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IN THIS ISSUE


RESEARCH PAPERS

J. Eng. Gas Turbines Power. 1992;114(4):603-611. doi:10.1115/1.2906633.

The use of a rational efficiency for a power plant (the work output divided by the maximum possible reversible work output) is well established for conventional and combined plants. However, there are in the literature several proposals for “second-law” efficiencies of power plant components and no universally agreed practice. The paper discusses these various proposals and recommends particular definitions for the efficiency of components. These definitions are consistent with the universally agreed definition for overall plant rational efficiency. The approach is illustrated by a numerical example.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):612-620. doi:10.1115/1.2906634.

The modern pulverized-coal power plant is the product of continuous design experience and component improvement in the 20th century. In recent years, studies of the effect of high temperatures on turbine materials have led to major worldwide research and development programs on improving the thermal cycle by raising turbine-inlet pressure and temperature. This paper reviews the importance of various parameters in trying to optimize a turbine cycle designed for advanced steam conditions. Combinations of throttle pressure (between 3500 psi [24.1 MPa] and 10,000 psi [70MPa]), throttle and reheat temperature(1000°F [538°C] to 1400°F [760°C]), and number of reheats are explored to establish a realistic turbine cycle design. Assessments and trade-offs are discussed, as applicable. Critical cycle components, feedwater cycle arrangements, and reheat pressure selections are analyzed in establishing an optimized steam turbine-boiler cycle for a 1000 MW turbine-generator. Applicability of results to smaller advanced steam turbines is given. A brief update on the high-temperature Wakamatsu turbine project in Japan is also given.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):621-631. doi:10.1115/1.2906635.

The reaction of water-cooled and wet-surface air-cooled condensers to a bypass of the steam turbine is analyzed by the introduction of an indicant. Gas dynamics considerations for designing the breakdown of the steam pressure are included. SI metric units are compared with gravitational metric units in order to clarify the fundamental difference between these two systems of measure. Conditioning the steam before admission to the condenser involves desuperheating, which is analyzed on the basis of a heat balance.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):632-642. doi:10.1115/1.2906636.

In the use of wet cooling towers, drift refers to small droplets of circulating water that are carried out of the cooling tower by the saturated exhaust air. Inertial impaction separators, known as drift eliminators, are used to strip the water droplets from the exhaust air. To achieve peak cooling tower operating efficiency, it is desirable that losses in fan system performance due to the drift eliminators be minimized. Therefore, an experimental program was developed and executed to evaluate the effect of drift eliminator design on cooling tower fan system performance. Flow visualization studies were used to gain insight into the flow patterns within the cooling tower plenum as influenced by drift eliminator design. A fully instrumented fan test cell was used to investigate the effects upon fan system performance resulting from two different styles of drift eliminators. The effect of drift eliminator discharge angle upon fan system total efficiency was investigated and the optimal discharge angle determined.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):643-652. doi:10.1115/1.2906637.

As utilities plan for load growth in the 1990s, they are faced with the difficulty of choosing the most economic generation while subject to a number of challenging constraints. These constraints include environmental regulations, particularly the new Clean Air Act, risk aversion, fuel availability and costs, etc. One of the options open to many utilities with existing steam units is repowering, which involves the installation of gas turbine(s) and heat recovery steam generator(s) (HRSG) to convert the steam plant to combined-cycle operation. This paper takes an overall look at the application considerations involved in the use of this generating option, beginning with a summary of the size ranges of existing steam turbines that can be repowered using the GE gas turbine product line. Other topics covered include performance estimates for repowered cycles, current emissions capabilities of GE gas turbines, approximate space requirements and repowering economics.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):653-659. doi:10.1115/1.2906638.

Unfired combined cycles achieve superior efficiencies at low emission levels. The potential and efficiency limits are investigated and the possibilities for enhancing efficiency are described. It is demonstrated that limited supplementary firing of the heat recovery steam generator can be an interesting alternative and that this allows efficiency and plant size to be increased. The effects of supplementary firing on NOx emissions are also shown.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):660-664. doi:10.1115/1.2906639.

Commercial IGCC power plants need gas turbines with high efficiency and high power output in order to reduce specific installation costs and fuel consumption. Therefore the well-proven 154 MW V94.2 and the new 211 MW V94.3 high-temperature gas turbines are well suited for this kind of application. A high degree of integration of the gas turbine, steam turbine, oxygen production, gasifier, and raw gas heat recovery improves the cycle efficiency. The air use for oxygen production is taken from the gas turbine compressor. The N2 fraction is recompressed and mixed with the cleaned gas prior to combustion. Both features require modifications of the gas turbine casing and the burners. Newly designed burners using the coal gas with its very low heating value and a mixture of natural gas and steam as a second fuel are developed for low NOx and CO emissions. These special design features are described and burner test results presented.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):665-675. doi:10.1115/1.2906640.

Increasing atmospheric carbon dioxide from fossil fuel combustion is raising new interest in using renewable biomass for energy. Modest-scale cogeneration systems using air-blown gasifiers coupled to aeroderivative gas turbines are expected to have high efficiencies and low unit capital costs, making them well-suited for use with biomass. Biomass-gasifier/gas turbine (BIG/GT) technology is not commercial, but efforts aimed at near-term commercialization are ongoing worldwide. Estimated performance and cost and prospects for commercial development of two BIG/GT systems are described, one using solid biomass fuel (e.g., wood chips), the other using kraft black liquor. At an energy-efficient kraft pulp mill, a BIG/GT cogeneration system could produce over three times as much electricity as is typically produced today. The mill’s on-site energy needs could be met and a large surplus of electricity would be available for export. Using in addition currently unutilized forest residues for fuel, electricity production would be nearly five times today’s level. The total cost to produce the electricity in excess of on-site needs is estimated to be below 4 cents per kWh in most cases. At projected growth rates for kraft pulp production, the associated biomass residue fuels could support up to 100 GW of BIG/GT capacity at kraft pulp mills worldwide in 2020 (30 GW in the US). The excess electricity production worldwide in 2020 would be equivalent to 10 percent of today’s electricity production from fossil fuels.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):676-681. doi:10.1115/1.2906641.

The V64.3 60-MW combustion turbine is the first of a new generation of high-temperature gas turbines, designed for 50 and 60 Hz simple cycle, combined cycle, and cogeneration applications. The prototype engine was tested in 1990 in the Berlin factories under the full range of operation conditions. It was equipped with various measurement systems to monitor pressures, gas and metal temperatures, clearances, strains, vibrations, and exhaust emissions. The paper describes the engine design, the test facility and instrumentation, and the engine performance. Results are given for turbine blade temperatures, compressor and turbine vibrations, exhaust gas temperature, and NOx emissions for combustion of natural gas and fuel oil.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):682-686. doi:10.1115/1.2906642.

The injection of exhaust-heat-generated steam into gas turbines for power augmentation has been proven to provide exceptional flexibility of operation in cogeneration applications. The chronology of development of this technology is presented, including a list of available turbines. A description is then given of the design process for converting existing gas turbines to steam injection. Finally, the water purification issue, which is perceived by some as a barrier to cost-effective implementation of such installations, is addressed. It is shown that water purification cost is of the order of 5 percent of the fuel cost and is therefore not a decisive factor.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):687-694. doi:10.1115/1.2906643.

The effect of heat storage on a cogeneration plant is investigated using a mathematical programming approach. For a diesel engine plant, an optimal planning method is presented by which the operational policy of constituent equipment is determined together with the charging history of a heat storage tank so as to minimize the daily operational cost. An algorithm is designed to solve this optimization problem efficiently by combining the dynamic programming method with the mixed-integer programming one. Through a case study, it is made clear how the volume of the heat storage tank influences the daily operational policy and the long-term economy of the total plant.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):695-700. doi:10.1115/1.2906644.
Abstract
Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):701-706. doi:10.1115/1.2906645.

The use of a binary mixture as a working fluid in bottoming cycles has in recent years been recognized as a means of improving combined cycle efficiency. There is, however, quite a number of studies dealing with components of plants that employ fluids other than water, and particularly binary mixtures. Due to different specific volume, viscosity, thermal conductivity, and Prandtl number, heat recovery boilers designed to work with water require certain modifications before they can be used with binary mixtures. Since a binary mixture is able to recover more heat from the exhaust fumes than water, the temperature difference between the hot and the cold fluids is generally lower over the whole recovery boiler; this necessitates greater care in sizing the tube bundles in order to avoid an excessive heat transfer surface per unit of thermal power exchanged. The aim of this paper is to provide some general criteria for the design of a heat recovery boiler for a binary mixture, by showing the influence of various dimensional parameters on the heat surface and pressure drop both in the cold and the hot side. Heat transfer coefficients and pressure drops in the hot side were computed by means of correlations found in the literature. A particular application was studied for an ammonia-water mixture, used in the Kalina cycles, which represents one of the most interesting binary cycles proposed so far.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):707-714. doi:10.1115/1.2906646.

Methods developed for optimization of thermal systems usually work on a predetermined configuration of the system. Consequently, in order to select the best system, it is necessary to apply the method separately for each possible configuration and compare the results. The designer’s work would be significantly facilitated, if the optimization method could synthesize the optimal configuration of the system automatically. Such a method is presented here, based on the Thermoeconomic Functional Approach (TFA). TFA is a method developed for optimal design or improvement of complex thermal systems. It combines thermodynamic concepts with economic considerations in a systems approach. A thermal system is considered as a set of interrelated units; each unit has one particular function (purpose, or product). The documented determination of the function of the system as a whole and of each unit individually is achieved by functional analysis. The problem is mathematically formulated (objective function, constraints) at two levels: (A) optimization of operation, (B) optimization of the configuration and the design of the system. The solution is obtained by a two-level algorithm. As an example, the method is used to optimize a cogeneration system supplying a process plant with heat and electricity, which are known functions of time.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):715-720. doi:10.1115/1.2906647.

Magnetic heat pumps have been successfully used for refrigeration applications at near absolute-zero-degree temperatures. In these applications, a temperature lift of a few degrees in a cryogenic environment is sufficient and can be easily achieved by a simple magnetic heat-pump cycle. To extend magnetic heat pumping to other temperature ranges and other types of application in which the temperature lift is more than just a few degrees requires more involved cycle processes. The possible cycle applications include cooling of superconducting transmission lines, space conditioning, and industrial heating. This paper investigates the characteristics of a few better-known thermomagnetic heat-pump cycles (Carnot, Ericsson, Stirling, and regenerative) in extended ranges of temperature lift. The regenerative cycle is the most efficient one. Cycle analyses were done for gadolinium operating between 0 and 7 Tesla, and with a heat-rejection temperature of 320 K. The analysis results predicted a 42 percent reduction in coefficient of performance at 260 K cooling temperature and a 15 percent reduction in capacity at 232 K cooling temperature for the magnetic Ericsson cycle as compared with the ideal regenerative cycle. Such substantial penalties indicate that the potential irreversibilities from this one source may adversely affect the viability of certain proposed MHP concepts if the relevant loss mechanisms are not adequately addressed.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):721-726. doi:10.1115/1.2906648.

Future space power requirements will vary from the subkilowatt range for deep space probes, to the hundreds of kilowatts range for a lunar base, to the multimegawatt range for interplanetary propulsion systems. Closed Brayton cycle (CBC) power conversion has the flexibility to be used in all these power ranges and with a variety of heat source options such as isotope, solar, and nuclear. Each of these types of heat sources has different characteristics that make it more appropriate for particular mission profiles and power output ranges. Heat source characteristics can also be major design drivers in the closed Brayton cycle design optimization process. This paper explores heat source selection and the resulting CBC system designs, and discusses optimization methods as a function of the main design drivers. Such power system requirements as power level, man-rated radiation shielding, fuel costs, eclipse/darkness duration, system mass, radiator area, reliability/mission duration, and insolation level are evaluated through several CBC parametric case studies. These cases include: (1) a 500 We power system for deep space probes; (2) a 50 kWe solar dynamic system for earth orbit and other applications; (3) a 100 kWe man-rated lunar/Mars stationary /rover power system; (4) a 200 to 825 kWe power system for the lunar outpost; and (5) 3300 kWe modules for interplanetary propulsions.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):727-736. doi:10.1115/1.2906649.

This paper presents design stage methods to analyze centrifugal compressor station piping acoustically. The methods have been successfully applied to the design of 26 stations since 1988. Full details of the calculation procedures are given, as well as guidelines for interpreting predicted results. Finally, the relationships between acoustic and mechanical response are described.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):737-739. doi:10.1115/1.2906650.

For the conveyance and storage of natural gas, compressor stations are required where the installed power output varies mostly between 1 MW and 20 MW. The noise control measures involved to meet the environmental noise emission regulations in Europe will be presented. The most economical noise control techniques are described particularly for the intake and exhaust systems of gas turbines, the housing of such engines, and peripheral sound sources like gas coolers, oil coolers, and aboveground piping.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):740-748. doi:10.1115/1.2906651.

Stringent environmental constraints are usually associated with or applied to the siting and installation of new pipeline facilities. This has resulted in the dedication of a significant portion of the design effort and ultimate cost of the facility to the mitigation of these environmental concerns. This paper describes how a compressor station can be designed and built such that stringent silencing requirements can be satisfied. The paper also references specific aspects of design that were successfully applied to the Parkway Compressor Station, Canada.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):749-754. doi:10.1115/1.2906652.

The paper describes a conceptual control system design based on advanced technologies currently in the exploratory development phase, and, in some cases, emerging into the advanced development phase. It explores future propulsion control systems that focus on improvements in three areas: (1) significantly reducing control system weight; (2) enhancing engine performance (thrust, sfc, etc.); and (3) improving control system reliability and tolerance to high-threat environments (temperature, vibration, EMI, EMP, etc.). The factors that will influence the design and hardware configuration of future propulsion control systems are described. Design goals for future systems, based on the DOD/NASA IHPTET Initiative, and projections of emerging technology capability (and availability) form the basis for future propulsion control system design requirements and for estimating future hardware configurations.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):755-762. doi:10.1115/1.2906653.

The Pratt & Whitney and Northrop companies together, under the Air Force Wright Research and Development Center (WRDC) sponsored Integrated Reliable Fault-Tolerant Control for Large Engines (INTERFACE II) Program [1, 2], designed and demonstrated an advanced real-time Integrated Flight and Propulsion Control (IFPC) system. This IFPC system was based upon the development of physically distinctive, functionally integrated, flight and propulsion controls that managed the Northrop twin engine, statically unstable, P700 airplane. Digital flight control and digital engine control hardware were combined with cockpit control hardware and computer simulations of the airplane and engines to provide a real-time, closed-loop, piloted IFPC system. As part of a follow-on effort, lessons learned during the INTERFACE II program are being applied to the design of a flight critical propulsion control system. This paper will present both the results of the INTERFACE II IFPC program and approaches toward definition and development of an integrated propulsion control system for flight critical applications.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):763-767. doi:10.1115/1.2906654.

An analog fuel control for a gas turbine engine was compared with several state-space derived fuel controls. A single-spool, simple cycle gas turbine engine was modeled using ACSL (high level simulation language based on FORTRAN). The model included an analog fuel control representative of existing commercial fuel controls. The ACSL model was stripped of nonessential states to produce an eight-state linear state-space model of the engine. The A, B, and C matrices, derived from rated operating conditions, were used to obtain feedback control gains by the following methods: (1) state feedback; (2) LQR theory; (3) Bellman method; and (4) polygonal search. An off-load transient followed by an on-load transient was run for each of these fuel controls. The transient curves obtained were used to compare the state-space fuel controls with the analog fuel control. The state-space fuel controls did better than the analog control.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):768-775. doi:10.1115/1.2906655.

The flow fields for swirlers with and without a shroud were measured using a twocomponent laser-Doppler velocimeter (LDV) system. The primary goal of this study is to investigate the effect of shrouds on swirler flow fields, in order to provide useful design information for the manufacture of gas turbine fuel nozzles, and to supply benchmark data for comparison with numerical predictions. As a result of the measurements, the radial distributions of three mean velocity components, turbulence intensity, and shear stresses were obtained at five locations (x/d = 0.1, 1, 2, 4, and 8) along the axis of the swirlers. The LDV system was operated in the 20 deg off-axis forward scatter mode with beam expanders and Bragg cell frequency shifting on both components. The flow was seeded by 1 μm mean diameter atomized particles of glycerol and water (50/50) mixture. Comparison of flow with and without the shroud showed that the jet diameter was much smaller, and the flow deceleration in the downstream direction was faster, due to the influence of the shroud, at the same supply pressure (750 mm H2 O). As a result of the significant reduction in the swirl number due to the addition of the shroud, the recirculation zone disappeared. In addition to its influence on recirculation, the shroud caused a radially inward shift of the maximum mean and turbulence parameters at all axial locations. The anisotropy of turbulence increased as compared to the values for the swirler without the shroud.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):776-782. doi:10.1115/1.2906656.

Weak extinction data obtained from an experimental apparatus designed to simulate the characteristics of practical afterburner combustion systems are presented. The apparatus supplies mixtures of varied composition (equivalence ratio and degree of vitiation), temperature and velocity to Vee-gutter flame holders of various widths and shapes similar to those found in jet engine systems. The fuel employed is a liquid hydrocarbon whose chemical composition and physical properties correspond to those of aviation kerosine, JP5. An equation for predicting weak extinction limits which accounts for upstream vitiation and the chemical characteristics of the fuel is derived from stirred reactor theory. The correlation between the predictions and experimental results indicates that the stirred reactor approach can provide a framework for predicting the lean blowout limits of practical flameholders over wide ranges of engine operating conditions.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):783-789. doi:10.1115/1.2906657.

Detailed information on the influence of geometric and flow parameters on the structure and properties of recirculation zone in confined combusting flows is not available. In this paper, recirculation zone structure and turbulence properties of methane-air mixtures downstream of several conical flameholders were measured using LDA. These tests employed different blockage ratios (13 and 25 percent), cone angles (30, 45, 60, and 90 deg), equivalence ratios (0.56, 0.65, 0.8, and 0.9), mean annular velocities (10, 15, and 20 m/s), and approach turbulence levels (2, 17, and 22 percent). It was found that increasing the blockage ratio and cone angle affected the recirculation zone size and shape only slightly. Also, these parameters increased the shear stress and turbulent kinetic energy (TKE) moderately. Increasing the equivalence ratio or approach turbulence intensity produced a recirculation zone shape very similar to that found in the cold flow. TKE decreased due to turbulent dilatation produced by increased heat release. These observations are discussed from the viewpoint of their importance to practical design and combustion modeling.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):790-796. doi:10.1115/1.2906658.

A method for aerothermodynamic preliminary design of a wave engine is presented. The engine has a centrifugal precompressor for the wave rotor, which feeds high and low-pressure turbines. Three specific wave engine designs are presented. Wave rotor blades are naturally cooled by the ingested air; thus combustion temperatures can be as high as 1900 K. Engine pressure ratios of over 25 are obtained in compact designs. It is shown that placing no nozzles at the end of the rotor blade passages yields the highest cycle efficiencies, which can be over 50 percent. Rotor blades are straight and easily milled, cast, or fabricated.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):797-801. doi:10.1115/1.2906659.

Advanced technology now being demonstrated in the test cell will provide growth in existing engine ratings in the near term and substantially improve new technology engines early in the twenty-first century. The benefits these advancements provide, to the engines, to the salient characteristics important to users and designers, and to the vehicles they will power, are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):802-808. doi:10.1115/1.2906660.

Future aircraft engine development may lead to Advanced Ducted Engines (ADE), which have a bypass ratio significantly higher than present turbofans. The increases in bypass ratio will dictate larger diameter nacelles and an increasing importance of the nacelle aerodynamics and wing integration aerodynamics. A series of isolated wind tunnel tests was therefore designed and conducted by PWA and MTU to investigate inlet, nozzle, and reverser aerodynamics. Additional installed testing was done in cooperation with MBB and BAe. Key features of the tests are noted and significant results are discussed.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):809-815. doi:10.1115/1.2906661.

A twin-engine, low-wing transport model, with a supercritical wing designed for a cruise Mach number of0.77 and a lift coefficient of 0.55, was tested in the 16-Foot Transonic Tunnel at NASA Langley Research Center. The purpose of this test was to compare the wing/nacelle interference effects of superfans (very high bypass ratio turbofans, BPR ≈ 18) with the interference effects of advanced turbofans (BPR ≈ 6). Flow-through nacelles were used in this study. Forces and moments on the complete model were measured using a strain gage balance and extensive surface static pressure measuements (383 orifice locations) were made on the model’s wing, nacelles, and pylons. Data were taken at Mach numbers from 0.50 to 0.80 and model angle-of-attack was varied from −4 to +8 deg. Results of the investigation indicate that superfan nacelles can be installed with approximately the same drag penalty as conventional turbofan nacelles.

Commentary by Dr. Valentin Fuster
J. Eng. Gas Turbines Power. 1992;114(4):816-828. doi:10.1115/1.2906662.

The origin of dynamic pressure loads on external divergent engine nozzle flaps of the B-1B aircraft was investigated in the NASA/LaRC 16-ft transonic tunnel using a 6 percent full-span model with powered engine nacelles. External flap dynamic loads and afterbody drag associated with flap removal were measured using this model. Both dry and maximum A/B power nozzles were evaluated in this study. As a result of this study, the principle mechanisms responsible for high dynamic external flap loads were determined along with performance penalty associated with flap removal.

Commentary by Dr. Valentin Fuster

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