bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Velocity and Temperature Distribution at the Hole Exit on Film Cooling of Turbine Blades
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 coolant velocity and temperature distribution at the hole exit on the heat transfer coefficient on three film-cooled turbine blades, namely, the C3X vane, the VKI rotor, and the ACE rotor. Results are also compared with the experimental data for all the blades. Moreover, Mayle’s transition criterion (Mayle, 1991), Forest’s model for augmentation of leading edge heat transfer due to free-stream turbulence (Forest, 1977), and Crawford’s model for augmentation of eddy viscosity due to film cooling (Crawford et al., 1980) are used. Use of Mayle’s and Forest’s models is relevant only for the ACE rotor due to the absence of shower-head cooling on this rotor. It is found that, in some cases, the effect of distribution of coolant velocity and temperature at the hole exit can be as much as 60% on the heat transfer coefficient at the blade suction surface, and 50% at the pressure surface. Also, different effects are observed on the pressure and suction surface depending upon the blade as well as upon the hole shape, conical or cylindrical.
The Effects of Adverse Pressure Gradients on Momentum and Thermal Structures in Transitional Boundary Layers: Part 1 — Mean Quantities
Authors: Mislevy Scott P. , Wang Ting
Published: February 2015

The effects of adverse pressure gradients on the thermal and momentum characteristics of a heated transitional boundary layer were investigated with free-stream turbulence ranging from 0.3 to 0.6%. The acceleration parameter, K=vU¯∞2dU¯∞dx, was kept constant along the test section. Both surface heat transfer and boundary layer measurements were conducted. The boundary layer measurements were conducted with a three-wire probe (two velocity wires and one temperature wire) for two representative cases, K1=−0.51 × 10−6 and K2=−1.05 × 10−6.

The surface heat transfer measurements were conducted for K values ranging from −0.045 × 10−6 to −1.44 × 10−6 over five divergent wall angles. The Stanton numbers of the cases with adverse pressure gradients were greater than that of the zero-pressure-gradient turbulent correlation in the low-Reynolds number turbulent flow, and the difference increased as the adverse pressure gradient was increased.

The adverse pressure gradient caused earlier transition onset and shorter transition length based on Rex, Reδ*, and Reθ in comparison to zero-pressure-gradient conditions. As expected, there was a reduction in skin friction as the adverse pressure gradient increased. In the U+-Y+ coordinates, the adverse pressure gradients had a significant effect on the mean velocity profiles in the near-wall region for the late-laminar and early transition stations. The mean temperature profile was observed to precede the velocity profile in starting and ending the transition process, opposite to what occurred in favorable pressure gradient cases in previous studies. A curve fit of the turbulent temperature profile in the log-linear region for the K2 case gave a conduction layer thickness of Y+=9.8 and an average Prt=0.71. In addition, the wake region of the turbulent mean temperature profile was significantly suppressed.
Transient Heat Transfer Experiments in a Linear Cascade via an Insertion Mechanism Using the Liquid Crystal Technique
Authors: Hoffs A. , Bolcs A. , Harasgama S. P.
Published: February 2015

An insertion mechanism for a linear cascade allowing the displacement of one measurement airfoil to conduct transient heat transfer experiments is introduced. A basic feature of the system is its capability to work in a continously running tunnel driven by a compressor at steady state conditions. The experiment is initiated by pulling the measurement airfoil very rapidly through the sidewalls of the cascade by means of a pneumatic cylinder. Heat transfer measurements were obtained on a turbine airfoil at different exit Mach numbers up to M=0.8 and exit Reynolds numbers up to Re=1.2E6. The transient liquid crystal method was used applying a digital image processing system capable of recording and storing the optical signal in real time. Comparisons were performed with measurements conducted in the same test facility using the naphthalene sublimation technique as well as thin film gauges. Calculations were made with a two-dimensional boundary layer code.
Multiple Jets in a Crossflow: Detailed Measurements and Numerical Simulations
Authors: Ajersch Peter , Zhou Jian-Ming , Ketler Steven , Salcudean Martha , Gartshore Ian S.
Published: February 2015

The fluid mechanics and heat transfer characteristics of film cooling is three-dimensional and highly complex. To better understand this problem, an experimental study was conducted in a low speed wind tunnel on a row of six rectangular jets injected at 90° to the crossflow (main stream flow). The jet-to-crossflow velocity ratios (blowing ratios) examined were 0.5, 1.0, and 1.5, and the jet spacing-to-jet width ratio was 3.0. No significant temperature difference between jet and crossflow air was introduced. Mean velocities, and six flow stresses were measured using a three-component laser Doppler velocimeter operating in coincidence-mode. Seeding of both jet and cross-stream air was achieved with a commercially available smoke generator. Flow statistics are reported in the form of vector plots, contours, and x-y graphs, showing velocity, turbulence intensity, and Reynolds stresses.

To complement the detailed measurements, flow visualization was accomplished by transmitting the laser beam through a cylindrical lens, thereby generating a narrow, intense sheet of light. Jet air only was seeded with smoke, which was illuminated in the plane of the light sheet. Therefore, it was possible to record on video tape the trajectory and penetration of the jets in the crossflow. Selected still images from the recordings are presented.

Numerical simulations of the observed flow field were made by using a multi-grid, segmented, k-ε CFD code. Special near wall treatment included a non-isotropic formulation for the effective viscosity, a low Re model for k, and an algebraic model for the length scale. Comparisons between the measured and computed velocities show good agreement for the non-uniform mean flow at the jet exit plane. Velocities and stresses on the jet centerline downstream of the orifice are less well predicted, probably because of inadequate turbulence modeling, while values off the centerline match those of the experiments much more closely.
Film Effectiveness Over a Flat Surface With Air and CO2 Injection Through Compound Angle Holes Using a Transient Liquid Crystal Image Method
Authors: Ekkad Srinath V. , Zapata Dyrk , Han Je-Chin
Published: February 2015

This paper presents detailed film effectiveness distributions over a flat surface with one row of injection holes inclined streamwise at 35° for three blowing ratios (M=0.5, 1.0, 2.0). Three compound angles of 0°, 45°, and 90° with air (D.R.=0.98) and CO2 (D.R.=1.46) as coolants are tested at an elevated free-stream turbulence condition (Tu≈8.5%). A transient liquid crystal technique is used to measure local heat transfer coefficients and film effectiveness. Detailed film effectiveness results are presented near and around film injection holes. Compound angle injection provides higher film effectiveness than simple angle injection for both coolants. Higher density injectant produces higher effectiveness for simple injection. However, lower density coolant produces higher effectiveness for a large compound angle of 90°. The detailed film effectiveness obtained using the transient liquid crystal technique, particularly in the near hole region, provided a better understanding of the film cooling process in gas turbine components.
Effect of Surface Roughness on Local Heat Transfer and Film Cooling Effectiveness
Authors: Barlow Douglas N. , Kim Yong W.
Published: February 2015

An experimental investigation of film cooling on rough surfaces has been accomplished at a Reynolds number and dimensionless boundary layer momentum thickness found in current high performance first stage turbine vanes. A transient experimental method using thermochromic liquid crystals is employed to determine both local heat transfer coefficients and film cooling effectiveness values on planar rough surfaces. Two surface roughness configurations are investigated with a single row of cooling holes spaced three diameters apart and inclined 30° to the mainstream flow. The mainstream turbulence level at the point of film injection is 8.5% and the density ratio considered is approximately 1.0. The influence of roughness on the centerline film cooling effectiveness, laterally averaged film cooling effectiveness, laterally averaged heat transfer coefficients, as well as area averaged values are presented. It is found that the presence of roughness causes a decrease in the film cooling effectiveness over that of the smooth surface for the range of experimental parameters considered in this study. In addition, significant lateral smoothing in film cooling effectiveness distribution is observed for the rougher surfaces. Measured heat transfer coefficients on rough surfaces show a trend of monotonic increase with blowing ratio. However, such increase is not as great as that for the case of smooth surface.
The Discharge Coefficient of Flared Film Cooling Holes
Authors: Hay N. , Lampard D.
Published: February 2015

The coefficient of discharge (Cd) of flared film cooling holes is reported for a range of pressure ratios, geometries and flow conditions. The geometry of the holes used was typical of present day designs produced by the method of electrical discharge machining or spark erosion. Cd data are given for normal (90°) holes and for 30° inclined holes. The effects of the following geometrical and flow parameters have been investigated and are reported.

Effect of the length of the cylindrical portion of the hole prior to the flare.

Effect of the deletion of the layback of the hole flare

Effect of the presence of cross flow on the inlet to and on the outlet from the hole.

Effect of the orientation of the cross flow relative to the axial direction of the hole.

The flare increases Cd over that for a cylindrical hole. Eliminating the layback has little effect on Cd, but reducing the length of the cylindrical portion has a marked adverse effect when an inlet cross flow is present. As for cylindrical holes, an inlet cross flow reduces Cd for normal holes, but flared holes can maintain higher Cd’s than cylindrical holes, provided that the cylindrical inlet to the flare is sufficiently long.
An Experimental Study to Compare the Naphthalene Sublimation With the Liquid Crystal Technique in Compressible Flow
Authors: Häring M. , Hoffs A. , Bolcs A. , Weigand B.
Published: February 2015

The naphthalene sublimation and the liquid crystal technique are two methods being used for measurements of the heat transfer coefficient on turbine airfoils. In this paper the results obtained with the two methods for the same compressible flow conditions are compared.

The measurements were performed in a free jet test facility on a flat plate and a cylinder. The free stream Mach number ranged from M=0.4 to 0.8. The naphthalene sublimation technique was applied to obtain the local Nusselt number, based on the Sherwood number, applying a new analogy function (Häring, Weigand (1995)). These results were compared with measurements on the same test arrangement using the transient liquid crystal technique. A good agreement between the two measurement techniques and correlations was found for the entire Mach number range. An application of both techniques on a turbine airfoil confirmed this observation.

The sublimation technique was also applied to measure the local heat transfer coefficient on a turbine vane at exit Mach numbers up to M=0.9 and exit Reynolds numbers up to Re=1.8e6. The experimental results were compared with the two dimensional boundary layer code TEXSTAN (Crawford, 1986).
The Influence of Large Scale High Intensity Turbulence on Vane Heat Transfer
Authors: Ames Forrest E.
Published: February 2015

An experimental research program was undertaken to examine the influence of large scale high intensity turbulence on vane heat transfer. The experiment was conducted in a four vane linear cascade at exit Reynolds numbers of 500,000 and 800,000 based on chord length corresponding to exit Mach numbers of 0.17 and 0.27. Heat transfer measurements were made for four inlet turbulence conditions including a low turbulence case (Tu ≅ 1%), a grid turbulence case (Tu ≅ 7.5%), and two levels of large scale turbulence generated with a mock combustor at two upstream locations (Tu ≅ 12% & Tu ≅ 8%).

The heat transfer data demonstrated that the length scale, Lu, has a significant effect on stagnation region and pressure surface heat transfer. The average heat transfer augmentation over the pressure surface was found to scale reasonably well on the relative level of dissipation. The stagnation region heat transfer correlated well on the {Tu ReD5/12 (Lu/D)−1/3} parameter of Ames and Moffat (1990). The dependence of heat transfer augmentation on Reynolds number was estimated to scale on the 1/3 power for the pressure surface. The absolute level of heat transfer augmentation was found to be highest near the stagnation region. The combustor closely coupled to the cascade produced an average augmentation on the pressure surface of 56 percent at a Reynolds number of 800,000.
Performance Improvement Through Indexing of Turbine Airfoils: Part 2 — Numerical Simulation
Authors: Griffin Lisa W. , Huber Frank W. , Sharma Om P.
Published: February 2015

An experimental/analytical study has been conducted to determine the performance improvements achievable by circumferentially indexing succeeding rows of turbine stator airfoils. A series of tests was conducted to experimentally investigate stator wake clocking effects on the performance of the space shuttle main engine (SSME) alternate turbopump development (ATD) fuel turbine test article (TTA). The results from this study indicate that significant increases in stage efficiency can be attained through application of this airfoil clocking concept. Details of the experiment and its results are documented in part 1 of this paper. In order to gain insight into the mechanisms of the performance improvement, extensive computational fluid dynamics (CFD) simulations were executed. The subject of the present paper is the initial results from the CFD investigation of the configurations and conditions detailed in part 1 of the paper.

To characterize the aerodynamic environments in the experimental test series, two-dimensional (2D), time-accurate, multistage, viscous analyses were performed at the TTA midspan. Computational analyses for five different circumferential positions of the first stage stator have been completed. Details of the computational procedure and the results are presented. The analytical results verify the experimentally demonstrated performance improvement and are compared with data whenever possible. Predictions of time-averaged turbine efficiencies as well as gas conditions throughout the flow field are presented. An initial understanding of the turbine performance improvement mechanism based on the results from this investigation is described.
Film Cooling From Spanwise Oriented Holes in Two Staggered Rows
Authors: Ligrani Phillip M. , Ramsey Anthony E.
Published: February 2015

Adiabatic effectiveness and iso-energetic heat transfer coefficients are presented from measurements downstream of film-cooling holes inclined at 30 degrees with respect to the test surface in spanwise/normal planes. With this configuration, holes are spaced 3d apart in the spanwise direction and 4d in the streamwise direction in two staggered rows. Results are presented for an injectant to freestream density ratio near 1.0, and injection blowing ratios from 0.5 to 1.5. Spanwise-averaged adiabatic effectiveness values downstream of the spanwise/normal plane holes are significantly higher than values measured downstream of simple angle holes for x/d<25–70 (depending on blowing ratio) when compared for the same normalized streamwise location, blowing ratio, and spanwise and streamwise hole spacings. Differences are principally due to different coalescence of injectant accumulations from the two different rows of holes, as well as significantly different lift-off dependence on momentum flux ratio. Spanwise-averaged iso-energetic Stanton number ratios are somewhat higher than ones measured downstream of other simple and compound angle configurations studied. Values range between 1.0 and 1.41, increase with blowing ratio at each streamwise station, and show little variation with streamwise location for each value of blowing ratio tested.
Dual-Use Conversion of a High Mach Number Jet Engine Test Cell for Industrial Gas Turbine Low-Emission Combustor Development
Authors: Pillsbury P. W. , Ryan W. R. , Moore J. R.
Published: February 2015

With the recent trend of reducing U.S. military expenditures, it has become desirable to develop dual use of certain Department of Defense facilities. These efforts have a commercial purpose, while still retaining a military benefit. The goals of these efforts are to make U.S. business more competitive in world markets, to develop the technology to solve pressing national problems, and to maintain intact the necessary talent pool and equipment for possible military needs. In a recent initiative described in this paper, test cell equipment at the Arnold Engineering Development Center, Arnold AFB, Tennessee, was modified and expanded to allow development by the Westinghouse Electric Corporation of low-emission combustors for heavy-duty gas turbines for commercial power generation.
Field Test Results of a Dry Low NOx Combustion System for the MS3002J Regenerative Cycle Gas Turbine
Authors: Maughan James R. , Elward Kevin M. , De Pietro Simon M. , Bautista Paul J.
Published: February 2015

A dry low NOx combustion system for the MS3002J regenerative cycle gas turbine has been developed and successfully installed at two pipeline compressor stations. Preparation for the DLN retrofits began with initial field testing of the conventional system intended to characterize some of the unique features of the two-shaft, regenerative cycle machine that might impact the proposed premixed combustor design. Combustor transition pieces were instrumented with gas sampling probes for CO2 analysis. Fuel flow to each combustor was measured and controlled. Consequently, the fuel/air ratio, exit temperature, and air flow for each combustor could be determined over the operating range.

The dry low NOx combustion system for the MS3002J R/C is based on an existing system for the MS6001B gas turbine. A description of the hardware and system operation is given. Because of the relatively high inlet temperature of the MS3002J R/C (950 F), some portions of the liner required highly efficient effusion cooling. A new transition piece seal was developed to reduce leakage and ensure uniform air flow throughout the machine. A control strategy was developed to guide the machine through diffusion modes of operation at low load to premixed combustion at higher loads. Results showed acceptable component temperatures throughout. Emissions measurements were consistent with previous laboratory measurements and met design targets of 33 ppm NOx and 25 ppm CO (at 15% O2) over the required range. The fuel split between the two premixed flame zones was controlled over the load range of the turbine to optimize CO, NOx, and liner temperatures. Because of the high inlet temperature and low overall temperature rise, dynamic pressure activity was low. Following a successful inspection after 6000 hours of operation, the hardware inspection interval has been set at 12000 hrs.
Mechanisms of Coke Formation in Gas Turbine Combustion Chambers
Authors: Brandauer M. , Schulz A. , Wittig S.
Published: February 2015

New gas turbine combustor designs are developed to reduce pollutant and NOx-emissions. In these new combustors, the formation of carbonaceous deposits, especially in prevaporizers, affects the reliablility and effectiveness of operation. To avoid deposits, a detailed knowledge of the origins and mechanisms of formation is required.

To obtain a deeper insight, the phenomena were studied systematically. The deposits under consideration show differing characteristics suggesting more than one formation mechanism in the combustor. Consequently, the primary goal was to identify the formation mechanisms and, subsequently, to simulate the mechanisms under well-defined conditions in bench tests for determining the relevant parameters of deposit build-up. The mechanisms of formation were identified based on the properties of the deposits in the combustion chamber. In order to characterize the deposits, physical and chemical analysis techniques were utilized.

In summary, tests and numerical predictions identified two major paths of formation: a deposit build-up resulting from flame products such as soot or coked droplets and a deposit build-up resulting from liquid fuel impinging the wall accompanied with chemical reactions at the wall.

The deposits caused by fuel droplet impingement were intensively studied in bench tests. In analyzing the processes, the influence of wall temperature, fuel composition, and the oxygen content in the environment is shown in detail. In addition, the importance of thermal instabilities of the fuel, previously studied under fuel supply system conditions, is demonstrated for a deposit formation inside a combustion chamber.
3D Flow Structures and Operating Characteristic of an Industrial Fluid Coupling
Authors: Huitenga H. , Formanski T. , Mitra N. K. , Fiebig M.
Published: February 2015

A liquid circulating between an input rotor and an output rotor transmits power in a fluid coupling. Insight into the flow field is required to influence the transmission behaviour. Parameter studies of model geometries of fluid couplings were presented previously. Laminar and turbulent flow fields and characteristic curves of an actual industrial fluid coupling have been computed from the numerical solution of the three-dimensional, nonsteady Navier-Stokes equations on a body fitted rotating coordinate system. Results show the complex flow structure and vortices that determine the transported angular momentum. Comparison with measured torque suggests that the turbulence modeling by standard k-ϵ model may be inadequate at large slip.
The Westinghouse/Rolls-Royce WR-21 Gas Turbine Variable Area Power Turbine Design
Authors: Cox John C. , Hutchinson David , Oswald James I.
Published: February 2015

The Westinghouse/Rolls-Royce WR-21 marine gas turbine with an intercooled, recuperated thermodynamic cycle utilises exhaust heat to provide excellent efficiency not only at full power but also at part power. Vital to the success of the engine and the optimisation of fuel consumption is the Variable Area Nozzle (VAN) which is used to control turbine capacity across the power range. By continuously monitoring and controlling turbine capacity, the heat recovered by the recuperator is optimised across the power range.

The efficiency of the power turbine variable stage at low power (low flow) and its ability to deliver full power (high flow) is vital to the success of the engine. Success also requires precise control of the variable vane, easy maintenance and good reliability in a hot, mechanically hostile environment.

This paper describes the aerodynamic and mechanical design, rig verification and early engine experience of the variable power turbine stage.
CFD in the Design of Marine Gas Turbine Inlet Air Systems
Authors: Fewel Kenneth J. , Kierzkowski Frank J.
Published: February 2015

This paper discusses the design of marine gas turbine intake systems and how computational fluid dynamics (CFD) is being used to aid in the design of these systems.

Three major types of intake separators and two state-of-the-art intake separators are discussed. A brief summary is included on salt-in-air loadings and requirements as specified by the United States Navy and the British Royal Navy so that typical performance requirements can be understood.

The paper covers CFD basics, including grid creation and analysis and evaluation of single-phase flows. The implications for design are then discussed. Finally, marine intake systems using CFD are illustrated with graphics of analyses. The results and conclusions of these projects are presented.
API Standard 616: Scopes for Different Interpretations
Authors: Roy G. K.
Published: February 2015

The intention of API standard 616 is to help manufacturer, or buyer of gas turbines in specifying the equipment, and is based on experience and good engineering practices over many years. Like any other standard, the definitions are broad-based to cover possibly the majority of manufacturers, and are based on experiences gathered in the industries in general. However, different interpretations are possible on some of the clauses of the standard.

Each gas turbine customer has specific requirements, and the manufacturer’s objective is “Customer Focus” which means it has to fulfill the requirements of the customer totally, or even to take it a step further identify the needs that the customer has not even recognized. The common objective of providing a machine satisfying the specific requirements is difficult to achieve, when attempts are made to bridge the gaps between the customer and the manufacturer through the API standard 616.

Few clauses of API standard 616 are controvertial in nature, where possibly more than one explanations are possible, and a more clear guide-line from API is needed to direct the users and the manufacturers. Turbine firing temperature, rotor insensitivity test, API 614, turbine baseplate, post-test bearing inspection, etc are some of them. In this paper these were discussed with some of the available gas turbine purchasing standards.

It was concluded that standard like API 616 needs to be general in nature, so that it can be used for each specific customer, however, definitions and its’ scopes need to be clearly identified to avoid mis-use or incorrect use of the standard.
Study and Application of Hemispheric Cavities for Surface Heat Transfer Augmentation
Authors: Schukin A. V. , Kozlov A. P. , Agachev R. S.
Published: February 2015

Results of experimental study of heat transfer and flow phenomena associated with application of hemispheric cavities to augment convective heat transfer are presented. Study is performed for different geometries and various flow parameters, including turbulence.

Experimental correlations for the curved surfaces applicable to gas turbine internal airfoil cooling are obtained and analyzed for both heat transfer and pressure losses. Effectiveness of the augmentation technique, considering a simplicity of fabrication process, is emphasized.
Modelling and Recoupling the Control Loops in a Heavy-Duty Gas Turbine Plant
Authors: Crosa G. , Ferrari G. , Trucco A.
Published: February 2015

This paper presents a dynamic simulation of a single shaft heavy-duty gas turbine plant, suitable for gas-steam combined cycles. The plant is operated at maximum gas turbine exhaust temperature, using variable inlet guide vanes (VIGV) as control.

In the first section, a non-linear lumped parameter mathematical model is described: it includes a control system representative of those controls normally utilised by industry today. Some dynamic responses of a controlled plant taken as an example are presented.

In the second section, a different control system is proposed, operating with no interaction between the speed and exhaust temperature loops. To this aim, a linear model in the frequency domain of the uncontrolled plant is obtained, starting from the non-linear model in the time domain. Assuming that each one of manipulated variables influences only one of the controlled variables (VIGV only the exhaust gas temperature and the fuel mass rate only the load), the transfer functions of two new blocks have been obtained. To compensate for the system non linearity, the calculations are repeated for different load levels. The new control feature can offer advantages in the time response of the regulated plant, especially in the operating range where the airflow can be modulated by the VIGV at constant fuel firing temperature.
CARS Temperature and LDA Velocity Measurements in a Turbulent, Swirling, Premixed Propane/Air Fueled Model Gas Turbine Combustor
Authors: Schmidt Stephan E. , Hedman Paul O.
Published: February 2015

This paper present results from a research program being conducted at the Advanced Combustion Engineering Research Center (ACERC) at Brigham Young University (BYU). This study is part of a comprehensive effort supported by the Advanced Gas Turbine Systems Research (ATS) Program headquartered at the South Carolina Energy Research and Development Center, Clemson, South Carolina. The objective of this study was to characterize a turbulent premixed propane/air flame in a model combustor that simulates the characteristics of a utility gas turbine engine. The program’s long term goal is to develop and commercialize ultra-high efficiency, environmentally superior, and cost competitive gas turbine systems for base-load applications in the utility, independent power producer, and industrial markets.

This paper focuses on the following four areas of the investigation: 1) a series of digitized video images to document the effect of fuel equivalence ratio and swirl number on flame structure, 2) LDA velocity measurements to quantify the flow structure, 3) CARS gas temperature measurements to determine the temperature field in the combustor, and 4) local continuity and energy release in differential elements throughout the flame zone.
Application of Catalytic Combustion Technology to Industrial Gas Turbines for Ultra-Low NOx Emissions
Authors: Dalla Betta Ralph A. , Schlatter James C. , Nickolas Sorento G. , Razdan Mohan K. , Smith Duane A.
Published: February 2015

An operating cycle had been developed for a catalytic combustion system applied to the Allison 501-KB7 engine. This cycle used overboard bleed of diffuser air to maintain a high fuel/air ratio at the catalyst and thus achieve a high combustor outlet temperature with attendant low CO and UHC emissions. For the design point of this engine, the emissions measured at full pressure and temperature in a subscale catalyst test rig were <1 ppm NOx and <2 ppm CO and UHC. Tests over the full operating cycle showed that the catalytic combustor system would achieve low emissions from 20 to 100% load.

The use of catalytic combustion on a high efficiency gas turbine engine design was also evaluated. Pressures up to 20 atm and combustor outlet temperatures up to 1500°C (2730°F) were demonstrated with NOx emissions <2.2 ppm and CO and UHC <2 ppm. These results show that catalytic combustion is a viable technology for application to a high pressure, high temperature industrial gas turbine engine design.
The Thermal Stability of Fuels at 480 °C (900 °F): Effect of Test Time, Flow Rate, and Additives
Authors: Edwards Tim , Krieger John
Published: February 2015

The thermal oxidative stability of several aircraft fuels at high temperatures has been evaluated in a flowing test device. The fuels studied include Jet A, JPTS, and JP-7. The tests evaluated solid deposition under various conditions, typically at maximum fuel temperatures of ∼480 °C (900 °F) at a pressure of 69 atm. Under these conditions, the dissolved oxygen in the fuel is completely consumed and the thermal-oxidative reactions are driven to completion. At test times up to 50 hours, both surface and bulk (filter) deposition was usually an approximately linear function of test time, after an initial induction time of low deposition which varied from 0 to ∼20 hours depending upon fuel quality. In tests with flow rates from 12 to 200 mL/min (1–21 lb/hr), the deposition rate (expressed in ppm) was fairly constant. These data give some guidance for extrapolating results from small flow-rate bench-scale tests to higher flow rates more realistic to aircraft fuel systems, for conditions where the oxygen is completely consumed. For conditions where the oxygen is not completely consumed, the relationship between surface and suspended bulk deposits can become quite complex. Two dispersant additives widely examined in the JP-8+100 program were studied, with the additive significantly decreasing the slope of the deposition-vs-time curve (the deposition rate) for Jet A fuels.
An Investigation of the Heat Recovery System in Externally Fired Evaporative Gas Turbines
Authors: Yan Jinyue , Eidensten Lars , Svedberg Gunnar
Published: February 2015

Externally fired gas turbines have the features of using solid fuel and requiring no particulate cleaning up to protect the gas turbine path. The solid fuel can be, for example, coal or biomass. Evaporative gas turbines (e.g., HAT cycle) have the potential to enhance the power output and increase the efficiency without including a bottoming steam turbine. The integration of the two systems, so called externally fired evaporative gas turbine, can offer the features from both of the systems. In the present paper, the modified externally fired evaporative cycle with intercooling and recuperation is proposed and analyzed. The externally fired gas turbine system is divided into three main subsystems: gas turbine subsystem, solid fuel combustion subsystem and heat recovery subsystem. This paper presents an in-depth investigation of the heat recovery subsystem and its impacts on the total system. The effects of intercooler and aftercooler on the whole system have been addressed and discussed. The optimization strategies for multiple interaction variables, such as air temperature after the recuperation, water-to-air ratio and combustion air temperature for the externally fired combustor, have been provided. The optimization results show that the behavior of the heat recovery subsystem greatly affects the cycle efficiency and power output. Using exhaust heat to heat humid air in a recuperator and to preheat combustion air to the biomass combustor are important for improving the externally fired evaporative gas turbine system. With the electrical efficiency as the objective function of the optimization, there exists an optimum water-to-air ratio located at 0.17 to 0.20 for the system studied in this paper.
Computation of Three-Dimensional Viscous Transonic Turbine Stage Flow Including Tip Clearance Effects
Authors: Merz Rüdiger , Krückels Jörg , Mayer Jürgen F. , Stetter Heinz
Published: February 2015

A numerical method to solve the three-dimensional Navier-Stokes equations for the flow in transonic turbine stages with tip gap leakage is presented.

Viscous flow in a transonic turbine stage has been simulated. The high pressure difference at the rotor blade tip results in a supersonic jet. The relative motion of the casing wall is oriented against the tip leakage flow and tends to reduce it. Very large velocity gradients in the tip region pose a challenge for the numerical simulation. Computational results are compared with experimental data obtained in operation. Measurements include data for the tip leakage jet.

The numerical method is based on a conservative finite volume cell–vertex scheme in cylindrical coordinates with central difference approximation and Runge–Kutta time stepping. Convergence is accelerated by use of a multigrid method and implicit residual smoothing with variable coefficients. The Baldwin–Lomax turbulence model is used for closure. The boundary condition treatment at inlet and outlet as well as the coupling of stator and rotor flow is achieved by use of non–reflective boundary conditions. The tip region is discretized by an additional grid within a multi-block approach.
Experimental Flow Field Investigation in a Centrifugal Compressor Vaned Diffuser
Authors: Pinarbasi Ali , Johnson Mark W.
Published: February 2015

The purpose of this study was to improve the understanding of the flow physics in a centrifugal compressor vaned diffuser. A low speed compressor with a 19 bladed backswept impeller and diffuser with 16 wedge vanes was used. The measurements were made at three inter-vane positions and are presented as mean velocity, turbulent kinetic energy and flow angle distributions on eight diffuser cross sectional planes.

The impeller blade wakes mix out rapidly within the vaneless space and more rapidly than in an equivalent vaneless diffuser. Although the flow is highly non uniform in velocity at the impeller exit, there is no evidence in the results of any separation from the diffuser vanes. The results do however suggest that the use of twisted vanes within the diffuser would be beneficial in reducing losses.
Investigations of Shock/Boundary-Layer Interaction in a Highly Loaded Compressor Cascade
Authors: Bell Ralf M. , Fottner Leonhard
Published: February 2015

Experimental investigations of the shock/boundary-layer interaction were carried out in a highly loaded compressor cascade under realistic turbomachinery conditions in order to improve the accuracy of semi-empirical flow and loss prediction methods. Different shock positions and strengths were obtained by variations of inlet flow angle and inlet Mach number. The free stream turbulence intensity, depending on the inlet Mach number, changed between 4% and 8%. The influence of the inlet Reynolds number based on blade chord is also examined for two different values (Re1=450000, 900000). Schlieren pictures of the transonic cascade flow reveal an unsteady flow behavior with different shock configurations, depending on the pre-shock Mach number. Wake distributions and boundary-layer measurements with the Laser two-focus velocimetry show that the increase of total pressure loss with increasing inlet Mach number is mainly due to the shock/boundary-layer interaction. The shock interaction with a laminar/transitional boundary-layer causes a wide streamwise pressure diffusion, clearly shown by profile pressure distributions. This has a strong influence on the flow outside of the boundary-layer presented by a quantitative Schlieren image. The transition process, investigated with the analysis of thin-film signals, is induced by the shock-wave and occurs above a separated-flow region. At the higher Reynolds number a shock-induced transition takes place without separation.
Latest Improvement in Solar Centaur Family of Engines (New First Stage Compressor)
Authors: Saadatmand Mohammad R.
Published: February 2015

Both the Solar Centaur 40 and Centaur 50 were uprated in mid 1992. The uprate was the result of a redesign of the compressor first stage which increased both mass flow and efficiency. The redesigned compressor underwent rig tests, which included the provision of stator leading-edge mounted instrumentation and overall compressor mapping. The results were close to the design intent/predictions. The predicted engine performance improvements were also confirmed by a series of engine back-to-back tests. Variable vane optimization was performed on the engine using Design of Experiments (DOX). DOX are statistical methods for changing process input in a systematic way and analyzing the resulting outputs in order to improve a response to an acceptable or optimum value. A key feature of the new compressor first stage is that it can be easily retrofitted to both the Centaur 40 and Centaur 50 engines. This paper covers the compressor design methodology, compressor rig test data, engine performance validation test and variable vane optimization.
Theoretical Modelling of Relative Wall Motion Effects in Tip Leakage Flow
Authors: Nikolos I. K. , Douvikas D. I. , Papailiou K. D.
Published: February 2015

The influence of relative wall motion in modifying the leakage flow through the tip clearance is investigated. A theoretical model is developed, in order to calculate the mass flow rate through the gap.

The physical mechanism by which relative wall motion affects the leakage flow is analyzed and the differences between the turbine and compressor case are identified. This model, being an extension of an already existing one, not taking into account relative wall motion, is incorporated into the tip clearance calculation procedure, already developed by the authors.

Theoretical results of the complete calculation procedure (secondary flow plus tip clearance model) are compared with experimental data, for the case of compressor and turbine cascades, as well as for the case of a single rotor. Good agreement between theory and experiment is obtained.
Development of an Interactive Electronic Technical Manual
Authors: Masincup William E. , Bryan John S. , Ochs Linda M.
Published: February 2015

For a number of years, the Navy has been pursuing a means of reducing or eliminating the amount of paper carried onboard ship. In particular, technical manuals consume large amounts of storage space. The paper provides a case study of the development of a gas turbine technical manual into an interactive electronic (computerized) format. Some of the difficulties of the development process, enhancements that have been developed, software selection, graphics complexity, and hardware definition. In addition, a detailed description of a final product will be provided.
Rotor Blade-to-Blade Measurements Using Particle Image Velocimetry
Authors: Tisserant Denis , Breugelmans Frans A. E.
Published: February 2015

The study of turbomachinery flow fields requires detailed experimental data. The rotating parts of turbomachines greatly limit the measurement techniques which can be used. Particle Image Velocimetry (PIV) appears to be a suitable tool to investigate the blade-to-blade flow in a rotor.

The facility is a subsonic axial-flow compressor. The experimental apparatus enables the recording of a double exposed photograph in a circumferential plane located at 85 % of the blade height. The illumination plane has an axial direction and is provided by a pulsed Ruby laser. The tracers used are sub-micron glycerine oil droplets. Data are processed by the Young’s fringes method.

Measurements were performed at 3000, 4500 and 6000 RPM with velocities in the range of 30 to 70 m/s. Steady operating conditions are chosen in such a way that the effect of radial velocity on PIV measurements can be neglected.

Experimental problems which are encountered included homogeneous seeding of the flowfield and laser light scattering from blade surfaces. The uncertainty affecting the velocity determination corresponds to 2 % of the measured value.

For a given set of operating conditions, 10 PIV pictures are recorded. The periodic flow field is approximated by averaging point by point the experimental data. Upstream and downstream velocity triangles are confirmed by measurements obtained from pressure probes. PIV measurement results were found to be similar to those of a blade-to-blade potential-flow calculation.
Surface Effects on Deposits From Jet Fuels
Authors: Ervin J. S. , Heneghan S. P. , Martel C. R. , Williams T. F.
Published: February 2015

Flow experiments in a single-pass heat exchanger using JP-8 and certain additives were initiated under controlled conditions to explore the effects of a metal surface on deposition. The experimental apparatus permitted a unique viewing of the time evolution of deposits at different axial locations under conditions of limited oxygen availability somewhat similar to that in jet aircraft. Scanning electron microscopy was used to examine deposit microstructure. In addition, x-ray photoelectron spectroscopy and Auger electron spectroscopy determined the chemical composition of the deposits. Oxygen concentration measurements in the bulk flow were also performed, and the observed transient oxidation behavior was related to measured time-dependent changes in the deposit.

Increasing dissolved oxygen levels and large changes in deposition were characteristic of the induction time. Mechanisms of fouling in the heated and cooled sections were different. Spectroscopic analysis indicated that deposits formed in the heated section had chemical compositions different from those formed in the cooled section. Scanning electron microscopy revealed differences in microstructure between the heated and cooled sections: more uniform deposits formed in the cooled section as a result of once-soluble species becoming insoluble at low temperatures. In addition, the JP-8 additives significantly reduced fouling in the heated section, but their effectiveness in the cooled section, especially after large periods, was unclear.
Variables Affecting NOx Formation in Lean-Premixed Combustion
Authors: Steele R. C. , Jarrett A. C. , Malte P. C. , Tonouchi J. H. , Nicol D. G.
Published: February 2015

The formation of NOx in lean-premixed, high-intensity combustion is examined as a function of several of the relevant variables. The variables are the combustion temperature and pressure, fuel-type, combustion zone residence time, mixture inlet temperature, reactor surface-to-volume ratio, and inlet jet size. The effects of these variables are examined by using jet-stirred reactors and chemical reactor modeling.

The atmospheric pressure experiments have been completed and are fully reported. The results cover the combustion temperature range (measured) of 1500 to 1850K, and include the following four fuels: methane, ethylene, propane, and carbon monoxide/hydrogen mixtures. The reactor residence time is varied from 1.7 to 7.4ms, with most of the work done at 3.5ms. The mixture inlet temperature is taken as 300 and 600K, and two inlet jet sizes are used. Elevated pressure experiments are reported for pressures up to 7.1atm for methane combustion at 4.0ms with a mixture inlet temperature of 300K. Experimental results are compared to chemical reactor modeling. This is accomplished by using a detailed chemical kinetic mechanism in a chemical reactor model, consisting of a perfectly stirred reactor (PSR) followed by a plug flow reactor (PFR). The methane results are also compared to several laboratory-scale and industrial-scale burners operated at simulated gas turbine engine conditions.
Combustor Stability and Emissions Research Using a Well Stirred Reactor
Authors: Zelina J. , Ballal D. R.
Published: February 2015

The design and development of low-emissions, lean premixed aero or industrial gas turbine combustors is very challenging because it entails many compromises. To satisfy the projected CO and NOx emissions regulations without relaxing the conflicting requirements of combustion stability, efficiency, pattern factor, relight (for aero combustor) or off-peak loading (for industrial combustor) capability demands great design ingenuity. The well stirred reactor (WSR) provides a laboratory idealization of an efficient and highly compact advanced combustion system of the future that is capable of yielding global kinetics of value to the combustor designers. In this paper, we have studied the combustion performance and emissions using a toroidal WSR.

It was found that the toroidal WSR was capable of peak loading almost twice as high as that for a spherical WSR and also yielded a better fuel-lean performance. A simple analysis based upon WSR theory provided good predictions of the WSR lean blowout limits. The WSR combustion efficiency was 99 percent over a wide range of mixture ratios and reactor loading. CO emissions reached a minimum at a flame temperature of 1600K and NOx increased rapidly with an increase in flame temperature, moderately with increasing residence time, and peaked at or slightly on the fuel-lean side of the stoichiometric equivalence ratio. Finally, emissions maps of different combustors were plotted and showed that the WSR has the characteristics of an idealized high efficiency, low emissions combustor of the future.