250 μm particle size) with 40% NaOH at 100 °C for 3 h and followed with 20% of H2O2, H2SO4, HCl, and HF acids at similar conditions. The research study revealed that ash content (mineral matter) of coal is reduced to >70% by NaOH followed HF treatment as compared to other solvents. The greater liberation of mineral results increases the ash reduction from low grade coal because mineral associated in the coal matrix may formed elution by the leaching effect. The greater extent of demineralization was caused due to the high affinity of OH and F with minerals in the coal matrix. The characterization of pre and post treatment coal and coal ash was investigated by the FESEM, XRF and XRD analysis. Overall the current research study challenges the chemical cleaning of low grade coal has been efficient techniques for reducing the minerals to a certain limit.

Topics: Ore dressing , Coal
Commentary by Dr. Valentin Fuster
2017;():V001T04A007. doi:10.1115/POWER-ICOPE2017-3064.

Swirl stabilized premixed flames are common in industrial gas turbines. The flame shape in the combustor is highly related to the combustion stability and the performance of the gas turbine. In the current paper, the effects of confinement on the time averaged flame structures or flame macrostructures are studied experimentally. Experiments are carried out with swirl number S = 0.66 in two cylindrical confinements with diameters of d1 = 39 mm and d2 = 64 mm and confinement ratio c1 = 0.148 and c2 = 0.0567. All the experiments were carried out in atmospheric. CH chemiluminescence from the flame was recorded to visualize the flame behavior. An inverse Abel image reconstruction method was employed to better distinguish the flame macrostructures. Different mechanisms forming the time averaged M shape flames are proposed and analyzed. It is found that the confinement wall plays an important role in determining the flame macrostructures. The flow structures including the inner and outer recirculation zones formed in the confinement are revealed to be the main reasons that affects different flame macrostructures. Meanwhile, the alternation of flame shapes determines the flame stability characteristics. A smaller confinement diameter forced the flame front to bend upstream into the outer recirculation zone hence forming a M shape flame. A strong noise caused by the interaction of the flame front in the outer recirculation zone with the combustor wall was observed. Another unsteady behavior of the flame in the bigger combustor, which was caused by the alternation of the flame root position inside and outside the premixing tube, is also presented. The V shape flame in the two combustors radiated weaker chemiluminescence but the main heat release zone was elongated than the M shape flame. Other operating conditions, i.e. total mass flow rate of the air flow and the equivalence ratio also affect the flame macrostructures. The flame blowout limits were also altered under different test conditions. The bigger confinement has better performance in stabilizing the flame by having lower lean blowout limits.

Topics: Flames
Commentary by Dr. Valentin Fuster
2017;():V001T04A008. doi:10.1115/POWER-ICOPE2017-3078.

Access to electricity is a key necessity in today’s World for economic growth and improvements in quality of life. However, the global challenge is addressing the so-called Energy Trilemma: how to provide secure, affordable electricity while minimizing the impact of power generation on the environment. The rapid growth in power generation from intermittent renewable sources, such as wind and photovoltaics, to address the environmental aspect has created additional challenges to meet the security of supply and affordable electricity aspects of this trilemma. Fossil fuels play a major role in supporting intermittent renewable power generation, rapidly providing the security of supply needed and ensuring grid stability.

Globally diesel or other fuel oils are frequently used as the primary fuel or back-up fuel for fossil-fueled power generation plants at all scales, from a few kiloWatts to hundreds of MegaWatts, and helps provide millions of people with secure electricity supplies. But diesel is a high polluting fuel, emitting high levels of carbon dioxide (CO2) per unit of fuel input compared to natural gas, as well as high levels of combustion contaminants that are potentially hazardous to the local environment and human health. Additionally, diesel can be a high cost fuel in many countries, with imports consuming significant portions of sometimes scarce foreign currency reserves.

Most observers consider that natural gas is the ‘fuel of choice’ for fossil power generation due to its reduced CO2 emissions compared to coal and diesel. However, access to gas supplies cannot be guaranteed even with the increased availability of Liquefied Natural Gas (LNG) and Compressed Natural Gas (CNG). Additionally where natural gas is available, operators may opt for an interruptible gas supply contract which offers a lower tariff than a firm gas supply contract, therefore there is a need for a back-up fuel to ensure continuous power supplies. While traditionally diesel or Heavy Fuel Oil (HFO) has been used as fuel where gas is not available or as a back-up fuel, propane offers a cleaner and potentially lower cost alternative. This paper compares the potential economic, operational and environmental benefits of using propane as a fuel for gas turbine-based power plants or cogeneration plants.

Commentary by Dr. Valentin Fuster
2017;():V001T04A009. doi:10.1115/POWER-ICOPE2017-3090.

Effects of the bluff-body’s position on diffusion flame structures and flame instability characteristics were investigated experimentally. A flame regime diagram together with the corresponding flow fields were proposed to evaluate the influences caused by the alternation of bluff-body’s position. The disk shape bluff-body was placed 10 mm downstream or at the same height with the annular channel exit. The bulk velocity of the annular air flow varied from 0 to 8.6m/s while the central jet fuel velocity ranged from 0 to 30m/s. Various flame patterns including the recirculation zone flame, the stable diffusion jet flame, split-flashing flame and lifted flame were observed and recorded with a high speed camera. It is found that the flame has approximately the same patterns with different bluff-body’s positions, except for cases with high air flow rate (Ua > 6.8m/s) and low fuel flow rate (Uj < 5m/s). Under that operating conditions, placing the disk bluff-body 10 mm above the annular channel could better stabilize the flame. High speed Particle Image Velocimetry (PIV) was also used to get deeper insight into the characteristics of the flow fields and flame stabilization. The size and strength of the recirculation zone downstream of the bluff-body altered with the changing of bluff-body’s position and other operating conditions. The recirculation zone, in the burner with the bluff-body placed 10 mm above the air channel exit, was found larger and stronger than that in the other burner geometry. In the reacting case, a recirculation bubble was formed besides the bluff-body’s outer wall which enhanced the flame stabilization. It is also found that the combustion changed the flow fields by enlarging the recirculation bubbles downstream of the bluff-body.

Commentary by Dr. Valentin Fuster
2017;():V001T04A010. doi:10.1115/POWER-ICOPE2017-3107.

We reported the large-eddy simulations of a series of bluff-body flames varying air-fuel velocity ratio. The air-fuel ratio γ is defined by the ratio of external air velocity to central jet velocity, ranging from 0.05 to 0.50. The case of γ = 0.32 is exactly same the Sydney bluff-body HM1e flame. Firstly, the mathematical model and numerical method were validated in details as the simulation results are all in good agreement with measurements in HM1e flame. Then the interaction between turbulence and thermo-chemistry is revealed. As γ increases, external coflow trends to dominant the flame behavior. The stoichiometric mixture fraction shifts from the area between recirculation zone and central jet to the area between external flow and recirculation zone. Corresponding, the flame changes from jet-like, columnar to hat-like flames. The different level of local extinction and reignition is also observed. Local extinction and reignition occurs in jet-like and columnar flames. As γ increases, local extinction becomes easier and reignition becomes harder.

Topics: Fuels , Turbulence , Flames
Commentary by Dr. Valentin Fuster
2017;():V001T04A011. doi:10.1115/POWER-ICOPE2017-3110.

For the optimal design of the selective non-catalytic reduction (SNCR) for a 600MW W-flame boiler, the SNCR process was simulated through method of chemical kinetics analysis and fluid dynamics analysis. The design temperature, de-nitrification efficiency in theory, position of spray gun and other parameters were determined and 46% de-nitrification rate was finally obtained. Chemical kinetics analysis, without considering the effect of reducing agent mixed with NOx, the theoretical efficiency is higher. Fluid dynamics analysis, taking into account the effect of mass transfer, the de-nitrification efficiency is lower than the theoretical value. In practical engineering, the mixed mass transfer is an important factor affecting the efficiency of SNCR. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T04A012. doi:10.1115/POWER-ICOPE2017-3118.

A 600MW tangentially fired sub-critical boiler with the volume heat load of 87.6kW/m3 at the case of BMCR was not originally equipped with the separated over fire air (SOFA) system. Shenhua bituminous coal with low ash fusion point and strong slagging characteristics is employed as its design coal. To prevent serious slagging on its platen heaters, it is necessary to employ 80% Shenhua bituminous coal with low ash fusion temperature blending 20% Shenhua bituminous coal with high ash fusion temperature. However, NOx emission value at the furnace exit reaches more than 370mg/m3 (O2 = 6%). In order to achieve a NOx emission limitation level below 100mg/m3 (O2 = 6%) for pulverized coal power boilers which meets the requirement from latest Chinese environmental protection regulation, while considering a low cost of retrofit, a comprehensive low NOx emission boiler retrofit scheme combining air-staged low NOx combustion technology and selective catalytic reduction of flue gas in the low temperature flue duct of boiler was selected preferentially. Two-level air staging technology has some obvious advantages including a little negative effect on the boiler’s combustion efficiency, and easily achieving deep air-staged combustion mode. Therefore, a study of numerical simulation concerning original combustion mode and optimized two-level air staging combustion mode was conducted. Due to excellent ignition and burnout characteristics of Shenhua bituminous coal with high volatile matter, low ash fusion temperature and reasonable configuration of upper and lower burnout air ports, the NOx emission level at the exit of furnace would be greatly reduced, and the fouling layer temperature of water wall obviously decreases, which means a definite improvement of clean degree of furnace. And the gas temperature at the bottom of platen heaters decreases about 20 °C while burning 100% Shenhua bituminous coal with low ash fusion temperature. However, its combustion efficiency would decline weakly. The performance of boiler was optimized by combustion tests after the retrofit. This boiler can fully burn Shenhua bituminous coal with low ash fusion temperature by use of two-level air staging system, and furnace soot blowing frequency also lowered. Consequently, exhaust gas temperature decreased, which achieved an increase of boiler efficiency by about 0.3%. In addition, NOx emission level decreased more than 60%, and was about 15 mg/m3 (O2 = 6%) lower than coal blending cases. To meet a full burning of Shenhua bituminous coal with low ash fusion temperature, it is suggested that two-level air staging technology should be applied to the retrofit of boiler. And then goals of low NOx emission and anti-slagging on the platen heaters can be achieved.

Commentary by Dr. Valentin Fuster
2017;():V001T04A013. doi:10.1115/POWER-ICOPE2017-3127.

Five biomass including cotton stalk (CS), sunflower stalk (SS), wheat stalk (WS), rice husk (RH) and maize stalk (MS) were pyrolyzed in an entrained flow reactor under reburning condition. The chlorine release fraction was determined based on the analysis of each biomass and the relevant bio-coke measured by digital ion meter. The effects of biomass species, reaction temperature (T), residence time (τ), stoichiometric ratio (SR2), and initial oxygen content in the simulated flue gas on chlorine release were analyzed. The obtained results indicated that the chlorine release fraction increases with the increasing of reaction temperature, and all biomass have a higher chlorine release fraction of 94.6%–100% at high reaction temperature. Stoichiometric ratio has little influence on chlorine release. The chlorine release fraction shows a significant increase from 80.3% to 97.1% with increasing initial oxygen content in the simulated flue gas from 0% to 4%.

Commentary by Dr. Valentin Fuster
2017;():V001T04A014. doi:10.1115/POWER-ICOPE2017-3144.

The sodium content in Zhundong coal is extremely high, which can accelerate the deactivation of the V-W-TiO2 selective catalytic reduction (SCR) catalysts. Sulfuric acid solution (H2SO4) washing has been verified as a famous method to regenerate the de-NOx performance for catalyst which has been poisoned by alkali metals. However, the performance of the regenerated catalyst in practice still needs to be investigated. In the present study, the resistance to sulfur dioxide (SO2) and the mechanical strength of the regenerated catalyst were experimentally studied as well as the continuous operation performances under several conditions. The results indicate that the de-NOx activity of H2SO4 regenerated catalyst is chemically stable below 300 °C and thermally stable below 450 °C. However, the catalytic activity of the regenerated catalyst could suffer a decline during operating under the SCR atmosphere at 450 °C, which is different from the fresh catalyst. Besides, the regenerated catalyst shows good SO2 resistance, whereas the mechanical strength is likely to be affected by the H2SO4 washing treatment.

Commentary by Dr. Valentin Fuster
2017;():V001T04A015. doi:10.1115/POWER-ICOPE2017-3148.

An comparison of technical specification and updated operation results between two USC coal fired boilers namely RDK-8, Germany and WGQ-3, China has been considered under the global scenario related to the variation of industrial production structure, power demand cut down, more stringent carbon dioxide depression and larger quantity of renewable units engaged into the grid, in this respect a discussion and analysis have been carried out subjected to low grade heat recovering and harmful emission prevention from boiler flue gas and introduction carbon harmful emission prevention from boiler flue gas and their multiple benefits on energy saving and environmental protection, moreover the experience and gains in the field of flue gas heat recovering and mitigating pollution, including the proprietary technique (WGGH) by SPERI are briefly stated, thereby a conclusion of enlightenment for further development of these units is mentioned.

Topics: Coal
Commentary by Dr. Valentin Fuster
2017;():V001T04A016. doi:10.1115/POWER-ICOPE2017-3149.

This study developed a new kind of biomass fuel with biomass (forestry residues, agriculture waste, energy crops and so on) crushed below certain particle size (micron level, ≤250 μm) to form biomass powder, biomass-micron-fuel (BMF). And effects of excess air coefficient, air-fuel ratio, and particle size of BMF on the combustion temperature were studied through a self-designed lab-scale cyclone combustion system. Results showed that temperature increased first and then decreased with the increasing air flow rate and best excess air coefficient occurred in the region of 1.05–1.18. Similarly, combustion temperature also increased first and then decreased as the fuel feed rate increased and 225 g/m3–265 g/m3 air-fuel ratio would guarantee the effective combustion of BMF. The influence of particle size on the combustion temperature was also determined under five different combustion conditions and results demonstrated that the smaller the particle size is, the higher the temperature will be. (CSPE)

Topics: Combustion , Fuels , Biomass
Commentary by Dr. Valentin Fuster
2017;():V001T04A017. doi:10.1115/POWER-ICOPE2017-3195.

The aim of this paper is to investigate the thermal conductivity of various biomass products and investigate the thermal conductivity when moisture is added. In this study, the biomass used was seeds from Bermuda grass and a mix of wildflowers (e.g. Lupine, flax, Coreopsis and Shasta daisy).

Thermal diffusivity is calculated with a transient, one-dimensional conduction experiment. The experiments on aluminum is performed to test the experimental test setup to ensure the accuracy of the technique. Before obtaining the biomass thermal conductivity tests, the actual thermal conductivity values are obtained with the C-Therm TCi Thermal Conductivity Analyzer and the tests are carried out and compared with these values. Next, moisture is infused into biomass samples by addition of water from 10% to 30% with increments of 5%. An increase in thermal conductivity with moisture is observed for both biomass samples and the results are presented. In our tests, the moisture increased the thermal conductivity about 78% for Bermuda grass seed and 122% for Wild Flower seed.

Commentary by Dr. Valentin Fuster
2017;():V001T04A018. doi:10.1115/POWER-ICOPE2017-3211.

A turbocharged three cylinder automotive common rail diesel engine was modified to operate in the n-butanol diesel dual fuel mode. The quantity of butanol injected by the port fuel injectors and the rail pressure, injection timing and number of injection pulses of diesel were varied using open engine controllers. Experiments were performed in the dual fuel mode at a constant speed of 1800 rpm at varying BMEPs. Butanol to diesel energy share (BDES) was varied and the injection timing of diesel was always set for highest brake thermal efficiency (BTE). Single pulse injection (SPI) and two pulse injection (TPI) of diesel were evaluated. In SPI with increase in butanol diesel energy share (BDES), BTE remained unchanged. At high loads and high BDES the heat release rate variation indicated that butanol auto ignited before diesel with both SPI and TPI of diesel. NO emission always decreased because of reduced temperatures due to evaporation of butanol. Butanol also reduced the smoke levels except at high loads. HC levels were always higher. With optimized injection parameters TPI of diesel resulted in lower NO, similar smoke and BTE with lesser rate of pressure rise as compared to SPI of diesel.

Topics: Fuels , Engines , Diesel
Commentary by Dr. Valentin Fuster
2017;():V001T04A019. doi:10.1115/POWER-ICOPE2017-3215.

Chlorine is a harmful constituent in coal, contributing to severe high temperature corrosion on the super-heater and re-heater tubes in utility boiler firing high-chlorine coal (more than 0.3 wt.%). Characteristics of the corrosion contain not only the formed products on the metal surface, but also intergranular attack inner the alloy, resulting in great potential safety hazard and economic loss. The prevailing Cl-related mechanisms of high temperature corrosion involve active oxidation and fluxing, which mean both corrosive elements in the flue gas and deposits on the boiler metal surface can accelerate the corrosion. Cl2 as a catalyst in active oxidation can be released by sulfuration of alkali metal chlorides or reactivity by alkali metal chlorides with chromium/chromium oxide and iron/iron oxide or oxidation of HCl. However, the formation of low-melting eutectics (such as NaCl-Na2CrO4) in mechanism of fluxing can be an induction of severe corrosion because the rate of molten corrosion is much higher than chemical corrosion. Lab-scale experiments simulating the flue gas species, temperature gradient from hot flue gas (950 °C) to cold metal (610 °C), and deposit (four various Cl-containing coal ash) on the specimens were conducted in a tube furnace to investigate the corrosion of three common boiler steels (12Cr1MoVG, T91, TP347H). Furthermore, with the aid of the scanning electronic microscope associated with energy dispersive spectrometer (SEM-EDX) and X-ray diffraction instrument (XRD), the appearance and microstructure, the element contents, and composition of corrosion products on the specimens after corrosion have been analyzed. For high-chlorine coal, there existed white crystal on the surface of specimens (T91, TP347H) after corrosion test, and the XRD result showed NaCl, which can be explained by evaporation-condensation mechanism. However, no white crystal was detected for 12Cr1MoVG and it can be inferred that thick corrosion product layer with high thermal resistance was formed and 12Cr1MoVG suffered severe degradation. Through comparisons of alloy elements corroded in various oxidizers (Cl2, O2, and S), it can be seen that as the metal temperature increases, the negative value of Gibbs free energy for alloy elements corroded in Cl2 becomes higher, but the value is less corroded in O2 or S. Thus, alloy elements tend to be easier combined with Cl2, and Cl-induced corrosion is aggravated with the temperature increases. Similar results can be obtained by increased equilibrium vapor pressures of metal chlorides, evaporating easily and diffusing towards further to be oxidation. In comparison with high-chlorine coal, the corrosivity of low-chlorine coals on specimens were weak, especially for TP347H characterized with higher contents of Cr and Ni. Furthermore, the higher the ratio of Cl/2S or Cl/Na in the coal ash is, the more severe corrosion the specimens suffer.

Commentary by Dr. Valentin Fuster
2017;():V001T04A020. doi:10.1115/POWER-ICOPE2017-3221.

Two typical pulverized Zhundong coal with different calcium oxide contents in ash were selected to use in this work. The liquid nitrogen was used to cool ash rapidly at different temperatures, in order to avoid changes in mineral condition. The ash melting behavior and mineral transition mechanism, especially calcium-bearing minerals was studied by ash melting point test platform, XRD, XRF, SEM and EDS. The results showed that the different states of calcium are the dominant reasons for different sintering behaviors of coal ash. The calcium-bearing minerals in ash, such as calcium oxide (CaO), calcium silicate (CaSiO3), gehlenite (2CaO·Al2O3·SiO2), and anorthite (CaO·Al2O3·2SiO2), etc., are the most important factors influencing the initial sintering behavior of coal ash in the temperature range from 1373K to 1473K under oxidizing atmosphere during coal combustion. That is the reason why ash starts to melt at relatively high temperature during ash melting behavior in laboratory, but has severe slagging and contamination characteristic at low temperature during coal combustion in boilers. The research achievments have important guiding significance for the design of partially or completely burning Zhundong coal boiler as well as its long-term safe and efficient operation. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T04A021. doi:10.1115/POWER-ICOPE2017-3236.

This paper reports the results of a study to determine a ternary blend of oxygenated additives for reduction in smoke emissions in diesel engines. Initial studies on binary blends established twenty percent (by volume) n-butanol-diesel blend (B20) as the base fuel. Subsequently observations were taken with Nitromethane (NM)-n-butanol-diesel blends. It was observed that binary blends are not able to reduce smoke and other emissions beyond the optimum blending ratio (B20). Also, Cetane Number of binary blends was found to be lowered due to poor Cetane Number of n-butanol. It is therefore necessary to add another additive which helps in reducing smoke substantially and improve Cetane Number of blend without affecting the other parameters. The study found that blending of one percent of NM by volume gives best results for smoke reduction. The overall effect of this ternary blend is to reduce the smoke and NOx up to 69.76% and 5.4% respectively. It is concluded that NM-n-butanol-diesel blend would be a potential fuel for smoke reduction in diesel engines.

Commentary by Dr. Valentin Fuster
2017;():V001T04A022. doi:10.1115/POWER-ICOPE2017-3241.

Facing the challenge of needs of abundant, cheap and environmental-friendly supply of electricity, the parameters of utility boiler like the ultra-supercritical boilers should be improved to increase the efficiency of power generation, which may seriously influence the safety of thermal power station reduce the useful life of the boiler materials. With the increasing parameters of steam temperature, high temperature corrosion affected by many factors like temperature, corrosive gas and molten salt of water wall or super-heater near the combustion gas might be more and more serious. In additional with the increasing of the parameters of steam, the stress was induced by the nonuniform temperature distribution in the steel. Thus, the external stress in the steel, which plays an important role in the corrosion process, has been outstanding as the temperature increasing. Therefore, the external stress in the steel has been taken in account in the process of hot corrosion happening in the boilers. The hot corrosion behavior of steel T91 was experimentally studied under different stress in complex environment including high temperature and SO2 corrosive atmosphere. Through observing the corrosion products, morphology and compositional changes in corrosion scales formed in the 168h corrosion process through the XRD, SEM and EDS test, it could be informed that the corrosion behavior was strongly associated with the content of chromium oxides in the corrosion scales. Thus under the experimental environment, the oxides scales were mainly made of two layers in which the outer were formed of Fe oxides and the inner one contained Cr oxides and less Fe oxides. Generally, the Cr2O3 or Ni oxides has the most strong corrosion resistance among Cr, Fe, Mn, Ni, so the portion of Cr2O3 in the corrosion scales strongly affect the hot corrosion. Since the corrosion behavior affected by many factors, the effects of external stress might be different in different temperature for example the 60MPa caused most serious corrosion at 700 °C but at 750 °C that is 40MPa. The external stress could accelerate the diffusion of negative ion like S and Cr elements to cause more serious corrosion.

Topics: Steel , Stress , Corrosion
Commentary by Dr. Valentin Fuster
2017;():V001T04A023. doi:10.1115/POWER-ICOPE2017-3246.

In order to reduce the hotspots in partial oxidation of methane, CeO2 supported BaCoO3 perogvskite-type oxides were synthesized using a sol-gel method and applied in chemical-looping steam methane reforming (CL-SMR). The synthesized BaCoO3-CeO2 was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). XRD and XPS results suggested that the obtained BaCoO3 was pure crystalline perovskite, its crystalline structure and lattice oxygen could regenerate after calcining. The reactivity of perovskite-type oxides in CL-SMR was evaluated using a fixed-bed reactor. Gas production rates and H2/CO ratios showed that the optimal reaction temperature was about 860 °C and the properly reaction time in fuel reactor was about 180s when Weight Hourly Space Velocity (WHSV) was 23.57 h−1. The syngas production in fuel reactor were 265.11 ml/g, hydrogen production in reforming reactor were 82.53 ml/g. (CSPE)

Topics: Syngas , Hydrogen , Methane
Commentary by Dr. Valentin Fuster
2017;():V001T04A024. doi:10.1115/POWER-ICOPE2017-3262.

The Claus reactors is widely used to recover elementary sulfur from hydrogen sulfide that is contained in fresh natural gas. It involves thermal oxidation of hydrogen sulfide and its reaction with sulfur dioxide to form sulfur and water vapor. To improve the efficiency of the process, we built two kinds of 3-dimensional Claus reactor models to explore the key factors that affect the combustion reactions. The two-channel Claus reactor consisted of an air channel and an acid gas channel (60% H2S, 33% CO2, 7%H2O) while the three-channel Claus reactor consisted of two air channels and an acid gas channel (60% H2S, 33% CO2, 7%H2O). The two-channel model was built according to the devices used in the factory while the three-channel model was improved by us from the two-channel model. In both the two models, air and acid gas turned into swirling flow in their channels respectively before their mixture. Then air and acid gas mixed and burned at the throat of the models. The most remarkable difference between the two kinds of Claus reactors was that the three-channel reactor had an additional inner air channel inside the acid gas channel that can be helpful to the mix of the acid gas and air. The second difference was that the two kinds of reactors had different deflectors to swirl in the flow fields. In this study, we compared the flow fields and concentration fields of the two kinds of Claus reactors by using a computational fluid dynamics (CFD) tool.

The simulation results indicated that the swirling intensity and the mix intensity played an important role in the combustion reactions. The efficiency of sulfur recovery in Claus reactors increased with an increase of the swirling intensity or the mix intensity. The stronger the swirling intensity or the mix intensity was, the sooner the mixture of air and acid gas reached to the best stoichiometric ratio. The three-channel reactor had a better performance than that of the two-channel reactor due to the additional inner air channel which can strengthen the mix of the acid gas and air from the inside of the acid gas. Moreover, the helix deflectors in the three-channel reactor had a better swirling performance than that of the vane deflectors in the two-channel reactor. From the comparison of the two models, we can obtain a way to improve the process of elementary sulfur recovery in the industry, which can be helpful to reduce pollution emissions and improve economic performance.

Commentary by Dr. Valentin Fuster
2017;():V001T04A025. doi:10.1115/POWER-ICOPE2017-3274.

Catalytic combustion of ultra-low heat value fuel over 0.5%Pd/ZrO2/γ-Al2O3 was investigated to offer an opportunity for scientifically using such fuel sources. The experimental studies were performed using single fuel, synthetic mixtures and different kinds of gasified biomasses, respectively. The effects of varied combustible gas concentration, inlet temperature and flow velocity on the conversion rate were also studied. The results showed that the ignition temperature of 1.4% CH4 over the catalyst used is lower 210 °C than that in the oxidation absence of catalyst. Conversion of CH4 increased with decreasing flow velocity and increasing combustible gas concentration. The influence of the flow velocity on the conversation is more significant when further increasing the CH4 concentration to a certain degree. The ignition temperature for CO, H2, CH4 decreased with increasing concentration, and the specific order is TCH4, TCO, TH2. The experimental data showed that the influence of H2 is very obvious for CH4 combustion-supporting character by adding different concentration of H2. Among the experiments of three kinds of gasified biomasses, the catalytic combustion characteristics of wood chip gas is best, followed by grape seed gas and cotton wood gas. These studies would provide the experimental analysis and technical support for catalytic combustion technology application in ultra-low heat value fuel.

Commentary by Dr. Valentin Fuster
2017;():V001T04A026. doi:10.1115/POWER-ICOPE2017-3277.

To protect against global warming, a massive influx of renewable energy is expected. Although hydrogen is a renewable media, its storage and transportation in large quantity is difficult. Ammonia, however, is a hydrogen energy carrier and carbon-free fuel, and its storage and transportation technology is already established. Although ammonia combustion was studied in the 1960s in the USA, the development of an ammonia combustion gas turbine had been abandoned because combustion efficiency was unacceptably low. Since that time, in the combustion field, ammonia has been thought of as a fuel N additive in the study of NOx formation. Recent demand for hydrogen carrier revives the usage of ammonia combustion, but no one has attempted an actual design setup for ammonia combustion gas turbine power generation. The National Institute of Advanced Industrial Science and Technology (AIST) in Japan successfully performed ammonia-kerosene co-fired gas turbine power generation in 2014, and ammonia-fired gas turbine power generation in 2015. In the facilities, a regenerator-heated, diffusion-combustion micro-gas turbine is used, and its high combustor inlet temperature enables high thermal efficiency of ammonia combustion compared with that of methane combustion. Adoption of the regenerator increased combustor inlet temperature and enhanced flame stability in ammonia-air combustion. Although NOx emission from a gas turbine combustor is high, a Selective Catalytic Reduction (SCR) after gas turbine combustor reduces NOx emission to less than 10 ppm. This means that the ammonia combustion gas turbine design, abandoned in the 1960s for its unacceptably low combustion efficiency, has performed successfully with regenerator and SCR technology. However, the weakness of these facilities was that they required large-size SCR equipment in order to suppress a high concentration of NOx. Although NOx reduction in the combustion process is desirable, low NOx combustion technology is difficult because ammonia had been thought of as a source of fuel-NO. In the case of premixed ammonia-air flame, there exists a low emission window of NOx and NH3 in a certain equivalence ratio, but combustion intensity is very low because the laminar burning velocity of NH3-air is one-fifth that of CH4-air. This means that, when utilizing the window of premixed ammonia-air flame, scale-up of the combustion chamber or fuel additives for enhancement of flame stability is necessary. This study shows that the addition of H2 is effective for low NOx combustion with high combustion efficiency. In addition, H2 can be easily made from NH3 decomposition. The other option is diffusion combustion. Further research on low NOx combustion is needed.

Commentary by Dr. Valentin Fuster
2017;():V001T04A027. doi:10.1115/POWER-ICOPE2017-3311.

In order to reduce CO2 emission from thermal power stations with keeping high thermal efficiency, a new concept of IGCC system, namely oxy-fuel IGCC, has been recently proposed. Hence CO2 is recycled in the system, the effect of CO2 recycle on each equipments should be clarified. In this study, the effect of recycled CO2 injection on coal gasifier performance was investigated by means of three-dimensional RANS-based numerical simulation. For estimating of coal gasifier performance, coal gasification and water-gas shift reaction are key phenomena. Therefore, the partially active site sharing coal gasification model and detailed chemistry of water-gas shift reaction model were implemented. Calculated gasifier was a commercial scale entrained flow coal gasifier whose coal feeding rate is 70 tons per hour. The gasifier consists of a lower combustor part and an upper reductor part. The effect of coal feeding rate into the reductor, R/T, was investigated. The results show that temperature in the combustor decreases with decreasing R/T. In the lower R/T condition, hence air ratio in the combustor decreases, the reducing atmosphere becomes stronger. As a result, coal gasification which is endothermic reaction in the combustor is promoted. Although coal gasification is occurred in the reductor in higher R/T condition, total coal gasification rate is not so promoted compared with lower R/T condition. Due to the above mechanism, the gasification performance becomes higher with decreasing R/T. The results obtained in this study indicate that it is important that how much the higher gasification reactivity in a gasifier is exploited by optimizing local heat balance.

Commentary by Dr. Valentin Fuster
2017;():V001T04A028. doi:10.1115/POWER-ICOPE2017-3327.

This paper aims at developing a mesoscale combustion based thermoelectric power generator as an alternate to the electrochemical batteries. Most of the micro and mesoscale combustors investigated till date are based on external fuel and air supply systems, which may not be beneficial for a practical system. The proposed design is a standalone system which makes use of the heat conducted through the combustor walls, as an energy source to evaporate the liquid fuel stored in a surrounding tank and supply the vaporized fuel to the combustor. The high momentum fuel (vapor) jet is designed to entrain the ambient air in appropriate proportion so as to form a combustible mixture. The partially mixed fuel/air mixture is fed to a mesoscale combustor and the flame is stabilized by facilitating hot gas recirculation regions. The heat conduction through the combustor walls is controlled by providing an air gap between two concentric, low thermal conductivity, ceramic tubes so as to transmit desirable amount of heat to the fuel tank. Note that the heat lost from the combustor, is recovered via increased enthalpy of the supplied fuel. The hot products then flow over the hot side of a thermoelectric module to generate electricity. The cold side of the module is maintained at relatively lower temperature and the rejected heat is used to boil the stored water. The prototype is designed to produce an electrical power output of 15 W with an overall efficiency of about 3% and endurance of 1 hour in a single fuel (and cold side water) refill. The paper presents detailed thermo-fluid and heat transfer analysis of the constituent components and evaluates the performance of the system.

Commentary by Dr. Valentin Fuster
2017;():V001T04A029. doi:10.1115/POWER-ICOPE2017-3329.

Recently the firing of biomass at existing power plant has drawn much attention because biomass fuels result in less pollutant emission. It is desirable to investigate the flow characteristics of biomass particles in existing combustors in order to determine whether the coal burners also have good adaptability for biomass fuel. The particle dispersion in the burner has a close relationship with pollutant emissions. In this paper, a monitoring system based on a charge-coupled device (abbreviated as CCD) camera was employed to measure the particle distribution of rice husk in a fuel-rich/lean burner. The influence of air velocity was taken into consideration. The particle-rich/lean ratio is 19.49, 16.23, 14.86, and 12.94 (corresponding to the air velocity of 9.5, 11, 12.5, and 14 m/s, respectively) at the exit of the burner model. The results indicates that the air velocity has a negative effect on the separation performance. In order to verify the particle distributions obtained by the digital imaging technique, specially designed filter bags were used to collect rice husk from both the fuel-rich side and fuel-lean side. Then mass and size distributions of the collected particles were analyzed. The results agrees with the trend above and indicates that the block-type concentrator has greater impacts on large particles. More large particles were collected from the fuel-rich side. The dispersion mechanism of rice husk particles revealed in this paper can propose solutions to the actual operation of plants that combust/co-combust the rice husk. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T04A030. doi:10.1115/POWER-ICOPE2017-3331.

We present a new model for the prediction of the explosion limits of the hydrogen-oxygen system. Our model is based on the principle of ignition delay time, postulating that crossing the explosion limit (by increasing the pressure or temperature above it) causes a sharp decrease in the ignition delay time. By using fundamentals of the chain ignition theory, and by employing the Le-Chatelier rule for the explosion limits of fuel mixtures, we develop our model equations. We use numerical analysis to calibrate the constants, and show that our proposed model can accurately capture the unique trend of the peninsula shaped explosion limits. We believe that the relative simplicity of our model will be useful in the analysis of more complex hydrocarbon fuels.

Topics: Explosions , Hydrogen , Oxygen
Commentary by Dr. Valentin Fuster
2017;():V001T04A031. doi:10.1115/POWER-ICOPE2017-3333.

Coal is a valuable primary energy source that has excellent supply stability and economic efficiency. Japan has extremely low energy self-sufficiency and coal-fired power generation is positioned as an important base load power supply. One urgent issue we face is to find realistic countermeasures that greatly reduce CO2 emissions from coal-fired power plants which produce a large volume of CO2 emissions. Therefore, we have launched the Osaki CoolGen Project since April 2012 as an “Integrated Coal Gasification Fuel Cell Combined Cycle (IGFC) Demonstration Project” subsidized by the Ministry of Economy, Trade and Industry (until 2015 FY) and New Energy and Industrial Technology Development Organization (from 2016 FY). This project aims to realize innovative low-carbon coal-fired power generation that combines an IGFC, an extremely efficient coal-fired power generation technology with high-performance CO2 capture technology for the purpose of dramatically reducing CO2 emissions from coal-fired power generation. This project consists of three steps. The first step will implement demonstration tests of the oxygen-blown Integrated coal Gasification Combined Cycle (IGCC) which is the base technology for IGFC.

Toward the start of demonstration testing in March 2017, construction was started in March 2013 and commissioning was started in April 2016. In the second step, we plan to carry out demonstration tests of the oxygen-blown IGCC with CO2 capture equipment. In the third step, we plan to demonstrate an IGFC system combining the demonstration plant of the second step with a fuel cell.

Commentary by Dr. Valentin Fuster
2017;():V001T04A032. doi:10.1115/POWER-ICOPE2017-3337.

A modified sorbent was prepared by a novel hydration-impregnation method. Results indicated that hydrating with salt water can obtain enhanced capacity of the sorbents during multiple calcination/carbonation reactions. After 40 cycles, the modified limestone sorbent doped with 2wt% lake salt remained a CO2 capture capacity of 0.34 g of CO2 of sorbent, which was 150% higher than that of natural limestone. XRF and XRD were tested for analyzing the chemical component of the sorbents. A Fixed-bed reactor was applied to test the absorption characteristics of those sorbents. SEM analysis revealed that macropores in this novel sorbent were relatively stable during long-term cycles. A preliminary economic analysis of different modified calcium-based sorbents was conducted, and the results demonstrated that limestone modified by lake salt is a promising scheme for large-scale sorbent production, which is a well cost-effective and pollution free scenario suitable for industrial promotion. (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T04A033. doi:10.1115/POWER-ICOPE2017-3351.

This paper presents a study of ethanol jet spray flame characteristics in a hot-diluted oxidant with different co-flow oxygen concentrations and fuel/air mass flow rate ratios (MF/MA ratios) through advance image processing technique. An air-blast atomizer was located in a McKenna burner which was utilized to provide stable combustion surroundings and variable combustion atmosphere for ethanol jet spray. The co-flow oxygen concentrations were set to 5%, 10%, 15% and 21% (by volume) by adjusting the mass flow rates of CH4, O2 and N2. The MF/MA ratios were set to 0.245, 0.490, 0.735, and 0.980 by adjusting the fuel mass flow rate and the carrier air mass flow rate. A high-speed RGB CCD camera was employed to capture spray flame images continuously. Spray flame edge is detected using an auto-adaptive edge-detection algorithm which could detect the spray flame edge continuously and clearly. A flame zone is defined as the region surrounded by the detected flame edge to obtain flame parameters. Spray flame characteristics are described using the measured flame parameters, involving flame area, length, brightness, nonuniformity and temperature which are derived from the spray flame images. Spray flame area, length, brightness and nonuniformity are extracted through image processing technique directly. Moreover, two-dimensional (2D) temperature profiling of spray flame is obtained by coupling image processing technique with two-color pyrometry based on Planck’s radiation law. The effects of co-flow oxygen concentration and MF/MA ratio on spray flame characteristics are investigated in this work. The spray flame parameters are observed to be sensitive to both co-flow oxygen concentration and MF/MA ratio. The results show that the fuel mass flow rate (MF) has opposite effects on spray flame characteristics compared with the carrier air mass flow rate (MA) in hot-diluted oxidant. Spray flame area and length are shown to decrease for higher co-flow oxygen concentrations, while spray flame brightness, uniformity and temperature are observed to increase for higher co-flow oxygen concentrations, owing to the enhancement of the combustion rate. A higher MF/MA ratio leads to higher spray flame area, length, brightness, uniformity and temperature, due to the increase of the droplet residence time or droplet concentration in hot-diluted oxidant. In the same MF/MA ratio, spray flame area and length are found to be smaller at a higher fuel flow rate (or carrier air flow rate). However, spray flame brightness, uniformity and temperature are demonstrated to be enhanced at a higher fuel flow rate (or carrier air flow rate). (CSPE)

Commentary by Dr. Valentin Fuster
2017;():V001T04A034. doi:10.1115/POWER-ICOPE2017-3411.

A series of numerical simulations were conducted to study the influences of separated over-fire air (SOFA) distribution, yawing and tilting angles on the flue gas temperature deviation of a 660MW tangentially coal-fired boiler. The turbulent flow, combustion, pollutants and emission characteristics were investigated. The numerical model developed in the study was first validated with field test, which showed good consistence between the numerical and experimental results. Further study indicated that with the increase of SOFA rate, the coal burnout rate, temperature uniformity coefficient and temperature deviation on the temperature detection line (TDL) declined, and the NOx emission dropped. Increase the SOFA yawing angle in reverse tangential direction leads to reduction of high temperature region in the center of lower furnace exit section and in the left of upper furnace exit section, which is positive in reducing gas temperature deviation. Tilting SOFA nozzle upward leads to upward movement of high temperature region in the upper furnace burnout region, increases in gas temperature of upper and lower furnace exits, decreases in temperature distribution uniformity coefficient of furnace exit section and a slight decrease in coal burnout rate, which is negative for reducing gas temperature deviation. (CSPE)

Topics: Temperature , Boilers , Coal
Commentary by Dr. Valentin Fuster
2017;():V001T04A035. doi:10.1115/POWER-ICOPE2017-3420.

In recent years, global warming and climate change caused by the greenhouse gas emissions has given rise to widespread concerns. CO2 has been considered as the principal greenhouse gas of interest, and fossil-fuel-fired power plants have been deemed as the largest stationary sources of CO2 emission. It is imperative to capture CO2 from these sources to reduce the global CO2 emissions. Lately, capturing CO2 from flue gas using solid absorbents shows promising for CO2 abatement. For the cost-effective CO2 capture process and the recycling of environmental pollutants, deprecated resources have been utilized for CO2 capture from flue gas.

In this work, fly ashes derived from different raw materials were tried as solid CO2 sorbents for flue gas treatment. To improve their CO2 capture capacities, the ashes were modified by different polyamines. An experimental demonstration on CO2 capture behaviors of fresh ashes and modified sorbents in simulated flue gas atmosphere of 40°C, 15% CO2 + 15% H2O and balanced N2 was presented in detail with a fixed-bed reactor system. CO2 capture capacities of fresh ashes were calculated as 0.56 mmolCO2/g, 0.32 mmolCO2/g, 0.44 mmolCO2/g and 0.83 mmolCO2/g, respectively. By contrast, CO2 capture capacities of amine-modified samples had been enhanced as 0.38 mmolCO2/g, 0.65 mmolCO2/g, 1.07 mmolCO2/g, 0.85 mmolCO2/g and 1.17 mmolCO2/g. The optimal sample of TEPA-modified biomass ash (TEPA-BA) with CO2 capture capacity of 1.17mmolCO2/g was screened. The optimal candidate was then selected for further investigation of the effects of temperature, CO2 concentration and H2O concentration on its CO2 capture behaviors. The results indicated that CO2 capture capacity would increase with the increase of temperature in the range of 30 to 40 °C and decrease with the increase of temperature in the range of 40 to 60°C, increase with the increase of CO2 concentration in the range of 5% to 20%, increase with the increase of H2O concentration in the range of 0% to 15% and decrease with the increase of H2O concentration in the range of 15% to 20%. The results in this work could provide basic data as a guidance for further applying the sorbents in practical operations.

Commentary by Dr. Valentin Fuster
2017;():V001T04A036. doi:10.1115/POWER-ICOPE2017-3439.

Diesel engines are widely used throughout the world in the transportation and industrial sector. Over the years, engineers and researchers have made continuous efforts to maximize the efficiency of the diesel engine, but there is still room for improvement. By maximizing the efficiency we can not only reduce the fuel consumption of engine, but can also add positively to the environment by reducing the emissions from the engine.

In the present research a simulation model for the optimization of the performance of a diesel engine’s has been developed using the cylinder to cylinder approach. Physical, empirical and thermodynamic relations are used to setup the model in MATLAB. The model can predict the backflow through the valves based upon pressure difference across the valves. Multi event fuel injection technique is employed using main injection and pilot injection. The turbocharger is investigated with and without intercooler to see the effect on engine performance. The simulated results are in good agreement with already presented experimental results.

A study has been performed to analyze the effect of variation of different parameters on the efficiency of the compression ignition engine. The parameters analyzed are bore to stroke ratio, compression ratio, equivalence ratio, injection timing variation (advance, retard), inlet charge heating and turbo-charging. By using the developed technique it is easier to make decisions regarding efficiency optimization in the design phase of the engine. The testing time and cost associated with the engine can also be reduced. The study provides a thorough insight on the effect of parametric variation on engine efficiency.

Commentary by Dr. Valentin Fuster
2017;():V001T04A037. doi:10.1115/POWER-ICOPE2017-3443.

Due to the global warming, climate treaty regulations and credits have been enhanced. As a result, the Carbon Capture & Storage (CCS) technologies have been emerged. In this study, it is presented that is separating the CO2 from Air by vortex generator. The vortex tube is a device to separate inlet gases to hotter and colder mixture than inlet by energy separation technology. In this study, the vortex tube is applied to CO2 gas separation from air that is investigated under atmospheric temperature. Prior to feasibility experiment, transient response shows that the temperature separation is settled down in 3000 seconds. Experimental parameters of gas separation are pressures and concentrations of CO2 that is mixed with air. Results show that CO2 gas separation is proportional to operating temperature. The percentage of CO2 gas separation is 7.4 % at 3barg and cold mass fraction of 0.6. The gas separation is also affected by inlet CO2 concentration.

Commentary by Dr. Valentin Fuster
2017;():V001T04A038. doi:10.1115/POWER-ICOPE2017-3446.

The combustion duration in an internal combustion engine is the period bounded by the engine crank angles known as the start of combustion (SOC) and end of combustion (EOC), respectively. This period is essential in analysis of combustion for the such as the production of exhaust emissions. For compression-ignition engines, such as diesel engines, several approaches were developed in order to approximate the crank angle for the start of combustion. These approaches utilized the curves of measured in-cylinder pressures and determining by inspection the crank angle where the slope is steep following a minimum value, indicating that combustion has begun. These pressure data may also be utilized together with the corresponding cylinder volumes to generate the apparent heat release rate (AHRR), which shows the trend of heat transfer of the gases enclosed in the engine cylinder. The start of combustion is then determined at the point where the value of the AHRR is minimum and followed by a rapid increase in value, whereas the EOC is at the crank angle where the AHRR attains a flat slope prior to the exhaust stroke of the engine. To verify the location of the SOC, injection line pressures and fuel injection timing are also used. This method was applied in an engine test bench using a four-cylinder common-rail direct injection diesel engine with a pressure transducer installed in the first cylinder. Injector line pressures and fuel injector voltage signals per engine cycle were also recorded and plotted. By analyzing the trends of this curves in line with the generated AHRR curves, the SOC may be readily determined.

Commentary by Dr. Valentin Fuster
2017;():V001T04A039. doi:10.1115/POWER-ICOPE2017-3459.

Effect of transient variation in the fraction of components in the multi-component fuels on the characteristics of a Bunsen-type burner has been investigated experimentally. Methane/ethane/propane three-component fuel, methane/ethane two-component fuel and methane/propane two-component fuel were used. The flame motion under the linear transition from one fuel mixture to another was examined. The transition time was varied from 1 s to 10 s, keeping the flow velocity and the equivalence ratio constant at 0.8 m/s and 0.85 respectively. The variation in the flame height was measured, using high speed video camera at 125 fps. Experimental results showed the overshoot of the flame height in an upward or downward direction during the transition. The magnitude of the overshoot was larger for shorter transition time and for larger difference of volume fraction of fuel components. The difference in diffusion coefficient of each fuel is supposed to play an important role for the overshoot.

Topics: Fuels , Flames
Commentary by Dr. Valentin Fuster
2017;():V001T04A040. doi:10.1115/POWER-ICOPE2017-3476.

Currently, SCR-DeNOx technology of flue gas has been widely applied in coal-fired power plants in China for its higher denitrification efficiency, lower ammonia escape and more stable operation performance. In order to overcome the shortages of the off-line method, an on-line method based activating was proposed. However, many key technologies also need to be researched that one of them is a cheap and efficient activating solution. First, activating solutions were prepared by means of single factor and experimental investigations of catalysts activation were conducted. Second, impacts of the catalysts, which were activated by the above mentioned solutions, NO removal and activity were tested and compared with that of the inactivated catalyst. The effect of active components (vanadium, tungsten, molybdenum, oxalic acid) and flue gas conditions on the activation of catalyst were investigated. Then, analysis of these catalysts by scanning electron microscopy (SEM), the specific surface area (BET), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) were conducted. Finally, an ideal activating solution was found out through the analysis of the efficiency of denitrification and the macro and micro changes from catalysts.

The following conclusions were obtained through the above mentioned activation experiments: 1) NO removal by activated catalysts is higher than that of inactivated catalyst; the De-NOx efficiency can be up to 99% in the following conditions: the reaction temperature (370 °C), the proportion of the active solution component (1.0%-V, 9%-W, 6%-Mo), the oxygen concentration (4%-O2) and the ratio of ammonia and nitrogen (NH3:N2 = 1:1); 2) the airspeed and the initial concentration of NO had little influence on catalyst activation; 3) the specific surface area and pore size of the activated catalyst were significantly increased that the active components of the catalyst surface were effectively added. Our investigation results to illustrate that the enhancement of active components, broadening of acid sites distribution, and including the surface labile oxygen and small pores opening to be the reason for high denitrification efficiency.

Topics: Catalysts
Commentary by Dr. Valentin Fuster
2017;():V001T04A041. doi:10.1115/POWER-ICOPE2017-3495.

This paper is aimed to clarify the ash deposition/slagging behavior of blended coal with Xinjiang High-Alkali coal (HA coal) during the combustion process in boiler. One typical Xinjiang coal (HA coal) and another low-alkali coal (LA coal) have been mixed to study the ash melting behavior as a function of coal blending ratio, through the use of AFTs test, XRD, SEM-EDX characterization of ash samples and 3MW pilot-scale test. The results indicate that, the trend of AFTs is not linearly related to the blending ratio of coal mixtures. Instead, it is highly linked with the changes on the liquidus temperature from the ternary phase diagram systems. The initial melting temperature of HA coal ash is approximately 275°C lower than that of LA coal ash due to the existence of alkali and alkaline earth metals, although it has relative higher ash fusion temperature. The mixing of LA coal is not only beneficial to reduce the amount of vaporized sodium, but it also increases the initial melting temperature of blended ash due to the physical and chemical reactions between alkali and silica particles. The higher content of Na gas was formed during HA coal combustion process due to the promoted effect of the existence of Cl in HA coal. Some low melting minerals, such as Na2SO4, Na3Fe(SO4), NaS2O7, were found as the dominate minerals in its deposit ash on heat transfer tubes in the temperature range 650∼1000°C when combustion HA coal. When blended with other LA coal, the amount of deposit ash was decreased and the shape of it became looser due to some high melting minerals were found in its deposit ash, such as quartz and mullite etc. The optimum blending ratio of LA coal is 20% for its safe operation for HA coal.

Topics: Melting , Coal
Commentary by Dr. Valentin Fuster
2017;():V001T04A042. doi:10.1115/POWER-ICOPE2017-3496.

Due to the danger of depletion of world petroleum reserve and environmental concerns the “Philippines Biofuels Act of 2006” (Republic Act No. 9367) was established to develop and strengthen the use of local sustainable fuels, particularly the use of Coconut Methyl Ester (CME) biodiesel blends in the country. As of 2015, with respect to biodiesel in the Philippines only 2% of biodiesel is required to be blended in commercially available fuels. The National Biofuels Board of the Philippines is planning to increase the percentage of the blend within the next 5 years however only few studies are conducted to prove the effectiveness of the increase in percentage. Also in pursuant to “Philippine Clean Air Act of 2009” (Republic Act No.8749) The Department of Environmental and Natural Resources (DENR) issued an administrative order with regards to the implementation of EURO 4/IV Emission Limits within the country. This study investigates the influence of various CME Biodiesel blends in a light duty automotive CRDi engine without any engine modifications through evaluation of performance and emission characteristics, The emission characteristics will be also be investigated if it meets the EURO 4/IV emission limits set by DENR. Five fuel blends B2 (2% CME, 98% Neat Diesel), B5 (5% CME, 95% Neat Diesel), B10 (10% CME, 90% Neat Diesel), B15 (15% CME, 85% Neat Diesel) and B20 (20% CME, 80% Neat Diesel) were used and their results is compared to B0 (Neat). This will also The tests were performed at the University of the Philippines Vehicle Research and Testing Laboratory at steady state conditions, a naturally aspirated water cooled four cylinder Common Rail Direct Injection Diesel (CRDi) engine, with varying speeds from 800 to 4000 RPM at an interval of 400 RPM while maintaining the throttle 100% wide open. As a result of the investigation at typical engine speed range (1200–2400 RPM) no significant differences for biodiesel blends vs. neat diesel were observed for torque, power, CO2 and NOx emissions. However, a decrease of HC and CO was observed. Meanwhile, at 2800–4000 RPM, an increase in torque, power, CO2 and NOx, but no significant differences in HC and CO emissions. However, the engine does not normally run at the higher speed range (1800–2400 RPM) for a long period of time. With respect to biodiesel blends, torque, power, CO2, and NOx emissions generally increase with increasing biodiesel blend, while CO and HC emissions generally decreased with increasing biodiesel blend.

Commentary by Dr. Valentin Fuster
2017;():V001T04A043. doi:10.1115/POWER-ICOPE2017-3498.

The depletion of conventional fuel source at a fast rate and increasing environmental pollution have motivated extensive research in combustion modeling and energy efficient engine design. In the present work, a computer simulation incorporating progressive combustion model using thermodynamic equations has been carried out using MATLAB to evaluate the performance of a diesel engine. Simulations at constant speed and variable load have been carried out for the experimental engine available in the laboratory. For simulation, speed and Air/Fuel ratios, which are measured during the experiment, have been used as input apart from other geometrical details. A state-of-the-art experimental facility has been developed in-house. The facility comprises of a hundred horsepower water cooled eddy current dynamometer with appropriate electronic controllers. A normal load test has been carried out and the required parameters were measured. A six gas analyzer was used for the measurement of NOx, HC, CO2, O2, CO and SOx. and a smoke meter was used for smoke opacity. The predicted Pressure-Volume (PV) diagram was compared with measurements and found to match closely. It is concluded that the developed simulation software could be used to get quick results for parametric studies.

Commentary by Dr. Valentin Fuster
2017;():V001T04A044. doi:10.1115/POWER-ICOPE2017-3570.

A large number of Xinjiang Zhundong coal was found in China. Its high content of alkali metals can cause serious fouling/slagging problems which may lead to economic losses. It is significant to control the release of alkali metals from Zhundong coal during the combustion. Si-Al additives are used to capture Na released from the Zhundong coal. In this work, a combination of experimental research and quantum chemical calculation was used to study the effect of coal ash on the capture of alkali metal in Zhundong high alkali Coal and the related mineral evolution mechanism during melting processes. The experiments were done with Zhundong coal/coal ash mixtures at 900–1200°C. The behavior mechanism of coal ash capturing alkali metals was analyzed from the perspective of mineral microstructure features by using XRD, ICP and quantum chemical calculation methods. The results show that during the process of combustions, complex chemical reactions occur among minerals after sodium is released from the coal and captured by the coal ash. The coal ash’s ability to capture sodium in Zhundong high alkali coal rises firstly, and then gradually decreases with the rise of temperature. It shows the best capture performance for sodium at 1000∼1100°C. The maximum efficiency of sodium absorption can reach to 50.6%. The coal ash shows a rather high efficiency compared with other additives. Furthermore, metals in Zhundong coal have opposite directions of migration. The Na, K, Al, Ca, and Mg migrated to the coal ash far away from the reaction interface, and the Fe and Mn were moved to the coal from the reaction interface. The original minerals of Zhundong coal mainly include calcium sulfate hydrate, quartz and kaolinite. Investigating the capture mechanism, it indicates that O (26) and O (22) in kaolinite have electrophilic reaction with Na+ and K+ easily, which would promote the rupture of aluminum-oxygen bonds. The O2- of alkali metal or alkaline earth metal oxide would easily have nucleophilic reaction with Si (6) and Si (8) and prompt the rupture of bridging oxygen bonds (Si-O-Si). Kaolinite would be transformed into some other minerals that contains Na+ or K+ which have trend to form eutectics or evaporate into the flue gas easily, the degree of fouling and slagging on heating surface can be reduced based on these two most easily reaction paths.

Topics: Coal , Alkali metals
Commentary by Dr. Valentin Fuster
2017;():V001T04A045. doi:10.1115/POWER-ICOPE2017-3619.

Performance of an experimental diesel engine was investigated when fueled with CTL20 (80% ULSD#2 (ultra-low sulfur diesel) blended with 20% Fischer-Tropsch coal-to-liquid (CTL) fuel. CTL fuel was selected given its potential as an alternative fuel that can supplement the ULSD supply. Combustion and emissions were studied in a common rail, supercharged, single cylinder DI engine with 15% exhaust gas recirculation operated at 1500 RPM and 4.5 bar IMEP in reference to a diesel baseline. The injection pressure was varied from 800–1200 bar while injection timing was tested from 15° to 22° CAD BTDC to optimize combustion. Similar in-cylinder pressures and temperatures were observed for both fuels at the same injection pressure and timing; the maximum heat release and in cylinder pressure and temperatures increased with higher rail pressure. CTL20 had a retarded premixed burn peak by 5 to 8 J/CAD compared to diesel at the same injection pressure and timing. This can be related to a delayed ignition of CTL20 which allowed for higher peak premixed combustion. In-cylinder convection and radiation heat fluxes were stable across injection pressures for both fuels around 1.7 MW/m2 and 0.4 MW/m2, respectively. NOx decreased with CTL20 at higher injection pressure while soot was relatively increased at lower injection pressure. CTL20 decreased BSFC by 3–5% compared to ULSD#2 at 800–1200 bar injection. The mechanical efficiency was maintained around 65% for ULSD#2 as well as for CTL20 during operation at all injection pressures. The study suggests that CTL fuel can be used at 20% as a binary mixture in ULSD#2 while sustaining performance in the experimental engine.

Commentary by Dr. Valentin Fuster
2017;():V001T04A046. doi:10.1115/POWER-ICOPE2017-3621.

Sorption enhanced steam reforming of propane over Ni catalyst using in-situ carbonation of CaO provides both carbon capture, and enhanced H2 content in the product gas, and enhanced carbon conversion efficiency. Choosing propane over methane for sorption enhanced reforming provides easier fuel handling capability and higher throughput of H2 per unit volume of fuel. Such advantages help in building domestic scale hydrogen production source for sustainable energy production. The effect of propane addition on CaO carbonation and poisoning possibilities in reformation integrated with CO2 capture is explored in a packed-bed reactor. The motivation of propane addition is to model petroleum gas to address the feasibility of carbon capture integration with hydrocarbon reforming processes. Initially, different partial pressures of steam and propane will be used to study the kinetic parameters in a fixed bed reactor at different temperatures. The formed kinetic models will be used to compare the integrated CO2 capture results and the thermodynamic results to evaluate the efficiencies of such process. Higher temperatures provide better conversion efficiency, but the equilibrium of CaO carbonation suggests steam reforming enhancement and CO2 capture needs to be below 1073 K in order to avoid the backward reaction of CaCO3 releasing CO2. The balance between endothermic reformation reaction and exothermic water-gas shift and CaO carbonation reactions is the optimizing parameter for improved conversion to high H2 content. Temperatures higher than 873 K provided higher conversion with lower CO2 capture and H2 content while lower than 873 K provided lower methane conversion and higher CO2 capture and H2 content. Increase in steam to carbon ratio increased CH4 conversion and reduced CO content without affecting sorption with no further reduction in CO2 observed for most of the sorption cycle. These results supplement the available data in the literature to provide superior reaction conditions to improve the process efficiency in hydrogen production.

Commentary by Dr. Valentin Fuster
2017;():V001T04A047. doi:10.1115/POWER-ICOPE2017-3788.

Colorless Distributed Combustion (CDC) has been shown to provide unique benefits on ultra-low pollutants emission, enhanced combustion stability, and thermal field uniformity. To achieve CDC conditions, fuel-air mixture must be properly prepared and mixed with hot reactive gases from within the combustor prior to the mixture ignition. The hot reactive gases reduce the oxygen concentration in the mixture while increasing its temperature, resulting in a reaction zone that is distributed across the reactor volume, with lower reaction rate to result in the same fuel consumption. The conditions to achieve distributed combustion were previously studied using methane and other fuels with focus on pollutants emission and thermal field uniformity. In this paper, the impact of distributed combustion on noise reduction and increased stability is investigated. Such reduced noise is critical in mitigating the coupling between flame and heat release perturbations and acoustic signal to enhance the overall flame stability and reduce the propensity of flame instabilities which can cause equipment failure. Nitrogen-carbon dioxide mixture is used to simulate the reactive entrained gases from with the combustor. Increasing the amounts of nitrogen and carbon dioxide reduced the oxygen concentration within the oxidizing mixture, fostering distributed combustion. Upon achieving distributed combustion, the overall flame noise signature decreased from 80 dB to only 63 dB, as the flame transitioned from traditional swirl flame to distributed combustion. The flow noise under these conditions was 54 dB, indicating that distributed combustion has only 9 dB increase over isothermal case as compared to 26 dB for standard swirl flame. In addition, the dominant flame frequency around 490Hz disappeared under distributed combustion. For the traditional swirl flame, both the acoustic signal and heat release fluctuations (detected through CH chemiluminescence) had a peak around 150Hz, indicating coupling between the heat release fluctuations and pressure variation. However, upon transitioning to distributed combustion, this common peak disappeared, outlining the enhanced stability of distributed combustion as there is no feedback between the heat release fluctuations and the recorded acoustic signal.

Commentary by Dr. Valentin Fuster
2017;():V001T04A048. doi:10.1115/POWER-ICOPE2017-3791.

Pyrolysis of hydrogen sulfide, as an alternative treatment method to Claus process, with simultaneous hydrogen production and sulfur recovery is an energy intensive process. The high energy demand of the process remains a hindrance to its application. Production of hydrogen via hydrogen sulfide oxidation at very high equivalence ratios, compared to the high equivalence ratio of 3 employed in Claus reactor, has been studied experimentally. The objective of this approach is to alleviate the energy load requirement of hydrogen production from hydrogen sulfide stream. Since combustion of hydrogen sulfide cannot be sustained at such high equivalence ratios, partial oxidation reaction was examined in a heated quartz tubular reactor that was placed inside an electrical furnace. Oxygen concentration of 1% or 2 % in 10% H2S (called the 10%H2S/O2 mixture) were injected into the reactor with the remaining 90% nitrogen gas. These results were compared to the case of decomposing H2S alone. Experimental data showed that destruction of hydrogen sulfide increased with oxygen injection and that it increased with increase in oxygen concentration. Injection of oxygen at increased concentration consumed hydrogen constituent in hydrogen sulfide to water to result in dramatic decrease in hydrogen production. Formation of sulfur dioxide was absent over the examined temperature range of 1273–1673 K. These results provide the potential of hydrogen production from hydrogen sulfide oxidation, define the favorable operational conditions and outline the potential future developments for treatment of hydrogen sulfide.

Topics: Hydrogen , Oxygen , Pyrolysis
Commentary by Dr. Valentin Fuster
2017;():V001T04A049. doi:10.1115/POWER-ICOPE2017-3798.

This work investigated the effect of oxygen concentrations in the reactor on the partial oxidation of JP8 under the distributed reaction condition. Reforming efficiency as high as 74% was achieved; syngas composition consisted of 20.7 to 22.3% hydrogen and 20.2 to 21.5% carbon monoxide.

Reformate product distribution and quality was found to depend on the reactor oxygen concentrations and, to a lesser extent on flame regime. Previous works operating at similar conditions found that higher reformate quality was associated with the more distributed reactor conditions. An increase in reactor oxygen concentrations fostered a more rapid chemical reaction, which shortened chemical time and length scales. While this resulted in a less distributed reactor, the potential decrease in reformate quality was offset by the increased availability of oxygen. As the reactions were limited by the availability of oxygen, the addition of oxygen enhanced the extent of reforming reactions, to promote increased conversion and reforming efficiency.

Topics: Flames , Oxygen
Commentary by Dr. Valentin Fuster

Heat Exchangers, Condensers, Cooling Systems, and Balance-of-Plant

2017;():V001T05A001. doi:10.1115/POWER-ICOPE2017-3002.

The ability to bypass steam, around the steam turbine and directly into a steam surface condenser, has been a fundamental aspect of the design of base loaded power plants for many years. The increased dependence on natural gas, and the subsequent increase in the number of combined cycle plants, has provided additional challenges for the condenser designer, and also the plant operator, with respect to safely accommodating steam bypass.

However, the steam bypass requirements for modern combined cycle power plants differ significantly from those of traditionally base loaded plants, like fossil and nuclear. Higher cycle frequencies for steam bypass, faster start-ups, as well as increases in bypass steam temperatures and pressures, have all impacted the design criteria for the condenser. Indeed, for modern combined cycle plants, the bypass steam conditions are often higher than normal operation, such that the bypass requirements can very well dictate the overall design of the condenser. This, in turn, has resulted in an increase in the reported instances of operational problems, tube failures, condenser damage and plant shutdowns due to steam bypass related issues.

Recorded issues and reported failures experienced by combined cycle power plants during steam bypass, have been traced to causes such as transient conditions during commissioning, faster start-ups, the poor design and location of steam bypass headers internal to the condenser, over-heating due to curtain spray deficiencies, excessive tube vibration and tube failures. Many of these issues are based on an inherent lack of understanding of the impact of the rigors of steam bypass on condenser internals. Furthermore, operation of steam bypass outside of the generally accepted design parameters often compounds these problems.

This paper consolidates the learning and advances in the design of turbine bypass systems for steam surface condensers from the past 20, or so, years. It includes current design guidelines, as well as safe operational limitations, and general considerations for minimizing potential damage when operating steam bypass on a modern combined cycle power plant.

Included is a Case Study of how an existing fossil power plant that was repowered, along with the existing steam surface condenser that was modified to accept the bypass steam, experienced excessive erosion and damage during the past 10+ years of operation. The condenser was recently reviewed once again, and additional modifications were implemented to take advantage of current improvements in steam bypass design. This drastically reduced further erosion and improved the condenser availability, reliability and longevity; thereby improving the plant efficiency.

Commentary by Dr. Valentin Fuster
2017;():V001T05A002. doi:10.1115/POWER-ICOPE2017-3011.

With ever-increasing ambient temperatures many electric power plants that employ cooling lakes to reject their waste heat into the environment are struggling to maintain reasonable turbine backpressures during the hot summer months when electric load demand is often the greatest. Some consider adding mechanical draft cooling towers (MDCT) to further cool the condenser circulating water (CCW) prior to entering the main condenser, but the additional auxiliary power required to drive MDCT fans often consume the additional generator output resulting from the lower backpressure. Spray ponds offer significant advantages over MDCT including superior simplicity and operability, lower power requirements, and lower capital and maintenance costs. The Oriented Spray Cooling System (OSCS) is an evolutionary spray pond design. Unlike a conventional spray pond in which spray nozzles are arranged in a flat bed and spray upward, blocking the ambient air flow to the spray region as it travels down to the pond below, the OSCS nozzles are mounted on spray trees arranged in a circle and are tilted at an angle oriented towards the center of the circle. As a result, the water droplets drag air into the spray region while the warm air concentrated in the center of the circle rises. Both of these effects work together to increase air flow through the spray region. Increased air flow reduces the local wet-bulb temperature (LWBT) of the air in the spray pattern, promoting heat transfer and more efficient cooling. During the late 1970’s the author developed a purely analytical model to predict the thermal performance of the OSCS which was successfully compared with the OSCS at the Columbia Generating Station (CGS) in the mid 1980’s. This paper describes how the OSCS may be employed to supplement the cooling capacity of an existing cooling lake to reduce the temperature of the CCW prior to entering a power plant, resulting in lower main condenser pressures and more net plant output.

Commentary by Dr. Valentin Fuster
2017;():V001T05A003. doi:10.1115/POWER-ICOPE2017-3080.

The condenser performance benefits afforded by dropwise condensation have long been unattainable in steam cycle power plant condensers due to the unavailability of durable and long lasting wetting inhibiting surface treatments. However, recent work in superhydrophobic coating technology shows promise that durable coatings appropriate for use on condenser tubes in steam cycle power generation systems may soon become a reality. This work presents a nano-scale, vapor phase deposited superhydrophobic coating with improved durability comprised of several layers of rough alumina nano-particles and catalyzed silica with a finishing layer of perfluorinated silane. This coating was applied to solid, hemi-cylindrical test surfaces fabricated from several common condenser tube materials used in power generation system condensers: Titanium, Admiralty brass, Cupronickel, and Sea Cure stainless steel condenser tube materials as well as 304 stainless steel stock. The development evolution of the coating and its effect on condensation behavior on the above materials are presented. Results show that the performance enhancement, measured in rate of heat transfer spikes corresponding to condensate roll-off events, was best for the titanium surface which produced 64% more events than the next most active material when coated using the most durable surface treatment tested in this work.

Commentary by Dr. Valentin Fuster
2017;():V001T05A004. doi:10.1115/POWER-ICOPE2017-3084.

Direct-contact heat exchanger involves the exchange of heat between two immiscible fluids at different temperatures. Considering that there is a linear relationship between the flow patterns of a bubble swarm and heat transfer coefficient, it is inevitably to investigate the evolution of flow patterns for heat transfer enhancement in different mixing systems. However, the dynamical complexity and random variability of multiphase flow have put forward a severe challenge to improve the accuracy and real-time performance of visualized measurement of multiphase flow. The entropy of an image shows its quality objectively. Generally speaking, if the value of image entropy is large enough, then the mixing uniformity is good enough. Hence, in this paper, image entropy is used to assess the mixing uniformity and estimate the homogeneous time in the direct-contact boiling heat transfer process. The evolution of bubbles movement is experimentally tracked using an imaging technique. Variations in time of image entropy values bring new insights to study and compare mixing performance of different direct-contact heat transfer process. The results show the evolutions of bubble patterns in a direct-contact exchanger have been successfully visualized measured.

Commentary by Dr. Valentin Fuster
2017;():V001T05A005. doi:10.1115/POWER-ICOPE2017-3180.

Performance of lignite-fueled power plants can be improved by predrying the lignite and it is influenced by the characteristics of drying heat source. Heat source for lignite predrying in power plants can be high-temperature flue gas, boiler exhaust gas and extraction steam. Nevertheless, balance point among drying safety, lignite drying degree and drying thermal economy cannot be located using single drying heat source. In this study, a lignite-fueled power plant with a two-stage drying system was proposed. The drying system mainly contains two fluidized bed dryers — the first stage dryer and the second stage dryer. Boiler exhaust gas and extraction steam supply the heat, respectively. The proposed power plant can attain higher lignite drying degree than the power plant in which only boiler exhaust was employed. The new power plant also features higher overall efficiency for the same lignite drying degree compared with extraction steam drying power plant..

Topics: Power stations
Commentary by Dr. Valentin Fuster
2017;():V001T05A006. doi:10.1115/POWER-ICOPE2017-3190.

Type 304 austenitic stainless steel is the most common tube material utilized for nuclear feedwater heaters, however, some utilities have experienced problems with Stress Corrosion Cracking (SCC), especially when they utilize brackish cooling water and have experienced condenser tube leaks. This has forced some utilities to explore other options when it comes to high pressure feedwater heaters (HP FWH) tubing materials. AL6XN® is considered a “super” stainless steel that is resistant to (SCC), however, it is not immune (AL6XN is a trademark of ATI Technologies).

Based on the relative inexperience and unknowns related to the use of AL6XN tubing in high pressure, nuclear feedwater heater applications, a detailed mock-up procedure was outlined as part of the replacement heater specification which would allow the evaluation of the tube to tubesheet joining processes. Since AL6XN can still be affected by SCC; steps were taken in order to minimize the imposed stress levels and any potential for the inadvertent inclusion of contaminants during the fabrication steps at the tube mill and at the feedwater heater Manufacturer’s shop. The desire to minimize stresses also applies at the tube to tubesheet joint, therefore, it was desired not to stress the tube more than absolutely necessary in achieving a reliable, leak tight joint. The mock-up details and procedures were therefore generated with these objectives in mind, so as to give consideration for the ability to check different configurations in order to determine the most efficient tube to tubesheet joining process.

Several tubes in the mock-up were subjected to a pull out test in order to quantify the joint strength in the different configurations. The mockup was then sectioned and inspected under a digital microscope to verify intimate contact between the tube and the tubesheet. Once the optimal procedure was identified, four identical HP FWHs were constructed utilizing AL6XN tubing. During heater production, over 30,000 tube ends were expanded, however, two tubes were identified to have failures as part of the tube expansion process.

This paper shall describe the procedures utilized in developing and analyzing the tubesheet mock-up as well the actions taken to identify the root causes of the tube failures.

Topics: Joining , Feedwater
Commentary by Dr. Valentin Fuster
2017;():V001T05A007. doi:10.1115/POWER-ICOPE2017-3231.

This paper established a thermal and air leakage calculation model of quad-sectional rotary air preheater, which considered the axial heat conduction of the matrix and the effect of three kinds of air leakage-radial, axial and circumferential air leakage. Based on control equation of rotary air preheater, thermal calculation model was simplified and solved by numerical finite difference method. Air leakage model was solved by nonlinear equations based on mass and energy equations. With the coupling calculation of two models, temperature and air leakage distribution were given. Compared with a quad-sectional rotary air preheater, the error value was less than 5%. The results showed that air leakage of quad-sectional air preheaters was much less than tri-sectional ones .The temperature distribution of fluids in different air channels were continuous and were quite consistent with matrix. Declining the inlet gas flow along the direction of rotary can reduce the low-temperature area rate.

Topics: Leakage
Commentary by Dr. Valentin Fuster
2017;():V001T05A008. doi:10.1115/POWER-ICOPE2017-3235.

Dry cooling towers are an alternative cooling method when large quantities of water are not available. Examples of the proposed applications are the enhanced geothermal and concentrated solar thermal (CST) power plants in arid or semi-arid areas, like south-western United States, Australia, western Asia, north-western China and the rest of the world. Natural draft dry cooling towers (NDDCTs) have received widespread attention because they do not consume water, have low maintenance requirements and cause small parasitic losses. Unfortunately, the performance of a NDDCT is severely reduced when the ambient air is hot, which is because the NDDCT is driven by buoyancy effect and relies solely on air to cool the working fluid. The present study introduces inlet air pre-cooling using wetted media, which combines dry and wet cooling. The wet cooling system only operates at high ambient temperatures to assist dry cooling. However, wetted-medium cooling introduces extra pressure drop which reduces the air flow passing through the NDDCT and thus impairs the tower heat rejection. To this end, this paper takes into account the trade-off between the wetted-medium cooling and the extra pressure drop. Early studies find that the performance of NDDCTs can be improved by wetted-medium evaporative pre-cooling when the ambient air is hot and dry. However, the pre-cooling enhancement is seasonal-dependent and is significantly affected by wetted media. To further investigate the effect of wetted medium type on pre-cooling performance, the current study simulates a pre-cooled NDDCT using five selected wetted media (i.e., three film and two trickle media) based on a self-developed MATLAB program. The innovations of the current study are: (1) two typical types of wetted media with the potential of evaporative pre-cooling are comparatively studied to give suggestions for future pre-cooling design; (2) the characteristics of wetted media suitable for evaporative pre-cooling of NDDCTs are summarized.

The simulation finds that the media with high or low cooling efficiencies and pressure drops are not promising while those media with middle cooling efficiencies and pressure drops intend to produce much performance enhancement of the studied NDDCT. The film medium, Cellulose7060 with pressure drops of 28.6–272.1 Pa/m and cooling efficiency range of 44.7–88.5% is most promising for such pre-cooling enhancement. For the studied NDDCT, the critical temperatures below which the tower performance does not benefit but is hindered by wetted-medium pre-cooling are 28, 16, 30, 26 and 26°C for cellulose7090, cellulose7060, PVC1200, Trickle125 and Trickle100, respectively (ambient humidity of 20% and medium thickness of 200mm). The pre-cooling enhancements can go up to 100% by 200mm-thick cellulose7060 at extreme hot and dry climate (i.e., ambient temperature of 50°C and humidity of 20%). The simulation will give instructions for the design of pre-cooled NDDCTs.

Topics: Cooling
Commentary by Dr. Valentin Fuster
2017;():V001T05A009. doi:10.1115/POWER-ICOPE2017-3278.

Effect of flow direction of heating medium on the heat transfer performance of upward evaporating refrigerant flows in a plate-fin heat exchanger was examined using HFC-134a as the refrigerant. The heat exchanger had a single refrigerant channel sandwiched by two water channels. Hot water flew upward or downward to form a parallel or counter flow heat exchange, respectively. To understand the heat flux distribution, temperature distributions on the outside wall of the water channel were visualized by an IR camera. As the results, it was shown that the difference in heat transfer rate between the parallel and counter flow was a little due to the large temperature difference in the heat exchange. The pressure loss of the refrigerant flow was larger for the parallel flow than the counter flow. It could be estimated from the wall temperature distribution that the increase in pressure loss might be caused by inhomogeneous phase distribution of the refrigerant flow.

Commentary by Dr. Valentin Fuster
2017;():V001T05A010. doi:10.1115/POWER-ICOPE2017-3289.

There are various finned tube heat exchanges with diverse thermo-flow performance being widely applied in the power plants. Wherein, the H-type finned tubes are widely used in the economizer to improve the waste heat utilization efficiency of the coal fired boiler. The experimental studies regarding the heat transfer and resistance characteristics of single H-type and double H-type finned tubes have obtained the thermo-flow performances under different conditions. In addition, the test facility of double channels is specially designed to ensure the test accuracy. Correlations for Euler number Eu, Nusselt number Nu and Performance evaluation index Pec with Reynolds number Re are presented by analyzing the thermo-flow performances of the used bundles. The results show that the single H-type finned tube performs better heat transfer characteristic and relatively worse resistance characteristic than the double H-type finned tube. Consequently, the double H-type finned tube is recommended in the practical application considering the higher manufacturing installation efficiency. (CSPE)

Topics: Heat transfer
Commentary by Dr. Valentin Fuster
2017;():V001T05A011. doi:10.1115/POWER-ICOPE2017-3293.

Effects of the tube array, such as in-line and staggered, on void-fraction distribution and heat transfer coefficient around a tube were experimentally investigated. The test section was vertical duct with inner size of 90 × 90 mm2. Diameter of the tubes was 15 mm, and the pitch-to-diameter ratio was 1.5 for both tube bundles. Working fluids were air and water. Experiments were carried out at superficial gas velocity defined at minimum area section, Jg, of 0.10 to 0.89 m/s, superficial liquid velocity, Jl, of 0.1 to 0.3 m/s, under the atmospheric condition. Measurements of void-fraction distribution were carried out using X-ray radiography. In addition, heat transfer coefficient around a tube was measured and the heat transfer coefficients in association with the flow regime and the void-fraction distribution were evaluated. Time-average void-fraction was higher around upstream of a tube than that of downstream at bubbly flow condition for both bundles. Under intermittent flow condition, time-average void fraction at the maximum gap were higher than that around the other points in both tube bundles. For in-line tube bundle, enhancement of the heat transfer clearly appeared between ±90 to 180°. For staggered tube bundle, the heat transfer increased all over the pipe.

Commentary by Dr. Valentin Fuster
2017;():V001T05A012. doi:10.1115/POWER-ICOPE2017-3367.

In response to the technical challenges faced by aging plant systems and components at nuclear power plants (NPP), the Electric Power Research Institute (EPRI) has a product entitled Integrated Life Cycle Management (ILCM). The ILCM software is a quantitative tool that supports capital asset and component replacement decision-making at NPPs. ILCM is comprised of models that predict the probability of failure (PoF) over time for various high-value components such as steam generators, turbines, generators, etc. The PoF models allow the user to schedule replacements at the optimum time, thereby reducing unplanned equipment shutdowns and costs. This paper describes a mathematical model that was developed for critical heat exchangers in a power plant. The heat exchanger model calculates the probability of the tubes, shell, or internals failing individually, and then accumulates the failures across the heat exchanger sub-components. The dominant degradation mechanisms addressed by the model include stress corrosion cracking, wear, microbiologically influenced corrosion, flow accelerated corrosion, and particle-induced erosion. The heat exchanger model combines physics-based algorithms and operating experience distributions to predict the cumulative PoF over time. The model is applicable to shell and tube heat exchangers and air-to-water heat exchangers. Many different types of fluids including open cycle fresh water, closed cycle fresh water, sea water, brackish water, air, closed cooling water, steam, oil, primary water, and condensate are included. Examples of PoF over time plots are also provided for different fluid types and operating conditions.

Commentary by Dr. Valentin Fuster
2017;():V001T05A013. doi:10.1115/POWER-ICOPE2017-3398.

Water is essential to the power generation process, and for many power generation plants that rely on cooling water systems to condense steam, total hardness in source water is a problem. The high mineral content in many sources of cooling water results in hardened, calcified scale deposits forming on the walls of condenser tubes. These deposits form an insulation barrier inhibiting heat transfer. The scale also reduces the inner diameter of the tubes, restricting the flow of cooling water and further reducing heat transfer. As the heat transfer rate falls, performance of the condenser degrades, which can lead to decreasing megawatt output of the plant.

A power station in the United States sources hard lakewater for cooling. Like many plants utilizing hard water, the station relies on a water treatment program to control the formation of hard scale deposits. However, when the plant opened a closed cooling water exchanger (CCW) in its Unit 1, a layer of calcium carbonate was found on the tube walls throughout the bundle.

The CCW exchanger was shot with a variety of mechanical cleaners to thoroughly remove the scale and other deposits and debris from the tubes. Plant management suspected that the same problem might be occurring in the main condenser, and they understood that if scale was forming inside the condenser, the resulting loss in heat transfer rate would be a contributing factor in the decreased efficiency of the unit.

Since the plant was planning an eddy current test on 100% of the more than 12,000 stainless steel tubes in the main condenser, the tubes were required to be thoroughly cleaned. Upon opening the main condenser, technicians verified the presence of calcium carbonate fouling, confirming their suspicions. While not knowing the condition of the tubes underneath the deposit, plant engineers were concerned about the underlying tube condition. They were also looking for alternative cleaning methods to provide relief from environmental concerns often associated with chemical cleaning. To preserve tube integrity and assure thorough removal of deposits, the plant decided to clean the condenser tubes utilizing the same mechanical cleaning method as the CCW unit. The condenser tubes would be shot with a series of specialized mechanical tube cleaners, one designed to fracture the calcium carbonate and a second designed to remove the fractured scale and other deposits from the tubes.

This paper highlights the role of hard water in condenser tube fouling, the need to remove scale from condenser tubes and the mechanical cleaning process that was used to restore condenser performance at a prototypical coal fired power station in the United States.

Commentary by Dr. Valentin Fuster
2017;():V001T05A014. doi:10.1115/POWER-ICOPE2017-3466.

The design and certification of a high performance recuperator for micro gas turbines is presented. The component has been developed and built for a 100kWel micro gas turbine. The recuperator heated up compressed air at 3.5 bar with exhaust gas near atmospheric pressure and recuperates 300 kWth at an effectiveness of 90%. This concept can readily be adapted for other micro gas turbines due to its modular design. The certification has been realized under Pressure Equipment Directive 97/23/EC, equivalent to ASME Boiler and Pressure Vessel Code, covering closed pressurized devices. However, minor leakage in the recuperator is allowed, thus requiring an inventive design and validation approach for meeting the certification requirements. This leak is caused by weld porosity: the heat exchanging core plates are laser welded, having over 1200 meters of sealing weld length in a single recuperator. The maximum allowable leak amounts to 3 10−6 mm2 per meter weld length. The maximum leak was 0.2% of the massflow on the pressurized side at the nominal operating point, and therefore did not adversely affect the effectiveness of the recuperator. The finite element calculations and the resulting design loops on components and weld connections are presented. Validation of the entire component is done under the Experimental Design Method. A hydrostatic pressure test at 8.4 bar and ambient temperature is executed in the presence of a certified notified body to demonstrate that the welds are sufficiently robust. This pressure is higher than the operating pressure to simulate the effect of temperature on the steel properties. A laser scanner is used to map the deformation of the unit under pressure and subsequently referenced to its original state. The maximum deviation measured is equal to 0.26 mm for the pressurized part, which is acceptable considering the size of the unit is 1000mm × 600mm × 1000mm. The strain levels went back to the values before putting the unit under pressure, indicating there are no residual deformations.

The test is further accompanied with leakage rate measurements before and after the hydrostatic pressure test. If the difference between these leakages rates is within limits, the recuperator will pass the test. The measured total leakage area is 0.4 mm2, well below the maximum allowable value, and equivalent to 0.01% of the massflow at the nominal operating point. This means the recuperator passed the test successfully. Furthermore, a burst test was executed to determine the safety factor and to identify the weakest element of the design. The burst pressure is observed at 18.3 bar, resulting in a safety margin of 218% and 523% in reference to the PED and operational design pressures, respectively. The component responsible for failure has been further optimized for the next generation of recuperators. Field data confirm that the lifetime of the high performance recuperator meets the requirements of 40.000 h operating time. Additionally, the traceability of the serial produced components is handled by the audited quality management system. It covers the used materials, including lot traceability, the measured process characteristics and welder certifications. The approach can also be used for ASME certification.

Commentary by Dr. Valentin Fuster
2017;():V001T05A015. doi:10.1115/POWER-ICOPE2017-3552.

This paper presents the instruments developed for shell and tube heat exchangers and their measurements made in operating large scale HX units. These instruments provide in-situ, long-term direct measurement of temperatures and fluid flow rates that are important for evaluation of the desirable and undesirable effects of a HX design. Unique results of this instrumentation are the 3-dimensional measurements of temperature at the inlet, outlet, and along the length of heat exchanger tubes, total tube side flow, and individual tube flow measurements. The temperature measurements are interpolated in a 3-D computational space for design assessment and engineering evaluation. These results have been used to design upgrades for underperforming steam surface condensers. Data from these instruments, the evaluation process, and design effort could lead to development of a new class of better performing heat exchanger designs.

Commentary by Dr. Valentin Fuster
2017;():V001T05A016. doi:10.1115/POWER-ICOPE2017-3646.

Detailed 2-axis hot-wire anemometry measurements were conducted around a scale Air-Cooled Condenser (ACC) model within an atmospheric boundary layer wind-tunnel. The measurements were taken for the “standard” flow field, as well as the effects of using partial wind screens and louvers as mitigation measures. This provides a representation of the complex 2-D flow field present underneath an operating ACC when subjected to various speed cross winds.

Optimal ACC operation is achieved when all fans generate a uniform flow pattern into the plenum chamber of the ACC, and this is dependent on the speed and direction of the air at the inlet. The wind-tunnel measurements support the assertion that wind screens reduce the horizontal wind speed directly downstream; however, this comes with a marked increase in turbulence. The results suggest a wind-screen covering a smaller portion (6% tested) of the ACC inlet may be more beneficial than the more common 50% coverage.

Commentary by Dr. Valentin Fuster

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