bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Strength as a Function of Preloading in Dynamic Fatigue Testing of Glass and Ceramics
Authors: Choi Sung R. , Salem Jonathan A. , Gyekenyesi John P.
Published: February 2015

The solution of fatigue strength as a function of preloading in dynamic fatigue testing was obtained analytically and numerically. The effect of preloading on dynamic fatigue strength decreases with increasing fatigue parameter (n), and for n ≥ 20 the effect is negligible up to a preloading of 90 %. The solution was verified by dynamic fatigue experiments conducted with soda-lime glass and alumina specimens in room-temperature distilled water. This result showed that one can apply a preloading corresponding up to 90 % of fatigue strength for most glass and ceramic materials, resulting in a dramatic saving of testing time in dynamic fatigue testing. The key feature that makes this technique feasible is that most of the slow crack growth under dynamic fatigue loading occurs close to failure time where a dynamic fatigue strength is defined.
An Assessment of the Performance of Closed Cycles With and Without Heat Rejection at Cryogenic Temperatures
Authors: Agazzani A. , Massardo A. F. , Korakianitis T.
Published: February 2015

This paper presents optimized cycle performance that can be obtained with systems including a Closed Cycle Gas Turbine (CCGT). The influence of maximum temperature, minimum temperature and recuperator effectiveness on cycle performance is illustrated. Several power-plant arrangements are analyzed and compared based on: thermodynamic performance (thermal efficiency and specific work); enabling technologies (available at present); and developing technologies (available in the near term or future). The work includes the effects of utilization of high temperature ceramic heat exchangers and of coupling of CCGT systems with plants vaporizing Liquid Hydrogen (LH2) or Liquefied Natural Gas (LNG). Given the versatility of energy addition and rejection sources that can be utilized in closed gas-cycle systems, the thermodynamic performance of power plants shown in this paper indicate the remarkable capabilities and possibilities for closed gas-cycle systems.
Structural Design and High Pressure Test of a Ceramic Combustor for 1500°C Class Industrial Gas Turbine
Authors: Yuri I. , Hisamatsu T. , Watanabe K. , Etori Y.
Published: February 2015

A ceramic combustor for a 1500°C, 20MW class industrial gas turbine was developed and tested. This combustor has a hybrid ceramic/metal structure. To improve the durability of the combustor, the ceramic parts were made of silicon carbide (SiC), which has excellent oxidation resistance under high temperature conditions as compared to silicon nitride (Si3N4) although the fracture toughness of SiC is lower than that of Si3N4. Structural improvements to allow the use of materials with low fracture toughness, were made to the fastening structure of the ceramic parts. Also the combustion design of the combustor was improved. Combustor tests using low BTU gaseous fuel of a composition that simulated coal gas were carried out under high pressure. The test results demonstrated that the structural improvements were effective because the ceramic parts exhibited no damage even in the fuel cutoff tests from rated load conditions. It also indicated that the combustion efficiency was almost 100% even under part load conditions.
A Fast-Response Total Temperature Probe for Unsteady Compressible Flows
Authors: Buttsworth D. R. , Jones T. V.
Published: February 2015

A fast-response probe for the measurement of total temperature in unsteady or fluctuating compressible flows is discussed. The operation of the device is based on the measurement of transient heat flux at different probe operating temperatures. The heat flux gauges used in the present investigation were thin film platinum resistance thermometers painted onto the stagnation region of hemispherical fused quartz probes. The quartz probes had a diameter of approximately 3 mm. Uncertainty estimates indicate that temperature measurements with an accuracy of better than ± 3 K are possible. As a demonstration of the accuracy and utility of the device, total temperature and convective heat transfer coefficient measurements were obtained in a number of supersonic nozzle tests, and in a compressible turbulent jet experiment.
A Systematic Computational Methodology Applied to a Three–Dimensional Film–Cooling Flowfield
Authors: Walters Dibbon K. , Leylek James H.
Published: February 2015

Numerical results are presented for a three–dimensional discrete–jet in crossflow problem typical of a realistic film–cooling application in gas turbines. Key aspects of the study include: (1) Application of a systematic computational methodology that stresses accurate computational model of the physical problem, including simultaneous, fully–elliptic solution of the crossflow, film–hole, and plenum regions; high quality 3–D unstructured grid generation techniques which have yet to be documented for this class of problems; the use of a high order discretization scheme to significantly reduce numerical errors; and effective turbulence modelling; (2) A three–way comparison of results to both code validation quality experimental data and a previously documented structured grid simulation; and (3) Identification of sources of discrepancy between predicted and measured results, as well as recommendations to alleviate these discrepancies. Solutions were obtained with a multi–block, unstructured/adaptive grid, fully explicit, time–marching, Reynolds averaged Navier–Stokes code with multi-grid, local time stepping, and residual smoothing type acceleration techniques. The computational methodology was applied to the validation test case of a row of discrete jets on a flat plate with a streamwise injection angle of 35°, and two film–hole length–to–diameter ratios of 3.5 and 1.75. The density ratio for all cases was 2.0, blowing ratio was varied from 0.5 to 2.0, and free–stream turbulence intensity was 2%. The results demonstrate that the prescribed computational methodology yields consistently more accurate solutions for this class of problems than previous attempts published in the open literature. Sources of disagreement between measured and computed results have been identified, and recommendations made for future prediction of this class of problems.
A Three-Dimensional Shock Loss Model Applied to an Aft-Swept, Transonic Compressor Rotor
Authors: Puterbaugh Steven L. , Copenhaver William W. , Hah Chunill , Wennerstrom Arthur J.
Published: February 2015

An analysis of the effectiveness of a three-dimensional shock loss model used in transonic compressor rotor design is presented. The model was used during the design of an aft-swept, transonic compressor rotor. The demonstrated performance of the swept rotor, in combination with numerical results, is used to determine the strengths and weaknesses of the model. The numerical results were obtained from a fully three-dimensional Navier-Stokes solver. The shock loss model was developed to account for the benefit gained with three-dimensional shock sweep. Comparisons with the experimental and numerical results demonstrated that shock loss reductions predicted by the model due to the swept shock induced by the swept leading edge of the rotor were exceeded. However, near the tip the loss model under-predicts the loss because the shock geometry assumed by the model remains swept in this region while the numerical results show a more normal shock orientation.

The design methods and the demonstrated performance of the swept rotor is also presented. Comparisons are made between the design intent and measured performance parameters. The aft-swept rotor was designed using an inviscid axisymmetric streamline curvature design system utilizing arbitrary airfoil blading geometry. The design goal specific flow rate was 214.7 kg/sec/m2 (43.98 lbm/sec/ft2), the design pressure ratio goal was 2.042, and the predicted design point efficiency was 94.0. The rotor tip sped was 457.2 m/sec (1500 ft/sec). The design flow rate was achieved while the pressure ratio fell short by 0.07. Efficiency was 3 points below prediction, though at a very high 91 percent. At this operating condition the stall margin was 11 percent.
CFD-Analysis of Coverplate Receiver Flow
Authors: Popp Oliver , Zimmermann Horst , Kutz J.
Published: February 2015

The flow field in a preswirled cooling air supply to a turbine rotor has been investigated by means of CFD-simulations. Coefficients for system efficiency are derived. The influences of various geometrical parameters for different configurations have been correlated with the help of appropriate coefficients. For some of the most important geometrical parameters of the coverplate receiver design recommendations have been found. For the preswirl nozzles the potential of efficiency improvement by contour design is highlighted.
The Effect of Vortex Shedding on the Unsteady Pressure Distribution Around the Trailing Edge of a Turbine Blade
Authors: Cicatelli G. , Sieverding C. H.
Published: February 2015

The wakes behind turbine blade trailing edge are characterized by large scale periodic vortex patterns known as the von Karman vortex street. The failure of steady-state Navier-Stokes calculations in modeling wake flows appears to be mainly due to ignoring this type of flow instabilities. In an effort to contribute to a better understanding of the time varying wake flow characteristics behind turbine blades, VKI has performed large scale turbine cascade tests to obtain very detailed information about the steady and unsteady pressure distribution around the trailing edge of a nozzle guide vane. Tests are run at an outlet Mach number of M2,is,=0.4 and a Reynolds number of Rec = 2·106. The key to the high spatial resolution of the pressure distribution around the trailing edge is a rotatable trailing edge with an embedded miniature pressure transducer underneath the surface and a pressure slot opening of about 1.5° of the trailing edge circle. Signal processing allowed or differentiation between random and periodic pressure fluctuations. Ultra-short schlieren pictures help in understanding the physics behind the pressure distribution.
Progress on the European Gas Turbine Program: AGATA
Authors: Gabrielsson Rolf , Holmqvist Göran
Published: February 2015

The four-year European Gas Turbine Program “AGATA” was started in Jan 1993 with the objective to develop three critical components aimed at a 60 kW turbogenerator in an hybrid electric vehicle — a catalytic combustor, a radial turbine wheel and a static heat exchanger. The AGATA partners represent car manufacturers as well as companies and research institutes in the turbine, catalyst and ceramic material fields in both France and Sweden.

This paper outlines the main results of the AGATA project for the first three year period. During the third year of the program, the experimental verification of the components has started. A high pressure/temperature test rig for the combustor and the heat exchanger tests has been built and is now being commissioned. A high temperature turbine spin rig will be ready late 1995.

The turbine wheel design is completed and ceramic Si3N4 spin discs have been manufactured by injection moulding and Hot Isostatic Pressing (HIP). A straight blade design has been selected and FEM calculations have indicated that stress levels which occur during a cold start are below 300 MPa.

The catalytic combustor final design for full scale testing has been defined. Due to the high operating temperature, 1350°C, catalyst pilot tests have included ageing, activity and strength tests. Based on these tests, substrate and active materials have been selected. Initial full scale tests including LDV measurements in the premix duct will start late 1995.

The heat exchanger design has also been defined. This is based on a high efficiency plate recuperator design. One critical item is the ceramic thermoplastic extrusion manufacturing method for the extremely thin exchanger plates another is the bonding technique: ceramic to ceramic and ceramic to metal. Significant progress on these two items has been achieved. The manufacturing of quarter scale prototypes is now in process.
An Analysis of Axial Compressors Fouling and a Cleaning Method of Their Blading
Authors: Tarabrin A. P. , Schurovsky V. A. , Bodrov A. I. , Stalder J.-P.
Published: February 2015

The paper describes the phenomenon of axial compressor fouling due to aerosols contained in the air. Key parameters having effect on the level of fouling are determined. A mathematical model of a progressive compressor fouling using the stage-by-stage calculation method is developed. Calculation results on the influence of fouling on the compressor performance are presented. A new index of sensitivity of axial compressors to fouling is suggested. The paper gives information about the Turbotect’s deposit cleaning method of compressor blading and the results of its application on an operating industrial gas turbine. Regular on line and off line washings of compressor flow path make it possible to maintain a high level of engine efficiency and output.
Creep Life of Ceramic Components Using a Finite Element Based Integrated Design Program (CARES/CREEP)
Authors: Powers Lynn M. , Jadaan Osama M. , Gyekenyesi John P.
Published: February 2015

The desirable properties of ceramics at high temperatures have generated interest in their use for structural applications such as in advanced turbine systems. Design lives for such systems can exceed 10,000 hours. The long life requirement necessitates subjecting the components to relatively low stresses. The combination of high temperatures and low stresses typically places failure for monolithic ceramics in the creep regime. The objective of this paper is to present a design methodology for predicting the lifetimes of structural components subjected to creep rupture conditions. This methodology utilizes commercially available finite element packages and takes into account the time varying creep strain distributions (stress relaxation). The creep life of a component is discretized into short time steps, during which, the stress and strain distributions are assumed constant. The damage is calculated for each time step based on a modified Monkman-Grant creep rupture criterion. Failure is assumed to occur when the normalized accumulated damage at any point in the component is greater than or equal to unity. The corresponding time will be the creep rupture life for that component. Examples are chosen to demonstrate the CARES/CREEP (Ceramics Analysis and Reliability Evaluation of Structures/CREEP) integrated design program which is written for the ANSYS finite element package. Depending on the components size and loading conditions, it was found that in real structures one of two competing failure modes (creep or slow crack growth) will dominate. Applications to benchmark problems and engine components are included.
Experience in Full Load Testing Natural Gas Centrifugal Compressors for Rotordynamics Improvements
Authors: Gelin Alain , Pugnet Jean-Marc , Bolusset Daniel , Friez Patrick
Published: February 2015

During full load shop tests under natural gas, two multistage centrifugal compressors exhibited subsynchronous vibrations. Both of them are low flow, high pressure, high rotational speed compressors, and are fitted with tilting pad bearings, and dry gas seals. A rotating stall problem was firstly eliminated by a modification of the diffuser geometry. Then, aerodynamic excitations caused the rotors to operate at their stability limit, and high vibration levels were observed at the first natural frequency. A complete rotordynamics analysis was performed in order to model precisely all the fluid-structure interactions. Modifications of the rotor designs were implemented, consisting in optimizing conveniently the bearing pads, replacing the toothed labyrinth seals of the balance pistons by damping honeycomb seals, fitting them with improved shunt hole systems. In addition, the dry gas seals were found to have been damaged, due to thermal effects, and further modifications were implemented to eliminate this problem. Final full load tests demonstrated a satisfactory behaviour of both centrifugal compressors.
INCONEL Alloy 783: An Oxidation Resistant, Low Expansion Superalloy for Gas Turbine Applications
Authors: Heck K. A. , Smith J. S. , Smith R.
Published: February 2015

INCONEL® alloy 783 is an oxidation resistant low coefficient of thermal expansion (low CTE) superalloy developed for gas turbine applications. Turbine efficiency can be increased through the use of low CTE shrouds and case components that maintain tight blade tip clearances at different turbine operating temperatures. To achieve low CTE, alloys based on Ni-Fe-Co compositions require Cr content be maintained at low levels. Added Cr lowers the Curie temperature and thereby increases thermal expansion rate over a wider temperature range. The necessary lack of Cr minimizes resistance to both general oxidation and stress accelerated grain boundary oxygen enhanced cracking (SAGBO). Increased amounts of Al in alloys strengthened by γ’ alone also promotes SAGBO. Alloy 783 is the culmination in the development of an alloy system with very high aluminum content that, in addition to forming γ′, causes β aluminide phase precipitation in the austenitic matrix. It was discovered that this type of structure can be processed to resist both SAGBO and general oxidation, while providing low thermal expansion and useful mechanical properties up to 700°C. The high Al content also reduces density to 5% below that of superalloys such as INCONEL alloy 718. Key aspects of the alloy development are presented, including the assessment of SAGBO resistance by evaluating elevated temperature crack growth in air. The alloy, now commercially available, has been successfully fabricated and welded into gas turbine engine components.
High Pressure Test Results of a Catalytic Combustor for Gas Turbine
Authors: Fujii T. , Ozawa Y. , Kikumoto S. , Sato M. , Yuasa Y. , Inoue H.
Published: February 2015

Recently, use of gas turbine systems such as combined cycle and cogeneration systems has gradually increased in the world. But even when a clean fuel such as LNG (liquefied natural gas) is used, thermal NOx is generated in the high temperature gas turbine combustion process. The NOx emission from gas turbines is controlled through selective catalytic reduction processes (SCR) in the Japanese electric industry.

If catalytic combustion could be applied to the combustor of the gas turbine, it is expected to lower NOx emission more economically. Under such high temperature and high pressure conditions as in the gas turbine, however, the durability of the catalyst is still insufficient. So it prevents the realization of a high temperature catalytic combustor.

To overcome this difficulty, a catalytic combustor combined with premixed combustion for a 1300°C class gas turbine was developed. In this method, catalyst temperature is kept below 1000°C and a lean premixed gas is injected into the catalytic combustion gas. As a result, the load on the catalyst is reduced and it is possible to prevent the catalyst deactivation.

After a preliminary atmospheric test, the design of the combustor was modified and a high pressure combustion test was conducted. As a result, it was confirmed that NOx emission was below 10ppm (at 16% O2) at a combustor outlet gas temperature of 1300°C and that the combustion efficiency was almost 100%.

This paper presents the design features and test results of the combustor.
Experimental Investigation of the Liquid Fuel Evaporation in a Premix Duct for Lean Premixed and Prevaporized Combustion
Authors: Brandt Michael , Gugel Kay O. , Hassa Christoph
Published: February 2015

Liquid fuel evaporation was investigated in a premix duct, operating at conditions expected for lean premixed and prevaporized combustion. Results from a flat prefilming airblast atomizer are presented. Kerosine Jet A was used in all experiments. Air pressure, air temperature and liquid fuel flow rate were varied separately, their relative influences on atomization, evaporation and fuel dispersion are discussed.

The results show, that at pressures up to 15 bars and temperatures up to 850 K, nearly complete evaporation of the fuel was achieved, without autoignition of the fuel. For the configuration tested, the fuel distributions of the liquid and evaporated fuel sbow very little differences in their dispersion characteristics and were not much affected by a variation of the operating conditions.
Analysis of the Flow in Vaneless Diffusers With Large Width-to-Radius Ratios
Authors: Dou Hua-Shu , Mizuki Shimpei
Published: February 2015

The flow in vaneless diffusers with large width-to-radius ratios is analyzed by using three-dimensional boundary-layer theory. The variations of the wall shear angle in the layer and the separation radius of the turbulent boundary layer versus various parameters are calculated and compared with experimental data. The effect of the separation point on the performance of vaneless diffusers and the mechanism of rotating stall are discussed. It is concluded that when the flow rate becomes very low, the reverse flow zone on the diffuser walls extends toward the entry region of diffusers. When the rotating jet-wake flow with varying total pressure passes through the reverse flow region near the impeller outlet, rotating stall is generated. The influences of the radius ratio on the reverse flow occurrence as well as on the overall performance are also discussed.
Advances in Nonlinear Dynamic Engine Simulation With an Example: Dynamic Performance Behavior of a Gas Turbine With One Reheat Turbine Stage and Two Combustion Chambers
Authors: Schobeiri M. T. , Attia M. S.
Published: February 2015

The paper discusses some recent advances in dynamic engine simulation technology. A brief presentation of the physical background is followed by a detailed description of the turbine component, its modular representation, and its integration into the nonlinear dynamic engine simulation code GETRAN. In order to ensure the capability, accuracy, robustness, and reliability of the turbine module in interaction with GETRAN, comprehensive critical performance assessment and validation tests were performed. Two conceptually different engine configurations were dynamically simulated and their transient behavior was analyzed and compared with each other. As the first example, a full scale dynamic simulation of an advanced high performance single spool single shaft power generation gas turbine engine is presented. The second example includes the full scale dynamic simulation of an advanced power generation gas turbine engine with a reheat turbine stage and two combustion chambers. The comparison of these engines shows clearly the impact of the dynamic operation on the performance of individual gas turbine engines under consideration.
On Calculation and Optimization of Energy Systems
Authors: Ortmann Peter , Gyarmathy George
Published: February 2015

Most modern plants offer a variety of control methods which can be used one-by-one or in combination. For instance, in case of CC plants, control methods can comprise e. g. fuel control, adjustable compressor guide vanes and various feed preheat options. For the actual part-load operation the knowledge of optimum combinations is of great interest.

A computer code based on standard mathematical optimization tools for large non-linear systems of equations has been developed and tested on various gas-turbine and CC power plant configurations. The code can be employed to plants of almost any level of complexity and to any particular plant layout.

The range of control action is always limited by technological constraints imposed by mechanical, thermal, chemical or other limits and prescribed by the equipment manufacturer. The optimization code has been devised to respect an arbitrary number of such conditions as e. g. flue gas temperature, steam turbine moisture, gas turbine exit temperature and the like.

Such limits and operating instructions concerning the observance of certain parameter ranges (e. g. limits prescribed for sake of life-cycle extension) can be introduced into the optimization procedure.
Measurement of Erosion/Corrosion Damage to Gas Turbine Components
Authors: Oakey John E. , Simms Nigel J.
Published: February 2015

Measurement and prediction of damage to gas turbine aerofoils is of interest to both gas turbine plant operators and suppliers. Metrology methods have been developed to produce accurate and statistically significant measurements of the extent of metal damage after a period of plant operation and to give confidence in results obtained, especially from relatively short term tests. These methods of assessing materials/component performance are based on the use of contact metrology prior to exposure and optically guided measurement around precision prepared cross-sections after exposure. These methods can be used to make several hundred measurements of component dimensions after which the statistical analysis of the data can be carried out for assessment of materials performance. Such measurement methods can be applied to other components in power generating systems, eg heat exchangers.
Thermal Stresses in Gas Turbine Exhaust Duct Expansion Joints
Authors: Ninacs Michel D. , Bell Rodney P.
Published: February 2015

This paper discusses the methods used to derive an improved design for gas turbine exhaust duct expansion joints. Typically these joints are subjected to very rapid increase in internal exhaust gas temperatures that result in large temperature differentials within the joint structures. The thermal gradients can cause stress levels in excess of yield and when the turbine is used intermittently, such as peaking power units would be, the net result is crack propagation and gas leakage.
Failure Analysis of a Burner Component
Authors: Saunders Kenneth L. , Copley Brian P.
Published: February 2015

The cogeneration facility of interest contains four identical cogeneration units which produce about one half million Kg per hour of steam for an adjacent refinery and 385 megawatts of electricity. To supplement the production of steam, burners are used to heat the gas turbine exhaust. These burners incorporate shields to deflect exhaust gas flow around the flame base.

In an effort to improve burner emissions of the units, the burner shield design was modified. This alteration resulted in gross deformation of the shields which interfered with combustion. A failure analysis of these components was conducted to ascertain the root cause of the observed behavior. Loads were estimated based upon operational conditions and material properties were obtained from the open literature. An evaluation was conducted to determine the temperature distribution first. This temperature distribution was then coupled with mechanical loading to obtain total operational stress levels. The stress levels at the observed temperatures clearly placed the material in the high strain rate (creep) region. The computed stress distribution confirmed the observed failure configuration.

A new design was proposed to eliminate this failure mechanism. Detailed evaluations revealed that the new design, while a significant improvement, still operated near the creep region for the material.
Modeling Support Effects: Finite Element and Experimental Modal Methods
Authors: Buckles Jonathan R. , Rouch Keith E. , Baker John R.
Published: February 2015

The effects of support/foundation dynamics are often significant in high speed turbomachinery, and can affect the stability and response to unbalance. In some cases additional critical speeds are introduced, related to resonances in the foundation or interaction with rotor resonances of foundation resonances.

This paper reviews several methods for representing these effects, including (1) reduced matrices from finite element substructures (ANSYS, for example), (2) matrices generated from modal data, and (3) direct use of experimental transfer functions. These methods are implemented in a finite element rotor program in a PC-DOS environment.

The application of the methods to two laboratory rotor configurations described and results presented. Situations with a foundation resonance above and near the rotor critical are included. The importance of including coupling effects between supports is shown.
Torque and Power Loss in a Cylindrical Fluid-Lubricated Bearing/Rotor System
Authors: Goldman Paul , Petchenev Alex , Bently Donald E. , Muszynska Agnes
Published: February 2015

The paper contains the study of the lubricant fluid forces applied to the journal in a cylindrical, externally-pressurized bearing. The analytical expressions take into account the appearance of fluid cavitation at high eccentricity level.

The obtained expressions for fluid forces and torque are used for numerical simulation of a simple, one-mode rotor system. The system exhibits typical fluid whirl/whip instability which results in high fluid resistance torque values. The latter is considered as one of the causes of turbomachinery efficiency deterioration due to fluid-induced instabilities.

This paper is a continuation of the study undertaken by Bently et al. (1985), Muszynska (1986), and Petchenev et al. (1995).
Identification of Best Integrated Combined Cycle Cogeneration Plant
Authors: Sarabchi K. , Polley G. T.
Published: February 2015

Combined cycle cogeneration plants offer significant advantages over other cogeneration systems in many medium and large scale industrial applications. This paper presents a new methodology for the identification of the most efficient plant to satisfy given process requirements of heat and power loads and process steam conditions.
RAM - Performance of Modern Gas Turbines
Authors: von Rappard Axel W. , Neuhoff Heinz G. , Della Villa Salvatore A.
Published: February 2015

Power and heat rate, and exhaust gas and noise emissions are commonly used to evaluate the performance of power generation equipment. Recently, reliability, availability and maintainability (RAM) are being widely adopted as more significant evaluation criteria for gas turbine power plants. All the criteria are used to evaluate new equipment and the measurements on previous installations are the basis for expected values. What differentiates RAM from the other three criteria is the duration of the measurements. Collecting and processing of RAM data is different since it needs to be collected during normal operation of the plant and over a long period of time. This means it is a coordinated effort of both partners; the customers and the manufacturers.

This paper provides a summary of results over a period of four years with a review of the data and conclusions concerning the actual operation. It shows that gas turbine plants can be operated with high reliability and availability requirements. Outages can be reduced in both frequency and length, if the service management is based on the shared information of a worldwide RAM field data collection. A coordinated communication line is a prerequisite for sharing this information. The exchange of information is also mandatory if short reaction time for improvements is required. The planning for the implementation of the communication tools is presented in detail in terms of a ‘road map’ of this program.
Study of Three-Dimensional Viscous Flow Field in Axial-Flow Fan
Authors: Su Moming , Gu Chuan-gang , Miao Yong-miao
Published: February 2015

The complex three-dimensional flow field in an axial-flow impeller incorporating high-Reynolds-number k-ε turbulence model is studied in this paper. The fully three-dimensional Reynolds averaged Navier-Stokes equations are solved. A computational procedure has been developed for predicting three-dimensional incompressible separated turbulent flows in the impeller. The SIMPLE-like algorithm is used. Convective terms are approximated with higher-order upstream-weighted approximations and a TVD-type MUSCL scheme. Physical covariant velocity components are selected as dependent solving variables. The non-orthogonal boundary-fitted coordinate system and collocated grid arrangement are also employed. Rhie and Chow’s momentum interpolation method is adopted to eliminate the non-physical pressure and velocity oscillations. Periodic boundary condition and moving wall boundary condition are considered to simulate truthfully the turbulent flow field in impeller.

Two types of axial-flow impellers are computed. The first one is designed by ordinary method and the other is a improved design that has been considered with eliminating flow separation and viscous vortex in the first design. The computed results show that the fully tree-dimensional turbulent flows computation can efficiently predict three-dimensional separated flows and viscous vortex in axial-flow impeller and vaneless clearance. Using the program, a designer can improve passage geometric design to enhance the performance of the fan.
Coating Characterization and Evaluation of Directionally Solidified CM 186 LC® and Single Crystal CMSX-4®
Authors: Korinko Paul S. , Barber Michael J. , Thomas Malcolm
Published: February 2015

Hot corrosion and long-time dynamic oxidation tests were conducted on several alloy (equiaxed MM-0011 and IN738. SX CMSX-4. and DS CM186LC) and coating (Simple aluminide, Pt-aluminide, and NiCoCrAlY) combinations. The coating performance in both hot corrosion and oxidation testing was, in most cases, influenced by the substrate composition. An overlay NiCoCrAlY on either CMSX-4 or CM186LC appeared unaffected visually, but there were indications during metallographic examination that this coating substrate combination was beginning to degrade after a 1000 hour hot corrosion test. The results of the oxidation test indicated that several of the alloy/coating combinations that were superior in the hot corrosion test were inferior in oxidation. After 6000 hours of dynamic oxidation testing at 1038°C (1900°F) two of the alloy/coating combinations had not yet reached negative weight changes. Metallographic results from the oxidation test show a significant reaction layer in the CMSX-4 coated with either simple or modified aluminides or NiCoCrAlY overlay coatings.
Validation of a 4D Finite Volume Method for Blade Flutter
Authors: Groth Pieter , Mårtensson Hans , Eriksson Lars-Erik
Published: February 2015

A finite volume method for blade flutter analyses, using moving grids is presented and partly validated. The method which solves the unsteady three-dimensional Euler equations is formulated in the four-dimensional time-space domain. An algebraic grid generation technique based on transfinite interpolation is used to move and deform the grid to conform to the blade motion. Fluxes are calculated using a third-order upwind-biased scheme. For time marching both an explicit three-stage Runge-Kutta scheme and a Crank-Nicolson scheme is used. Internal and external flows are calculated using the present method. Calculated results agree well with the corresponding experiments and with results obtained using other methods.
Use of a Thermographic Phosphor Fluorescence Imaging System for Simultaneous Measurement of Film Cooling Effectiveness and Heat Transfer Coefficient
Authors: Chyu M. K. , Hsing Y. C.
Published: February 2015

This paper describes a novel approach based on the temperature-sensitive fluorescence of a thermographic phosphor (europium-doped lanthanum oxysulfide, La2O2S:Eu+3) that enables the simultaneous determination of both local film effectiveness and local heat transfer on a film-cooled surface. The measurement system is capable of acquiring a series of transient, full-field surface temperature images during a heating process. Using a data reduction procedure designed specifically for three-temperature systems, these temporally resolved temperature maps yield the local film effectiveness and heat transfer coefficient simultaneously. The film cooling test model is a single row of four, 30-degree inclined, discrete holes oo a flat plate. The measuement results exhibit superior spatial resolution with detailed features in good agreement with those using other conventional thermal methods, as well as the liquid crystal imaging technique. One major advantage of this technique is its potential for high temperature and highly unsteady applications.
A Boundary Layer Transition Model
Authors: Johnson Mark W. , Ercan Ali H.
Published: February 2015

A new boundary layer transition model is presented which relates the velocity fluctuations near the wall to the formation of turbulent spots. A relationship for the near wall velocity frequency spectra is also established, which indicates an increasing bias towards low frequencies as the skin friction coefficient for the boundary layer decreases. This result suggests that the dependence of transition on the turbulent length scale is greatest at low freestream turbulence levels. This transition model is incorporated in a conventional boundary layer integral technique and is used to predict eight of the ERCOFTAC test cases. Three of these test cases are for nominally zero pressure gradient and the remaining five are for a pressure distribution typical of an aft loaded turbine blade. The model is demonstrated to predict the development of the boundary layer through transition reasonably accurately for all the test cases. The sensitivity of start of transition to the turbulent length scale at low freestream turbulence levels is also demonstrated.
Surface Optimisation by Engineering the Stress and Roughness
Authors: O’Hara Peter
Published: February 2015

Performance of turbine components can significantly be affected by surface/subsurface characteristics. Techniques applied today and being developed further entail introducing into a components surface a residual compressive stress of predictable magnitude and depth followed by superfinishing to improve the surface finish.

The effect will be to lower the mean stress which will increase component life and fatigue strength or enable higher loads through present designs; develop a damage tolerant layer capable of withstanding corrosion pitting or strike damage while in service and produce a final roughness capable of improving flow characteristics on turbine blades/buckets.

The processes to achieve the above include Controlled Shot Peening and Superfinishing. In combination, an optimised surface condition will result.
A Low-Leakage Discontinuously-Rotating Regenerator Designed for a Motor-Vehicle Gas Turbine
Authors: Pfahnl Andreas Carl , Wilson David Gordon
Published: February 2015

A novel regenerator sealing concept is reported that can potentially reduce net compressed-air regenerator-seal leakage in gas turbines to unprecedented levels — near 1% of the net flow, greatly increasing the cycle thermal efficiency. The concept involves primarily discontinuously rotating a disk-type regenerator and implementing clamping seals. This work explains the principle of operation with discussions on preliminary-design calculations based on its use in a conceptual automotive gas turbine (Pfahnl and Wilson, 1995). Detailed regenerator-leakage calculations illustrate the drastically improved leakage rates.
Application of Transient and Dynamic Simulations to the U.S. Army T55-L-712 Helicopter Engine
Authors: Savelle S. A. , Garrard G. D.
Published: February 2015

The T55-L-712 turboshaft engine, used in the U.S. Army CH-47D Chinook helicopter, has been simulated using version 3.0 of the Advanced Turbine Engine Simulation Technique (ATEST) and version 1.0 of the Aerodynamic Turbine Engine Code (ATEC). The models simulate transient and dynamic engine operation from idle to maximum power and run on an IBM-compatible personal computer. ATEST is a modular one-dimensional component-level transient turbine engine simulation. The simulation is tailored to a specific engine using engine-specific component maps and an engine-specific supervisory subroutine that defines component interrelationships. ATEC is a one-dimensional, time-dependent, dynamic turbine engine simulation. ATEC simulates the operation of a gas turbine by solving the one-dimensional, time dependent Euler equations with turbomachinery source terms. The simulation uses elemental control volumes at the sub-component level (e.g. compressor stage).

The paper discusses how limited information from a variety of sources was adapted for use in the T55 simulations and how commonality between the models allowed reuse of the same material. The first application of a new turbine engine model, ATEC, to a specific engine is also discussed. Calibration and operational verification of the simulations will be discussed, along with the status of the simulations.
The Key Role of Heat Exchangers in Closed Brayton Cycle Gas Turbine Power Plants
Authors: McDonald Colin F.
Published: February 2015

In the power generation field, simple cycle gas turbines are dominant, with heat exchanged variants only selected based on particular user’s requirements. For the lesser known closed Brayton cycle (CBC) power plant, heat exchangers are mandatory. The following three categories of heat exchangers are addressed in this paper, 1) heat input to the closed cycle from an external source; for example the heat exchanger in a fluidized bed combuster in the case of a fossil-fired plant, or an intermediate heat exchanger (IHX) in the case of an indirect cycle nuclear gas turbine, 2) recuperator in the system to enhance efficiency, and 3) exchangers (i.e., precooler and intercooler) for heat rejection from the system. The influence that these heat exchangers have on the selection of system parameters, and plant performance is discussed. Heat exchanger technology state-of-the-art for CBC systems is highlighted.
Prediction of the Three-Dimensional Reacting Two-Phase Flow Within a Jet-Stabilized Combustor
Authors: Kurreck M. , Willmann M. , Wittig S.
Published: February 2015

Numerical calculations of the two-phase flow in an experimentally well investigated research combustor are presented. The comparison between measurements and calculations demonstrates the possibilities of the state-of-the-art Euler/Lagrange method for calculating two-phase flows, when applied to a complex reacting liquid fueled combustor. The governing equations for gaseous and liquid phase are presented, with special emphasis on the control of the coupling process between the two phases. The employed relaxation method together with a protocol of convergence show a suitable way to achieve a fast and accurate solution for the strongly coupled two-phase flow under investigation.

Furthermore methods are presented to simulate the stochastic behaviour of the atomization process that appears due to the use of an airblast atomizer. In addition to the numerical methods, experimental techniques are presented, which are used to achieve detailed information about droplet starting conditions.
Steady State Response and Stability of Rotating Composite Blades With Frictional Damping
Authors: Shiau T. N. , Rao J. S. , Yu Y. D. , Choi S. T.
Published: February 2015

Friction dampers are widely used to improve the performance of rotating blades. This paper is concerned with the steady stale response and stability analysis of ratating composite plates in the presence of non linear friction damping. Direct Integration Method (DIM) and Harmonic Balance Method (HBM) are used to determine the steady state response due to periodic lateral external forces. In addition, an alternate procedure, Hybrid Method (HM) is proposed for this analysis to substantiate the results from DIM and HBM. The analysis shows that the steady state response is a function of friction damping magnitude as well as its location besides the excitation frequency and the rotational speed. A stability analysis of the composite blades is also made by including periodic in-plane excitation using Floquet-Liapunov theory.
High Speed Rotor Losses in a Radial 8-Pole Magnetic Bearing: Part 2 — Analytical/Empirical Models and Calculations
Authors: Kasarda M. E. F. , Allaire P. E. , Maslen E. H. , Brown G. R. , Gillies G. T.
Published: February 2015

The continual increase in the use nf magnetic bearings in varinus capacities, including high speed aerospace applications such as jet engine prototypes, dictates the need to quantify power losses in this type of bearing. The goal of the present study is to develop and experimentally verify general power loss equations for the high speed operation of magnetic bearings. Experimental data from a large scale test rotor has been presented in Part 1 of this study. Analytical/empirical predictions are presented here for the test bearings, a pair of 8-pole planar radial bearings, for comparison to the experimental results from Part 1. Expressions for the four loss components, eddy current, alternating hysteresis, rotating hysteresis, and windage, are also presented. Analytical/empirical predictions for the test bearings at three different bias flux levels demonstrate good correlation with corresponding experimental data. Throughout mnst of the speed range the dominant loss mechanism appears to be eddy currents.
Structural Integrity of a Gas Turbine Combustion System Subjected to Increased Dynamic Pressure
Authors: Barnes John E.
Published: February 2015

The effect of combustion dynamic pressure oscillations on the structural integrity of the MS 7001F dry low NOX 2 (DLN 2) combustion system has been evaluated using ANSYS [ref. 1] finite element analyses and high cycle fatigue material data. Analytical results were validated with laboratory measurements on the combustion system subjected to combustion dynamic pressure at actual gas turbine temperature and pressure operating conditions. The combustion liner, transition piece, impingement sleeve and supports were proven to have excellent durability when subjected to dynamic loads. No risk of structural failure exists at anticipated dynamic pressures using assumptions shown to be conservative.
Heat Transfer in a Two-Pass Internally Ribbed Turbine Blade Coolant Channel With Cylindrical Vortex Generators
Authors: Hibbs Richard G. , Acharya Sumanta , Chen Yi , Nikitopoulos Dimitris E. , Myrum Tod A.
Published: February 2015

The effect of vortex generators on the mass (heat) transfer from the ribbed passage of a two pass turbine blade coolant channel is investigated with the intent of optimizing the vortex generator geometry so that significant enhancements in mass/heat transfer can be achieved. In the experimental configuration considered, ribs are mounted on two opposite walls: all four walls along each pass are active and have mass transfer from their surfaces but the ribs are non-participating. Mass transfer measurements, in the form of Sherwood number ratios, are made along the centerline and in selected inter-rib modules. Results are presented for Reynolds number in the range of 5,000 to 40,000. pitch to rib height ratios of 10.5 and 21, and vortex generator-rib spacing to rib height ratios of 0.55 and 1.5. Centerline and spanwise averaged Sherwood number ratios are presented along with contours of the Sherwood number ratios. Results indicate that the vortex generators lead to substantial increases in the local mass transfer rates, particularly along the side walls, and modest increases in the average mass transfer rates. The vortex generators have the effect of making the inter-rib profiles along the ribbed walls more uniform. Along the side walls, horseshoe vortices that characterize the vortex generator wake are associated with significant mass transfer enhancements. The wake effects and the levels of enhancement decrease somewhat with increasing Reynolds number and decreasing pitch.