bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison and Validation of Dynamics Simulation Models for a Structurally Flexible Manipulator
Authors: Stanway Jeff , Sharf Inna , Damaren Chris
Published: February 2008

This paper presents a series of experimental results obtained with a 2-DOF flexible-link direct-drive manipulator. First, we conduct a frequency analysis by comparing experimental natural frequencies with those predicted by the finite element model. Then, the time responses from four dynamics models are compared with each other and with the experiment. It is demonstrated that higher order nonlinearities are less important for slow maneuvers by close agreement between all four simulation models. For fast maneuvers, the two simpler models fail to predict a physically meaningful response. Good agreement with experimental results is attained with a model which accounts for all inertial nonlinearities. It is also shown that inclusion of damping in the dynamics models has a significant impact on their performance, as well as improving the correlation with experimental data.
The Importance of the Nitrous Oxide Pathway to NOx in Lean-Premixed Combustion
Authors: Nicol D. G. , Steele R. C. , Marinov N. M. , Malte P. C.
Published: February 2008

This study addresses the importance of the different chemical pathways responsible for NOx formation in lean-premixed combustion, and especially the role of the nitrous oxide pathway relative to the traditional Zeldovich pathway. NOx formation is modeled and computed over a range of operating conditions for the lean-premixed primary zone of gas turbine engine combustors. The primary zone, of uniform fuel-air ratio, is modeled as a micromixed well-stirred reactor, representing the flame zone, followed by a series of plug flow reactors, representing the postflame zone. The fuel is methane. The fuel–air equivalence ratio is varied from 0.5 to 0.7.The chemical reactor model permits study of the three pathways by which NOx forms, which are the Zeldovich, nitrous oxide, and prompt pathways. Modeling is also performed for the well-stirred reactor alone. Three recently published, complete chemical kinetic mechanisms for the C1–C2 hydrocarbon oxidation and the NOx formation are applied and compared. Verification of the model is based on the comparison of its NOx output to experimental results published for atmospheric pressure jet-stirred reactors and for a 10 atm. porous-plate burner. Good agreement between the modeled results and the measurements is obtained for most of the jet-stirred reactor operating range. For the porous-plate burner, the model shows agreement to the NOx measurements within a factor of two, with close agreement occurring at the leanest and coolest cases examined. For lean-premixed combustion at gas turbine engine conditions, the nitrous oxide pathway is found to be important, though the Zeldovich pathway cannot be neglected. The prompt pathway, however, contributes small-to-negligible NOx. Whenever the NOx emission is in the 15 to 30 ppmυ (15 percent O2, dry) range, the nitrous oxide pathway is predicted to contribute 40 to 45 percent of the NOx for high-pressure engines (30 atm), and 20 to 35 percent of the NOx for intermediate pressure engines (10 atm). For conditions producing NOx of less than 10 ppmυ (15 percent O2, dry), the nitrous oxide contribution increases steeply and approaches 100 percent. For lean-premixed combustion in the atmospheric pressure jet-stirred reactors, different behavior is found. All three pathways contribute; none can be dismissed. No universal behavior is found for the pressure dependence of the NOx. It does appear, however, that lean-premixed combustors operated in the vicinity of 10 atm have a relatively weak pressure dependence, whereas combustors operated in the vicinity of 30 atm have an approximately square root pressure dependence of the NOx.
Gas Turbine Bottoming Cycles: Triple-Pressure Steam Versus Kalina
Authors: Marston C. H. , Hyre M.
Published: February 2008

The performance of a triple-pressure steam cycle has been compared with a single-stage Kalina cycle and an optimized three-stage Kalina cycle as the bottoming sections of a gas turbine combined cycle power plant. A Monte Carlo direct search was used to find the optimum separator temperature and ammonia mass fraction for the three-stage Kalina cycle for a specific plant configuration. Both Kalina cycles were more efficient than the triple pressure steam cycle. Optimization of the three-stage Kalina cycle resulted in almost a two percentage point improvement.
Computation of Turbulent Evaporating Sprays: Eulerian Versus Lagrangian Approach
Authors: Hallmann M. , Scheurlen M. , Wittig S.
Published: February 2008

A new Eulerian model for turbulent evaporating sprays is presented. It comprises droplet heating and evaporation processes by solving separate transport equations for the droplet’s temperature and diameter. A Lagrangian approach, which we have discussed in detail on other occasions, is used in comparing the results of the new method. A comparison with experimental data shows that both approaches are successful in predicting the main features of turbulent evaporating sprays.
Degradation of a Jet A Fuel in a Single-Pass Heat Exchanger
Authors: Jones E. G. , Balster W. J. , Post M. E.
Published: February 2008

The formation of bulk and surface insolubles in a Jet A fuel during a single pass through heated stainless-steel tubes has been studied. Low temperature and low flow rates were utilized to produce near-isothermal conditions. In a second series of experiments, depletion of oxygen in the fuel saturated with respect to room-temperature air was measured under identical isothermal conditions. At a wall/bulk-fuel temperature of 185°C, rates of surface deposition and oxygen depletion were correlated; the maximum in the surface-deposition rate was found to occur after the Jet A fuel was stressed sufficiently that the dissolved oxygen was totally consumed. Results are discussed in terms of the autoxidation of the Jet A fuel and the concurrent production of deleterious bulk and surface insolubles.
Coatings for the Protection of Turbine Blades From Erosion
Authors: Walsh P. N. , Quets J. M. , Tucker R. C.
Published: February 2008

Many types of turbines, including aircraft gas turbines, steam turbines, and power recovery turbines, suffer from solid particle erosion caused by a variety of materials ingested into the machines. Utilization of various laboratory erosion tests tailored to the specific application by using various erodents, temperatures, velocities, and angles of impact, have been shown to be effective in the development and selection of coatings for the erosion protection of turbine blades and other components. Detonation gun coatings have demonstrated their efficacy in providing substantial protection in many situations. It has now been shown that several tungsten carbide and chromium carbide Super D-Gun™ coatings not only have better erosion resistance than their D-Gun analogs, but cause little or no degradation of the fatigue properties of the blade alloys. Nonetheless, caution should be employed in the application of any laboratory data to a specific situation and additional testing done as warranted by the turbine designer.
Soft Computing in Design and Manufacturing of Advanced Materials
Authors: Cios K. J. , Baaklini G. Y. , Vary A.
Published: February 2008

The goal of this paper is to show the potential of fuzzy sets and neural networks, often referred to as soft computing, for aiding in all aspects of manufacturing of advanced materials like ceramics. In design and manufacturing of advanced materials it is desirable to find which of the many processing variables contribute most to the desired properties of the material. There is also interest in real-time quality control of parameters that govern material properties during processing stages. This paper briefly introduces the concepts of fuzzy sets and neural networks and shows how they can be used in the design and manufacturing processes. These two computational methods are alternatives to other methods such as the Taguchi method. The two methods are demonstrated by using data collected at NASA Lewis Research Center. Future research directions are also discussed.
Active Vibration Control of Rotating Machinery Using Piezoelectric Actuators Incorporating Flexible Casing Effects
Authors: Barrett T. S. , Palazzolo A. B. , Kascak A. F.
Published: February 2008

The modern trend toward lighter and more flexible designs in rotating machinery brings with it increasing demands for ways to dissipate the excess energy transferred to such structures by the action of dynamic forces. The present study incorporates the use of active feedback control mechanisms to suppress this unwanted vibration. The basic active damping scheme involves the introduction of a control force on the structure from a feedback network whose input is dictated by the motion of the structure. The control force is applied to the rotor bearing support housing via a piezoelectric actuator attached to the rotor casing. The current research extends previous electromechanical simulations by incorporating a flexible finite element shell model of the casing to support the actuator and sensors. Actuator and feedback loop dynamics are included in the stability and response simulation.
Magnetic Bearing Control of Flexible Shaft Vibrations Based on Multi-access Velocity-Displacement Feedback
Authors: Petela G. , Botros K. K.
Published: February 2008

A model of the forced vibrations of a flexible, asymmetric, and unbalanced shaft, supported by two magnetic bearings, is derived to simulate the effect of different schemes of active control on shaft dynamic behavior. Simulation results were compared for several cases of single and multi-access bearing controls, rigid-body mode only and rigid with flexible mode control, and linear and nonlinear bearing responses. It is shown that the multi-access bearing response, calculated from the known equation of the stable ROCL (Reduced Order Closed Loop) and based on the direct velocity-displacement feedback, provided the most precise shift in critical frequencies and also reasonable suppression of shaft vibration amplitudes. The nonlinear bearing design was also briefly discussed. The stability analysis showed that stability limits were influenced by more parameters in this case, but no particular advantages were observed in suppression of the vibration amplitudes as compared to the linear case.
Applying Combined Pinch and Exergy Analysis to Closed-Cycle Gas Turbine System Design
Authors: Dhole V. R. , Zheng J. P.
Published: February 2008

Pinch technology has developed into a powerful tool for thermodynamic analysis of chemical processes and associated utilities, resulting in significant energy savings. Conventional pinch analysis identifies the most economical energy consumption in terms of heat loads and provides practical design guidelines to achieve this. However, in analyzing systems involving heat and power, for example, steam and gas turbines, etc., pure heat load analysis is insufficient. Exergy analysis, on the other hand, provides a tool for heat and power analysis, although at times it does not provide clear practical design guidelines. An appropriate combination of pinch and exergy analysis can provide practical methodology for the analysis of heat and power systems. The methodology has been successfully applied to refrigeration systems. This paper introduces the application of a combined pinch and exergy approach to commercial power plants with a demonstration example of a closed-cycle gas turbine (CCGT) system. Efficiency improvement of about 0.82 percent (50.2 to 51.02 percent) can be obtained by application of the new approach. More importantly, the approach can be used as an analysis and screening tool for the various design improvements and is generally applicable to any commercial power generation facility.
The Compression of Fuel Gas for Turbines, Engines, and Boilers in Cogeneration Plants
Authors: Arbon I. M.
Published: February 2008

The proliferation of gas-fired cogeneration plants in recent years had led to many installations being located on sites remote from high-pressure gas pipelines. Since it is often impractical or not cost effective to provide a dedicated high-pressure gas supply, such installations are often based close to alternative sources of fuel, such as small natural gas wells, landfill sites, or sewage digester plants. This paper will look at typical gas sources and composition, requirements of the fired equipment, the types of fuel gas compressors normally used, methods of compressor capacity control, and the development of synthetic and semi-synthetic lubricants for fuel gas compression duty.
Condensation in Jet Engine Intake Ducts During Stationary Operation
Authors: Young J. B.
Published: February 2008

The paper describes an analysis of the condensation of moist air in very long intake ducts of jet engines during stationary operation. Problems arising from such condensation include fan overspeed and increased stagnation pressure loss in the intake duct. The analysis demonstrates that, for moderate values of relative humidity, homogeneous condensation will occur in an outer annulus adjacent to the intake cowling if the local flow Mach number attains values of about 1.0. In the central region of the intake duct, where design Mach numbers of 0.8 may be attained, homogeneous condensation is unlikely to occur except, possibly, when the relative humidity is close to 100 percent and the ambient temperature very high. However, if the intake duct is very long, significant heterogeneous condensation on foreign particles present in the atmosphere is possible. The concentration of foreign nuclei required for this type of condensation is comparable to the likely levels of contamination at many industrial test sites. The effects of condensation on engine test results are twofold. First, condensation is a thermodynamically irreversible process and results in an increase of entropy and hence loss of total pressure in the intake duct. Uncorrected measurements using Pitot probes may not record this loss correctly. Second, the mass and energy transfer between the phases during the condensation process has a tendency to accelerate the flow approaching the engine, an effect that may be counteracted by a reduction in mass flow rate in order to maintain the static pressure constant. These conclusions are in agreement with experimental results obtained on-site during the testing of a jet engine fitted with a very long intake duct.
A Design Procedure for Effervescent Atomizers
Authors: Chin J. S. , Lefebvre A. H.
Published: February 2008

A methodology for the design of effervescent atomizers is described. The objective is to achieve sprays of minimum mean drop size for any stipulated values of liquid flow rate, air supply pressure, and air/liquid ratio. Application of the method leads to optimum values for all the key atomizer dimensions, including the number and size of the air injection holes, and the diameters of the mixing chamber and discharge orifice. It also enables optimum dimensions to be determined for a convergent-divergent nozzle should such a device be fitted to the nozzle exit to improve atomization performance. Examples are provided to demonstrate the application of the recommended design procedure and to illustrate the relative importance of various flow and geometric parameters in regard to their effects on atomization quality.
Multivariable Adaptive Control Using Only Input and Output Measurements for Turbojet Engines
Authors: Huang Jin-Quan , Sun Jian-Guo
Published: February 2008

Current and future aircraft engines are increasingly relying upon the use of multivariable control approach for meeting advanced performance requirements. A multivariable model reference adaptive control (MRAC) scheme is proposed in this paper. The adaptation law is derived using only input and output (I/O) measurements. Simulation studies are performed for a two-spool turbojet engine. The satisfactory transient responses are obtained at different operating points from idle to maximum dry power within the flight envelope. These show insensitivity of the design to engine power level and flight condition. Simulation results also show high effectiveness of reducing interaction in multivariable systems with significant coupling. Using the multivariable MRAC controller, the engine acceleration time is reduced by about 19 percent in comparison with the conventional engine controller.
Steam-Injected Gas Turbine Analysis: Steam Rates
Authors: Rice I. G.
Published: February 2008

This paper presents an analysis of steam rates in steam-injected gas turbines (simple and reheat). In considering a gas turbine of this type, the steam-injection flow is separated from the main gas stream for analysis. Dalton’s and Avogadro’s laws of partial pressure and gas mixtures are applied. Results obtained provide for the accurate determination of heat input, gas expansion based on partial pressures, and heat-rejection steam-enthalpy points.
A New Constitutive Model for Several Metals Under Arbitrary Temperature and Loading Conditions
Authors: Whaley P. W.
Published: February 2008

A new theory of viscoplasticity is described that models yielding as a random phenomenon. A circle on the deviatoric stress plane represents the intensity of yielding with the radius equal to the random yielding microstress. This random model does not utilize a yield surface; yielding intensity is quantified by expected values defined in the deviatoric stress plane. The circle in the deviatoric stress plane with a random radius is a simple way to model multi-axial loading. Approximations for stress, strain energy density, and plastic strain energy density are used to improve the computational efficiency of parameter selection and to quantify the flow criterion. The exact state equations are derived, which can be manipulated to describe a wide variety of loading conditions for a broad temperature range. Reversed loading, stress relaxation, creep, and nonproportional loading are all natural properties of the model, which require little additional elaboration. Material properties were specified for five metals, three at room temperature and two over a wide temperature range.
Finite Element Analysis of Structural Engineering Problems Using a Viscoplastic Model Incorporating Two Back Stresses
Authors: Arya V. K. , Halford G. R.
Published: February 2008

The feasibility of a viscoplastic model incorporating two back stresses and a drag strength is investigated for performing nonlinear finite element analyses of structural engineering problems. The model has recently been put forth by Freed and Walker. The feasibility of the viscoplastic model is demonstrated for nonlinear structural analyses by implementing the model into a finite element program and performing nonlinear finite element analyses for several uniaxial and multiaxial problems. Good agreement is shown to exist between the results obtained using the finite element implementation and those obtained experimentally. The advantages of using advanced viscoplastic models for performing nonlinear finite element analyses of structural components are indicated.
The Application of a Method to Evaluate the Design Performance of a Feedwater Heater With a Short Drain Cooler
Authors: Weber G. E. , Worek W. M.
Published: February 2008

The application of the Modified Delaware Method, which was developed by Weber and Worek (1994) to evaluate the design performance of a feedwater heater with a short drain cooler, is illustrated. All calculations used in obtaining the heat transfer coefficients and pressure drops in the desuperheating, condensing, and drain cooling zones are shown by applying the method to an actual heater design.
Assessment of Notches in Ceramic Components
Authors: Bru¨ckner-Foit A. , Heger A. , Munz D.
Published: February 2008

The failure probability of notched tensile bars is calculated using the multi-axial Weibull theory. The influence exerted by the stress concentration factor, the stress gradient in the notch root, and the Weibull exponent is analyzed.
Application of SPSLIFE to Preliminary Design Evaluation and Life Assessment of CSGT Components
Authors: Saith A. , Norton P. F. , Parthasarathy V. M.
Published: February 2008

The Ceramic Stationary Gas Turbine (CSGT) Program has utilized the SPSLIFE computer code to evaluate the preliminary design of ceramic components. The CSGT program is being performed under the sponsorship of the United States Department of Energy, Office of Industrial Technology, to improve the performance of stationary gas turbines in cogeneration through the selective replacement of hot section components with ceramic parts. Preliminary design evaluation and life assessment results are presented here for the following components: (1) Stage 1 turbine blade, (2) Stage 1 turbine nozzle, and (3) combustor inner liner. From the results of the analysis, recommendations are made for improving the life and reliability of the components. All designs were developed in Phase I (preliminary design) of the CSGT program and will be optimized in Phase II (detail design) of the program.
Observations of Flame Behavior From a Practical Fuel Injector Using Gaseous Fuel in a Technology Combustor
Authors: Hedman P. O. , Sturgess G. J. , Warren D. L. , Goss L. P. , Shouse D. T.
Published: February 2008

This paper presents results from an Air Force program being conducted by researchers at Brigham Young University (BYU) Wright-Patterson Air Force Base (WPAFB), and Pratt and Whitney (P&W). This study is part of a comprehensive effort being supported by the Aero Propulsion and Power Laboratory at Wright-Patterson Air Force Base, and Pratt and Whitney in which simple and complex diffusion flames are being studied to understand better the fundamentals of gas turbine combustion near lean blowout. The program’s long-term goal is to improve the design methodology of gas turbine combustors. This paper focuses on four areas of investigation: (1) digitized images from still film photographs to document the observed flame structures as fuel equivalence ratio was varied, (2) sets of LDA data to quantify the velocity flow fields existing in the burner (3) CARS measurements of gas temperature to determine the temperature field in the combustion zone, and to evaluate the magnitude of peak temperature, and (4) two-dimensional images of OH radical concentrations using PLIF to document the instantaneous location of the flame reaction zones.
A Review of Droplet Dynamics and Vaporization Modeling for Engineering Calculations
Authors: Aggarwal S. K. , Peng F.
Published: February 2008

The present paper reviews the methodologies for representing the droplet motion and vaporization history in two-phase flow computations. The focus is on the use of droplet models that are realistic in terms of their efficient implementation in comprehensive spray simulations, representation of important physical processes, and applicability under a broad range of conditions. The methodologies available at present to simulate droplet motion in complex two-phase flows may be broadly classified into two categories. First one is based on the modified BBO equation. This approach is more comprehensive, but requires modifications and/or correlations at higher droplet Reynolds number. The second approach aims at developing correlations, using detailed numerical simulations or laboratory experiments, for the effects of flow nonuniformity and droplet relative acceleration on the instantaneous drag and lift coefficients. Recent advances made in the droplet vaporization models are also discussed. The advanced vaporization models include the effects of transient liquid heating, gas-phase convection, and variable thermo physical properties. All of these models are discussed, and recommendations are made for their inclusion in comprehensive two-phase computations.
Laser Vibrometry Measurements of Rotating Blade Vibrations
Authors: Reinhardt A. K. , Kadambi J. R. , Quinn R. D.
Published: February 2008

One of the most important design factors in modern turbomachinery is the vibration of turbomachinery blading. There is a need for developing an in-service, noncontacting, noninterfering method for the measurement and monitoring of gas turbine, jet engine, and steam turbine blade vibrations and stresses. Such a technique would also be useful for monitoring rotating helicopter blades. In the power generation industry, blade failures can result in millions of dollars of downtime. The measurement of blade vibrations and dynamic stresses is an important guide for preventive maintenance, which can be a major contributor to the availability of steam turbine, gas turbine, and helicopter operations. An experiment is designed to verify the feasibility of such a vibration monitoring system using the reference beam on-axis laser-Doppler technique. The experimental setup consists of two flat, cantilever blades mounted on a hub attached to the shaft of a dc motor. The motor rests on a linear bearing permitting motion only in the direction of the motor shaft. The motor and blade assembly is then excited via an electrodynamic shaker at the first natural frequency of the blades. The resulting blade vibration is then detected using a laser vibrometer. The vibration frequencies and amplitudes of the two rotating blades are successfully measured.
An Assessment of the Thermodynamic Performance of Mixed Gas–Steam Cycles: Part B—Water-Injected and HAT Cycles
Authors: Chiesa P. , Lozza G. , Macchi E. , Consonni S.
Published: February 2008

Part B of this paper focuses on intercooled recuperated cycles where water is injected to improve both efficiency and power output. This concept is investigated for two basic cycle configurations: a Recuperated Water Injected (RWI) cycle, where water is simply injected downstream of the HP compressor, and a Humid Air Turbine (HAT) cycle, where air/water mixing is accomplished in a countercurrent heat/mass transfer column called “saturator,” For both configurations we discuss the selection and the optimization of the main cycle parameters, and track the variations of efficiency and specific work with overall gas turbine pressure ratio and turbine inlet temperature (TIT). TIT can vary to take advantage of lower gas turbine coolant temperatures, but only within the capabilities of current technology. For HAT cycles we also address the modelization of the saturator and the sensitivity to the most crucial characteristics of novel components (temperature differences and pressure drops in heat/mass transfer equipment). The efficiency penalties associated with each process are evaluated by a second-law analysis, which also includes the cycles considered in Part A. For any given TIT in the range considered (1250 to 1500°C), the more reversible air/water mixing mechanism realized in the saturator allows HAT cycles to achieve efficiencies about 2 percentage points higher than those of RWI cycles: At the TIT of 1500°C made possible by intercooling, state-of-the-art aero-engines embodying the above-mentioned cycle modifications can reach net electrical efficiencies of about 57 and 55 percent, respectively. This compares to efficiencies slightly below 56 percent achievable by combined cycles based upon large-scale heavy-duty machines with TIT = 1280°C.
Arbitrary Surface Flank Milling of Fan, Compressor, and Impeller Blades
Authors: Wu C. Y.
Published: February 2008

It is generally conceived that a blade surface is flank millable if it can be closely approximated by a ruled surface; otherwise the slow machining process of point milling has to be employed. However, we have now demonstrated that the ruled surface criterion for flank milling is neither necessary nor sufficient. Furthermore, many complex arbitrary surfaces typical of our blades in fans, axial compressors, and centrifugal impellers in aviation gas turbines are actually closely flank millable and can be rendered exactly flank millable with one or more passes per surface often without sacrificing, indeed usually with gain, in performance.
Laser Guidance for Repairing Gas Turbine Parts
Authors: Galel Z. , Hunt J. L. , Unger T. H.
Published: February 2008

As a result of normal operating conditions, jet engine parts tend to distort. During repair, many of these parts require some form of selective cutting. Due to the differences between each individual part, automation such as CNC machining becomes complex. The need to map each individual part prior to machining has prohibited repair facilities from introducing sophisticated automation. This paper presents for the first time a novel method that addresses many problems related to selective material removal in jet engine repairs. Similar to a terrain-following cruise missile, a laser-guided cutter is used to follow a selected datum surface. For example, in the case of Honeycomb Airseals, the thin laser beam penetrates the honeycomb cell structure to follow the base metal. The method minimizes parent metal removal and under-minimum-wall condition. As a result, life potential of parts is extended, and repair costs are reduced. The ability to track a moving part and modify the cutting path automatically produces one more significant advantage: Accurate setup of a part on a machine is no longer critical. The method has applications in the repair of airseals, frames and cases, and airfoils.
Comparison Between EBW and GTAW for Turmo IV C Compressor Blade Repairs
Authors: Miglietti W.
Published: February 2008

A research study was undertaken to evaluate whether electron beam welding (EBW) or gas tungsten arc welding (GTAW) could be utilized for repairs to the leading edges of the Turmo IV C compressor blades. These blades are manufactured from Ti-6Al-4V. The study entailed performing a series of welding trials. For the GTAW process a matching filler metal to the parent metal was used, whereas for the EBW process, the welds were made autogenously. After metallographic examination of the weld microstructure, mechanical property assessments were undertaken, namely tensile and fatigue tests, the latter being a stringent test to evaluate the performance of the welded joint. The results demonstrated that the EB welds had equivalent properties to the parent metal, whereas the GTA welds had poorer fatigue properties due to undesirable microstructure that resulted in the weld zone. The results achieved herein showed that the EBW process would be an appropriate technique for the restoration of these compressor blades.
Design and Development of the WR-21 Intercooled Recuperated (ICR) Marine Gas Turbine
Authors: Shepard S. B. , Bowen T. L. , Chiprich J. M.
Published: February 2008

The U.S. Navy is developing an Intercooled Recuperated (ICR) marine gas turbine, designated the WR-21, for propulsion of future surface ships. The objectives of this development program and the key technical requirements are summarized. The design of the WR-21 is described in considerable detail. Meeting all the design requirements for performance, space, weight, reliability, maintainability, and life has been challenging. Numerous design tradeoffs and iterations have been performed to optimize the design within the constraints imposed in the ICR technical specification. Integration of the WR-21 engine into the DDG51 Flight IIA ship, which is the U.S. Navy’s first application, has influenced the WR-21 design. This paper discusses the aspects of the DDG-51 application that were factored into the design of the ICR engine in order to reduce installation costs.
Updating the ANSI Standard on Measurement of Exhaust Emissions
Authors: Vaught J. M.
Published: February 2008

The American National Standards Institute (ANSI) required that the source testing Standard on Measurement of Exhaust Emissions from Stationary Gas Turbine Engines, B133.9, be brought up to date with today’s regulatory requirements and best measurement technology. The criteria for the design of the Standard along with its content and format are discussed. The selection of measurement methods for gaseous components, smoke, and particulates emitted by present-day emission-controlled industrial gas turbine engines is presented.
Lyapunov’s Stability of Nonlinear Misaligned Journal Bearings
Authors: Nikolakopoulos P. G. , Papadopoulos C. A.
Published: February 2008

In this paper the stability of nonlinear misaligned rotor-bearing systems is investigated, using the Lyapunov direct method. A finite element formulation is used to determine the journal bearing pressure distribution. Then the linear and nonlinear stiffness, damping, and hybrid (depending on both displacement and velocity) coefficients are calculated. A general method of analysis based on Lyapunov’s stability criteria is used to investigate the stability of nonlinear misaligned rotor bearing systems. The equations of motion of the rigid rotor on the nonlinear bearings are used to find a Lyapunov function using some of these coefficients, which depend on L/D ratio and the misalignment angles ψx, ψy. The analytical conditions for the stability or instability of some examined cases are given and some examples for the orbital stability are also demonstrated.
Experimental Identification of Linearized Oil Film Coefficients of Cylindrical and Tilting Pad Bearings
Authors: Arumugam P. , Swarnamani S. , Prabhu B. S.
Published: February 2008

The dynamic behavior of the rotating machinery supported by the hydrodynamic journal bearings is significantly influenced by the dynamic characteristics of the oil film. In the present work an efficient identification method is used to identify the stiffness and damping coefficients of the tilting pad and cylindrical journal bearings of a flexible rotor-bearing system. The method uses FRFs (Frequency Response Functions) obtained by the measurements and the finite element method. The accuracy and feasibility of the method were tested and demonstrated by theoretical simulation. The possible effects of oil-film inertia is also verified by the theoretical simulation. The method can be further extended to identify twelve linearized oil-film coefficients.
The Use of Imposed Displacements to Determine Impact Forces in a Multiple Blade Shed Incident
Authors: Dewhurst T. B. , Tang P.
Published: February 2008

Experimental data from a multiple blade shed incident are used to determine the forces exerted by the blades on a containment ring. A transient, dynamic, finite element procedure is used to model the ring during the blade shed. This work focuses on the selection of the proper numerical parameters that lead to a stable and accurate numerical solution while maintaining physical reality. Examination of the degree of implicitness and various measures of damping, as well as incorporation of large displacement algorithms, has lead to a simulation that successfully determines the forces on the ring. Accurate determination of these forces is necessary for optimal design of containment systems.
A Methodology to Assess Design Uncertainty in Selecting Affordable Gas Turbine Technology
Authors: Younghans J. L. , Johnson J. E. , Csonka S. J.
Published: February 2008

A methodology is discussed that allows quantification of uncertainty in the gas turbine design and analysis process. The methodology can be employed to rank order the cost effectiveness of advanced component technologies or alternatively can be used to determine probable performance (sfc and thrust) of engines that have component performance uncertainties. Execution of the methodology requires a desktop computer and commercially available software.
System Evaluation and LBTU Fuel Combustion Studies for IGCC Power Generation
Authors: Cook C. S. , Corman J. C. , Todd D. M.
Published: February 2008

The integration of gas turbines and combined cycle systems with advances in coal gasification and gas stream cleanup systems will result in economically viable IGCC systems. Optimization of IGCC systems for both emission levels and cost of electricity is critical to achieving this goal. A technical issue is the ability to use a wide range of coal and petroleum-based fuel gases in conventional gas turbine combustor hardware. In order to characterize the acceptability of these syngases for gas turbines, combustion studies were conducted with simulated coal gases using full-scale advanced gas turbine (7F) combustor components. It was found that NOx emissions could be correlated as a simple function of stoichiometric flame temperature for a wide range of heating values while CO emissions were shown to depend primarily on the H2 content of the fuel below heating values of 130 Btu/scf (5125 kJ/NM3) and for H2/CO ratios less than unity. The test program further demonstrated the capability of advanced can-annular combustion systems to burn fuels from air-blown gasifiers with fuel lower heating values as low as 90 Btu/scf (3548 kJ/NM3) at 2300°F (1260°C) firing temperature. In support of ongoing economic studies, numerous IGCC system evaluations have been conducted incorporating a majority of the commercial or near-commercial coal gasification systems coupled with “F” series gas turbine combined cycles. Both oxygen and air-blown configurations have been studied, in some cases with high and low-temperature gas cleaning systems. It has been shown that system studies must start with the characteristics and limitations of the gas turbine if output and operating economics are to be optimized throughout the range of ambient operating temperature and load variation.
Numerical Computation and Validation of Two-Phase Flow Downstream of a Gas Turbine Combustor Dome Swirl Cup
Authors: Tolpadi A. K. , Burrus D. L. , Lawson R. J.
Published: February 2008

The two-phase axisymmetric flow field downstream of the swirl cup of an advanced gas turbine combustor is studied numerically and validated against experimental Phase-Doppler Particle Analyzer (PDPA) data. The swirl cup analyzed is that of a single annular GE/SNECMA CFM56 turbofan engine that is comprised of a pair of coaxial counterswirling air streams together with a fuel atomizer. The atomized fuel mixes with the swirling air stream, resulting in the establishment of a complex two-phase flow field within the swirl chamber. The analysis procedure involves the solution of the gas phase equations in an Eulerian frame of reference using the code CONCERT. CONCERT has been developed and used extensively in the past and represents a fully elliptic body-fitted computational fluid dynamics code to predict flow fields in practical full-scale combustors. The flow in this study is assumed to be nonreacting and isothermal. The liquid phase is simulated by using a droplet spray model and by treating the motion of the fuel droplets in a Lagrangian frame of reference. Extensive PDPA data for the CFM56 engine swirl cup have been obtained at atmospheric pressure by using water as the fuel (Wang et al., 1992a). The PDPA system makes pointwise measurements that are fundamentally Eulerian. Measurements have been made of the continuous gas phase velocity together with discrete phase attributes such as droplet size, droplet number count, and droplet velocity distribution at various axial stations downstream of the injector. Numerical calculations were performed under the exact inlet and boundary conditions as the experimental measurements. The computed gas phase velocity field showed good agreement with the test data. The agreement was found to be best at the stations close to the primary venturi of the swirler and to be reasonable at later stations. The unique contribution of this work is the formulation of a numerical PDPA scheme for comparing droplet data. The numerical PDPA scheme essentially converts the Lagrangian droplet phase data to the format of the experimental PDPA. Several sampling volumes (bins) were selected within the computational domain. The trajectories of various droplets passing through these volumes were monitored and appropriately integrated to obtain the distribution of the droplet characteristics in space. The calculated droplet count and mean droplet velocity distributions were compared with the measurements and showed very good agreement in the case of larger size droplets and fair agreement for smaller size droplets.
Development Requirements for an Advanced Gas Turbine System
Authors: Bannister R. L. , Cheruvu N. S. , Little D. A. , McQuiggan G.
Published: February 2008

In cooperation with U.S. Department of Energy’s Morgantown Energy Technology Center, a Westinghouse-led team is working on the second part of an 8-year, Advanced Turbine Systems Program to develop the technology required to provide a significant increase in natural gas-fired combined cycle power generation plant efficiency. This paper reports on the Westinghouse program to develop an innovative natural gas-fired advanced turbine cycle, which, in combination with increased firing temperature, use of advanced materials, increased component efficiencies, and reduced cooling air usage, has the potential of achieving a lower heating value plant efficiency in excess of 60 percent.
A Combined Cycle Designed to Achieve Greater Than 60 Percent Efficiency
Authors: Briesch M. S. , Bannister R. L. , Diakunchak I. S. , Huber D. J.
Published: February 2008

In cooperation with the U.S. Department of Energy’s Morgantown Energy Technology Center, Westinghouse is working on Phase 2 of an 8-year Advanced Turbine Systems Program to develop the technologies required to provide a significant increase in natural gas-fired combined cycle power generation plant efficiency. In this paper, the technologies required to yield an energy conversion efficiency greater than the Advanced Turbine Systems Program target value of 60 percent are discussed. The goal of 60 percent efficiency is achievable through an improvement in operating process parameters for both the combustion turbine and steam turbine, raising the rotor inlet temperature to 2600°F (1427°C ), incorporation of advanced cooling techniques in the combustion turbine expander, and utilization of other cycle enhancements obtainable through greater integration between the combustion turbine and steam turbine.
A Gas-Operated Bearing Damper for Turbomachinery—Theoretical Predictions Versus Experimental Measurements: Part II—Experimental Results and Comparison With Theory
Authors: Sundararajan P. , Vance J. M.
Published: February 2008

This is the second of two papers describing results of a research project directed at developing a gas-operated vibration damper for high-temperature turbomachinery applications. This part presents the experimental measurements made on a gas damper hardware and compares them with the theoretical predictions given in Part I. It is found that the isentropic theoretical model predicts the damper characteristics quite well. A maximum damping of 2310 N-s/m (13.2 lb-s/in.) was measured at a natural frequency of 118 Hz using the present design and the results suggest that significantly higher damping levels are possible with design modifications.
Active Vibration Control of Rotating Machinery With a Hybrid Piezohydraulic Actuator System
Authors: Tang P. , Palazzolo A. B. , Kascak A. F. , Montague G. T.
Published: February 2008

An integrated, compact piezohydraulic actuator system for active vibration control was designed and developed with a primary application for gas turbine aircraft engines. Copper tube was chosen as the transmission line material for ease of assembly. Liquid plastic, which meets incompressibility and low-viscosity requirements, was adjusted to provide optimal actuator performance. Variants of the liquid plastic have been prepared with desired properties between −40°F and 400°F. The effectiveness of this hybrid actuator for active vibration control (AVC) was demonstrated for suppressing critical speed vibration through two critical speeds for various levels of intentionally placed imbalance. A high-accuracy closed-loop simulation, which combines both finite element and state space methods, was applied for the closed-loop unbalance response simulation with/without AVC. Good correlation between the simulation and test results was achieved.
Development of 300 kW Class Ceramic Gas Turbine (CGT303)
Authors: Ohhashi I. , Arakawa S.
Published: February 2008

CGT303 is a two-shaft regenerative ceramic gas turbine with rotary heat exchangers for the purpose of mobile power generator. It is also widely adaptable for industrial machinery and construction machinery as well. The development program of CGT303 is funded by the New Energy and Industrial Technology Development Organization (NEDO). The maximum output power of 300 kW and thermal efficiency of 42 percent at TiT 1350°C are the objectives of this development. The high TiT requires all gas passage components to be made of ceramics that are designed appropriately to keep sufficient strength by using sophisticated computer analysis. Hot spin tests on ceramic turbine rotors and thermal shock tests on stationary ceramic components have been carried out to prove their strength. The paper covers the design concept of CGT303 and results of analysis.
Ceramic Gas Turbine Technology Development
Authors: Easley M. L. , Smyth J. R.
Published: February 2008

AlliedSignal Engines is addressing critical concerns slowing the commercialization of structural ceramics in gas turbine engines. These issues include ceramic component reliability, commitment of ceramic suppliers to support production needs, and refinement of ceramic design technologies. The stated goals of the current program are to develop and demonstrate structural ceramic technology that has the potential for extended operation in a gas turbine environment by incorporation in an auxiliary power unit (APU) to support automotive gas turbine development. AlliedSignal Engines changed the ATTAP ceramic engine test bed from the AGT101 automotive engine to the 331-200[CT] APU. The 331-200[CT] first-stage turbine nozzle segments and blades were redesigned using ceramic materials, employing design methods developed during the earlier DOE/NASA-funded Advanced Gas Turbine (AGT) and the ATTAP programs. The ceramic design technologies under development in the present program include design methods for improved resistance to impact and contact damage, assessment of the effects of oxidation and corrosion on ceramic component life, and assessment of the effectiveness of nondestructive evaluation (NDE) and proof testing methods to reliably identify ceramic parts having critical flaws. AlliedSignal made progress in these activities during 1993 ATTAP efforts. Ceramic parts for the 331-200[CT] engine have been fabricated and evaluated in component tests, to verify the design characteristics and assure structural integrity prior to full-up engine testing. Engine testing is currently under way. The work summarized in this paper was funded by the U.S. Dept. of Energy (DOE) Office of Transportation Technologies and administered by NASA-Lewis Research Center, under Contract No. DEN3-335.
Design and Development of a Direct Injected, Glow Plug Ignition-Assisted, Natural Gas Engine
Authors: Willi M. L. , Richards B. G.
Published: February 2008

Conventional (Otto cycle) natural gas engines are limited in power and thermal efficiency relative to a diesel engine due to detonation and the need to run a nearly stoichiometric air/fuel ratio. Technology is under development to burn natural gas in a direct-injected diesel cycle that is not prone to detonation or air/fuel ratio control limitations. Direct-injected gas (DIG) technology will allow natural gas engines to match the power and thermal efficiency of the equivalent diesel-fueled engine. Laboratory development now under way is targeted for field experimental evaluation of a DIG 3516 engine in a 1500 kW road switcher locomotive. This paper will describe DIG 3516 engine component design and single and multicylinder performance development.