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RESEARCH PAPERS: Gas Turbines: Coal Utilization

J. Eng. Gas Turbines Power. 1994;116(2):331-337. doi:10.1115/1.2906824.

A number of advanced technologies are being developed to convert coal into clean fuels for use as feedstock in chemical plants and for power generation. From the standpoint of component materials, the environments created by coal conversion and combustion in these technologies and their interactions with materials are of interest. The trend in the new or advanced systems is to improve thermal efficiency and reduce the environmental impact of the process effluents. This paper discusses several systems that are under development and identifies requirements for materials application in those systems. Available data on the performance of materials in several of the environments are used to examine the performance envelopes for materials for several of the systems and to identify needs for additional work in different areas.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):338-344. doi:10.1115/1.2906825.

The United States electric industry is entering a period where growth and the aging of existing plants will mandate a decision on whether to repower, add capacity, or do both. The power generation cycle of choice, today, is the combined cycle that utilizes the Brayton and Rankine cycles. The combustion turbine in a combined cycle can be used in a repowering mode or in a greenfield plant installation. Today’s fuel of choice for new combined cycle power generation is natural gas. However, due to a 300-year supply of coal within the United States, the fuel of the future will include coal. Westinghouse has supported the development of coal-fueled gas turbine technology over the past thirty years. Working with the U.S. Department of Energy and other organizations, Westinghouse is actively pursuing the development and commercialization of several coal-fueled processes. To protect the combustion turbine and environment from emissions generated during coal conversion (gasification/combustion) a gas cleanup system must be used. This paper reports on the status of fuel gas cleaning technology and describes the Westinghouse approach to developing an advanced hot gas cleaning system that contains component systems that remove particulate, sulfur, and alkali vapors. The basic process uses ceramic barrier filters for multiple cleaning functions.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):345-351. doi:10.1115/1.2906826.

In the search for a more efficient, less costly, and more environmentally responsible method for generating electrical power from coal, research and development has turned to advanced pressurized fluidized bed combustion (PFBC) and coal gasification technologies. A logical extension of this work is the second-generation PFBC plant, which incorporates key components of each of these technologies. In this new type of plant, coal is devolatilized/carbonized before it is injected into the PFB combustor bed, and the low-Btu fuel gas produced by this process is burned in a gas turbine topping combustor. By integrating coal carbonization with PFB coal/char combustion, gas turbine inlet temperatures higher than 1149°C (2100°F) can be achieved. The carbonizer, PFB combustor, and particulate-capturing hot gas cleanup systems operate at 871°C (1600°F), permitting sulfur capture by time-based sorbents and minimizing the release of coal contaminants to the gases. This paper presents the performance and economics of this new type of plant and provides a brief overview of the pilot plant test programs being conducted to support its development.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Gas Turbines: Aircraft

J. Eng. Gas Turbines Power. 1994;116(2):307-314. doi:10.1115/1.2906821.

One of the major activities of AGARD panels is to form working groups, which assemble experts who work on the particular subject for two or three years. As a result of the work, an advisory report is published, which compiles the state-of-the-art knowledge on the chosen specific topic. This paper explains the philosophy and procedures adopted during the formation of working groups of the Propulsion and Energetics Panel. Working groups concerning gas turbine technologies are presented. The selected working groups aim to improve the computational and experimental knowledge that would lead to the design of advanced aero gas turbine engines. Objective, scope, procedure, and important results of each working group will be explained. Working groups that were active during the 1980s and which were presently active are covered.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):315-321. doi:10.1115/1.2906822.

The early thinking leading to the American Turbojet engine is reviewed. This included ideas pertaining to ramjets and rockets, and culminated in the axial flow turbojet engine concept. The role of the NACA Subcommittee on Jet Propulsion under the leadership of Dr. W. F. Durand is stressed. Early problems with the new engine are mentioned, including flame tube light-off, interconnecting tubes, and fuel injection problems. An early major design innovation was the change to a single annular combustion chamber, replacing the 24 cans. This change culminated in the 19XB engine. The purposes of this paper are to show the magnitude of the problems encountered, and to give credit to the many dedicated persons who made the American Axial Flow Turbojet Engine a success.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):322-330. doi:10.1115/1.2906823.

The PT6 engine entered service in the mid-1960s. Since then, application of new technology has enabled low-cost development of engines approaching 1500 kW, the introduction of electronic controls, improved power-to-weight ratio, higher cycle temperature, and reduced specific fuel consumption. At the same time, PT6 field experience in business, commuter, helicopter, and trainer applications has resulted in engines with low Direct Operating Cost and a reputation for rugged design and a high standard of engine reliability. This paper will highlight some interesting examples of this technical evolution, including the development of electronic controls and the application of the latest three-dimensional aerodynamic and stress analysis to both compressor and turbine components.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Gas Turbines: Heat Transfer

J. Eng. Gas Turbines Power. 1994;116(2):395-401. doi:10.1115/1.2906833.

Increasing the thermal loading of bearing chambers in modern aero-engines requires advanced techniques for the determination of heat transfer characteristics. In the present study, film thickness and heat transfer measurements have been carried out for the complex two-phase oil/air flow in bearing chambers. In order to ensure real engine conditions, a new test facility has been built up, designed for rotational speeds up to n = 16,000 rpm and maximum flow temperatures of Tmax = 473 K. Sealing air and lubrication oil flow can be varied nearly in the whole range of aero-engine applications. Special interest is directed toward the development of an ultrasonic oil film thickness measuring technique, which can be used without any reaction on the flow inside the chamber. The determination of local heat transfer at the bearing chamber housing is based on a well-known temperature gradient method using surface temperature measurements and a finite element code to determine temperature distributions within the bearing chamber housing. The influence of high rotational speed on the local heat transfer and the oil film thickness is discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):402-405. doi:10.1115/1.2906834.

A first of its kind, induced draft (ID) heat recovery steam generators (HRSG) have been in service at a cogeneration facility since 1991. A preliminary engineering study considered a forced draft (FD) fan to supply combustion air to the HRSG duct burners (when the combustion turbine (CT) is out of service) as a traditional design; however, the study indicated that the FD fan may require the HRSG duct burner to be shut off following a CT trip and re-ignited after the FD fan was in service. Although the induced draft HRSG design cost more than the FD fan design, the induced draft design has improved the cogeneration facility’s steam generation reliability by enabling the HRSG to remain in service following a CT trip. This paper briefly summarizes the preliminary engineering study that supported the decision to select the ID fan design. The paper also discusses the control system that operates the fresh-air louvers, duct burners, HRSG, and ID fan during a CT trip. Startup and operating experiences are presented that demonstrate the effectiveness of the design. Lessons learned are also summarized for input into future induced draft HRSG designs.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):406-410. doi:10.1115/1.2906835.

Heat recovery heat exchangers with gas as one of the streams depend on the use of finned tubes to compensate for the inherently low gas heat transfer coefficient. Standard frequency welded “plain” fins were generally used in the past, until the high-frequency resistance welding technology permitted a cost-effective manufacture of “segmented” fins. The main advantage of this fin design (Fig. 1) is that it permits higher heat flux and hence smaller, lighter weight units for most operating conditions. While the criteria that dictate optimum design, such as compactness, weight, and cost per unit area favor the segmented fin design, a few other considerations such as fouling, ease of cleaning, and availability of dependable design methods have to be considered. This paper analyzes the performance parameters that affect the selection of either fin type.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Advanced Energy Systems

J. Eng. Gas Turbines Power. 1994;116(2):277-284. doi:10.1115/1.2906817.

This paper investigates a “basic” Chemically Recuperated Gas Turbine (a “basic” CRGT is defined here to be one without intercooling or reheat). The CRGT is of interest due to its potential for ultralow NOx emissions. A computer code has been developed to evaluate the performance characteristics (thermal efficiency and specific work) of the Basic CRGT, and to compare it to the steam-injected gas turbine (STIG), the combined cycle (CC) and the simple cycle gas turbine (SC) using consistent assumptions. The CRGT model includes a methane-steam reformer (MSR), which converts a methane-steam mixture into a hydrogen-rich fuel using the “waste” heat in the turbine exhaust. Models for the effects of turbine cooling air, variable specific heats, and the real gas effects of steam are included. The calculated results show that the Basic CRGT has a thermal efficiency higher than the STIG and simple cycles but not quite as high as the combined cycle.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):285-290. doi:10.1115/1.2906818.

The importance of the goal of developing systems that effectively use nonrenewable energy resources such as oil, natural gas, and coal is apparent. The method of exergy analysis is well suited for furthering this goal, for it enables the location, type and true magnitude of waste and loss to be determined. Such information can be used to design new systems and to reduce the inefficiency of existing systems. This paper provides a brief survey of both exergy principles and the current literature of exergy analysis with emphasis on areas of application.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):291-299. doi:10.1115/1.2906819.

In studies supported by the U.S. Department of Energy and the Electric Power Research Institute, several design configurations of Kellogg-Rust-Westinghouse (KRW)-based Integrated Gasification-Combined-Cycle (IGCC) power plants were developed. Two of these configurations are compared here from the exergetic viewpoint. The first design configuration (case 1) uses an air-blown KRW gasifier and hot gas cleanup while the second configuration (reference case) uses an oxygen-blown KRW gasifier and cold gas cleanup. Each case uses two General Electric MS7001F advanced combustion turbines. The exergetic comparison identifies the causes of performance difference between the two cases: differences in the exergy destruction of the gasification system, the gas turbine system, and the gas cooling process, as well as differences in the exergy loss accompanying the solids to disposal stream. The potential for using (a) oxygen-blown versus air-blown-KRW gasifiers, and (b) hot gas versus cold gas cleanup processes was evaluated. The results indicate that, among the available options, an oxygen-blown KRW gasifier using in-bed desulfurization combined with an optimized hot gas cleanup process has the largest potential for providing performance improvements.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):300-306. doi:10.1115/1.2906820.

In a study supported by the U. S. Department of Energy, several design configurations of Kellogg-Rust-Westinghouse (KRW)-based Integrated Gasification-Combined-Cycle (IGCC) power plants were developed. One of these configurations was analyzed from the exergoeconomic (thermoeconomic) viewpoint. This design configuration uses an air-blown KRW gasifier, hot gas cleanup, and two General Electric MS7001F advanced combustion turbines. Operation at three different gasification temperatures was considered. The detailed exergoeconomic evaluation identified several changes for improving the cost effectiveness of this IGCC design configuration. These changes include the following: decreasing the gasifier operating temperature, enhancing the high-pressure steam generation in the gasification island, improving the efficiency of the steam cycle, and redesigning the entire heat exchanger network. Based on the cost information supplied by the M. W. Kellogg Company, an attempt was made to calculate the economically optimal exergetic efficiency for some of the most important plant components.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Gas Turbines: Control and Diagnostics

J. Eng. Gas Turbines Power. 1994;116(2):366-373. doi:10.1115/1.2906829.

Manufacturers of gas turbines have searched for three decades for a reliable way to use gas path measurements to determine the health of jet engine components. They have been hindered in this pursuit by the quality of the measurements used to carry out the analysis. Engine manufacturers have chosen weighted-least-squares techniques to reduce the inaccuracy caused by sensor error. While these algorithms are clearly an improvement over the previous generation of gas path analysis programs, they still fail in many situations. This paper describes some of the failures and explores their relationship to the underlying analysis technique. It also describes difficulties in implementing a gas path analysis program. The paper concludes with an appraisal of weighted-least-squares-based gas path analysis.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):374-380. doi:10.1115/1.2906830.

Reliable methods for diagnosing faults and detecting degraded performance in gas turbine engines are continually being sought. In this paper, a model-based technique is applied to the problem of detecting degraded performance in a military turbofan engine from take-off acceleration-type transients. In the past, difficulty has been experienced in isolating the effects of some of the physical processes involved. One such effect is the influence of the bulk metal temperature on the measured engine parameters during large power excursions. It will be shown that the model-based technique provides a simple and convenient way of separating this effect from the faster dynamic components. The important conclusion from this work is that good fault coverage can be gleaned from the resultant pseudo-steady-state gain estimates derived in this way.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Gas Turbines: Electric Utilities

J. Eng. Gas Turbines Power. 1994;116(2):381-388. doi:10.1115/1.2906831.

Gas turbine performance is the result of choices of type of cycle, cycle temperature ratio, pressure ratio, cooling flows, and component losses. The output is usually given as efficiency (thermal, propulsive, specific thrust, overall efficiency) versus specific power. This paper presents a set of computer programs for the performance prediction of shaft-power and jet-propulsion cycles: simple, regenerative, intercooled-regenerative, turbojet, and turbofan. Each cycle is constructed using individual component modules. Realistic assumptions are specified for component efficiencies as functions of pressure ratio, cooling mass-flow rate as a function of cooling technology levels, and various other cycle losses. The programs can be used to predict design point and off-design point operation using appropriate component efficiencies. The effects of various cycle choices on overall performance are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):389-394. doi:10.1115/1.2906832.

The 701F is a high-temperature 50 Hz industrial grade 220 MW size engine based on a scaling of the 501F 150 MW class 60 Hz machine, and incorporates a higher compressor pressure ratio to increase the thermal efficiency. The prototype engine is under a two-year performance and reliability verification testing program at MHI’s Yokohama Plant and was initially fired in June of 1992. This paper describes the 701F design features design changes made from 501F. The associated performance and reliability verification test program will also be presented.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Gas Turbines: Industrial

J. Eng. Gas Turbines Power. 1994;116(2):352-359. doi:10.1115/1.2906827.

A number of materials issues related to the design of piping and support components in high-temperature fluidized bed combustor systems were examined. These issues included the availability of long-time design data on structural materials, the general character of the creep and stress rupture behavior, the performance of weldments, and the assessment of damage accumulation. Emphasis was placed on alloy 800H, but several other alloys were briefly examined for use at temperatures above 816°C (1500°F). It was concluded that the character of the creep curve ranged significantly with chemistry, processing variables, and environment, and that the specification of design allowable stresses and life estimation techniques must be approached with caution for service above 816°C (1500°F).

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):360-365. doi:10.1115/1.2906828.

Gas turbine air cooling systems serve to raise performance to peak power levels during the hot months when high atmospheric temperatures cause reductions in net power output. This work describes the technical and economic advantages of providing a compressor inlet air cooling system to increase the gas turbine’s power rating and reduce its heat rate. The pros and cons of state-of-the-art cooling technologies, i.e., absorption and compression refrigeration, with and without thermal energy storage, were examined in order to select the most suitable cooling solution. Heavy-duty gas turbine cogeneration systems with and without absorption units were modeled, as well as various industrial sectors, i.e., paper and pulp, pharmaceuticals, food processing, textiles, tanning, and building materials. The ambient temperature variations were modeled so the effects of climate could be accounted for in the simulation. The results validated the advantages of gas turbine cogeneration with absorption air cooling as compared to other systems without air cooling.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Gas Turbines: Marine

J. Eng. Gas Turbines Power. 1994;116(2):411-417. doi:10.1115/1.2906836.

The LV100 gas turbine engine is being developed for U.S. Army ground vehicle use. A unique approach for controls and accessories is being used whereby the engine has no accessory gearbox. Instead a high-speed starter/generator is mounted directly on the compressor shaft and powers all engine accessories as well as supplies the basic electrical power needs of the vehicle. This paper discusses the evolution of the electrically driven LV100 accessory system starting with the Advanced Integrated Propulsion System (AIPS) demonstrator program, through the current system to future possibilities with electric vehicle propulsion. Issues in electrical vehicle propulsion are discussed including machine type, electrical power type, and operation with a gas turbine.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):418-423. doi:10.1115/1.2906837.

Regenerative and intercooled-regenerative gas turbine engines with low pressure ratio have significant efficiency advantages over traditional aero-derivative engines of higher pressure ratios, and can compete with modern diesel engines for marine propulsion. Their performance is extremely sensitive to thermodynamic-cycle parameter choices and the type of components. The performances of two 1.12 MW (1500 hp) regenerative gas turbines are predicted with computer simulations. One engine has a single-shaft configuration, and the other has a gas-generator/power-turbine combination. The latter arrangement is essential for wide off-design operating regime. The performance of each engine driving fixed-pitch and controllable-pitch propellers, or an AC electric bus (for electric-motor-driven propellers) is investigated. For commercial applications the controllable-pitch propeller may have efficiency advantages (depending on engine type and shaft arrangements). For military applications the electric drive provides better operational flexibility.

Commentary by Dr. Valentin Fuster
Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):428-433. doi:10.1115/1.2906839.

Over the last three decades, aeroderivative gas turbines have become established naval ship propulsion engines, but use in the commercial marine field has been more limited. Today, aeroderivative gas turbines are being increasingly utilized as commercial marine engines. The primary reason for the increased use of gas turbines is discussed and several recent GE aeroderivative gas turbine commercial marine applications are described with particular aspects of the gas turbine engine installations detailed. Finally, the potential for future commercial marine aeroderivative gas turbine applications is presented.

Commentary by Dr. Valentin Fuster

RESEARCH PAPERS: Power

J. Eng. Gas Turbines Power. 1994;116(2):434-441. doi:10.1115/1.2906840.

A method is developed to determine the shell and tube side heat transfer performance of a feedwater heater with a short drain cooler. The desuperheating, condensing, and drain cooling zones are discussed and analyzed by deriving a modified version of the Delaware Method of Shell-Side Design.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1994;116(2):442-451. doi:10.1115/1.2906841.

This paper deals with an issue of paramount importance for the turbine manufacturer today: the mathematical modeling of erosive wear at the inlet rotor blade edges by streams of coarsely dispersed liquid droplets. In the methodology of blade material wear an important element is the erosion model or material response Y = Y (τ) to the droplet impact intensity. On the background of this erosion model development the approaches of Szprengiel and Weigle (1983), Szprengiel (1985), and Shubenko and Kovalsky (1987) are presented and applied for erosion calculation of some real turbine blade profiles. There are, however, several factors that affect the erosion prediction quality as well as the field experimental data. Hence a procedure for verifying the methodology of the erosion prediction by experimental data is necessary. Krzyzanowski (1987, 1988, 1991) used for that purpose the calculated and measured erodet area of various turbine blade profiles. Here the comparison of the calculated and measured erosion width ηB ≡ z has been used to verify the prediction methodology of erosion. The use of ηB instead of erosion area looked promising since acquiring ηB experimental values seemed easier than any other geometric characteristics of the blade erosion wear. It has been shown, however, that the prediction of ηB underestimates the blade erosion wear for both material response models. To cope with the scatter of experimental data, statistics have been used. Reasons for this scatter and differences between the calculated (ηBcalc ) and measured (ηBm ) values of the erosion field width have been suggested. The list of factors that affect the erosion prediction quality may be looked upon as a list of promising topics of further research on the subject.

Commentary by Dr. Valentin Fuster

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