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ASME Conference Presenter Attendance Policy and Archival Proceedings

2015;():V06AT00A001. doi:10.1115/IMECE2015-NS6A.
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This online compilation of papers from the ASME 2015 International Mechanical Engineering Congress and Exposition (IMECE2015) 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to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.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

Energy: Biofuel Production, Combustion and Applications

2015;():V06AT07A001. doi:10.1115/IMECE2015-50159.

This paper reports performance evaluation of four–stroke, single–cylinder, water cooled, variable compression ratio (3–9), variable speed (2200–3000 rpm) spark ignition engine with brake power of 2.2 kW at a speed of 3000 rpm with copper coated combustion chamber (CCE) [copper-(thickness, 300 μ) was coated on piston crown, inner side of liner and cylinder head] with alcohol blended gasoline [20% methanol with 80% gasoline; 20% of ethanol with 80% of gasoline by volume) with varied spark ignition timing provided with catalytic converter with sponge iron as catalyst along with air injection and compared with engine with conventional combustion chamber (CE) with gasoline operation. Performance parameters and exhaust emissions (CO and UBHC) were evaluated at full load operation of the engine. Aldehydes (formaldehyde and acetaldehyde) were measured by wet method of 2,4, dinitrophenyle method at full load operation of the engine. Alcohol blended gasoline operation improved performance and reduced CO and UBHC emissions when compared with gasoline operation with both versions of the combustion chamber. At recommended and injection timing, CCE with test fuels improved performance and reduced pollution levels, when compared with CE. Catalytic converter with sponge iron as catalyst along with air injection significantly reduced pollutants with test fuels.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A002. doi:10.1115/IMECE2015-50541.

Palm methyl ester (PME) is an attractive alternate fuel that is becoming popular in Asia and has the potential for a wider application. In this study, the near-burner flame characteristics in the laminar partially premixed flames of Jet A, PME and their blends (25%, 50% and 75% by volume) were investigated. Planar laser-induced fluorescence (PLIF) technique was used to determine the relative concentration of OH and CH radicals in the near-burner region of the flames. The fuel was prevaporized by injecting into a hot air stream and passed through a 9.5 mm stainless steel tube which served as the injector. The burner exit equivalence ratios of 2, 3 and 7, were selected to simulate a wide range of (high to low) partially premixed modes of combustion that exist in practical combustors. The PLIF measurements indicated that the OH and CH concentrations closely followed the temperature profiles at the equivalence ratio of 2. The blend-fuel flames had higher OH and CH concentrations than the neat fuel flames at equivalence ratios of 2 and 3. At the equivalence ratio of 7, a significant reduction in OH concentration was observed in the near-burner region of the flames having biofuel content, and the CH concentration was comparatively higher than OH concentration of corresponding flames. The presence of high CH concentration in the region of peak NO concentration indicated that the NO formation at this condition was likely through the Fenimore mechanism. The concentration measurements of OH and CH radicals revealed a non-monotonic variation with the proportion of biofuel in the fuel blend and suggested a complex competition between the growth and oxidation of poly aromatic hydrocarbons (PAH) and soot particles, and the formation of combustion products.

Topics: Ester , Flames
Commentary by Dr. Valentin Fuster
2015;():V06AT07A003. doi:10.1115/IMECE2015-51713.

Ignition delay of category A and C alternative aviation fuels have been investigated using a rapid compression machine (RCM). Newly introduced alternative jet fuels are not yet comprehensively understood in their combustion characteristics. Two of the category C fuels that will be primarily investigated in this study are Amyris Farnesane and Gevo Jet Fuel Blend. Amyris direct sugar to hydrocarbon (DSHC) fuel (POSF 10370) come from direct fermentation of bio feedstock sugar. Amyris DSHC is mainly composed of 2,6,10-trymethly dodecane, or farnesane. Gevo jet blend stock fuel is alcohol to jet (ATJ) fuel (POSF 10262) produced from bio derived butanol. Gevo jet blend stock is composed with iso-dodecane and iso-cetane, and has significantly low derived cetane number of 15. The experimental results are compared to combustion characteristics of conventional jet A fuels, including JP-8. Ignition delay, the important factor of auto ignition characteristic, is evaluated from pressure trace measured from the RCM at University of Illinois, Urbana-Champaign. The measurements are made at compressed pressure 20bar, intermediate and low compressed temperature, and equivalence ratio of unity and below. Direct test chamber charge method is used due to its reliable reproducibility of results. Compared to category A fuels, different combustion characteristics has been observed from category C fuels due to their irregular chemical composition.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A004. doi:10.1115/IMECE2015-51900.

Diesel engine can be run with renewable biodiesel which has the potential to supplement the receding supply of crude oil. Use of biodiesel in diesel engines can also reduce harmful emissions of CO, unburned HC and particulates. As biodiesel possess similar physiochemical properties to diesel, most diesel engines can be run with biodiesel with minimum modifications. However, the viscosity and calorific values of biodiesel are higher and lower, respectively than diesel which will affect the performance of diesel engine run with biodiesel. Use of 100% biodiesel in diesel engines shows inferior performance of having lower power and torque. Guide vanes into the intake runner to improve the in-cylinder airflow characteristic to break down higher viscous biodiesel is the aim of this research. This is expected to improve the air-fuel mixing resulting better combustion. The experimental results of biodiesel run in a diesel-gen set showed that break specific fuel consumption reduced in between 0.90 and 1.77% with vane numbers of 3 to 5. In regards to emissions, CO reduced in the range 0.05 and 8.78%, CO2 reduced in the range of 0.82 and 1.75%, and HC in the range of 1.19 and 7.49% with vane numbers of 3 to 5. Interestingly, most improvements were found with the vane numbers of 4.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A005. doi:10.1115/IMECE2015-52047.

Bio-derived fuels have received significant attention for their potential to reduce the consumption of petroleum-based liquid fuels, either through blending or direct use. Bio-feedstocks that employ algae, in particular heterotrophic microalgae, which convert sustainable plant sugars into renewable oils are especially attractive because the sugar that feeds this process can come from many sources — from sugarcane to corn, and even waste biomass, also known as cellulosic sugars. The microalgae grow in the dark and transforms sugar into nearly any oil type for almost any purpose anywhere, all while drastically compressing production time, from months and years to a matter of days.

Much of the work in this area has focused on fuel production technologies. Little research has been reported on the combustion performance of algae-derived fuels, with most of the effort being directed to more system-level studies associated with combustion in engines.

In this paper, we report the results of experiments that address some more fundamental multiphase combustion characteristics of algae-derived fuels relevant for spray combustion, namely a configuration involving a single isolated burning droplet. Experimental conditions are created that promote near spherical symmetry such that the gas flow arises primarily through the evaporation process (i.e., stationary droplets are ignited by spark discharge in stagnant air in the standard atmosphere and the droplet burning history is recorded in a free-fall facility that minimizes the influence of buoyant convection). The combustion symmetry that results, in which the droplet and flame are concentric spheres, facilitates the understanding of the combustion process while providing useful validation data for basic models of droplet burning that assume one-dimensional gas transport.

Experiments were performed using algae-derived renewable diesel, and its performance was compared to #2 diesel fuel and a mixture of algal renewable diesel/#2 diesel (0.5 v/v). Additionally, the results of detailed chemical analysis are reported where it is shown that the composition of the algae-based diesel that was employed in the experiments was comprised of a complex mixture of aromatics and normal alkanes. The highly sooting propensity of these components resulted in droplet flames being luminous and producing soot during the burning history.

A comparison of the flame brightness suggests that the sooting propensities are in the order of #2 diesel > renewable diesel #2 diesel blend > algae renewable diesel, which is consistent with observations of the sooting dynamics from back-lit droplet images. In spite of this difference in sooting propensities, algal renewable diesel droplets were found to have burning rates that are very close to #2 diesel and the mixture. Furthermore, the relative position of the flame to the droplet was almost indistinguishable for the fuels examined. These results suggest that algae renewable diesel could potentially be considered a drop-in replacement for conventional diesel fuel, or at the least serve as a useful additive to reduce the consumption of petroleum-based #2 diesel fuel.

Topics: Combustion , Drops , Diesel
Commentary by Dr. Valentin Fuster
2015;():V06AT07A006. doi:10.1115/IMECE2015-52232.

This paper investigates the improvements in the temperature distribution of biomass in an alternative design of fixed-bed biofuel batch reactor while undergoing fast pyrolysis, compared to the conventional design. The reactor furnace temperature was selected based on optimum pyrolysis temperature and appropriate convective heat transfer coefficient was computed and used with corresponding boundary conditions for transient thermal analysis using ANSYS software. For the 3-D model, about eighty-one thousand and sixty-eight thousand elements were used for the conventional design and alternative design, respectively; while for the 2-D model, about three thousand elements were used for both the conventional and alternative designs in the transient ANSYS heat transfer analysis. The results show that the alternative design, which includes the use of extended surfaces, improves the temperature distribution in the reactor by making it more uniform during the fast pyrolysis process. The implications of this are that the alternative design gives a greater yield of bio-oil per batch run, and steady-state conditions are reached within 40% of the time taken for the conventional design, which translates to a shorter process time and reduction in overall energy input, thereby making it a more efficient system.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A007. doi:10.1115/IMECE2015-53437.

Due to the intensive and extensive consumption of fossil fuels in all life sectors such as transportation, power generation, industrial processes, and residential consumption lead to find other new alternative fuels should be the target to cover this fuel demand. Fossil fuel resources are considered non-renewable sources and they will be depleted in the near future. In addition to its environmental impact which causes global warming, harmful exhaust emissions, and its price instability. Waste cooking oil (WCO) was considered as one of these alternative fuels and additives which will provide the industry with low price fuel and may solve the problem of getting rid of waste cooking oil. The present work demonstrated a comparative study for combustion characteristics between light diesel oil (LDO) and waste cooking oil in a swirled oil burner. Waste cooking oil was used directly as a fuel inside a cylindrical combustor using a swirled liquid oil burner at different operating conditions. Waste cooking oil was preheated to 90 °C before entering oil burner to decrease its viscosity and near to light diesel oil. Physical and chemical properties of waste cooking oil were measured and characterized according to ASTM standards. Combustion characteristics of this swirled oil burner using waste cooking oil and light diesel oil were experimentally investigated. Axial and radial inflame temperatures; exhaust gas emissions concentrations and combustor efficiency were analyzed. The experimental results showed that the increase of primary air pressure led to increase in exhaust gas temperature for LDO and WCO. CO2 emissions values for LDO increased compared to WCO. Hydrocarbons a emissions for WCO were higher than LDO. Percentage of heat transferred to the combustor wall increased for WCO compared to LDO. Increase of radial inflame temperature of WCO compared to LDO was due to the increase in heat release at high equivalence ratio. Waste cooking oil tended to produce luminous flames compared to diesel oil due to higher carbon content in its chemical composition.

Topics: Combustion
Commentary by Dr. Valentin Fuster
2015;():V06AT07A008. doi:10.1115/IMECE2015-53597.

A series of experiments were performed on a flat honeycomb burner with air coflow to ensure laminar flow in order to study the effect of Acetylene/Argon mixture to the natural gas (NG) on the temperature distribution and flame structure. The burner assembly could be traversed in the horizontal and vertical direction controlled by using a field point system to scan the flame radially and axially. The flow rate of fuel, diluents and air was measured using differential pressure flow meters. The whole supply lines were calibrated. Methane gas, air and Acetylene/Argon mixture were injected through mixing pipes controlled with solenoid valves handled with a LabVIEW program. The combustion flame was in room atmospheric conditions with room disturbances controlled to treat such flames as free jet diffusion flames. The laminar flame axial and radial temperature profile was measured using a shielded-aspirated platinum/ Platinum-13% Rhodium thermocouple (type R). Flame images were taken using Canon EOS camera with CMOS sensor, up to 3.7 fps. The fuel used was NG with flow rate from 180 up to 520 ml/min. Ar flow rate up to 350 ml/min and C2H2 up to 100 ml/min with a constant coflow air of 3 l/min. The choice of the different Investigated cases was based on flame stability. The results obtained indicate the following:

– In case of using air, NG and Ar, the fuel rich zone tends to vanish and in case of injecting Ar and acetylene mixture in addition of NG and air the front zone tends to vanish and the flame became mainly diffusion.

– Maximum temperature was at the flame tip in all cases. Increasing Ar percentage up to 50% decreases tip temperature to nearly 870°C compared to the typical case (about 1000 °C); increasing acetylene content over 15% resulted in dense soot formation.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A009. doi:10.1115/IMECE2015-53612.

As the intake system design is significant for the optimal performance of internal combustion engines, this work aims to optimize the geometry of an intake system in a direct injection (DI) diesel engine. The study concerns the geometry effects of three different intake manifolds mounted consecutively on a fully instrumented, six cylinders, in line, water cooled, 19.1 liters displacement, DI heavy duty diesel engine. A 3D numerical simulation of the turbulent flow through these manifolds is applied. The model is based on solving Navier-Stokes and energy equations in conjunction with the standard K-ε turbulence model and hypothetical boundary conditions using ANSYS- CFX 15. Numerical results of this simulation are presented in the form of flow field velocity as well as pressure field. Optimal design of the intake system is performed and the modeling made it possible to provide a fine knowledge of in-flow structures, in order to examine the adequate manifold. Engine performance characteristics such as brake torque, brake power, thermal efficiency and specific fuel consumption are also carried out to evaluate the effects of the variation in the intake manifold geometry and to validate the optimal design. Simulation and experimental results confirmed the effectiveness of the optimized manifold geometry on the engine performances.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A010. doi:10.1115/IMECE2015-53635.

Increase of the capacity of heavy duty diesel engines is of great interest in the way of power enhancement in many engine applications. Turbocharger is one of the most important ways used to increase the engine specific power. The present study aimed to develop an analytical model to simulate the performance and combustion characteristics of a direct injection diesel engine. This model depends on the basic conservation equations of continuity, momentum and energy as well as equation of state, these equations are solved together numerically by using two steps Lax-Wendroff scheme. To address this, a comprehensive computer “FORTRAN” code was developed and applied to study the performance and combustion characteristics of a six-cylinder, four stroke, direct injection, heavy duty diesel engine as a base engine and when its power upgraded by 15% using a turbocharger. This code is open source, preprocessor is user-friendly and very easy in work and will used at any time. The computed results are compared with the results obtained by applying the engine simulation DIESEL-RK software. But the DIESEL-RK solver may be run under the control of an external code. In that case the interface of the program includes input & output text files. Templates of these files are generated automatically. The developed model provides reasonable estimates and the experimental validation of the model show that an appropriate agreement between mathematical model, DIESEL-RK software, and the real measurements, in addition the capability of the model to predict satisfactorily the performance, and combustion characteristics of the direct injection diesel engine. Simulation study was also performed to compare the turbocharged engine with the naturally aspirated direct injection diesel engine. This study examined the engines for operating parameters like brake power and brake specific fuel consumption over the entire speed range and revealed that turbocharging offers higher brake power and lower brake specific fuel consumption values for most of the operating range. The results indicated that turbocharging offers marginally higher brake thermal efficiency and enhancing the engine performance.

Topics: Diesel engines
Commentary by Dr. Valentin Fuster

Energy: Biomass Gasification and Combustion

2015;():V06AT07A011. doi:10.1115/IMECE2015-51599.

This study presents the experimental combustion characteristics of biomass briquettes made from agricultural wastes (coconut fiber and corn cob) of Córdoba-Colombia. For this thermochemical conversion, the actual heat transfer during the process and the main combustion characteristics are also studied. Initially, several corncob and coconut fibers briquettes were produced and burned. The non-adiabatic flame temperatures and the air velocity were measured. To study the combustion process dynamics, a process simulation was performed in EES Software© using the typical mass balances of a combustion process, and taking into account the possible stoichiometric equation, using as input the elemental analyzes of each biomass and the excess air that was determined experimentally. The exhaust gases and completeness combustion with moist air were evaluated and usual combustion parameters and correlations like energy balance, enthalpy of formation of the exhaust gases and process exergy were calculated. Likewise, the heat transfer by convection, radiation and heat flow at the gas outlet was evaluated, referenced to the process temperatures. It was found that values of non-adiabatic flame temperature were around 500 ° C, while surface and gases temperatures were between 60–81 ° C and 60 ° C respectively. In general, low emissions of harmful gases to the atmosphere were generated during the combustion of these briquettes. As well, the energy availability at the outlet can be used for moderate heating processes. These findings make these types of biomass a viable alternative to be utilized as renewable energy source.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A012. doi:10.1115/IMECE2015-51633.

This paper is about the development of a computational method to determinate the energy generation potential from residual biomass gasification, in function of the variables and working conditions as the equivalence ratio (ER), and the elemental composition of the biomass, using air as gasifying agent; and by this way promote the generation of low cost energy, whether it be electrical or mechanical energy in order to take advantage of products which normally have no value added. This method was developed using the simulation software of chemical and thermodynamic processes Aspen HYSYS®, this software has a large number of components and the possibility of evaluating their physicochemical properties, along with the equations of state of Peng-Robinson which allow you to define the properties of different fluids with a low error range.

The energy generation potential was evaluated with 5 different biomasses commonly generated by agroindustry in Córdoba-Colombia (Rice husk, sesame stalks, cotton waste, corncobs and coconut fiber) by a modeling of the kinetics of the reactions, where a combination between the reaction mechanisms in function of the Gibbs free energy and reactors, whose yields have been programmed from statistical regressions obtained from other reference, was carried out, and thus simulate the gasification process at 1000 ° C and an ER between 0.21–0.3, getting in this way a synthesis gas with heating values of around 6 (MJ /Nm3) and efficiencies of around 60%.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A013. doi:10.1115/IMECE2015-51692.

During the past decades, combustion of producer gases from other facilities has been introduced as one of the promising techniques in steel furnaces. The impurities inside producer gases are responsible for a low quality steel production due to formation of the molten ash that forms sticky layers of solutions on steel surfaces. Therefore, a comprehensive investigation is needed before a full implementation of producer gases inside the industrial furnaces. In this paper, the effects of impurities inside the gasified biomass flue gases are thermodynamically investigated regarding temperature zones inside a reheating furnace. After that, the high temperature agent combustion (HiTAC) is investigated as a solution for a steel batch reheating furnace to reduce the side effects of using the producer gases. Finally, computational fluid dynamics (CFD) is used as a numerical technique to compare four different producer gases in the studied furnace. The temperature distribution is validated with existing literature data. It shows a good agreement with a 5% error in the heating and a 10% error in the soaking zones of the reheating furnace. The comparison of simulation results assists in the understanding of the chemical and thermal behavior of different gases and provides useful data for the furnace fuel optimization.

Topics: Gases , Steel , Fuels , Furnaces
Commentary by Dr. Valentin Fuster
2015;():V06AT07A014. doi:10.1115/IMECE2015-51966.

Although alternative energy sources, such as nuclear, wind, and solar, are showing great potential, hydrocarbon fuels are expected to continue to play an important role in the near future. There is an increasing interest in developing technologies to use hydrocarbon fuels cleanly and efficiently. The gasification technology that converts hydrocarbon fuels into syngas is one of these promising technologies. Entrained-flow gasifiers are the preferred gasifier design for future deployment due to their high carbon conversion, high efficiency and high syngas purity. Current designs of entrained-flow gasifiers still have serious problems such as injector failure, refractory failure, slag blockages, downstream fouling and poisoning, poor space efficiency, and lack of dynamic feedstock flexibility. To better understand the entrained-flow gasification process, we performed parametric studies of coal gasification in the laboratory-scale gasifier developed at Brigham Young University (BYU) using ANSYS FLUENT. An Eulerian approach was used to describe the gas phase, and a Lagrangian approach was used to describe the particle phase. The interactions between the gas phase and particle phase was modeled using the particle-source-in-cell approach. Turbulence was modeled using the standard k-ε model. Turbulent particle dispersion was taken into account by using the discrete random walk model. Devolatilization was modeled using a version of the chemical percolation devolatilization (CPD) model, and char consumption was described with a shrinking core model. Turbulent combustion in the gas phase was modeled using a finite-rate/eddy-dissipation model. Radiation was considered by solving the radiative transport equation with the discrete ordinates model. Second-order upwind scheme was used to solve all gas phase equations. First, the numerical model was validated by using experimental data for the mole fractions of the major species (CO, CO2, H2, and H2O) along the gasifier centerline. Then, the effects of concentrations of steam and oxygen at the inlets, and steam preheat temperature were studied. Model predictions found that increasing the steam concentration or steam preheat temperature in the secondary inlet generally decreases CO concentration, while increasing CO2 and H2 concentrations. Increasing the steam concentration in the secondary inlet showed no significant effects on predicted gas temperature in the gasifier. Increasing the oxygen concentration in the primary inlet generally increases gas temperature, CO and CO2 concentrations, while decreasing H2 concentration.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A015. doi:10.1115/IMECE2015-52119.

This paper studied, through an experiment design, the significance of particle size, air speed and reactor arrangement for palm shell micro-gasification process in order to optimize the heating value of the syngas obtained. The range of variables was 8 to 13 mm for particle size, 0.8–1.4m/s for air velocity, and updraft or downdraft for the reactor type. It was found that the particle size and air velocity factors were the most significant in the optimization of the output variable, syngas heating value. A heating value of 2.69MJ / Nm3 was obtained using a fixed bed downdraft reactor, with a particle size of 13 mm and 1.4 m/s for air speed; verification of the optimum point of operation under these conditions verified that these operating conditions favor the production of a gas with a high energy value.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A016. doi:10.1115/IMECE2015-52444.

Gasification is incomplete combustion of solid fuel that results in the production of vapor, often referred to as syngas or producer gas, char, and tar. When this process is applied to biomass, the resulting char, referred to as biochar, is produced and has been shown to enhance soil fertility and crop growth. As part of a broader effort, this work examines how the gasification process impacts the biochar generated through downdraft gasification. In contrast to previous publications, which only focused on the syngas compositions, this research paper expands the analysis to the composition of the biochar produced in the gasification systems.

In a large-scale gasifier, corn grains at about a 15% moisture level are inserted into a pilot scale downdraft gasifier from the top. In this system, both air and fuel move in the same direction. The air entering the setup is controlled using a damper. Corn grains entering the gasifier pass through a drying zone where the moisture content in it is removed. The dry corn then passes through a combustion and pyrolysis zone, followed by a reduction zone. The high temperature present at the bottom in the reduction zone cracks any tar present in the syngas produced. This syngas exits from the bottom of the gasifier. The char produced has a residence time from half an hour to several hours. About 20% of the fuel that’s inserted in the gasifier is converted to biochar.

An ultimate and proximate chemical composition analysis, BET porosity analysis, and an SEM image analysis were carried out on the biochar produced from this system. From the SEM analysis, a surface area of 2.38 m2/g was obtained. From the ultimate and proximate analysis, it was observed that the biochar had higher carbon content and a lack of volatile components compared to other reported biochars and levels similar to activated carbon. From the BET porosity analysis, both small scale and large-scale pores were observed but quantified comparison with other biochar is still on going. Porosity is known to be an important factor in biochar effectiveness as a soil amendment.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A017. doi:10.1115/IMECE2015-52592.

This research is based on obtaining a mathematical model to determine the efficiency of generating a generator coupled to a biomass gasification process. To do this, it is initially simulated internal combustion engine at the Aspen hysys® licensed software, in order to obtain the shaft work and a representative model of the generation efficiency of the motor; according to the characteristics of the power cycle and product gas from the gasification of agricultural biomass prevailing in the Department of Córdoba – Colombia: Cotton waste (Gossypium hirsutum), Rice husk (Oryza sativa), Sesame stalk (Sesamum indicum), Corn cob (Zea mays) and Coconut fiber (Cocos nucifera).

Subsequently, the generator efficiency is evaluated by the electric power generation simulation phase in the Simulink Toolbox of the MATLAB® software.

The deterministic mathematical models resulting from the simulations above are adjusted by statistical techniques to experimental data and a regression model that assesses the overall system efficiency is obtained. Such efficiencies range from 16 to 20%. Therefore it is concluded that the use of representative crops biomass product’s calorific values in the Department of Córdoba -Colombia, are profitable for electric power generation.

On the other hand, it is important to note that experimental data’s reliable and monitored way acquisition was performed through the SCADA developing; it allowed real time process variables’ intervention presentation.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A018. doi:10.1115/IMECE2015-53026.

A central theme of our prior experimental and computational work on a transonic self-sustaining pulsatile three-stream coaxial airblast injector involved obtaining spectral content from compressible 2-D models and preliminary droplet size distributions from incompressible 3-D models. The three streams entail an inner low-speed gas, and outer high-speed gas, and an annular liquid sheet. Local Mach numbers in the pre-filming region exceed unity due to gas flow blockage by the liquid. Liquid bridging at somewhat regular intervals creates resonance in the feed streams. The effects of numerical decisions and geometry permutations were elucidated. The focus now shifts to compressible 3-D computational models so that geometric parameters, modeled domain size, and non-Newtonian slurry viscosity can be more elaborately explored. While companion studies considered circumferential angles less than 45°, specific attention in this work is given to the circumferential angles larger than 45°, the slurry annular dimension, and how this annular dimension interacts with inner nozzle retraction (pre-filming distance). Additional metrics, including velocity point spectral analyses, are investigated. Two-stream experimental studies are also computationally studied.

Multiple conclusions were drawn. Narrower annular slurry passageways yielded a thinner slurry sheet and increased injector throughput, but the resulting droplets were actually larger. Unfortunately the effect of slurry sheet thickness could not be decoupled from another important geometric permutation; injector geometry physical constraints mandated that, in order to thin the slurry sheet, the thickness of the lip which separates the inner gas and slurry had to be increased accordingly. Increased lip thickness reduced the interfacial shear and increased the thickness of the gas boundary layer immediately adjacent to the slurry sheet. This suppressed the sheet instability and reduced the resulting liquid breakup. Lastly, velocity point correlations revealed that an inertial subrange was difficult to find in any of the model permutations and that droplet length scales correlate with radial velocities.

As anticipated, a higher viscosity resulted in larger droplets. Both the incremental impact of viscosity and the computed slurry length scale matched open literature values. Additionally, the employment of a full 360° computational domain produced a qualitatively different spray pattern. Partial azimuthal models exhibited a neatly circumferentially repeating outer sheath of pulsing spray ligaments, while full domain models showed a highly randomized and broken outer band of ligaments. The resulting quantitate results were similar especially farther from the injector; therefore, wedge models can be used for screening exercises. Lastly, droplet size and turbulence scale predictions for two external literature cases are presented.

Topics: Viscosity , Slurries
Commentary by Dr. Valentin Fuster
2015;():V06AT07A019. doi:10.1115/IMECE2015-53129.

A chemical equilibrium model for fixed-bed gasification is developed, which allows the prediction of the syngas composition, the amount of residual coal or ash, as well as the amount of tars as a function of the gasification temperature and the elemental composition of the biomass and the tars. Moreover, the combustion heat of the gas fuel is calculated, as well as the conversion and process efficiency, in order to perform further analyses which allow the determination of energy potential for different types of biomass under several conditions of moisture and equivalence ratio of gasifying agent. Performance of the proposed model is compared to prediction of some models which were found to be relevant in the literature review. An assessment to the model is also carried out. For this purpose, a case-study is performed for African palm (Elaeis guineensis) shells using a commercial gasifier. Experimental data obtained from the biomass used in the case-study are used to feed the model and perform the assessment. Actual results and model predictions (results) are compared varying the equivalent relation between 0.05 and 0.65, and the moisture content form biomass between 0 and 20%. This case is proposed as a benchmark case for further applications.

Commentary by Dr. Valentin Fuster

Energy: Carbon Capture and Storage

2015;():V06AT07A020. doi:10.1115/IMECE2015-51229.

Carbon dioxide (CO2) emitted from various sources, mainly fossil fuel power plants, is considered responsible of the global warming effect. Many processes and techniques are still under research for CO2 capture and sequestration. On the other hand, it is proposed that the geothermal heat be mined from geothermal reservoirs using captured CO2. In this sense, some theoretical studies show feasibility of using supercritical carbon dioxide (sCO2) as a heat mining media in such geothermal reservoirs. In this work, it is carried out a set of numerical simulations to determine the most effective distance between injection and production wells for extracting geothermal energy utilizing sCO2 (Water is used for comparison). In the study, the permeability is considered in the range of 0.5 mD to 3.5 mD, with the aim of determining also the critical point in which sCO2 works better than water (H2O) as a working fluid. The remaining properties such as volume, density and other thermal properties remain fixed. Afterwards, it is constructed a numerical model which is implemented in TOUGH2 and PETRASIM 5 software to simulate the cases established. In the model, it is considered a simplified control volume, i.e. only one well for injection and one for production, assuming a constant flow rate at the inlet and at the outlet, meaning that sequestration is not taken into account. A length of 300 meter is defined for reservoir thickness, considering also a pressure and temperature of 100 bar and 200 °C, respectively. The energy mined is estimated for a period of twenty-five years. As typically, the sensitivity analysis is performed by varying only one property and keeping the remaining properties constant, isolating in this way the effect of such variable. Results show that for small permeabilities H2O works better than sCO2, but it is possible to assure that for permeabilities greater than 1 mD, sCO2 presents more advantages as extracting heat media instead of water. Both, H2O and sCO2 show a linear behavior. A deep analysis is necessary to carry out, because results shows that sCO2 works better in an intermediate zone (greater than 200 meter length, but smaller than 800 meter length). An unusual behavior is presented when the distances between the wells are varied; water shows a linear behavior increasing monotonically, while sCO2 shows a nonlinear behavior for some distances sCO2 works better. As expected, the more the distance, the greater the amount of the energy mined due to the volume related with each one of the distances.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A021. doi:10.1115/IMECE2015-51962.

Capture of carbon dioxide gas from a flue gas mixture (N2:CO2 = 80:20) using amine-impregnated mesoporous sorbent (NETL-32D) was investigated in a small scale batch unit at ambient temperature and pressure. The variation of local bed temperature at different axial location of the bed, pressure drop across the bed, time to carbon breakthrough and adsorption capacity as a function of moisture content, bed heights and flow rates under both fixed bed and bubbling bed conditions was reported. Further, a time difference between the time to reach the peak bed pressure drop and temperature from the carbon breakthrough was established. The present findings are designed to offer a valuable data set for validation of CFD models studying carbon capture devices.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A022. doi:10.1115/IMECE2015-53384.

Pre-combustion CO2 capture is regarded as a promising option to manage greenhouse gas emissions from power generation sector. In this regard, metallic membranes can provide a significant boost in power plants energy performances, due to their infinite hydrogen perm-selectivity and their ability to operate at high pressure and temperature. However, the properly integration of these devices still requires a deep investigation of power plant behavior, in order to detect the mutual interaction between system components, which may impose constraints on their operating conditions.

This paper aims to investigate a chemically recuperated gas turbine (CRGT) with pre-combustion CO2 recovery based on hydrogen separation through a metallic membrane. At first, the steam reforming and membrane separation processes are investigated, in order to assess their sensitivity to the variation of the main operating parameters. Then, the CRGT power plant with CO2 capture is analyzed, highlighting the effect of system components interaction on energy and environmental performances. In addition, the study accomplishes a preliminary investigation of the system capability to produce an excess of hydrogen to be used as an energy carrier.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A023. doi:10.1115/IMECE2015-53758.

In this paper the coal-fired power plant with CO2 capture by integrating MCFCs system and the integrated coal gasification with CO2 capture by integrating MCFCs combined cycle system are compared with each other in different ways. The effects of the key parameters of MCFC on the performance of two systems, such as CO2 utilization factor, fuel utilization factor and the current density of MCFC, have been analyzed and compared. Aspen Plus soft is used to develop the system models and the key parameters of MCFC are calculated, analyzed and optimized. The flue gas of the coal-fired power plant (CFPP) or the Integrated Gasification Combined Cycle (IGCC) system is used as the reactant gas of MCFC cathode side, reacting with fuel in the anode side and producing power. The anode exhaust gas burns with pure oxygen in the afterburner. The CO2 in the flue gas is further concentrated and captured with the lower energy consumption. The results show that, the efficiency of the coal-fired power plant integrating MCFCs system is about 45.75% when the CO2 capture rate is 88.07%, and the efficiency of the IGCC system integrating MCFCs is about 47.31% when the CO2 capture rate is 88.14%. Achievements in this paper will provide the valuable reference for CO2 capture of coal-fired power plant and IGCC with low energy penalty.

Commentary by Dr. Valentin Fuster

Energy: Design and Analysis of Energy Conversion Systems

2015;():V06AT07A024. doi:10.1115/IMECE2015-50171.

Membrane distillation (MD) is a separation technique used for water desalination, which operates at low feed temperatures and pressures. Direct contact membrane distillation (DCMD) is one of the common MD configurations where both the hot saline feed stream and the cold permeate stream are in direct contact with the two membrane surfaces. An experimental study was performed to investigate the effect of operating conditions such as feed temperature, feed flow rate, permeate temperature, and permeate flow rate on the system output flux. To check the effect of membrane degradation, the MD system was run continuously for 48 hours with raw seawater as feed and the reduction in system flux with time was observed. Results showed that increasing the feed temperature, decreasing the permeate temperature, increasing the feed and permeate flow rate yield an increase in flux. The effects of feed temperature and feed flow rate are the most significant parameters. After 48 hours of system continuous operation flux was reduced by 42.4 % but the quality of permeate (as measured by its TDS) is still very high with salt rejection factor close to 100 %. For the DCMD system under consideration, the GOR values remain between 0.8 and 1.2, for the tested range of operating temperatures.

Topics: Membranes , Water
Commentary by Dr. Valentin Fuster
2015;():V06AT07A025. doi:10.1115/IMECE2015-50414.

A new waste heat recovery scheme based on absorption heat pumps (AHP) applied in CHP (Combined Heat and Power) system was proposed to decrease heating energy consumption of existing CHP systems by recovering waste heat of exhausted steam from a steam turbine of coal-fired direct air cooling units. Based on the establishment of thermodynamic analysis model, through adopting the design parameters of the 135 MW direct air-cooled power plants in China, the performances, especially the exergy losses of the unit as well as its subsystems mainly including six parts at different heating modes were obtained at one specific load. Compared with conventional heating mode, when the thermoelectric ratio is 100%, the power output increases around 3.81 MW, coal consumption rate decreases 11.69 g/(kW·h) and total exergy loss decreases 6.892 MW under 100% THA load, while the energy and exergy efficiencies of the integrated system increase 1.29 % and 1.25 %, respectively. Additionally, the change laws of total exergy loss, energy and exergy efficiency of integrated system at different loads also were studied. The results provide not only theory basis and scientific support for the design of the coal-fired power plants with absorption heat pump recovering waste heat, but also a new scheme of energy saving and optimization for the units.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A026. doi:10.1115/IMECE2015-50479.

Thermal evaporation of moisture from clothes is the main technique used in clothes dryers today. Most of the energy supplied is spent to provide the latent heat of evaporation of water (2.5MJ/kg). This paper presents a novel direct contact ultrasonic system to mechanically remove water from wet fabric. The vibrations from the transducers are transferred by direct contact to the water inside the narrow pores of the clothes. Breaking the capillary adhesion of moisture at the interface between air and water allows water to exit the clothes as cold mist. The cold mist also carries with it most impurities such as minerals or detergents. This cannot be achieved in thermal dryers where water evaporates and leaves the impurities behind. Mechanical extraction of water is expected to be more efficient since thermal processing is not required. The majority of the supplied energy is used to mechanically separate water from the fabric. Initial testing has revealed that it is possible to dry a 1 cm2 piece of fabric from full saturation to a mere 0.4 % moisture content in just 14 seconds.

Topics: Drying , Textiles
Commentary by Dr. Valentin Fuster
2015;():V06AT07A027. doi:10.1115/IMECE2015-50524.

The growing demand for natural gas leads to an increasing LNG market. The amount of traded LNG has more than doubled during the last decade. This trend is intensified by the rising number of liquefaction plants (export terminals) and regasification plants (import terminals). At the end of the year 2013 there were 86 liquefaction plants in 17 exporting countries and 104 import terminals in 29 importing countries. Also the number of floating regasification plants is growing. It is expected that the LNG market will grow with 7 % per year until 2020. In comparison, the market for gaseous natural gas only will increase with approxematly 1.8 % per year. The difference could be led back to the several advantages, when using LNG. Thus LNG enables the extraction of natural gas in offsite areas and leads to a flexible gas market. Especially with improving the efficiency of each part of the LNG chain — liquefaction, transportation, storage and regasification — and its fallen prices the LNG market will continue to grow. For the regasification of LNG different processes have been used, while mainly the vaporization via direct or indirect heating is applied. Due to their location at the coast of the importing country, seawater, air or the combustion gases coming from natural gas are used as thermal energy. A further possibility is the combination of regasification of LNG with generating electricity. Additionally, the regasification of LNG could be integrated into chemical processes (oil refinery and petrochemical plants), where low temperature refrigeration is required. The authors have already reported a concept for the integration of the regasification of LNG into an air separation and liquefactions process, i.e. into a cryogenic processes. In previous publications, an evaluation of the conventional air separation unit in combination with the LNG regasification has been reported. It was emphasized that the integration of LNG leads to a lower power consumption for the entire system. This paper deals with an improved concept for integrating the regasification of LNG into an air separation process. Due to structural changes, comparing the first design and the new design, the system can be further improved from the thermodynamic point of view. The aim of this paper is to discover the potential for improvement by the parametric study. The results obtained from the sensitivity analysis (energetic and exergetic) are reported as well as the results obtained from the advanced exergetic analysis. Some options for new designs of this system are be developed.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A028. doi:10.1115/IMECE2015-50527.

The idea of developing supercritical CO2 power cycles and applying them to industrial processes became increasingly popular in the last decade. Significant research has been done in this field, including the investigation of characteristics of equipment, and parametric optimization of power systems. There are only few publications on refrigeration using CO2, under hot climatic conditions. This paper deals with an application of an integrated conventional and advanced exergetic analysis to a supercritical CO2 power cycle operating in hot climatic conditions. The objective is to obtain detailed useful information about the optimization of the structure and the parameters of the system being considered. Conventional exergetic analyses have some limitations, which are significantly reduced by the so-called advanced analyses. In addition to conventional analyses, the latter evaluate, (a) the interactions among components of the overall system, and (b) the real potential for improving a system component. A conventional exergetic analysis emphasizes more the relative importance of the regenerative heat exchanger compared to the remaining four components (compressor, cooler, expander, and heat exchanger) than the advanced analysis does. The results obtained from the advanced exergetic analysis show that the system being analyzed can be improved by improving the components in isolation from the overall system, because the avoidable inefficiencies caused by the components interconnections are relatively low.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A029. doi:10.1115/IMECE2015-50626.

In this paper an experimental investigation on a lab scale HDH water desalination unit using a Heat pump was presented. From the thermodynamic view, it was found that the electric heater has a coefficient of performance equal unity, while the heat pump has a coefficient of performance greater than one; in other words the dissipated heat has a high scale. In addition, the refrigeration effect could be used as a secondary benefit. The proposed system utilizes the heat rejected and the cooling effect of the mechanically driven vapor compression heat pump for fresh water production. A test rig consisting of a fan, condenser duct, water spray humidifier and evaporator duct was constructed to study the performance under different operating conditions. The effect of air flow rate variation and water spraying direction (cross, counter or parallel) in the humidification process were studied. Experiments were carried out under variable inlet air conditions. Air flow rate was varied from 0.076 m3/s to 0.4054 m3/s. Results showed that cross water spraying humidification tests yielded the highest production rate. The unit’s maximum production rate was found to be 2.8 Liters/hour at a power 1.4091 kW.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A030. doi:10.1115/IMECE2015-51107.

Thermoelectric generators (TEGs) are solid-state heat engines consisting of p-type and n-type semiconductors that convert heat into electricity via the Seebeck effect. Conducting polymers are a viable alternative with intrinsic advantages over their inorganic counterparts since they are abundant, flexible as thick-films, and have reduced manufacturing costs since they can be solution processed. Furthermore, polymers have an inherently low thermal conductivity, thus affording them the option of forgoing some heat exchanger costs. Current examples of polymer TE devices have been limited to traditional flat-plate geometries with power densities on the μW/cm2 scale, where their potential is not fully realized. Herein, we report a novel radial device and evaluate the improved performance of polymer-based TEG based on this architecture. Analytical heat transfer and electrical models are presented that optimize the device for maximum power density, and we obtain the geometry matching condition for this radial device that maximizes the module figure-of-merit. Our radial architecture accommodates a fluid as the heat source and can utilize natural convection alone (due to heat spreading) to obtain high power densities of 1–3 mW/cm2 using state-of-the-art polymer TEs subjected to a temperature difference of 100 K.

Topics: Design , Polymers , Generators
Commentary by Dr. Valentin Fuster
2015;():V06AT07A031. doi:10.1115/IMECE2015-51223.

Coupling cryogenic air separation plant to industrial processes imposes demand change on the air separation process. Therefore, control of cryogenic air separation plant is a must for stable operation. In this research, we introduce a control scheme for heat integrated distillation which is the main process of cryogenic air separation. The control is achieved via decentralized PID controllers, and its performance is investigated using numerical simulation. Sizing of distillation columns, control valves and heat exchanger were undertaken to simulate industrial air separation plant. In order to verify control system performance, five different control scenarios were studied, including switching between full load to part load, and switching between full production of oxygen to full production of nitrogen, which has not been reported in literature. The simulation results show satisfactory performance of control system facing the disturbing scenarios. However, in severe transition cases (i.e. transition from full liquid nitrogen to full liquid oxygen production), liquid level in the low pressure column base increased excessively and approached safe operating limits. This side effect requires care in controllers tuning, or even introducing level interlocks.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A032. doi:10.1115/IMECE2015-52217.

Geothermal energy is one of the no fossil energy sources that has been utilized mainly for electricity generation, by using the so-called high enthalpy geothermal resource. Nevertheless, low and medium enthalpy geothermal resources are most abundant, but utilized in less extension due mainly to technological barriers or the thermal match between temperature of energy resources and the technology requirements. This work presents the analysis of alternatives for integrating a multiproduct system, producing sequentially electricity, ice and useful heating. For the purpose, the cascade utilization concept is considered for geothermal energy, utilizing low and medium enthalpy resources. To carry out the analysis, it is assumed availability of geothermal hot water with different temperatures typical of already drilled geothermal wells or studied geothermal reservoirs in Mexico. In order to produce electricity, ice and heating for further use (dehydration process or greenhouse heat supply), three cascade levels are proposed to operate sequentially and simultaneously. For electricity generation Organic Rankine Cycles are considered, and for ice production, thermally activated technologies are the best candidates. If necessary, supplementary heat is provided as a mean of geothermal energy upgrade; among the technologies to integrate are parabolic trough collectors, linear Fresnel collectors and biomass boiler. Particularly, with regard to Organic Rankine Cycles, are considered the ones that works with geothermal hot water in the range of 90 °C to 125 °C with rated power output between 25 kWe to 250 kWe. For ice production, two type of machines are under study, i.e. single-effect absorption machines with coefficient of performance around 0.6, and half-effect absorption machines with a value around 0.3 for the coefficient of performance. Absorption machines can be activated thermally with geothermal hot water with temperature in the range of 70 °C to 90 °C. Afterwards, a number of alternatives are proposed to integrate the multiproduct system, which are analyzed and compared both from the energy and economic point of view, obtaining in this way the main energy interactions of the systems, including electricity produced, amount of ice produced and heat availability. In the model, economic indicators are evaluated, obtaining for each alternative the capital cost, simple payback and net present value. Results shows quantitatively that cascade use of geothermal energy is a viable concept to increase the use of low and medium enthalpy geothermal resources with increase of energy performance and improvement of economical profit.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A033. doi:10.1115/IMECE2015-52241.

Solar concentric dish collectors and Stirling engines with cavity receivers are commonly considered for this purpose due to the high efficiency for converting solar radiation into mechanical energy. The study and design of a solar collector of this type, and of its cavity receiver, require solving a mathematical model that take into account the geometric, optical and thermal behavior of all components. With an adequate sizing, not only the useful energy produced on the solar device will meet the energy required for the process, but also the absorber temperature will be the needed for the operation of the Stirling engine. This paper focuses on the construction of a mathematical model that represents the operational performance of a concentric solar dish with cavity receiver for its applications in Stirling engines. The purpose is to develop a designing tool for optimization and for quantifying the effect of changing the values of design parameters over any specific output behavior or the overall performance of the system. The parameters in the optimization include: geometrical variables, i.e., the solar dish diameter, the receiver aperture diameter or the focal length; and optical variables, i.e., rim and incident angles, and irradiation interception factor. The objective is to minimize the solar dish collector cost and calculate the heat available to the Stirling engine, contained in the receiver cavity, to be converted in to mechanical energy. The numerical model was coded in the MatLab® programming language. The results of the simulation disclosed a model able to predict, adequately, the optical and thermal behavior of the described system, so that the model can be used to study the operation and also to design parameters. The optimal results disclosed the configuration of a solar collector dish with a rim angle of about 41° and for a dish diameter of 6.58 m and an aperture receiver of 0.12 m for a minimum cost of 4717 €. It was also concluded that the maximum temperature reached in the absorber of a receiver cavity, is limited mainly by the geometric relationships between the dish diameter, receiver aperture diameter and the aperture ratio, and it is possible to obtain an ideal thermal efficiency of 64%.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A034. doi:10.1115/IMECE2015-52315.

District heating networks are important infrastructures to provide high efficient heating and domestic hot water to buildings located in urban areas. Modern district heating networks may involve the use of waste heat, renewable sources and heat from cogeneration thermal storage systems. In addition, management is operated through advanced ICT solutions able to minimize the global primary energy consumption and to increase end user awareness.

Detailed thermo-fluid dynamic simulation tools can be of extreme importance for the optimal management of modern district heating networks. Some of the issues that simulation tools are requested to face are: peak shaving, selection of the operating temperature, operation in the case of malfunctions, storage management. An important requirement consists in the possibility to perform fast simulations, even in the case of complex networks.

This paper aims at presenting a detailed simulation approach that can be applied to large district heating networks. The entire network is represented as constituted by the main pipeline, which may be a tree shaped or a looped network, and various tree shaped subnetworks that distribute water from the main network to each single building. The main pipeline is fully modeled considering fluid flow and transient heat transfer. Subnetworks are simulated using a reduced model obtained from the full model.

This modeling approach is applied to the analysis of transient operation of the Turin district heating network. The thermal request of the users is obtained from temperature and mass flow rate measurements at the thermal substations, available each six minutes. Thermo-fluid dynamic simulation allows one obtaining the corresponding thermal load profiles at the various thermal plants. Results show that a peak request is caused by the temperature reduction in the entire system due to the small thermal request at night. Due to the advective transport of water in the network and the thermal losses, the shape and amplitude of the peak at the plant is completely different than that at the users.

A comparison between simulations and experimental results shows that the model is able to predict the network operation with good accuracy. Using this simulation approach it is therefore possible to examine the effects of variations, obtained through night attenuation or the installation local storage systems, on the thermal request profiles of some of the users on the global thermal load of the network during the start-up transient.

The proposed simulation approach is shown to represent a versatile and important tool for the implementation of advanced management to district heating systems.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A035. doi:10.1115/IMECE2015-52455.

The Stirling cycle has recently been receiving renewed interest due to some of its key inherent advantages. In particular, the ability to operate with any form of heat source (including external combustion, flue gases, alternative (biomass, solar, geothermal) energy) provides Stirling engines a great flexibility and potential benefits for many applications. However, several aspects of traditional Stirling engine configurations (i.e., the Alpha, Beta, and Gamma), specifically complexity of design, high cost, and relatively low power to size and power to volume ratios, limited their widespread applications to date. This study focuses on an innovative Stirling engine configuration that features a rotary displacer (as opposed to common reciprocating displacers), and aims to utilize a preliminary analytical analysis to gain insights on its operation parameters. Although the analysis involves idealizations, it still provides useful design guidelines as a first step towards optimization.

This study adopts some of the assumptions from the well-known Schmidt analysis, and follows a similar approach for the innovative rotary displacer configuration. As part of this preliminary analysis the optimum phase (lead) angle is determined to be 90°. In addition, the work ratio normalized for the optimum phase angle is presented. Other studied parameters include the internal volume of rotary displacer over the volume of power cylinder, and the volume of “dead spaces” over the volume of power cylinder at various ratios. Although the dead space have negative effects on overall performance and efficiency, they are dictated by the practical design constraints. Lastly, this study considers work output of the engine over a range of heat sink to heat source temperature ratios, and varies the heat sink or heat source temperatures independently. The analysis addresses both low and high temperature differential situations for the purpose of waste heat recovery and power generation, respectively.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A036. doi:10.1115/IMECE2015-52906.

This paper investigates the integration of a photovoltaic-Thermal Collector (PV/T) and a Triple Effect Absorption System (TEAS) for cooling residential as well as commercial buildings. Energy and exergy analyses are conducted to examine the performance of the recommended system and to investigate the variation of different operating conditions and PV/T characteristics on the overall performance of the PV/T collector. Power and heat generated by the PV/T system are used to mainly drive mainly the TEAS by supplying power and heat to the HTG. This paper studies the effect of the of average solar radiation for different months during the year on the Coefficient of Performance (COP) and/or the overall efficiency of the (PV/T) collector integrated with TEAS to produce 10 kW of cooling capacity. This paper also investigates how the rate of energy output of the PV/T collector. It is found that energetic and exergetic efficiencies of the PV/T collector as well as the overall energetic and exergetic efficiencies of the integrated system decrease with increasing the solar irradiance. The analyses show that the maximum energetic and exergetic COPs obtained for PV/T integrated with TEAS are 2.32 and 2.06; respectively. Finally, this paper provides a new interpretation in which alternative energy is utilized in operating HVAC cooling systems and presents a new insight into one of the most sustainable integrated systems that can be applied in residential and commercial buildings in the UAE.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A037. doi:10.1115/IMECE2015-52935.

Design and development of energy efficient vehicles is of paramount importance to the automobile industry. Energy efficiency can be enhanced through recovery of the kinetic energy lost in the form of waste heat during braking. The kinetic energy could be converted into a reusable energy source and aid in acceleration, hence the braking system would contribute to improving the overall efficiency of a vehicle. Hydraulic-Pneumatic Regenerative Braking (HPRB) systems are a hybrid drive system that works in tandem with a vehicle’s engine and drivetrain to improve efficiency and fuel-economy. A HPRB system functions by recovering the energy typically lost to heat during vehicle braking, and storing this energy as a reusable source that can propel a vehicle from a stop. The major advantages of a HPRB system are that a vehicle would not require its engine to run during braking to stop, nor would the engine be required to accelerate the vehicle initially from a stop. The benefit realized by this system is an increase in fuel-efficiency, reduced vehicle emissions, and overall financial savings. An HPRB system aids in slowing a vehicle by creating a drag on the driveline as it recovers and stores energy during braking. Therefore, HPRB system operation reduces wear by minimizing the amount of work performed by the brake pads and rotors.

An experimental investigation of Hydraulic-Pneumatic Regenerative Braking (HPRB) system was conducted to measure the system’s overall efficiency and available power output. The HPRB in this study is a 1/10th lab-scale model of a light-duty four wheel vehicle. The design/size was based on a 3500 lbs light-duty four wheel vehicle with an estimated passenger weight of 500 lbs. It was assumed that the vehicle can accelerate from 0–15 mph in 2 seconds. The aim of this work is to examine the effect of heat losses due to irreversibility on energy recovery. The experimental facility consisted of a hydraulic pump, two hydraulic-pneumatic accumulators, solenoid and relief valves, and data acquisition system. The HPRB system did not include any driveline components necessary to attach this system onto a vehicle’s chassis rather an electric motor was used to drive the pump and simulate the power input to the system from a spinning drive shaft.

Pressure transducers, Hall effects sensor, and thermocouples were installed at suction and discharge sections of the hydraulic and pneumatic components to measure hydrodynamic and thermos-physical properties. The measured data were used to determine the system’s energy recovery and power delivery efficiency. Results showed that the HPRB system is capable of recovering 47% of the energy input to the system during charging, and 64% efficient in power output during discharging with an input and output of 0.33 and 0.21 horsepower respectively. Inefficiencies during operation were attributed to heat generation from the gear pump but especially due to the piston accumulator, where heat loss attributed to a 12% reduction in energy potential alone.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A038. doi:10.1115/IMECE2015-53219.

The numerical analysis of solar desalination processes in a unique tray was extended to include an RED device to produce electricity either during operation or using the stored concentrated salt mixture. The motivation for this using device was based on an exergy analysis and the second law efficiency. Previous analysis illustrated how the exergy analysis could be used to identify the irreversibilities in the system and indicated modifications to increase the performance of the tray design desalinator for the sensible energy content of the discharge. The exergy related to the higher concentration level of the discharge is now investigated for a RED device. These analyses are extended to investigate the potential of using the higher salinity of the out flowing brine to produce electrical energy by using the reversed electrodialysis (RED) process. The RED process which converts 70–80% of the change in Gibbs energy to electricity uses the concentrated brine to produce electrical power while the freshwater is being produced. The analysis demonstrates it is possible to produce a maximum electrical output of 0.32 kJ/kg for the expected concentration differences. Using the predicted mass flow over the day of 6 kg/(day m2) it is expected that one could produce approximately 1.9 kJ/(day m2) of electricity in addition to the freshwater production.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A039. doi:10.1115/IMECE2015-53320.

This paper demonstrates the performance analysis of various arrangements of thermoelectric generators to be used for the combination of a Low Temperature Difference Stirling Engine-Thermoelectric Generator hybrid system. To estimate whether the deployed Stirling Engines will perform on satisfactory level it is necessary to determine if a sufficient thermal flux can be provided to the heating part of the Low Temperature Difference Stirling Engine (LTD SE) from the “cold” side of the thermoelectric generator or their combination. This paper reports study results on the performance of a single layer and a cascaded two-layer thermoelectric generator made up of bulk material. These two generators were connected in series and in parallel to produce the combined thermoelectric module operating as a three-layer generator. Also computational data on the temperature distribution across the layers has been obtained using Finite Element Analysis as a part of ANSYS software. Results obtained demonstrate that both the single and two-layer generators provide sufficient heat flux to drive LTD SEs but the total power output from the two-layer generator-Stirling Engine system is considerable higher when the engine is coupled to a single and three-layered thermoelectric generator.

Topics: Engines , Generators
Commentary by Dr. Valentin Fuster
2015;():V06AT07A040. doi:10.1115/IMECE2015-53669.

The development of electric and hybrid electric vehicles is motivated by the high prices of fossil fuels, the need for better efficiency and the minimization of pollutants and greenhouse gas emissions. There are several possible technologies for these vehicles but Plug-in Hybrid Electric Vehicles (PHEV) and Fully Electric Vehicles (FEV) are becoming popular. They both require advanced energy storage and management systems. In the design of these powertrains it is of capital importance to evaluate, not only the required traction energy, but also the energy involved in braking and that has the possibility of being regenerated, in real-world routes and traffic conditions. Type-approval driving cycles are insufficient for this purpose, as they do not include parameters that substantially affect the vehicle dynamics, such as road slope and additional friction due to road winding. This work presents a methodology for the energy characterization of driving cycles, based on the numerical integration of specific power, including new parameters such as specific traction and braking energies, cumulative uphill and downhill slopes and cornering friction energy, as well as energy-power distributions. The methodology will help in the comparison of the available type-approval driving cycles and in the definition of more realistic ones that can be used for better assessment of fuel consumption and emissions of vehicles. With input data from real routes, the procedure will be useful in the design of advanced electrical or hybridized powertrain systems, both to size the components and to define appropriate energy management strategies, with the final goal of an improved efficiency. The methodology will also be valuable in the energy classification of European roads. The paper describes the mathematical model, which allows the quantification of all the important energy flows involved in the evolution of a reference vehicle, following a route. This model was developed in the MatLab/Simulink environment and was applied to the characterization of three type-approval cycles and to three real routes. The results indicate that the type-approval cycles are too soft to adequately emulate present day aggressive traffic conditions. Driving cycles simulating significant road slopes and sinuosity should be used in the future, both for consumption and emissions certification and in the development of new powertrains.

Topics: Vehicles , Cycles
Commentary by Dr. Valentin Fuster

Energy: Electrochemical Energy Conversion and Storage

2015;():V06AT07A041. doi:10.1115/IMECE2015-50850.

An experimental study is presented on designing and electrochemical fabrication of sandwich-structured NiO/Ni/NiO nanotube arrays for suppercapacitor applications. The electrochemical performance of different NiO based electrodes with different values of specific capacitance has been reported, including NiO film (∼309 F g−1)[1], NiO nanosheets (∼600 F g−1)[2], NiO nanotubes (∼266 F g−1)[3] and NiO-TiO2 based nanotubes (∼300 F g−1)[4]. These reported pseudocapacitors are still far from the theoretical value of NiO based capacitance, which is largely attributed to the poor electronic conduction. To overcome this difficulty, we designed and fabricated novel sandwich-structured NiO/Ni/NiO nanotube arrays as pseudocapacitor electrodes on conductive substrates. Fabrication of these nanotube arrays starts with the growth of ZnO nanorods, which then act as sacrificial template. The Ni nanotube arrays subsequently are synthesized by electrodeposition of a Ni layer onto the surface of ZnO nanorods, followed by dissolving the sacrificial template in sodium hydroxide aqueous solution. The final sandwich-structured NiO/Ni/NiO nanotube arrays are then formed by annealing of the Ni nanotubes at temperature of 450°C in air. The aspect ratio of the Ni nanotubes is conformable with the morphology of the ZnO nanorods template and their wall-thickness is determined by the electrodeposition. The thickness of the NiO layer can be further controlled by adjusting the processing parameters of the annealing process (i.e., time and temperature). The results of electrochemical tests, that is, the cyclic voltammetry and galvanostatic charge-discharge cycling measurements, show that the NiO/Ni/NiO sandwich-like nanotubes electrode clearly displays pseudo-capacitive behavior with improved capacitive performance. Experimental data suggest that the metal Ni core in the NiO/Ni/NiO sandwich-like nanotube structures uniquely serves as a channel for high electron transfer rate from current collector to support the rapid redox reaction activated in the bilateral NiO shells with a higher electrolytic accessible surface area, which is responsible for the high performance of energy storage.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A042. doi:10.1115/IMECE2015-52333.

This paper highlights our progress in developing pristine single-walled carbon nanotubes (SWCNTs) into functional materials for lightweight, conductive cathodes in lithium air (Li-air) batteries. We outline a process to produce foams of single-walled carbon nanotubes using liquid processing routes that are free of additives or surfactants, using polar solvents and electrophoretic deposition. To accomplish this, SWCNTs are deposited onto sacrificial metal foam templates, and the metal foam is removed to yield a freestanding, all-SWCNT foam material. We couple this material into a cathode for a Li-air battery and demonstrate excellent performance that includes first discharge capacity over 8200 mAh/g, and specific energy density of ∼ 21.2 kWh/kg (carbon) and ∼ 3.3 kWh/kg (full cell). We further compare this to the performance of foams prepared with SWCNTs that are dispersed with surfactant, and our results indicate that surfactant residues completely inhibit the nucleation of stable lithium peroxide materials — a result measured across multiple devices. Comparing to multi-walled carbon nanotubes produced using the same technique indicates a discharge capacity of only ∼ 1500 mAh/g, which is over 5X lower than SWCNTs in the same processing technique and material architecture. Overall, this work highlights SWCNT materials in the absence of impurities introduced during experimental processing as a lightweight and high performance electrode material for lithium-air batteries.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A043. doi:10.1115/IMECE2015-52407.

A mathematical model is developed for transport of ionic components to study the performance of ionic liquid based lithium batteries. The mathematical model is based on a univalent ternary electrolyte frequently encountered in ionic liquid electrolytes used for lithium batteries. Owing to the very high concentration of components in ionic liquid, the transport of lithium ions are described by the mutual diffusion phenomena using Maxwell-Stefan diffusivity. The model is used to study a lithium ion battery where the cations and anions of ionic liquid are mppy+ and TFSI-. The electric performance results predicted by the model are in good agreement with experimental data. We also studied the effect of load current density on the performance of lithium ion battery using this model. Numerical results indicate that low rate of lithium ion transport causes lithium depleted zone in the porous cathode regions as the load current density increases. This lithium depleted region is responsible for lower specific capacity in lithium-ion cells. The model presented in this study can be used for optimum design of ionic liquid electrolytes for lithium-ion and lithium-air batteries.

Topics: Electrolytes , Lithium
Commentary by Dr. Valentin Fuster
2015;():V06AT07A044. doi:10.1115/IMECE2015-52575.

The development of electrochemical accumulators of charge starting from biopolymer conductors of cassava starch chemically synthesized from cassava and adding plasticizers (glycerol. polyethylene glycol and glutaraldehyde) as well as lithium perchlorate in varying concentration and the addition of polypyrrole, which was prepared electrochemically by chronoamperometry. Each of these polymers is used as a polymer solid electrolyte and electrode respectively. Paratoluensulfonic acid and indigo-carmine was used as counterion. Surface response methodology was implemented in order to maximize experimental conditions for accumulators assembly (chemical compositions of biopolymers) as well as electric properties. For all compositions it shows optimal values of electric properties. Comparing desirability between chemical compositions, it showed that best conditions for assembly of electrochemical accumulator were obtained with composition 2.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A045. doi:10.1115/IMECE2015-52601.

Battery performance reflects the transport and kinetics of related species within the microstructures of battery’s electrode. However, the current homogenized battery models lack detailed morphology of the internal structures of electrodes. In this work, a multiscale battery simulation tool is developed. This model is capable of capturing the impact of microstructures of electrodes on battery performance, by adapting the variational multiscale principle. The developed model is verified through the direct numerical solutions, and compared with the conventional pseudo-2D (P2D) model method. The model has revealed more dynamic battery behaviors related to the variation of the microstructure, such as particle shape, tortuosity, and material composition, while the corresponding result from P2D shows a monotonous change within different structures.

Topics: Electrodes , Batteries
Commentary by Dr. Valentin Fuster

Energy: Energy Systems Components

2015;():V06AT07A046. doi:10.1115/IMECE2015-50005.

Wndows are account for the most of the heat gain in buildings, and to reduce the heat gain, exterior metallic shutters are commonly installed in residential buildings in hot climates. The shutter is typically partially opened to illuminate the indoor space, but potentially reduces the thermal effectiveness of the shutter. Since the temperature difference between the window glass and shutter is high, natural convection, flow in induced in the space between the window and shutter. Experimental measurements are employed to study the effect of the shatter on the heat gain through the window during the month of June. The results indicate that when the shutter is partially opened, the heat gain through window is increased significantly, depending on the shutter opening distance.

Topics: Heat
Commentary by Dr. Valentin Fuster
2015;():V06AT07A047. doi:10.1115/IMECE2015-50058.

This work investigates the feasibility of manufacturing a turbine blade made of a Ti-Al intermetallic alloy by means of investment casting. The work is based on a multidisciplinary approach that combines a conventional CFD analysis of the flow field around the statoric and rotoric blades with the results of several metallurgical studies aimed at the optimization of the alloy composition by finding the best compromise among fracture toughness, oxidation resistance at high temperatures and mechanical properties. The combination of the two techniques lead to an iterative procedure (of which only the first two steps are reported in this paper): a conventional blade is first modeled and the corresponding investment cast is produced via a 3D printing technique; a first version of the blade is built; a modified blade shape is then obtained by a refined CFD study; as a last step the final version of the blade is cast. On the basis of standard operational specifications representative of modern gas turbines, a turbine blade was therefore designed, tested by CFD (ANSYS-FLUENT) to ensure proper fluid dynamic performance, and its levels of thermo-mechanical stress under working conditions were calculated via a commercial CAD software (ANSYS). The fully 3D version of the component was subsequently prototyped by means of fused deposition modeling. A full-scale set of blades (blade height approximately 7 cm, blade chord approximately 5 cm) was produced by means of investment casting in an induction furnace. The produced items showed acceptable characteristics in terms of shape and soundness. The blade alloy was analyzed by performing metallographic investigations and some preliminary mechanical tests. At the same time, the geometry was refined by a complete and more complex CFD study, and a slightly modified shape was obtained. Its final testing under operative conditions is left for a later study. The paper describes the spec-to-final product procedure and discusses some critical aspects of this manufacturing process such as the considerable reactivity between the molten metal and the mold material, the resistance of the ceramic shell to the molten metal impact at temperatures as high as 2073 K and the limit mold porosity that may compromise the component surface finish. Furthermore, a detailed account is provided for the CFD results that led to the modification of the original commercial shape: pressure, velocity and temperature fields in the statoric and rotoric channels are described in some detail, and a preliminary performance assessment of the turbine stage is presented and discussed.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A048. doi:10.1115/IMECE2015-50295.

Shunt capacitor banks are used on power distribution feeders to reduce losses and regulate the voltage level. The decrease in transmission line current also leads to an increase in the amount of demand that can be supplied without increasing the size of the conductors. In order to maximize the benefit of adding capacitor banks to the distribution feeders, the optimal size and location of the capacitors must be determined. This paper presents a novel optimal control approach to both regulate the voltage drop and reduce the copper loss. A cost function that penalizes both energy losses and voltage drop is developed. The optimal size and location of capacitors can be found using the optimal control solution. Computer simulation results are compared with existing methods of determining the optimal size and location of capacitors. Our approach improves on current methods by providing flexibility to both regulate voltage levels and reduce losses.

Topics: Capacitors
Commentary by Dr. Valentin Fuster
2015;():V06AT07A049. doi:10.1115/IMECE2015-50507.

A horizontal cross flow air heated humidifier is designed for three modes of heating. It is tested to investigate its performance in terms of its ability to effectively humidify air. The system investigated in this study has both the humidifier and the heater(s) integrated in one unit. Special low pressure-drop nozzles are used to spray water such that they provide a fine mist, thus they break a liquid to tiny droplets to increase the surface area for better heat and mass transfer between the hot air and sprayed water. Several attempts to improve system performance are made. For example, the effect of adding packing material to further increase heat and mass transfer surface area is attempted. Another attempt is by having an inter-stage heating such that a heating coil (basically a heat exchanger where hot water is circulated in a closed loop) is placed after a first-stage sprayer to heat the air again such that its ability to absorb more moisture increases as it is passed through a second-stage sprayer. A mist eliminator is placed at the exit of the humidifier to make sure water droplets are not allowed to leave the humidifier with the exit humid air stream. Performance parameters used in the analysis include the temperature and humidity of the exit air stream in addition to the humidifier effectiveness that is considered one of the crucial parameters in designing a HDH desalination system. A comparison between different modification to the humidifier are made to select the mode that results in the closest exit air stream to saturation condition and the highest humidifier effectiveness. Adding the packing material showed insignificant improvement to the humidifier performance. On the other hand, the inter-stage heating is believed to be effective in increasing the unit effectiveness.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A050. doi:10.1115/IMECE2015-50518.

This work analyzes the morphological characteristics and fractal dimension of diesel particulate matter (DPM) produced by multipoint-intake fumigation of n-butanol in a diesel engine. A novel methodology based on digital images processing (DIP) of micrographs from transmission and scanning electron microscopy (TEM and SEM) is presented. Two DIP algorithms were developed and compared for identification and cleaning of TEM images background: the semi-automatic (supervised), which uses the Watershed transform, morphological operators and edge detectors; and the automatic (non-supervised), which further includes adaptive threshold methods. Both algorithms performed successfully when compared with manual methods allowing a significant time saving (from 12 hours manual to 2 minutes automatic). Results showed that mean primary particle diameter (dp0), mean particulates agglomerates diameter, and fractal dimension of the agglomerate (Df) of DPM, which were around 30 nm, 70 nm, and 1.9 dimension respectively, were not affected by n-butanol fumigation in comparison with Ultra-low sulfur diesel (ULSD). The algorithms were sensible to the manual selection of the primary particles from the micrographs, strongly affected the determination of total number of primary particles (np0) and its diameter of gyration (dg); but the Df is not affected. Both algorithms performed successful avoiding the user subjectivity and providing significant time saving during the analysis.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A051. doi:10.1115/IMECE2015-50574.

To promote energy and environment security through combustion efficiency improvement as well as CO2 capture and sequestration (CCS), in this study oxygen enhanced combustion of methane has been investigated by using an inherently safe technique of rapidly mixed tubular flame combustion. As a new type of flame, the tubular flame has excellent flame characteristics such as negligible heat loss, aerodynamic stability and thermodynamic stability. Various applications have been proposed and demonstrated for determining the flammability limits, stabilizing a flame in a high speed flow, and obtaining a uniform and large-area laminar flame to heat iron slab or to reduce steel sheet surface. Especially, by individually injecting the fuel and the oxidizer into a cylindrical burner through four tangential slits hence, hence without flame flashback, the rapidly mixed tubular flame burner has been applied to analyze the characteristics of oxygen enhanced methane flame.

To make a fundamental investigation, methane oxygen combustion has been attempted under various oxygen mole fractions with nitrogen and carbon dioxide as the diluents respectively. At first, nitrogen was added to the oxygen stream, and the oxygen mole fraction in the oxidizer was increased from 0.21 to 1.0. A stable, laminar tubular flame can be obtained from lean to rich when the oxygen mole fraction is no more than 0.4. And the maximum adiabatic flame temperature reaches around 2700 K. To enhance the mixing of fuel and oxidizer, nitrogen was also added to the fuel inlet to increase the injection velocity of fuel stream. The results show that by assigning the nitrogen to both the fuel and oxygen inlets to approach the same injection velocity, the flames become more uniform and stable. However, the range of stable tubular flame in equivalence ratio remains almost the same.

Secondly, instead of nitrogen, carbon dioxide was used to dilute the methane/oxygen flames. Thus, the NOX emissions introduced by nitrogen will be greatly reduced, in addition, the main exhaust will be carbon dioxide and steam, which is beneficial for CCS. When carbon dioxide was only added into the oxygen stream, a stable tubular flame was obtained from 0.9 to 1.2 in equivalence ratio at the oxygen mole fraction of 0.21. With an increase of oxygen mole fraction, the stable tubular flame range enlarges in equivalence ratio, and up to the oxygen mole fraction of 0.50, stable tubular combustion could be achieved from lean to rich. By adding carbon dioxide to both the fuel and oxygen inlets to approach the same injection velocity, the upper limit of stable tubular flame increases much. Up to the oxygen mole fraction of 0.86, the stable combustion can be achieved at the stoichiometry, which gives a flame temperature around 3000 K.

To fully understand the flame characteristics above, the chemical effects of carbon dioxide are numerical analyzed in comparing with the nitrogen diluted flames using the CHEMKIN PREMIX code with the GRI kinetic mechanism.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A052. doi:10.1115/IMECE2015-50646.

The inadequate power harvested from piezoelectric materials makes online tuning of the converter duty cycle and switching frequency a difficult task. This paper presents an open-loop control with pre-computed duty cycle profiles to minimize power consumption. Considering the real input signal to the shock absorber is non-sinusoidal when the vehicle passes through a bump, it is beneficial and necessary to apply a suitable duty cycle profile to every impulse excitation so that the power yield is maximized. The power expense is greatly reduced by first calculating offline the array of optimum duty cycle profiles matching a variety of impulse responses using the shock absorber performance model. The profiles are then stored into the micro-controller look-up table and used as needed during the operation of the vehicle.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A053. doi:10.1115/IMECE2015-51030.

Small, hydrokinetic systems generating between 0.5 and 10 kW of power allow for the potential of portable power generation. An optimized propeller turbine approximately 0.6826 m in diameter and a diffuser with an area ratio of 1.31 were used to produce a prototype for preliminary testing. The optimized diffuser augmented hydrokinetic turbine was investigated numerically to predict power and thrust curves for comparison during experimental testing. A gear box with a 10:1 gear ratio was selected for converting torque to angular velocity. A DC permanent magnet generator was selected for mechanical-electrical power conversion. At the ideal generator operating conditions consisting of a shaft rotation rate of 1150 RPM, a voltage of 48 V, and current of approximately 8 A, 375 W of power may be generated at a river flow speed of 1.5 m/s. Numerical predictions coupled with component efficiencies yield a system efficiency of approximately 0.61 before DC/DC conversion and 0.52 after DC/DC conversion.

Topics: Design , Turbines
Commentary by Dr. Valentin Fuster
2015;():V06AT07A054. doi:10.1115/IMECE2015-51468.

An analysis of thermal performance of a vertical Borehole Heat Exchanger (BHE) from a close loop Ground Source Heat Pump (GSHP) located in Guayaquil-Ecuador is presented. The project aims to assess the influence of using novels heat transfer fluids such as nanofluids, slurries with microencapsulated phase change materials and a mixture of both. The BHEs sensitive evaluation is performed by a mathematical model in a finite element analysis by using computational tools; where, the piping array is studied in one dimension scenario meanwhile its surroundings grout and ground volumes are presented as a three dimensional scheme. Therefore, an optimized model design can be achieved which would allow to study the feasibility of GSHP in buildings and industries in Guayaquil-Ecuador.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A055. doi:10.1115/IMECE2015-51570.

Commercial green houses are the back bone of farming industry in world where the climatic conditions are not stable especially in Middle East, Europe and United states. The commercial greenhouses are often high tech production facilities for vegetables or flowers. The glass greenhouses are filled with equipment like screening installations, heating, cooling, and lighting and also may be automatically controlled by a computer to maximize potential growth. Greenhouse concept will provide the stable indoor plant growth environment throughout the year irrespective of the outside climate variance. The indoor climate conditions can be maintained using the properly designed HAVC systems. The conventional commercial green houses are equipped with axial fans and the cooling pads to control the indoor climate conditions without central control of the equipment’s. Financial conditions of the commercial green houses are very important since the cost per plant will be determined by the overall contribution of the capital and operational expenses. In the present scenario the almost 30% of the net profit is eating by the HVAC systems operational cost. The major operation cost is due to the cooling pads work force and the electricity operational cost for the axial fans equipped with metal blade. The up gradation involves mainly the involvement of individual evaporative air-conditioned system instead of conventional systems. The green houses are equipped with individual evaporative cooling units, circulating fans, top mounted air louvers and the control systems to control the entire set up. The initial heat load calculations will give us an idea about the total heat load required to maintain the ambient conditions for indoor plant cultivation. CFD analysis will provide the exact equipment orientation and the load requirement. In conventional greenhouses the conventional equipment’s are equipped to get the results but the same will consume more electrical power and which is not effective in all weather conditions. Heat load calculations will provide us the system demand in a conditioned space based on the available material properties. Based on the heat load results we can do the proper equipment selection and set the airflow based on the demand. CFD analysis will help the modeling of the system in the actual condition. The aim of the study was to analysis the performance study of the individual evaporative cooling units in the greenhouse conditioned space. The results obtained from the heat loads and CFD analysis can be compared. The objective of the present work is to examine the designed Air conditioning system effectiveness in peak summer heat load conditions to check the design parameters (25 °C temperature and 50%RH) inside the greenhouse using Computational Fluid Dynamics (CFD) Analysis.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A056. doi:10.1115/IMECE2015-51874.

The heat from the exhaust gas of diesel engines can be an important heat source to provide additional power and improve overall engine efficiency. Studies related to the applications of recoverable heat to produce additional power using separate Rankine cycle are scare. To recover heat from the exhaust of an engine, an efficient heat exchanger is necessary. For this type of application, the heat exchangers are needed to be designed in such a way that it can handle the heat load with reasonable size, weight and pressure drop. In this project, experiments were conducted to measure the exhaust heat available from a 40 kW diesel generator at different loads. Shell and tube heat exchangers were purchased and installed into the engine. The performance of the heat exchangers using water as the working fluid was then conducted. With the available data, computer simulation was carried out using CFD software CFX to improve the design of the heat exchangers. Geometric variables including length, number and diameter of tubes, and baffle design were all tested separately. Upon investigating how these parameters influenced the heat exchangers’ effectiveness, optimum design of shell and tube heat exchangers was proposed. The proposed heat exchangers were manufactured and experiment was conducted. Two heat exchangers were used to generate superheated steam. These two heat exchangers were arranged in two orientations namely, series and parallel. The proposed heat exchanger was able to produce 2.71 kW additional power using water as the working fluid at an optimum working pressure of 15 bar using parallel arrangement. It was found that parallel arrangement generated 10% more additional power than the series arrangement.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A057. doi:10.1115/IMECE2015-52094.

This paper reports on the results of analyzing yearlong monitored 15 min data from the cooling plant of a large university campus consisting of multiple chillers and multiple chilled water Thermal Energy Storage (TES) tanks. The objective of the analysis was to determine whether the addition of another TES tank would be economically justified under the present electric rate structure and cooling load demand of the campus. The analysis was done: (i) using blended on-peak and off-peak energy rates (an approach commonly adopted due to its simplicity for evaluating different system alternatives and operating strategies meant to reduce cost and/or energy use), and (ii) using the actual electric rate structure which includes energy and demand charges. The latter rate structure suggests a 42 year payback, while the former rates predicted a payback period of over 100 years. If the incremental avoided cost of an additional chiller (to meet anticipated increases in cooling loads) is included in the economic analysis, the payback will be greatly reduced from the 42 year payback, and make this option a design choice meriting further investigation. The study also suggests a way of generating indifference plots which provide insights into how future changes in the electric rate structure would impact the payback period. The methodology adopted in this study would serve as a case study example to energy analysts evaluating TES systems as a design option for meeting increasing cooling demand and reducing costs in an existing building or campus facility.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A058. doi:10.1115/IMECE2015-52284.

Most of the renewable energy sources, including solar and wind suffer from significant intermittency due to day/night cycles and unpredictable weather patterns. Energy Storage systems are required to enable the renewable energy sources to continuously generate energy for the power grid. Thermal Energy Storage (TES) is one of the most promising forms of energy storage due to simplicity and economic reasons. However, heat transfer is a well-known problem of most TES systems that utilize solid state or phase change. Insufficient heat transfer impairs the functionality of the system by imposing an upper limit on the power generation. Isochoric thermal energy storage system is suggested as a low-cost alternative for salt-based thermal energy storage systems. The isochoric thermal energy storage systems utilize a liquid storage medium and benefit from enhanced heat transfer due to the presence of buoyancy-driven flows. In this study, the effect of buoyancy-driven flows on the heat transfer characteristics of an Isochoric Thermal Energy Storage system is studied computationally. The storage fluid is molten elemental sulfur which has promising cost benefits. For this study, the storage fluid is stored in horizontal storage tubes. A computational model was developed to study the effect of buoyancy-driven flow and natural convection heat transfer on the charge/discharge times. The computational model is developed using an unsteady Finite Volume Method to model the transient heat transfer from the constant-temperature tube wall to the storage fluid. The results of this study show that the heat transfer process in Isochoric thermal energy storage system is dominated by natural convection and the buoyancy-driven flow reduces the charge time of the storage tube by 72–93%.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A059. doi:10.1115/IMECE2015-52747.

The combination of increasingly challenging emissions regulations and impending Corporate Average Fuel Economy (CAFE) standards of 54.5 mpg by 2025 presents auto makers with a challenge over the next 10 years. The most promising technologies currently available for meeting high fuel economy and low emissions regulations are increased hybridization, turbo downsizing, and increased Diesel engine implementation. Combining these into a hybrid turbo Diesel is an ideal transition technology for the very near future as battery and other alternative fuels become viable for widespread automotive use.

This paper presents a Diesel emission test stand to improve Selective Catalytic Reduction (SCR) systems for light duty Diesel vehicles, particularly hybrid power systems that experience many start-stop events. Advanced modeling and control systems for SCR systems will further reduce tailpipe emissions below existing Tier structures and will prepare manufacturers to meet increasingly stringent Tier 3 standards beginning in 2017. SCR reduces oxides of Nitrogen, NO, and NO2, from otherwise untreated Diesel emissions. Scientific study has proved that inhaling this harmful exhaust gas is directly responsible for some forms of lung cancer and a variety of other respiratory diseases. In addition to EPA Tier emissions levels and CAFÉ standards, the On-Board Diagnostics (OBD) regulations require every vehicle’s emission control systems to actively report their status during all engine-on vehicle operation. Testing and development with production NOx sensors and production SCR components is critical to improving NOx reduction and for OEMs to meeting strict Tier 3 light duty emission standards.

The test stand was designed for straightforward access to the NOx sensors, injector, pump and all exhaust components. A Diesel Particulate Filter (DPF) followed by a Diesel Oxidizing Catalyst (DOC) precedes the Selective Catalytic Reducer (SCR) injector, mixing pipe and catalyst. An upstream NOx sensor reads engine-out NOx and the downstream NOx sensor reports the post catalyst NOx levels. Custom fabrication work was required to integrate the SCR mechanical components into a simple system with exhaust components easily accessible in a repeatable, controlled laboratory environment.

A Diesel generator was used in combination with a custom designed resistive load bank to provide variable NOx emissions according to the EPA drive cycles. A production exhaust temperature sensor was calibrated and integrated into the software test manager. Production automotive NOx sensors and SCR injector, pump and heaters were mounted on a production light duty vehicle exhaust system. The normalized nature of NOx concentration in parts per million (ppm) allows the small Diesel generator to adequately represent larger Diesels for controls development purposes. Both signal level and power electronics were designed and tested to operate the SCR pump, injector, and three Diesel Exhaust Fluid (DEF) heating elements. An Arduino-based Controller Area Network (CAN) communications network read the NOx Diesel emissions messages from the upstream and downstream sensors. The pump, injector, solenoid, and line heaters all functioned properly during DEF fluid injection. CAN and standard serial communications were used for Arduino and Matlab/Simulink based control and data logging software. Initial testing demonstrated partial and full NOx reduction. Overspray saturated the catalyst and demonstrated the production NOx sensor’s cross-sensitivity to ammonia. The ammonia was indistinguishable from NOx during saturation and motivates incorporation of a separate ammonia sensor.

Topics: Diesel , Emissions
Commentary by Dr. Valentin Fuster
2015;():V06AT07A060. doi:10.1115/IMECE2015-52761.

Exhaust gas recirculation (EGR) and ignition timing have strong effects on engine performance and exhaust emissions. In the present study, detailed chemical reactions with 29 steps of hydrogen oxidation with additional nitrogen oxidation reactions were coupled with an advanced CFD code to investigate the engine performance and emission characteristics of a SI engine fueled with hydrogen. The NOx formation within the engine was computed using the extended Zeldovich mechanism with parameters adjusted for a carbon-free fuel such as hydrogen. The computational results were validated against experimental results with equivalence ratio of 0.84 and fixed ignition timing at crank angle of 5° BTDC (before top dead center). The simulations were then employed to examine the effects of EGR and ignition timing on the engine performance and NOx formation and emission. The EGR ratio was varied between 5% and 15% while the ignition timings considered were 5°, 10°, 15°, and 20° BTDC. It was found that NOx emission increased with advancing the ignition timing away from TDC while the indicated engine power showed an increasing trend with further advancing the ignition timing. Higher indicated mean effective pressure (IMEP) and indicated thermal efficiency were obtained with an advanced ignition timing of 20° BTDC. The model was also run with three different EGR ratios of 5%, 10% and 15% with fixed ignition timing at 5° BTDC. The simulation results quantified the reduction in NOx and the indicated engine power with the increase in the EGR ratio. The computations were consistent with the hypothesis that the combustion duration increases with the EGR ratio. Finally, the maximization of engine power and minimization of NOx emissions were considered as conflicting objectives. The different data points were plotted in the objective space.

Using the concept of “knee”, (5° BTDC, 0% EGR) was selected as the optimal operating point representing the best trade-off between maximum engine power and minimum NOx emissions.

Commentary by Dr. Valentin Fuster
2015;():V06AT07A061. doi:10.1115/IMECE2015-52803.

Renewable energy has surfaced as a power source of interest of the world recently. Wind Energy has been the leading source of renewable energy development for the past several years. The biggest issue with wind energy are wind turbine (WT) drivetrain failures. The gearbox fails after three to seven years of operation while the expected lifetime of the WT is 20 years. The application to the automotive industry inspired the use of continuously variable transmissions (CVT) in a WT. The CVT considered in this study is the Nu-Vinci CVT technology, a Continuously Variable Planetary (CVP) transmission, designed by Fallbrook Technologies. This technology was selected because of its planetary configuration and its ability to transmit larger amounts of torque, which is required for WT applications. The goal of this research was to reduce the Cost of Energy (COE) by increasing the reliability of CVTs in WTs. In this study, two WT systems, one with CVT as the third stage (referred as ‘WT with CVT’) and another with three stage standard gearbox (referred as ‘WT with SG’), are considered. The research question in this study is ‘Does the use of CVTs improve the reliability of drivetrains of WTs?’ To answer this question three specific aims were developed. First, a computational framework had to be developed. Second, a probabilistic dynamic analysis was conducted. Third, a probabilistic analysis on the COE was performed. A computational framework was developed to guide the probabilistic analysis to determine power values and COE. The probability that the generator torque of the WT with CVT will be less than that of the WT with SG is found to be 50.67%. It was also shown that provided the same input speed and torque, the WT with CVT has a slightly higher power generation. In addition, it was shown that there is 54% probability that the WT with CVT will exhibit lower COE than WT with SG. The higher power production is attained while decreasing the COE. From these results, it can be inferred that the reliability of the drivetrain is improved using a CVT.

Topics: Reliability
Commentary by Dr. Valentin Fuster

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