bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
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.
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.