Showing papers in "Journal of Engineering for Gas Turbines and Power-transactions of The Asme in 1987"

Interpretation of gas turbine response due to dust ingestion

Abstract: A measurement program currently underway at Arvin/Calspan Advanced Technology Center has been used in the evaluation of observed engine behavior during dust ingestion. The Pratt and Whitney TF33 turbofan and J57 turbojet were used in the investigation. Solid particle ingestion was found to erode the compressor blades and result in substantial performance deterioration. The engines were found to have increased susceptibility to surge at low power settings. The roles that anti-ice and intercompressor bleed airplay in surge avoidance are discussed. A discussion of the fuel controller behavior in a deteriorated engine and its effect during steady-state engine operation is also presented. Experimental data obtained during testing were compared to a predictive capability developed to describe deteriorated engine response. The effects of tip clearance, blade profile, and secondary flows were taken into account. The results show good agreement with experimentally observed engine behavior.

Performance deterioration of a turbofan and a turbojet engine upon exposure to a dust environment

Abstract: Deterioration des performances d'un turboreacteur simple flux et d'un turboreacteur double flux dans un environnement charge de poussieres

Exergy Analysis of Combined Cycles: Part 1—Air-Cooled Brayton-Cycle Gas Turbines

Abstract: Quantitative analytical tools based on the second law of thermodynamics provide insight into the complex optimization tradeoffs encountered in the design of a combined cycle. These tools are especially valuable when considering approaches beyond the existing body of experience, whether in cycle configuration or in gas turbine cooling technology. A framework for such analysis was provided by the author [1-3] using simplified, constant-property models. In this paper, this theme is developed to include actual chemical and thermodynamic properties as well as relevant practical design details reflecting current engineering practice. The second-law model is applied to calculate and provide a detailed breakdown of the sources of inefficiency of a combined cycle. Stage-by-stage turbine cooling flow and loss analysis calculations are performed using the GASCAN program and examples of the resulting loss breakdowns presented. It is shown that the dominant interaction governing the variation of cycle efficiency with turbine inlet temperature is that between combustion irreversibility and turbine cooling losses. Compressor and pressure-drop losses are shown to be relatively small. A detailed analysis and loss breakdown of the steam bottoming cycle is presented in Part 2 of this paper.

Steam-Injected Gas Turbines

Abstract: Rising electricity prices, the near-term prospect of surplus natural gas supplies, and the provisions of the Public Utility Regulatory Policies Act (PURPA) and ensuing regulations that encourage cogeneration have stimulated a wave of innovation in gas turbine technology. Here the significance of one of these innovations, the steam-injected gas turbine, is assessed for both cogeneration and central station power generation.

Effective Thermal Conductivity of Coal Ash Deposits at Moderate to High Temperatures

Abstract: The effective thermal conductivity of coal ash deposits strongly influences heat transfer in pulverized coal-fired boilers. In this study thermal conductivity measurements were performed over a wide range of temperatures for fly ash, slagging deposits, and fouling deposits. The effects of ash particle size, thermal history, and physical structure of the deposit are discussed. Thermal history and deposit structure were observed to have the greatest influence on the local thermal conductivity, which increased by an order of magnitude with particle melting. Conductivities for solid-porous deposits were twice those of the same sample in particulate form.

Wetness and Efficiency Measurements in L.P. Turbines With an Optical Probe As an Aid to Improving Performance

Abstract: Mesure de l'humidite et du rendement par des sondes optiques dans une turbine basse pression et consequences pour l'amelioration des performances

Exergy analysis of combined cycles: Part 2 - Analysis and optimization of two-pressure steam bottoming cycles

Abstract: Results of a study for selecting the optimum parameters of a dual-pressure bottoming cycle as a function of the gas turbine exhaust temperature are presented. Realistic constraints reflecting current technological practice are assumed. Exergy analysis is applied to quantify all loss sources in each cycle. Compared to a single pressure at typical exhaust gas temperatures the optimized dual-pressure configuration is found to increase steam cycle work output on the order of 3 percent, principally through the reduction of the heat transfer irreversibility from about 15 to 8 percent of the exhaust gas energy. Measures to further reduce the heat transfer irreversibility such as three-pressure systems or use of multicomponent mixtures can therefore only result in modest additional gains. The results for the efficiency of optimized dual-pressure bottoming cycles are correlated against turbine exit temperature by simple polynomial fits. Sensitivity of the results to variations in the constraint envelope are presented.

Surface Flaw Reliability Analysis of Ceramic Components with the Scare Finite Element Postprocessor Program

Abstract: The SCARE (Structural Ceramics Analysis and Reliability Evaluation) computer program on statistical fast fracture reliability analysis with quadratic elements for volume distributed imperfections is enhanced to include the use of linear finite elements and the capability of designing against concurrent surface flaw induced ceramic component failure. The SCARE code is presently coupled as a postprocessor to the MSC/NASTRAN general purpose, finite element analysis program. The improved version now includes the Weibull and Batdorf statistical failure theories for both surface and volume flaw based reliability analysis. The program uses the two-parameter Weibull fracture strength cumulative failure probability distribution model with the principle of independent action for poly-axial stress states, and Batdorf's shear-sensitive as well as shear-insensitive statistical theories. The shear-sensitive surface crack configurations include the Griffith crack and Griffith notch geometries, using the total critical coplanar strain energy release rate criterion to predict mixed-mode fracture. Weibull material parameters based on both surface and volume flaw induced fracture can also be calculated from modulus of rupture bar tests, using the least squares method with known specimen geometry and grouped fracture data. The statistical fast fracture theories for surface flaw induced failure, along with selected input and output formats and options, are summarized. An example problem to demonstrate various features of the program is included.

On the Premixed Combustion in a Direct-Injection Diesel Engine

Abstract: The factors influencing premixed burning and the importance of premixed burning on the exhaust emissions from a small high-speed direct-injection diesel engine were investigated. The characteristics of premixed and diffusion burning were examined using a single-zone heat-release analysis. The mass of fuel burned in premixed combustion was found to be linearly related to the product of engine speed and ignition-delay time and to be essentially independent of the total amount of fuel injected. Accordingly, the premixed-burned fraction increased with increasing engine speed, with decreasing fuel-air ratio and with retarding injection timing. The hydrocarbon emissions did not correlate well with the premixed-burned fraction. In contrast, the oxides of nitrogen emissions were found to increase with decreasing premixed-burned fraction, indicating that diffusion burning, and not premixed burning, is the primary source of oxides of nitrogen emissions.

Induction System Effects on Small-Scale Turbulence in a High-Speed Diesel Engine

Abstract: Influence du systeme d'admission sur les turbulences a petite echelle dans un moteur diesel rapide

Parametric Analysis of Combined Gas-Steam Cycles

Abstract: Combined gas-steam cycles have been analyzed from the thermodynamic point of view. Suitable thermodynamics indices - explained in Appendix A - have been utilized. The parameters that most influence efficiency have been singled out and their ranges of variability have been specified. Calculations have been carried out taking into account the state of the art for gas turbines and the usual values for the quantities of steam cycles. The results are given. The maximal gas turbine temperature has been varied between 800/sup 0/C and 1400/sup 0/C. The gas turbine pressure ratio has been analyzed in the range of 2-24. Afterburning has also been taken into consideration. Maximal efficiency curves and the corresponding specific work curves (referred to the compressed air) related to the parameters of the analysis are given and discussed.

A Correlation for the Burning Velocity of Methane–Air Mixtures at High Pressures and Temperatures

Abstract: A formulation for the burning velocity of methane-air mixtures was developed over a range of equivalence ratios at temperatures and pressures high enough to cover conditions encountered in a typical operating spark ignition engine. An example involving the use of such data in a diagnostic program to yield information about the characteristics of flame propagation in an engine fueled with methane is shown.

Thermodynamic Evaluation of Gas Turbine Cogeneration Cycles: Part I—Heat Balance Method Analysis

Abstract: This paper presents a heat balance method of evaluating various open-cycle gas turbines and heat recovery systems based on the first law of thermodynamics. A useful graphic solution is presented that can be readily applied to various gas turbine cogeneration configurations. An analysis of seven commercially available gas turbines is made showing the effect of pressure ratio, exhaust temperature, intercooling, regeneration, and turbine rotor inlet temperature in regard to power output, heat recovery, and overall cycle efficiency. The method presented can be readily programmed in a computer, for any given gaseous or liquid fuel, to yield accurate evaluations. An X-Y plotter can be utilized to present the results.

Lifetime Prediction Under Constant Load Creep Conditions for a Cast Ni-Base Superalloy

Abstract: Creep and stress-rupture properties of cast IN-738LC turbine blades have been analyzed to review the suitability of the Monkman-Grant relationship as a reliable life prediction method where tr es m = C and m and C are material constants. The constants m and C in the Monkman-Grant relationship are temperature dependent and the relationship predicts lives within a factor of ±4 relative to the observed values. A modified form of this relationship is derived where (−b tr n1 + tr ) es m1 = K and b, n, m1 , and K are material constants. The modified relationship is more accurate and predicts lives within a factor of 2 relative to the observed values. The constants b, n, m, and k are independent of stress and temperature.

Reduction of NOx and Particulate Emissions in the Diesel Combustion Process

Abstract: Reduction des emissions d'oxydes d'azote et de particules dues a la combustion des moteurs diesel

Combustion Characteristics of a Single-Cylinder Open-Chamber Diesel Engine

Abstract: The combustion characteristics of an open-chamber diesel engine were examined by means of heat-release analysis and flame luminosity measurements. Increasing the load was found to decrease premixed burning and correspondingly to increase diffusion burning. During most of the diffusion combustion the burning rate of the fuel appeared to be directly proportional to the amount of unburned fuel present in the cylinder. The duration of heat release in crank-angle degrees increased linearly with load and, in general, increased with decreasing engine speed and retarded injection timing. The measured duration of flame luminosity was significantly longer than the calculated duration of heat release, which suggested that emission of radiation continued long after the heat-release reactions ceased.

A Comparison of the Predicted and Measured Thermodynamic Performance of a Gas Turbine Cogeneration System

Abstract: The thermodynamic performance of a gas turbine cogeneration system is predicted using a computer model The predicted performance is compared to the actual performance, determined by measurements, in terms of various thermodynamic performance parameters which are defined and discussed in this paper These parameters include the electric power output, fuel flow rate, steam production, electrical efficiency, steam efficiency, and total plant efficiency Other derived parameters are the net heat rate, the power-to-heat ratio, and the fuel savings rate This paper describes the cogeneration plant, the computer model, and the measurement techniques used to determine each of the necessary measurands The predicted and the measured electric power compare well The predicted fuel flow and steam production are less than measured The results demonstrate that this type of comparison is needed if computer models are to be used successfully in the design and selection of cogeneration systems

Materials and surface finish effects in the breaking-in process of engines

Abstract: In this investigation, three materials and several surface finishes on cylinder walls were compared in laboratory tests that simulate the running-in behavior or fired engines. The three materials were the conventional cast gray iron, a sintered graphite-iron powder, and a cast aluminum-silicon alloy. The surface finishes were formed by various types of polishing and honing, including ''plateau honing.'' The run-in behavior of these materials was indicated by a laboratory simulator that is known to correlate with the early wear seen in fired engines. Two test sequences were used. One is a scuff test, in which a quick succession of increasing contact pressure is applied between a piston ring and a cylinder wall until surface failure occurs. The other is a ''normal'' wear test in which a lower contact pressure is applied, for a longer term study of surface change and coefficient of friction. Scuff load and midstroke friction were found to be dependent on roughness but independent of the amount of plateauing, as measured by skewness of the height distribution in the surface roughness trace. Plateau-honed cylinders were found to run in no more quickly than uniform-honed cylinders. Graphite-iron powder and aluminum-silicon cylinder walls had lower scuff resistance than didmore » gray iron, but their ''normal'' wear behavior and midstroke friction performance were about the same as gray iron.« less

Engine valves - Design and material evolution

Abstract: This paper reviews the design and material evolution of poppet valves used in reciprocating internal combustion engines in the United States. Driving forces which led to the current state-of-the-art technology, such as needs for improved durability and cost effectiveness, are described. This paper also endeavors to predict how valve materials, design, and construction will change over the next two decades in response to continual engine performance improvement demands in a worldwide competitive environment. As a basis for understanding the past evolution and future trends in valve design, the key operating parameters that affect valve function are detailed.

Aeroelastic Behavior of Low-Aspect-Ratio Metal and Composite Blades

Abstract: The aeroelastic stability of titanium and composite blades of low aspect ratio is examined over a range of design parameters, using a Rayleigh-Ritz formulation. The blade modes include a plate-type mode to account for chordwise bending. Chord-wise flexibility is found to have a significant effect on the unstalled supersonic flutter of low-aspect-ratio blades, and also on the stability of tip sections of shrouded fan blades. For blades with a thickness of less than approximately 4 percent of chord, the chordwise, second bending, and first torsion branches are all unstable at moderately high supersonic Mach numbers. For composite blades, the important structural coupling between bending and torsion cannot be modeled properly unless chordwise bending is accounted for. Typically, aft fiber sweep produces beneficial bending-torsion coupling that is stabilizing, whereas forward fiber sweep has the opposite effect. By using crossed-ply laminate configurations, critical aeroelastic modes can be stabilized.

Tensile behavior of glass/ceramic composite materials at elevated temperatures

Abstract: This paper describes the tensile behavior of high-temperature composite materials containing continuous Nicalon ceramic fiber reinforcement and glass and glass/ceramic matrices. The longitudinal properties of these materials can approach theoretical expectations for brittle matrix composites, failing at a strength and ultimate strain level consistent with those of the fibers. The brittle, high-modulus matrices result in a nonlinear stress-strain curve due to the onset of stable matrix cracking at 10 to 30 percent of the fiber strain to failure, and at strains below this range in off-axis plies. Current fibers and matrices can provide attractive properties well above 1000 C, but composites experience embrittlement in oxidizing atmospheres at 800 to 1000 C due to oxidation of a carbon interface reaction layer.The oxidation effect greatly increases the interface bond strength, causing composite embrittlement.

Periodic and Continuous Vibration Monitoring for Preventive/Predictive Maintenance of Rotating Machinery

Abstract: Discussion de l'application du controle des vibrations considere comme une partie des programmes d'entretien, et description de plusieurs methodes incluant en particulier les techniques de controle continu ou periodique. Importance du choix des transducteurs de vibration en fonction du type specifique de machine. Necessite d'une interpretation par specialiste des donnees de vibration afin d'identifier les defauts de fonctionnement dont plusieurs exemples sont donnes

Continued Development of a Coal/Water Slurry-Fired Slow-Speed Diesel Engine: A Review of Recent Test Results

Abstract: Poursuite des recherches sur un moteur diesel lent utilisant un melange eau-charbon comme carburant. Bilan des derniers resultats d'essais

Operation of a Caterpillar 3516 spark-ignited engine on low-Btu fuel

Abstract: The use of an engine-generator package, fueled by landfill gas, to produce usable electrical power has generated considerable interest among both landfill operators and engine manufacturers. Landfill gas operation presents some unusual technical challenges that require preparation of the gas prior to engine consumption as well as modifications to the spark-ignited engine. The primary obstacles to landfill gas operation are the low-Btu content of the gas, its poor combustion characteristics, and fluctuations in the heating value of the gas. Even so, the engine was not derated from the standard natural gas generator set rating of 762 kW net electrical output. In addition, the engine performance was optimized to meet the EPA site laws for stationary gas engines while still maintaining very low brake specific fuel consumption (BSFC). Finally, 90 days of continuous operation demonstrated engine durability.

Progress Toward Life Modeling of Thermal Barrier Coatings for Aircraft Gas Turbine Engines

Abstract: Progress toward developing life models for simulating the behavior of thermal barrier coatings in aircraffft gas turbine engines is discussed. A preliminary laboratory model is described as are current efforts to develop engine-capable models. Current understanding of failure mechanisms is also summarized.

Thermodynamic Evaluation of Gas Turbine Cogeneration Cycles: Part II—Complex Cycle Analysis

Abstract: Complex open gas turbine cycles are analyzed by applying the heat balance method presented in Part 1 of this paper. Reheating, intercooling, regeneration, steam injection, and steam cooling are evaluated graphically to give a visual perspective of what takes place in terms of the overall heat balance when such complexities are introduced to the cycle. An example of a viable, new, intercooled regenerative cycle is given. A second example of a prototype reheat gas turbine is also included. The overall approach using the heat balance method can be applied to various cogeneration configurations when considering the more complex cycles of the future.

Heat Release Studies in a Divided-Chamber Diesel Engine

Abstract: The influences of operational parameters on the heat release and heat transfer characteristics of a divided-chamber diesel engine were examined. Increasing the fuel-air ratio increased the heat release rate, as expected, and increased the duration of combustion. Near the beginning and end of combustion the mass-burned rate was found to increase in direct proportion to an increase of engine speed. In contrast, in the central part of the combustion duration, the mass-burned rate was found to increase at a higher rate than engine speed. For motored conditions, the computed area-averaged heat-flux histories were found to be in reasonable agreement with the corresponding measured local heat-flux histories.

Wastage of In-Bed Heat Transfer Surfaces in the Pressurized Fluidized Bed Combustor at Grimethorpe

Abstract: Presentation et discussion de donnees experimentales sur les pertes metalliques des tubes du foyer de l'installation experimentale de Grimethorpe