bluuebunny/crossref_metadata_2025 huggingface dataset:
An Approximate Method for Evaluating the Temperature Field in Tubesheet Ligaments of Tubular Heat Exchangers Under Steady-State Conditions
Authors: Singh K. P. , Holtz M.
Published: October 2009

A method to determine the temperature field in a typical tubesheet ligament is developed. Using a numerical example, it is shown that, contrary to the common belief, a temperature gradient may exist throughout the thickness of the tubesheet in heat exchangers operating under “typical” conditions. Such thermal gradients can have significant influence on the exchanger’s thermal and mechanical performance. The solution is developed with an eye to its suitability as a design tool.
A Review of Fast Reactor Design Applications of Swelling and Irradiation Creep
Authors: Foster J. P. , Boltax A.
Published: October 2009

The formulation of empirical swelling and irradiation creep equations from their respective independent data bases is reviewed. These equations are not inclusive of all reactor operating conditions, and the use and applicability of these equations is discussed. The application of swelling and irradiation creep equations in the design of core components is illustrated for both primary and secondary loading situations. The primary (external) loading illustrations include fuel pin performance and duct dilation. The agreement between measurements and predictions using swelling and irradiation creep equations indicates that these equations adequately describe available component performance data. Secondary (internal) loading is illustrated by duct bowing. The necessary component performance and model test data to determine the applicability of swelling and irradiation creep equations are currently in-progress in EBR-II or planned for early FFTF tests.
The Effect of Irradiation Induced Structural Material Deformations on Core Restraint Design
Authors: Kalinowski J. E.
Published: October 2009

A summary of the major considerations in the design of LMFBR core restraint systems is presented. A discussion of these considerations is given using the design features and environment of the Clinch River Breeder Reactor Plant core restraint system design. A comparison of core restraint performance with an alternate concept is provided. Conclusions are drawn on the direction of current and future core restraint system designs.
Development, Fabrication, and Testing of a Prototype Water-Cooled Gas Turbine Nozzle
Authors: Collins M. F. , Muth M. C. , Schilling W. F.
Published: October 2009

The design and development of a water-cooled high temperature gas turbine has been under active investigation by the General Electric Gas Turbine Division for the past 15 years. The transition from testing small scale, laboratory-size experimental hardware to full scale industrial gas turbine components was initiated in 1975 by General Electric and extended further under the U.S. Department of Energy’s High Temperature Turbine Technology (HTTT) program. A key element in this transition was the identification of a composite (hybrid) design for the first stage nozzles. This design permits efficient heat transfer to the water-cooling passageways, thus lowering effective strains and increasing part life. This paper describes the metallurgical considerations and process technology required for such hardware. A review of the materials selection criteria utilized for the nozzle is presented, along with the results of several materials development programs aimed at determining metallurgical compatibility of the component materials, diffusion bonding behavior and both hot corrosion and aqueous corrosion performance of key materials. A brief description of the actual cascade testing of the part is given, along with results of a post-test metallurgical analysis of the tested hardware.
Investigation of the Tip Clearance Flow Inside and at the Exit of a Compressor Rotor Passage—Part II: Turbulence Properties
Authors: Pandya A. , Lakshminarayana B.
Published: October 2009

The flow in the tip clearance region of a compressor rotor is highly turbulent due to the strong interaction of the leakage flow with the annulus wall boundary layer. This paper deals with the turbulence properties of the flow in the tip clearance region of a moderately loaded compressor rotor. The experimental results reported in this paper were obtained using a two-sensor hot-wire probe in combination with an ensemble averaging technique. Blade-to-blade distribution of the axial and tangential turbulence intensities at various radial locations and ten axial locations (four inside the blade passage and the remaining six outside the passage) were derived from this data. Isointensity contours in the clearance region at various radial locations were also obtained from the experimental data. A region of very high turbulence intensities was indicated at the half-chord location from these results. The turbulence intensity profiles also indicated that the leakage flow travels toward the midpassage before rolling up. The turbulence is almost isotropic beyond three-quarter chord downstream of the trailing edge.
An Empirically Based Simulation Model for Heavy-Duty Gas Turbine Engines Using Treated Residual Fuel
Authors: Blanton J. C. , O’Brien W. F.
Published: October 2009

An empirically based engine simulation model was developed to analyze the operation of a heavy-duty gas turbine on ash-bearing fuel. The effect of the ash in the combustion products on turbine efficiency was determined employing field data. The model was applied to the prediction of the performance of an advanced-cooled turbine engine with a water-cooled first-stage nozzle, when operated with ash-bearing fuels. Experimental data from a turbine simulator rig were used to estimate the expected rates of ash deposit formation in the advanced-cooled turbine engine, so that the results could be compared with those for current engines. The results of the simulations indicate that the rate of decrease in engine power would be 32 percent less in the advanced-cooled engine with water cooling. An improvement in predicted specific fuel consumption performance was also noted, with a rate of increase of 38 percent for the advanced-cooled engine.
Fuel Microemulsions for Jet Engine Smoke Reduction
Authors: Naegeli D. W. , Moses C. A.
Published: October 2009

The concept of water and alcohol/fuel microemulsions for the purpose of reducing smoke emissions from jet engine test cells was studied in a T-63 gas turbine combustor. Several ethanol/fuel, methanol/fuel, and water/fuel microemulsions were prepared with JP-4 and JP-8 base fuels and the appropriate surfactants; anhydrous ethanol was miscible in both base fuels. These blends reduced radiation and exhaust smoke, increased CO and total hydrocarbon emissions, and decreased combustion efficiency. NOx was reduced when the surfactant did not contain nitrogen. The reductions in smoke and radiation correlated with changes in the H/C ratio of the fuel blends. Anhydrous ethanol/fuel solutions were most effective in reducing smoke from the standpoint of cost, operational, and systems effects.
Investigation of the Tip Clearance Flow Inside and at the Exit of a Compressor Rotor Passage—Part I: Mean Velocity Field
Authors: Pandya A. , Lakshminarayana B.
Published: October 2009

This paper reports on an experimental study of the nature of the tip clearance flow in a moderately loaded compressor rotor. The measurements reported were obtained using a stationary two-sensor, hot-wire probe in combination with an ensemble averaging technique. The flow field was surveyed at various radial locations and at ten axial locations, four of which were inside the blade passage in the clearance region and the remaining six outside the passage. Variations of the mean flow properties in the tangential and the radial directions at various axial locations were derived from the data. Variation of leakage velocity at different axial stations and the annulus-wall boundary layer profiles from passage-averaged mean velocities were also estimated. The results indicate that there exists a region of strong interaction of the leakage flow with the annulus-wall boundary layer at half-chord. The profiles are well-behaved beyond this point. The rotor exit flow is found to be uniform beyond 3/4 blade chord downstream of the rotor trailing edge.
Measurement of Aerodynamic Work During Fan Flutter
Authors: Kurkov A. P.
Published: October 2009

Stationary high-response pressure and displacement measurements are used to describe the flutter characteristics of the first fan-rotor of a turbofan engine. Flutter occurred at part speed and at high incidence. Several forward and backward traveling waves were identified in a predominantly torsional flutter mode. Positive aerodynamic work contribution was confined to the region close to the leading edge and was mainly due to modes corresponding to forward traveling waves of nodal diameters in the range 3 to 5.
The Influence of Flow Rate on the Wake in a Centrifugal Impeller
Authors: Johnson M. W. , Moore J.
Published: October 2009

Three-dimensional flows and their influence on the stagnation pressure losses in a centrifugal compressor impeller have been studied. All three mutually perpendicular components of relative velocity and stagnation pressure on five cross-sectional planes, between the inlet and outlet of a 1-m dia shrouded impeller running at 500 rpm were measured. Comparisons were made between results for a flow rate corresponding to nearly zero incidence angle and two other flows, with increased and reduced flow rates. These detailed measurements show how the position of separation of the shroud boundary layer moved downstream and the wake’s size decreased, as the flow rate was increased. The wake’s location, at the outlet of the impeller, was also observed to move from the suction surface at the lowest flow rate, to the shroud at higher flow rates.
A Visual Study of Turbine Blade Pressure-Side Boundary Layers
Authors: Han L. S. , Cox W. R.
Published: October 2009

Boundary layer characteristics on the pressure-side of a turbine airfoil were investigated experimentally in a three-blade cascade tunnel. The blades had a chord length of 21 in. to facilitate flow visualization and high-speed photography. The investigation revealed the existence of the Gortler’s vortices appearing in spurts in regions of severe curvature. In the trailing edge region, Karman vortices were detected and found to interact strongly with the Gortler’s vortices convected thereto.
Deposit Formation in Hydrocarbon Fuels
Authors: Roback R. , Szetela E. J. , Spadaccini L. J.
Published: October 2009

A high-pressure fuel coking test apparatus was designed and developed and was used to evaluate thermal decomposition (coking) limits and carbon deposition rates in heated copper tubes for two hydrocarbon fuels, RP-1 and commercial-grade propane. Tests were also conducted using JP-7 and chemically-pure propane as being representative of more refined cuts of the baseline fuels. A parametric evaluation of fuel thermal stability was performed at pressures of 136 atm to 340 atm, bulk fuel velocities in the range 6–30 m/s and tube wall temperatures in the range 422–811 K. In addition, the effect of the inside wall material on deposit formation was evaluated in selected tests which were conducted using nickel-plated tubes. The results of the tests indicated that substantial deposit formation occurs with RP-1 fuel at wall temperatures between 600 and 800 K, with peak deposit formation occurring near 700 K. No improvements were obtained when deoxygenated JP-7 fuel was substituted for RP-1. The carbon deposition rates for the propane fuels were generally higher than those obtained for either of the kerosene fuels at any given wall temperature. Finally, plating the inside wall of the tubes with nickel was found to significantly reduce carbon deposition rates for RP-1 fuel.
Gas Turbine Airflow Control for Optimum Heat Recovery
Authors: Rowen W. I. , Van Housen R. L.
Published: October 2009

Gas turbines furnished with heat recovery equipment generally have maximum cycle efficiency when the gas turbine is operated at its ambient capability. At reduced gas turbine output the cycle performance can fall off rapidly as gas turbine exhaust temperature drops, which reduces the heat recovery equipment performance. This paper reviews the economic gains which can be realized through use of several control modes which are currently available to optimize the cycle efficiency at part load operation. These include variable inlet guide vane (VIGV) control for single-shaft units, and combined VIGV and variable high-pressure set (compressor) speed control for two-shaft units. In addition to the normal control optimization mode to maintain the maximum exhaust temperature, a new control mode is discussed which allows airflow to be modulated in response to a process signal while at constant part load. This control feature is desirable for gas turbines which supply preheated combustion air to fired process heaters.
Effect of Crossflows on the Discharge Coefficient of Film Cooling Holes
Authors: Hay N. , Lampard D. , Benmansour S.
Published: October 2009

The strongest flow parameter governing the film cooling effectiveness provided by a row of holes is the blowing rate. Precise setting of the blowing rate at the design stage requires accurate data for the discharge coefficient of the holes. The effects of crossflow on the discharge coefficient have received scant attention in published work to date. In the present work, the discharge coefficient of single rows of holes has been measured in a specially constructed isothermal rig over a wide range of geometric and flow conditions. Mainstream and coolant Mach numbers have been varied independently over the range 0 to 0.4 for pressure ratios in the range 0 to 2. Cooling hole length to diameter ratios were varied between 2 and 6, and inclinations of 30, 60, and 90 deg were used. The results show that the influence of crossflow is strong and complex, particularly with regard to that on the coolant side. A large range of data is presented sufficient to permit the discharge coefficient to be inferred for many cases of practical importance. Suggestions are also made for a promising theoretical approach to this problem.
Tuning of Turbine Blades: A Theoretical Approach
Authors: Gudmundson P.
Published: October 2009

A perturbation method is described which predicts the changes in eigenfrequencies resulting from geometrical changes of a structure. This dependence is represented by dimensionless functions, one for each eigenfrequency, which vary over the surface of the structure. The functions are presented for each eigenfrequency as isoline plots. An easily estimated integration of these functions allows one to predict a geometrical change which results in a desired change in the resonance frequencies. The method was applied to a turbine blade and a rectangular beam. For the turbine blade isoline plots are presented for the first five eigen frequencies. Eigen frequency changes up to 8 percent were modeled accurately.
Convective Heat Transfer in a Rotating Cylindrical Cavity
Authors: Owen J. M. , Onur H. S.
Published: October 2009

In order to gain an understanding of the conditions inside air-cooled, gas-turbine rotors, flow visualization, laser-doppler anemometry, and heat-transfer measurements have been made in a rotating cavity with either an axial throughflow or a radial outflow of coolant. For the axial throughflow tests, a correlation has been obtained for the mean Nusselt number in terms of the cavity gap ratio, the axial Reynolds number, and rotational Grashof number. For the radial outflow tests, velocity measurements are in good agreement with solutions of the linear (laminar and turbulent) Ekman layer equations, and flow visualization has revealed the destabilizing effect of buoyancy forces on the flow structure. The mean Nusselt numbers have been correlated, for the radial outflow case, over a wide range of gap ratios, coolant flow rates, rotational Reynolds numbers, and Grashof numbers. As well as the three (forced convection) regimes established from previous experiments, a fourth (free convection) regime has been identified.
A Computational Geometry for the Blades and Internal Flow Channels of Centrifugal Compressors
Authors: Casey M. V.
Published: October 2009

A new computational geometry for the blades and flow passages of centrifugal compressors is described and examples of its use in the design of industrial compressors are given. The method makes use of Bernstein-Bezier polynomial patches to define the geometrical shape of the flow channels. This has the following main advantages: the surfaces are defined by analytic functions which allow systematic and controlled variation of the shape and give continuous derivatives up to any required order: and the parametric form of the equations allows the blade and channel coordinates to be very simply obtained at any number of points and in any suitable distribution for use in subsequent aerodynamic and stress calculations and for manufacture. The method is particularly suitable for incorporation into a computer-aided design procedure.
Flow Distributions and Discharge Coefficient Effects for Jet Array Impingement With Initial Crossflow
Authors: Florschuetz L. W. , Isoda Y.
Published: October 2009

Two-dimensional arrays of circular air jets impinging on a surface parallel to the jet orifice plate are considered. The jet flow, after impingement is constrained to exit in a single direction along the channel formed by the jet orifice plate and the impingement surface. In addition to the crossflow which originates from the jets following impingement, an initial (independent) crossflow is present which approaches the array through an upstream extension of the channel. The configurations considered are intended to model the impingement cooled midchord region of gas turbine airfoils in cases where an initial crossflow is also present. Experimentally determined row-by-row streamwise distributions of the jet and crossflow velocities are presented for ratios of the initial crossflow rate to the total jet flow rate ranging from zero to unity. Comparisons are drawn between the measured flow distributions and a theoretical model which is presented. Effects of crossflow velocity and impingement surface proximity on jet hole discharge coefficients are also presented and discussed.
Scaling Effects on Leakage Losses in Labyrinth Seals
Authors: Wittig S. L. K. , Do¨rr L. , Kim S.
Published: October 2009

The accurate prediction of leakage losses through labyrinth seals in gas turbine engines depends largely on exact measurements. As tolerance effects are important, scaled-up models are used for experimental analysis. Application to real size engine conditions is of predominant importance. Measurements in a newly developed test section over wide pressure ranges with geometrically similar straight-through seal models of different scale indicate that the flow coefficient is not independent of scale. In a first attempt to clarify these questions, the results obtained from various models were correlated using Fanno-line analysis with dimensionless integral friction coefficients. The results obtained reveal the necessity for simultaneous consideration of Reynolds and Mach-number effects as well as relatively small geometrical deviations.
Operating and Maintenance Experience With Model V-94 100/135 MW Heavy-Duty Gas Turbines
Authors: Deblon B. , Maghon H.
Published: October 2009

Towards the end of 1974, the first Model V-94 gas turbine with an ISO base-load rating of 91 NW was placed in service and three further similar machines shortly thereafter. The prototype unit has been operated to date for more than 21,000 hr and started up over 3,200 times. It has demonstrated over the past few years excellent operating availability, as well as starting reliability. The paper gives a detailed report of the operating experience and findings gained from the overhauls. It also describes the measures that were taken to achieve high reliability. Since the end of 1979 three uprated V-94 gas turbines employing air-cooled turbine blades with a unit output of up to 125 MW have been taken into operation. The initial experience with these machines is discussed.
Dry Friction Damping Mechanisms in Engine Blades
Authors: Srinivasan A. V. , Cutts D. G.
Published: October 2009

In the context of jet engines, significant vibration damping due to dry friction can occur at (a) shroud interfaces of fans and (b) the platform of turbine blades fitted with “platform dampers.” Analytical and experimental studies in regard to this important source of nonaerodynamic damping of blade vibration are presented in this paper. Comparisons between results from analytical models and laboratory test data are made and discussed.
Status Report—Advanced Heat Exchanger Technology for a CCGT Power Generation System
Authors: Wright D. E. , Tignac L. L.
Published: October 2009

Rocketdyne is under contract to the Department of Energy for the development of heat exchanger technology that will allow coal to be burned for power generation and cogeneration applications. This effort involves both atmospheric fluidized bed and pulverized coal combustion systems. In addition, the heat exchanger designs cover both metallic and ceramic materials for high-temperature operations. This paper reports on the laboratory and small AFB test results completed to date. It also covers the design and installation of a 6×6 ft atmospheric fluidized bed test facility being used to correlate and expand the knowledge gained from the initial tests. The paper concludes by showing the direction this technology is taking and outlining the steps to follow in subsequent programs.
Comparison of Beam and Shell Theories for the Vibrations of Thin Turbomachinery Blades
Authors: Leissa A. W. , Ewing M. S.
Published: October 2009

A great deal of published literature exists which analyzes the free vibrations of turbomachinery blades by means of one-dimensional beam theories. Recently, a more accurate, two-dimensional analysis method has been developed based upon shallow shell theory. The present paper summarizes the two types of theories and makes quantitative comparisons of frequencies obtained by them. Numerical results are presented for cambered and/or twisted blades of uniform thickness. Significant differences between the theories are found to occur, especially for low aspect ratio blades. The causes of these differences are discussed.
Arrays of Impinging Jets With Spent Fluid Removal Through Vent Holes on the Target Surface, Part 2: Local Heat Transfer
Authors: Hollworth B. R. , Lehmann G. , Rosiczkowski J.
Published: October 2009

An extensive study was conducted to determine the heat transfer characteristics of arrays of turbulent air jets impinging on perforated target surfaces. Spent air was withdrawn through vent holes on the surface, rather than along one or more of its edges, as had been done in all previous investigations. An earlier publication presented average heat transfer data for such systems; this paper gives results of comprehensive measurements of local heat transfer. Also given are the results of flow visualization studies, and an approximate mathematical model which predicts distributions of local heat transfer which agree satisfactorily with test data.
A Three-Dimensional Turbulent Flow Analysis Method for the Rotating Channels of a Centrifugal Turbomachine
Authors: Fraser D. A. , Howard J. H. G. , Lennox W. C.
Published: October 2009

A three-dimensional turbulent flow analysis method is described based on transformations of the equations to follow an arbitrary curved passage center-line and allowing for passage area and aspect ratio variations. The numerical method is arranged to allow either parabolic or partially parabolic solution methods in the main passage direction. The method has been tested for radial turbomachine elements and comparisons are included with measured internal passage flows in a radial impeller.
Effect of Using Emulsions of High Nitrogen Containing Fuels and Water in a Gas Turbine Combustor on NOx and Other Emissions
Authors: Singh P. P. , Mulik P. R. , Cohn A.
Published: October 2009

A total of four combustion tests studying the response of various water/fuel emulsion rates on NOx emissions have been conducted on: (a) Paraho shale oil, (b) H-Coal© (372x–522 K) distillate, (c) No. 2 oil doped with quinoline, (d) H-Coal© (505–616 K) distillate, utilizing a 0.14-m dia gas turbine can-type combustor at base-load conditions. Each test fuel run was proceeded with a base-line fuel run with No. 2 distillate oil. The results indicate that the effectiveness of water injection to reduce NOx decreased rapidly with an increase in the fuel-bound nitrogen (FBN) content of the test fuels. The smoke number, in general, decreased with increased water injection, while carbon monoxide and unburned hydrocarbons increased at high water/fuel flow rates.
The Gas Turbine Heat Exchanger in the Fluidized Bed Combustor
Authors: Holt C. F. , Boiarski A. A. , Carlton H. E.
Published: October 2009

In a current research and development program a coal-fired atmospheric fluidized bed combustor is being designed to supply the heat to a closed cycle gas turbine cogeneration system. The major technical effort is directed towards the design of the in-bed heat exchanger, which is required to operate near bed temperature. This high temperature (850° C) exposes the heat exchanger tubes to potentially severe sulfidation. The corrosion behavior depends upon the intimate details of the bed environment and may be related to the occurrence of localized areas of low oxygen partial pressure and high sulfur partial pressure. This paper describes a series of measurements of oxygen partial pressure at various locations within a fluidized bed. The bed, containing densely packed heat exchanger tubes, was operated under various conditions to observe the effect of coal mixing and devolatilization on local oxygen activity. Substantial variations of oxygen partial pressure (below 10−14 atmospheres) were observed. It was noted that these locally severe variations could be substantially modified by changes in coal mixing (as through coal port design). The experiments with varying coal size suggest that rapid devolatilization is desirable and would reduce the extent of locally corrosive environments.
A Theoretical Investigation of Transonic Flows in Radial Compressor Diffusers
Authors: Jeske H. O. , Teipel I.
Published: October 2009

The transonic flow in a diffuser of a centrifugal compressor with high pressure ratio has been analyzed by a numerical procedure. The method consists of an inviscid calculation of the pressure field in the vaned diffuser and of a determination of the boundary layer flow along the blades. The diffuser has been equipped with curved vanes, and only the flow through one channel is considered. The two-dimensional pressure distribution has been calculated by a time-dependent finite difference scheme. The boundary layer flow has been determined by different integral methods with special attention concerning the shock-boundary-layer interaction. Finally, the numerical results are compared with experiments, and the agreement is satisfactory.
Effect of Impeller-Extended Shrouds on Centrifugal Compressor Performance as a Function of Specific Speed
Authors: Sapiro L.
Published: October 2009

Centrifugal compressors for gas compression applications usually employ low-pressure ratio, backward-swept impellers with vaneless diffusers. To increase the compressor flow range and speed, impeller blades are occasionally trimmed, resulting in an extended shroud configuration. The effect of extended front and back impeller shrouds on the performance of centrifugal compressors with vaneless diffusers, and the variation of this effect as a function of specific speed, is thus of concern and is the subject of this paper. An investigation was carried out on two backward-swept shrouded impellers of common blade tip and inducer hub diameters, but different inducer tip diameters (corresponding to low and high specific speeds), with the front and back shrouds extending 20 percent above the blade’s outside diameter.
The Design and Testing of Air-Cooled Blading for an Industrial Gas Turbine
Authors: Hannis J. M. , Smith M. K. D.
Published: October 2009

The design and testing of a cooled high-pressure turbine stage to provide advance information for the Ruston Tornado 6MW industrial gas turbine is described. The cooled stage was designed to replace an existing uncooled stage in a current Ruston gas turbine to allow development testing under actual engine conditions. The instrumentation techniques used on the development engine, including infrared pyrometry, are discussed and results of the tests covering nozzle vane and rotor blade cooling under steady-state and transient conditions and engine performance are presented and compared with the design predictions.
Optimal Design of Squeeze Film Supports for Flexible Rotors
Authors: Rabinowitz M. D. , Hahn E. J.
Published: October 2009

Assuming central preloading, operation below the second bending critical speed, and full film lubrication, this paper presents a theoretical model which allows one, with minimum computation, to design squeeze film damped rotors under conditions of high unbalance loading. Closed form expressions are derived for the maximum vibration amplitudes pertaining to optimally damped conditions. The resulting vibration amplitude and transmissibility data of design interest are presented for a wide range of practical operating conditions on a single chart. It can be seen that for a given rotor, the lighter the bearing the more easily one can satisfy design constraints relating to allowable rotor vibration levels and lubricant supply pressure requirements. The data presented are shown to be applicable to a wide variety of rotors, and a recommended procedure for optimal design is outlined.
An Improved Time-Marching Method for Turbomachinery Flow Calculation
Authors: Denton J. D.
Published: October 2009

Time-marching solutions of the Euler equations are now very widely used for calculation of flow through turbomachinery blade rows. All methods suffer from the disadvantages of shock smearing, lack of entropy conservation, and comparatively long run times. A new method is described which reduces all these problems. The method is based on the author’s opposed difference scheme, but this is applied to a new grid consisting of quadrilateral elements which do not overlap and have nodes only at their corners. The use of a non-overlapping grid reduces finite differencing errors and gives complete freedom to vary the size of the elements. Both these factors help to improve entropy conservation. Considerable savings in run time (by a factor of about 3) are obtained by using a simple multigrid method whereby the solution is advanced simultaneous on a course and on a fine grid. The resulting method is simpler, faster, and more accurate than its predecessor.
The Control of Engine Vibration Using Squeeze Film Dampers
Authors: Holmes R.
Published: October 2009

This paper describes the following roles of a squeeze-film damper when used in gas turbine applications as a means of reducing vibration and transmitted force due to unbalance: (a) as an element in parallel with a soft spring in a vibration isolator; and (b) as an element in series with the stiffness of the engine pedestal. The effects of cavitation on performance are elucidated, and the dangers of jump phenomena and subsynchronous response are discussed. Experimental work is described in which both roles of the squeeze-film damper are investigated and the results are compared with theoretical predictions.
The Elliptic Solution of the Secondary Flow Problem
Authors: Abdallah S. , Hamed A.
Published: October 2009

This paper presents the elliptic solution of the inviscid incompressible secondary flow in curved passages. The three-dimensional flow field is synthesized between 3 sets of orthogonal nonstream surfaces. The two-dimensional flow field on each set of surfaces is considered to be resulting from a source/sink distribution. The distribution and strength of these sources are dependent on the variation in the flow properties normal to the surfaces. The dependent variables in this formulation are the velocity components, the total pressure, and the main flow vorticity component. The governing equations in terms of these dependent variables are solved on each family of surfaces using the streamlike function formulation. A new mechanism is implemented to exchange information between the solutions on the three family surfaces, resulting into a unique solution. In addition, the boundary conditions for the resulting systems of equations are carefully chosen to insure the existence and uniqueness of the solution. The numerical results obtained for the rotational inviscid flow in a curved duct are discussed and compared with the available experimental data.
The Effect of Journal Misalignment on the Oil-Film Forces Generated in a Squeeze Film Damper
Authors: Cookson R. A. , Feng X. H. , Kossa S. S.
Published: October 2009

Squeeze film damper performance is usually assessed on the assumption that the axis of the journal is parallel to that of the bearing housing. For many practical cases, for example that of the overhung fan shaft in an aero gas turbine, these two elements are unlikely to be parallel, even when self-aligning bearings are used. In this theoretical study an attempt has been made to evaluate the effect of misalignment on the magnitude of the oil-film forces produced in a squeeze film damper bearing, and to this end a computational procedure has been established. From the results reported in this paper, it has been clearly shown that the effect of misalignment in a two-land, squeeze film damper can lead to a significant increase in the transmission of unbalance force through the oil film, As an example, data from a previously reported investigation into the performance of a simple two-bearing model with a single centrally supported disk have been used in a typical calculation. The results from this computation indicated that the oil-film forces generated, could have been several times greater than those calculated on the assumption that the journal and bearing housing were parallel. Unfortunately, there do not appear to be any clear guidelines to lay down to the designers of squeeze film dampers at this moment, in relation to journal misalignment. In general, the effect of misalignment is strongest when the ratio of land-length to radial clearance is greatest, when large unbalance is being accommodated, and when the orbit size is large. In our own analytical studies, the effect of misalignment is allowed for whenever the angle of misalignment is greater than 0.0005 radians.
Aerodynamic Damping Measurements in a Transonic Compressor
Authors: Crawley E. F.
Published: October 2009

A method has been developed and demonstrated for the direct measurement of aerodynamic damping in a transonic compressor. The method is based on the inverse solution of the structural dynamic equations of motion of the blade-disk system. The equations are solved inversely to determine the forces acting on the system. If the structural dynamic equations are transformed to multiblade or modal coordinates, the damping can be measured for blade-disk modes, and related to a reduced frequency and interblade phase angle. This method of damping determination was demonstrated using a specially instrumented version of the MIT Transonic Compressor run in the MIT Blowdown Compressor Test Facility. No regions of aeroelastic instability were found. In runs at the operating point, the rotor was aerodynamically excited by a controlled two-per-revolution, fixed, upstream disturbance. The disturbance was sharply terminated midway through the test. Analysis of the data in terms of multiblade modes led to a direct measurement of aerodynamic damping for three interblade phase angles. Comparison between experimental damping values and theoretical values calculated using a weak shock two dimensional analysis show reasonable agreement.
Nonlinear Analysis of Rotor-Bearing Systems Using Component Mode Synthesis
Authors: Nelson H. D. , Meacham W. L. , Fleming D. P. , Kascak A. F.
Published: October 2009

The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems has been written and results are presented for transient system response associated with blade loss dynamics, with squeeze film dampers, and with interference rubs.
Investigation of F/A-18A Engine Throttle Usage and Parametric Sensitivities
Authors: Hall C. L. , Hathaway R. W. , Cote´ S. M.
Published: October 2009

Projection of realistic engine usage is essential for advanced tactical fighter aircraft to avoid significant durability problems and associated high weapon system costs. Previous engines such as the TF41 and F100 experienced durability deficiencies because actual field usage was more severe than initial projections. Thus, MCAIR developed systematic prediction procedures to provide improved usage estimates for preliminary design. These procedures based on digital flight simulation models were used to investigate throttle usage for peacetime training flights of the Navy F/A-18A aircraft with F404-GE-400 engines. The purpose was to identify major contributors to engine damaging usage and provide an early assessment of anticipated F/A-18A field utilization. Data are presented for individual mission throttle cycles and time histories as well as composite engine duty cycles. The prediction procedures were validated demonstrating excellent agreement by comparing results with flight data from the contractor phase of the Navy’s Accelerated Service Test (AST) at Patuxent River Naval Air Station (NAS). Engine usage was projected for F/A-18A transitional training at Lemoore NAS, the first deployment site. Results indicate that the severity of cycles and hot time at Lemoore will be comparable to that for AST. The ground attack, air combat, and air intercept missions were found to contribute the most to usage. Sensitivities were also evaluated parametrically for F/A-18A aircraft performance and mission parameter variations. Usage was found to be most sensitive to aircraft thrust to weight, and insensitive to store drags. The results provide valuable insight into how missions, maneuvers, and aircraft performance parameters affect usage which is important for cost effective design of durable, high-performance engines.
Some Aspects of Constant Pressure Turbocharged Marine Diesel Engines of Medium and Low Speed
Authors: Azuma T. , Yura T. , Tokunaga Y.
Published: October 2009

The constant pressure turbocharge system is widely used in marine diesel engines because of its high thermal efficiency. This study has been made to establish a simulation system for exhaust gas pulsation of the constant pressure turbocharge system and to clarify its characteristics. The previous paper reported that the pressure fluctuations measured on test units and some engines agreed very well with those simulated by the scheme developed in this study. The study used the characteristic method for solving the differential equations of unsteady flow. This report will first discuss the high thermal efficiency of this turbocharge system in the range of high mean effective pressure, then it will show the advantages of the two-step Lax-Wendroff’s method in solving the unsteady flow equations in comparison with the characteristic method. Furthermore, it will present some characteristics of the pulsation and the unique pulsation resonance in this turbocharge system.
Materials Development for HTGR Heat Exchangers
Authors: Johnson W. R. , Roberts D. I.
Published: October 2009

High-temperature, gas-cooled reactors (HTGR’s) are uranium/thorium-fueled, graphite-moderated, helium-cooled systems capable of producing high-temperature primary coolant. Several variants of this system are under active development in the United States and worldwide. In one version, the primary coolant heat is transferred to steam generators producing 538°C/16.5 MPa steam for use in electricity generation or process heat applications. The materials and design technology for steam generators in this system are well developed, relying heavily upon prior experience with fossil-fired steam generators and the steam generators of the commercial HTGR’s. The major work that remains to be done is to complete qualification of the materials and to respond to evolving rules pertinent to elevated-temperature nuclear design and construction. Other versions of the HTGR generate much higher primary coolant gas temperatures (850° to 950°C) and exchange this heat, through intermediate heat exchangers (IHX’s), to a secondary loop for higher temperature process heat applications. Although IHX’s for these systems are typically pressure-balanced (low-stress) units, their design involves several challenges, including the potential interactions between structural materials and impurities present in the HTGR primary coolant. Considerable work is required to qualify materials for IHX applications, including detailed mechanical property characterization, determination of environmental influences on performance, provision of welding materials and procedures for producing joints of adequate strength and integrity, and provisions for wear protection. Some of the work currently under way addressing these issues is described.
Boiling Heat Transfer in a Narrow Eccentric Annulus, Part I: Dryout
Authors: Johnston B. S. , Sharon A. , Kozawa Y. , Bankoff S. G.
Published: October 2009

An experimental apparatus was used to simulate the annular crevice formed by a heated tube and drilled tube support plate (TSP) in a pressurized water reactor recirculating steam generator. The aim of the experiment was to explore the conditions required for the formation and maintenance of a dry region. Water at 0.69 MPa or atmospheric pressure was circulated through the crevice. Visual observations and tube wall temperature measurements were obtained and compared to synthesize a description of the crevice boiling processes. It was determiend that a stable dry patch exists about a line of contact between tube and TSP above a wall superheat of 2–3°C. However, separating the tube and TSP by about 0.025 mm allows the dry patch to be rewet.
Boiling Heat Transfer in a Narrow Eccentric Annulus, Part II: Heat Transfer
Authors: Johnston B. S. , Sharon A. , Bankoff S. G.
Published: October 2009

An experimental apparatus was used to simulate the annular crevice formed by a heated tube and drilled tube support plate (TSP) in a pressurized water reactor recirculating steam generator. A previous paper [1] has described the stable dryout phenomena which occur. This paper discusses the heat transfer mechanisms in the contact and wide gap regions of the crevice. Changes in flow rate and inlet enthalpy are found to have little effect on the patch extent and contact line temperature, while an increase in diametral gap size decreases both. Increasing the thermal conductivity of the TSP also reduces the contact line temperature, but does not affect the wide gap region.
The Effect of Flat Bar Supports on the Crossflow Induced Response of Heat Exchanger U-Tubes
Authors: Weaver D. S. , Schneider W.
Published: October 2009

A wind tunnel study was conducted to determine the effect of flat bar supports on the crossflow induced response of heat exchanger U-tubes. The 13-mm-dia tubes formed a triangular array with a pitch ratio of 1.57 and a mean U-bend diameter of about 1.5 m. A 0.3-m-long section of the array was exposed to a flow parallel to the plane of the U-bends. Experiments were conducted with no supports, with one set of flat bars at the apex, and with two sets of flat bar supports at the apex and 45 deg points. In each case, the tube response was monitored to a flow velocity beyond that required for fluid elastic instability. Limited experiments were also conducted to examine the effect of tube support clearance on tube response. Conclusions are drawn regarding the effectiveness of flat bars as U-bend antivibration supports.
Droplet Size Effects on NOx Formation in a One-Dimensional Monodisperse Spray Combustion System
Authors: Sarv H. , Nizami A. A. , Cernansky N. P.
Published: October 2009

A one-dimensional monodisperse aerosol spray combustion facility is described and experimental results of post-flame NO/NOx emissions are presented. Four different hydrocarbon fuels were studied: isopropanol, methanol, n-heptane, and n-octane. The results indicate an optimum droplet size in the range of 43-58 microns for minimizing NO/NOx production for all of the test fuels. This NOx behavior is associated with droplet interactions and the transition from diffusive type of spray burning to that of a prevaporized and premixed case. Decreasing the droplet size results in a trend of increasing droplet interactions, which suppresses temperatures and reduces NOx. This trend continues until prevaporization effects begin to dominate and the system tends towards the premixed limit. The occurrence of the minimum NOx point at different droplet diameters for the different fuels appears to be governed by the extent of prevaporization of the fuel in the spray and is consistent with theoretical calculations based on each fuel’s physical properties.
An Analysis of the Performance of a Gas Turbine Cogeneration Plant
Authors: Baughn J. W. , McKillop A. A. , Treleven K.
Published: October 2009

A computer program has been developed to analyze the thermodynamic performance of a cogeneration plant. Results of parametric studies using this program include partial load operation, inlet air cooling, and supercharging. Fuel chargeable to power, a previously used figure-of-merit, is used to evaluate the performance for partial-load operation. Fuel chargeable to incremental power and differential steam efficiency are two new figures-of-merit for evaluating other design alternatives: the former for incremental increases in electric power output, the latter for incremental increases in steam output at the expense of electrical power output.
Deposition Results of a Transpiration Air-Cooled Turbine Vane Cascade in a Contaminated Gas Stream
Authors: Raj R.
Published: October 2009

The experimental data are presented on the deposition of particulate on transpiration air-cooled turbine vanes operating in a cascade for a series of tests using distillate fuel contaminated with alumina or fly ash. The data are discussed in view of the known mechanisms of deposition. Qualitative discussion of the role of electrostatic charge on the deposition in gas turbines is also presented.
A Study of the Surface Deterioration due to Erosion
Authors: Tabakoff W. , Balan C.
Published: October 2009

Turbomachines are subject to an excessive rate of erosion when operated in dusty environments or exposed to combustion gases of newly developed synthetic fuels or heavy oils. The surface quality of the blades exposed to such particulate flow deteriorates. With time, the surface roughness increases and leads to a decrease in engine performance. This paper presents the results of the experiments carried out in an erosion wind tunnel on 6061T6 aluminum specimens to study the roughness formations. The particles used were silica sand.