bluuebunny/crossref_metadata_2025 huggingface dataset:
A Family of Designs for Aspirated Compressors
Authors: Kerrebrock Jack L. , Drela Mark , Merchant Ali A. , Schuler Brian J.
Published: December 2014

The performance of compressors can be enhanced by the judicious removal of the viscous boundary layer fluid from the flow path. Removal of the boundary layer fluid just prior to or in a region of rapid pressure rise, either at shock impingement or more generally at the point of rapid pressure rise on the suction surface of the blade, can give significant increases in the diffusion and therefore increase the work done per stage for a given blade speed. It also provides a thermodynamic benefit by removing the high-entropy fluid from the flow path. Design studies have been done using quasi 3-D viscous and 3-D Euler computational tools on a family of fan stages of varying tip speed that lake advantage of such viscous fluid removal. One stage in this family is a low tip speed fan stage designed to produce a pressure ratio of 1.5 at a tip speed of 700 ft/sec. Fan noise reductions resulting from the decrease in tangential Mach number, without sacrificing total pressure ratio, could make this design attractive for the fan of medium-bypass ratio engines. Another stage in the family would produce a total pressure ratio of 2.0 at a tip speed of 1000 ft/sec and could be very attractive as a fan stage on a lower bypass ratio engine or as a first stage of a low speed core compressor. The final stage in the family would achieve a pressure ratio of more than 3.0 at a tip speed of 1500 ft/sec and could be very attractive as a first stage of a core compressor, or as a fan for a military engine. A design for the suction passages to deal with the fluid removal has been completed for an experimental version of the 1.5 pressure ratio design. A tip shroud allows bleeding of the tip surface boundary layer from the rotor, and carries the fluid removed from the blade surfaces through the tip. One of these stages will be tested in the MIT Blowdown Compressor, serving a dual purpose: as a validation of the computational design process and as a test of the concept of aspirated compressors.
Intercooled and Brayton Cycle Gas Turbines for Steam Power Plant Hot Windbox Repowering
Authors: Negri di Montenegro G. , Gambini M. , Peretto A.
Published: December 2014

In the present paper the performance of a hot windbox repowering steam power plant are evaluated.

A methodology has been developed to determine the mass flow rate range of gas turbine exhaust gas injected into a steam generator of an existing steam power plant.

The study allowed to evaluate the performance of the repowered plant for different gas turbine available on the market.

By utilizing the same methodology, this repowering solution was also investigated employing an intercooler gas turbine that, in the state of art, may be realistically proposed.

It resulted that the hot windbox repowering with Brayton cycle gas turbine supplies a considerably higher power output and efficiency than those of the steam power plant before the repowering.

The employing of an intercooled gas turbine provides further improvements of power and efficiency with respect to the repowered plant using the Brayton cycle gas turbine.
Air System Correlations: Part 2 — Rotating Holes and Two Phase Flow
Authors: Zimmermann H. , Kutz J. , Fischer R.
Published: December 2014

Three important subjects of the physics of air systems have been chosen:

Part 1: Labyrinth Seals

Part 2: Rotating Holes and Two Phase Flow

In these fields many new papers are available. Correlations out of the literature for the discharge coefficients of rotating holes which include the most important parameters are compared and discussed. For two phase flow simple correlations for engineering purposes are recommended, especially for vent lines of aero engines. It is concluded that much more effort is required in order to push knowledge beyond the state of current literature which is partly controversial and not comprehensive enough for computerized engineering.
Experimental and Numerical Investigation of Heat Transfer on a Cooled Turbine Vane
Authors: Rubensdörffer Frank G. , Hjalmarsson Christer S.
Published: December 2014

An experimental research program was performed in a pressurized hot component test rig to evaluate surface temperatures, cooling effectiveness and heat transfer coefficients on a convective cooled turbine vane at near engine conditions. The results were obtained in a 40° five-vane sector cascade at exit Reynolds numbers of 0.98*106 and 2.28*106 at a turbulence level of 4 %. The tests were performed both in steady state and in transient modes. The temperature solving part of a cooling design system was used to evaluate the heat transfer coefficients. A two-dimensional boundary layer program and the commercial Navier-Stokes code Rampant were used for obtaining the numerical results. This paper describes the experimental procedure, the evaluation model and method and the comparison of the first experimental results with numerical calculations.
Application of a Partially Premixed Laminar Flamelet Model to a Low Emissions Gas Turbine Combustor
Authors: Held T. J. , Mongia H. C.
Published: December 2014

Computational combustion dynamics simulations have been used widely for the design and analysis of conventional rich dome combustors using a fast chemistry assumed shape PDF approach (Shyy et al. 1986) and/or an eddy-breakup model (Valachovic, 1993, Danis et al., 1996). The application of these tools to ultra-low emissions combustors such as the GE LM6000 DLE has been hampered by the inadequacies of the eddy break-up combustion model. In the present work, a partially-premixed laminar flamelet combustion model, based initially on the model of Müller et al. (1994), is applied to an LM6000 single cup combustor. The basic fluid mechanical code is ACC, using the k-ε turbulence model (Prakash, et al., 1998). Assumed-shape PDF models are used for mixture fraction Z(x), and the scalar field G(x), whose level surfaces G = G0 represent the flame location. The model includes the effects of local strain rate on flame propagation rate and extinction through modification of the turbulent flame speed correlation, which determines the rate of propagation of the scalar field variable G. The effects of variable inlet fuel/air ratio variance (unmixedness) on predicted NOx emissions are included through the moments of a calculated NO source term on the PDF’s of Z, and include the contributions of flame-front production of NO in premixed flames. Comparisons to measured velocity and emissions data are shown.
Power Generation Technological Determinants for Fuel Scenario Outlook
Authors: Luby P. , Susta M. R.
Published: December 2014

Concentration of power market revolutionary changes within the relatively narrow time frame of the last decade will continue for at least another decade.

Too many dynamic factors have been seen in the research & development of new power generation technology as well as commercial realisation.

Too many impulses have been also seen in the independent power market arena. New legislation framework, new financing tools, deregulation, privatisation and liberalisation trends have become typical with many emerging-economy countries but also with countries having highly developed infrastructure supported by stabilised legislation & political system.

Under such circumstances natural gas (NG) has been preferred both by private developers as well as state developers. From the same reason also gas turbines (GT) based technologies have become highly competitive option in the new capacity demand saturation. GT technologies will retain their dominant position also in the future. However, this needn’t inevitably mean that also NG must retain the first choice for the whole period of next generation. NG market may become saturated in middle-range horizon, approximately about 2010–2015. Huge reserves of coal together with appropriate coal-based technologies like IGCC (Integrated Gasification Combined Cycle) or PFBC (Pressurised Fluidised Bed Combustion) will cause subsequent decline from NG towards other fossil fuel commodities. Reasons for such scenario are given in our analysis.
An Evolutionary Approach to the Development of New Advanced Technology Gas Turbines
Authors: McQuiggan G. , Southall L. R.
Published: December 2014

This paper identifies the market drivers that have accelerated advanced engine development for use in combined cycles. It also describes experience to date with one such advanced turbine model and details a proven approach to the design of these advanced machines. Details are given of two new models and how the designs are an evolution from previous engines. However, good design alone is not enough to obtain optimum reliability. The paper will discuss those operating practices and maintenance approaches that are necessary for successful and profitable plant operation.
Investigation of a Rectangular Rich Quench Lean Combustor Sector
Authors: Koopman Johannes W. , Hassa Christoph , Griebel Peter , Theisen Peter
Published: December 2014

The chemically reacting flow in the mixing and secondary zone of the improved RQL combustor sector of the DLR has been numerically investigated. The combustion model is adapted to meet experimental conditions and proves to underpredict temperature fluctuations. The pressure dependence of the NOx emission index for the quench and lean zone of the combustor can be described with an exponential factor of 0.66. Although the level of agreement between measured and calculated results is not consistently good, the code can be used to study the effect of various operating conditions as well as the effect of geometrical changes on the flow and the emissions.
Design and Investigation of Four Low Solidity Vaned Diffusers to Assess the Effect of Solidity and Vane Number
Authors: Engeda Abraham
Published: December 2014

As part of a continued effort to understand the design and performance of Low Solidity Vaned Diffusers (LSVD), four new LSVDs have been designed and tested.

A centrifugal compressor stage usually consists of the inlet, impeller, diffuser and collector systems. Even though the individual components of the compressor are capable of achieving high efficiency, it is the efficiency of the whole stage that is of great importance. The diffuser system of a centrifugal compressor comes basically in two general categories either as vaneless or vaned diffuser (excluding pipe diffusers). Vaned diffusers can further be subdivided into two depending on channel geometry as straight channel or curved channel, or depending on solidity. It is currently believed that the LSVD offers a compromise between a vaned and a vaneless diffuser by possessing the virtues of each.

This paper discusses the design and experimental investigation of the new four LSVDs. The diffusers had a solidity of 0.9, 0.8, 0.7 and 0.6. These newly designed LSVDs are known as LSVD#5 to LSVD#8.
Numerical Modeling of Unsteady Flow Through a Turbomachine Stage
Authors: Issa R. I. , Sadri M. A.
Published: December 2014

A numerical method is presented for the simulation of unsteady flows through turbomachine stages with unequal numbers of rotor and stator blades. The method solves the two-dimensional incompressible, unsteady, ensemble averaged, Navier-Stokes equations together with transport equations for the k–ϵ turbulence model employed to simulate the effects of turbulence. The method employs an implicit pressure-based finite volume discretisation procedure. In order to simulate the flow in the rotor and stator passages simultaneously, a sliding mesh methodology is developed which allows the mesh mapping the rotor domain to move in a sliding action relative to the static mesh which maps the stator passage. Phase-lagged periodic boundary conditions are implemented in the context of the implicit numerical method developed to handle unequal rotor and stator pitches efficiently. The effectiveness and accuracy of the method are assessed against data for a rotor/stator configuration with unequal pitches in adjacent rows of a low speed turbine.
Development of a Low NOx Combustor for 300kW-Class Ceramic Gas Turbine (CGT302)
Authors: Okuto A. , Kimura T. , Takehara I. , Nakashima T. , Ichikawa Y. , Tatsumi T.
Published: December 2014

Research and development project of ceramic gas turbines (CGT) was started in 1988 promoted by the Ministry of International Trade and Industry (MITI) in Japan. The target of the CGT project is development of a 300kW-class ceramic gas turbine with a 42 % thermal efficiency and a turbine inlet temperature (TIT) of 1350°C. Three types of CGT engines are developed in this project. One of the CGT engines, which is called CGT302, is a recuperated two-shaft gas turbine for co-generation use. In this paper, we describe the research and development of a combustor for the CGT302.

The project requires a combustor to exhaust lower pollutant emissions than the Japanese regulation level. In order to reduce NOx emissions and achieve high combustion efficiency, lean premixed combustion technology is adopted.

Combustion rig tests were carried out using this combustor. In these tests we measured the combustor performance such as pollutant emissions, combustion efficiency, combustor inlet/outlet temperature, combustor inlet pressure and pressure loss through combustor. Of course air flow rate and fuel flow rate are controlled and measured, respectively.

The targets for the combustor such as NOx emissions and combustion efficiency were accomplished with sufficient margin in these combustion rig tests. In addition, we report the results of the tests which were carried out to examine effects of inlet air pressure on NOx emissions here.
A Rotor Blade Cooling Improvement for Heavy Duty Gas Turbine Using Steam and Mixed Steam/Air Cooling
Authors: Carnevale Ennio , Facchini Bruno , Ferrara Giovanni , Innocenti Luca
Published: December 2014

This paper proposes a theoretical study of steam cooling application for a typical rotor blade cooling system of heavy duty gas turbine.

The steam cooling introduction is evaluated using open and closed loop configurations; the possible interaction of steam and air cooling is also studied; the simulation is realized with a family of modular codes developed by authors.

The study is conducted with the characteristic cooling parameters (efficiency, effectiveness) analysis and by the evaluation of blade temperature distribution. The results show the possibility of a mass coolant reduction and/or, a maximum cycle temperature increase with the same cooling system used for standard air cooling.

The best results are obtained with an innovative closed-open/steam-air cooling system.
Characteristics of Heat Transfer in Impinging Jets by Control of Vortex Pairing
Authors: Cho H. H. , Lee C. H. , Kim Y. S.
Published: December 2014

The present study is conducted experimentally to obtain heat transfer characteristics on the impingement surface for controlled jets. Counterflowing or coflowing stream around the jet periphery is used to control the jet at the nozzle lip. The characteristics of flow and heat transfer are studied on two different jet nozzle exit flow conditions, including a fully developed turbulent tube flow and an uniform velocity distribution flow. The experiments are carried out for nozzle-to-plate distances of 2 to 8 nozzle diameters, jet Reynolds numbers in the range of 10,000 to 70,000, and main and secondary flow velocity ratios, R = ΔU/2Ū, of 0.45 to 1.86. The secondary counter- and co-flows change the flow instability conditions in the shear layers resulting in changes of heat transfer on the impingement surface. For secondary counterflows, heat transfer on the impingement surface is changed little for the small nozzle-to-plate distance of H/D = 2, but is enhanced on the stagnation region with reduction on the secondary peak region for H/D = 4. Augmentation of heat transfer on the stagnation region increases with increasing jet Reynolds numbers. For secondary coflows, the jet potential core extends far downstream due to inhibited development of the vortices, but the heat transfer is reduced significantly and the secondary peak appears downstream with increasing blowing rates.
Application of Gas Turbines on Floater Vessel for Power Generation Service
Authors: Waldhelm Chris
Published: December 2014

Application of gas turbines for power generation services aboard special classed floater vessels for mobile oil and gas exploration platforms has been demonstrated and certified by classification societies. A floating platform, designed by Kerr McGee UK PLC, in operation in the North Sea on purpose-built vessel, Tentech 850, has incorporated a pair of Mars T-12,000 gas turbine generator sets designed and supplied by Solar Turbines. The system has been registration classed and certified by Det Norske Veritas in mid 1993 for all of the power generating services required for extended oil extraction and pre-production processing, as well as, auxiliary electric power required for operations.

This paper presents the selection and certification process required for this application and an update of the operating experience during the first years of operation.
Aerodynamics of a Transitioning Turbine Stator Over a Range of Reynolds Numbers
Authors: Boyle R. J. , Lucci B. L. , Verhoff V. G. , Camperchioli W. P. , La H.
Published: December 2014

Midspan aerodynamic measurements for a three vane-four passage linear turbine vane cascade are given. The vane axial chord was 4.45cm. Surface pressures and loss coefficients were measured at exit Mach numbers of 0.3, 0.7, and 0.9. Reynolds number was varied by a factor of six at the two highest Mach numbers, and by a factor often at the lowest Mach number. Measurements were made with and without a turbulence grid. Inlet turbulence intensities were less than 1% and greater than 10%. Length scales were also measured. Pressurized air fed the test section, and exited to a low pressure exhaust system. Maximum inlet pressure was two atmospheres. The minimum inlet pressure for an exit Mach number of 0.9 was one-third of an atmosphere, and at a Mach number of 0.3, the minimum pressure was half this value. The purpose of the test was to provide data for verification of turbine vane aerodynamic analyses, especially at low Reynolds numbers. Predictions obtained using a Navier-Stokes analysis with an algebraic turbulence model are also given.
Investigations of Turbulent Flow in a Centrifugal Compressor Vaned Diffuser by 3-Component Laser Velocimetry
Authors: Stahlecker D. , Gyarmathy G.
Published: December 2014

The unsteady 3D impeller exit and vaned diffuser flow of a high-subsonic centrifugal compressor has been investigated with an LDV system. Time-resolved 3D velocity measurements were taken along a streampath at 8 positions from impeller exit downwards through the vaned diffuser and at 18 positions from hub to casing at each station. The compressor was operated at its best point at a rim Mach number of Mu = 0.75.

Time-resolved (phase averaged) angle and velocity profiles are presented for 2 positions along the streampath. The time-averaged velocity, deterministic fluctuation intensity, turbulence intensity, and in-plane Reynolds sheer stress profiles, presented for all stations, show the evolution of flow and permit comparisons to in-house CFD calculations to be made.

The flow leaving the impeller enters the diffuser with an asymmetric and distorted velocity profile. It is shown that the deterministic fluctuations caused by the jet/wake are quickly damped along the streampath. The results illustrate the deceleration of the flow arriving near the hub in the diffuser channel. The deceleration is accompanied by a sharp increase of turbulence. Near the casing, where the approach velocity is low, no deceleration occurs and the Reynolds stresses are high. Turbulence in the in-plane flow can be regarded as isotropic whereas the axial fluctuations clearly show a high amount of anisotropicity.

The narrow diffuser passage required special optical measures for permitting close-to-wall LDV measurements. The experiences are described.
Effect of Upstream Rotor Vortical Disturbances on the Time-Average Performance of Axial Compressor Stators: Part 1 — Framework of Technical Approach and Wake-Stator Blade Interactions
Authors: Valkov T. V. , Tan C. S.
Published: December 2014

In a two-part paper, key computed results from a set of first-of-a-kind numerical simulations on the unsteady interaction of axial compressor stator with upstream rotor wakes and tip leakage vortices are employed to elucidate their impact on the time-average performance of stator. Detailed interrogation of the computed flowfield showed that for both wakes and tip leakage vortices, the impact of these mechanisms can be described on the same physical basis. Specifically there are two generic mechanisms with significant influence on performance: reversible recovery of the energy in the wakes/tip vortices (beneficial) and the associated non-transitional boundary layer response (detrimental). In the presence of flow unsteadiness associated with rotor wakes and tip vortices, the efficiency of the stator under consideration is higher than that obtained using a mixed-out steady flow approximation. The effects of tip vortices and wakes are of comparable importance. The impact of stator interaction with upstream wakes and vortices depends on the following parameters: axial spacing, loading, and the frequency of wake fluctuations in the rotor frame. At reduced spacing, this impact becomes significant. The most important aspect of the tip vortex is the relative velocity defect and the associated relative total pressure defect, which is perceived by the stator in the same manner as a wake. In Part 1, the focus will be on the framework of technical approach, and the interaction of stator with the moving upstream rotor wakes.
Mechanical Property Scatter in CFCCs
Authors: Steen Marc , Filiou Constantina
Published: December 2014

The tensile response of continuous fibre reinforced ceramic matrix composites (CFCCs) is not expected to show the large variation in strength properties commonly observed for monolithic ceramics. Results of recent investigations on a number of 2D reinforced CFCCs have nevertheless revealed a considerable scatter in the initial elastic modulus, in the first matrix cracking stress and in the failure stress. One school of thought considers that the observed variability is caused by experimental factors. Elaborate testing programmes have been set up to clarify the origins of this scatter by investigation of the effects of control mode, loading rate, specimen shape, etc.. Another school explains the scatter by the presence of (axial) residual stresses in the fibres and in the matrix. Although plausible, this hypothesis is difficult to verify because experimental determination of the residual stress state in CFCCs is not straightforward. In addition, with the available methods it is impractical to determine the residual stresses in every test specimen. This approach is indeed required for establishing the relationship between the magnitude of the residual stresses and the experimentally observed scatter.

At IAM a method has been developed and validated which allows to quantify the axial residual stress state in individual CFCC specimens by subjecting them to intermittent unloading-reloading cycles. The method as well as the derived relationship between residual stress state and scatter in mechanical response will be presented.
Numerical Analysis of Turbine Coolant Passage Flows
Authors: Liou Meng-Sing , Singh K. P.
Published: December 2014

We report in this paper a project undertaken at NASA Lewis Research Center with an aim at achieving a timely, reliable, and high-fidelity CFD prediction of aeropropulsion systems. The present paper specifically addresses issues relevant to internal flows in a turbine component. The flows are three dimensional, highly viscous and turbulent and the geometry is complex. We choose to discretize the computation domain with unstructured tetrahedral meshes and approximate the inviscid fluxes with the recent upwind scheme, AUSM+. An implicit discrete system of unknowns is solved by the Gauss-Seidel Jacobi iterative scheme with a coloring strategy to reduce the matrix bandwidth. A one-equation turbulence model is used to represent the Reynolds stresses. To calculate the complex flow in a turbine coolant passage, we first validate the code for unit problems that contain some subset features. The calculations show excellent results for the backward-facing step and the 180-degree-turn duct. Finally we provide a detailed analysis of the flow in the simulated geometry of th turbine coolant passage.
An Iterative CFD and Mechanical Brush Seal Model and Comparison With Experimental Results
Authors: Chen L. H. , Wood P. E. , Jones T. V. , Chew J. W.
Published: December 2014

The position of the bristles within a brush seal is dictated by the pressure distribution within the seal, which is itself influenced by the position of the bristle matrix. In order to predict mass flows, pressure capabilities, bristle displacements, stresses and contact loads at the rotor interface a technique for iterating between a CFD and a mechanical model has been developed. The iterative technique is used to model the behaviour of seals with an initial build clearance, where the application of pressure causes a change in the position of the bristle matrix. Frictional effects between neighbouring bristles and at the backing ring influence the behaviour of the bristles and these are accounted for within the mechanical part of the model. Results are presented and discussed for seals of both initial build clearance and interference. The mathematical predictions for flow, contact loads at the rotor interface and the nature of the bristles displacements are compared with experimental results.
Stability Analysis and Testing of a Train of Centrifugal Compressors for High Pressure Gas Injection
Authors: Memmott Edmund A.
Published: December 2014

This paper describes the rotor dynamic stability analysis and the PTC-10 Class 1 test of a three body centrifugal compressor train for high pressure natural gas injection service. This train had a full load full pressure string test on hydrocarbon gasses to a final discharge pressure of 500 BAR (7250 PSIA). Each compressor is of the back to back configuration, and is equipped with tilting pad seats, damper bearings, and a honeycomb labyrinth at the division wall with shunt holes. The driver is a gas turbine.
Local Measurement of Loss Using Heated Thin Film Sensors
Authors: Davies Mark R. D. , O’Donnell Francis K.
Published: December 2014

A calibration equation is derived linking the non-dimensional entropy generation rate per unit area with the non-dimensional aerodynamic wall shear stress and free stream pressure gradient. It is proposed that the latter quantities, which can be measured from surface gauges, be used to measure the profile entropy generation rate. It is shown that the equation is accurate for a wide range of well-defined laminar profiles. To measure the dimensional entropy generation rate per unit area requires measurement of the thickness of the boundary layer. A general profile equation is given and used to show the range of accuracy of a further simplification to the calibration. For flows with low free stream pressure gradients, the entropy generation rate is very simply related to the wall shear stress, if both are expressed without units. An array of heated thin film sensors is calibrated for the measurement of wall shear stress, thus demonstrating the feasibility of using them to measure profile entropy generation rate.
High Pressure Test Results of a Catalytically Assisted Ceramic Combustor for a Gas Turbine
Authors: Ozawa Yasushl , Tochihara Yoshihisa , Mori Noriyuki , Yuri Isao , Kanazawa Takaaki , Sagimori Katsuhiro
Published: December 2014

A catalytically assisted ceramic combustor for a gas turbine was designed to achieve low NOx emission under 5ppm at a combustor outlet temperature over 1300°C. This combustor is composed of a burner system and a ceramic liner behind the burner system. The burner system consists of 6 catalytic combustor segments and 6 premixing nozzles, which are arranged in parallel and alternately. The ceramic liner is made up of the layer of outer metal wall, ceramic fiber and inner ceramic tiles.

Fuel flow rates for the catalysts and the premixing nozzles are controlled independently. Catalytic combustion temperature is controlled under 1000°C, premixed gas is injected from the premixing nozzles to the catalytic combustion gas and lean premixed combustion over 1300°C is carried out in the ceramic liner. This system was designed to avoid catalytic deactivation at high temperature and thermal and mechanical shock fracture of the honeycomb monolith of the catalyst.

A combustor for a 10MW class, multi-can type gas turbine was tested under high pressure conditions using LNG fuel. Measurements of emission, temperature, etc. were made to evaluate combustor performance under various combustion temperatures and pressures.

This paper presents the design features and the test results of this combustor.
Effect of Reynolds Number on Separation Bubbles on Controlled-Diffusion Compressor Blades in Cascade
Authors: Hobson Garth V. , Hansen Denis J. , Schnorenberg David G. , Grove Darren V.
Published: December 2014

A detailed experimental investigation of second-generation, controlled-diffusion, compressor stator blades at an off-design inlet-flow angle was performed in a low-speed cascade wind tunnel primarily using laser-Doppler velocimetry (LDV). The object of the study was to characterize the off-design flowfield and to obtain LDV measurements of the suction surface boundary layer separation which occurred near mid chord. The effect of Reynolds number on the flow separation in the regime of 210,000 to 640,000 was investigated. Surface flow visualization showed that at the low Re. no. the mid-chord separation bubble started laminar and reattached turbulent within 20% chord on the suction side of the blade. The extent of the bubble compared very well with the measured blade surface pressure distribution which showed a classical plateau and then diffusion in the turbulent region. LDV measurements of the flow reversal in the bubble were performed. At the intermediate Re. no. the boundary layer was transitional before the bubble which had decreased significantly in size (down to 10% chord). At the highest Re. no. the flow was turbulent from close to the leading edge, and three-dimensional flow reversal as a result of endwall effects appeared at approximately 80% chord which did not reattach.
The Effect of Hub Leakage Flow in a Transonic Compressor Stator
Authors: Singh Udai K. , Ginder Robert B.
Published: December 2014

The effect of hub leakage flow on the performance of a transonic fan stator has been investigated numerically using the NEWT unstructured grid Navier-Stokes solver. The experimental configuration which has been modelled has two leakage flow paths: the first being a channel under the stator platform starting in the rotor-stator cavity upstream of the blade leading edge and rejoining the main flow downstream of the blade trailing edge; the second channel is in the form of a small gap between adjacent stator hub platforms, which joins up with the first channel. The experimental results indicate a severe corner separation in the stator hub region. Predictions with no leakage path considerably underestimate this corner separation. When the under-platform channel is modelled the corner stall becomes much worse than measured but it is considerably reduced when the inter-platform gap is included.
A Systematic Experimental Study on the Aerodynamics of Leading Edge Film Cooling on a Large Scale High Pressure Turbine Cascade
Authors: Ardey Sabine , Fottner Leonhard
Published: December 2014

Systematic isothermal investigations on the aerodynamic effects of leading edge film cooling were carried out on a large scale high pressure turbine cascade named AGTB. In the vicinity of the stagnation point the AGTB turbine cascade has one injection site on the suction side and one on the pressure side. Three injection geometries were tested: Slots (two dimensional geometry), streamwise inclined holes (symmetrical three dimensional geometry) and compound angle holes (fully three dimensional geometry). The injection angle in streamwise direction, the blowing ratio, the inlet turbulence intensity, the inlet Mach number, and the inlet Reynolds number were kept constant at values typically found in modern gas turbines.

The measured data comprise the coolant plenum state, the cascade inlet conditions, the flow field in the cascade exit plane including secondary flows, the static pressure distribution in the mid span section of the blade and in the near hole region, the coolant flow field close to the injection site on the leading edge, Schlieren images of the coolant penetration height and oil-and-dye flow visualizations of the blade surface. The experimental data are summarized and documented as a test case that can be used for validation purposes of prediction methods.
Results of the GT Prime Program Improvements to General Electric MS7001B Gas Turbines at the Houston Light and Power T.H. Wharton Site
Authors: Svatek Jerome , Elliott Michael , Crabtree Paul , Jurczynski Gerald E. , Johnston John R. (Bob)
Published: December 2014

At the time of the start of the GT PRIME upgrade project, the eight General Electric MS7001 gas turbines in combined cycle service at the Wharton Station of Houston lighting and Power each had 85,000 hours of operation with 2000 starts. The units were ready for their second major overhaul. A number of hot gas path components required replacement at that time. Rather than replacing components one by one, the user devised a Program for Reliability, Improved Maintenance, and Efficiency (GT PRIME). We will discuss turbine condition, design changes, reduced emissions, and increased output in the paper.

Actual user experience on maintenance and operating costs resulted in some special requirements to be satisfied in addition to the expected parts replacement. General Electric had developed many improved parts for newer units, all of which could be easily applied to older machines. The use of these newer production MS7001EA parts increase component life, parts availability, inspection intervals, system reliability and performance. These will be described in the paper.

These 1972 vintage turbines achieved a 50PPM NOx level by injecting water at a high rate of flow which resulted in the need for more frequent combustion inspection intervals. The development of a dry low NOx system for the unit allowed the combustion inspection interval to double while reducing NOx to 25PPM.

The improvement in component efficiencies in the gas path resulted in increased output and improved the heat rate. These changes had a significant impact on customer operating costs which resulted in a very attractive payback period. We will discuss expected versus actual output, heat rate and emissions results for all eight units. The upgrade of the first unit started in 1992 and the last unit was completed in 1996. A detailed listing of uprate program schedule by unit is listed in Figure #1.
Fast-Track Redeployment of AVON Quad-Pack Improves Island’s Backup Power System
Authors: Blomberg Björn , Liljigren Christer , Jameison Ian
Published: December 2014

Moving power generation equipment is a major undertaking under the best of circumstances. This paper documents the project to provide more reliable backup power for the island of Gotland, off the coast of Sweden in the Baltic Sea. All the power for this scenic island is normally supplied by two sub-sea, HVDC cables from the Swedish mainland. In the early 1990’s, the power company started the planning to redeploy some of their peaking generation assets more effectively on Gotland. Providing the island with more generating capacity and faster recovery in the event of a partial or total loss of the DC tie-line was deemed a worthy endeavor.

Preparations to move the two 60 MW AVON Quad-pack gas turbine-generators were initiated late in 1994. In addition to commencing green-field site construction to receive the units, the company initiated a controls retrofit of the 1970-vintage units with new fault-tolerant combustion and generation automatic voltage regulation control systems to the relocated turbines.

The scope and timeline for this complex, fast-track project are described along with specific challenges. Results versus expectations are also documented.
On-Line and Off-Line Steam Turbine Component Strain States Monitoring for the Diagnostic System
Authors: Kosman Gerard P. , Rusin Andrzej M. , Nowak Grzegorz M.
Published: December 2014

This paper presents the main assumptions and targets of the strain and stress states modelling of the steam turbine components. The analysis is undertaken due to the main components of HP and IP turbine sections (inner and outer casings, valve bodies and rotors) working under a significant load. Stress modelling has been divided into two parts: a simplified analysis and the detailed one. The former has been proposed in this way that the on-line calculations can be done. It’s based on special functions built upon multi-variant heat process simulations. The functions mentioned make it possible to describe the maximum component stress from some measured temperatures. This part should meet the requirements due to the stress state modelling during a usual turbine operation.

The detailed analysis comprises the unsteady operating conditions, bearing the stamp of intensive heating or cooling processes. As a result of the advanced calculation methods and full stress models being used the analyses is carried off-line.
Heat Transfer and Flow Phenomena in a Swirl Chamber Simulating Turbine Blade Internal Cooling
Authors: Hedlund C. R. , Ligrani P. M. , Moon H.-K. , Glezer B.
Published: December 2014

Heat transfer and fluid mechanics results are given for a swirl chamber whose geometry models an internal passage used to cool the leading edge of a turbine blade. The Reynolds numbers investigated, based on inlet duct characteristics, include values which are the same as in the application (18000–19400). The ratio of absolute air temperature between the inlet and wall of the swirl chamber ranges from 0.62 to 0.86 for the heat transfer measurements. Spatial variations of surface Nusselt numbers along swirl chamber surfaces are measured using infrared thermography in conjunction with thermocouples, energy balances, digital image processing, and in situ calibration procedures. The structure and streamwise development of arrays of Görtler vortex pairs, which develop along concave surfaces, are apparent from flow visualizations. Overall swirl chamber structure is also described from time-averaged surveys of the circumferential component of velocity, total pressure, static pressure, and the circumferential component of vorticity. Important variations of surface Nusselt numbers and time-averaged flow characteristics are present due to arrays of Görtler vortex pairs, especially near each of the two inlets, where Nusselt numbers are highest. Nusselt numbers then decrease and become more spatially uniform along the interior surface of the chamber as the flows advect away from each inlet.
A Parametric Starting Study of an Axial-Centrifugal Gas Turbine Engine Using a One-Dimensional Dynamic Engine Model and Comparisons to Experimental Results: Part 1 — Model Development and Facility Description
Authors: Owen A. Karl , Daugherty Anne , Garrard Doug , Reynolds Howard C. , Wright Richard D.
Published: December 2014

A generic one-dimensional gas turbine engine model, developed at the Arnold Engineering Development Center, has been configured to represent the gas generator of a General Electric axial-centrifugal gas turbine engine in the six kg/sec airflow class. The model was calibrated against experimental test results for a variety of initial conditions to insure that the model accurately represented the engine over the range of test conditions of interest. These conditions included both assisted (with a starter motor) and unassisted (altitude windmill) starts. The model was then exercised to study a variety of engine configuration modifications designed to improve its starting characteristics and thus quantify potential starting improvements for the next generation of gas turbine engines. This paper discusses the model development and describes the test facilities used to obtain the calibration data. The test matrix for the ground level testing is also presented. A companion paper presents the model calibration results and the results of the trade-off study.
Update on the Progress of the Brazilian Wood BIG-GT Demonstration Project
Authors: Waldheim L. , Carpentieri E.
Published: December 2014

Biomass integrated gasification-gas turbine (BIG-GT) technology offers the opportunity for efficient and environmentally sound power generation from biomass fuels. Since biomass is ‘carbon-neutral’ it can be used in power generation equipment without contributing to the ‘greenhouse effect’ if it is grown sustainably.

The Brazilian BIG-GT initiative is one of a number of initiatives world-wide aimed at demonstrating, and thereby establishing, biomass as an energy resource for power production. The goal of the Brazilian BIG-GT project is to confirm the commercial viability of producing electricity from wood through the use of biomass-fuelled integrated gasification combined-cycle (BIG-GT) technology. To fulfil this goal a 32 MWe eucalyptus-fuelled demonstration power plant will be built in Brazil on the basis of a design made by TPS Termiska Processer AB (TPS).

The first two phases of the project, which included experimental and engineering studies and the basic engineering of the plant, were completed in 1997. The next phase of the project, the construction and commissioning of the plant, is the recipient of a U.S. $35 million grant from the Global Environmental Facility (GEF) of the United Nations Development Programme (UNDP), in addition to financing from the World Bank (WB).

The plant will be built in Bahia, north-eastern Brazil. The customer of the plant is a consortium, SER - Sistemas de Energia Renovável, comprising of CHESF (Companhia Hidro Elétrica do São Francisco), a federally-owned electricity generation and distribution company, Eletrobras (Centrais Elétricas Brasileiras), a holding company comprising of the main Brazilian companies from the electric generation and distribution sector, and Shell Brasil. Start-up of the plant is scheduled for the year 2000.

The plant will be based on a TPS designed atmospheric-pressure gasification/gas cleaning process. The product gas will be fired in a modified GE LM 2500 gas turbine. The gasification and gas cleaning process is based on the use of a circulating fluidised bed gasifier, secondary stage catalytic tar cracker and conventional cold filter and wet scrubbing technology. The feedstock to the plant will be mainly eucalyptus wood from a dedicated plantation which is harvested on a three-year cycle.

This paper describes the background of the project leading up to the technology selection, the technology that will be employed in the plant and the outline of the economics of this ‘first-of-a-kind’ plant. The progress made in establishing the organisation and the formal framework (e.g. securing the electricity and fuel contracts) are also reported. Future projections of likely technological improvements and cost reductions, and their effect on the overall economics of an ‘Nth’ plant, are presented.
A Metallographic Technique for High Temperature Creep Damage Assessment in Single Crystal Alloys
Authors: Henderson Pamela , Komenda Jacek
Published: December 2014

The use of single crystal (SX) nickel-base superalloys will increase in the future with the introduction of SX blades into large gas turbines for base-load electricity production. Prolonged periods of use at high temperatures may cause creep deformation and the assessment of damage can give large financial savings. A number of techniques can be applied for life assessment, e.g. calculations based on operational data, non-destructive testing or material interrogation, but because of the uncertainties involved the techniques are often used in combination. This paper describes a material interrogation (metallographic) technique for creep strain assessment in SX alloys.

Creep tests have been performed at 950°C on the SX alloy CMSX-4 and quantitative microstructural studies performed on specimens interrupted at various levels of strain. It was found that the strengthening γ′-particles, initially cuboidal in shape, coalesced to form large plates or rafts normal to the applied stress. The γ-matrix phase also formed plates. CMSX-4 contains ∼ 70 vol % γ′-particles and after creep deformation the microstructure turned itself inside out, i.e. the gamma “matrix” became the isolated phase surrounded by the γ′-“particles”. This can cause problems for computerised image analysis, which in this case, were overcome with the choice of a suitable measurement parameter.

The rafts reached their maximum length before 2% strain, but continued to thicken with increasing strain. Although of different dimensions, the aspect ratios (length/thickness ratio) of the gamma-prime rafts and the gamma plates were similar at similar levels of strain, increasing from ∼1 at zero strain to a maximum of ∼3 at about 1–2 % strain.

Analysis of microstructural measurements from rafting studies on SX alloys presented in the literature showed that the aspect ratios of the γ- and γ′-phases were similar and that at a temperature of 950–1000°C a maximum length/thickness ratio of about 2.5–3.5 is reached at 1 to 2% creep strain. Measurement of gamma-prime raft or (or gamma plate) dimensions on longitudinal sections of blades is thus a suitable method for high temperature creep damage assessment of SX alloys. This gives a considerable advantage over conventional Ni-base superalloys whose microstructures are usually very stable with respect to increasing creep strain.
A Government / Industry Collaboration for Turbine Engine Instrumentation Development
Authors: Anderson Robert C. , Atkinson William , Bonsett Tom , Osani Joe
Published: December 2014

The Propulsion Instrumentation Working Group (PIWG) was formed to cooperatively address critical propulsion engine development test instrumentation and sensor issues. Members of PIWG include the Air Force Arnold Engineering and Development Center, Air Force Wright Laboratory, AlliedSignal Engines, Allison Engine Company, General Electric Aircraft Engines, NASA Lewis Research Center, and Pratt & Whitney with the Ohio Aerospace Institute serving as the administrator to the working group. This paper describes the benefits of this cooperative effort, defines the mission statement, and describes instrumentation and sensor issues currently being addressed.