bluuebunny/crossref_metadata_2025 huggingface dataset:
More Comprehensive Vibration Limits for Rotating Machinery
Authors: Lifshits A. , Simmons H. R. , Smalley A. J.
Published: October 2009

Vibrations are often found to be the cause of rotating machinery failures. To minimize these outages a large number of vibration criteria have been introduced by technical societies, equipment manufacturers, and experienced individuals. While useful, these vibration criteria have often been found to be contradictory and restricted to particular transducer types, machine design, or failure mechanisms. Based on this work and adding the experience accumulated by SwRI with various types of rotating equipment, more comprehensive combined vibration severity limits are established. These limits are divided into several severity regions, and cover filtered and unfiltered vibration. The appropriate correction factors are also introduced to equitably accommodate different machine designs, installations, and vibration problems. Vibration severity limits are provided for relative shaft displacement, for shaft displacement with respect to bearing clearance, and for vibration measurements taken on machine casing or bearing housing. The use of these limits is clarified by reviewing the results obtained from five field studies of actual operating equipment. Advantages, disadvantages, and use of various transducer types (proximity probes, velocity pickups, accelerometers, dual probes), as well as sources of machinery vibration (subsynchronous instabilities, resonance, imbalance, misalignment, etc.) are analyzed to assure proper application of the vibration limits.
Investigation of the Steady-State Response of a Dual-Rotor System With Intershaft Squeeze Film Damper
Authors: Li Qihan , Yan Litang , Hamilton J. F.
Published: October 2009

This paper presents an analysis of the steady-state unbalance response of a dual-rotor gas turbine engine with a flexible intershaft squeeze film damper using a simplified transfer matrix method. The simplified transfer matrix method is convenient for the evaluation of the critical speed and response of the rotor system with various supports, shaft coupling, intershaft bearing, etc. The steady-state unbalance response of the rotor system is calculated for different shaft rotation speeds. The damping effects of an intershaft squeeze film damper with different radial clearances under various levels of rotor unbalance are investigated.
Investigation of the Transient Response of a Dual-Rotor System With Intershaft Squeeze-Film Damper
Authors: Li Qihan , Hamilton J. F.
Published: October 2009

A method is presented for calculating the dynamics of a dual-rotor gas turbine engine equipped with a flexible intershaft squeeze-film damper. The method is based on the functional expansion component synthesis method. The transient response of the rotor due to a suddenly applied imbalance in the high-pressure turbine under different steady-speed operations is calculated. The damping effects of the intershaft damper and stability of the rotor system are investigated.
Perturbation Solutions for Eccentric Operation of Squeeze Film Damper Systems
Authors: Li Xuehai , Taylor D. L.
Published: October 2009

The study focuses on the effect of a small unidirectional load such as comes from imperfect balance between preloading on centering springs and gravitational load on squeeze film dampers. A rigid rotor-squeeze film damper system is considered, and a thorough study of the synchronous motion of the system is performed. Two perturbation solutions are developed: one for large speed and one for small speed. The perturbation solutions are shown to be in good agreement with numerical simulation and published experimental results.
Thermal Decomposition of Aircraft Fuel
Authors: Marteney P. J. , Spadaccini L. J.
Published: October 2009

A test program has been conducted to determine the thermal stability and heat transfer characteristics of JP-5 and several other kerosene-type fuels which vary in composition and tendency to form deposits. Tests were conducted in small-diameter, resistively heated tubes at typical aircraft engine operating conditions. A detailed mapping of the thermal decomposition characteristics of JP-5 was performed to evaluate the importance of key environmental factors—such as temperature, pressure, flowrate, and test duration—and to establish a data base for estimating the relative performance of new fuels. Tests were conducted over the temperature range 425 to 870 K for durations up to 32 hr. Fuel deposition rates varied among fuels, and the relationship between the “breakpoint temperature” (determined according to ASTM D3241) and the rate of fuel deposition was investigated.
The Autoignition and Combustion of Coal-Water Slurry Under Simulated Diesel Engine Conditions
Authors: Siebers D. L. , Dyer T. M.
Published: October 2009

The combustion characteristics of a coal-water slurry spray were examined under diesel engine conditions. A two-stage combustion process was used to simulate the diesel engine conditions in a constant-volume combustion bomb. The combustion characteristics investigated were ignition delay, ignition site, combustion development, combustion duration, and combustion completeness. The results show that the ignition delay of the coal-water slurry fuel is temperature and pressure dependent. Also, the coal slurry ignition delay is approximately a factor of five longer and the energy release rate is significantly slower in comparison to the ignition delay and energy release rate for conventional No. 2 diesel fuel. The combustion of the slurry spray was incomplete for all test conditions due to the impingement and the adherence of the coal slurry on the wall. This fundamental testing provides insight into engine design parameters which must be considered if coal-water slurry is to be used in practice.
Performance of a Stirling Engine Regenerator Having Finite Mass
Authors: Jones J. D.
Published: October 2009

The performance of a Stirling engine regenerator subjected to sinusoidal mass flow rate and pressure variation is analyzed. It is shown that cyclic variations in the temperature of the matrix due to its finite mass lead to an increase in the apparent regenerator effectiveness, but a decrease in engine power. Approximate closed-form expressions for both of these effects are deduced. The results of this analysis are compared with the predictions of a finite-element system model, and good agreement is found.
Life Assessment Technology for Combustion Turbine Blades
Authors: Viswanathan R. , Dolbec A. C.
Published: October 2009

Combustion turbine blades operating in the hot gas path are subject to degradation by embrittlement, creep, thermal fatigue, hot corrosion, and synergistic effects among the above. Development of techniques to assess the extent of degradation of the blades under these conditions can have a significant and favorable economic impact for the utility industry. The Electric Power Research Institute (EPRI) is currently engaged in a number of research activities aimed at the development of such techniques. This paper is an overview of the present and planned activities relating to life assessment technology for blades.
Thermodynamic Evaluation of Gas Turbine Cogeneration Cycles: Part I—Heat Balance Method Analysis
Authors: Rice I. G.
Published: October 2009

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.
Operating Experiences and Measurements on Turbo Sets of CCGT-Cogeneration Plants in Germany
Authors: Bammert K.
Published: October 2009

Five closed-cycle gas turbine cogeneration plants have been built and commissioned in the Federal Republic of Germany. In all cases the working fluid was air. The facilities were designed as cogeneration plants to supply electricity as well as heat to electrical and heating networks. Each of the plants accumulated more than 100,000 operating hours. One of them, which has exceeded 160,000 hours of operation, is still working. An account has already been given of the experience with the air heaters of these plants, which were fired with coal, oil, gas, or combinations of these. This paper records the experience obtained with the turbo sets.
The Effect of Thermal Matching on the Thermodynamic Performance of Gas Turbine and IC Engine Cogeneration Systems
Authors: Baughn J. W. , Bagheri N.
Published: October 2009

Computer models have been used to analyze the thermodynamic performance of a gas turbine (GT) cogeneration system and an internal combustion engine (IC) cogeneration system. The purpose of this study was to determine the effect of thermal matching of the load (i.e., required thermal energy) and the output steam fraction (fraction of the thermal output, steam and hot water, which is steam) on the thermodynamic performance of typical cogeneration systems at both full and partial output. The thermodynamic parameters considered were: the net heat rate (NHR), the power-to-heat ratio (PHR), and the fuel savings rate (FSR). With direct use (the steam fractions being different), the NHR of these two systems is similar at full output, the NHR of the IC systems is lower at partial output, and the PHR and the FSR of the GT systems are lower than those of the IC systems over the full range of operating conditions. With thermal matching (to produce a given steam fraction) the most favorable NHR, PHR, and FSR depend on the method of matching the load to the thermal output.
Parametric Analysis of Combined Gas-Steam Cycles
Authors: Cerri G.
Published: October 2009

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—see Appendix B—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°C and 1400°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.
Field Experience With Pulse-Jet Self-Cleaning Air Filtration on Gas Turbines in an Arctic Environment
Authors: Retka T. J. , Wylie G. S.
Published: October 2009

This paper discusses the results of continuous duty operation of automatic self-cleaning air filtration systems on a gas turbine application during a winter season in a North Slope Alaska arctic environment where equipment is subjected to extremely low ambient temperatures, ice fog, and blowing snow. The effects of wind direction, temperature change, and filter installation configurations relative to filter performance are discussed. Recommendations for setup and operation of self-cleaning air filters in cold weather and arctic environments are presented.
Advances in Defining a Closed Brayton Conversion System for Future ARIANE 5 Space Nuclear Power Applications
Authors: Tilliette Z. P.
Published: October 2009

The present European ARIANE space program will expand into the large ARIANE 5 launch vehicle from 1995. It is assumed that important associated missions would require the generation of 200 kWe or more in space during several years at the very beginning of the next century. For this reason, in 1983, the French C.N.E.S. (Centre National d’Etudes Spatiales) and C.E.A. (Commissariat a` l’Energie Atomique) have initiated preliminary studies of a space nuclear power system. The currently selected conversion system is a closed Brayton cycle. Reasons for this choice are given: high efficiency of a dynamic system; monophasic, inert working fluid; extensive turbomachinery experience, etc. A key aspect of the project is the adaptation to heat rejection conditions, namely to the radiator geometry which depends upon the dimensions of the ARIANE 5 spacecraft. In addition to usual concepts already studied for space applications, another cycle arrangement is being investigated which could offer satisfactory compromises among many considerations, increase the efficiency of the system, and make it more attractive as far as the specific mass (kg/kWe), the specific radiator area (m2/kWe), and various technological aspects are concerned. Comparative details are presented.
Lifetime Prediction Under Constant Load Creep Conditions for a Cast Ni-Base Superalloy
Authors: Castillo R. , Koul A. K. , Toscano E. H.
Published: October 2009

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 ε˙sm = 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 trn1 + tr) ε˙sm1 = 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.
Development of HIDEC Adaptive Engine Control Systems
Authors: Landy R. J. , Yonke W. A. , Stewart J. F.
Published: October 2009

The NASA Ames/Dryden Flight Research Facility is sponsoring a flight research program designated Highly Integrated Digital Electronic Control (HIDEC), whose purpose is to develop integrated flight-propulsion control modes and evaluate their benefits in flight on NASA F-15 test aircraft. The Adaptive Engine Control System (ADECS I) is one phase of the HIDEC program. ADECS I involves uptrimming the P&W Engine Model Derivative (EMD) PW1128 engines to operate at higher engine pressure ratios (EPR) and produce more thrust. In a follow-on phase, called ADECS II, a constant thrust mode will be developed which will significantly reduce turbine operating temperatures and improve thrust specific fuel consumption. A performance seeking control mode is scheduled to be developed. This mode features an onboard model of the engine that will be updated to reflect actual engine performance, accounting for deterioration and manufacturing differences. The onboard engine model, together with inlet and nozzle models, are used to determine optimum control settings for the engine, inlet, and nozzle that will maximize thrust at power settings of intermediate and above and minimize fuel flow at cruise. The HIDEC program phases are described in this paper with particular emphasis on the ADECS I system and its expected performance benefits. The ADECS II and performance seeking control concepts and the plans for implementing these modes in a flight demonstration test aircraft are also described. The potential payoffs for these HIDEC modes as well as other integrated control modes are also discussed.
Fatigue Crack Growth Resistance of Advanced Blade Materials
Authors: Wilson D. A. , Deluca D. P. , Cowles B. A. , Stucke M. A.
Published: October 2009

The best measure of performance in a jet engine is the thrust-to-weight ratio. Cast single-crystal superalloys provide higher temperature capability and offer opportunities for significant improvements in future jet engine performance and durability. The highly anisotropic behavior of these advanced materials, which includes modulus, strength, and ductility variation with crystallographic orientation, pose potentially significant problems for design and life prediction of advanced turbine blades. The objective of this paper is to provide a better understanding of the crack growth behavior in this advanced turbine blade material by evaluating the effect of temperature, frequency, orientation, and thickness.
Heat Release Studies in a Divided-Chamber Diesel Engine
Authors: Alkidas A. C.
Published: October 2009

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.
RANKINE: A Computer Software Package for the Analysis and Design of Steam Power Generating Units
Authors: Somerton C. W. , Brouillette T. , Pourciau C. , Strawn D. , Whitehouse L.
Published: October 2009

A software package has been developed for the analysis of steam power systems. Twenty-eight configurations are considered, all based upon the simple Rankine cycle with various additional components such as feedwater heaters and reheat legs. The package is demonstrated by two examples. In the first, the optimum operating conditions for a simple reheat cycle are determined by using the program. The second example involves calculating the exergetic efficiency of an actual steam power system.
Exergy Analysis of Combined Cycles: Part 1—Air-Cooled Brayton-Cycle Gas Turbines
Authors: El-Masri M. A.
Published: October 2009

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.
Simultaneous Heat and Mass Transfer in a Catenary Cooling Tower
Authors: Liu Yun-Yu , Hesketh H. E.
Published: October 2009

A 6-in. i.d. catenary contactor was used to evaluate the performance of this device as a new type of cooling tower. A fractional factorial statistical study facilitated the incorporation of all 21 independent variables applicable to this system. Regression models showed that the catenary behavior is analogous to and can be predicted by traditional cooling tower theory. These models also showed that an improved available coefficient based on mass transfer more accurately predicts catenary cooling tower performance. In comparison with conventional cooling towers and within the range of these data it appears that a catenary is more stable with changes in liquid-to-gas ratio, L/G, and that it can handle nearly twice the liquid and gas loadings. Catenary contactors could have a promising future in that they should also conserve space and be economical to purchase.
Experimental Investigation of Gas Turbine Recuperator Fouling
Authors: Bowen T. L. , Guimond D. P. , Muench R. K.
Published: October 2009

This paper discusses an experimental investigation of recuperator fouling currently underway at the David Taylor Naval Ship Research and Development Center. The overall approach involves testing different heat exchangers in the exhaust gas stream of a gas turbine. The two heat exchangers initially tested were the plate-fin type and differed in the gas-side heat transfer surface geometry. Primary surface heat exchangers are being considered for future tests also. Test conditions are defined such that the critical part of full-scale recuperators (i.e., the colder end of the gas passages) is simulated in the small test heat exchangers. The composition of the gas stream is measured to determine amounts of gaseous, particulate, and condensible hydrocarbon emissions. Fuel samples taken during each test are analyzed. The test heat exchangers are specially constructed to allow inspection and measurement of the fouling film inside the unit following each test. The temperature distribution inside the test exchanger is measured, as well as air and gas inlet and exit temperatures. Measurements of fouling film thickness are made using an optical microscope and photographs of fouling deposits were taken. The early results obtained from fouling tests conducted with the first heat exchanger are discussed. Tests were also conducted to demonstrate a fouling removal technique.
NDE Reliability and Process Control for Structural Ceramics
Authors: Baaklini G. Y.
Published: October 2009

The reliability of microfocus x-radiography and scanning laser acoustic microscopy for detecting microvoids in silicon nitride and silicon carbide was statistically evaluated. Materials and process-related parameters that influenced the statistical findings in research samples are discussed. The use of conventional x-radiography in controlling and optimizing the processing and sintering of an Si3N4-SiO2-Y2O3 composition designated NASA 6Y is described. Radiographic evaluation and guidance helped develop uniform high-density Si3N4 modulus-of-rupture bars with improved four-point flexural strength (857, 544, and 462 MPa at room temperature, 1200°C, and 1370°C, respectively) and reduced strength scatter.
Tensile Behavior of Glass/Ceramic Composite Materials at Elevated Temperatures
Authors: Mandell J. F. , Grande D. H. , Jacobs J.
Published: October 2009

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.
Mixed-Mode Fracture Criteria for Reliability Analysis and Design With Structural Ceramics
Authors: Shetty D. K.
Published: October 2009

Increasing use of ceramics in structural applications has led to the development of a probabilistic design methodology that combines three elements: linear elastic fracture mechanics theory that relates strengths of ceramics to size, shape, and orientation of critical flaws, a characteristic flaw size distribution function that accounts for the size effect on strength via the weakest-link concept, and a time-dependent strength caused by subcritical crack growth or other mechanisms. This paper reviews recent research that has been focused on the first of the above three elements, the investigation of fracture criteria for arbitrarily oriented flaws in ceramics, i.e., the mixed-mode fracture problem in linear elastic fracture mechanics theory. Experimental results obtained with two-dimensional through cracks and three-dimensional surface (indentation) cracks are summarized and compared to mixed-mode fracture criteria. The effects of material microstructure and the stress state on mixed-mode fractures are discussed. The application of mixed-mode fracture criteria in reliability analysis is illustrated for several simple stress states in the absence of time-dependent strength degradation.
Wastage of In-Bed Heat Transfer Surfaces in the Pressurized Fluidized Bed Combustor at Grimethorpe
Authors: Anderson J. S. , Carls E. L. , Mainhardt P. J. , Swift W. M. , Wheeldon J. M. , Brooks S. , Minchener A. J. , Stringer J.
Published: October 2009

The wastage of in-bed heat transfer surfaces has recently emerged as a potentially serious problem for both pressurized and atmospheric fluidized bed combustors. The experimental pressurized fluidized bed combustion facility at Grimethorpe has accumulated a considerable quantity of data covering the wastage of in-bed tubes obtained during a total of just over 3600 h of operation. The combustor operated with different tube banks, with some degree of wastage being experienced with each one. The data are described, evidence for possible solutions is presented, and plans for future tests at Grimethorpe to prove these solutions are outlined.
ITSL Coal Liquid as a Combustion Turbine Fuel
Authors: Rieke K. L. , Lew H. G. , Rovesti W. C.
Published: October 2009

The combustion characteristics of low-hydrogen-content distillate fuels produced from coal differ from those of conventional petroleum distillates. The differences include: increased flame emissivity which contributes to higher combustor liner temperature, and increased fuel-bound nitrogen which contributes to higher NOx emission. This paper presents the results of a laboratory test program to evaluate the emissions and combustor performance characteristics when burning the ITSL heavy distillate coal-derived liquid (CDL), and thus determine its acceptability and suitability as a utility combustion turbine fuel. The chemical and physical properties characterizing the test fuel were determined. The trace metals, such as sodium, potassium, vanadium, etc., are low and within concentrations presently allowable in fuel oil specifications. The burner performance factors on the CDL fuel did not differ significantly from those of the baseline No. 2 fuel. Evaluation and comparison of combustor wall temperatures when burning ITSL showed the increase in wall temperature (above No. 2 fuel) to be consistent with expectations. Emissions were measured over an equivalent load range of 30 to 100 percent engine base load. The increase in the measured NOx emissions with increasing combustor temperature rise (load) was observed. The usual reduction of NOx with water injection into the combustor was also observed. Other emissions, such as CO, UHC, O2, and CO2 for the ITSL fuel generally followed the usual characteristics with load. The ITSL Heavy distillate was found to be an acceptable coal-derived liquid fuel for combustion turbine applications.
Combustion of Coal/Water Mixtures With Thermal Preconditioning
Authors: Novack M. , Roffe G. , Miller G.
Published: October 2009

Thermal preconditioning is a process in which coal/water mixtures are vaporized to produce coal/steam suspensions, and then superheated to allow the coal to devolatilize producing suspensions of char particles in hydrocarbon gases and steam. This final product of the process can be injected without atomization, and burned directly in a gas turbine combustor. This paper reports on the results of an experimental program in which thermally preconditioned coal/water mixture was successfully burned with a stable flame in a gas turbine combustor test rig. Tests were performed at a mixture flowrate of 300 lb/hr and combustor pressure of 8 atm. The coal/water mixture was thermally preconditioned and injected into the combustor over a temperature range from 350°F to 600°F, and combustion air was supplied at between 600°F to 725°F. Test durations varied between 10 and 20 min. Major results of the combustion testing were that: A stable flame was maintained over a wide equivalence ratio range, between φ = 2.2 (rich) and 0.2 (lean); and combustion efficiency of over 99 percent was achieved when the mixture was preconditioned to 600°F and the combustion air preheated to 725°F. Measurements of ash particulates, captured in the exhaust sampling probe located 20 in. from the injector face, show typical sizes collected to be about 1 μm, with agglomerates of these particulates to be not more than 8 μm. The original mean coal particle size for these tests, prior to preconditioning, was 25 μm. Results of additional tests showed that one third of the sulfur contained in the solids of a coal/water mixture with 3 percent sulfur was evolved in gaseous form (under mild thermolized conditions) mainly as H2S with the remainder as light mercaptans.
Combustion and Deposition in Coal-Fired Turbines
Authors: Kimura S. G. , Spiro C. L. , Chen C. C.
Published: October 2009

Combustion and deposition behavior of coal in the form of highly beneficiated coal-water mixtures (CWM) has been investigated. The solids content of the CWM fuels was typically 50 percent, with a mean coal particle size of 4 μm and an ash content of 0.8 percent (dry). Combustion efficiencies in excess of 99.5 percent based on the carbon content of the collected ash were achieved in gas turbine-type can combustors with residence times of less than 20 ms with up to 25 percent (Btu basis) supplemental fuel oil assist. Ash deposition rates on a first-stage turbine nozzle sector were measured and were found to be much lower than would have been predicted from residual petroleum fuel experience because of differences in ash chemistry, and thus, deposition mechanism.
Acoustical Resonance Measurement of Particle Loading in Gas-Solids Flow
Authors: Vetter A. A. , Culick F. E. C.
Published: October 2009

The measurement of the frequency of transverse acoustical resonances of a duct can determine the mass loading and size of particles fluidized by a gas phase. A first-order perturbation-iteration acoustical analysis is applied to this two-phase flow measurement, termed the Acoustical Resonance Measurement, in a circular duct. A sample application of pulverized coal fluidized by air in power plant coal piping is examined. The particle loading is determined by measuring the frequency of a single transverse resonance, and the particle size is determined by simultaneously measuring the frequencies of two transverse resonances. The Acoustical Resonance Measurement provides a nonintrusive and real-time measurement of the mass loading and sizing of particles fluidized by a gas phase.
Partially Stabilized Zirconia Piston Bowl Reliability
Authors: Hartsock D. L.
Published: October 2009

The Weibull based “Simplified Structural Ceramic Design Technique” [1] was used to calculate the reliability of a partially stabilized zirconia (PSZ) piston bowl design. The details of the method and a set of sample calculations are presented. Test results of the piston bowl showed cracks in regions which had a high calculated probability of failure. In addition cracks developed in a region of high compressive/shear stress. Since Weibull reliability analysis only uses tensile stresses this area did not have a high calculated probability of failure. Several hypotheses are presented for the mode of failure in this region. The simplified technique was used to predict what the necessary material properties would have to be for successful PSZ insert of the design shown.
Materials and Surface Finish Effects in the Breaking-in Process of Engines
Authors: Barber G. C. , Lee J. C. , Ludema K. C.
Published: October 2009

In this investigation, three materials and several surface finishes on cylinder walls were compared in laboratory tests that simulate the running-in behavior of 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 did gray iron, but their “normal” wear behavior and midstroke friction performance were about the same as gray iron.
Development of the B2400 Engine
Authors: Dunton R. M. , Propetto L. , Murray G. E.
Published: October 2009

A new engine has been designed to meet future requirements for heavy-duty locomotive applications as found in North America and developing countries. After a thorough analysis of future market requirements, a detailed specification was prepared to serve as guideline throughout the evaluation of the design. Objectives were established for many fundamental parameters including efficiency, introductory and growth power ratings, weight and package size, durability, and maintainability. The paper describes the engine configuration, detail design, and the significant use of computer analytical techniques, to provide increased levels of performance in the integrity of the crankshaft, cylinder block, and other key components. In addition, reference to many years’ experience with an existing locomotive engine design has provided assurance of the reliability of many of the new components. Design details are included for many components, with descriptions of the rationale behind those designs.
Comparing Expanders for Direct Recovery of Exhaust Energy From a Low-Heat-Rejection Diesel
Authors: Amann C. A.
Published: October 2009

Part-load performance of a compound low-heat-rejection (LHR) engine is estimated at constant speed. The engine consists of an LHR diesel reciprocator geared to a supercharging compressor and an exhaust expander. Two classes of expander differing substantially in both flow characteristics and energy-extraction principles are ranked: aerodynamic (reaction turbine) and positive-displacement (internal expansion). To focus the comparison on differences in fundamental expander characteristics rather than differences in efficiency levels among specific samples of each type of expander, each is assigned an efficiency of 100 percent at its best-efficiency point. Although differences in fundamental characteristics between the expanders were sufficient to rank them on a performance basis, these differences were largely overshadowed by the magnitude of the indicated work developed in the reciprocator relative to the work developed by the expander.
Application of Several Variable-Valve-Timing Concepts to an LHR Engine
Authors: Morel T. , Keribar R. , Sawlivala M. , Hakim N.
Published: October 2009

An analytical study was made of advantages provided by electronically controlled hydraulically activated valves when applied to a low heat rejection engine with and without exhaust heat recovery devices. The valves, which could be designed to operate with variable timings and variable rates of opening and closing, would allow the use of certain sophisticated valve strategies not possible with conventional systems. Three individual investigations were carried out. The first concerned the optimization of the timing and rate of valve opening at several speeds and loads, to obtain maximum volumetric efficiency and lowest BSFC. A second investigated early intake valve closing (IVC before BDC), coupled with increased boost, a concept that had been suggested previously in the literature. The present results showed much lower benefits than those predicted by the earlier study. The final study addressed the use of an organic Rankine cycle bottomer (ORCB) to extract energy from the exhaust stream and directing the ORCB output power to the engine air compressor shaft rather than to the engine output shaft. At rated engine conditions, when not employing a power turbine, this concept was found to produce higher BSFC compared to the more standard configuration where the ORBC was directly coupled to the engine shaft. When a power turbine was used between the engine and the ORCB, nearly the same BSFC was achieved with the two configurations.
Tests of Thick Flame Combustion Estimates in a Single-Cylinder Engine
Authors: Boisvert J. , Hill P. G.
Published: October 2009

Estimates of turbulent burning speed, burning zone thickness, and randomness of ignition delay have been incorporated in a model of spark-ignited engine combustion. The estimates have been made on the assumption that turbulence during combustion is homogeneous, isotropic, and has Tennekes’ small-scale structure with integral length scale proportional to chamber height. Flame propagation rate has been assumed to depend on turbulence intensity in accord with Chomiak’s vortex-bursting hypothesis. The resulting method of calculating combustion has been tested with cylinder pressure data from a Ricardo single-cylinder engine over a wide range of rpm and equivalence ratio and operating with natural gas fuel. Hot-wire measurements of turbulence intensity were made in the motored engine, but window-averaged estimates of intensity were a factor of two lower than ensemble-averaged estimates. Given a factor of two uncertainty in the turbulence intensity measurements it can be said that estimates of combustion duration and pressure agreed well with experimental data over the range of speed and equivalence ratio. The sensitivity of the calculation method to alterations in assumed parameters has been tested. The most important uncertainty appears to be the turbulence intensity.
Progress Toward Life Modeling of Thermal Barrier Coatings for Aircraft Gas Turbine Engines
Authors: Miller R. A.
Published: October 2009

Progress toward developing life models for simulating the behavior of thermal barrier coatings in aircraft gas turbine engines is discussed. A preliminary laboratory model is described as are current efforts to develop engine-capable models. Current understanding into failure mechanisms is also summarized.
Maintaining Low Exhaust Emissions With Turbocharged Gas Engines Using a Feedback Air–Fuel Ratio Control System
Authors: Eckard D. W. , Serve´ J. V.
Published: October 2009

Maintaining low exhaust emissions on a turbocharged, natural gas engine through the speed and load range requires precise control of the air–fuel ratio. Changes in ambient conditions or fuel heating value will cause the air–fuel ratio to change substantially. By combining air–gas pressure with preturbine temperature control, the air–fuel ratio can be maintained regardless of changes in the ambient conditions or the fuel’s heating value. Design conditions and operating results are presented for an air–fuel controller for a turbocharged engine.
Swirl and Counterswirl Effects in Prefilming Airblast Atomizers
Authors: Aigner M. , Wittig S.
Published: October 2009

The performance characteristics of prefilming airblast atomizers depend largely on the shear stresses in each of the two air supply channels. As an extension of previously reported results, experiments were conducted using an atomizer model with separately controlled air ducts and typical prototype nozzles. It was shown that the quality of atomization can be limited due to internal droplet formation. However, the velocity profiles of the atomization air and the properties of the liquid are the dominant parameters that determine the drop-size distribution generated at the atomization edge. The shear flow at the nozzle exit and the recirculation zone depend largely on the swirl or counterswirl of the exiting air. Correlations have been obtained between the spray characteristics and the relevant parameters.
Improved 12 Percent Cr Rotor Forgings for Advanced Steam Turbines
Authors: Ito F. , Kuwabara K. , Miyazaki M. , Fukui Y. , Takeda Y.
Published: October 2009

For future advanced steam turbines of 4500 psi and 1100°F, a high-temperature rotor is one of the most important components to be developed. We estimated that the usable temperature limit of existing 12Cr steel was approximately 1075°F, and then developed improved 12Cr steels. Prototype rotors were made from three types of developed steels, and were put to various evaluation tests. All three steels had creep-rupture strength exceeding that of existing 12Cr steels and were satisfactory in quality and in the other mechanical properties.
Pack Cementation Coatings for Superalloys: A Review of History, Theory, and Practice
Authors: Goward G. W. , Cannon L. W.
Published: October 2009

Nickel and cobalt-base superalloy blades and vanes in the hot sections of all gas turbines are coated to enhance resistance to hot corrosion. Pack cementation aluminizing, invented in 1911, is the most widely used coating process. Corrosion resistance of aluminide coatings can be increased by modification with chromium, platinum, or silicon. Chromium diffusion coatings can be used at lower temperatures. Formation and degradation mechanisms are reasonably well understood and large-scale manufacturing processes for these coatings are gradually being automated. Pack cementation and related diffusion coatings serve well for most aircraft engine applications. The trend for industrial and marine engines is more toward the use of overlay coatings because of the greater ease of designing these to meet a wide variety of corrosion conditions.
The United Kingdom Engine Technology Demonstrator Program
Authors: Chrispin W. J.
Published: October 2009

It is generally accepted that development time scales for civil and military aero-engines can exceed those of the airframe they will power. It is now essential to ensure that relevant engine technologies are conceived and proven ahead of commitment to full-scale engine development if future military and civil propulsion requirements are to be met in an affordable way. The scope and scale of UK demonstrator activity has been greatly expanded in recent years in recognition of this need, principally through increased government funding. This paper discusses the principles underlying technology demonstration including the circumstances pertaining in the UK, concluding that a comprehensive program of technology demonstration conducted in a step-by-step fashion and properly integrated with transition to full-scale engineering development will produce significant financial and operational benefits.
Introduction and Application of the General Electric Turbine Engine Monitoring Software Within KLM Royal Dutch Airlines
Authors: Lucas H. , Paas J. E.
Published: October 2009

KLM Royal Dutch Airlines has been using the General Electric ground-based engine monitoring (GEM) system for the CF6-50 and CF6-80 engines for several years. During the last year, various additional elements of the monitoring system have been introduced to the maintenance departments and are currently operational. This paper describes the introduction and the application of the GEM system within KLM’s organization. Also some attention is given to the (potential) benefits that are related to the use of this system, as well as to KLM’s engine monitoring plans for the near future.
Conceptual Design of an Optic-Based Engine Control System
Authors: Davies W. J. , Baumbick R. A. , Vizzini R. W.
Published: October 2009

Advanced integrated flight and propulsion control systems may require the use of optic technology to provide enhanced electromagnetic immunity and reduced weight. Immunity to electromagnetic interference and pulses is required for integrated systems where flight and propulsion control systems communicate with each other and diverse systems located throughout a composite aircraft. Weight reduction is crucial to the complex engine control systems required for advanced engines incorporating diagnostics, variable geometry and vectoring/reversing exhaust nozzles. A team of Pratt & Whitney, McDonnell Aircraft, Hamilton Standard, and United Technologies Research Center have developed the conceptual design of an optic engine control system, under a contract from NASA Lewis, entitled Fiber Optic Control System Integration (FOCSI). FOCSI is a triservice/NASA joint program designed to provide the optic technology requirements for advanced fighter/attack aircraft.
Gas Turbine Fuel Control Systems for Unmanned Applications
Authors: Harrison R. A. , Yates M. S.
Published: October 2009

The technique of controlling engine acceleration has made possible gas turbine controls with simple hydromechanics and a minimal number of inputs into the electronics. This paper describes a control and electrical power generation system developed for an unmanned aircraft gas turbine, and the results obtained from the development engine running carried out with it.
Heat Transfer in Stepped Labyrinth Seals
Authors: Wittig S. , Jacobsen K. , Schelling U. , Kim S.
Published: October 2009

Leakage flow and heat transfer of scaled-up stepped labyrinth seals were investigated experimentally and numerically. The experiments were conducted in a test rig under steady conditions. For different geometries and pressure ratios a finite element program was used to determine the temperature distribution and subsequently the heat transfer coefficients. In verifying the experimental results, the flow field of the seals was calculated numerically by a finite difference program. Heat transfer coefficients were derived utilizing the well-known analogies between heat transfer and wall friction.
Windage Rise and Flowpath Gas Ingestion in Turbine Rim Cavities
Authors: Haaser F. , Jack J. , McGreehan W.
Published: October 2009

Typically cooling air must be metered into cavities bordering turbine disks to offset cavity air temperature rise due to windage generated by air drag from rotating and stationary surfaces and the ingestion of hot mainstream gas. Being able to estimate the minimum amount of cooling air required to purge turbine rim cavities accurately is important toward providing optimum turbine cycle performance and hardware durability. Presented is an overview of a method used to model windage rise and ingestion on a macroscopic scale. Comparisons of model results to engine test data are included.