bluuebunny/crossref_metadata_2025 huggingface dataset:
Recessed Casing Treatment Effects on Fan Performance and Flow Field
Authors: Kang C. S. , McKenzie A. B. , Elder R. L.
Published: February 2015

An experimental investigation to examine the influence of the vaned recess casing treatment on stall margin, operating efficiency and the flow field of a low speed axial flow fan with aerospace type blade loading is presented. Different geometrical designs of the vaned passages were examined. The best configuration resulted in a stall margin improvement of 67%, a significantly higher pressure rise in the stall region and insignificant change in peak efficiency. Detailed 3-D flow measurements in the endwall region and in the casing recess were carried out with a slanted hot-wire, providing some insight to the operation of the device. The results revealed that the stall margin improvement was largely due to the removal of flow from the blade tip to the recess, and the elimination of the growth of the stall region at the tip, which occurs at stall in the solid casing build.
OGV Tailoring to Alleviate Pylon-OGV-Fan Interaction
Authors: Shrinivas G. N. , Giles M. B.
Published: February 2015

This paper studies the application of sensitivity analysis to the redesign of outlet guide vanes (OGV’s) in a commercial gas turbine engine. The redesign is necessitated by the interaction of the pylon induced static pressure field with the OGV’s and the fan, leading to reduced OGV efficiency and shortened fan life. The concept of cyclically varying camber is used to redesign the OGV row to achieve suppression of the downstream disturbance in the domain upstream of the OGV row. The harmonic nature of the disturbance and the tailoring permits the analysis for the redesign to be performed on only one blade passage. Sensitivity of the pressure field upstream of the OGV’s to changes in blade camber is computed, and used to modify the blade profile. The sensitivity is obtained from a linear perturbation CFD analysis; nonlinear CFD analysis and actuator disc theory (ADisc) provide validation at each step. The modifications reduce the pylon induced pressure variation at the fan by more than 70%. The presence of an interaction mechanism from the pylon to the OGV’s is investigated.
Research and Development of 300kW Class Ceramic Gas Turbine (Development of the Static Ceramic Components for CGT303)
Authors: Murota Mitsuharu , Ohhashi Issei , Ito Yoshiyuki , Arakawa Sadao
Published: February 2015

As the result of setting the low pressure ratio at 4.5, sizes of the static ceramic components forming the gas passage in CGT303 have been increased, and establishing reliability of these components was thought to be the most important task. So, the heat-cycle tests were conducted, in advance of the engine operation, and improvements have been made on their material and constructions.

After conducting 600 times of the heat-cycle tests, so far, up to the gas temperature of 1200°C, we have succeeded in the engine operation at the turbine inlet temperature of 1200°C Examples of the problems encountered in the test and of the solutions therefore are introduced in this paper.
An Approximate Modal Method for Rotordynamic Stability Prediction of Flexible Rotors
Authors: Chan Dennis S. H.
Published: February 2015

The prediction of rotordynamic stability is important in the design and diagnosis of high-performance turbomachinery. An approximate method using the mode shape and natural frequency of the first undamped vibration mode of the rotor-bearing system is developed and verified to be accurate for practical cases. The assumption that the damping does not significantly affect the first mode modal parameters can be relaxed if the damped mode shape is available. It confirms previous findings that the mode deflection at the bearing position is most critical to rotor-bearing system stability. The modal method, despite its simplicity, is superior to the lumped parameter method since it can easily account for the distributed shaft parameters and the effective modal contribution of other component properties including the aerodynamic excitation. When provided with the results of the undamped vibration analysis (i.e. only one eigensolution for a specified system configuration), the method predicts a linear relationship between stability measured in terms of logarithmic decrement and system (bearing) damping. The method allows very efficient parameter studies for the effect of bearing damping and aerodynamic cross-coupling on system stability.
Ceramic Gas Turbine Technology Development
Authors: Rettler M. W. , Easley M. L. , Smyth J. R.
Published: February 2015

Under the U.S. Dept. of Energy/National Aeronautics and Space Administration (DOE/NASA) funded Ceramic Turbine Engine Demonstration Project, formerly the Advanced Turbine Technology Applications Project (ATTAP), AlliedSignal Engines is addressing the remaining critical concerns slowing the commercialization of structural ceramics in gas turbine engines. These issues include demonstration of ceramic component reliability, readiness of ceramic suppliers to support ceramic production needs, and development of ceramic design technologies.

The AlliedSignal/Garrett Model 331-200[CT] Auxiliary Power Unit (APU) is being used as a ceramics test bed engine. The first-stage turbine blades and nozzles were redesigned using ceramic materials, employing the design methods developed during the earlier DOE/NASA-funded Advanced Gas Turbine (AGT) and ATTAP programs. Ceramic engine components have been fabricated and are now being evaluated in laboratory engine testing. The fabrication processes for these components will provide the framework for a demonstration of manufacturing process scale-up to the minimum level for commercial viability. The laboratory engine testing is helping to refine the component designs and focus the development of ceramic component technologies. Extended engine endurance testing and field testing in commercial aircraft is planned to demonstrate ceramic component reliability.

Significant progress has been made during 1994. An engine with ceramic turbine nozzles was successfully operated and engine tests in the laboratory are continuing to gather useful data. An engine equipped with ceramic blades was also tested, but blade fractures occurred, interrupting operation. An extensive investigation has identified possible vibration and contact problems. Investigative evaluation efforts are continuing to identify the problem source and determine go-forward plans for ceramic blade development. Component design technologies have progressed in the areas of modeling particle impact pulverization, development of a ceramic hot corrosion environmental life model, and methods for evaluating ceramic contact damage. The planned ceramic manufacturing scale-up was initiated with two ceramics vendors, Norton Advanced Ceramics (East Granby, CT) and AlliedSignal Ceramic Components (Torrance, CA). The scaleup demonstration program is emphasizing improvement of ceramic processing yields and increased production rates.

Work summarized in this paper was funded by the U.S. Dept. of Energy (DOE) Office of Transportation Technologies, as part of the Turbine Engine Technologies Program, and administered by the NASA Lewis Research Center, Cleveland, OH under Contract No. DEN3-335.
A Compact Lightweight Gas-Turbine Regenerator
Authors: Beck Douglas Stephen
Published: February 2015

This paper describes a new kind of gas-turbine regenerator, the Creare Baleen Regenerator. The Baleen Regenerator is much more compact and lightweight than current regenerators and recuperators. These features make the Baleen Regenerator attractive for regenerative gas turbines for aircraft, power generation, marine propulsion, and automobiles. In addition to a description of the Baleen Regenerator, this paper also gives a design method with which the Baleen Regenerator and other regenerators can be designed directly from input specifications. This design method is illustrated with designs of the Baleen Regenerator for a 20 MW gas turbine and a 3 MW gas turbine.
Performance of a Mixed Flow Turbocharger Turbine Under Pulsating Flow Conditions
Authors: Arcoumanis C. , Hakeem I. , Khezzar L. , Martinez-Botas R. F. , Baines N. C.
Published: February 2015

The performance of a high pressure ratio (P.R.=2.9) mixed flow turbine for an automotive turbocharger has been investigated and the results revealed its better performance relative to a radial-inflow geometry under both steady and pulsating flow conditions. The advantages offered by the constant blade angle rotor allow better turbocharger-engine matching and maximization of the energy extracted from the pulsating engine exhaust gases. In particular, the mixed inlet blade geometry resulted in high efficiency at high expansion ratios where the engine-exhaust pulse energy is maximum. The efficiency characteristics of the mixed flow turbine under steady conditions were found to be fairly uniform when plotted against the velocity ratio, with a peak efficiency at the design speed of 0.75. The unsteady performance as indicated by the mass-averaged total-to-static efficiency and the swallowing capacity exhibited a departure from the quasi-steady assumption which is analysed and discussed.
Simple Design Methods for the Prediction of Radial Static Pressure Distributions in a Rotor-Stator Cavity With Radial Inflow
Authors: Hart Kenneth J. , Turner Alan B.
Published: February 2015

Research has been conducted into the effects of component geometry and air bleed flow on the radial variation of static pressure and core tangential velocity in a rotor-stator cavity of the type often found behind the impeller of a gas turbine engine centrifugal compressor.

A CFD code, validated by rig test data for a wide range of rotor-stator axial gaps and throughflows, has been used to generate pressure and velocity data for typical gas turbine operating conditions.

This data has been arranged as a series of simple design curves which relate the rotational speed of the core of fluid between rotor and stator boundary layers, and hence the static pressure distribution, to primary cavity geometry, rotational Reynolds number and bleed throughflow with particular attention to radial inflowing bleeds. Details are provided on the use and limitations of these curves.

Predictions using this method have been compared successfully with measured data from engine test and a compressor test rig, modified to facilitate variable quantity and direction of impeller rear face bleed flow, at typical gas turbine operational power conditions.

Data generated by these curves can be used directly in the design process and to validate integral momentum methods which can provide relatively simple computation of rotor-stator cavity pressure and velocity distributions independently or within air system network programs.

This approach is considered to be a cost and time effective addition to the analytical design process especially if validated CFD code, which can accommodate rotational flows consistently and accurately, is not available.
Conditioned Navier-Stokes and k–ϵ–γ Equations to Model Transition in Pressure Gradient Flow
Authors: Steelant J. , Dick E.
Published: February 2015

Conditionally averaged Navier-Stokes equations are derived to describe transitional flow. The averages are taken during the fraction of time the flow is laminar or turbulent, respectively. Conditional averaging leads both for the laminar and turbulent parts to a set of equations for mass, momentum and energy. The conditioned equations differ from the original Navier-Stokes equations by the presence of source terms which are functions of the intermittency factor, γ. This factor is the extra unknown and is determined by a transport equation. The evolution of γ depends mainly on the turbulence level, pressure gradient and Reynolds-number. The turbulence is described by the classical k-ϵ model. The approach is verified against several test cases, with and without pressure gradients.
Application of Advanced Probabilistic Fracture Mechanics to Life Evaluation of Turbine Rotor Blade Attachments
Authors: Millwater H. R. , Wu Y.-T. , Cardinal J. W. , Chell G. G.
Published: February 2015

This paper describes the application of an advanced probabilistic fracture mechanics computational algorithm with inspection simulation to the probabilistic life assessment of a turbine blade attachment, sometimes referred to as a steeple or fir tree. The life of the steeple is limited by high cycle fatigue. The methodology utilized combines structural finite element analysis, stochastic fatigue crack growth, and crack inspection and repair. The resulting information provides the engineer with an assessment of the probability of failure of the structure as a function of operating time and the effect of the inspection procedure. This information can form the basis of inspection planning and retirement-for-cause decisions.
Synchronous Dynamics of a Coupled Shaft/Bearing/Housing System With Auxiliary Support From a Clearance Bearing: Analysis and Experiment
Authors: Lawen James L. , Flowers George T.
Published: February 2015

This study examines the response of a flexible rotor supported by load sharing between linear bearings and an auxiliary clearance bearing. The objective of the work is to develop a better understanding of the dynamical behavior of a magnetic bearing supported rotor system interacting with auxiliary bearings during a critical operating condition. Of particular interest is the effect of coupling between the bearing/housing and shaft vibration on the rotordynamical responses. A simulation model is developed and a number of studies are performed for various parametric configurations. An experimental investigation is also conducted to compare and verify the rotordynamic behavior predicted by the simulation studies. A strategy for reducing sychronous shaft vibration through appropriate design of coupled shaft/bearing/housing vibration modes is identified. The results are presented and discussed.
A Probabilistic Method for the Fatigue Life Assessment of Powder Metallurgy Parts of Aircraft Engines
Authors: Krafft R. , Mosset S.
Published: February 2015

This paper will present a probabilistic approach developed in order to assess the fatigue life of aircraft engine parts (turbine disks) obtained by powder metallurgy technique. First of all, the main issues will be pointed out and the theoretical principles of the method will be described. Then the design implications and the experimental correlation will be emphasised.

The scale effect is a major concern for the fatigue life assessment of a powder metallurgy part. It no longer allows the designer to directly evaluate the life of a massive part from experimental results based on small specimen fatigue tests as it is done in the classical methodology. In order to correctly describe this scale effect, incubation sites (inhomogeneities like ceramic inclusions) must be characterised. The size of these inhomogeneities and their positions in the part appeared to be the most relevant parameters. Hence the methodology developed at Snecma integrates the scale effect scatter through a binomial probability distribution as well as a temperature and stress dependent life evaluation for each inhomogeneity size and position. The life calculation of a part implies an analysis of its whole volume and surface. An iterative process determines the number of cycles corresponding to a global reliability level requirement for the part. The complete methodology is then validated by comparing the calculated initiation distribution with experimental results on small specimens and test disks.
Adiabatic Effectiveness, Thermal Fields, and Velocity Fields for Film Cooling With Large Angle Injection
Authors: Kohli Atul , Bogard David G.
Published: February 2015

The film cooling performance and velocity field were investigated for discrete round holes inclined at an injection angle of 55°. Results are compared to typical round film cooling holes, with an injection angle of 35°. All experiments in this study were performed at a density ratio of DR = 1.6, using cryogenic cooling of the injected air. Centerline and lateral distributions of effectiveness, were obtained for a range of momentum flux ratios. Thermal field and two component mean velocity and turbulence intensity measurements were made at a momentum flux ratio which was within the range of maximum spatially averaged effectiveness. Compared to round holes with 35° injection angle, the 55° holes showed only a slight degradation in centerline effectiveness for low momentum flux ratios, while a significant reduction in effectiveness was seen at high momentum flux ratios. The thermal field for the 55° round holes indicated a faster decay of cooling capacity for the 55° round holes. The high turbulence levels for the 55° round hole coincided with the sharp velocity gradients between the jet and freestream, and the decay of turbulence levels with downstream distance was found to be similar to those for a 35° hole.
Methods of Classical Mechanics Applied to Turbulence Stresses in a Tip Leakage Vortex
Authors: Moore Joan G. , Schorn Scott A. , Moore John
Published: February 2015

Moore et al. measured the six Reynolds stresses in a tip leakage vortex in a linear turbine cascade. Stress tensor analysis, as used in classical mechanics, has been applied to the measured turbulence stress tensors. Principal directions and principal normal stresses are found. A solid surface model, or 3-d glyph, for the Reynolds stress tensor is proposed and used to view the stresses throughout the tip leakage vortex. Modelled Reynolds stresses using the Boussinesq approximation are obtained from the measured mean velocity strain rate tensor. The comparison of the principal directions and the 3-d graphical representations of the strain and Reynolds stress tensors aids in the understanding of the turbulence and what is required to model it.
Modeling of Gas Turbine Fuel Nozzle Spray
Authors: Rizk N. K. , Chin J. S. , Razdan M. K.
Published: February 2015

Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A 2-D fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the air-assist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near critical evaporation. The present investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon (UHC) and carbon monoxide (CO) in atomizer flowfield, information that could support the effort to reduce emission levels of gas turbine combustors.
New Technology Trends for Improved IGCC System Performance
Authors: Anand A. K. , Cook C. S. , Corman J. C. , Smith A. R.
Published: February 2015

The application of gas turbine technology to IGCC systems requires careful consideration of the degree and type of integration used during the system design phase. Although gas turbines provide the primary output and efficiency gains for IGCC systems, as compared with conventional coal fired power generation systems, they are commercially available only in specific size ranges. Therefore, it is up to the IGCC system designer to optimize the IGCC power plant within the required output, efficiency and site conditions by selecting the system configuration carefully, particularly for air separation unit (ASU) integration incorporated with oxygen blown gasification systems.

An IGCC system, based on a generic, entrained flow, oxygen blown gasification system and a GE STAG 109FA combined cycle has been evaluated with varying degrees of ASU integration, two fuel equivalent heating values and two gas turbine firing temperatures to provide net plant output and efficiency results. The data presented illustrate the system flexibility afforded by variation of ASU integration and the potential performance gains available through the continued use of gas turbine advances. Emphasis is place on system design choices which favor either low initial investment cost or low operating cost for a given IGCC system output.
Fiber Fracture in Continuous Fiber Ceramic Composites: Concepts and Observations
Authors: Reifsnider K. , Liao K. , McCormick M. , Tiwari A.
Published: February 2015

The knowledge of fiber behavior in CMCs is rather modest, and models tend to be based on concepts that are less than complete. The present paper addresses several aspects of this problem. Fundamental assumptions for tensile strength models are discussed, and some basic modeling approaches are described. The effects of fiber fracture on the quasi-static stress-strain behavior are described (from physical measurements), and some models of that behavior discussed. Finally, a summary of the “state of affairs” for this subject will be attempted, and the needs for further investigation, especially to support improved modeling, will be presented.
Experimental Investigation of Steady and Unsteady Flow Field Downstream of an Automotive Torque Converter Turbine and Inside the Stator: Part I — Flow at the Exit of Turbine
Authors: Marathe B. V. , Lakshminarayana B. , Maddock Donald G.
Published: February 2015

The objective of this investigation is to understand the steady and the unsteady flow field at the exit of an automotive torque converter turbine and inside the stator with a view towards improving its performance. The measurements were conducted in a stationary frame of reference using a high frequency response five-hole probe and the data were processed to derive the flow properties in the relative (turbine) frame of reference. The experimental data were processed in the frequency domain by spectrum analysis and in temporal-spatial domain by ensemble averaging technique. The flow properties (e.g. pressure and velocity) were resolved into mean, periodic, aperiodic and unresolved components. A velocity profile similar to that of a fully developed flow was observed at all radii. The periodic data in relative reference frame revealed a small separation zone near the suction surface in the core region. The rms values of the unresolved component were found to be significantly higher in this region. The secondary flow vectors show underturning, radially inward flow in the entire passage with a small region of overturning near the separation zone. The overall flow at the turbine exit was nearly two dimensional in nature except in the zone of flow separation. The unsteady flow data shows that unresolved and aperiodic components dominate the unsteadiness in the pressure whereas the periodic components dominate the unsteadiness in velocities and flow angles. Pressure and velocity fluctuations were moderate whereas the flow angle fluctuations were found to be high. The overall flow at the exit of turbine was found to be highly unsteady.
Finite Volume Scheme With Quadratic Reconstruction on Unstructured Adaptive Meshes Applied to Turbomachinery Flows
Authors: Delanaye M. , Essers J. A.
Published: February 2015

This paper presents a new finite volume cell-centered scheme for solving the 2D Euler equations. The technique for computing the advective derivatives is based on a high-order Gauss quadrature and an original quadratic reconstruction of the conservative variables for each control volume. A very sensitive detector identifying discontinuity regions switches the scheme to a TVD scheme, and ensures the monotonicity of the solution. The code uses unstructured meshes whose cells are polygons with any number of edges. A mesh adaptation based on cell division is performed in order to increase the resolution of shocks. The accuracy, insensitivity to grid distortions as well as the shock capturing properties of the scheme are demonstrated for different cascade flow computations.
Dynamic Fatigue Testing of Candidate Ceramic Materials for Turbine Engines to Determine Slow-Crack-Growth Parameters
Authors: Osborne Nora R. , Graves George A. , Ferber Matt K.
Published: February 2015

The purpose of this study was to evaluate the mechanical strength and slow-crack-growth parameter values for two commercially available silicon nitrides, SN-88 and NT164, at three high temperature conditions. Weibull analysis and dynamic fatigue slow-crack-growth parameters were used to characterize the material strength and resistance to slow crack growth at high temperatures for use in life prediction models. Although both materials are commercially available Si3N4, their high temperature behavior was found to be significantly different.
Long-Term Testing of Advanced Ceramics: Concerns, Insights, and Recommendations
Authors: Jenkins Michael G.
Published: February 2015

Advanced ceramics have reached a level of material development to warrant serious consideration for use in advanced heat engine designs. Typically, design requirements based on service conditions may include 25,000 h lifetimes under stresses and temperatures of up to 250 MPa and 1370°C, respectively, with probabilities of failure of <0.1%. To assure that materials meet these stringent requirements requires long-term testing under the service conditions. Tensile tests at 1370°C in ambient air have been conducted on silicon nitride alloys to 5,000 h with reports of 10,000 h tests for silicon carbide. To provide useful data, such long term tests must incorporate such meticulous attention to detail as: strict temperature control (±5°C); accurate temperature measurement (1% of the nominal temperature); close control of grip cooling (±0.1°C) and ambient environment (±0.25°C); stable, high resolution extensometry (±0.5 µm); reliable heating (MTBF>10,000 h) and load control (gravity-controlled, dead load), and responsive data acquisition systems (12-bit, digital collection). Data thus obtained can be used as input into design codes such as NASA CARES/LIFE to predict and confirm reliability/durability.
The Transport of Vortices Through a Turbine Cascade
Authors: van de Wall Allan G. , Kadambi Jaikrishnan R. , Boyle Robert J. , Adamczyk John J.
Published: February 2015

An experiment was conducted to determine how incident vortices created by upstream blade rows, interacted with a downstream turbine cascade. Specifically, the kinematics of the vortex transport through turbine blade passages was investigated. A stationary water table and a flow visualization system using the pH indicator Bromothymol Blue was used to visualize the vortices generated by vortex generators placed upstream of a turbine blade cascade. Two test series were conducted. In the first test series, stationary vortex generators were positioned at various locations along the turbine blade pitch to observe how a steady incident streamwise vortex was transported through the turbine cascade. Observations showed an unsteady vortex response of the streamwise vortex when the incident vortex was located at the stagnation area of the blade. In the second test series, the vortex generators were moved to simulate the relative motion of an upstream blade row. In these tests, the unsteady vortex response was no longer seen at the stagnation region but was instead located at the suction side of the blade. In addition, the breakdown of the vortex varied greatly with the reduced frequency of the incident vorticity and showed an “explosive” type vortex breakdown that occurred at reduced frequencies greater than 8. The dissimilar behavior between the stationary and moving incident vortices indicates that losses and leading edge heat transfer could differ to some degree when determined from a stationary test as opposed to a full stage simulation.
Machine Health Monitoring and Life Management Using Finite Element Based Neural Networks
Authors: Roemer Michael J. , Hong Chi-an , Hesler Stephen H.
Published: February 2015

This paper demonstrates a novel approach to condition-based, health monitoring for rotating machinery using recent advances in neural network technology and rotordynamic, finite-element modeling. A desktop rotor demonstration rig was used as a proof of concept tool. The approach integrates machinery sensor measurements with detailed, rotordynamic, finite-element models through a neural network which is specifically trained to respond to the machine being monitored. The advantage of this approach over current methods lies in the use of an advanced neural network. The neural network is trained to contain the knowledge of a detailed finite-element model whose results are integrated with system measurements to produce accurate machine fault diagnostics and component stress predictions. This technique takes advantage of recent advances in neural network technology that enable real-time machinery diagnostics and component stress prediction to be performed on a PC with the accuracy of finite-element analysis. The availability of the real-time, finite-element based knowledge on rotating elements allows for real-time component life prediction as well as accurate and fast fault diagnosis.
Fuel Spray Characteristics of Gas Turbine Fuel Injectors at Cold Start Conditions
Authors: Koblish Theodore R. , Fox Theodore G. , Patel Subhash G. , Siddiqui Jamil R.
Published: February 2015

Engine starting at extremes of cold ambient and fuel temperatures are a concern to both military and commercial operators of jet engines, but the military in particular needs the capability to quick start under very cold conditions. The ongoing worldwide conversion to JP8 fuel is compromising this ability for older engines developed for use on wide-cut JP4 fuel. The greatly reduced volatility and increased viscosity of JP8 fuel significantly impacts fuel spray angle and droplet size at start conditions resulting in over-long and aborted starts in cold climates.

A program was carried out by Pratt & Whitney and Textron Fuel Systems to investigate and improve the spray qualities of a dual orifice pressure atomizing fuel injector of a commonly used military jet engine in the start to low power range. The primary fuel injector portion was modified to produce a finer droplet size and wider spray angle. A hybrid design with an aerating secondary was also tested. Droplet diameter and spray angles were measured to −40°F (−40°C) temperatures. Variations in fuel flow rate and fuel type were also investigated. It was found that cold fuel had an adverse effect on spray qualities for the all pressure atomizing nozzles, but the hybrid injector was less affected and produced superior sprays at all conditions on the primary portion. Improvements in the all pressure atomizing design resulted in lesser but still significant benefits.
Model Based Diagnostics and Prognosis System for Rotating Machinery
Authors: Bankert Raymond J. , Singh Vinod K. , Rajiyah Harindra
Published: February 2015

A PC-based automated mechanical vibration diagnostic and prognosis system for rotating machinery is under development by integrating AI-expert system-based interpretative capabilities with rotor dynamics based modeling and numerical optimization techniques. Presented here are the details involved while generating a rotor dynamic simulator: A turbine-generator is properly modeled using the finite element approach to compute steady-state response. The bearing stiffness and damping properties are computed by numerically solving the Reynold’s equation. An optimizer software has been interfaced with the rotor dynamics code for the solution of nonlinear unconstrained function minimization. A finite element based closed form approach has been adopted to compute the gradients of the objective function. The model is perturbed by the optimizer to match the results with simulated field measurement.

The model based optimization technique has been demonstrated on a 120 mass, 6 bearing rotor system. After optimization, the responses and mass unbalance converge to their goal (field) values. To date, feasibility studies show encouraging results to differentiate between mass unbalance and misalignment for realistic systems using this methodology.
The Effect of Primary Zone Design on the Performance of a High Heat Release Rate Propulsion Engine Combustor
Authors: Myers G. , Cardenas M. , Reynolds B. , Srinivasan R. , Arana C.
Published: February 2015

The primary reaction zone of a modern propulsion engine combustion system has a profound effect on overall combustor performance, including efficiency, lean stability, exit temperature pattern factor, and emissions production rates. A unique full-annular, throughflow combustion system with interchangeable fuel injectors, dome mixing devices, and liners was used to evaluate the effects of several primary zone design variables on efficiency and exit temperature distribution. The combustor was tested in a rig designed for extreme exit temperatures, at heat release rates up to 30 M Btu/hr-ft3-atm (0.31 kW/M3-atm) and exit temperatures in excess of 3500F (1927C), through a range of overall fuel/air ratios up to stochiometric. An automated, six-port, rotating exit gas sampling system was used to map the exit gas concentrations for determining gas temperatures and combustion efficiency. Both liquid (JP-4) and natural gas fuels were used to examine the impact of evaporation and fuel momentum effects. Gaseous fuel was injected through nozzles designed to mimic the initial fuel spatial distribution and spray cone angle of the liquid nozzles. Thick thermal barrier coatings on the liners eliminated the need for and interference of film cooling. The high reference velocity, short residence time, and absence of any dilution zone further highlighted the primary zone design impact on exit conditions. Test results show that combustor efficiency becomes volume-limited at a point lean of stochiometric, with both the shape of the efficiency curve and the fuel/air ratio for maximum efficiency dependent on the primary zone design and fuel type. The average exit temperature raidal profile was outside diameter (OD)-peaked at low fuel/air ratios, rotating toward a flat profile at stochiometric for all of the configurations.
Mixing of Multiple Jets in a Can Combustor
Authors: Ebbinghaus Alexandra , Swithenbank Jim
Published: February 2015

Computational fluid dynamics and experiments have been used to study the mixing of multiple jets in a can combustor. An existing configuration having a poor exit temperature profile was chosen as the baseline case. In the computations, the air split and axial location of the primary, secondary and dilution jets were held constant while the number of jets at each location were varied parametrically to determine their effect on the exit temperature profile. As a result of these studies, two configurations were selected for experimental verification of the anticipated improved performance. The modified design was found to have a more uniform exit temperature profile than the baseline case. Thus the experimental results generally confirmed the predictions and demonstrated the potential utility of CFD as a design tool.
The 501D5A Combustion Turbine
Authors: Hintz Douglas E.
Published: February 2015

Westinghouse is now offering its latest upgrade of the 501D5 family of combustion turbines. This upgrade engine, designated 501D5A, is based on recent technical advancements successfully incorporated in the 251B12 and 701DA engines. These advancements primarily focus on compressor end modifications for increased mass flow and turbine end modifications for a modest increase in rotor inlet temperature. In addition, modifications were made to the combustion section for use of low emissions combustion systems. This paper will describe these changes incorporated in the upgraded 501D5, along with improvements associated with engine efficiency, which have resulted in an engine with over 10 percent increased power and over 2 percent improved simple cycle heat rate.
Design, Part Load and Transient Operation of Combined Cycle Plants With Water Flashing
Authors: Dechamps P. J.
Published: February 2015

The last decade has seen remarkable improvement in gas turbine based power generation technologies, with the increasing use of natural gas-fuelled combined cycle units in various regions of the world. The struggle for efficiency has produced highly complex combined cycle schemes based on heat recovery steam generators with multiple pressure levels and possibly reheat. As ever, the evolution of these schemes is the result of a technico-economic balance between the improvement in performance and the increased costs resulting from a more complex system.

This paper looks from the thermodynamic point of view at some simplified combined cycle schemes based on the concept of water flashing. In such systems, high pressure saturated water is taken off the high pressure drum and flashed into a tank. The vapour phase is expanded as low pressure saturated steam or returned to the heat recovery steam generator for superheating, whilst the liquid phase is recirculated through the economizer.

With only one drum and three or four heat exchangers in the boiler as in single pressure level systems, the plant might have a performance similar to that of a more complex dual pressure level system. Various configurations with flash tanks are studied based on commercially available 150 MW-class E-technology gas turbines and compared with classical multiple pressure level combined cycles. Reheat units are covered, both with flash tanks and as genuine combined cycles for comparison purposes. The design implications for the heat recovery steam generator in terms of heat transfer surfaces are emphasized.

Off-design considerations are also covered for the flash based schemes, as well as transient performances of these schemes, because the simplicity of the flash systems compared to normal combined cycles significantly affects the dynamic behaviour of the plant.
2D Electrochemical Airfoil Machining Process Model
Authors: Nied H. A. , Lamphere M. S.
Published: February 2015

A 2D Electro-Chemical Machining (ECM) process model was developed to aid with tooling design and process optimization by simulation of the ECM process. The boundary element method (BEM) was used to numerically solve the field equations of the process model. The electrochemical anodic reaction was furnished by Faraday’s Law, which provided the relationship for the rate of dissolution at the surface of the workpiece as a function of charge transfer. Accordingly, the workpiece shape change and mass of metal removed by the machining process can be determined as a function of time. The process model includes a library of workpiece material and electrolyte combinations for predicting the electrochemical machining behavior, e.g., titanium alloy 6Al-4V and NaCl electrolytes. These metal/electrolyte combinations are of special interest in the aircraft engine industry for manufacturing heat-resistant, rotary components with complex geometry such as airfoil blades. The major features of the numerical computer program are briefly described with a selected example of machining a typical fan blade. Preliminary comparison of the numerical predictions with the nominal airfoil geometry showed good agreement and is discussed below.
Leading Edge Film Cooling Effects on Turbine Blade Heat Transfer
Authors: Garg Vijay K. , Gaugler Raymond E.
Published: February 2015

An existing three-dimensional Navier-Stokes code (Arnone et al., 1991), modified to include film cooling considerations (Garg and Gaugler, 1994), has been used to study the effect of spanwise pitch of shower-head holes and coolant to mainstream mass flow ratio on the adiabatic effectiveness and heat transfer coefficient on a film-cooled turbine vane. The mainstream is akin to that under real engine conditions with stagnation temperature = 1900 K and stagnation pressure = 3 MPa. It is found that with the coolant to mainstream mass flow ratio fixed, reducing P, the spanwise pitch for shower-head holes, from 7.5 d to 3.0 d, where d is the hole diameter, increases the average effectiveness considerably over the blade surface. However, when P/d = 7.5, increasing the coolant mass flow increases the effectiveness on the pressure surface but reduces it on the suction surface due to coolant jet lift-off. For P/d = 4.5 or 3.0, such an anomaly does not occur within the range of coolant to mainstream mass flow ratios analyzed. In all cases, adiabatic effectiveness and heat transfer coefficient are highly three-dimensional.
The GUIde Consortium: Government, Universities, and Industry Working Together to Develop New Technologies
Authors: Richardson Scott M. , Griffin Jerry H.
Published: February 2015

The GUIde Consortium, a joint government, university, and industrial program to fund research in turbomachinery bladed disk forced response, is described. The development of the Consortium was prompted by the fact that excessive vibration of bladed disks in fans, compressors, and turbines is an industry-wide problem that impacts turbine engine development and reliability. This paper describes the forces behind the development of the Consortium, its structure, including the costs and benefits to each of the participating organizations, and a reflection of the lessons learned from the open interaction between the GUIde members. Finally, the future of the organization is discussed with a look at the evolution of the program to face the changes in technical and financial priorities within the industry.
Joint Dynamic Airbreathing Propulsion Simulations Partnerships (JDAPS)
Authors: Davis M. W. , Owen A. K. , O’Brien W. F. , Cousins W. T.
Published: February 2015

The Joint Dynamic Airbreathing Propulsion Simulations (JDAPS) is a partnership of government, university, and industry organizations for the purpose of developing and applying turbine engine/component numerical simulations to aid in the understanding of turbine engine dynamic behavior. The primary focus of the simulations being developed by the partnership is to aid in the understanding of gas turbine dynamic behavior such as engine surge, compressor rotating stall, the effects of inlet distortion, and dynamic events during engine start. The insight gained from the development and application of these simulations provides design guidance for improved turbine engine performance and operability. By pooling resources, the organizations involved in the JDAPS partnership have access to more support, both financial and technical, than any one organization could afford on its own. Such synergy makes each organization’s return on investment very high.
Novel Compressed Air Energy Storage (CAES) Systems Applying Air Expanders
Authors: Shnaid Isaac , Weiner Dan , Brokman Shimshon
Published: February 2015

In Compressed Air Energy Storage (CAES) systems, off-peak electric energy is consumed by air compressors that charge CAES reservoirs. During peak load hours, air released from the CAES reservoir expands, producing electric power. Two novel CAES systems, improving their reliability and efficiency, are introduced.

The first system is the CAES Plant Integrated with a Gas Turbine (CAESIGT), in which 40 percent of the power output is produced by a standard gas turbine, and 60 percent by an air expander utilizing compressed air that is preheated by the exhaust gases of the gas turbine. For certain initial parameters of the compressed air, its temperature after expansion becomes lower than the ambient temperature. This cold air can be used as a source for refrigeration of the gas turbine inlet air and for other purposes.

In the CAES system of the second type, multistage expansion of compressed air is applied. Reheating air between expander stages is provided either by refrigerated substances, by heat sources from surroundings, or by non fuel heat sources such as the waste heat from industry, solar ponds, etc.

Thermodynamic and economic analyses of the novel CAES systems are carried out.
Gas Turbine Inlet Air Cooling and the Effect on a Westinghouse 501D5 CT
Authors: Kohlenberger Chuck
Published: February 2015

The temperature of the air entering a gas turbine prime mover has a dramatic effect on its performance, including output, heat rate, and exhaust gas temperature (EGT). These variations are easily observed in actual operation and by reference to generic gas turbine (GT) performance curves. The gross capacity increase of a GT operating at 40F (8C) inlet compared to operation at 102F (70C) is 28%. The gross reduction in heat rate for this 62F (16.7C) differential is 6%, and the exhaust gas temperature is reduced 5%. Since the overall mass flow through the GT is increased through the cooling process, the added energy available in the heat recovery steam generator (HRSG), is increased 8% The significant improvements in GT output and efficiency which can be achieved by maintaining lower inlet air temperatures encourage the manufacturer, systems engineer, owner, and operator of GT facilities to consider seriously the implementation of a gas turbine inlet air cooling (GTIAC) system.

GTIAC systems have proven to produce some very excellent economic paybacks due to increased power output, EG mass flow, and reduced heat rates. Generic gross performance factors are plotted (See Figure 1) against inlet air temperature compared to International Standards Organization (ISO) conditions.
Crack Growth Simulation and Life Prediction Using BEM
Authors: Aliabadi M. H. , Niku S. , Adey R.
Published: February 2015

In this paper an application of the dual boundary element method to the analysis of two- and three-dimensional mixed-mode crack growth is presented using a boundary element software BEASY. The crack growth processes are simulated numerically using the maximum principal stress criterion and the minimum strain energy density criterion. The fatigue life predictions are evaluated using the generalized formula presented in FLAGRO. Result of the analysis are presented for two- and three-dimensional crack problems.