bluuebunny/crossref_metadata_2025 huggingface dataset:
Distorted Flow Field in Compressor Inlet Channels
Authors: Bry P. , Laval P. , Billet G.
Published: October 2009

Solving the complex inlet-distortion related problems in turbojets or turbofans has become crucial to the successful development of new-generation engines. In order to curtail costs, reliable prediction methods, both analytical and numerical, must be developed and implemented. ONERA has been studying this problem for several years now. This paper reports on the preliminary numerical investigations of the three-dimensional flow field in the annular duct extending in front of a compressor with distorted inflow. The computational approach is a fully unsteady time-splitting, finite difference method solving the inviscid flow equations with nonuniform steady boundary conditions. Some analytical examples are presented and discussed. Matching of this three-dimensional computer code with models representing rotating or fixed blade rows is under way and will be reported on in a future contribution.
Unsteady Aerodynamic and Heat Transfer Processes in a Transonic Turbine Stage
Authors: Ashworth D. A. , LaGraff J. E. , Schultz D. L. , Grindrod K. J.
Published: October 2009

The effect of the interaction of the wake from a nozzle guide vane with the rotor may be simulated in part by means of a stationary rotor and a moving wake system. This technique is applied to a transonic rotor blade cascade, and the unsteady measurements of surface pressure and heat transfer rate are compared with baseline data obtained without the wake interaction. The wake-rotor interaction results in a change in inlet incidence angle and this effect is also examined in the steady-state case. It is found that the shock waves from the moving wake system have a major effect on the instantaneous heat transfer rates.
Derivative Engines Versus New Engines: What Determines the Choice?
Authors: Dix D. M. , Gissendanner D. A.
Published: October 2009

A choice between a derivative engine or a new engine for either an existing aircraft or a new aircraft is becoming an increasingly frequent one. Although some factors which govern such a choice are necessarily subjective, there are several objective factors which should be considered. Using summaries of recent or current cases as examples, an examination of the many dimensions of capability, cost, and risk identifies twelve of these objective factors, many of which are often not subjected to rational analysis.
Integrated Flight/Propulsion Control System Considerations for Future Aircraft Application
Authors: Vizzini R. W.
Published: October 2009

Flight and propulsion controls can effectively be integrated to provide operational benefits to the weapon system which cannot be achieved with either system acting independently. The key factor is the synergistic effect of digital computers and associated high-speed data links, engine condition monitoring, diagnostics, and shared power systems (hydraulic and electrical), thus providing potential improvements in reliability, life cycle cost, weight, and maintenance actions. This technical paper will address the integration concepts required for the airframe and the propulsion control configurations (for consideration in the design stages) to achieve the optimum weapon system configuration by assessing fiber optic and hardwired systems for future applications.
Aircraft Engine Control Mode Analysis
Authors: Brown H. , Elgin J. A.
Published: October 2009

This paper describes the control mode analysis procedure that is used to establish closed-loop control requirements for advanced aircraft propulsion systems. The procedure utilizes anticipated variations in engine component performance, engine deterioration, and control tolerances in a statistical analysis to establish corresponding variations in engine output performance and safety parameters. Potential closed-loop control configurations are evaluated by this process, compared, and the best configuration selected for implementation into control law and schedule designs. A byproduct of the analysis is the establishment of engine design and performance margins. The paper will describe typical engine variational models used in this process, the General Electric COMET program designed to automate the analysis, and typical mode study results based on a current augmented turbofan engine.
Cool Water Coal Gasification—A Progress Report
Authors: Plumley D. R.
Published: October 2009

On May 20, synthetic gas made by gasifying coal was burned in a commercial size gas turbine in Daggett, CA and the electricity produced from that coal flowed into the Southern California Edison system. This event marked the initial operational phase of the Cool Water Coal Gasification Program that expects to demonstrate that the integrated coal gasification combined cycle (IGCC) power plant can burn coal in an environmentally superior manner while also meeting a utility system’s operational and reliability requirements.
Evaluation of Polytropic Calculation Methods for Turbomachinery Performance
Authors: Huntington R. A.
Published: October 2009

Performance calculations for centrifugal compressors have been based on polytropic analysis for many years. The basic polytropic equation, in which head is found from gas pressure, temperature, and compressibility factor at the end points of compression, is applied by virtually all engineers involved with turbomachinery design, selection, or operation. The problems and errors associated with this simple calculation method when applied to nonideal gases have long been recognized. Schultz [1] proposed a correction factor to the head equation to compensate for the errors. This “polytropic head factor” correction is required by the ASME Power Test Code 10 [2] for the evaluation of compressor performance. Recently, the accuracy of even the corrected head equation has been questioned for the compression of gases to high pressures and an alternative calculation method has been proposed by Mallen and Saville [3]. Although differences were found between their method and the Schultz method of up to three percent, they did not show which method was more accurate. This paper evaluates the accuracy of these previous calculation methods and shows that both have errors for some compression calculations. In addition, a new polytropic calculation method is described and is shown to be substantially more accurate than the methods of both [1] and [3], thus allowing more precise evaluations of compressor performance.
A Theoretical Approach to the Combustion of Fuel-Alcohol Blends
Authors: Cau G. , Pelagagge M. P.
Published: October 2009

This paper is concerned with the results of a theoretical investigation on combustion of traditional fuel and alcohol blends. An analytical procedure has been developed which examines three different hypotheses for introducing the alcohol: constant mass of primary fuel, constant total energy of fuel, and constant total mass of fuel. The procedure has been applied to combustion at constant volume varying over a wide range of air-fuel ratios, percentage of alcohol, and combustion temperature. The results obtained, of particular interest for reciprocating internal combustion engines, indicate that as far as energy and emissions are concerned, the effects of alcohol on combustion depend strongly on the hypothesis adopted for fueling the alcohol.
High-Temperature Thermocouple and Heat Flux Gauge Using a Unique Thin Film-Hardware Hot Junction
Authors: Liebert C. H. , Holanda R. , Hippensteele S. A. , Andracchio C. A.
Published: October 2009

A special thin film-hardware material thermocouple (TC) and heat flux gauge concept for a reasonably high-temperature and high heat flux, flat-plate heat transfer experiment was fabricated and tested to gauge temperatures of 911 K. This unique concept was developed for minimal disturbance of boundary layer temperature and flow over the plates and minimal disturbance of heat flux through the plates. Comparison of special heat flux gauge Stanton number output at steady-state conditions with benchmark literature data was good and agreement was within a calculated uncertainty of the measurement system. Also, good agreement of special TC and standard TC outputs was obtained and the results are encouraging. Oxidation of thin film thermoelements was a primary failure mode after about 5 hr of operation.
Performance Evaluation of Linear Turbine Cascades Using Three-Dimensional Viscous Flow Calculations
Authors: Moore J. , Moore J. G.
Published: October 2009

The overall performance of two geometrically similar linear turbine cascades is calculated using an elliptic flow program. The increase in the mass-averaged total pressure loss is calculated within and downstream of the cascades and the results show good agreement with the measured values. The buildup and decay of the secondary kinetic energy are also shown; measurements are available for one of the cascades near and downstream of the trailing edge and these are in close agreement with the calculated values. Details of the flow development are also compared with measurements. Calculated velocity vectors near the endwall show the overturning revealed by surface flow visualization and similarly near the suction surface the strong spanwise flow is well calculated. Calculated contours of total pressure loss in cross-sectional planes confirm the important interaction of the passage vortex with the profile boundary layer at midspan. Regions of high loss near midspan are calculated downstream of both cascades; this three-dimensional flow development is followed in the calculations.
Effects of Tip Endwall Contouring on the Three-Dimensional Flow Field in an Annular Turbine Nozzle Guide Vane: Part 1—Experimental Investigation
Authors: Boletis E.
Published: October 2009

Tip endwall contouring is one of the most effective methods to improve the performance of low aspect ratio turbine vanes [1]. In view of the wide variety of geometric parameters, it appears that only the physical understanding of the three-dimensional flow field will allow us to evaluate the probable benefits of a particular endwall contouring. The paper describes the experimental investigation of the three-dimensional flow through a low-speed, low aspect ratio, high-turning annular turbine nozzle guide vane with meridional tip endwall contouring. The full impact of the effects of tip contouring is evaluated by comparison with the results of a previous study in an annular turbine nozzle guide vane of the same blade and cascade geometry with cylindrical endwalls [12]. In parallel, the present experimental study provides a fully three-dimensional test case for comparison with advanced theoretical calculation methods [15]. The flow is explored by means of double-head, four-hole pressure probes in five axial planes from far upstream to downstream of the blade row. The results are presented in the form of contour plots and spanwise pitch-averaged distributions.
Short-Duration Measurements and Numerical Simulation of Heat Transfer Along the Suction Side of a Film-Cooled Gas Turbine Blade
Authors: Camci C. , Arts T.
Published: October 2009

This paper deals with an experimental investigation of heat transfer across the suction side of a high-pressure, film-cooled gas turbine blade and with an attempt to numerically predict this quantity both with and without film cooling. The measurements were performed in the VKI isentropic compression tube facility under well-simulated gas turbine conditions. Data measured in a stationary frame, with and without film cooling, are presented. The predictions of convective heat transfer, including streamwise curvature effects, are compared with the measurements. A new approach to determine the augmented mixing lengths near the ejection holes on a highly convex wall is discussed and numerical results agree well with experimentally determined heat transfer coefficients in the presence of film cooling.
Simulation of the Effects of Shock Wave Passing on a Turbine Rotor Blade
Authors: Doorly D. J. , Oldfield M. L. G.
Published: October 2009

The unsteady effects of shock waves and wakes shed by the nozzle guide vane row on the flow over a downstream turbine rotor have been simulated in a transient cascade tunnel. At conditions representative of engine flow, both wakes and shock waves are shown to cause transient turbulent patches to develop in an otherwise laminar (suction-surface) boundary layer. The simulation technique employed, coupled with very high-frequency heat transfer and pressure measurements, and flow visualization, allowed the transition initiated by isolated wakes and shock waves to be studied in detail. On the profile tested, the comparatively weak shock waves considered do not produce significant effects by direct shock-boundary layer interaction. Instead, the shock initiates a leading edge separation, which subsequently collapses, leaving a turbulent patch that is convected downstream. Effects of combined wake- and shock wave-passing at high frequency are also reported.
3D Transonic Potential Flow Computation in an Axial-Flow Compressor Rotor by an Approximate Factorization Scheme
Authors: Zhang Jialin
Published: October 2009

A conservative full-potential equation of 3D transonic flow in a turbomachine has been derived with the tensor method and expressed with respect to nonorthogonal curvilinear coordinates, and a fully implicit approximate factorization scheme to calculate the flow field has been developed in this paper. The new algorithm has been used to compute the 3D transonic flow field within an axial-flow single-stage compressor rotor tested by DFVLR. Comparisons between the computed flow field and the DFVLR data have been made. Results demonstrate that fast convergence can be achieved by the presented algorithm and that the agreement with the measurements obtained with an advanced laser velocimeter is quite good.
A Three-Dimensional Axisymmetric Calculation Procedure for Turbulent Flows in a Radial Vaneless Diffuser
Authors: Schumann L. F.
Published: October 2009

An analytical model is proposed to calculate the three-dimensional axisymmetric turbulent flowfield in a radial vaneless diffuser. The model assumes that the radial and tangential boundary layer profiles can be approximated by power-law profiles. Then, using the integrated radial and tangential momentum and continuity equations for the boundary layer and corresponding inviscid equations for the core flow, there result six ordinary differential equations in six unknowns which can easily be solved using a Runge-Kutta technique. A model is also proposed for fully developed flow. The results using this technique have been compared with the results from a three-dimensional viscous, axisymmetric duct code and with experimental data and good quantitative agreement was obtained.
Modeling the 3-D Flow Effects on Deviation Angle for Axial Compressor Middle Stages
Authors: Roberts W. B. , Serovy G. K. , Sandercock D. M.
Published: October 2009

A model of the spanwise variation of the 3-D flow effects on deviation is proposed for middle-stage rotors and stators. This variation is taken as the difference above or below that predicted by blade element theory at any spanwise location. It was found that the stator variation is strongly affected by the end-wall boundary-layer thickness as well as camber, solidity, and blade channel aspect ratio. Rotor variation was found to depend on end-wall boundary layer thickness and tip clearance normalized by blade span. If these parameters are known or can be calculated, the models provide a reasonable approximation to the spanwise variation of deviation for middle compressor stages operating at low to high subsonic inlet Mach numbers.
Computation of Off-Design Flows in a Transonic Compressor Rotor
Authors: Dawes W. N.
Published: October 2009

Recent years have seen increasing efforts to develop efficient solvers for the compressible Navier–Stokes equations. For maximum benefit to be derived from this effort, these Navier–Stokes solvers must be capable of dealing with off-design flows as readily and accurately as the on-design cases. The current paper outlines an efficient implicit algorithm developed recently by the author for solving the compressible Navier–Stokes equations in turbomachinery blade-blade flows. The Navier–Stokes solver is applied to the study of a transonic compressor rotor with supersonic inlet velocities for three cases, one on-design and two off-design. The results are compared with experimental measurements and with the predictions of a viscous-inviscid interactive method.
High Weber Number SMD Correlations for Pressure Atomizers
Authors: Kennedy J. B.
Published: October 2009

Published correlations for the Sauter Mean Diameter (SMD) of sprays produced by pressure atomizing injectors have generally taken the form, SMD = Aω˙B ΔPC. The system of units and the fuel properties are reflected by the coefficient A. The exponent of the flow rate term (B) has been found to be approximately 0.20. There has been less agreement relative to the appropriate value of the pressure drop exponent (C). Simmons [1] reported the value of the pressure drop exponent to be 0.354, and this value has been widely used. This paper presents recently acquired experimental data that reveal that for We greater than 10.0 a different atomization process occurs, i.e., “shear-type” breakup, which results in much finer atomization than predicted by previously reported correlations. To accurately represent the high We data, a significantly different SMD correlation form is required and is reported in this paper. The effects of large variations in the nozzle size, fuel density, viscosity, surface tension, and fuel temperature have been included in the derivation of the correlations.
Spatially Resolved Droplet Size Measurements
Authors: Jackson T. A. , Samuelsen G. S.
Published: October 2009

This paper encompasses initial tests of a droplet sizing technique, providing spatially and temporally resolved measurements within a liquid spray from an air assist nozzle. The method utilizes laser interferometry. The primary size measurement is based upon the signal visibility; it is validated by the peak intensity of the scattered light. As the system is based on the Doppler effect, a single component of velocity is extracted concurrent with the size information. The size of the measurement volume is controlled with off-axis light collection. Beam splitting is accomplished with a rotating diffraction grating, allowing the signal to be frequency shifted. Measurements are compared directly to those of a standard diffraction based sizing system (i.e., Malvern). The diffraction information is processed via Rosin-Rammler (2 parameter) and Model Independent (15 parameter) distribution algorithms. Correspondence between diffraction and interferometric results is satisfactory for the Model Independent algorithm. Differences observed using the Rosin-Rammler distribution are attributed to an inadequate representation of the spray by the two parameter model.
Semiempirical Analysis of Fuel-Air Ratio Distribution Downstream of a Plain Orifice Injector Under Nonuniform Crossflow
Authors: Chin J. S. , Li W. M. , Cao M. H.
Published: October 2009

The present paper is a step further and a modification of the semiempirical analysis of liquid fuel distribution downstream of a plain orifice injector proposed previously [1]. It has been improved from the previous paper in two aspects: (i) the use of experimental data of plain orifice atomization under crossflow obtained by the present authors instead of using Ingebo’s correlation [2], and (ii) consideration taken of the effect of a nonuniform crossflow. The agreement between the calculated results and the experimental data on fuel-air ratio distribution is quite good. In particular the model is capable of predicting the maximum value of the fuel-air ratio distribution and its position. The model has been used for the calculation of fuel-air ratio distribution under nonuniform crossflow with different average flow velocities. Thus the authors are able to predict how the position of maximum fuel-air ratio changes with average velocity for the same profile. The results are in good agreement with the experimental data. From the results of present research the authors conclude that for fuel-air ratio prediction in afterburners or ramjets, it is necessary to consider the effects of nonuniform crossflow. The present semiempirical analysis provides a good design tool for combustor development.
Influence of Downstream Distance on the Spray Characteristics of Pressure-Swirl Atomizers
Authors: Chin J. S. , Nickolaus D. , Lefebvre A. H.
Published: October 2009

An analytical study is made of the factors that are responsible for the observed changes in fuel spray characteristics with axial distance downstream of a pressure-swirl nozzle. To simplify the analysis the effect of fuel evaporation is neglected, but full account is taken of the effects of spray dispersion and drop acceleration (or deceleration). Equations are derived and graphs are presented to illustrate the manner and extent to which the variations of mean drop size and drop-size distribution with axial distance are governed by such factors as ambient air pressure and velocity, fuel injection pressure, initial mean drop size, and initial drop-size distribution.
Annulus Wall Boundary-Layer Measurements in a Four-Stage Compressor
Authors: Cumpsty N. A.
Published: October 2009

There are few available measurements of the boundary layers in multistage compressors when the repeating-stage condition is reached. These tests were performed in a small four-stage compressor; the flow was essentially incompressible and the Reynolds number based on blade chord was about 5 • 104. Two series of tests were performed; in one series the full design number of blades were installed, in the other series half the blades were removed to reduce the solidity and double the staggered spacing. Initially it was wished to examine the hypothesis proposed by Smith [1] that staggered spacing is a particularly important scaling parameter for boundary layer thickness; the results of these tests and those of Hunter and Cumpsty [2] tend to suggest that it is tip clearance which is most potent in determining boundary-layer integral thicknesses. The integral thicknesses agree quite well with those published by Smith.
Unsteady Pressure Measurements on a Biconvex Airfoil in a Transonic Oscillating Cascade
Authors: Shaw L. M. , Boldman D. R. , Buggele A. E. , Buffum D. H.
Published: October 2009

Flush-mounted dynamic pressure transducers were installed on the center airfoil of a transonic oscillating cascade to measure the unsteady aerodynamic response as nine airfoils were simultaneously driven to provide 1.2 deg of pitching motion about the midchord. Initial tests were performed at an incidence angle of 0.0 deg and a Mach number of 0.65 in order to obtain results in a shock-free compressible flow field. Subsequent tests were performed at an angle of attack of 7.0 deg and a Mach number of 0.80 in order to observe the surface pressure response with an oscillating shock near the leading edge of the airfoil. Results are presented for interblade phase angles of 90 and −90 deg and at blade oscillatory frequencies of 200 and 500 Hz (semichord reduced frequencies up to about 0.5 at a Mach number of 0.80). Results from the zero-incidence cascade are compared with a classical unsteady flat-plate analysis. Flow visualization results depicting the shock motion on the airfoils in the high-incidence cascade are discussed. The airfoil pressure data are tabulated.
Aerodynamic Detuning Analysis of an Unstalled Supersonic Turbofan Cascade
Authors: Hoyniak D. , Fleeter S.
Published: October 2009

A new, and as yet unexplored, approach to passive flutter control is aerodynamic detuning, defined as designed passage-to-passage differences in the unsteady aerodynamic flow field of a rotor blade row. Thus, aerodynamic detuning directly affects the fundamental driving mechanism for flutter, i.e., the unsteady aerodynamic forces and moments acting on individual rotor blades. In this paper, a model to demonstrate the enhanced supersonic unstalled aeroelastic stability associated with aerodynamic detuning is developed. The stability of an aerodynamically detuned cascade operating in a supersonic inlet flow field with a subsonic leading edge locus is analyzed, with the aerodynamic detuning accomplished by means of nonuniform circumferential spacing of adjacent rotor blades. The unsteady aerodynamic forces and moments on the blading are defined in terms of influence coefficients in a manner that permits the stability of both a conventional uniformly spaced rotor configuration as well as the detuned nonuniform circumferentially spaced rotor to be determined. With Verdon’s uniformly spaced Cascade B as a baseline, this analysis is then utilized to demonstrate the potential enhanced aeroelastic stability associated with this particular type of aerodynamic detuning.
Behavior of Tip Leakage Flow Behind an Axial Compressor Rotor
Authors: Inoue M. , Kuroumaru M. , Fukuhara M.
Published: October 2009

Performance testing and detailed flow measurements were made in an axial compressor rotor with various tip clearances. The experiments were conducted on the condition of the same incidence angle at midspan. Thus, the effect of tip clearance distinguished from that of incidence angle was investigated on the overall performance, work-done factor, blockage factor, and increases in displacement, momentum, and blade-force-deficit thicknesses of the casing wall boundary layer, The phase-locked flow patterns obtained by the multisampling technique show clear evidence of a leakage vortex core behind the rotor. Behavior of the leakage vortex was clarified for various tip clearances by examining loci of the vortex center, decay characteristics of the vorticity at the center, and the total amount of vorticity shed from the blade tip. These results were compared with the leakage vortex model presented by Lakshminarayana.
A New Theory for Solving Turbulent Vortices in Flowing Fluids
Authors: Gao Ge , Ning Huang
Published: October 2009

Turbulent vortices occur everywhere in flowing fluids and possess the properties of dissipation and dispersion. A set of new control equations is presented featuring the interaction between dissipation and dispersion of turbulence. By analysis of instability the rate of turbulent energy production is established. Two third-order derivative momentum equations are derived, one for weak and the other for strong vorticity. By this new theory various turbulent flow problems can be solved, such as: energy inversion in the vortex tail behind a bluff body, the coherent horseshoe vortices in a turbulent boundary layer, the delay in cascading down of turbulent energy through the spectrum, anisotropy of turbulence intensities, etc. Two computational examples are presented.
An Investigation of a Highly Loaded Transonic Turbine Stage With Compound Leaned Vanes
Authors: Shi Jing , Han Jianyuan , Zhou Shiying , Zhu Mingfu , Zhang Yaoko , She Mengyu
Published: October 2009

An investigation was made to compare the performance of a highly loaded transonic turbine stage with and without compound leaned vanes. In both cases, velocity distribution along the vane surfaces was calculated from a full three-dimensional time-marching finite volume method. Nozzles were tested in a wind tunnel. Through rig tests, velocity profile at the stage exit was measured and the stage overall performance obtained. Performance in both tip and hub regions was improved by using the compound leaned vanes so that the stage efficiency increased by approximately 1 percent. The improvement is particularly remarkable at off-design points.
The Transonic Flow Through a Plane Turbine Cascade as Measured in Four European Wind Tunnels
Authors: Kiock R. , Lehthaus F. , Baines N. C. , Sieverding C. H.
Published: October 2009

Reliable cascade data are esssential to the development of high-speed turbomachinery, but it has long been suspected that the tunnel environment influences the test results. This has now been investigated by testing one plane gas turbine rotor blade section in four European wind tunnels of different test sections and instrumentation. The Reynolds number of the transonic flow tests was Re2 = 8 × 105 based on exit flow conditions. The turbulence was not increased artificially. A comparison of results from blade pressure distributions and wake traverse measurements reveals the order of magnitude of tunnel effects.
A Model for the Prediction of Thermal, Prompt, and Fuel NOx Emissions From Combustion Turbines
Authors: Toof J. L.
Published: October 2009

A model has been developed for the prediction of NOx emissions from combustion turbines. Thermal, prompt, and fuel NO are all treated and are all assumed to be formed at a stoichiometric equivalence ratio. Prompt and fuel NO are assumed to be fast with respect to thermal NO and establish a finite concentration of NO at the beginning of the thermal NO formation process. Thermal NO is calculated via the extended Zeldovich mechanism; a thermal NO formation time is determined from the ratio of flame length to convective velocity within the combustor. Prompt NO is assumed to be formed from the hydrocarbon chemistry and is related to the equilibrium concentration of NO rather than to O-atom overshoot. Fuel NO is calculated assuming an indispensible intermediate in the formation mechanism and a constant Fenimore α parameter for combustion turbine flames. The model employs equilibrium hydrocarbon chemistry; the flame temperature and concentrations of key species are determined in an equilibrium subroutine. The effects of water or steam injection and ambient humidity are included through their impact on the flame temperature and species concentrations. The model has been applied to can-type combustors and its accuracy has been verified by data on high and low nitrogen fuels with and without water injection, and on combustors of different geometry. The treatment of all three mechanisms of NO formation is unique to this model and permits prediction of emissions for the range of conventional and alternative fuels encountered in industrial combustion turbines.
Thermal Mechanical Crack Growth Rate of a High Strength Nickel Base Alloy
Authors: Wilson D. A. , Warren J. R.
Published: October 2009

An understanding of thermal mechanical fatigue (TMF) crack propagation is fundamental to the application of fracture mechanics to gas turbine components. Typical operating conditions for a cooled turbine disk rim consist of a complex mechanical history and an associated variable amplitude thermal history. While thermally induced stress gradients are commonly incorporated in the mechanical history, the effects of thermal cycling on crack growth must be addressed in an appropriate fatigue model. A current computer-based empirical crack propagation modeling system has demonstrated effectiveness under isothermal conditions and can be readily expanded to include thermal-mechanical effects. The existing isothermal models were developed from an extensive data base and describe crack growth over a broad range of temperature and loading conditions. Building on this established system, a model of thermal-mechanical crack growth is being developed.
Weight Functions of Radial Cracks in Hollow Disks
Authors: Sha George T. , Yang Chien-Tung
Published: October 2009

Explicit nodal weight functions for both bore and rim radial cracks in a hollow disk are presented with special emphasis on the load independent characteristics of the weight functions that can eliminate the repeated finite element computations of the Mode I stress intensity factors (KI) for a given crack geometry under different loading conditions. An analytical expression, which relates the explicit crack-face weight functions to the radial distance (rs) from the crack tip along the crack face, is also provided for wide range ratios of crack length (a) to the difference between outer disk radius (Ro) and inner disk radius (Ri) [0.01 ≤ a/(Ro − Ri) ≤ 0.8]. The accurate explicit weight functions of any crack length can be obtained easily with a cubic spline interpolation technique from an adequate set of explicit crack-face weight functions of discrete crack lengths. With the availability of the explicit crack-face weight functions for both the bore and rim cracks, the Mode I stress intensity factors under any complex loading conditions can be calculated accurately and inexpensively by a sum of worklike products between the equivalent “un-cracked” stress field and the interpolated crack-face weight functions. This equivalent uncracked stress field could include the body force loading of a rotating disk, thermal loading, complex residual stresses, the applied tractions at the crack face and other locations, and any combinations of these loading conditions.
The Great Plains Coal Gasification Project Status
Authors: Bodnaruk B. J.
Published: October 2009

The Great Plains Gasification Project is the first commercial-sized plant to produce substitute natural gas from coal in the United States. The plant is designed to convert 14,000 tons/D of North Dakota lignite into 137.5 million standard cubic feet of gas per day. The plant construction has been successfully completed per original design, on schedule and on budget. The plant has also been successfully turned over from construction to operations, as per the original plan. With the completion of the capital projects being implemented at the plant, plans are to achieve 70 percent stream factor in the first year of production (1985). The DOE-Chicago Operations Office has been assigned the responsibility for monitoring the project’s performance against baselines of cost, schedule, and technical criteria. During the startup phase of the project, significant technological advancements have been made and considerable knowledge has been gained, both by the operators and DOE (considering this to be a first of a kind plant built in the U.S.).
Variations of the Lean Blowout Limits of a Homogeneous Methane-Air Stream in the Presence of a Metallic Wire Mesh
Authors: Karim G. A. , Kibrya M. G.
Published: October 2009

The combustion of a homogeneous lean methane-air stream was investigated in a vertical, cylindrical combustor of 150 mm diameter in the presence of a metallic wire mesh. Eight metallic materials were deposited in turn onto a stainless steel wire mesh by electroplating. The potential improvement in the lean blowout limit due to catalytic effects was established separately from those due to the thermal and aerodynamic contributions of the wire mesh and its holder ring. The effectiveness of the various metallic surfaces tested in the lean combustion of methane was in the following descending order: Pt → Cu → Ag → brass → Cr → Cd → Ni → stainless steel. Moreover, it was confirmed that hydrogen was more sensitive to catalytic effects extending to relatively lower temperatures than methane.
Bench Scale Process Evaluation of Reburning for In-Furnace NOx Reduction
Authors: Greene S. B. , Chen S. L. , Pershing D. W. , Heap M. P. , Seeker W. R.
Published: October 2009

Reburning involves the injection of a secondary fuel above the main firing zone of pulverized coal-fired utility boilers to produce a reducing zone which acts to reduce NOx to molecular nitrogen. Overfire air is added above the reburn reducing zone to complete the combustion. Bench scale evaluations of the process carried out in a plug flow furnace at 23 KW have indicated that NOx reductions of up to 70 percent can be achieved depending on a number of process variables. The dominant variables include the initial NOx level that is to be reduced, the reburning fuel type (pulverized coal type or natural gas), and the residence time and temperature in the reducing zone. The reburning process has been combined with the injection of calcium-based sorbents (limestone) to investigate the potential for combined NOx and SOx reduction.
Fuel Deposit Characteristics at Low Velocity
Authors: Szetela E. J. , Giovanetti A. J. , Cohen S.
Published: October 2009

An experimental program has been carried out to characterize the relationship between deposit mass, operating time, and temperature in studies of the thermal stability of aviation gas turbine fuel. This information is required by fuel system designers to prevent deposit buildup in fuel system components, thus allowing for more efficient designs. The program has included the design, fabrication, and operation of a novel thermal stability test apparatus for the determination of deposition rates over a range of temperatures and test durations up to several hundred hours. Experiments were run to determine the rate of deposit formation as a function of temperature in heated stainless steel tubes at low velocity using Jet A fuel. The test tube had an inside diameter of 0.22 cm, a length of 0.91 m, and a flow rate of 0.73 kg/h. Deposits obtained were often characterized as thick, porous, and nonuniform in nature. Deposit density based on carbon content was 0.08 g/cm3. Deposit rates of 0.1 to 100 μg C/h-cm2 were observed at surface temperatures between 400 and 600 K.
Thermal Mechanical Fatigue Life Prediction for Advanced Anisotropic Turbine Alloys
Authors: Pejsa P. N. , Cowles B. A.
Published: October 2009

The most severe stresses that turbine airfoils encounter are thermally induced by extreme temperature gradients and rapid thermal transients. These thermally induced stresses combined with mechanical loading produce thermal mechanical fatigue (TMF) cracking in the airfoil. Analysis of and life prediction for the complex loading situation is further complicated by the use of advanced anisotropic alloys in high turbine sections of modern aircraft engines. In an effort to better understand TMF behavior of these materials, a test program was conducted to simulate turbine airfoil conditions at critical locations. A damage parameter containing terms thought to be essential to the description of material response to TMF cycling was developed. The damage parameter consolidated the data within a factor of approximately 1.5×.
Comparison of Methods for Lifetime Calculations of Highly Loaded Aero-Engine Discs
Authors: Hefele R. , Kappler G. , Rist D.
Published: October 2009

The requirement for low weight-to-thrust ratios of modern aero-engines has led to high structure loads and design of parts in the range of low cycle fatigue. In order to ensure high reliability and optimized TBO’s (time between overhaul), methods to calculate accurately the durability of parts are of great interest. For a highly loaded compressor disc of a fighter engine the lifetime was calculated using the nominal stress method and the maximum local strain concept. The nominal and maximum local stresses and strains were calculated with a finite-element program which was extended to consider plastic deformation of materials. The reference load cycle, which was the same for both methods, was derived from actual load measurements during flight missions. The comparison of the results shows the region of validity of both methods and suggests the application of a modified nominal stress method. Two proposals for improving the nominal stress method by superseding the Neuber-Hyperbolic rule and modifying the mean stress influence in the Goodman diagram are discussed.
A Simplified Thermal Mechanical Fatigue (TMF) Test Method
Authors: Warren J. R. , Cowles B. A.
Published: October 2009

The thermal fatigue environment of gas turbine engine airfoils is severe and is often a life-limiting mode of failure. Alloy and coating system evaluation and accurate service life predictions for advanced turbine blades and vanes are dependent upon realistic laboratory simulation of the engine service environment. Engine conditions are best simulated in the laboratory by mechanical testing capable of imposing simultaneous, independently controlled temperature and strain cycles, or thermal mechanical fatigue (TMF) tests. Historically, TMF tests are expensive and usually require computer-controlled laboratory equipment. Consequently the cost of TMF testing has been prohibitively expensive for airfoil material and coating system evaluation. A simplified, low-cost TMF test method has been developed which is useful for alloy/coating system research and screening. This method, referred to as “load-adjusted TMF” (LATMF), uses load and temperature as the primary test control parameters. Test results using the simplified TMF test method show good correlation (within a factor of two) with the full computer-automated strain control TMF test results.
A Nonlinear Theory of Dynamic Systems With Dry Friction Forces
Authors: Srinivasan A. V. , Cassenti B. N.
Published: October 2009

Structural systems with interfaces where one component may rub against another are not uncommon in aircraft and other engineering structures. The dynamic characteristics of such systems need to be calculated for use in design and such calculations depend on the law of friction used to represent the interacting boundaries. This paper proposes a nonlocal law of dynamic friction and establishes a procedure to incorporate such laws in a general structural dynamic analysis.
Fabrication of Near-Net-Shape Silicon Nitride Parts for Engine Application
Authors: Bandyopadhyay G. , French K. W.
Published: October 2009

Significant advances have been made at GTE for fabrication of near-net-shape silicon nitride parts by injection molding. The technology is now in place to fabricate high-quality, high-density small cross-section (≅0.25 in.) parts such as axial flow gas turbine blades and vanes with state-of-the-art silicon nitride properties. New methods have been developed to fabricate large cross-section (>0.5 in) complex parts with good mechanical properties and reliability.
SCARE: A Postprocessor Program to MSC/NASTRAN for Reliability Analysis of Structural Ceramic Components
Authors: Gyekenyesi J. P.
Published: October 2009

A computer program is developed for calculating the statistical fast fracture reliability and failure probability of ceramic components. The program includes the two-parameter Weibull material fracture strength distribution model, using the principle of independent action for polyaxial stress states and Batdorf’s shear-sensitive as well as shear-insensitive crack theories, all for volume distributed flaws in macroscopically isotropic solids. Both penny-shaped cracks and Griffith cracks are included in the Batdorf shear-sensitive crack response calculations, using Griffith’s maximum tensile stress or critical coplanar strain energy release rate criteria to predict mixed mode fracture. Weibull material parameters can also be calculated from modulus of rupture bar tests, using the least-squares method with known specimen geometry and fracture data. The reliability prediction analysis uses MSC/NASTRAN stress, temperature, and volume output, obtained from the use of three-dimensional, quadratic, isoparametric, or axisymmetric finite elements. The statistical fast fracture theories employed, along with selected input and output formats and options, are summarized. A sample problem to demonstrate various features of the program is included.
Friction Losses and Flow Distribution for Rotating Disks With Shielded and Protruding Bolts
Authors: Zimmermann H. , Firsching A. , Dibelius G. H. , Ziemann M.
Published: October 2009

The friction losses of rotating disks in turbomachines are often increased by protruding bolt heads and surface imperfections, especially at the rim. This can significantly influence the heat production and flow distribution in disk cooling systems. A detailed knowledge of losses and local cooling flows is required to improve the accuracy of both performance and disk life predictions. To this end a thorough experimental study of various disk, bolt, and bolt cover configurations has been carried out. Some of the important test results are presented, and recommendations are given for minimizing windage losses. Empirical influence coefficients based on von Ka´rma´n’s equations for disk friction losses have been derived for different geometries. Furthermore, empirical correlations are proposed for the windage losses of various disk/bolt configurations.
Effects of Honeycomb-Shaped Walls on the Flow Regime Between a Rotating Disk and a Stationary Wall
Authors: Uzkan T. , Lipstein N. J.
Published: October 2009

In gas turbines there are many circumstances where coolant flows are introduced between the rotor disk and the stationary housing. This flow serves not only to supply coolant flow to the disk face, but also to restrict the radial inflow of hot gases to be ingested into the clearance from the turbine blade flow field. The amount of the hot radial inflow is influenced by the difference of the disk pumping capacity and the coolant flow supplied near the center. In order to cool the turbine disk with limited supply of coolant air, some means of reducing the radial inflow of hot gases is needed. It is thought that the use of different surface shapes on the stationary housing would inhibit the disk pumping capacity and, therefore, reduce the radial inflow of hot gases into the clearance. To validate the concept, an experimental study was undertaken. The basic geometry investigated was the flow field between a smooth cylindrical rotating disk parallel to a plain circular coaxial wall open to the free space at the disk periphery. Coolant flow is simulated by supplying air through the bore of the stationary wall into the gap. In addition to the base data obtained with the plain stationary wall, a duplicate series of experiments were run with an open honeycomb facing the stationary wall. The effects of the stationary wall surface geometry is assessed by comparing the data with honeycomb facing against the data with plain stationary wall. The flow field is studied through measurements of the static pressure on the stationary wall, radial and tangential velocity measurements in the clearance, the torque on the drive motor, and coolant flow rates. Flows were studied over a gap spacing to disk radii ratio of 0.01 and 0.10, disk Reynolds numbers from 5×105 to 2.2×106, and throughflow rates from 0 to 3.2 cfs. The results are presented in terms of the tangential and radial velocity profiles in the gap, the static pressure measurements, and the disk torque coefficients. The use of honeycomb on the stationary wall surface grossly altered the ingestion of external flow into the gap from the disk periphery. Important conclusions are: (1) The vacuum in the gap generated by the disk rotation is reduced by a factor of 0.4 to 0.6, depending on the radial location of the point; (2) the core tangential velocity is reduced by a factor of 0.6 to 0.7, depending on the axial spacing and the throughflow number; (3) the critical coolant flow rate is about 63 percent less for the honeycombed surface, as compared to the plain wall case. (4) for a given coolant flow rate, the penetration distance of the radial inflow is much larger for the plain disk than the honeycomb surface.
Lip Separate Flow Blowing and Analysis of Coherence of Inlet
Authors: He Z. W. , Zhang S. Y.
Published: October 2009

It is found experimentally that blowing at the lip separation of an inlet obviously reduces the turbulence at the inlet exit, and apparently reduces the intensity of pressure fluctuations caused by the shock-boundary layer interaction downstream of the throat. The coherence between pressure in the interaction region and total pressure at the exit is also reduced. The coherence between the pressure in the lip separation region and total pressure at the exit is 0.32. If, in addition, there is a stronger shock downstream of the throat, the abovementioned coherence is reduced to 0.06.