bluuebunny/crossref_metadata_2025 huggingface dataset:
An Inverse Time Marching Method for the Definition of Cascade Geometry
Authors: Meauze´ G.
Published: October 2009

The article describes a so-called “inverse mode” calculation method, providing the geometry of a cascade corresponding to a given velocity distribution, and gives some examples of application. The velocity distribution may be assigned over the whole of the suction and pressure sides or over only a part of them, the remaining parts being already known. The closure condition of the profile is ensured by an iterative process on the solidity of the cascade. A second version allows the definition of the geometry of a profile with a given thickness evolution law and as assigned velocity distribution on the suction side. The method makes use of a pseudo-unsteady calculation, enabling one to treat the case of flows with shock waves in a two-dimensional stream with possible variations of cross section. This flexibility of use confers to the method a wide field of application, covering all possible configurations of flow in turbine and compressor cascades.
Mechanical Design of a High-Efficiency 7.5-MW (10,000-hp) Gas Turbine
Authors: Van Buijtenen J. P. , Farrell W. M.
Published: October 2009

This paper describes the mechanical design features on TF-10 gas turbine. The TF-10 gas turbine features an intercooled centrifugal compressor and an annular combustor. A regenerator is added as a standard item. The ISO rating is 7.5 MW (10,000 hp) with a rotor inlet temperature (RIT) of 1116°C (2042°F) and a thermal efficiency of approximately 44 percent. Description of the combustion, rotors, stators, bearings, and shafting is presented.
Turbine Rotor-Stator Interaction
Authors: Dring R. P. , Joslyn H. D. , Hardin L. W. , Wagner J. H.
Published: October 2009

The aerodynamic interaction between the rotor and stator airfoils of a large scale axial turbine stage have been studied experimentally. The data included measurements of the time averaged and instantaneous surface pressures and surface thin film gage output on both the rotor and stator at midspan. The data also included measurement of the stator suction and pressure surface time averaged heat transfer at midspan. The data was acquired with rotor-stator axial gaps of 15 and 65 percent of axial chord. The upstream potential flow influence of the rotor on the stator was seen as well as the downstream potential flow and wake influences of the stator on the rotor. It was also seen that at the 15 percent axial gap, the stator heat-transfer coefficient was typically 25 percent higher than that at the 65 percent gap.
Influence of Free-Stream Turbulence on Boundary Layer Transition in Favorable Pressure Gradients
Authors: Blair M. F.
Published: October 2009

Results from an experimental study of large-scale, two-dimensional incompressible transitional boundary layer flows are presented. Tests were conducted on a heated flat wall with a zero pressure gradient and for two levels of “sink” streamwise acceleration; k = ν/U2 ∂U/∂x = 0.2 or 0.75 × 10−6. Free-stream turbulence intensity levels ranged from approximately 0.7 to 5 percent with limited data obtained outside these values. Convective heat-transfer distributions, laminar, transitional, and fully turbulent boundary layer mean velocity and temperature profile data, and free-stream turbulence intensity distributions are presented. Boundary layer integral quantities and shape factors are also given. Transition onset Reynolds number data obtained for this program agreed well with the results of other experimental and theoretical studies for both zero pressure gradient and accelerating flows. Comparisons of the profile data and wall heat-transfer distribution data indicated that fully turbulent mean velocity profiles were achieved upstream of fully turbulent wall heat-transfer rates.
F-14 Inlet Development Experience
Authors: Tindell R. H. , Hoelzer C. A. , Alexander D.
Published: October 2009

This paper reviews the F-14 inlet design and discusses the wind tunnel and flight test results of investigation that can contribute to move advanced inlet design.
Three-Dimensional Flow Field in the Tip Region of a Compressor Rotor Passage—Part II: Turbulence Properties
Authors: Lakshminarayana B. , Davino R. , Pouagare M.
Published: October 2009

The turbulence properties in the annulus wall region of an axial flow compressor rotor was measured using a triaxial, hot-wire probe rotating with the rotor. The flow was surveyed across the entire passage at five axial locations (leading edge, 1/4 chord, 1/2 chord, 3/4 chord, and the trailing edge location) and at six radial locations in a low-speed compressor rotor. The data derived include all three components of turbulence intensity and three components of turbulence stress. A comprehensive interpretation of the data with emphasis on features related to rotation, leakage flow, annulus wall boundary layer, and blade boundary layer interactions is included. All the components of turbulent intensities and stresses are found to be high in the leakage-flow mixing region. The radial component of intensities and stresses is found to be much higher than the corresponding streamwise components. The turbulent spectra clearly reveal the decay process of the inlet-guide-vane wake within the rotor passage.
Aerodynamic Performance of Large Centrifugal Compressors
Authors: Kano Fumikata , Tazawa Noriyuki , Fukao Yoshiteru
Published: October 2009

The aerodynamic performance of impellers and diffusers of the large centrifugal compressor were studied. A performance design procedure based on the quasi-three-dimensional flow analysis which is combined with the boundary layer theory was developed. The conditions of the boundary layer at the impeller exit and at the diffuser vane throat were calculated, and the three-dimensional measurements were carried out. This result shows that the low momentum flow is accumulated at the corner of the shroud and the blade suction side of the impeller. These results were applied to the development of a large four-stage isothermal compressor which handles the air for an air separation apparatus. This was tested in the field and showed an isothermal efficiency of 76 percent.
Casing Wall Boundary-Layer Development Through an Isolated Compressor Rotor
Authors: Hunter I. H. , Cumpsty N. A.
Published: October 2009

Detailed measurements were made of the casing wall boundary layer development across a large-scale, low-speed axial compressor rotor blade row. An important feature of the work was the use of blading which allowed the tip clearance to be varied. A conventional pressure probe was used to obtain time-averaged measurements of the outer-wall boundary layer downstream of the rotor whilst a hot-wire anenometry technique yielded the three-dimensional, blade to blade structure of the flow. The downstream boundary layer was found to thicken as the rotor loading and blade-end clearance were increased, with fluid tending to accumulate towards the pressure side of the passage. By its pronounced effects upon wall boundary layer development, tip clearance had a deleterious effect upon the performance of the compressor.
CFD Technology for Propulsion Installation Design—Forecast for the 80s
Authors: Paynter G. C.
Published: October 2009

Competition for the world aerospace market will continue to be intense through this decade. The aircraft industry will use CFD in this period to gain an advantageous market position by reducing the cost and risk of achieving viable configurations and removing the test-derived data base as a design constraint. Use of CFD for design implies that parametric analysis will reduce reliance on parametric testing as the basis for configuration selection. Industry will increasingly emphasize development of the technology necessary to support this. Most of the industry will follow a zonal modeling strategy and take advantage of the large vector processing computers now commercially available. Areas which will pace the development of the necessary flow analysis technology include turbulence modeling, numerical error assessment and mesh generation, and experiments for code validation.
Investigation of Blade Vibration of Radial Impellers by Means of Telemetry and Holographic Interferometry
Authors: Haupt U. , Rautenberg M.
Published: October 2009

On a high-pressure, high-mass flow, centrifugal compressor blade vibration measurements are carried out to determine the excitation mechanism in various operating ranges. For these experiments semiconductor strain gages were used. For the transmission of the signals, an 8 channel telemetry system has been installed. A research program was started with blade vibration measurements in different operating ranges of the compressor such as rotating stall, surge and flutter ranges and for the case of nonuniform flow conditions. The results of vibration tests with the impeller at rest showed the stress distribution and the strain directions during blade vibration. This information was used for the choice of the strain gage position on the blade. The experimental results were confirmed by a finite-element calculation considering a segment of the impeller with one blade, which determined the different vibration modes. Further, the steady strain distribution of the impeller due to centrifugal force and temperature was calculated. The investigations were completed by optical measurements to find out the vibration modes of the different blades in rotating operation. These tests were carried out by means of a holographic interferometric system with an optical derotator. The results show the various vibration modes of the blade up to a rotational speed of the compressor of 13,000 rpm.
Acoustic Control of Dilution-Air Mixing in a Gas Turbine Combustor
Authors: Vermeulen P. J. , Odgers J. , Ramesh V.
Published: October 2009

A small combustor of normal design employing acoustic control of the dilution-air flows has been successfully tested up to “half-load” conditions. It has been shown that this technique can be used to control the exit plane temperature distribution; also the ability to trim the temperature profile has been convincingly demonstrated. The acoustic driver power requirements were minimal, indicating that driver power at “full-load” will not be excessive. The nature of the acoustically modulated dilution-air flows has been clearly established as that of a pulsating jet flow with superimposed toroidal vortices. The pressure loss of the unit and its combustion efficiency were insignificantly affected by the acoustic drive. The work contributes to the design of combustors such that a desired exit plane temperature distribution may be achieved.
Flame Imprinted Characteristics of Ash Relevant to Boiler Slagging, Corrosion, and Erosion
Authors: Raask E.
Published: October 2009

Pulverized fuel flames imprint marked characteristics on different particulate species which influence their subsequent behavior in boiler plant. The paper discusses some of the high temperature changes, namely, the transformation of irregularly shaped mineral granulates to spherical shapes found in ash, coal/ash interface behavior and the surface properties of semi-molten ash particles, combustion of the ash-rich coal particles, and the release of potassium from aluminosilicates. This is followed by a brief assessment of relevance of the findings to boiler slagging, corrosion and erosion.
Combustion Roar as Observed in Industrial Furnaces
Authors: Putnam A. A.
Published: October 2009

Factory noise in recent years has become a source of increasing attention, both because of the action of regulatory bodies and because of increased industrial awareness of possible detrimental effects to workers. This paper concerns one significant source of factory noise, namely, combustion roar. Combustion roar accompanies any turbulent flame, premixed or diffusion. Generally, it increases with the rate and intensity of combustion. The effects of several variables, such as firing rate, turbulence intensity, and burner type, on the noise output of flames in an acoustically-infinite situation are first considered. Then, the available information on the changes in the acoustic performance of burners when they are placed in furnaces is discussed. Finally, some remarks are made concerning the suppression of combustion roar.
Naturally Occurring High-Chloride Coal and Superheater Corrosion—A Laboratory Study
Authors: Plumley A. L. , Roczniak W. R.
Published: October 2009

DOE Provided funds for C-E to investigate the fireside corrosion potential of commercial boiler tube alloys at elevated temperatures when exposed to the combustion products from a series of coals. The results of the laboratory and field tests were previously reported. In a supplementary phase of the program, C-E tested for the effect of chloride on similar alloys while firing a naturally occurring high chloride Midwestern bituminous coal in the same laboratory furnace. On the basis of exposure in the convection pass at temperatures from 1100–1700°F, Inconel Alloy 690 was found to have very good resistance to corrosion while Incoloy 800H and Tp-310 s. s. were good transitional materials. Poor materials were T-22, 316 s. s., Inconel 617, and Inconel 671.
Small Particle Transport Across Turbulent Nonisothermal Boundary Layers
Authors: Rosner D. E. , Fernandez de la Mora J.
Published: October 2009

Based on the importance of thermophoretic drift in transporting small particles across a turbulent thermal boundary layer, and the relatively small Brownian diffusivity of such particles, we present a simple asymptotic theory of particulate transport to aerodynamically smooth, solid surfaces cooled below, Te, the mainstream gas temperature. Numerical calculations based on a law-of-the-wall equilibrium velocity profile, and the assumption that the effective eddy diffusivities for mass, energy, and momentum diffusion are equal, are well-represented by −m˙p″≈ρeueωp,e•Sth•(αTLe)w[(Te−Tw)/Tw]{1+[(Te−Tw)/Tw]•[0.07+0.93(αTLew]} where Sth is the local heat-transfer coefficient (Stanton number) and (αTLe)w is the ratio of the particle thermophoretic diffusivity to the gas mixture heat diffusivity. While currently being extended to cover particle size ranges for which (i) the Brownian diffusion sublayer is not negligible in thickness compared to the viscous sublayer, or (ii) eddy impaction sets in, the present theory provides a rational improvement over previous estimates, and explains several important features of the recent data of Nomura et al [1] on the fouling rate of internally air-cooled, gas turbine blades exposed to the products of combustion of Vanadium-containing residual fuel oil.
Lockhopper Valve Testing and Development
Authors: Goff D. R. , Gardner J. F. , Maxfield D. A.
Published: October 2009

As advanced processes are used commercially for converting coal to other forms of energy, reliable valves will be required for operating in lockhopper service at pressures to 1200 psig (8.3 MPa) and temperatures to 1600°F (870°C). The Department of Energy’s Lockhopper Valve Testing and Development Project, being conducted at the Morgantown Energy Technology Center (METC), is cooperating with lockhopper valve manufacturers and users to improve the state-of-the-art capability of commercially available lockhopper valves. The test facilities and valve testing program currently being made available to valve manufacturers at METC are described. The performance of test valves currently in the program is summarized and design considerations for solids lockhopper service are discussed.
Investigation of the Laminar-Turbulent Transition of Boundary Layers Disturbed by Wakes
Authors: Pfeil H. , Herbst R. , Schro¨der T.
Published: October 2009

The boundary layer transition under instationary afflux conditions as present in the stages of turbomachines is investigated. A model for the transition process is introduced by means of time-space distributions of the turbulent spots during transition and schematic drawings of the instantaneous boundary layer thicknesses. To confirm this model, measurements of the transition with zero and favorable pressure gradient are performed.
Three-Dimensional Aerodynamic Characteristics of Oscillating Supersonic and Transonic Annular Cascades
Authors: Namba M. , Ishikawa A.
Published: October 2009

A lifting surface theory is developed for unsteady three-dimensional flow in rotating subsonic, transonic and supersonic annular cascades with fluctuating blade loadings. Application of a finite radial eigenfunction series approximation not only affords a clear insight into the three-dimensional structures of acoustic fields but also provides mathematical expressions advantageous to numerical work. The theory is applied to oscillating blades. Numerical examples are presented to demonstrate three-dimensional effects on aerodynamic characteristics. Three-dimensional effects in supersonic cascades are generally small and strip theory predicts local aerodynamic forces as well as total aerodynamic forces with good accuracy. In transonic flow, however, the strip theory approximation breaks down near the sonic span station and three-dimensional effects are of primary importance.
Influence of Endwall Flow on Airfoil Suction Surface Midheight Boundary Layer Development in a Turbine Cascade
Authors: Sharma O. P. , Graziani R. A.
Published: October 2009

This paper presents the results of an analysis to assess the influence of cascade passage endwall flow on the airfoil suction surface midheight boundary layer development in a turbine cascade. The effect of the endwall flow is interpreted as the generation of a crossflow and a crossflow velocity gradient in the airfoil boundary layer which results in an extra term in the mass conservation equation. This extra term is shown to infuence the boundary layer development along the midheight of the airfoil suction surface through an increase in the boundary layer thickness and consequently an increase in the midheight losses, and a decrease in the Reynolds shear stress, mixing length, skin friction, and Stanton number. An existing two-dimensional differential boundary layer prediction method, STAN-5, is modified to incorporate the above two effects.
Short Duration Heat Transfer Studies at High Free-Stream Temperatures
Authors: Kercher D. M. , Sheer R. E. , So R. M. C.
Published: October 2009

This paper describes short duration heat transfer measurements on a flat plate and a gas turbine nozzle airfoil at high free-stream temperatures. A shock tube generated the high-temperature and pressure air flow. Thin-film heat gages recorded the surface heat flux. The flat plate was tested both in the shock tube and in a shock tunnel placed aft of the tube. Shock tunnel tests on the nozzle airfoil measured the local heat transfer distribution. The flat plate free-stream temperatures varied from 830°R (460 K) to 3190°R (1770 K) for a Tw/TT, g temperature ratio of 0.17 to 0.64 at Mach numbers from 0.12 to 1.34. The nozzle measurements at a Tw/TT, g of 0.35 to 0.39 generally indicate that pressure (concave) surface heat transfer coefficients are high, whereas the suction (convex) surface shows much lower heat transfer coefficients than a turbulent flat-plate correlation.
Measured Coolant Distributions Downstream of Single and Double Rows of Film Cooling Holes
Authors: Afejuku W. O. , Hay N. , Lampard D.
Published: October 2009

A mass-transfer technique has been used to investigate experimentally the distribution of coolant from two rows of holes with independently varied blowing rates. Both staggered and in-line configurations were investigated for two injection angles and a range of row spacings. Detailed concentration distributions measured at and above the surface are presented and a possible mechanism to account for the large differences in behavior between staggered and in-line configurations is discussed.
An Investigation of Ingress for an “Air-Cooled” Shrouded Rotating Disk System With Radial-Clearance Seals
Authors: Phadke U. P. , Owen J. M.
Published: October 2009

In order to model the flow between an air-cooled gas turbine rotor and its stationary casing, a simple isothermal plane rotating disk and stator are used. In tests reported earlier, the cavity between the rotor and stator was sealed by a stationary cylindrical shroud, and the dimensionless minimum amount of “coolant,” Cw, min, necessary to prevent a radial inflow (or ingress) of “hot gas” through the axial clearance between the shroud and the rotor, was determined. In the current tests, a number of seals with a radial clearance between the cylindrical shroud and the rotor are tested. Unlike their axial-clearance counterparts, radial-clearance seals can exhibit a pressure-inversion effect, where the pressure inside the cavity increases, rather than decreases, with increasing rotational speed. Using pressure measurements and flow visualization, correlations showing the variation of Cw, min with clearance ratio and rotational Reynolds number are presented, and it is shown that — under equivalent conditions — a seal with a radial clearance can be much more effective than one with an axial clearance.
Unbalance Response Analysis of a Complete Turbomachine
Authors: Klompas N.
Published: October 2009

A new method is derived to calculate unbalance response of a complete turbomachine, including mount asymmetry, disk flexibility, and fluid-film bearing anisotropy by utilizing conventionally obtained stiffness coefficients for the rotor and stator. Formulation through the coordinates whirl and whip is in real variables with only eight equations per bearing. Whereas the stator is usually ignored, sample analysis illustrates possible strong influence of casing flexibility. Coordinate transformations to enhance visualization and verification of the solution are shown.
The Verification of Concentrated Impurities in Low-Pressure Steam Turbines
Authors: Steltz W. G. , Lee P. K. , Lindsay W. T.
Published: October 2009

The problem of corrosion-assisted low-pressure blade failures is discussed from the water chemistry and aerothermodynamic viewpoints. The physical chemistry of particular steam impurities existing in low-pressure steam turbines is reviewed with special applicability to blade path steam conditions. The interaction of the turbine expansion line with the salt solution zone has been verified by field testing which has, for the first time, demonstrated the existence of concentrated impurities within the low pressure turbine blade path. In addition, the existence of low levels of moisture as measured by an optical moisture probe offers strong evidence that the expansion process in low-pressure steam turbines takes place, on the average, in thermodynamic equilibrium, at least in the vicinity of the saturated vapor line.
A Thermodynamic Efficiency Concept for Heat Exchange Devices
Authors: Witte L. C. , Shamsundar N.
Published: October 2009

A thermodynamic efficiency based on the second law of thermodynamics is defined for heat exchange devices. The efficiency can be simply written in terms of the mean absolute temperatures of the two fluids exchanging heat, and the appropriate environment temperature. It is also shown that for a given ratio of hot to cold inlet temperatures, the efficiency and effectiveness for particular heat exchange configurations are related. This efficiency is compared to second-law efficiencies proposed by other authors, and is shown to be superior in its ability to predict the effect of heat exchanger parameter changes upon the efficiency of energy use. The concept is applied to typical heat exchange cases to demonstrate its usefulness and sensitivity.
Secondary Flow Mixing Losses in a Centrifugal Impeller
Authors: Johnson M. W. , Moore J.
Published: October 2009

Detailed flow measurements made in a 1-m dia shrouded centrifugal impeller running at 500 rpm are presented. All three mutually perpendicular components of relative velocity and rotary stagnation pressures were measured on five cross-sectional planes between the inlet and the outlet, using probes which were traversed within the rotating impeller passage. The reduced static pressures were also calculated from these flow measurements. The measurements were made for an impeller flow rate corresponding to approximately zero incidence at the blade leading edges. Shroud boundary layer separation and secondary flow were observed to lead to the formation of a wake in the suction-side/shroud corner region. It is concluded that the turbulent mixing associated with the shroud boundary layer separation and the strength of the secondary flow strongly influence the size and location of the wake, respectively.
Secondary Flow Effects and Mixing of the Wake Behind a Turbine Stator
Authors: Binder A. , Romey R.
Published: October 2009

In highly loaded turbines with large hub/tip ratios there is a marked increase in secondary flow effects. The optimization of the turbine flow requires detailed knowledge both of three-dimensional cascade flow and of the wake impinging on the downstream rows of airfoils. Therefore, in the DFVLR, thorough investigations of a single-stage turbine with cold air flow were performed. The stator of this turbine was designed for transonic flow and has a hub/tip ratio of 0.756 and an aspect ratio of 0.56. First, measurements were taken without the rotor in several sections behind the turbine stator with special regard to the mixing of the wakes and secondary vortices. Distributions of total pressure loss coefficient and flow direction give the order of magnitude of the mixing losses. Also, position, intensity, structure, and development of secondary vortices are shown. Some complementary measurements were carried out using five-hole probes. They confirm the above described results from two-dimensional measurements.
The Low-Temperature Properties of Aviation Fuels
Authors: Brunton G. , Willcock R. R. , Voisey M. A.
Published: October 2009

A review is presented of work on the low-temperature properties of aviation turbine fuels that has been carried out in recent years at Thornton Research Centre. Details of both simulated full-scale aircraft tank tests and laboratory evaluations are included. Zero holdup is considered as a low-temperature specification parameter and a novel method for measuring its value is described. Experimental results are presented which demonstrate that a change from a freezing point to a flow criterion could provide an increase in fuel availability without prejudicing flight safety.
Effects of Unsteady Free-Stream Velocity and Free-Stream Turbulence at a Stagnation Point
Authors: Gorla R. S. R.
Published: October 2009

An analysis is presented to investigate the combined effects of transient free-stream velocity and free-stream turbulence at a stagnation point on a cylinder situated in a crossflow. A model has been successfully formulated for the eddy diffusivity induced by the free-stream turbulence. The governing momentum equation has been integrated by the steepest descent method. Numerical solutions are provided for the unsteady wall shear stress function for specific free-stream transients. The results are correlated by a new turbulence parameter. It has been found that the wall friction increases with increasing free-stream turbulence intensity. In the case of flows involving unsteady free-stream velocity, the friction factor increases with increasing values of the reduced frequency of oscillations.
Liquid Particle Dynamics and Rate of Evaporation in the Rotating Field of Centrifugal Compressors
Authors: Pinkus O.
Published: October 2009

A model is presented which consists of injecting a liquid coolant into the gas or superheated vapor of centrifugal compressors via slots in the rotating blades. The aim of the injection is minimization of required compression work. The three-dimensional analysis determines the relative velocities and trajectories of the liquid particles, and their rate of vaporization as a function of the prevailing flow field and inlet conditions. Inertia, viscous drag, centrifugal and Coriolis forces are all included. The analysis rests on the assumption of low volumetric liquid/gas ratios so that the aerodynamics of the flow is not appreciably disturbed. The computer-obtained results show that for optimum conditions, and to avoid collision with the blades, it is desirable that injection occur at the suction side of the blades and close to the hub, that low rather than high initial particle velocities are preferred, and that small droplet sizes are required both to avoid blade erosion and to assure the highest rate of vaporization.
Combustion Turbine Deposition Observations From Residual and Simulated Residual Oil Studies
Authors: Whitlow G. A. , Lee S. Y. , Mulik P. R. , Wenglarz R. A. , Sherlock T. P. , Cohn A.
Published: October 2009

Burning residual oil in utility combustion turbines and the consequent deposition on blades and vanes may adversely affect reliability and operation. Corrosion and deposition data for combustion turbine materials have been obtained through dynamic testing in pressurized passages. The deposition produced by the 1900°F (1038°C) combustion gases from a simulated and a real residual oil on cooled Udimet 500 surfaces is described. Higher deposition rates for the doped fuel than for the real residual oil raised questions of whether true simulation with this approach can be achieved. Particles 4–8 μm in diameter predominated in the gas stream, with some fraction in the 0.1–12 μm range. Deposition rates seemed to be influenced by thermophoretic delivery of small molten particles, tentatively identified as magnesium pyro and metavanadates and free vanadium pentoxide, which may act to bond the larger solid particles arriving by inertial impaction to turbine surfaces. Estimated maintenance intervals for current utility turbines operating with washed and treated residual oil agreed well with field experience.
Heavy Fuels Ash Deposit Formation and Removal in Water-Cooled High-Temperature Gas Turbines
Authors: Blanton J. C. , Durgin G. A. , Palko J. E.
Published: October 2009

Experimental data obtained in heavy fuels operation of a gas turbine simulator with a water-cooled, transonic turbine nozzle cascade are presented. The ash fouling is characterized by the rate of decrease of the aerodynamic throat area. Particular attention is given to the cleanability of the ash deposits. A simple heat transfer analysis was performed to assist in evaluating the data. The rate of ash fouling in the water-cooled nozzle was found to be of the same order of magntude as for conventional air-cooled designs. Cleanability, both on and off-line, was found to be significantly enhanced, thus making the water-cooled gas turbine an attractive alternative for heavy fuels applications.
The Influence of Trailing Edge Ejection on the Base Pressure in Transonic Turbine Cascades
Authors: Sieverding C. H.
Published: October 2009

This paper summarizes the results of base pressure studies on transonic turbine blades in the presence of an ejection of coolant flow from a slot in the trailing edge. The first part of the paper reports on tests carried out on a enlarged model of the overhang section of a typical transonic cascade. This model provides valuable information about the detailed trailing edge pressure distribution and points to an asymmetric evolution of the base pressure on both sides of the slot in the presence of a bleed. The second part of the paper presents experimental results from cascade tests covering an outlet Mach number range M2, is = 0.5 to 1.35. These experiments underline the importance of the coolant flow impact on the base pressure and confirm the asymmetry of the base pressure with respect to the cooling slot. Tests with different coolant flow gases point to the significance of a proper simulation of the density ratio between coolant flow and main flow.
The Effect of Inlet Distortion on the Performance Characteristics of a Centrifugal Compressor
Authors: Ariga I. , Kasai N. , Masuda S. , Watanabe Y. , Watanabe I.
Published: October 2009

The present paper concerns itself with the effects of total pressure (and thus velocity) distortion on performance characteristics and surge margin of centrifugal compressors. Both radial and circumferential distortions were investigated. The performance tests as well as the velocity measurements within the impeller passages were carried out with a low-speed compressor test rig with the inlet honeycomb as the distortion generators and compared with the case of “no distortion” as a datum. The results indicated that the inlet distortion exerted unfavorable influences on the efficiency and the surge margin of the given compressor, though the influence of the radial distortion was much stronger than that of the circumferential one. Various distortion indices were further examined in order to correlate the performance to the inlet distortion.
The Use of Optimization Techniques to Design-Controlled Diffusion Compressor Blading
Authors: Sanger N. L.
Published: October 2009

A method is presented for automating compressor blade design using numerical optimization and is applied to the design of a controlled diffusion stator blade row. A general purpose optimization procedure is employed, which is based on conjugate directions for locally unconstrained problems and on feasible directions for locally constrained problems. Coupled to the optimizer is an analysis package consisting of three analysis programs which calculate blade geometry, inviscid flow, and blade surface boundary layers. The optimization concepts are briefly discussed. Selection of design of a two-dimensional blade section is discussed, and design results are presented.
Time-Marching Analysis of Steady Transonic Flow in Turbomachinery Cascades Using the Hopscotch Method
Authors: Delaney R. A.
Published: October 2009

A rapid, time-marching, numerical scheme based on the hopscotch method is presented for solution of steady, two-dimensional, transonic flow in turbomachinery cascades. The scheme is applied to the strong-conservation form of the unsteady Euler equations written in arbitrary curvilinear coordinates. Cascade solutions are obtained on an orthogonal, body-centered coordinate system. Numerical solution results for two turbine cascades are presented and compared with experimental data to demonstrate the accuracy and computational efficiency of the analysis method.
The Influence of Tip Clearance, Stage Loading, and Wall Roughness on Compressor Casing Boundary Layer Development
Authors: Bettner J. L. , Elrod C.
Published: October 2009

An experimental program was conducted in a highly loaded, single-stage, low-speed research compressor that featured variations in blade tip clearances, shroud wall roughness, and stage loading levels. The results showed that tip clearances and stage loading levels exerted a very strong influence on casing boundary layer growth. Shroud wall roughness not only showed some effect on casing boundary layer development, but also influenced stage stall margin. The results point out the need to understand the basic flow processes that occur if realistic mathematical models are to be developed so that casing boundary layer development and its influence on compressor stage performance can be accurately predicted.
Unsteady Three-Dimensional Turbine Aerodynamics
Authors: Joslyn H. D. , Dring R. P. , Sharma O. P.
Published: October 2009

High response aerodynamic measurements were made in a large-scale, axial, flow turbine model to study the unsteadiness and three dimensionality of the flow. High response velocity vector and total pressure data were acquired. A comparison was made of the results of phase lock averaging both raw and reduced data (voltages and velocities). The velocity vector measurements showed that there were strong radial flows present as well as significant periodic changes in the flow field due to relative rotor and vane positions. Random, periodic, and total unsteadiness levels were computed from the instantaneous and phase-lock-averaged velocity data. Time-averaged data were compared with an inviscid two-dimensional calculation. A comparison was also made of time-averaged total pressure measurements obtained from high-response and low-response (steady-state) probes.
The Influence of Coriolis Forces on Gyroscopic Motion of Spinning Blades
Authors: Sisto F. , Chang A. , Sutcu M.
Published: October 2009

Turbomachine blades on spinning and precessing rotors experience gyroscopically induced instabilities and forcing. With vehicle-mounted turbomachines, either constant or harmonic precession occurs, depending on vehicle or mount motion. Responses of uniform cantilever beams at arbitrary stagger, subjected to the noted rotor motion, are predicted in both self-excited and forced-excitation modes taking into account Coriolis acceleration.
Local Heat Transfer to Staggered Arrays of Impinging Circular Air Jets
Authors: Behbahani A. I. , Goldstein R. J.
Published: October 2009

Measurements are made of the local heat transfer from a flat plate to arrays of impinging circular air jets. Fluid from the spent jets is constrained to flow out of the system in one direction. Two different jet-to-jet spacings, 4 and 8 jet diameters, are employed. The parameters that are varied include jet-orifice-plate to impingement-surface spacing and jet Reynolds number. Local heat transfer coefficients vary periodically both in the flow direction and across the span with high values occurring in stagnation regions. Stagnation regions of individual jets as determined by local heat transfer coefficients move further in the downstream direction as the amount of crossflow due to upstream jet air increases. Local heat transfer coefficients are averaged numerically to obtain spanwise and streamwise-spanwise averaged heat transfer coefficients.
A Theoretical Investigation of an Overhung Flexible Rotor Mounted on Uncentralized Squeeze-Film Damper Bearings and Flexible Supports
Authors: Cookson R. A. , Feng Xin-Hai
Published: October 2009

Previous investigations have shown that the uncentralized type of squeeze-film damper is an effective means of reducing the transmission of unbalance forces into the supporting structure. In this theoretical study a more complex model, which includes an overhung “fan” disk and and a noncentral “turbine” disk has been employed. This model represents the conventional gas turbine somewhat closer than does the previously studied single disk system. This investigation has shown that it is possible to minimize the force transmitted into the surrounding structure by a careful selection of squeeze-film damper characteristics, although it may be found that some larger amplitudes of motion accompany the minimized transmissibility.
A Design Calculation Procedure for Shock-Free or Strong Passage Shock Turbomachinery Cascades
Authors: Tong Siu Shing , Thompkins W. T.
Published: October 2009

A previously described, inviscid design technique has been substantially improved to allow the generation of either shock-free, weak-shock or low total pressure loss supersonic rotor cascade designs. Improvements have been introduced in inflow-outflow boundary conditions, imposition of geometric constraints and in shock pressure rise specifications. Calculation examples are presented for precompression type rotor designs.
The Effect of Rotor Blade Thickness and Surface Finish on the Performance of a Small Axial Flow Turbine
Authors: Roelke R. J. , Haas J. E.
Published: October 2009

An experimental investigation was conducted to determine the effect of blade profile inaccuracies and surface finish on the aerodynamic performance of a 11.15-cm tip dia turbine. The as-received cast rotor blades had a significantly thicker profile than the design intent and a fairly rough surface finish. Stage test results showed an increase of one point in efficiency by smoothing the surface finish and another three points by thinning the blade profiles to near the design profile. Most of the performance gain between the as-cast thick and the thinned rotor blades, both with the same surface finish, was attributed to reduced trailing edge losses of the recontoured blades.
A Theory for Boundary Layer Growth on the Blades of a Radial Impeller Including Endwall Influence
Authors: Ekerol H. , Railly J. W.
Published: October 2009

Experimental data on the wall shear stress of a turbulent boundary layer on the suction side of a blade in a two-dimensional radial impeller is compared with the predictions of a theory which takes account of rotation and curvature effects as well as the three-dimensional influence of the endwall boundary layers. The latter influence is assumed to arise mainly from mainstream distortion due to secondary flows created by the endwall boundary layers, and it appears as an extra term in the momentum integral equation of the blade boundary layer which has allowance, also for the Coriolis effect; an appropriate form of the Head entrainment equation is derived to obtain a solution and a comparison made. A comparison of the above theory with the Patankar-Spalding prediction method, modified to include the effects of Coriolis (including mixing length modification, MLM), is also made.
Transonic Compressor Development for Large Industrial Gas Turbines
Authors: Becker B. , Kwasniewski M. , von Schwerdtner O.
Published: October 2009

With increasing mass flow and constant rotational speed of the single shaft gas turbine, the diameters and tip speeds of compressor and turbine blading have to be enlarged. A significant further increase in mass flow can be achieved with transonic compressor stages, as they have been in service in aero gas turbines for many years. For industrial applications, weight and stage pressure ratio are not nearly as important as efficiency. Therefore, different design criteria had to be applied, which led to a moderate front stage pressure ratio of 1.5 with a rotor tip inlet Mach number of 1.37 and a high solidity blading. In order to simulate the first three stages of a 200-MW gas turbine, a test compressor scaled by 1:5.4 was built and tested. These measurements confirmed the aerodynamic performance in the design point very well. The compressor map showed a satisfactory part speed behavior. These results prove that the single-shaft industrial gas turbine still has a high development potential with respect to power increase. Additionally, with the higher pressure ratio, the cycle efficiency will be improved considerably.
Materials Selection for Metallic Heat Exchangers in Advanced Coal-Fired Heaters
Authors: Wright I. G. , Minchener A. J.
Published: October 2009

The application of advanced coal-fired heaters to heat the working fluid for a closed-cycle gas turbine provides some challenging problems for the selection of metallic heat exchanger materials. The requirements of a working fluid temperature of 1550°F (1116 K) at a pressure of 300–600 psig (2.07–4.14 MPa/m2) necessitate that the alloys used for the hottest part of the heat exchanger possess high-temperature strength in excess of that available in widely used alloys like alloy 800. The maximum-duty alloys must therefore be selected from a group of essentially nickel-base alloys for which there is scant information on long-term strength or corrosion resistance properties. The susceptibility to corrosion of a series of candidate heat exchanger alloys has been examined in a pilot plant size fluidized-bed combustor. The observed corrosion behavior confirmed that at certain locations in a fluidized-bed combustor nickel-base alloys are susceptible in varying degrees to rapid sulfidation attack, and must be protected by coating or cladding.
The Calculation of Deviation Angle in Axial-Flow Compressor Cascades
Authors: Wang L. C. , Hetherington R. , Goulas A.
Published: October 2009

The deviation angles of axial flow compressor cascades have been predicted by solving the Reynolds averaged fully turbulent Navier-Stokes equations. A finite element method has been used. To close the problem an algebraic eddy viscosity turbulent model has been chosen. The introduction of the idea of vorticity to the governing equation enables the establishment of a relation between the entropy and the vorticity fields, and the vorticity transport differential equation in the stream function-vorticity method is replaced by a differential operation. A series of calculations have been carried out to examine the influence of cascade geometry on the devotion angle. Very good agreement has been obtained for small angles of incidence with the correlations produced by NASA and using Carter’s rule. Good agreement has also been shown for the variation of deviation angle with the angle of incidence with the experimental data of Felix and Emery, as well as for the distribution of the pressure coefficient along the blade axial chord.
Transient Vibration of High-Speed, Lightweight Rotors Due to Sudden Imbalance
Authors: Sakata M. , Aiba T. , Ohnabe H.
Published: October 2009

In the field of rotor dynamics, increased attention is being given to the transient response analysis of the rotor, since the effects of impact loading and vibrations of the rotor arising from blade loss can be studied by a time transient solution of the rotor system. As recent trends in rotating machinery have been directed towards lightweight, high-speed flexible rotors, the effect of flexibility on transient response analysis is becoming of increasing importance. In the present paper, a transient vibration analysis is carried out on a flexible-disk/flexible-shaft system or rigid-disk flexible-shaft system subjected to a sudden imbalance that is assumed to represent the effect of blade loss. To solve the basic equation governing a rotating flexible disk the Galerkin’s method is used, and the equation of motion of the rotor system is numerically solved by employing the Runge-Kutta-Gill’s method. Experiments were conducted on a model rotor having a blade loss simulator; the shaft vibrations were also measured. The validity of the anaytical results was demonstrated by comparison with the experimental results.
Experimental Evaluation of Squeeze Film Supported Flexible Rotors
Authors: Rabinowitz M. D. , Hahn E. J.
Published: October 2009

This paper describes the experimental investigations which were conducted to verify existing theoretical vibration amplitude predictions for centrally preloaded, squeeze film supported flexible rotors. The influence of measurement errors and operating condition uncertainties are quantified. The agreement between theory and experiment was excellent, and it is shown that any discrepancy can be explained in terms of errors in determining the mean lubricant viscosity and the orbit magnitudes. Hence, for the range of parameters investigated, the theoretical model and predictions therefrom are validated.
Unconditionally Stable Calculation of Transonic Potential Flow Through Cascades Using an Adaptive Mesh for Shock Capture
Authors: Caspar J. R.
Published: October 2009

This paper describes an unconditionally stable procedure for calculating practical transonic potential flows through two-dimensional cascades. The full potential equation is cast in conservation form and approximated in physical space with centered control area techniques. Discrete analogs of nonphysical weak solutions are eliminated by the introduction of artificial viscosity in supersonic regions using artificial compressibility in which the density is evaluated a certain distance upstream from where it is to be applied. An explicit treatment of the density causes standard iterative procedures to diverge, except on relatively coarse meshes on which shocks are poorly captured. Instead, the insight of a model problem analysis is used to treat the density partially and implicitly.