bluuebunny/crossref_metadata_2025 huggingface dataset:
An Assessment of the Thermodynamic Performance of Mixed Gas–Steam Cycles: Part A—Intercooled and Steam-Injected Cycles
Authors: Macchi E. , Consonni S. , Lozza G. , Chiesa P.
Published: February 2008

This paper discusses the thermodynamics of power cycles where steam or water are mixed with air (or combustion gases) to improve the performance of stationary gas turbine cycles fired on clean fuels. In particular, we consider cycles based on modified versions of modern, high-performance, high-efficiency aeroderivative engines. The paper is divided into two parts. After a brief description of the calculation method, in Part A we review the implications of intercooling and analyze cycles with steam injection (STIG and ISTIG). In Part B we examine cycles with water injection (RWI and HAT). Due to lower coolant temperatures, intercooling enables us to reduce turbine cooling flows and/or to increase the turbine inlet temperature. Results show that this can provide significant power and efficiency improvements for both simple cycle and combined cycle systems based on aero-engines; systems based on heavy-duty machines also experience power output augmentation, but almost no efficiency improvement. Mainly due to the irreversibilities of steam/air mixing, intercooled steam injected cycles cannot achieve efficiencies beyond the 52–53 percent range even at turbine inlet temperatures of 1500°C. On the other hand, by accomplishing more reversible water–air mixing, the cycles analyzed in Part B can reach efficiencies comparable (RWI cycles) or even superior (HAT cycles) to those of conventional “unmixed” combined cycles.
Advantages of Air Conditioning and Supercharging an LM6000 Gas Turbine Inlet
Authors: Kolp D. A. , Flye W. M. , Guidotti H. A.
Published: February 2008

Of all the external factors affecting a gas turbine, inlet pressure and temperature have the greatest impact on performance. The effect of inlet temperature variations is especially pronounced in the new generation of high-efficiency gas turbines typified by the 40 MW GE LM6000. A reduction of 50°F (28°C) in inlet temperature can result in a 30 percent increase in power and a 4.5 percent improvement in heat rate. An elevation increase to 5000 ft (1524 m) above sea level decreases turbine output 17 percent; conversely supercharging can increase output more than 20 percent. This paper addresses various means of heating, cooling and supercharging LM6000 inlet air. An economic model is developed and sample cases are cited to illustrate the optimization of gas turbine inlet systems, taking into account site conditions, incremental equipment cost and subsequent performance enhancement.
Combined Power Plants—Past, Present, and Future
Authors: Horlock J. H.
Published: February 2008

The early history of combined power plants is described, together with the birth of the CCGT plant (the combined “cycle” gas turbine). Sustained CCGT development in the 1970s and 1980s, based on sound thermodynamic considerations, is outlined. Finally more recent developments and future prospects for the combined gas turbine/steam turbine combined plant are discussed.
The Role of Fuel Preparation in Low-Emission Combustion
Authors: Lefebvre A. H.
Published: February 2008

The attainment of very low pollutant emissions, in particular oxides of nitrogen (NOx), from gas turbines is not only of considerable environmental concern but has also become an area of increasing competitiveness between the different engine manufacturers. For stationary engines, the attainment of ultralow NOx has become the foremost marketing issue. This paper is devoted primarily to current and emerging technologies in the development of ultralow emissions combustors for application to aircraft and stationary engines. Short descriptions of the basic design features of conventional gas turbine combustors and the methods of fuel injection now in widespread use are followed by a review of fuel spray characteristics and recent developments in the measurement and modeling of these characteristics. The main gas-turbine-generated pollutants and their mechanisms of formation are described, along with related environmental risks and various issues concerning emissions regulations and recently enacted legislation for limiting the pollutant levels emitted by both aircraft and stationary engines. The impacts of these emissions regulations on combustor and engine design are discussed first in relation to conventional combustors and then in the context of variable-geometry and staged combustors. Both these concepts are founded on emissions reduction by control of flame temperature. Basic approaches to the design of “dry” low-NOx and ultralow-NOx combustors are reviewed. At the present time lean, premix, prevaporize combustion appears to be the only technology available for achieving ultralow NOx emissions from practical combustors. This concept is discussed in some detail, along with its inherent problems of autoignition, flashback, and acoustic resonance. Attention is also given to alternative methods of achieving ultralow NOx emissions, notably the rich-burn, quick-quench, lean-burn, and catalytic combustors. These concepts are now being actively developed, despite the formidable problems they present in terms of mixing and durability. The final section reviews the various correlations now being used to predict the exhaust gas concentrations of the main gaseous pollutant emissions from gas turbine engines. Comprehensive numerical methods have not yet completely displaced these semi-empirical correlations but are nevertheless providing useful insight into the interactions of swirling and recirculating flows with fuel sprays, as well as guidance to the combustion engineer during the design and development stages. Throughout the paper emphasis is placed on the important and sometimes pivotal role played by the fuel preparation process in the reduction of pollutant emissions from gas turbines.
Detailed Measurements on a Modern Combustor Dump Diffuser System
Authors: Carrotte J. F. , Bailey D. W. , Frodsham C. W.
Published: February 2008

An experimental investigation has been carried out to determine the flow characteristics and aerodynamic performance of a modern gas turbine combustor dump diffuser. The system comprised a straight walled prediffuser, of area ratio 1.35, which projected into a dump cavity where the flow divided to pass either into the flame tube or surrounding feed annuli. In addition, a limited amount of air was removed to simulate flow used for turbine cooling. The flame tube was relatively deep, having a radial depth 5.5 times that of the passage height at prediffuser inlet, and incorporated burner feed arms, cowl head porosity, cooling rings, and primary ports. Representative inlet conditions to the diffuser system were generated by a single-stage axial flow compressor. Results are presented for the datum configuration, and for a further three geometries in which the distance between prediffuser exit and the head of the flame tube (i.e., dump gap) was reduced. Relatively high values of stagnation pressure loss were indicated, with further significant increases occurring at smaller dump gaps. These high losses, which suggest a correlation with other published data, are due to the relatively deep flame tube and short diffuser length. Furthermore, the results also focus attention on how the presence of a small degree of diffuser inlet swirl, typical of that which may be found within a gas turbine engine, can result in large swirl angles being generated farther downstream around the flame tube. This is particularly true for flow passing to the inner annulus.
Flow Field and Performance Characteristics of Combustor Diffusers: A Basic Study
Authors: Hestermann R. , Kim S. , Ben Khaled A. , Wittig S.
Published: February 2008

Results of a detailed study concerning the influence of geometric as well as fluid mechanic parameters on the performance of a plane model combustor diffuser in cold flow are presented. For a qualitative insight into the complex flow field inside the prediffuser, the sudden expansion region, and the flow field around the flame tube dome, results of a flow visualization study with the hydrogen bubble method as well as with the ink jet method are presented for different opening angles of the prediffuser and for different flame tube distances. Also, quantitative data from detailed measurements with LDV and conventional pressure probes in a geometrically similar air-driven setup are presented. These data clearly demonstrate the effect of boundary layer thickness as well as the influence of different turbulence levels at the entry of the prediffuser on the performance characteristics of combustor diffusers. The possibility of getting an unseparated flow field inside the prediffuser even at large opening angles by appropriately matching the diffuser’s opening angle and the flame tube distance is demonstrated. Also, for flows with an increased turbulence level at the entrance—all other conditions held constant—an increased opening angle can be realized without experiencing flow separation. The comparison of the experimental data with predictions utilizing a finite-volume-code based on a body-fitted coordinate system for diffusers with an included total opening angle less than 18 deg demonstrates the capability of describing the flow field in combustor diffusers with reasonable accuracy.
Calculation of Two-Phase Flow in Gas Turbine Combustors
Authors: Tolpadi A. K.
Published: February 2008

A method is presented for computing steady two-phase turbulent combusting flow in a gas turbine combustor. The gas phase equations are solved in an Eulerian frame of reference. The two-phase calculations are performed by using a liquid droplet spray combustion model and treating the motion of the evaporating fuel droplets in a Lagrangian frame of reference. The numerical algorithm employs nonorthogonal curvilinear coordinates, a multigrid iterative solution procedure, the standard k-ε turbulence model, and a combustion model comprising an assumed shape probability density function and the conserved scalar formulation. The trajectory computation of the fuel provides the source terms for all the gas phase equations. This two-phase model was applied to a real piece of combustion hardware in the form of a modern GE/SNECMA single annular CFM56 turbofan engine combustor. For the purposes of comparison, calculations were also performed by treating the fuel as a single gaseous phase. The effect on the solution of two extreme situations of the fuel as a gas and initially as a liquid was examined. The distribution of the velocity field and the conserved scalar within the combustor, as well as the distribution of the temperature field in the reaction zone and in the exhaust, were all predicted with the combustor operating both at high-power and low-power (ground idle) conditions. The calculated exit gas temperature was compared with test rig measurements. Under both low and high-power conditions, the temperature appeared to show an improved agreement with the measured data when the calculations were performed with the spray model as compared to a single-phase calculation.
A Theoretical and Experimental Investigation of a Gas-Operated Bearing Damper for Turbomachinery: Part I—Theoretical Model and Predictions
Authors: Sundararajan P. , Vance J. M.
Published: February 2008

This is the first (Part I) of two papers describing recent results of the research program directed at developing a vibration damper suitable for high-temperature turbomachinery applications. It is expected that such dampers will replace squeeze-film dampers, which use oil as the working fluid and have limitations at higher temperatures. A novel gas-operated bearing damper has been evaluated analytically and experimentally for its damping characteristics. A theory based on the isentropic assumptions predicts the damper performance characteristics reasonably well. A maximum damping level of 2311 N-m/s (13.2 lb-s/in.) at a frequency of 100 Hz was measured with a single actuator of the gas damper. Since many such actuators could be placed circumferentially around the squirrel cage, considerable damping levels can be realized. The study also shows that significantly higher damping levels can be achieved by modifying the current design. Part I describes the theoretical model that has been developed based on isentropic assumptions. This model is an improved version of the previous theory (Vance et al., 1991) and includes the supply groove effects, dynamic area changes of the inlet feeding holes, and the effects of flow choking on damper behavior. The governing equations are derived and theoretical predictions using these equations have been made for two hardware designs that were experimentally investigated (see Part II for experimental results).
Diesel Electro-injector: A Numerical Simulation Code
Authors: Digesu P. , Laforgia D.
Published: February 2008

A simulation code of an electro-injector for diesel engines is presented with the preliminary parametric analysis carried out with the code. The simulation code is based upon the concentrated volume method as for the chambers of the system. Energy and flow rate conservation equations and dynamic equations are used for the movable parts of the system under stress or friction. The magnetic force acting on the electro-injector actuator has been calculated by means of a finite element simulation. The one-dimensional code simulated the propagation in feeding pipes and the control of the electro-injector. The program, in fact, uses the method of the characteristic equations to solve conservation equations, simulating the propagation in a pipe between two chambers. The sensitivity analysis has pointed out that the parameters that are influenced by the propagation in the pipes are: needle lift, injected flow rate, pressure in each chamber, and volume. The perturbations reduce the effective pressure of injection and are influenced by pipe lengths and diameters.
Development of the 2400G Stationary Gas Engines
Authors: Chrisman B. M. , Freen P. D.
Published: February 2008

Development of the in-line versions of the 2400G Series of spark ignited, gas-fueled engines has been in process for the last six years. The main objective of this program is to produce a new series of 1200 rpm gas engines having a continuous duty rating of 200 bhp per cylinder. This paper deals with the highlights of the engine development program from the initial concept stage through the operation of prototype engines at customer sites. Development procedures are described that led to substantial advances in performance improvement and exhaust emissions control. A focal point of this work is the combustion analysis, which was conducted through computer simulation and through the operation of a gas-fueled, single-cylinder test facility. This preliminary analysis resulted in the definition of the basic configurations for the prechamber and the main combustion chamber. The applicability of the modeling and the single cylinder test work to the six and eight cylinder engines is evaluated in this paper. Development of appropriate manifolding, turbocharging, and cylinder balance was a critical part of the multicylinder phase of this program. Another key issue was the design and testing of the electronic feedback control system that assures continuous operation at conditions that produce optimized fuel economy and exhaust emissions. The satisfactory operation of the six and eight cylinder 2400G prototype engines in the field is based on the foundation of the developmental work described in this paper.
Landfill Gas Application Development of the Caterpillar G3600 Spark-Ignited Gas Engine
Authors: Mueller G. P.
Published: February 2008

A G3600 engine was developed to operate on landfill gas to demonstrate engine performance and identify any operational problems caused by this application. Fuel system and engine performance development were completed using simulated landfill gas containing carbon dioxide and natural gas at the Caterpillar Technical Center. The engine was packaged as a generator set and has operated for 12,000 hours on landfill gas. Engine performance goals similar to those for G3600 natural gas applications were achieved during development and were attained during the field test. Development work and field test endurance results are presented in this paper.
Advanced Gas Engine Cogeneration Technology for Special Applications
Authors: Plohberger D. C. , Fessl T. , Gruber F. , Herdin G. R.
Published: February 2008

In recent years gas Otto-cycle engines have become common for various applications in the field of power and heat generation. Gas engines in gen-sets and cogeneration plants can be found in industrial sites, oil and gas field application, hospitals, public communities, etc., mainly in the U.S., Japan, and Europe, and with an increasing potential in the upcoming areas in the far east. Gas engines are chosen sometimes even to replace diesel engines, because of their clean exhaust emission characteristics and the ample availability of natural gas in the world. The Austrian Jenbacher Energie Systeme AG has been producing gas engines in the range of 300 to 1600 kW since 1960. The product program covers state-of-the-art natural gas engines as well as advanced applications for a wide range of alternative gas fuels with emission levels comparable to Low Emission (LEV) and Ultra Low Emission Vehicle (ULEV) standards. In recent times the demand for special cogeneration applications is rising. For example, a turnkey cogeneration power plant for a total 14.4 MW electric power and heat output consisting of four JMS616-GSNLC/B spark-fired gas engines specially tuned for high altitude operation has been delivered to the well-known European ski resort of Sestriere. Sestriere is situated in the Italian Alps at an altitude of more than 2000 m (approx. 6700 ft) above sea level. The engines feature a turbocharging system tuned to an ambient air pressure of only 80 kPa to provide an output and efficiency of each 1.6 MW and up to 40 percent @ 1500 rpm, respectively. The ever-increasing demand for lower pollutant emissions in the U.S. and some European countries initiates developments in new exhaust aftertreatment technologies. Thermal reactor and Selective Catalytic Reduction (SCR) systems are used to reduce tailpipe CO and NOx emissions of engines. Both SCR and thermal reactor technology will shift the engine tuning to achieve maximum efficiency and power output. Development results are presented, featuring the ultra low emission potential of biogas and natural gas engines with exhaust aftertreatment.
Variables Affecting NOx Formation in Lean-Premixed Combustion
Authors: Steele R. C. , Jarrett A. C. , Malte P. C. , Tonouchi J. H. , Nicol D. G.
Published: February 2008

The formation of NOx in lean-premixed, high-intensity combustion is examined as a function of several of the relevant variables. The variables are the combustion temperature and pressure, fuel type, combustion zone residence time, mixture inlet temperature, reactor surface-to-volume ratio, and inlet jet size. The effects of these variables are examined by using jet-stirred reactors and chemical reactor modeling. The atmospheric pressure experiments have been completed and are fully reported. The results cover the combustion temperature range (measured) of 1500 to 1850 K, and include the following four fuels: methane, ethylene, propane, and carbon monoxide/hydrogen mixtures. The reactor residence time is varied from 1.7 to 7.4 ms, with most of the work done at 3.5 ms. The mixture inlet temperature is taken as 300 and 600 K, and two inlet jet sizes are used. Elevated pressure experiments are reported for pressures up to 7.1 atm for methane combustion at 4.0 ms with a mixture inlet temperature of 300 K. Experimental results are compared to chemical reactor modeling. This is accomplished by using a detailed chemical kinetic mechanism in a chemical reactor model, consisting of a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR). The methane results are also compared to several laboratory-scale and industrial-scale burners operated at simulated gas turbine engine conditions.
Lean Blowout Research in a Generic Gas Turbine Combustor With High Optical Access
Authors: Sturgess G. J. , Shouse D.
Published: February 2008

The U. S. Air Force is conducting a comprehensive research program aimed at improving the design and analysis capabilities for flame stability and lean blowout in the combustors of aircraft gas turbine engines. As part of this program, a simplified version of a generic gas turbine combustor is used. The intent is to provide an experimental data base against which lean blowout modeling might be evaluated and calibrated. The design features of the combustor and its instrumentation are highlighted, and the test facility is described. Lean blowout results for gaseous propane fuel are presented over a range of operating conditions at three different dome flow splits. Comparison of results with those of a simplified research combustor is also made. Lean blowout behavior is complex, so that simple phenomenological correlations of experimental data will not be general enough for use as design tools.
Optimum Power Boosting of Gas Turbine Cycles With Compressor Inlet Air Refrigeration
Authors: Ait-Ali M. A.
Published: February 2008

A conceptual gas turbine cycle with refrigerated air supplied to the compressor inlet is proposed to increase the cycle specific net power significantly and render it practically insensitive to seasonal temperature fluctuations. It is optimized for maximum power per m3/s and maximum power per kg/s of induced air. These cycle performances are evaluated in a numerical example for two refrigeration cycle efficiencies, based on state-of-the-art isentropic efficiency coefficients of the compressor and turbine. The specific heats of air and products of combustion are treated as temperature-dependent parameters to be determined as integrated mean averages.
An Adaptive Perturbation Scheme for the Analysis of Mistuned Bladed Disks
Authors: Lin C.-C. , Mignolet M. P.
Published: February 2008

In this paper, a novel perturbation technique is introduced for the determination of the forced vibration response of mistuned bladed disks. The proposed technique is adaptive in the sense that the level of approximation can be varied at will to accommodate any specificities of the tuned system and/or of the existing mistuning. This versatility of the proposed approach not only guarantees the reliability of the computed response but also leads to an excellent compromise between accuracy and computational effort. Numerical results are presented that demonstrate both the reliability of the computed response and the computational saving obtained by relying on the suggested perturbation technique as opposed to a straightforward steady-state analysis.
Dynamic Mechanical Properties of Ceramics and Ceramic Composites at Elevated Temperatures
Authors: Yang S. , Gibson R. F. , Crosbie G. M. , Allor R. L.
Published: February 2008

This paper presents the preliminary results of our research on dynamic mechanical properties of silicon nitride based ceramics and ceramic composites at elevated temperatures. The temperature-dependent dynamic elastic modulus and internal damping of the cantilever beam samples were measured from room temperature up to 1100°C. The dynamic mechanical behavior is found to be rather stable up to 700°C, but damping peaks are found to occur at around 900°C, accompanied by a corresponding relaxation in elastic modulus for the tested samples. By simulating the thermal cycling environment of engines, the resulting changes in the dynamic mechanical properties of the samples are observed. The possible mechanisms affecting the dynamic mechanical properties of these ceramics and ceramic composites, with special emphasis on high-temperature behavior, are discussed.
Fiber Fracture in Continuous Fiber Ceramic Composites: Concepts and Observations
Authors: Reifsnider K. , Liao K. , McCormick M. , Tiwari A.
Published: February 2008

The knowledge of fiber behavior in CMCs is rather modest, and models tend to be based on concepts that are less than complete. The present paper addresses several aspects of this problem. Fundamental assumptions for tensile strength models are discussed, and some basic modeling approaches are described. The effects of fiber fracture on the quasi-static stress–strain behavior are described (from physical measurements), and some models of that behavior discussed. Finally, a summary of the “state of affairs” for this subject will be attempted, and the needs for further investigation, especially to support improved modeling, will be presented.
Air Extraction in a Gas Turbine for Integrated Gasification Combined Cycle (IGCC): Experiments and Analysis
Authors: Kapat J. S. , Agrawal A. K. , Yang T.
Published: February 2008

This paper presents an investigation of extracting air from the compressor discharge of a heavy-frame gas turbine. The study aimed to verify results of an approximate analysis: whether extracting air from the turbine wrapper would create unacceptable nonuniformity in the flow field inside the compressor discharge casing. A combined experimental and computational approach was undertaken. Cold flow experiments were conducted in an approximately one-third scale model of a heavy-frame gas turbine; a closely approximated three-dimensional computational fluid dynamic analysis was also performed. This study substantiated the earlier prediction that extracting air from the turbine wrapper would be undesirable, although this method of air extraction is simple to retrofit. Prediffuser inlet is suggested as an alternate location for extracting air. The results show that not only was the problem of flow nonuniformity alleviated with this alternate scheme, but the frictional power loss in the compressor discharge casing was also reduced by a factor of two.
On the Relative Roles of Fuel Spray Kinetic Energy and Engine Speed in Determining Mixing Rates in D.I. Diesel Engines
Authors: Smith W. J. , Timoney D. J.
Published: February 2008

This paper describes an attempt to separate out and to quantify the relative importance of fuel injection characteristics and in-cylinder air motion as factors influencing the rate of fuel-air mixing and of combustion in high-speed D.I. diesel engines, where bulk swirling air motion is absent. Tests on a 121 mm bore × 139 mm stroke, 1.6 liter, single-cylinder engine at constant engine speed reveal substantially shorter fuel-air mixing times as the mean fuel injection kinetic energy (M.I.K.E.) is increased. Also, tests at constant injection kinetic energy but with varying engine speed (involving different fuel injection system builds at each speed) show that fuel-air mixing times are reduced at higher engine speeds. From these trends it is concluded that, while injection kinetic energy is the dominant factor in determining fuel-air mixing rates in D.I. diesels, small-scale turbulent air motions, the intensity and structure of which are related to engine speed, also exert an important influence on the mixing rate.
The Hybrid Rich-Burn/Lean-Burn Engine
Authors: Meyers D. P. , Kubesh J. T.
Published: February 2008

This paper describes a new low-emissions engine concept called the hybrid rich-burn/lean-burn (HRBLB) engine. In this concept a portion of the cylinders of a multicylinder engine are fueled with a very rich natural gas-air mixture. The remaining cylinders are operated with a lean mixture of natural gas and air and supplemented with the rich combustion exhaust. The goal of this unique concept is the production of extremely low NOx (e.g., 5 ppm when corrected to 15 percent exhaust oxygen content). This is accomplished by operating outside the combustion limits where NOx is produced. In rich combustion an abundance of hydrogen and carbon monoxide is produced. Catalyst treatment of the rich exhaust can be employed to increase the hydrogen concentration and decrease the carbon monoxide concentration simultaneously. The hydrogen-enriched exhaust is used to supplement the lean mixture cylinders to extend the lean limit of combustion, and thus produces ultralow levels of NOx. Results to date have shown NOx levels as low as 8 ppm at 15 percent oxygen can be achieved with good combustion stability and thermal efficiency.
Effect of Inertia Variation Due to Reciprocating Parts and Connecting Rod on Coupled Free Vibration of Crankshaft
Authors: Rajendran S. , Narasimhan M. V.
Published: February 2008

The inertia due to reciprocating parts and connecting rods, as felt by the crankshaft, varies with the crank angle. The effect of inertia variation on torsional free vibration of crankshafts has been studied extensively. In this paper, the effect on combined torsional and bending free vibrations is examined. Single-cylinder engine crankshaft geometry is considered for the study. The results indicate that the inertial coupling, introduced by the reciprocating parts and connecting rod, significantly influences the free vibration characteristics, particularly when the natural frequencies of the crankskahft are closely spaced. The results suggest that, under such conditions, modeling the crankshaft as a pure torsional system would involve considerable error.
Topping Combustor Status for Second-Generation Pressurized Fluidized Bed Cycle Application
Authors: Domeracki W. F. , Dowdy T. E. , Bachovchin D. M.
Published: February 2008

Second-generation Pressurized Fluidized Bed (PFB) combined cycles employ topping combustion to raise the turbine inlet temperature for enhanced cycle efficiency. This concept creates special combustion system requirements that are very different from requirements of conventional gas turbine systems. The topping combustor provides the means for achieving state-of-the-art turbine inlet temperatures and is the main contributor to enhanced plant performance. The objective of this program is to develop a topping combustor that provides low emissions, and is a durable, efficient device exhibiting stable combustion and manageable wall temperatures. The combustor will be required to burn a low-Btu Syngas under normal “coal-fired” conditions. However, for start-up and/or carbonizer outage, it may be necessary to fire a clean fuel, such as oil or natural gas. Prior testing has shown the Westinghouse Multi-Annular Swirl Burner (MASB) to have excellent potential for this application. Metal wall temperatures can be maintained at acceptable levels, even though most “cooling” is done by 1600°F vitiated air. Good pattern factors and combustion efficiencies have been obtained. Additionally, low conversion rates of fuel bound nitrogen to NOx have been demonstrated. This paper presents an update of the status of an ongoing topping combustor development and test program for application to “Second-Generation Pressurized Fluidized Bed Combined Cycles (PFBCC).” The program is sponsored by the Department of Energy’s Morgantown Energy Technology Center (DOE/METC) and will first be applied commercially into the Clean Coal Technology Round V Four Rivers Energy Modernization Project. Phase 1 of the program involved a conceptual and economic study (Robertson et al., 1988); Phase 2 addresses design and subscale testing of components; and Phase 3 will cover pilot plant testing of components integrated into one system.
Dual-Use Conversion of a High-Mach-Number Jet Engine Test Cell for Industrial Gas Turbine Low-Emission Combustor Development
Authors: Pillsbury P. W. , Ryan W. R. , Moore J. R.
Published: February 2008

With the recent trend of reducing U.S. military expenditures, it has become desirable to develop dual use of certain Department of Defense facilities. These efforts have a commercial purpose, while still retaining a military benefit. The goals of these efforts are to make U.S. business more competitive in world markets, to develop the technology to solve pressing national problems, and to maintain intact the necessary talent pool and equipment for possible military needs. In a recent initiative described in this paper, test cell equipment at the Arnold Engineering Development Center, Arnold AFB, Tennessee, was modified and expanded to allow development by the Westinghouse Electric Corporation of low-emission combustors for heavy-duty gas turbines for commercial power generation.
Combustor Stability and Emissions Research Using a Well-Stirred Reactor
Authors: Zelina J. , Ballal D. R.
Published: February 2008

The design and development of low-emissions, lean premixed aero or industrial gas turbine combustors is very challenging because it entails many compromises. To satisfy the projected CO and NOx emissions regulations without relaxing the conflicting requirements of combustion stability, efficiency, pattern factor, relight (for aero combustor), or off-peak loading (for industrial combustor) capability demands great design ingenuity. The well-stirred reactor (WSR) provides a laboratory idealization of an efficient and highly compact advanced combustion system of the future that is capable of yielding global kinetics of value to the combustor designers. In this paper, we have studied the combustion performance and emissions using a toroidal WSR. It was found that the toroidal WSR was capable of peak loading almost twice as high as that for a spherical WSR and also yielded a better fuel-lean performance. A simple analysis based upon WSR theory provided good predictions of the WSR lean blowout limits. The WSR combustion efficiency was 99 percent over a wide range of mixture ratios and reactor loading. CO emissions reached a minimum at a flame temperature of 1600 K and NOx increased rapidly with an increase in flame temperature, moderately with increasing residence time, and peaked at or slightly on the fuel-lean side of the stoichiometric equivalence ratio. Finally, emissions maps of different combustors were plotted and showed that the WSR has the characteristics of an idealized high-efficiency, low-emissions combustor of the future.
Economic Scales for First-Generation Biomass-Gasifier/Gas Turbine Combined Cycles Fueled From Energy Plantations
Authors: Larson E. D. , Marrison C. I.
Published: February 2008

This paper assesses the scales at which commercial, first-generation biomass integrated-gasifier/gas turbine combined cycle (BIG/GTCC) technology is likely to be most economic when fueled by plantation-derived biomass. First-generation BIG/GTCC systems are likely to be commercially offered by vendors beginning around 2000 and will be based on either pressurized or atmospheric-pressure gasification. Both plant configurations are considered here, with estimates of capital and operating costs drawn from published and other sources. Prospective costs of a farm-grown energy crop (switchgrass) delivered to a power plant are developed with the aid of a geographic information system (GIS) for agricultural regions in the North Central and Southeast US in the year 2000 and 2020. A simplified approach is applied to estimate the cost of delivering chipped eucalyptus from an existing plantation in Northeast Brazil. The “optimum” capacity (MWopt), defined as that which yields the minimum calculated cost of electricity (COEm), varies by geographic region due to differences in delivered biomass costs. With pressurized BIG/GTCC plants, MWopt is in the range of 230–320 MWe for the sites considered, assuming most of the land around the power plant is farmed for energy crop production. For atmospheric-pressure BIG/GTCC plants, MWopt ranges from 110 to 142 MWe. When a lower fraction of the land around a plant is used for energy farming, values for MWopt are smaller than these. In all cases, the cost of electricity is relatively insensitive to plant capacity over a wide range around MWopt.
An Experimental and Computational Study of Swirling Hydrogen Jet Diffusion Flames
Authors: Anand M. S. , Takahashi F. , Vangsness M. D. , Durbin M. D. , Schmoll W. J.
Published: February 2008

Computations using the joint velocity-scalar probability density function (pdf) method as well as benchmark quality experimental data for swirling and nonswirling hydrogen jet diffusion flames are reported. Previous studies of diffusion flames reported in the literature have been limited to nonswirling flames and have had no detailed velocity data reported in the developing (near-nozzle) region of the flames. The measurements and computations reported herein include velocities (mean and higher moments up to fourth order) and temperature (mean and variance) near the burner exit and downstream locations up to 26.5 jet diameters. The velocities were measured with a three-component laser-Doppler velocimeter (LDV) and the temperature was measured using coherent anti-Stokes Raman spectroscopy (CARS). The joint pdf method offers significant advantages over conventional methods for computing turbulent reacting flow, and the computed results are in good agreement with data. This study serves to present data that can be used for model validation as well as to validate further the joint pdf method.
The Effects of Different Sulfur Compounds on Jet Fuel Oxidation and Deposition
Authors: Kauffman R. E.
Published: February 2008

This paper presents research that supports a proposed fuel oxidation/deposition mechanism involving acid:base reactions between “oxidizable” sulfur compounds, “basic” nitrogen compounds, and oxygen-containing polymers. The reported research presents experiments that study the effects of different sulfur compounds on the high-temperature (160–220°C) oxidation products and deposition tendencies of jet fuel. Surface analyses incorporating elemental analyses and depth profiles of deposits formed on steel surfaces were performed to identify the species involved in the initial stages of deposition by jet fuels. Experiments to study the effects of acid neutralizing compounds on the deposition tendencies of jet fuels are also presented.
Hydrocarbon Fuel Cooling Technologies for Advanced Propulsion
Authors: Sobel D. R. , Spadaccini L. J.
Published: February 2008

Storable hydrocarbon fuels that undergo endothermic reaction provide an attractive heat sink for future high-speed aircraft. An investigation was conducted to explore the endothermic potential of practical fuels, with inexpensive and readily available catalysts, under operating conditions simulative of high-speed flight applications. High heat sink capacities and desirable reaction products have been demonstrated for n-heptane and Norpar 12 fuels using zeolite catalysts in coated-tube reactor configurations. The effects of fuel composition and operating condition on extent of fuel conversion, product composition, and the corresponding endotherm have been examined. The results obtained in this study provide a basis for catalytic-reactor/heat-exchanger design and analysis.
Differential Mass and Energy Balances in the Flame Zone From a Practical Fuel Injector in a Technology Combustor
Authors: Warren D. L. , Hedman P. O.
Published: February 2008

This paper presents further analysis of experimental results from an Air Force program conducted by researchers at Brigham Young University (BYU), Wright-Patterson Air Force Base (WPAFB), and Pratt and Whitney Aircraft Co. (P&W) (Hedman et al., 1994a, 1995). These earlier investigations of the combustion of propane in a practical burner installed in a technology combustor used: (1) digitized images from video and still film photographs to document observed flame behavior as fuel equivalence ratio was varied, (2) sets of LDA data to quantify the velocity flow fields existing in the burner, (3) CARS measurements of gas temperature to determine the temperature field in the combustion zone, and to evaluate the magnitude of peak temperature, and (4) two-dimensional PLIF images of OH radical concentrations to document the instantaneous location of the flame reaction zones. This study has used the in situ velocity and temperature measurements from the earlier study, suitably interpolated, to determine local mass and energy balances on differential volume elements throughout the flame zone. The differential mass balance was generally within about ±10 percent with some notable exceptions near regions of very high shear and mixing. The local differential energy balance has qualitatively identified the regions of the flame where the major heat release is occurring, and has provided quantitative values on the rate of energy release (up to −400 kJ/m3s). The velocity field data have also been used to determine Lagrangian pathlines through the flame zone. The local velocity and temperature along selected pathlines have allowed temperature timelines to be determined. The temperature generally achieves its peak value, often near the adiabatic flame temperature, within about 10 ms. These temperature timelines, along with the quantitative heat release data, may provide a basis for evaluating kinetic combustion models.
Numerical Simulation of Blade Fault Signatures From Unsteady Wall Pressure Signals
Authors: Dedoussis V. , Mathioudakis K. , Papailiou K. D.
Published: February 2008

A method for establishing signatures of faults in the rotating blades of a gas turbine compressor is presented. The method employs a panel technique for the calculation of the flow field around blade cascades, with disrupted periodicity, a situation encountered when a blade fault has occurred. From this calculation, time signals of the pressure at a location on the casing wall, facing the rotating blades, are constituted. Processing these signals, in combination with “healthy” pressure signals, allows the constitution of fault signatures. The proposed method employs geometric data, as well as data about the operating point of the engine. It gives the possibility of establishing the fault signatures without the need of performing experiments with implanted faults. The successful application of the method is demonstrated by comparison of signatures obtained by simulation to signatures derived from experiments with implanted blade faults, in an industrial gas turbine.
Multivariable Trend Analysis Using Neural Networks for Intelligent Diagnostics of Rotating Machinery
Authors: Zhang S. , Ganesan R.
Published: February 2008

The objective of this paper is the development of an efficient intelligent diagnostic procedure that considers several diagnostic indices for the quantification of developing faults and for monitoring machine condition. In this procedure, the condition monitoring is performed based on the on-line vibration measurements, and further, the fault quantification is formulated into a multivariate trend analysis. Self-organizing neural networks are then deployed to perform the multivariable trending of the fault development. The attributes for the disordering of “knots” in the trend analysis are determined. The disordering of neural network units is then eliminated by suitably altering the self-organizing neural network algorithm. Applications of this diagnostic procedure to the condition monitoring and life estimation of a bearing system are fully developed and demonstrated. The efficiency and advantages of the intelligent diagnostic procedure in precisely monitoring and quantifying the fault development are systematically brought out considering this bearing system.
Split Stream Boilers for High-Temperature/High-Pressure Topping Steam Turbine Combined Cycles
Authors: Rice I. G.
Published: February 2008

Research and development work on high-temperature and high-pressure (up to 1500°F TIT and 4500 psia) topping steam turbines and associated steam generators for steam power plants as well as combined cycle plants is being carried forward by DOE, EPRI, and independent companies. Aeroderivative gas turbines and heavy-duty gas turbines both will require exhaust gas supplementary firing to achieve high throttle temperatures. This paper presents an analysis and examples of a split stream boiler arrangement for high-temperature and high-pressure topping steam turbine combined cycles. A portion of the gas turbine exhaust flow is run in parallel with a conventional heat recovery steam generator (HRSG). This side stream is supplementary fired opposed to the current practice of full exhaust flow firing. Chemical fuel gas recuperation can be incorporated in the side stream as an option. A significant combined cycle efficiency gain of 2 to 4 percentage points can be realized using this split stream approach. Calculations and graphs show how the DOE goal of 60 percent combined cycle efficiency burning natural gas fuel can be exceeded. The boiler concept is equally applicable to the integrated coal gas fuel combined cycle (IGCC).
Nonlinear Vibrations and Stability of a Rotor-Bearing System With Nonsymmetric Clearances
Authors: Ganesan R.
Published: February 2008

The nonlinear vibrations of a rotordynamic system that is subjected to nonsymmetric bearing clearance effects are considered. Particular attention is paid to the nonstationary response that occurs during passage through resonance. Based on an extended Jeffcott rotor model that includes the effects of nonsymmetric bearing clearances, the steady-state oscillations and their stability are also analyzed. The “normal-loose” rotor stiffness condition that occurs due to the bearing clearance effects is modeled through a discontinuous radial stiffness model. Expressions for the amplitude and phase-modulating functions are obtained. Frequency-amplitude relationships are derived. The effects of “normal-loose” rotor stiffness condition on the modulation of both the amplitude and phase of the near-resonance vibrations, as well as the stability of the rotor system, are systematically brought out. The effects of high-speed acceleration during run-up of the rotor are both qualified and quantified. Similarly, the case of run-down is analyzed.
Synchronous Dynamics of a Coupled Shaft/Bearing/Housing System With Auxiliary Support From a Clearance Bearing: Analysis and Experiment
Authors: Lawen J. L. , Flowers G. T.
Published: February 2008

This study examines the response of a flexible rotor supported by load sharing between linear bearings and an auxiliary clearance bearing. The objective of the work is to develop a better understanding of the dynamic behavior of a magnetic bearing supported rotor system interacting with auxiliary bearings during a critical operating condition. Of particular interest is the effect of coupling between the bearing/housing and shaft vibration on the rotor-dynamic responses. A simulation model is developed and a number of studies are performed for various parametric configurations. An experimental investigation is also conducted to compare and verify the rotor-dynamic behavior predicted by the simulation studies. A strategy for reducing sychronous shaft vibration through appropriate design of coupled shaft/bearing/housing vibration modes is identified. The results are presented and discussed.
Optimization of Bearing Locations for Rotor Systems With Magnetic Bearings
Authors: Srinivasan S. , Maslen E. H. , Barrett L. E.
Published: February 2008

This paper presents a method for quickly evaluating the effect of changes in bearing location on bearing design for stability of rotating machinery. This method is intended for use by rotating machinery designers to select the “best” bearing locations prior to the bearing design process. The purpose of the method is to improve the design process by separating the problem of determining the “best” bearing locations from that of determining the actual bearing design. The method is independent of the type of bearing employed. For each candidate bearing configuration, the method provides a scalar measure of the relative ability of bearings to meet stability specifications. Within certain limits, the stability specifications are defined by the designer. The scalar measure is used to rank the candidate bearing locations and thereby select the best one. The scalar measure is compared to a practical measure of magnetic bearing design such as the infinity norm of the controller for an example design of a multistage centrifugal compressor.