bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of Secondary Flow Losses in Turbine Cascades by Leading Edge Modifications at the Endwall
Authors: Sauer H. , Müller R. , Vogeler K.
Published: August 2014

Experimental results are presented which show the influence on the secondary flow and its losses by a profile modification of the leading edge very close to the endwall. The investigation was carried out with a well-known turbine profile that originally was developed for highly loaded low pressure turbines. The tests were done in a low speed cascade wind tunnel. The geometrical modification was achieved by a local thickness increase; a leading edge endwall bulb. It was expected that this would intensify the suction side branch of the horse-shoe (hs-) vortex with a desirable weakening effect on the passage vortex. The investigated configuration shows a reduction of secondary losses by 2.1% points that represents approximately 50% of these losses compared to the reference profile. Detailed measurements of the total pressure field behind the cascade are presented for both the reference and the modified profile.

The influence of the modified hs-vortex on the overall passage vortex can be clearly seen. The results of a numerical analysis are compared with the experimental findings.

A numerical analysis shows that the important details of the experimental findings can be reproduced. Quantitative values are locally different. The theoretical approach taken cannot yet be used for an exact prediction of the loss reduction. However the analysis of the interaction and the resulting tendencies are considered to be valid. Hence theoretical investigations as a guideline for the design of a leading edge bulb at the endwall are a valuable tool.
Tip Clearance Effects in a Turbine Rotor: Part II — Velocity Field and Flow Physics
Authors: McCarter Andrew A. , Xiao Xinwen , Lakshminarayana Budugar
Published: August 2014

A comprehensive experimental investigation was undertaken to explore the flow field in the tip clearance region of a turbine rotor to understand the physics of tip leakage flow. Specifically the paper looks at its origin, nature, development, interaction with the secondary flow, and its effects on performance. The experimental study was based on data obtained using a rotating five-hole probe, laser doppler velocimeter, high-response pressure probes on the casing, and static pressure taps on the rotor blade surfaces.

The first part of the paper deals with the pressure field and losses. Part II presents and interprets the vorticity, velocity, and turbulence fields at several axial locations. The data provided here indicates that the tip leakage vortex originates in the last half chord. The leakage vortex is confined close to the suction surface corner near the blade tip by the relative motion of the blade and the casing, and by the secondary flow in the tip region. The tip leakage flow clings to the blade suction surface until midchord then lifts off of the suction surface to form a vortex in the last 20% of the blade chord. The relative motion between blades and casing leads to the development of a scraping vortex which, along with the secondary flow, reduces the propagation of the tip leakage flow into the mainflow. The rotational effects and corriolis forces modify the turbulence structure in the tip leakage flow and secondary flow as compared to cascades.
The Influence of the Clearance of Shrouded Rotor Blades on the Development of the Flowfield and Losses in the Subsequent Stator
Authors: Peters Patrick , Breisig Volker , Giboni Andre , Lerner Christian , Pfost Heiner
Published: August 2014

Although turbines are commonly noted for their high efficiency this efficiency can be improved further. The importance of the leakage flow for the losses of turbine stages makes this flow a promising candidate to be examined for loss reduction: first it decreases the workflow through the rotor and second, the suction side incidence of the re-entering leakage flow in the subsequent stator causes additional losses.

As an essential parameter for leakage flow the clearance and its influence on the losses is investigated by experimental and numerical approach as well. The measurements of the experimental part were carried out on a 1.5 stage axial model turbine of an enlarged scale. The rotor of the turbine consists of shrouded blades with two teeth on the shroud. The clearance was varied from s/D = 0.0007 up to 0.004. Linear traverse measurements with a pneumatic 5-hole probe were taken in front of and behind the second stator. The re-entering leakage flow extremely influences the flow properties in radial direction (up to 50% of the span) at the inlet of the following stator. So the flow angle α1 deviates up to 90° of the flow angle in the mid-span, depending on the clearance. Along with mixing losses, this suction side incidence leads to an increase of the losses within the stator. In addition numerical investigations of the flow field were done with the commercial flow solver CFX-TASCflow. The interaction between the leakage flow and the secondary losses of the following stator is shown, and a comparison with available loss correlations is carried out in this paper.
Three-Dimensional Turbulent Flow Field Downstream of a Single-Stage Axial Compressor Rotor
Authors: Ma Hongwei , Jiang Haokang
Published: August 2014

This paper reports an experimental investigation of the three-dimensional turbulent flow downstream of a single-stage axial compressor rotor. The flow fields were measured at two axial locations in the rotor-stator gap at different mass-flow conditions. Both hot-wire probe and fast-response pressure probe were employed to survey the flow structure.

At the design condition, substantial flow blockage, turbulence, loss and aerodynamic noise mainly occur in the tip mid-passage, the rotor wake and at the hub corner of the suction surface. The radial component is the highest of the three turbulence intensities at 15% axial chord downstream of the trailing edge. With the flow downstream, the radial turbulence components decay fast. Interactions of the tip leakage vorticities and the rotor wake are found at 30% axial chord downstream of the trailing edge.

With the mass-flow decrease, the turbulence intensities and shear stresses become stronger, while the radial components increase fast.

The flow separation and tangential migration of the low-energy fluids at the tip corner of the suction surface play an important role in the tip flow field at a low mass-flow condition.
Endwall Flow Development Across a Contra-Rotating Fan Unit
Authors: Kumar S. , Roy Bhaskar
Published: August 2014

An experimental study has been made to understand the development of endwall flow across a low speed twin-rotor contra-rotating fan unit. Fluid mechanic studies of flow field in the tip region of an axial fan and of a contra-rotating unit were carried out. The fluid mechanic parameters, including flow angles, velocities and static and stagnation pressures, were obtained downstream of the rotors and at one axial location upstream of the first fan (inlet). The flow measurements were done up to 50% of the span from the blade tips. The steady state experimental data of an isolated axial fan indicates that the span wise penetration of this zone is dependent on the tip clearance and the blade loading. Similar effects would normally be expected on the contra-rotating rotors. The experimental data of the contra-rotating unit, however, indicate that neither the blade loading nor the tip clearance change (of the rear fan) affect the performance of the contra-rotating stages as significantly. The span wise zone of influence near the endwall and corresponding flow development due to tip clearance and blade loading seems to be reduced by the rear contra-rotating fan.
An Experimental Study of Stall in Four Axial Compressor Stages
Authors: Cyrus Vaclav
Published: August 2014

Fourteen low-speed axial compressor stages have been tested in the SVÚSS and AHT laboratories. In four cases a detailed analysis of stall development was carried out while the stage working point moved from the design condition to the stability limit. In majority of cases the primary flow mechanism for stall was found. In most stages stalled flow arose in the upper half of the rotor blade row, thereby, tip clearance flow contributed to the growth of low-energy fluid near the casing. An alternative flow mechanism occurred only in one stage with very high aerodynamic loading. Near the stability limit, stalled flow appeared in the rotor blade row in the hub corner. The spanwise distribution of the diffusion factor helped us in the description of stalled flow in stage blade rows.

It follows from these experimental results that the conditions in the rotor blade row play the main role in the rotating stall onset. The extent of stall in the inlet guide vanes and stator vanes did not have a large affect on this phenomenon. The extent of stalled flow in stator row near the stability limit changed with the turning of vanes. At higher values of the IGV turning nonsteady flow patterns can appear.

The conditioning of the stage inlet flow field by means of a specially designed grid affects the stall development in the stage and the onset of rotating stall. A higher value of flow turbulence intensity (Tu = 6–7 %) caused the shift of the stage stability limit to lower flow rates. The stage stall margin was not sensitive to peripheral flow non-uniformities.
Effect of Turbulence Modeling on Particle Dispersion and Deposition on Compressor and Turbine Blade Surfaces
Authors: El-Batsh Hesham , Haselbacher Hermann
Published: August 2014

One of the main mechanisms that control particle movement is the turbulent diffusion by which the particles in the turbulent boundary layer migrate to the surface under the influence of random flow fluctuations. Theoretical approaches to particle dispersion use random walk models to represent the effect of turbulent fluctuation velocity on particle movement. As a consequence, the turbulence model has a significant effect on the particle trajectory. Particle sticking probability, on the other hand depends upon the particle impact velocity. Moreover, the wall shear stress that is calculated from the turbulence model is the main cause of particle detachment from the surface.

In this work, the effect of turbulence models on particle dispersion, deposition on turbine blade surfaces and detachment from the surfaces is studied. Two turbulence models have been tested: the Renormalization Group (RNG) k-ε model and the standard k-ε model. The near-wall region is solved by two different models: the standard wall function and the two-layer zonal model.

It is found that the RNG k-ε model with the two-layer zonal near-wall model is the more appropriate turbulence model for particle deposition. It is also concluded that the standard wall function should not be used when solving the flow field near the wall for particle deposition. The reason is that this method does not give the detailed solution of the flow near the wall that is very important for deposition models.
Numerical Performance of Transition Models in Different Turbomachinery Flow Conditions: A Comparative Study
Authors: Hu Jiasen , Fransson Torsten H.
Published: August 2014

A numerical study has been performed to compare the overall performance of three transition models when used with an industrial Navier-Stokes solver. The three models investigated include two experimental correlations and an integrated eN method. Twelve test cases in realistic turbomachinery flow conditions have been calculated. The study reveals that all the three models can work numerically well with an industrial Navier-Stokes code, but the prediction accuracy of the models depends on flow conditions. In general, all the three models perform comparably well to predict the transition in weak or moderate adverse pressure-gradient regions. The two correlations have the merit if the transition starts in strong favorable pressure-gradient region under high Reynolds number condition. But only the eN method works well to predict the transition controlled by strong adverse pressure gradients. The three models also demonstrate different capabilities to model the effects of turbulence intensity and Reynolds number.
The Combined Use of Navier-Stokes Solvers and Optimization Methods for Decelerating Cascade Design
Authors: Manna Marcello , Tuccillo Raffaele
Published: August 2014

The authors present an optimization strategy applied to decelerating cascades, with the combined use of a Navier-Stokes flow solver, correlation functions and a gradient based optimization method. In the initial stages of the searching the configurations proposed by the optimizer are mainly investigated with a semi-empirical analysis tool so to provide the flow solver with an improved initial guess. In the later stages the optimizer directly controls the flow solver. The objective of the optimization is two fold: determining the geometrical characteristics of the cascade yielding the best aerodynamic performances, and defining an appropriate cost function accounting for optimality conditions in a more general sense.

The method is applied to blade profiles of the C4 type, whose geometrical characteristics are determined as a function of a few parameters (typically the camber angle, the maximum thickness to chord ratio, and the chord). By doing so the number of design parameters is substantially reduced, and the validity of the present methodology is correctly demonstrated, without loss of generality, with a limited computational effort.

The examples deal with the design of decelerating cascades realizing considerable flow turning both in subsonic and transonic regimes and demonstrate the potential of the method.
Ceramic/Metal-Shaft/Hub Connection for Applications in Small High Temperature Ceramic Gas Turbine Rotors
Authors: Heinrich Ulf , Pucher Helmut , Schenk Bjoern , Reimers Walter , Schmackers Thomas
Published: August 2014

The paper provides a synopsis of the research activities currently pursued at the Technical University Berlin, Hahn-Meitner-Institut Berlin and Honeywell Engines & Systems with respect to ceramic/metal joining concept for small ceramic high temperature gas turbine rotors. The objective was to design an interference fit type joint that can be cost effectively produced and reliably transmit torque at elevated temperatures (up to 800°C). Experimental and numerical investigations have been carried out to examine two slightly different designs which both utilize the same basic principle of a shrink fit connection that is able to compensate the thermal expansion mismatch between ceramic and metal and therefore is capable of keeping the contact pressure at the ceramic/metal interface nearly constant over a wide operating temperature range. The joints have been tested under torsional load at isothermal conditions in order to determine the static coefficient of friction and the torque carrying capability, as well as to optimize the joint geometry. The stress distribution inside the joint has been determined by FEA and subsequently evaluated by measuring the residual stress state of the joint in the ceramic by neutron diffraction.
Development of a Very Small Aero-Engine
Authors: Gerendás Miklós , Pfister Ralph
Published: August 2014

The presented work is concerned with the development of a very small aero-engine with 100 N thrust. First a commercially available 30 N-model jet engine was studied on a test bench. Based on the measurements, a calculation procedure was built to represent the measurements. Then the calculation was scaled to 100 N thrust. The scaled engine was designed in a 3D-CAD system, in which the stress analysis of selected parts, mainly the turbine wheel were performed. After the engine parts were manufactured and assembled, the new aero-engine was tested on the test bench as comparison with the predicted values.
The Calculation of the Forced Response of Shrouded Blades With Friction Contacts and its Experimental Verification
Authors: Sextro Walter
Published: August 2014

Shrouds with a frictional interface are used to reduce the dynamic stresses in turbine blades. Due to dry friction energy is dissipated, which can be used to decrease vibration amplitudes and, hence, to increase the life time of turbine blades.

The spatial motion of the blades results in a spatial motion of the contact planes. Due to the non-linearity of the problem, the contact planes are discretized. For each contact area, the developed contact model is used to calculate the corresponding tangential and normal contact forces. This contact model includes the roughness of the contact surfaces, the normal pressure distribution due to roughness, the stiffnesses in normal and tangential direction and dry friction. Due to the roughness of the contact planes the normal contact forces and the contact stiffnesses in normal and tangential direction are nonlinear dependent on the relative displacements in the normal direction. This effect is verified by experiments.

An experiment with one shrouded blade and two non-Hertzian contacts is used to verify the developed contact model and the calculation method. The comparison between measured and calculated frequency response functions for bending and torsional vibrations of the blade show a very good agreement.

A bladed disk assembly with shrouds is investigated and optimized with respect to the vibration amplitudes and alternating stresses. Varying the normal contact force best damping effects are obtained. Separation of the contacts leads to an increase of the alternating stresses and, thus, has to be avoided.
Statistics of Responses of a Mistuned and Frictionally Damped Bladed Disk Assembly Subjected to White Noise and Narrow Band Excitations
Authors: Cha D. , Sinha A.
Published: August 2014

In this paper, the effects of friction dampers on the vibration of a mistuned bladed disk assembly are examined for the following types of random excitation: white noise and narrow band. To compute the statistics of nonlinear response, an analytical technique is developed based on the equivalent linearization method. The validity of the analytical technique has been established by comparison with the results from numerical simulations. The relation between the vibration mode of the system and the performance of friction dampers is investigated.
A Prototype for the First Commercial Pressurized Fuel Cell System
Authors: Ali Sy A. , Moritz Robert
Published: August 2014

High temperature fuel cell stacks of commercially significant power (>100 kW) have emerged during the last 10 years. Five US programs, two Molten Carbonate and three Solid Oxide were recently awarded feasibility study funding from US Department of Energy (DOE) to define products which could achieve at least 70% efficiency to electricity.

The Department of Energy believes that these pressurized fuel cell systems will become an important part of the future power generation soruces. In support of these views, Rolls-Royce has joined fuel cell manufacturers to develop pressurized fuel cell plants which can be marketed successfully to end users.

In selecting technology which should be supported, RR-Allison considered the following critical issues: technology with US business focus; technology with potential for near term commercialization; and technology which would lead into second generation fuel cell system development over long term.

The Rolls-Royce plan is to join the DOE initiative through the pressurized Molten Carbonate program which has been funded as “Molten Carbonate Fuel Cell (MCFC) Product Design and Improvement.”

The paper outlines the functional and commercial issues to be evaluated during the proof of concept tests of the first pressurized MCFC power generation package. The key factors to be evaluated during the test program in current order of priority are:

• operational stability

• power output and system availability

• cost reduction potential

• system simplification for commercial power generation application

• enhanced reliability

• power quality

• grid interconnection
Aerodynamic Loss Characteristics of a Turbine Blade With Trailing Edge Coolant Ejection: Part 2 — External Aerodynamics, Total Pressure Losses and Predictions
Authors: Uzol Oğuz , Camcı Cengiz
Published: August 2014

Investigation of the internal fluid mechanic losses for a turbine blade with trailing edge coolant ejection was presented in Uzol, Camci and Glezer (2000). The current study is a detailed experimental investigation of the external subsonic flowfield near the trailing edge and the investigation of the external aerodynamic loss characteristics of the turbine blade with trailing edge coolant ejection system. Particle Image Velocimetry experiments and total pressure surveys in the near wake of the blade are conducted for two different Reynolds Numbers and four different ejection rates. Two different trailing edge configurations with different cut-back lengths are also investigated. Numerical simulations of the flowfield are also performed for qualitative flow visualization purposes. Two dimensional, incompressible and steady solutions of Reynolds Averaged Navier Stokes equations are obtained. A two equation standard k-ε turbulence model coupled with an Algebraic Reynolds Stress Model is used for the simulation of the turbulent flowfield. The results show that the aerodynamic penalty levels in the wake region near the trailing edge are increased due to the mixing of the coolant and main stream flows for 0 to 3% ejection rates. However after a threshold level (5% ejection rate), the ejected coolant flow has enough momentum to fill the wake of the blade which in turn results in a decrease in the aerodynamic penalty levels.
Unsteady Flow and Whirl-Inducing Forces in Axial-Flow Compressors: Part II — Analysis
Authors: Ehrich F. F. , Spakovszky Z. S. , Martinez-Sanchez M. , Song S. J. , Wisler D. C. , Storace A. F. , Shin H.-W. , Beacher B. F.
Published: August 2014

An experimental and theoretical investigation was conducted to evaluate the effects seen in axial-flow compressors when the centerline of the rotor becomes displaced from the centerline of the static structure of the engine, thus creating circumferentially non-uniform, rotor-tip clearances. This displacement produces unsteady flow and creates a system of destabilizing forces, which contribute significantly to rotor whirl instability in turbomachinery. These forces were first identified by Thomas (1958) for turbines and by Alford (1965) for jet engines. In Part I, the results from an experimental investigation of these phenomena were presented.

In this Part II, three analytic models were used to predict both the magnitude and direction of the Thomas/Alford force in its normalized form, known as the β coefficient, and the unsteady effects for the compressors tested in Part I. In addition, the effects of a whirling shaft were simulated to evaluate differences between a rotor with static off-set and an actual whirling eccentric rotor. The models were also used to assess the influence of the non-axisymmetric static pressure distribution on the rotor spool, which was not measured in the experiment. The models evaluated were: (1) the Two-Sector Parallel Compressor (2SPC) model (Ehrich, 1993), (2) the Infinite-Segment-Parallel-Compressor (ISPC) model (Spakovszky, 2000), and (3) the Two-Coupled Actuator Disc (2CAD) model (Song and Cho, 2000). The results of these analyses were found to be in agreement with the experimental data in both sign and trend. Thus, the validated models provide the general means to predict the aerodynamic destabilizing forces for axial flow compressors in turbine engines. These tools have the potential to improve the design of rotordynamically stable turbomachinery.
Influence of High Pressure Water Injection on Sound Emission of Steam Valves
Authors: Bohn Dieter E. , Balkowski Ingo , Nordheim Dierk von , Saß Jochen
Published: August 2014

In addition to the pressure reduction, a temperature reduction is often obtained in steam valves by injection of cooling water. In such cases, water is injected into the high turbulent flow immediately behind the first stage of the valve, where a major part of the whole throttle noise is generated. Additionally, the density of the steam flow is increased behind the first stage. This causes lower velocities and less sound production in the following stages.

These effects of high pressure water injection on noise production of steam valves are experimentally investigated in a real five-stage steam control valve with a steam mass flow of up to 2 kg/s at an inlet temperature of 463 K and a pressure of 900 kPa. The high pressure water injection mass flow behind the first stage is varied between 0 % and 10% of the mean steam flow. In spite of a high pressure ratio of 45 and sonic expansion behind the first stages, a significant noise reduction of up to 8 dB is observed. During the investigations, the geometry of the injection holes and the throttle geometry of the valve are varied systematically to separate the causes for this effect. The results of the experiments lead to new knowledge about the physical phenomena of sound production in steam control valves.
A Real-Time Turbine Engine Facility Model and Simulation for Test Operations Modernization and Integration
Authors: Montgomery Peter A. , Burdette Rick , Krupp Brian
Published: August 2014

Arnold Engineering Development Center (AEDC) is currently improving its test facilities as part of its Test Operations Modernization & Integration Project (TOMIP). The challenge is to apply control system improvements, achieve control room consolidation, and provide operator training for complex test facilities without negatively impacting ongoing test projects. The TOMIP approach has been to target specific subsystems among all the AEDC test cells, rather than focusing on all the subsystems of a specific set of test cells. This makes it possible to minimize downtime and maximize cost savings. For each targeted subsystem, requirements are identified and hardware and software solutions are designed. These solutions are then validated through the use of models and simulations in a development/training area using identical hardware and software. Upon completion of this validation, the hardware is installed in the field and connected to the existing hardware for a complete checkout of the system. This paper discusses the creation of this development area, its communication architecture, and the real-time model and simulation constructed for this project. Furthermore, the checkout procedure followed, and the application of the system to the coding and testing of new programmable logic controllers (PLCs) for the J1 and J2 turbine engine test facilities will be discussed.
Life Assessment of Thermal Barrier Coatings for Gas Turbine Applications
Authors: Annigeri R. , DiMascio P. S. , Orenstein R. M. , Zuiker J. R. , Thompson A. M. , Lorraine P. W. , Dubois M.
Published: August 2014

A typical TBC system consists of a ceramic top coat material, such as 7–8% yttria stabilized zirconia, applied over a metallic bond coat material, such as diffusion aluminide or MCrAIY. The bond coat serves as an oxidation protection layer for the substrate, as well as providing an adherent surface for the ceramic top coat layer. Estimation of coating durability is critical for design of highly reliable TBC coated parts. Laboratory testing and historical engine experience have revealed that TBC can degrade by various mechanisms; such as fatigue, oxidation, erosion, and impact. Mechanism-based life prediction techniques are needed to assess the durability of TBC in a simulated gas turbine service cycle consisting of: start-up to full speed, steady state operation at full load, and shut-down to zero speed. New testing protocols have been developed in order to simulate the TBC loading under these conditions. The lifing methodology has been calibrated using GE Power Systems gas turbine experience. A nondestructive technique was also used for evaluation of pre- and post-tested TBC specimens.
GEOPHILES: GEneration Of Power with HIgh Levels of Environmental Friendliness — A Technology Transfer Project Between Europe and South America
Authors: Barbosa Joao Roberto , Pilidis Pericles
Published: August 2014

This paper outlines the main details of a technology transfer educational project between the EU and South America. It was sponsored by the CEC, The British Council and GUASCOR.

An international network called GEOPHILES was set up to train ten South American individuals selected by the South American partners. The technical subject was power generation with gas fuel from biomass and low calorific value coal.

The objective was to create a team of individuals with experience on a relevant discipline, giving each grantholder a different experience. To achieve this the training took place in several European Universities and a Spanish company. The trainees and their host institutions received state of the art training and material. They were also made aware of the advanced wealth creation capabilities within the European Community.

The European membership of the consortium included three Universities with important industrial and commercial links and an industrial partner. This gave the programme a valuable practical element.

The project was in two phases, firstly the preparation and delivery of the technical material in an intensive two week course. The second phase of the project was the mobility of the grantholders to Europe to carry out a six and a half month project on a subject relevant to the engineering of suitable power systems.

In the short term the benefit to the South American community was a small team of experts with an increased awareness of advanced environment friendly power generation systems. In the long term this may result in valuable business opportunities to European industry.
Integration of the ETF40B Gas Turbine Engine and FADEC System Into the Landing Craft Air Cushion Vehicle
Authors: Harris Howard , Schneider Phil , Richards John , Dvornak Mike
Published: August 2014

The US Navy along with Textron Marine & Land Systems (TM&LS) is qualifying and field testing the ETF40B gas turbine engine along with Full Authority Digital Engine Control (FADEC) system as possible upgrades to the current TF40B engine and analog control system currently installed on the Landing Craft Air Cushion (LCAC). The ETF40B engine and FADEC control system are of interest due to: increased power, proposed increase in Mean Time Between Overhauls (MTBO), and proposed increase in engine reliability.

The primary topics presented in this paper are:

1. The design, development, and qualification of the ETF40B engine and FADEC control system

2. Integration of the ETF40B engine and FADEC into the LCAC

3. Field test data from two LCACs, follow-up testing and implementation
The Application of Pressure- and Temperature-Sensitive Paints to an Advanced Compressor
Authors: Navarra Kelly R. , Rabe Douglas C. , Goss Larry P.
Published: August 2014

An innovative pressure-measurement technique that employs the tools of molecular spectroscopy has been widely investigated by the aerospace community. Measurements are made via oxygen-sensitive molecules attached to the surface of interest as a coating, or paint. The pressure-sensitive-paint (PSP) technique is now commonly used in stationary wind-tunnel tests; this paper presents the use of this technique in advanced turbomachinery applications. New pressure- and temperature-sensitive paints (P/TSPs) have been developed for application to a state-of-the-art transonic compressor where pressures up to 1.4 atm and surface temperatures to 90°C are expected for the suction surface of the first-stage rotor. PSP and TSP data images have been acquired from the suction surface of the first-stage rotor at 85% of the corrected design speed for the compressor near-stall condition. A comparison to over-the-rotor pressure transducer measurements will be presented.
Effect of Stator Design on Stator Boundary Layer Flow in a Highly Loaded Single-Stage Axial-Flow Low-Speed Compressor
Authors: Friedrichs Jens , Baumgarten Sven , Kosyna Günter , Stark Udo
Published: August 2014

The paper describes an experimental investigation of the stator hub and blade flow in two different stators of a highly loaded single-stage axial-flow low-speed compressor. The first stator (A) is a conventional design with blades of rectangular planform. The second stator (K) is an unconventional, more advanced design with blades of a special planform, characterized by an aft-swept leading edge with increasing sweep angle towards hub and casing. The experimental results show that stator K exhibits a much better hub performance than stator A, finally leading to a better overall performance of stage K compared to stage A. The better hub performance of stator K is, primarily, the result of a planform effect of the newly introduced blades with an aft-swept leading edge and the aerodynamics of an aft-swept wing.
Steady State Performance Simulation of Auxiliary Power Unit With Faults for Component Diagnosis
Authors: Davison Craig R. , Birk A. M.
Published: August 2014

A computer model of an auxiliary power unit has been developed. The model determines the steady state operating condition of the engine under user specified ambient conditions and load. Once the healthy baseline condition is determined faults, such as turbine degradation or flow passage blockage, were introduced and the effect on the engine’s operating parameters noted.

Comparing the results to healthy baseline data generates fault signatures and fault maps, that can be used in engine diagnosis. By observing the changes in parameters that can be economically monitored the viability of this simple diagnosis method can be determined.
Aerodynamic Test Results of Controlled Pressure Ratio Engine (COPE) Dual Spool Air Turbine Rotating Rig
Authors: Keith Brian D. , Basu Dipan K. , Stevens Charles
Published: August 2014

The Controlled Pressure Ratio Engine (COPE) is a fourth generation variable cycle engine combining the attributes of a high temperature turbojet (high dry specific thrust and low Max power SFC) with those of a turbofan (low specific thrust and low part power SFC). Variation in turbine flow function is achieved by the Controlled Area Turbine (CAT) Nozzle concept, which utilizes an innovative cam driven scheme to achieve desired flow function changes while minimizing loss in aerodynamic performance. The single stage high pressure turbine is coupled with a two stage vaneless counter-rotating low pressure turbine. The COPE Turbine System Aero/Heat Transfer Design Validation Program, jointly conducted by GE Aircraft Engines and Allison Advanced Development Company under the direction of the Air Force Research Laboratory at Wright-Patterson Air Force Base, has succeeded in demonstrating advanced turbine technologies that will be utilized on the XTE76, XTE77, and Joint Strike Fighter engines. The various phases of this program evaluated variable area nozzle performance, high pressure turbine performance under the influence of varying flow function, and dual spool testing of the vaneless, counter-rotating low pressure turbine. Evaluation of the three phases demonstrated the aerodynamic capability of these turbine technologies, meeting pre-test predictions in overall and component efficiencies.
On the Modeling of Tip Leakage Flow in Axial Turbine Blade Rows
Authors: Willinger Reinhard , Haselbacher Hermann
Published: August 2014

The starting point of this paper is an established turbine tip leakage loss model based on energy considerations. The model requires a discharge coefficient as an empirical input. The discharge coefficient is the ratio of the actual to the theoretical tip gap mass flow rate, The nondimensional parameters influencing the discharge coefficient are determined by a dimensional analysis. These parameters are: gap width to length ratio, end wall speed to gap flow velocity ratio and gap Reynolds number. Ranges for these parameters, valid for typical turbine tip gap situations, are presented. The numerical investigation of the turbulent flow in a plane perpendicular to the blade chord line supplies the discharge coefficient versus the nondimensional gap width. Depending on the gap width to length ratio, various degrees of mixing of the flow downstream of the vena contracta can be detected. Based on these observations, a simple tip gap flow model is presented. The discharge coefficients computed by this model are compared with the numerical results as well as with experimental values from the literature. Finally, the model is used to calculate the discharge coefficients of improved tip gap geometries (squealers, winglets).
Coating Rejuvenation: New Repair Technology for High Pressure Turbine Blades
Authors: Conner Jeffrey A. , Weimer Michael J.
Published: August 2014

With the evolution of advanced directionally solidified and single crystal nickel base superalloy turbine blades, managing life cycle costs of high pressure turbine (HPT) blades has become increasingly more difficult. Today’s advanced high pressure turbine blades in aero and aero-derivative turbines feature thin walls (<.030 inches), complex internal geometries, three dimensional (3D) aerodynamic shapes, multiple protective coatings and complex film cooling schemes. A major contributor to blade life cycle cost is the ability to perform multiple repairs without compromising the integrity of these complex components.

Repair of HPT blades has traditionally fallen into two categories: mini or partial repairs where blade tips are restored and coated, and full repairs where flowpath coatings are removed, blade tips restored and new coating(s) applied to flowpath surfaces. Historically, the number of full repairs allowed ranges from zero to two based on numerous design considerations, one of which is maintaining a minimum wall thickness. Removal of protective coatings during full repair reduces wall thickness which limits the number of times a full repair can be performed. Furthermore, blades that have sufficient design allowance to permit two full repairs typically have very low yields at the second full repair due to thinning of airfoil walls below minimum thickness limits. The life of a given HPT blade is therefore controlled to a large degree by at what shop visit a full repair is performed.

GE Engine Services has developed a new blade repair approach — Coating Rejuvenation — which significantly extends blade life by restoring protective coatings and maintaining wall thickness. Included in the Coating Rejuvenation repair are technologies that allow: removal of physical vapor deposited (PVD) thermal barrier coatings from external surfaces and cooling holes without impacting the bond coat; removal of oxidation and corrosion products from engine exposed coatings without impacting adjacent intact coating; restoration of coating composition to optimize environmental resistance; and upgrade of existing aluminide coatings to platinum aluminide coatings without removal of the existing coating. Combined together, these technologies can be used to support a comprehensive blade repair workscope plan that dramatically increases the life of HPT blades and decreases the life cycle cost for these components. Overviews of these technologies are presented in this paper along with information on how the technology was matured. Due to pending patent applications with the US Patent & Trademark Office as well as pending patent applications in other countries, significant technical detail cannot be presented at this time.
Summary of CGT302 Ceramic Gas Turbine Research and Development Program
Authors: Takehara Isashi , Tatsumi Tetsuo , Ichikawa Yoshihiro
Published: August 2014

The Japanese Ceramic Gas Turbine (CGT) research and development program (FY1988–1998) as a part of the New Sunshine Project funded by the Ministry of International Trade and Industry (MITI) was completed in March 1999. Kawasaki Heavy Industries, Ltd. (KM) participated in this research program from the beginning and developed a twin-shaft CGT with a recuperator, designated as the “CGT302”.

The purposes of this program were: 1) to achieve both a high efficiency and low pollutant emissions level using ceramic components, 2) to prove a multi-fuel capability to be used in co-generation systems, and 3) to demonstrate long-term operation. The targets of this program were: i) to achieve a thermal efficiency of over 42% at a turbine inlet temperature (TIT) of 1350°C, ii) to keep its emissions within the regulated value by the law, and iii) to demonstrate continuous operation for more than a thousand hours at 1200°C TIT.

The CGT302 has successfully attained its targets. In March 1999 the CGT302 recorded 42.1% thermal efficiency, and 31.7 ppm NOx emissions (O2 = 16%) at 1350°C TIT. At this time it had also accumulated over two thousand hours operation at 1200°C.

In this paper, we summarize the development of the CGT302.
Endwall Cavity Flow Effects on Gaspath Aerodynamics in an Axial Flow Turbine: Part I — Experimental and Numerical Investigation
Authors: Hunter Scott D. , Manwaring Steven R.
Published: August 2014

Axial flow turbine designers are currently using Navier-Stokes flow solvers to reveal the details of the three dimensional flowfield inside individual bladerow passages. This new capability has allowed designers to focus on secondary flow reduction to improve turbine efficiency. These steady bladerow solvers include viscous and film cooling effects and show good agreement with test measurements in the midspan region. However, the difference between computational results and data at the endwalls is significant due to the exclusion of endwall cavity effects. A clear understanding of how the flow entering and exiting the cavity interacts with the gaspath aerodynamics, in conjunction with an accurate computational model, are needed to predict accurately the secondary flow patterns and endwall losses. This investigation confirms that endwall cavity flows have a significant influence on gaspath aerodynamics and that they need to be included in bladerow computations for accurate results.

Part I presents the experimental and computational results from an investigation of the endwall cavity and gaspath flow interaction in a low pressure turbine. Detailed test measurements were obtained in a low speed research turbine using state of the art geometry and served as a benchmark for the computational model. Hot wire and total pressure measurements were taken at multiple planes between bladerows to establish the interaction between the hub cavity and gaspath flows. Ethylene tracer gas was also applied to evaluate secondary flow characteristics of the stator and the migration of the cavity flow through the downstream rotor.

Steady and unsteady computational analyses were utilized to model different combinations of the cavity and bladerow geometries. This building block approached allowed for separation of the flow physics involved in the interaction and identified the geometry and flow features that were critical to producing the best agreement with test data.

In Part II, the development of a source term model for a steady bladerow solver that simulates endwall cavity flows in a low pressure turbine is reviewed. The source term model adequately captured endwall cavity effects and accurately predicted secondary flow in the adjacent bladerow. This source term model gives designers the capability to investigate new ideas of reducing secondary flow in a timely manner, leading to improvements in overall turbine efficiency.
Aircraft Propulsion System Accident Causal Analysis
Authors: Jack Todd D. , Ford Carl N. , Nadell Shari-Beth , Crisp Vicki
Published: August 2014

A causal analysis of aviation accidents by engine type is presented. The analysis employs a top-down methodology that performs a detailed analysis of the causes and factors cited in accident reports to develop a “fingerprint” profile for each engine type. This is followed by an in-depth analysis of each fingerprint that produces a sequential breakdown. Analysis results of National Transportation Safety Board (NTSB) accidents, both fatal and non-fatal, that occurred during the time period of 1990–1998 are presented. Each data set is comprised of all accidents that involved aircraft with the following engine types: turbofan, turbojet, turboprop, and turboshaft (includes turbine helicopters). During this time frame there were 1461 accidents involving turbine powered aircraft; 306 of these involved propulsion malfunctions and/ or failures. Analyses are performed to investigate the sequential relationships between propulsion system malfunctions or failures with other causes and factors for each engine type. Other malfunctions or events prominent within each data set are also analyzed. Significant trends are identified. The results from this study can be used to identify areas for future research into intervention, prevention, and mitigation strategies.
Feature scale modeling of pulsed plasma-enhanced chemical vapor deposition
Authors: Kelkar Sanket S. , Wolden Colin A.
Published: August 2014

A two dimensional feature scale model has been developed to predict film profile evolution during pulsed plasma enhanced chemical vapor deposition (PECVD). The model employs a diffusion reaction framework with a spatially variable Knudsen diffusion coefficient to account for molecular transport in evolving feature geometries. The transient model accounts for the alternating atomic layer deposition (ALD) and PECVD growth modes that contribute to deposition. A scaling analysis is used to account for diffusion limitations that affect the ALD component in high aspect ratios due to insufficient precursor exposure. The model predictions have been validated using cross section micrographs of nanostructures produced by pulsed PECVD of aluminum oxide on patterned substrates. The model provides a tool to design the fabrication of nanostructures with digital precision. By varying the relative contributions of the two modes pulsed PECVD provides an opportunity engineer the degree of conformality to produce unique morphologies that are distinct from either steady state vapor deposition processes or conventional ALD.