Showing papers in "Journal of Engineering for Gas Turbines and Power-transactions of The Asme in 1994"

Exergy Analysis: Principles and Practice

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

The Evolution of Thermal Barrier Coatings in Gas Turbine Engine Applications

Abstract: Thermal barrier coatings (TBCs) have been used for almost three decades to extend the life of combustors and augmentors and, more recently, stationary turbine components Plasma-sprayed yttria-stabilized zirconia TBC currently is bill-of-material on many commercial jet engine parts A more durable electron beam-physical vapor deposited (EB-PVD) ceramic coating recently has been developed for more demanding rotating as well as stationary turbine components This ceramic EB-PVD is bill-of-material on turbine blades and vanes in current high thrust engine models and is being considered for newer developmental engines as well To take maximum advantage of potential TBC benefits, the thermal effect of the TBC ceramic layer must become an integral element of the hot section component design system To do this with acceptable reliability requires a suitable analytical life prediction model calibrated to engine experience The latest efforts in thermal barrier coatings are directed toward correlating such models to measured engine performance

Development of an Aeroderivative Gas Turbine Dry Low Emissions Combustion System

Abstract: This paper gives the development status of GE’s new aeroderivative premixed combustion system. This system consists of a new fuel staged annular combustor, compressor rear frame, first-stage turbine nozzle, electronic staging controller, and fuel delivery system. Component test results along with a description of the combustion system are presented. This new system will reduce NOx emissions by 90 percent relative to the original aircraft engine combustion system while maintaining low emissions of CO and UHCs. Tests of a LM6000 gas turbine equipped with the new system are planned for early 1994.

TEMPER - A gas-path analysis tool for commercial jet engines

Abstract: Almost from the inception of the gas turbine engine, airlines and engine manufacturers have sought an effective technique to determine the health of the gas-path components (fan, compressors, combustor, turbines) based on available gas-path measurements. The potential of such tools to save money by anticipating the need for overhaul and providing help in work scope definition is substantial, provided they produce reliable results. This paper describes a modern gas-path analysis tool (GE’s TEMPER1 program), discusses the benefits and problems experienced by current TEMPER users, and suggests promising research areas that may lead to an improved algorithm.Copyright © 1992 by ASME

GETRAN: A Generic, Modularly Structured Computer Code for Simulation of Dynamic Behavior of Aero- and Power Generation Gas Turbine Engines

Abstract: The design concept, the theoretical background essential for the development of the modularly structured simulation code GETRAN, and several critical simulation cases are presented in this paper. The code being developed under contract with NASA Lewis Research Center is capable of simulating the nonlinear dynamic behavior of single- and multispool core engines, turbofan engines, and power generation gas turbine engines under adverse dynamic operating conditions. The modules implemented into GETRAN correspond to components of existing and new-generation aero- and stationary gas turbine engines with arbitrary configuration and arrangement. For precise simulation of turbine and compressor components, row-by-row diabatic and adiabatic calculation procedures are implemented that account for the specific turbine and compressor cascade, blade geometry, and characteristics. The nonlinear, dynamic behavior of the subject engine is calculated solving a number of systems of partial differential equations, which describe the unsteady behavior of each component individually. To identify each differential equation system unambiguously, special attention is paid to the addressing of each component. The code is capable of executing the simulation procedure at four levels, which increase with the degree of complexity of the system and dynamic event. As representative simulations, four different transient cases with single- and multispool thrust and power generation engines were simulated. These transient cases vary from throttling the exit nozzle area, operation with fuel schedule, rotor speed control, to rotating stall and surge.

An Assessment of Weighted-Least-Squares-Based Gas Path Analysis

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

Chaotic Behavior of Rotor/Stator Systems With Rubs

Abstract: This paper outlines the dynamic behavior of externally excited rotor/stator systems with occasional, partial rubbing conditions. The observed phenomenon have one major source of a strong nonlinearity: transition from no contact to contact state between mechanical elements, one of which is rotating. This results in variable stiffness and damping, impacting, and intermittent involvement of friction. A new model for such a transition (impact) is developed. In case of the contact between rotating and stationary elements, it correlates the local radial and tangential ("super ball") effects with global behavior of the system. The results of numerical simulations of a simple rotor/stator system based on that model are presented in the form of bifurcation diagrams, rotor lateral vibration time—base waves, and orbits. The vibrational behavior of the considered system is characterized by orderly harmonic and subharmonic responses, as well as by chaotic vibrations. A new result (additional subharmonic regime of vibration) is obtained for the case of heavy rub of an anisotropically supported rotor. The correspondence between numerical simulation and previously obtained experimental data supports the adequacy of the new model of impact.

Modeling and Analysis of Gas Turbine Performance Deterioration

Abstract: The effects of performance deterioration in both land and aircraft gas turbines are presented in this paper. Models for two of the most common causes of deterioration, viz., fouling and erosion, are presented. A stage-stacking procedure, which uses new installed engine field data for compressor map development, is described. The results of the effect of fouling in a powerplant gas turbine and that of erosion in a aircraft gas turbine are presented. Also described are methods of fault threshold quantification and fault matrix simulation. Results of the analyses were found to be consistent with field observations.

Models for predicting the performance of Brayton-cycle engines

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

Analysis of a Basic Chemically Recuperated Gas Turbine Power Plant

Abstract: This paper investigates a basic'' Chemically Recuperated Gas Turbine (a basic'' CRGT is defined here to be one without intercooling or reheat). The CRGT is of interest due to its potential for ultralow NO[sub x] emissions. A computer code has been developed to evaluate the performance characteristics (thermal efficiency and specific work) of the Basic CRGT, and to compare it to the steam-injected gas turbine (STIG), the combined cycle (CC) and the simple cycle gas turbine (SC) using consistent assumptions. The CRGT model includes a methane-steam reformer (MSR), which converts a methane-steam mixture into a hydrogen-rich fuel using the waste'' heat in the turbine exhaust. Models for the effects of turbine cooling air, variable specific heats, and the real gas effects of steam are included. The calculated results show that the Basic CRGT has a thermal efficiency higher than the STIG and simple cycles not quite as high as the combined cycle.

Optimal Sizing of a Gas Turbine Cogeneration Plant in Consideration of Its Operational Strategy

Abstract: An optimal planning method is proposed for the fundamental design of cogeneration plants Equipment capacities and utility maximum demands are determined so as to minimize the annual total cost in consideration of the plants’ annual operational strategies for the variations of both electricity and thermal energy demands These sizing and operational planning problems are formulated as a nonlinear programming problem and a mixed-integer linear programming problem, respectively They are solved efficiently in consideration of their hierarchical relationship by a penalty method A numerical example about a gas turbine plant is given to ascertain the validity and effectiveness of the proposed method

Influence of High Rotational Speeds on Heat Transfer and Oil Film Thickness in Aero-Engine Bearing Chambers

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

Transient phenomena in compressor stations during surge

Abstract: Transient phenomena are generally inherent in the operation of compressor stations: These are either fast or slow transients. A model describing the governing equation for the gas dynamics, control system, compressor and turbine shaft inertias has been developed. The effect of these inertias is manifested by an example of a compressor station operating near the surge control line. Another example deals with a station that has a cooler placed in the recycle path. This alters the rate at which the compressor shaft decelerates upon shutdown and may cause backward spinning depending on the relative magnitude of the shaft inertia with respect to the cooler volume. Backward spinning of compressor shaft has detrimental effects on dry seals and is undesirable. It was found that by keeping the recycle value closed upon shutdown, the rate of shaft deceleration will be reduced.

Thermal Fracture of Multilayer Ceramic Thermal Barrier Coatings

Abstract: Controlled experiments and a corresponding analytical model were developed to investigate the reasons for crack initiation in multilayer ceramic thermal barrier coatings. The experiments and model determined that surface cracks form as a result of tensile stresses created following stress relaxation in the ceramic at steady-state high temperatures (about 900°C–1100°C). Interface cracks generated by out-of-plane stresses are affected by the presence of these surface cracks and thermal transients and, possibly, edge effects.

Fault Diagnosis in Gas Turbines Using a Model-Based Technique

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

Performance Evaluation of Low Heat Rejection Engines

Abstract: Improving the performance of the Chinese B135 six-cylinder direct injection turbocharged and turbocompounded Low Heat Rejection Engine (LHRE) was based on experimental and analytical studies. The studies were primarily applied on a B1135 single-cylinder LHR engine and a conventional water-cooled B1135 single-cylinder engine. Performance of the B1135 LHRE was worse than that of the conventional B1135 due to a deterioration in the combustion process of the B1135 LHRE. The combustion process was improved and the fuel injection system was redesigned and applied to the B135 six-cylinder LHRE. The new design improved the performance of the LHRE and better fuel economy was realized by the thermal energy recovered from the exhaust gases by the turbocompounding system.

Three-dimensional vibration analysis of rotating laminated composite blades

Abstract: This work offers the first known three-dimensional continuum vibration analysis for rotating, laminated composite blades A cornerstone of this work is that the dynamic energies of the rotating blade are derived from a three-dimensional elasticity based, truncated quadrangular pyramid model incorporating laminated orthotropicity, full geometric nonlinearity using an updated Lagrangian formulation and Coriolis acceleration terms These analysis sophistications are included to accommodate the nonclassical directions of modern blade designs comprising thin, wide chord-lifting surfaces of laminated composite construction The Ritz method is used to minimize the dynamic energies with displacements approximated by mathematically complete polynomials satisfying the vanishing displacement conditions at the blade root section exactly Several tables and graphs are presented that describe numerical convergence studies showing the validity of the assumed displacement polynomials used herein Nondimensional frequency data are presented for various rotating, truncated quadrangular pyramids, serving as first approximations of practical blades employed in aircraft engines and fans A wide scope of results explain the influence of a number of parameters coined to rotating, laminated composite blade dynamics, namely aspect ratio (a/b), chord ratio (c/b), thickness ratio (b/h), variable thickness distribution (h[sub l]/h[sub t]), blade pretwist angle ([phi][sub 0]), composite fiber orientation angle ([theta]), and angular velocitymore » ([Omega]) Additional examples are given that elucidate the significance of the linear and nonlinear kinematics used in the present three-dimensional formulation along with the importance of the Coriolis acceleration terms included in the analysis« less

Infrared signature suppression for marine gas turbines: comparison of sea trial and model test results for the DRES ball IRSS system

Abstract: Sea Trials have recently been underway for Canada's new City Class Patrol Frigate (CFP). These trails provided the first opportunity to measure the performance of the new DRES Ball Infrared Signature Suppression (IRSS) system installed on a ship. This paper presents a comparison between the 1/4 scale hot flow model test results with the full-scale sea trial results. Performance variables included in the comparison are : metal surface temperatures, back pressure, plume temperature distribution and surface static pressures.

Performance and economic enhancement of cogeneration gas turbines through compressor inlet air cooling

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

Study on the Turbine Vane and Blade for a 1500°C Class Industrial Gas Turbine

Abstract: This paper describes the summary of a three year development program for the first stage stationary vane and rotating blade for the next generation, 1,500 C class, high efficiency gas turbine. In such a high temperature gas turbine, the first turbine vane and blade are the most important hot parts. Full-coverage film cooling (FCFC) is adopted for the cooling scheme, and directionally solidified (DS) nickel base superalloy and thermal barrier coating (TBC) will be used to prolong the creep and thermal fatigue life. The concept of the cooling configuration, fundamental cascade test results, and material test results will be presented.

1993 Soichiro Honda Lecture: The Challenges of Change in the Auto Industry: Why Alternative Fuels?

Abstract: Development of vehicles to operate on nonpetroleum fuels began in earnest in response to the energy shocks of the 1970s. While petroleum will remain the predominant transportation fuel for a long time, petroleum supplies are finite, so it is not too soon to begin the difficult transition to new sources of energy. In the past decade, composition of the fuel utilized in the internal combustion engine has gained recognition as a major factor in the control of emissions from the tailpipe of the automobile and the rate of formation of ozone in the atmosphere. Improvements in air quality can be realized by using vehicles that operate on natural gas, propane, methanol, ethanol, or electricity, but introduction of these alternative fuel vehicles presents major technical and economic challenges to the auto industry, as well as the entire country, as long as gasoline remains plentiful and inexpensive.

Low emissions combustor development for an industrial gas turbine to utilize LCV fuel gas

Abstract: Advanced coal-based power generation systems such as the British Coal Topping Cycle offer the potential for high-efficiency electricity generation with minimum environmental impact. An important component of the Topping cycle program is the gas turbine, for which development of a combustion system to burn low calorific value coal derived fuel gas, at a turbine inlet temperature of 1,260 C (2,300 F), with minimum pollutant emissions, is a key R and D issue. A phased combustor development program is underway burning low calorific value fuel gas (3.6--4.1 MJ/m[sup 3]) with low emissions, particularly NO[sub x] derived from fuel-bound nitrogen. The first phase of the combustor development program has now been completed using a generic tubo-annular, prototype combustor design. Tests were carried out at combustor loading and Mach numbers considerably greater than the initial design values. Combustor performance at these conditions was encouraging. The second phase of the program is currently in progress. This will assess, initially, an improved variant of the prototype combustor operating at conditions selected to represent a particular medium sized industrial gas turbine. This combustor will also be capable of operating using natural gas as an auxiliary fuel, to suite the start-up procedure for the Topping Cycle. Themore » paper presents the Phase 1 test program results for the prototype combustor. Design of the modified combustor for Phase 2 of the development program is discussed, together with preliminary combustor performance results.« less

Microstructural Investigations of Plasma-Sprayed Yttria Partially Stabilized Zirconia TBC (In Relation to Thermomechanical Resistance and High-Temperature Oxidation Mechanisms)

Abstract: This study deals with microstructural investigations of plasma-sprayed yttria partially stabilized zirconia thermal barrier coatings, performed by classical and analytical transmission electron microscopy. The aim of the study was to determine eventual relationships between coating microstructure and toughness. The ceramic/metal interface, which plays an important role during TBC thermomechanical solicitation, has also been studied. In the 6--8 wt. percent Y[sub 2]O[sub 3] range, the metastable tetragonal t[prime] phase is observed, showing special faulted microstructural features, such as grain twinning and antiphase boundary planes. Moreover, after high-temperature annealing in air, a very fine and stable precipitation of the equilibrium cubic phase appears. It is believed that these microstructural elements could act as crack deviation sites and enhance the coatings' intrinsic toughness. Microstructural investigations of the alumina scales grown during high-temperature annealing reveal yttrium segregation at oxide grain boundaries as well as significant quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain boundary oxygen diffusion mechanism. The presence of zirconium inside the alumina grains suggests that Al[sub 2]O[sub 3] also partially forms by chemical reduction of ZrO[sub 2] by Al.

On Curve Veering and Flutter of Rotating Blades

Abstract: The eigenvalues of rotating blades usually change with rotation speed according to the Stodola-Southwell criterion. Under certain circumstances, the loci of eigenvalues belonging to two distinct modes of vibration approach each other very closely, and it may appear as if the loci cross each other. However, our study indicates that the observable frequency loci of an undamped rotating blade do not cross, but must either repel each other (leading to “curve veering”), or attract each other (leading to “frequency coalescence”). Our results are reached by using standard arguments from algebraic geometry—the theory of algebraic curves and catastrophe theory. We conclude that it is important to resolve an apparent crossing of eigenvalue loci into either a frequency coalescence or a curve veering, because frequency coalescence is dangerous since it leads to flutter, whereas curve veering does not precipitate flutter and is, therefore, harmless with respect to elastic stability.

An infrared pyrometry system for monitoring gas turbine blades - Development of a computer model and experimental results

Abstract: This work describes the development of a computer modeling system for infrared pyrometry measurement of gas turbine blade temperature. The model accurately evaluates apparent target emissivity and temperature on the basis of the radiation heat fluxes exchanged at steady-state conditions. Experimental testing conducted on gas turbine models in a controlled-temperature furnace has shown that the reliability of the target emissivity prediction effectively reduces one of the major causes of error in infrared pyrometry.

Development of Gas Turbine Steam Injection Water Recovery (SIWR) System

Abstract: This paper describes and discusses a “closed-loop” steam injection water recovery (SIWR) cycle that was developed for steam-injected gas turbine applications. This process is needed to support gas turbine steam injection especially in areas where water cannot be wasted and complex water treatment is discouraged. The development of the SIWR was initiated by NOVA in an effort to reduce the environmental impact of operating gas turbines and to find suitable solutions for its expanding gas transmission system to meet future air emission restrictions. While turbine steam injection provides many benefits, it has not been considered for remote, less supported environments such as gas transmission applications due to its high water consumption. The SIWR process can alleviate this problem regardless of the amount of injection required. The paper also covers conceptual designs of a prototype SIWR system on a small gas turbine unit. However, because of relatively high costs, it is generally believed that the system is more attractive to larger size turbines and especially when it is used in conjunction with cogeneration or combined cycle applications.

Numerical Analysis Versus Experimental Investigation of a Distributor-Type Diesel Fuel-Injection System

Abstract: A production distributor-type fuel-injection system for diesel engines has been extensively investigated via computer-assisted simulation and experimentation. The investigation was mainly aimed at assessing and validating a sophisticated computational model of the system, developed with specific attention given to the pump and to some important aspects concerning the injection pressure simulation, such as the dynamic effects of the injector needle lift, the flow unsteadiness, and compressibility effects on the nozzle-hole discharge coefficient. The pump delivery assembly was provided with a valve of the reflux type. This presented a flat in the collar, forming a return-flow restriction with the seat, and had no retraction piston. A single-spring injector, with a reduced sac volume, was fitted to the system. The numerical analysis of transient flow phenomena linked to the mechanical unit dynamics, including possible cavitation occurrence in the system, was performed using an implicit finite-difference algorithm, previously set up for in-line injection equipment. Particular care was exercised in modeling the distributor pump so as to match the dynamics of the delivery-valve assembly to the pressure wave propagation in the distributor and its outlets. The so-called minor losses were also taken into account and it was ascertained that sudden expansion and contraction lossesmore » were significant for the type of pump examined. The numerical and experimental results were compared and discussed, showing the validity of the model. The injection pressure time history and the influence of the delivery return-flow restriction on the system performance were numerically examined.« less

Exhaust emissions from two intercity passenger locomotives

Abstract: To enhance the effectiveness of intercity passenger rail service in mitigating exhaust emissions in California, the California Department of Transportation (Caltrans) included limits on exhaust emissions in its intercity locomotive procurement specifications. Because there were no available exhaust emission test data on which emission reduction goals could be based, Caltrans funded a test program to acquire gaseous and particulate exhaust emissions data, along with smoke opacity data, from two state-of-the-art intercity passenger locomotives. The two passenger locomotives (an EMD F59PH and a GE DASH8-32BWH) were tested at the Association of American Railroads Chicago Technical Center. The EMD locomotive was equipped with a separate Detroit Diesel Corporation (DDC) 8V-149 diesel engine used to provide 480 V AC power for the trailing passenger cars. This DDC engine was also emission tested. These data were used to quantify baseline exhaust emission levels as a challenge to locomotive manufacturers to offer new locomotives with reduced emissions. Data from the two locomotive engines were recorded at standard fuel injection timing and with the fuel injection timing retarded 4 deg in an effort to reduce NO[sub x] emissions. Results of this emissions testing were incorporated into the Caltrans locomotive procurement process by including emission performance requirementsmore » in the Caltrans intercity passenger locomotive specification, and therefore in the procurement decision. This paper contains steady-state exhaust emission test results for hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NO[sub x]), and particulate matter (PM) from the two locomotives. Computed sulfur dioxide (SO[sub 2]) emissions are also given, and are based on diesel fuel consumption and sulfur content. Exhaust smoke opacity is also reported.« less