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Coal, Biomass and Alternative Fuels

1988;():V003T05A001. doi:10.1115/88-GT-84.
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Solar Turbines Incorporated, a subsidiary of Caterpillar Inc., is currently developing under DOE sponsorship a coal-fueled version of its industrial Centaur Model H gas turbine for cogeneration applications. A critical sub-system component is the coal-fueled combustor island consisting of a Two-Stage Slagging Combustor (TSSC) with an integrated Particulate Rejection Impact Separator (PRIS). Earlier development of the TSSC consisted of basic feasibility demonstrations and emissions evaluations and has been reported previously together with preliminary system design and assessment data. This paper reports on the continued bench-scale development of the combustor island with the objective of developing a data base suitable for use in scaling-up the design by an order of magnitude to a rating consistent with application to the 3.8 MW Centaur Model H gas turbine. Development activities have included analytical and flow visualization modeling; sorbent injection tests for control of sulfur oxides; and baseline evaluations of a continuous slag removal system. A preliminary engine-size combustor island design is also presented.

Commentary by Dr. Valentin Fuster
1988;():V003T05A002. doi:10.1115/88-GT-86.
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Beginning in 1982, the Department of Energy (DOE), through the Morgantown Energy Technology Center (METC), has been conducting research for the purpose of verifying the feasibility of using coal fuels in heat engine applications. The heat engines of primary concern are the gas turbine and the diesel engine. The overall program objective is to develop the technology base for an environmentally sound, integrated heat engine system which will produce cost-competitive energy from coal. This paper will present the status of the gas turbine portion of this program.

Topics: Coal , Gas turbines
Commentary by Dr. Valentin Fuster
1988;():V003T05A003. doi:10.1115/88-GT-91.
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The combustion characteristics of fuels derived from low rank, coals have been evaluated at firing conditions representative of an industrial gas turbine engine. Data have been acquired for five fuels containing sub-bituminous coal and one using a lignite. The sub-bituminous fuels were coal-water mixtures differing in either the coal processing or coal loading. One slurry was based on minimally-processed coal which contained relatively high ash and internal moisture levels; the coal loading was limited to 42 pct to sustain acceptable handling. The other four slurries presented different loading of an improved-quality form of the same parent coal; slurry loadings up to 55 pct were achieved, providing nearly 50-pct greater heating value than the minimally-processed fuel. The lignite coal was also processed to produce an improved-quality slurry. Attempts to deliver and combust powdered, sub-bituminous coal were not successful. All tests were performed in a combustor configured to achieve geometrically separated zones of fuel-rich and fuel-lean combustion. Test results indicated a lower limit of fuel energy density as necessary to sustain stable combustion; efficiencies greater than 95 pct were only achieved for improved-quality fuels. The staged combustor approach again demonstrated its ability to control the conversion of fuel-bound nitrogen to NOx as concentrations down to 40 ppm (15 pct 02) were recorded.

Commentary by Dr. Valentin Fuster
1988;():V003T05A005. doi:10.1115/88-GT-119.
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The direct use of coal as a gas turbine fuel offers the opportunity to burn coal in an environmentally sound manner at a competitive cost of energy. A development program is underway to verify the feasibility of using coal water mixture to fuel an aero-derivative gas turbine. This paper presents the overall program approach, required gas turbine design modifications, and reports the results from small-scale combustor test facilities.

The GE LM500 gas turbine was selected for this program because of its high efficiency and size, which is appropriate for transportation and cogeneration markets. The LM500 gas turbine power system design will be modified to accommodate coal fuel and any required emissions control devices. The design for the modified annular combustor is complete and preparations for coal fired tests of a 140 degree annular sector combustor are in progress. The combustor design and test development are being supported by a component test program with a One Nozzle Segment Combustor and a single can combustor LM500 Turbine Simulator. These test facilities are providing results on coal water mixture handling and fuel nozzle design, air staging requirements, component metal temperatures, combustor temperature performance, ash deposition rates, and emissions abatement for NOx, SOx, and particulates.

Topics: Coal , Design , Gas turbines
Commentary by Dr. Valentin Fuster
1988;():V003T05A006. doi:10.1115/88-GT-131.
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NYU has an ongoing research program which is being funded by DOE to test three types of high-pressure, high-temperature filters. The main objectives of the testing program are: (1) to establish the performance capability of the filters under high-pressure and high-temperature conditions; and (2) to evaluate the dust collection efficiency. Shakedown tests for a duration of about 50 hours was completed during October 1986. Testing of the electrostatic precipitator (ESP) is in progress. The first test with ESP was performed during the middle of November 1986. The operating experience with respect to the test facility, and in particular with the particulate sampling systems, is reported in this paper. Additionally, some test results are also discussed.

Commentary by Dr. Valentin Fuster
1988;():V003T05A007. doi:10.1115/88-GT-133.
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A mass transfer model is developed that considers diffusive and chemical aspects of sodium sulfate formation and deposition on cooled blades of coal-fired gas turbines. The roles of gas phase condensation of sodium sulfate and multicomponent diffusion across a chemically frozen thin boundary layer are elaborated. A rational procedure is presented for correlating material wastage with laboratory weight gain data obtained by exposing alloy specimens pre-coated with a thin film of salt to SO2-SO3 in an oxygen environment. The sodium sulfate mass transfer model is used in conjunction with the correlation to project blade corrosion and lifetime as a function of gas turbine inlet temperature, blade cooling, and sodium and sulfur contaminant concentration.

Commentary by Dr. Valentin Fuster
1988;():V003T05A009. doi:10.1115/88-GT-186.
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Airfoils of gas turbines and jet engines frequently deteriorate by erosion or corrosion: Protection can be offered by special coatings that are resistant to either erosion or corrosion. However, the conventional corrosion resistant compressor coatings have very poor erosion resistance. Therefore there is a tendency to apply compressor coatings that offer protection against both erosion and corrosion.

The erosion resistance of (improved) conventional aluminium-based compressor coatings and of new TiN, Ti2B and WC coatings was determined at 150° C as a function of the angle of attack. The Ti2B coating had especially promising erosion resistance.

Commentary by Dr. Valentin Fuster
1988;():V003T05A010. doi:10.1115/88-GT-192.
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With the growing interest in burning pulverized coal directly in gas turbines, the problem of fouling — blockage of hot-gas pathways by thick ash deposits — is receiving increased attention. The inertial deposition rate of supermicron ash, which determines the fouling propensity of the coal via the thickness of the deposit, depends linearly on the sticking fraction of ash material arriving at the cooled surfaces, e.g., turbine blades and guide vanes. The magnitude and temperature-dependence of the sticking coefficient will depend on the inventory, composition and physicochemical properties of the liquid ‘glue’ consistent with the prevailing temperature, pressure and trace inorganic elemental compositions. As the deposit evolves in time, it encounters several deposition regimes in the order of increasing surface temperature, each characterized by a different source of liquid glue. The effect of coal-ash constituents on the extent of each of these sticking regimes is investigated theoretically here by means of a model of ‘self-regulated’ ash deposition.

Commentary by Dr. Valentin Fuster
1988;():V003T05A012. doi:10.1115/88-GT-238.
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Coals contain considerable amounts of oxygen in their structures ranging from 30% in brown coal to about 1.5% in anthracites. The distribution of coal oxygen in various functionalities changes drastically with increasing rank. The hetero-atom functionalities in coal and coal products are of importance in the processing of coal. The process of coal conversion relevant to the steam and gas turbine applications are pyrolysis, oxidation and combustion processes. Initial stages of pyrolysis and oxidation (combustion) are the thermal decomposition of the solid coal matrix to free radicals. Oxygen, sulfur, nitrogen and mineral containing free radicals play an important role during combustion thermodynamically. The differences between the coal functionalities in the solid coal matrix contribute to oxidation reactions of first and second order. The first and second order reactions affect the corrosion and deposition rates of the machine components differently.

In this paper functionality differences of various coals with respect to their oxidation characteristics will be discussed.

Topics: Coal , oxidation
Commentary by Dr. Valentin Fuster
1988;():V003T05A014. doi:10.1115/88-GT-295.
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In operating gas turbine engines in dusty environments, severe erosion of compressor and turbine components results. This erosion adversely effects engine performance. Predicting erosion in the rotating machine of gas turbine is a complex problem. This paper presents test data from the high temperature material erosion facility at the University of Cincinnati. Data was obtained between a target temperature of ambient and 649°C (1200°F) for AM355, Rene 41 and L605 cobalt. In addition, particle velocity and impingement angle were varied.

Commentary by Dr. Valentin Fuster

Combustion and Fuels

1988;():V003T06A011. doi:10.1115/88-GT-106.
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The blowout limit of a turbulent jet diffusion flame in co-flowing streams of lean fuel air mixtures is examined. The blowout limit of the flame, and thereby the maximum thermal output of a burner can be extended significantly, without any modification to the burner, through the presence of a small amount of fuel homogeneously mixed with the surrounding air. The extent of this extension is related to the observed limit of fuel concentration in the surrounding stream that brings about flame flashback conditions. The flame blowout limits involving different gaseous hydrocarbon fuels have been established at atmospheric pressure and the data were correlated in terms of the surrounding fuel concentrations relative to their corresponding flashback limits.

Topics: Fuels , Turbulence , Flames
Commentary by Dr. Valentin Fuster
1988;():V003T06A012. doi:10.1115/88-GT-107.
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Detailed measurements of a recirculating, droplet charged air flow within a model combustor are compared with predictions based on three different evaporation models. Similar results are obtained with the simplified d2-law, the uniform temperature model and thin skin model for relatively short droplet-heatup phases. Discrepancies, however, are observed under conditions where the droplet heating phase is relatively long, i.e. at low temperature conditions. Extended evaporation models, therefore, are necessary when the ignition performance is to be analysed.

Commentary by Dr. Valentin Fuster
1988;():V003T06A013. doi:10.1115/88-GT-108.
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Swirlers are very important elements of gas turbine combustion systems, necessary for the proper operation of a modern gas turbine engine.

In this paper the performance of air swirlers with a range of swirl angles and diameters are examined and discussed in the context of recently published papers. Parameters which are included in this discussion are swirl number, swirler thrust, swirler torque, swirler solidity, etc.

Results suggest that swirler “see through” is not necessarily bad, but may be beneficial with respect to swirl number and other parameters. The use of a mean swirler radius to calculate the swirl number and the resulting benefits are discussed and demonstrated.

Commentary by Dr. Valentin Fuster
1988;():V003T06A014. doi:10.1115/88-GT-109.
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Development of a combustion system at the author’s Company was carried out at atmospheric pressure to achieve successful operation of a 5500-hp (Type H) gas turbine on gaseous fuels covering a wide range of Wobbe Index (WI) values from 48.04 MJ/nm3 (1220 Btu/scf) for natural gas to 18.90 MJ/nm3 (480 Btu/scf) for natural gas and carbon dioxide mixtures. Mixtures with the latter composition have direct applications for gas turbine engines burning fuels derived from sanitary landfills and liquid sewage. Wide-range operational capability offers the flexibility to fire gas turbines with either pipeline quality natural gas or medium-heating-value fuel, depending on availability. For such applications, if a fuel injector is designed to operate satisfactorily on natural gas fuel, it will have unacceptably high pressure drops when operating on fuels with WI values towards the lower end of the range. On the other hand, if the fuel injector is designed to operate properly on fuels with WI values on the lower end of the range, it will have unacceptably low pressure drops when operating on fuels with WI values towards the higher end of the range, which causes combustion-driven pressure oscillation feedback into the fuel-injection system. This feedback usually increases the amplitude of combustion-driven pressure oscillation and can cause significant damage to the gas turbine in a relatively short time.

This paper describes the design and development work carried out to resolve these problems.

Commentary by Dr. Valentin Fuster
1988;():V003T06A015. doi:10.1115/88-GT-116.
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The general growth, in recent years, for the decentralized generation of electricity in the Netherlands is shown in terms of capacity and numbers of gas turbines installed by Dutch industry. This growth trend in cogeneration capacity is projected to the year 2000. NOx emissions standards for gas turbine plants are discussed with particular reference to “acid rain”. The contribution to national NOx emissions of gas turbines is presented for the present and for year 2000. Compliance with these standards by metering (source testing and monitoring) and the results of field testing for NOx emissions are shown.

Commentary by Dr. Valentin Fuster
1988;():V003T06A016. doi:10.1115/88-GT-128.
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Gas turbine combustors pose many modeling and design difficulties. This has created an urgent need for experimental research using laser diagnostics to validate and refine computer design models of combustors. In this paper, key practical problems, limitations, and our operational experience with laser diagnostic systems for gas turbine combustion research are described.

It is found that unavailability of a good LDA seeder design and an unambiguous particle bias correction scheme present the main obstacles to using LDA in gas turbine combustor measurements. The practical problems of the Raman/Rayleigh system, particularly above 1200 K are high background luminosity, beam steering due to unmixedness, and high Poisson uncertainty in temperature and concentration measurements. The integration of LDA-Raman systems is beset by optical and data acquisition difficulties. Therefore, considerable work is still required to make the applications of advanced laser diagnostics to measurements in a practical gas turbine combustor a reality.

Commentary by Dr. Valentin Fuster
1988;():V003T06A017. doi:10.1115/88-GT-129.
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Within the U. S., the pollutant emissions at Navy and Air Force airbases are not regulated by civil law. However, there is a desire to be a good neighbor to the local population. On the other hand, military engine test facilities are designated as ground emission sources which are subject to civil air quality regulations. Both situations contribute to a Navy and Air Force requirement for the generation of air quality scenarios, which in turn requires ready access to engine emissions data.

A considerable body of emissions data has been collected for U. S. military aircraft engines over the last twenty years. However, this data is not readily accessible, because it is distributed in a variety of technical publications, and is not presented in a consistent format.

Therefore the Navy, with Air Force cooperation, has sponsored a program to develop an engine emissions database system tailored to their requirements, for use on a microcomputer. The program was conducted by Northern Research and Engineering Corporation. The resulting database contains all of the available emissions data, as well as background information on each engine model and the conditions for each test. All of the unclassified operational engine models of the Navy and Air Force are listed, whether or not emissions data are available. When emissions data is not available for a particular model, but there is a similar engine model whose data can reasonably be substituted, this is identified. The system provides an easy and versatile means of accessing the available emissions data. In general, the computerized database approach can increase the value of many types of experimental data.

Commentary by Dr. Valentin Fuster
1988;():V003T06A020. doi:10.1115/88-GT-164.
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Details are presented of two series of experiments to investigate carbon determination in gas turbine combustion chambers. The first series employed a gravimetric technique to examine carbon distribution within the various zones of a combustor with the aim of identifying zones of formation and oxidation.

In the second series a fairly comprehensive investigation of the technique of measuring Smoke Number was made with the objective of obtaining details relevant to its accuracy and applicability. Mixtures of iso-octane and benzene were used as fuel, thereby permitting the effects of hydrogen content to be established. The results are correlated with othersome obtained previously.

Commentary by Dr. Valentin Fuster
1988;():V003T06A021. doi:10.1115/88-GT-165.
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WZ-5 engine is a small aero gas turbine engine rated in 1200kw class. A development program was initiated in 1986 to develop the engine with some modifications to accommodate the medium or low Btu gaseous fuel for its industrial application. The test program was accordingly carried out for the modified engine and combustor to evaluate their ability to burn medium Btu gaseous fuel. The present investigation is a part of the program to justify whether or not the modified combustor is capable of burning the medium Btu gaseous fuel with satisfactory combustion performances. The medium Btu gaseous fuel used in the test contains 50% of H2 and 20% of CH4 and the rest of N2 as innert. That is the typical processing gas produced in chemical fertilizer production. The low heating value of the gas is 3002 kcal/nm3.

All the test results whowed that when burning the medium Btu gaseous fuel the modified combustor had quite good performances except one combustor which had the injectors with slot-shape opening at the injector end and had unacceptable combustor exit temperature profile, and also showed that the modified combustor had the potential ability to burn low Btu gaseous fuel which has lower calorific value but some amount of H2.

Commentary by Dr. Valentin Fuster
1988;():V003T06A022. doi:10.1115/88-GT-181.
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The principles of pressure-gain combustors based on the wave rotor and pulse-combustor concepts were reviewed briefly. A study, based on experimental data, in which current-technology pressure-gain combustors were applied to three aircraft-engine derivative industrial gas-turbines, covering a power range from 275 kW (370 hp) to 29 MW (39,000 hp), showed that engine power increased by 6.5% to 9.6% with corresponding reductions of equal magnitude in specific fuel consumption. It was concluded that pressure-gain combustors appear to offer sufficient improvements in performance without incurring crippling installational penalties, although decreases in engine power/weight ratios were noted, to warrant further research and development.

Commentary by Dr. Valentin Fuster
1988;():V003T06A023. doi:10.1115/88-GT-194.
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A surrogate fuel has been developed to simulate the atomization and combustion performance of a practical, petroleum distillate JP-4. The surrogate is comprised of fourteen pure hydrocarbons and formulated to reproduce the distillation curve and compound class composition of the parent petroleum distillate fuel. In previous work, the atomization performance (evaluated in terms of the atomization quality in an isothermal chamber), and the combustion performance (evaluated in terms of the mean axial velocity and thermal fields in a spray-atomized, swirl-stabilized, model laboratory combustor) were found to be equivalent for the petroleum and surrogate JP-4. The present study addresses the sooting performance of the two fuels, as well as that of two reference fuels (isooctane and a high aromatic petroleum JP-5) of purposefully disparate properties. The sooting performance of the petroleum and surrogate JP-4 are nearly identical, and distinctly different from that of either the isooctane or the JP-5. The surrogate represents, as a result, an attractive fuel blend for the study of fuel compositional effects on the combustion performance of practical fuels in a spray-fired combustor.

Commentary by Dr. Valentin Fuster
1988;():V003T06A025. doi:10.1115/88-GT-241.
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The present work reports a detailed investigation of air-liquid interaction in sprays along with particle number density and mass flux measurements in complex turbulent flows such as those present in gas turbines and rocket combustors. Data have been obtained for the characterization of sprays in complex flows which include detailed drop size and drop velocity distributions, size-velocity correlations, mass flux, and particle number density. Key factors affecting the measurement of the sample volume size are discussed in detail since an accurate estimation of it is essential to the particle number density and volume flux determined by the instrument. The discrimination of refraction and reflective scattering components and their influence on the measurements is also discussed. Data comparing the phase Doppler results to alternate methods of measuring number density and volume flux are also presented. These results showed agreement to within 15% in most cases for realistic flow configurations.

Topics: Turbulence , Sprays
Commentary by Dr. Valentin Fuster
1988;():V003T06A026. doi:10.1115/88-GT-242.
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In single can combustor ignition tests, different results were obtained for pressure atomizing and airblast atomizing fuel injectors as well as for various ignition locations. In order to understand the effect of fuel spray characteristics and ignition locations on gas turbine combustion ignition characteristics, a computer simulation of fuel droplet ignition at engine starting flow conditions has been conducted. An ignition model for evaporating fuel droplets was incorporated with the numerical droplet tracking scheme in the computational flow field, which included a simulated ignition point source. A large number of various size droplets were computed for their trajectories and ignition reactions. A statistical data base was established to calculate the ignition probability of droplets in terms of number and mass fraction. A correlation between predicted ignition probability trends and experimental ignition data for two different injector/ignitor configurations was demonstrated.

Commentary by Dr. Valentin Fuster
1988;():V003T06A027. doi:10.1115/88-GT-245.
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Swirling flow primary zones with between 30% and 60% simulated primary zone air flow were investigated using curved blade radial swirlers. Two radial swirlers were compared with the same open area but different outlet diameters, d, giving different expansion ratios, D/d, from the swirler to the combustor diameter, D. Two combustors were used, 76 mm and 140 mm diameter, the larger one corresponding to the size of several gas turbine can combustors. There was no influence of D/d on the weak extinction. It was demonstrated that an adequate efficiency was not achieved in the weak region until there was a significant outer expansion and associated recirculation zone. It was shown that these systems with central gaseous fuel injection had good flame stability with very low NOx emissions. Propane and natural gas were compared and the NOx emissions were 50% lower with natural gas. The optimum NOx emissions, compatible with a high combustion efficiency, were close to 10 ppm NOx emissions corrected to 15% oxygen.

Topics: Nitrogen oxides
Commentary by Dr. Valentin Fuster
1988;():V003T06A029. doi:10.1115/88-GT-308.
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An interacting radial and axial multi jet shear layer combustion system is described that has the rapid fuel and air mixing characteristics necessary for low NOx emissions. The radial jet has the fuel mixed with a proportion of the total primary zone flow and a 30% proportion was investigated. This radial jet was fuel rich at most primary zone operating conditions and ensured a flame stability far superior to the premixed situation. The scale up of the design from a 76mm to a 140mm diameter combustor was investigated. It was demonstrated that the distance the radial jet travelled before encountering the rapid mixing with the axial jets, had a strong influence on the combustion efficiency and NOx emissions. For both the 76 and 140mm combustors it was shown that the NOx emissions with propane were 50% greater than those for natural gas. It was also demonstrated that the low NOx emissions of the 76mm system were retained in the larger combustor with the same single central fuel injector design. There was a significant increase in NOx for some 140mm combustor configurations, but the emissions corrected to 15% oxygen below 10ppm were demonstratred, with a high combustion efficiency. The design thus demonstrated, in a practical combustor size, the potential for a dry solution to the NOx emissions problem of natural gas fired industrial gas turbines.

Commentary by Dr. Valentin Fuster

Oil and Gas Applications

1988;():V003T07A002. doi:10.1115/88-GT-230.
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The growing gas market and the increasing ratio of imported gas to gas produced within a country requires an expanded capacity for buffer gas storage to compensate for differences between constant import gas flow and seasonal variances in consumption.

For economical operation of the gas storage facility and for moving extensive quantities of gas, high operating flexibility as well as high availability and reliability of gas compression equipment are required.

This paper will report on an underground gas storage project and indicate specific objectives for the project in reservoir engineering, gas compression and free-flow withdrawal duties. It will also deal with the sizing and selection of gas turbine driven centrifugal compressor sets, including the required station equipment.

Finally, operating experience will be discussed.

Commentary by Dr. Valentin Fuster
1988;():V003T07A003. doi:10.1115/88-GT-247.
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The paper outlines the operating and maintenance experience of the TYPE H industrial gas turbines on 2 of the platforms in the Greater Ekofisk field on the Norwegian continental shelf.

Traditional preventive maintenance procedures based on elapsed fired hours are discussed. Availability and reliability statistics are presented.

Typical component replacement on inspections is tabulated and comments are given.

Finally the author describes an on line, computer supervised, condition monitoring system which is being used and will help replace traditional preventive maintenance with predictive maintenance.

Commentary by Dr. Valentin Fuster
1988;():V003T07A004. doi:10.1115/88-GT-249.
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Kuwait Oil Company (KOC) has installed and operated gas turbines since 1957. There are currently 79 Gas Turbines ranging in size from 700 to 33,000 H.P. of various types, from industrial to aero-derivative.

Gas turbines provide more than half a million in horsepower, which is more than 80% of the power, for machinery and power generation at KOC.

This paper covers the introduction and the rappid growth of gas turbine power at KOC. Operational sites at KOC are subject to severe heat, dust and humidity. The experience in the operation and maintenance in the early years of the gas turbines at KOC are described.

Gas turbines have played a major role in the success of the Company.

Commentary by Dr. Valentin Fuster
1988;():V003T07A005. doi:10.1115/88-GT-250.
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The problems typically encountered with the basic engineering of a combined-cycle installation are examined here in general; the selection criteria of the operating fluid and determination of the thermodynamic parameters of the steam cycle are also dealt with in the appendix.

The combined-cycle gas compression unit at present under construction in SNAM’s Station at Messina is then described extensively; the system, designed to comply with the specific requirements of a gas compression plant (unmanned continuous operation in severe environmental conditions), is characterized by an efficiency higher than 47% at ISO conditions.

Special attention is paid to the control system and to the analysis of the dynamic behaviour of the gas / steam unit by which two pipeline compressors (the main one driven by the gas turbine and the auxiliary one driven by the steam turbine) are made to run in parallel.

Commentary by Dr. Valentin Fuster
1988;():V003T07A006. doi:10.1115/88-GT-266.
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Turbo expanders have been used in a number of installations to generate electricity from the energy available in the process of pressure reduction. The turbo expander replaces the regulating valve and duplicates the functions of the valve, controlling pressure and flow while at the same time generating electricity.

Commentary by Dr. Valentin Fuster
1988;():V003T07A007. doi:10.1115/88-GT-283.
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This paper sets out the advantages of using “off-the-shelf” equipment to produce an effective Compressed Air Energy System (CAES) and to develop the storage parameters of those geological entrapments that can be pressurized with air for the generation of electrical energy on demand.

The long lead time and the developmental cost needed to perfect turbo-machinery for aquifer storage has been a deterrant on the utilities in their desire to implement air storage in aquifers. Off-the-shelf hardware and predesigned turbo-machinery specified herein is readily adaptable to aquifer storage parameters and can be manufactured without the expense and uncertainty related to developmental hardware. Hence, normal equipment manufacturer’s assurances and guarantees are available for these applications.

When compared to the alternative storage opportunities such as; pumped hydro, battery storage and superconducting magnetic storage, the cost of compressed air storage in aquifers is a fraction of the first cost of these alternatives and as good or better in operating costs.

Topics: Stress , Storage
Commentary by Dr. Valentin Fuster
1988;():V003T07A009. doi:10.1115/88-GT-319.
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The PGT 10 two-shaft, 10 MW, industrial gas turbine has a capability of up to 34% simple-cycle efficiency, high reliability with extended range of operation and low exhaust emissions. Features like the 14:1 pressure ratio and high specific mass flow transonic axial compressor are at the highest levels in the heavy-duty gas turbine design. The firing temperature, the blade cooling techniques, the extended modularization of components and subassemblies are in their turn representative of the well-proven, state-of-art technology: performance results also from the aero-thermodynamic design aimed at maximizing component efficiencies.

This paper introduces the major aspects of the PTG 10 turbine design. After full-load testing was successfully completed on the first units, the PTG 10 has entered normal production in 1987 and several units have already been installed or shipped.

Topics: Gas turbines
Commentary by Dr. Valentin Fuster
1988;():V003T07A010. doi:10.1115/88-GT-322.
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A major expansion phase is underway at the Ruhrgas natural gas storage plant at Epe on the border between West Germany and the Netherlands. The plant already has 8 caverns with a total working capacity of approx. 350 × 106 m3 (n). 28 caverns are to be added, to bring the total to approx. 1.0 × 109 m3 (n). In view of the increase in capacity, it was necessary to raise the power installed for driving gas compressors from the existing figure of approx. 3,000 kW to a total of 12,000 kW in phase II. A minimum of 2 units were required for this figure of 9,000 kW.

Epe is already the second largest natural gas storage facility in West Germany and is designed to store both low BTU and high BTU natural gas. The facilities are operated at a wide range of pressures and flow rates. The new compressor units will be used only for gas injection at well head pressures of up to 200 bar.

Commentary by Dr. Valentin Fuster
1988;():V003T07A011. doi:10.1115/88-GT-324.
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When aero-derivative gas turbines were first introduced into industrial service, the prime criterion for assessing the “relative value” of equipment was derived hy dividing the initial (or capital) cost of the equipment by the number of kilowatts produced. The use of “dollars per kilowatt” as an assessment parameter emanated from the utility sector and is still valid providing that the turbo-machinery units under consideration possess similar performance features with regard to thermal efficiency. Second generation gas turbines being produced today possess thermal efficiencies approximately forty-five percent greater than those previously available. Thus, a new criterion is required to provide the purchaser with a better “value” perspective to differentiate the various types of turbo-machinery under consideration.

This paper presents a technique of combining the initial cost of equipment with the costs of fuel consumed, applied labor and parts to arrive at an assessment parameter capable of comparing the relative merits of varying types of turbo-machinery. For simplicity, this paper limits the life cycle cost derivation and discussion to turbo-generator units; however, the principles of this type of life cycle analysis can also be applied to gas turbines in mechanical drive applications and/or combined cycles.

Commentary by Dr. Valentin Fuster

Cycle Innovations

1988;():V003T08A001. doi:10.1115/88-GT-121.
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This paper considers the utilization of the high temperature Brayton closed cycle with air cooled atmospheric fluidized bed combustor in district heating plants.

The main features of a closed cycle plant are compared with those of a conventional steam cycle plant with flue gas desulphurization and with a steam plant fired by a circulating atmospheric fluidized bed boiler.

The characteristics of the main items are analyzed.

Topics: Central heating
Commentary by Dr. Valentin Fuster
1988;():V003T08A002. doi:10.1115/88-GT-122.
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In the chemical heat pipe concept, energy is transported long distances by using a high temperature heat source (e.g., a nuclear reactor) at the sender end to convert a mixture of gases (e.g., CO2 and CH4, or H2O and CH4) into an energy-rich combination (CO and H2), and then transporting the mixture by pipeline at close to room temperature to the receiver end. At the receiver end, the stored energy is released by the reverse reaction to generate steam or produce heat for process purposes. Candidate reactions for this system include the Hy-Co reaction (CO2 + CH4 = 2CO + 2H2) and the Eva-Adam reaction (CH4 + H2O = CO + 3H2). As written, these reactions are endothermic in the forward direction and exothermic in the reverse direction. In the Eva-Adam reaction, the forward conversion (steam or methane reforming) is favored by high temperatures and low pressures. For example, at a temperature of 1100 K and a pressure of 1 atmosphere, the degree of advancement in the forward direction is about 93%. The reverse conversion (methanation) is favored by low temperatures and high pressures. For example, at 800 K and 25 atmospheres, the degree of advancement in the reverse direction is about 95%. Thus, heat representing most of the heat of reaction can be made available at the sender end at a relatively high temperature. Since the system requires two pressure levels, compressors (and turbines to drive them) are necessary, as well as strategically placed heat exchangers. Thus results a closed cycle gas turbine system with a dissociating gas as the working fluid. This paper analyzes the Eva-Adam system and evaluates the energy-delivered to energy-supplied ratio. The efficiency is improved if the return pipeline is insulated.

Commentary by Dr. Valentin Fuster
1988;():V003T08A004. doi:10.1115/88-GT-140.
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An experimental project is now underway to demonstrate the advantages of the Kalina cycle technology. A Kalina Cycle Experimental Plant (KCEP) will be built as a 3 MW bottoming cycle using the waste heat from a facility within the Energy Technology Engineering Center (ETEC), a U.S. Department of Energy laboratory located in Canoga Park, California.

The design of the experimental plant is presented, including the process flow diagram, heat and mass balance, and specifications for the plant’s major equipment; the waste heat boiler, turbine generator and distillation/condensation subsystem.

Using a mixture of ammonia and water at a mass ratio of 70/30, and a new condenser design based on absorption principles, the Kalina cycle plant will attempt to demonstrate its superiority over the Rankine steam cycle. Based on single pressure designs at comparable peak cycle temperatures, the Kalina cycle’s output should exceed that of the steam cycle by 25 percent.

Topics: Design , Kalina cycle
Commentary by Dr. Valentin Fuster
1988;():V003T08A005. doi:10.1115/88-GT-156.
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Bearing lubrication systems in closed-loop plants using gas (air or helium) as the working fluid (e.g., gas turbine, gas-cooled nuclear reactor, gas compressor, etc.) are very demanding since liquid lubricant ingress could contaminate the circuit, unlike open-cycle systems where the products would be expelled in the exhaust. Oil-lubricated bearings, the tribology mainstay in the power plant field, are reliable, but in the event of a failure in the seal or buffer system, the impact of oil ingress (e.g., saturation of insulation, coking on high-temperature surfaces, or in the extreme case, conflagration of equipment) can be costly and result in extended plant downtime.

The emergence in the early 1980s of a new tribology technology, namely a system in which the turbomachine rotor is levitated by a magnetic field, and positively sensed and controlled in real-time by an electronic system, now offers the designer an additional option. While an active magnetic system has many advantages, its foremost are (1) potential for very high reliability, (2) obviates the possibility of closed circuit contamination by lubricant ingress, (3) system simplicity, (4) ease of operation, and (5) ease of critical speed problems.

It is projected that utilization of “electronic chips instead of liquid films” will have a significant impact on the design of high-speed rotating machinery across the full spectrum of applications. This paper outlines the emergence of active magnetic bearings in rotating machinery for closed-cycle gas turbines, and in helium circulators for future high-temperature gas-cooled nuclear power plants. The paper highlights the existing industrial technology base that will make possible the deployment of active magnetic bearings in rotating machinery for the next generation of power plants that utilize closed-loop circuits.

Commentary by Dr. Valentin Fuster

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