bluuebunny/crossref_metadata_2025 huggingface dataset:
An Experimental Investigation of Film Cooling on a Turbine Rotor Blade
Authors: Dring R. P. , Blair M. F. , Joslyn H. D.
Published: October 2009

Film cooling has been studied on the rotor blade of a large scale (low speed) model of a high pressure turbine first stage. Film coolant was discharged from single holes on the pressure and suction surfaces of the airfoil. For each blowing site the coolant to free stream mass flux ratio and density ratio were varied from 0.5 to 1.5 and from 1.0 to 4.0 respectively. Both surface flow visualization and local film cooling adiabatic effectiveness data were obtained. The observation was made that although it can have a strong radial component, the trajectory of the film coolant was very insensitive to coolant flow conditions. The existence of the radial component of the film coolant trajectory was found to have a strong impact on the nature of the effectiveness distribution. The data have been compared with data taken by other investigators on flat surfaces and in plane cascades. Agreement between the flat plate data and the suction surface data was reasonably good. However, the pressure surface results showed a much faster decay of the effectiveness than did the flat plate data due to effects thought to be related to both curvature and radial flow.
Use of the Characteristic Method for the Prediction of the Three-Dimensional Flow Field in High Transonic Compressors
Authors: Martinon J.
Published: October 2009

The strong pressure gradients that take place in high performance transonic axial flow compressors induce important viscous interaction effects. In order to estimate these effects and to calculate the flow field in the inviscid core, the perfect gas approach is necessary. A three-dimensional stationary characteristic method is used for such an approach, and numerical results are given for the flow field in: • the blade channel of a supersonic cascade with converging side walls, • the blade channel of an annular supersonic cascade, • the inlet region of a linear supersonic blade cascade with converging side walls.
Starting Torque Characteristics of Small Aircraft Gas Turbines and APU’s
Authors: Rodgers C.
Published: October 2009

Starting torque characteristics of small self-sufficient gas turbine engines often present a belated problem to the development engineer, particularly when proceeding into final engine qualification testing over the required range of operational environments. A common procedure is therefore to conservatively over-design the start system with consequent penalties in weight, cost, and size. The various aspects of engine starting are discussed and it is shown that the dominant factor controlling start characteristics at sub-zero ambient temperatures is lubricant viscous shear effects. The magnitude of this effect is such that stored energy start system weights for rapid starting of small aircraft auxiliary power units may weigh as much as the power unit itself. The same auxiliary power units, if used as starters for larger main propulsion gas turbines, are burdened with the incompatibility of torque output dependent upon air density, yet main engine cranking torque is dependent basically upon lubricant viscosity. It is concluded that start system over-design philosophy will tend to persist pending the application of external starting torque directly to the high speed shaft itself with uncoupling of all but necessary viscous parastic shear sources, or until such time as detailed research and development is devoted in applied tribology to further reduce viscous shear effects in high speed turbo-machinery.
Application of All-Ceramic Nozzle to Radial Flow Turbine
Authors: Napier J. C.
Published: October 2009

An all-ceramic turbine nozzle offers the capability for improved erosion resistance and up-rated turbine inlet temperature. This yields significant improvement in engine durability and performance. Results of ceramic turbine nozzle engine tests and engine simulator tests for a small radial flow gas turbine are presented. The effects of erosive particles and ingested sea salt on the ceramics are included in this work.
Recent Developments on Gas Turbine Control Systems
Authors: Greenhalf P. D.
Published: October 2009

The paper briefly outlines some of the activities undertaken on gas turbine logic and control systems. The frequent requirement for gas turbines to operate in polluted hostile environments has encouraged the development of ancillary equipment which will reliably withstand onerous site conditions. The design requirements, philosophy, component selection and progress made on fuel control and solid state logic systems, specifically introduced to meet arduous service requirements are reviewed. A computer control system designed for more temperate environments is also examined, enabling a comparison of the theoretical reliabilities of the respective systems to be assessed when installed on gas compressor applications.
Evaluation of Laminated Porous Wall Materials for Combustor Liner Cooling
Authors: Nealy D. A. , Reider S. B.
Published: October 2009

Some of the work at Detroit Diesel Allison (DDA) that has been aimed at the synthesis, characterization, and evaluation of a promising porous wall combustor-cooling concept featuring electrochemically etched, multilayer, diffusion-bonded sheet structures (Lamilloy) is briefly reviewed. The specific considerations of cooling effectiveness, design flexibility, fabrication complexity, and special operational and durability problems are considered in light of relevant engine and rig experience.
Mechanical Reliability Considerations in the Modern High Temperature Industrial Gas Turbine
Authors: Korta J. J.
Published: October 2009

The mechanical design considerations of the CW352 two shaft industrial type gas turbine are discussed with emphasis on achieving a high degree of mechanical reliability based on the extensive service experience of the company’s mature 1450°F inlet machines. Problem areas of the early units are discussed and how avoidance of problems has been considered in the design of the CW352.
The Relationship of Power and Heat Production with Closed Cycle Gas Turbines
Authors: Frutschi H. U.
Published: October 2009

As is well known, a part of the waste heat of closed cycle gas turbines can be used without any reduction in power production. However, if the plant is designed for optimal power conversion, the outlet temperatures of the repeatedly intercooled compressors are so low, that only a small part of the removed heat is useful. The closed cycle gas turbine compressor behaves analogous to a heat pump, and therefore an increase of useful heat can be realized without an undue reduction in power production. A moderate increase of the cycle pressure ratio above its optimum, a temperature increase at the compressor inlet and a reduction of the number of intercoolers are good methods for this. Measures, however, which bypass heat from the heater to the precooler, such as recuperator bypass, are not of interest. As far as closed gas turbines are considered, a further degree of freedom is given by the possibility of cycle gas inventory control, as demonstrated in combined power and heat production characteristics. These explanations are not only relevant for fossil fired plants, but also for nuclear high temperature reactors with helium turbines proposed in future.
Industrial Type Gas Turbines for Offshore Applications
Authors: Elmhed G. , Ferm S. , Svensson S. O.
Published: October 2009

The paper discusses, with reference to the power generating gas turbines on the FRIGG TCP-2 platform, the specific and general requirements for offshore gas turbines, and how those sometimes conflicting requirements are met. Furthermore, interesting details of the particular installation on the FRIGG TCP-2 platform are described. The gas turbines on the FRIGG TCP-2 platform are the first ones to be installed in Norwegian water after the Norwegian regulations for “Production and auxiliary systems on production installations, etc.” were officially issued in April 1978. Some of these special regulations and their influence on the gas turbine design are discussed.
The Role of the Ceramic Heat Exchanger in Energy and Resource Conservation
Authors: McDonald C. F.
Published: October 2009

The approaching era of strict energy conservation and eventual energy shortage will have a profound effect on the design of process and power-producing plants, since in the future maximum fuel utilization efficiency will be of the essence. The intrinsic economic worth of industrial reject and exhaust heat is too great to merely discharge to the environment, and means of utilizing this energy by improved process efficiency, or by cogeneration, must be quickly brought to the commercial stage. For future power conversion systems, and in particular open- and closed-cycle gas turbines, emphasis will be placed on maximizing efficiency, and in many cases this can be achieved only by significant increases in operating temperatures. For future gas turbines, process heat plants, chemical plants, basic industries, and waste heat recovery applications, the high level of reject temperature will necessitate the utilization of ceramic heat exchangers for thermal energy recovery. In this paper, current development activities in the field of ceramic heat exchangers for gas turbine applications are discussed, and it is projected that the encouraging results from these programs will stimulate a broader interest in high-temperature waste heat energy recovery. The future role the ceramic heat exchanger will play in energy recovery for different industrial applications is emphasized, and appropriate heat exchanger design criteria, types of construction, surface geometries, and development activities are briefly discussed.
Measurements of the Four-Quadrant Characteristics on a Multi-Stage Turbine
Authors: Bammert K. , Zehner P.
Published: October 2009

With turbines, operation conditions far from the design range are possible. With gas turbines, in nuclear and solar energy plants in the case of a fault, flow in reverse directions may even occur. For extreme operations insufficient knowledge was available, so measurements were carried out at first on a single-stage turbine and then on a seven-stage turbine, with both the mass flow and the rotor speed systematically varied in the positive (normal direction) and negative ranges (four-quadrant characteristics). The measurement on the seven-stage turbine basically tally with the single-stage measurements. Stage performance curves can be approximately calculated also for four quadrants from the cascade characteristics of the middle section. The calculated curves are compared to the results of the single-stage measurements. During operation far from the design point, the individual stages of a multi-stage turbine work at a wide variety of operating points, so the characteristics of such a turbine have to be determined by the superimposition of the corresponding stage performance curves on each other.
Forced Vibrations of a Single Stage Axial Compressor Rotor
Authors: Fabunmi J. A.
Published: October 2009

A semi-empirical method, utilizing modal analysis based on experimentally obtained modeshapes has been used to study the vibration response of a 23 bladed axial compressor rotor. The system modeshapes, characterized by the blade deflections at resonance, are more or less irregular depending upon the proximity of the system frequencies to the blade cantilever frequencies. The response of the detuned bladed disk assembly to various types of harmonic excitations are shown to be predictable if sufficient experimental information is available about the resonant modes and frequencies of the system.
Aerodynamic and Aeroelastic Characteristics of Oscillating Loaded Cascades at Low Mach Number—Part II: Stability and Flutter Boundaries
Authors: Akai T. J. , Atassi H.
Published: October 2009

The aerodynamic coefficients obtained from the analysis developed in Part I of this paper are utilized here to investigate stability and flutter boundaries for loaded cascades of airfoils with finite thickness. Combined bending and torsional oscillations for different stiffness ratios are studied for compressor and turbine cascades. The results show very significant effects of blade geometry and mean flow incidence on the stability and flutter boundaries. These effects are basically the consequence of strong coupling between the steady and unsteady aerodynamics of the cascade.
Optimization for Rotor Blades of Tandem Design for Axial Flow Compressors
Authors: Bammert K. , Staude R.
Published: October 2009

The tandem cascades investigated consist of two retarding cascades closely arranged behind one another. The influences of the flow interference for the pressure distribution at the profiles, for the losses and the outlet angle are discussed. Various cascade configurations are theoretically and experimentally investigated to find out the optimum range of the axial spacing and for the displacement in circumferential direction. An example shows how rotor blades of tandem design can be optimized for minimal profile losses. The aim is to find the optimum configuration for each of the design sections of the rotor blades. A further condition is to avoid additional bending stresses due to centrifugal forces, so that tandem rotor blades can run with relatively high speed.
An Analysis of Aeroengine Fan Flutter Using Twin Orthogonal Vibration Modes
Authors: Ford R. A. J. , Foord C. A.
Published: October 2009

Flutter prediction methods for aeroengine fans at present typically combine a complex aerodynamic analysis with a simple model of the mechanical behavior of the fan. In this paper a more sophisticated model of the mechanical response is used to investigate flutter and provide additional insight into the physical mechanisms involved. The model incorporates twin orthogonal modes, which are two independent vibration patterns similar in shape and resonant frequency but displaced 1/4 wave circumferentially in space. Flutter can be thought of as a self excited vibration in which the response of each blade in one mode generates aerodynamic forces on the blades which drive the twin mode—and vice versa. The flutter frequency can be determined by considering the phasing between the twin modes; whether flutter does actually occur (at this frequency) depends upon the relationship between the aerodynamic force coefficients and the amplitude response of each mode. The greatest tendency to flutter occurs when the twin modes are identical in frequency. For the more practical case of a frequency split between the modes the tendency to flutter decreases with increased frequency separation, and the vibration pattern becomes non-uniform. The non-uniformities include unequal blade amplitudes, unequal interblade phase angles, variation from blade to blade in the temporal phase between twist and flap within each individual blade, and a deflected shape which is not sinusoidal circumferentially.
The Development of Wake Flow in a Centrifugal Impeller
Authors: Johnson M. W. , Moore J.
Published: October 2009

Three-dimensional flow, leading to the formation and the growth of a wake in a centrifugal impeller, has been studied. Results of flow measurements in a 1 m dia, shrouded, centrifugal compressor impeller running at 500 rpm are presented. Relative velocities and rotary stagnation pressures (p* = p + 1/2ρW2 − 1/2ρω2r2) were measured, on five cross-sectional planes between the inlet and outlet of the impeller, using pressure probes which were traversed within the rotating impeller passage. Particular attention was given to the convection of low p* fluid by secondary flows and to the formation of the wake in the shroud/suction-side corner region of the passage.
Effect of Interblade Phase Angle and Incidence Angle on Cascade Pitching Stability
Authors: Carta F. O. , St. Hilaire A. O.
Published: October 2009

A comprehensive test program was performed at low subsonic velocity on a linear cascade of airfoils oscillating in pitch about their midchords for incidence angles up to 10 deg, reduced frequencies up to 0.193, and over a range of interblade phase angles from σ = −60 deg to +60 deg. The test conditions represent significant changes in blade loading and dimensionless frequency, and the range of interblade phase angle includes those values usually encountered in actual turbomachines. The measured pressure time histories over the airfoil chord were used to calculate the stability parameters of the system including the unsteady pitching moment coefficient and the aerodynamic damping parameter. For the range of parameters tested it was found that the interblade phase angle is the most important parameter affecting the stability of oscillating cascaded airfoils. The system was unstable for most positive values of σ over the entire range of loading and frequency. This was similar in behavior (but not in magnitude) to the predictions of available potential flow cascade theories and suppports the observation that blade stall need not be present for torsional “stalled” flutter to occur. System stability for negative values of σ was more dependent on loading and frequency and, conformed more closely with the observed behavior of stalled flutter. Specifically, for σ < 0 deg stability increased with frequency and decreased with loading. A preliminary evaluation of the pressure time histories shows that a second harmonic behavior renders the 1.2 percent chord station ineffective in contributing to the blade damping. Under these circumstances it is surmised that the induced damping is associated mainly with the first harmonic component of the pressure response at the 6.2 percent chord station.
Dependence of Soot Production on Fuel Blend Characteristics and Combustion Conditions
Authors: Blazowski W. S.
Published: October 2009

Liquid synthetic fuels derived from nonpetroleum resources will play a major role in meeting future national energy demands. In the case of gas turbine applications, it is known that the different properties of these fuels can result in substantially altered combustion performance. Most importantly, decreased fuel hydrogen content resulting from an increased aromatic content has been observed to result in increased exhaust smoke and particulates as well as greater flame luminosity. This paper contributes empirical information and insight which allows the greater soot formation tendencies of low hydrogen content fuels to be better understood. A small scale laboratory device which simulates the strongly backmixed conditions present in the primary zone of a gas turbine combustor is utilized. The Jet Stirred Combustor provides for very rapid mixing between a premixture of vaporized fuel and air and the combustion products within a 5.08 cm dia hemispherical reactor. Results to be presented are gaseous combustion product distributions, incipient soot limits, and soot production (mg/l) for a variety of fuels. The influences of combustor inlet temperature and reactor mass loading have been evaluated and the sooting characteristics of fuel blends have been studied. These results have been analyzed to develop useful correlations which are in general agreement with existing mechanistic concepts of the soot formation process.
Improvements in the Utilization of Gas Turbine Compression Plant
Authors: Huggett B. M. , Ingham D. R.
Published: October 2009

The paper reviews the technical developments and changes in philosophy currently underway in British Gas to improve the utilisation of existing and future gas compressor plants. These developments have two main objectives, first to improve the operation of all plants, with corresponding reductions in operating costs, and second to reduce capital investment in future plants by good design and accurate planning. The paper considers in some detail machinery selection including the possibility of a short-term peak operation of plant and the use of waste heat recovery schemes. Improvements in machinery operating efficiency are also reviewed with particular emphasis on performance testing, computer based health monitoring schemes and reliability investigations. The influence of the various technical developments in relation to the investment in new and standby plants is considered.
The Experimental Behavior of Premixed Flames in Tubes: The Effects of Diluent Gases
Authors: Odgers J. , White I. , Kretschmer D.
Published: October 2009

One of the problems facing gas turbine users is the proliferation of gaseous fuels which may be available. These are so many that a comprehensive rig/engine study would be far too costly to undertake. The present studies represent an attempt to quantify the behavior of such fuels, in a simple environment. Measurements of the rates of flame travel and the stability limits have been made for propane/oxygen mixtures diluted with nitrogen, carbon dioxide, helium or argon. The results have been used to forecast the laminar flame speed of mixtures, and rates of flame travel for the various mixtures have been correlated with groups representative of reaction rate and gas transport properties.
Improving Turbine Component Efficiency
Authors: Mach K. D.
Published: October 2009

The thermal efficiency of a gas turbine engine depends on the cycle pressure and temperature ratio and on the aerodynamic efficiencies of the gas path components. Maintaining and/or improving structural integrity and aerodynamic efficiency in this high pressure, high temperature environment is the preeminent problem of the turbine designer. High gas temperatures require at least some of the metal structure to be cooled, yet cooling air is a loss to the cycle and its consumption must be kept to a minimum. Research into cooling techniques and boundary layer behavior on airfoils and endwalls and into test procedures for obtaining heat transfer data are providing some of the answers the designer needs. Increased operating-pressures generate increased mechanical stresses. Finite element analyses and automated design procedures are proving to be powerful aids to the designer. Improving aerodynamic efficiency requires careful control of the flow in three dimensions, particularly in low aspect ratio machines. The first practical computation method for three-dimensional, viscous, transonic flows became available in late 1977 and has made this one of the most exciting areas of turbine technology. Additional gains in aerodynamic efficiency can be realized by controlling leakages, especially those over the rotor tip, by accounting for the transient interactions between rotor and stator; and by careful control of discharged coolant flow. This paper briefly describes the turbine cooling research conducted by the Air Force Aero Propulsion Laboratory and describes more extensively the AFAPL programs in turbine aerodynamics, including applications of three-dimensional flow analysis.
A Design Review of Ceramic Components for Turbine Engines
Authors: Coty P. J. , Lane A. D. , Lee J. B. , Meyer L. J.
Published: October 2009

This paper summarizes a program (AFML/APL Contract No. F33615-77-C-5171) to evaluate the application of ceramic materials in small, limited-life turbine engines. Advanced ceramics technology is employed in the program to achieve an affordable, reliable, high-performance capability for turbine engines in a missile application. The paper presents design and material considerations for ceramic rotor blades and stator vanes in addition to aerodynamic flow path analyses for ceramic components in high temperature environments. An iterative materials/design analysis was made with use of probabilistic design methods to predict the survivability of the ceramic components. Materials for both rotor blades and stator vanes were evaluated and selected based on mechanical and thermal stresses imposed by the optimum component design. A number of design concepts for the primary components are reviewed. These concepts include segmented-vane configurations and rotor airfoil shape and attachment schemes.
The Prediction of Steady, Circumferential Pressure and Temperature Distortions in Multistage Axial Flow Compressors
Authors: Mokelke H.
Published: October 2009

A small perturbation theory is presented for the prediction of the decay of steady circumferential pressure, temperature and velocity distortions in multistage axial flow compressors. The mathematical model which is employed replaces the blade rows of the compressor by actuator disks. A closed solution for the linearized equations describing the two-dimensional, inviscid and compressible flow between the disks is derived and appropriate matching conditions at the disks (assuming a quasi-steady blade response) are determined. An efficient calculation procedure is presented which allows the rapid computation of the distortion development through any compressor configuration, i.e., through any combination of rotors, stators and axial clearances including the core engine compression system. The theory can be applied to the mean section of the compressor or separately from stream surface to stream surface. Due to the assumption of a two-dimensional flow, however, it is restricted to purely circumferential distortions in compressors with sufficiently high hub-to-tip ratios where radial flow redistributions can be expected to be small. The validity of the small perturbation theory is demonstrated by comparing the theoretical results with experimental data. In addition, the theory is used to study the effect of Mach-number and flow rate on the decay of the distortions through two compressor configurations. Suggestions are made how to utilize the theory for the design of distortion-tolerant compressors.
Assessment of Hot Gas Clean-Up Systems and Turbine Erosion/Corrosion Problems in Pfbc Combined Cycle Systems
Authors: Stringer J. , Ehrlich S. , Slaughter W. W. , Dolbec A. C.
Published: October 2009

Alternative methods of producing electricity from coal while maintaining acceptable environmental standards are currently being examined in detail. One such method involves the fluidized bed combustion of coal at elevated pressure, using an acceptor in the fluidized bed to remove the sulfur. Steam is raised using heat exchangers within and above the bed, and the hot combustion gases are expanded through a gas turbine. A serious limitation on this system is the ability to reduce the particulate loading in the combustion gases to a level at which a gas turbine having acceptable life can be constructed. The turbine may be either a new design or a modification of a currently available engine, and palliatives include lowering the turbine inlet temperature, lowering the gas velocity through the turbine, and “hardening” the turbine by the selection of appropriate materials or claddings for the vanes and blades. In this paper, the various degradation processes are considered, with emphasis on erosion, and the probable limits of particulate loading in the gas stream are estimated. These estimates are discussed in relation to existing hot gas particulate removal systems, and directions for further study are suggested.
Low Frequency Gas Turbine Noise
Authors: Newman J. R. , McEwan K. I.
Published: October 2009

British Gas have experienced problems at some installations from low frequency turbine noise. The paper describes how the low frequency noise problems were investigated and then resolved by aerodynamic modifications and a silencer extension.
Steam Turbines for Cogeneration Power Plants
Authors: Oliker I.
Published: October 2009

Steam turbines for cogeneration plants may carry a combination of industrial, space heating, cooling and domestic hot water loads. These loads are hourly, weekly, and seasonally irregular and require turbines of special design to meet the load duration curve, while generating electric power. Design features and performance characteristics of one of the largest cogeneration turbine units for combined electric generation and district heat supply are presented. Different modes of operation of the cogeneration turbine under variable load conditions are discussed in conjunction with a heat load duration curve for urban heat supply. Problems associated with the retrofitting of existing condensing type turbines for cogeneration applications are identified.
Simulation of Whirl Interaction in Pinion-Gear Systems Supported on Oil Film Bearings
Authors: Hamad B. , Seireg A.
Published: October 2009

The pinion gear system is modeled as a coupled two-rotor problem in this study. Each rotor is centrally supported on two hydrodynamic bearings and the inertia and load interaction between the two rotors is considered throughout their whirl orbits. Numerical results are given to illustrate the effect of transmitted load on the whirl amplitudes and stability of balanced and unbalanced gears with different gear ratios.
Mean Velocity and Decay Characteristics of the Near and Far-Wake of a Compressor Rotor Blade of Moderate Loading
Authors: Ravindranath A. , Lakshminarayana B.
Published: October 2009

This paper reports the experimental study of the three-dimensional characteristics of the mean velocity in the wake of a moderately loaded compressor rotor blade. The measurements were taken with a three-sensor hot-wire probe rotating with the rotor. The wake was surveyed at several radial and axial stations. The loading was found to have substantial effect and this was reflected not only in the axial and tangential components, but also in the radial component. The radial velocities were found to be high very near the trailing-edge and this exhibits the characteristics prevalent in a trailing vortex system. The static pressures across the wake were measured using a direction insensitive spherical head static-stagnation pressure probe. The static pressure was found to be higher inside the wake. These and other measurements are reported and correlated in this paper.
Simplified Inelastic Analysis in Helical Coil Heat Exchanger Design
Authors: Richard C. E.
Published: October 2009

A simplified, inelastic analysis of helical coil tubing for high-temperature applications is described. Elastically calculated operating stresses are compared with inelastic estimates of allowable cyclic creep/fatigue stresses. The technique of simplifying and analyzing the operating cycles to determine acceptable creep damage levels has general application. The allowable stresses represent the greatest uncertainty in the method, and tests are required to improve their accuracy. A method of utilizing short-time test data to determine allowable stresses for reactor lifetimes of 30 to 40 years is proposed.
Fiber Reinforced Metals in Turbine Blades
Authors: Larsson L. O. K. , Warren R.
Published: October 2009

Composites of tungsten wire reinforced stainless steel were prepared by a specially developed fabrication method based on hot isostatic pressing. This composite system was chosen as a convenient model material. Its mechanical properties were investigated to provide a basis for the evaluation of the potential advantages and possible difficulties to be expected in the application of such material to turbine blades. Results obtained so far suggest that composites based on W-alloy wires show considerable promise as blade materials for very high service temperatures. Further research effort is required, particularly on fiber/matrix interaction, thermal fatigue and to optimize the properties of the reinforcement wire.
Plasma-Spray Coating Processes: Physico-Mathematical Characterization
Authors: Gal-Or B.
Published: October 2009

Approximate characterization of the complicated dynamics of plasma-spray coating processes may be useful in obtaining optimal coatings. The usual industrial method of obtaining such a characterization by experimental trial-and-error procedures may be more time-wasting and costly than a combined procedure of analysis and trial-and-error. This paper describes such an approximate analysis and presents the results in a simple graphical form. Thus, by using a few simplified differential equations which describe the fluid dynamics, temperature and velocity distributions as well as the degree of evaporation of the injected powder in the plasma jet, we illustrate our method for the specific case of spraying molybdenum particles in argon as the carrier gas. The results indicate the various limitations associated with major operating variables such as particle size, relative mass flow rates of gas and particles, plasma temperatures, and distances from the plasma gun. Evaporation losses of the powder are given in Fig. 7.
An Analysis of Three-Dimensional Flow in a Centrifugal Compressor Impeller
Authors: Bosman C.
Published: October 2009

This paper presents detailed results of the three-dimensional kinematic flow detail in a centrifugal compressor impeller of common form with inducer and straight radial blade tip sections. The calculation method, which is inviscid and is reported elsewhere, shows the development of a passage vortex in a sense counter to that of blade rotation, initiated in the inducer and disappearing as the flow becomes radial. This vortex unloads the blade shroud sections and combined with slip at the blade tips, produces a jetwake velocity distribution at the blade passage exit. General features of the calculation are at variance with two-dimensional calculations but are in agreement with the experimental results of other workers.
Application of Viscous Analyses to the Design of Jet Exhaust Powered Lift Installations
Authors: Tjonneland E. , Birch S. F.
Published: October 2009

The application of available numerical methods to the design of powered lift installations is reviewed. For this application, where strong coupling exists between the jet exhaust and the external flow, a three-dimensional viscous analysis tool is needed. The task of selecting a suitable analysis procedure is first outlined, with particular emphasis on the need for careful coordination of the various elements of the task. Problems and progress in the development of turbulence models are then discussed, and some selected three-dimensional calculations are presented to illustrate recent progress. Finally, a numerical procedure, currently under development for a particular powered lift application, is briefly described.
A Blade-to-Blade Solution of the Flow in a Centrifugal Compressor Impeller with Splitters
Authors: Goulas A.
Published: October 2009

The matrix through flow analysis is used to predict the blade-to-blade flow in a centrifugal compressor impeller which contains splitters (half vanes). The presence of solid boundaries in the flow field and the stagnation points associated with it are treated by assuming that the flow around the stagnation point is isentropic. This removes the instability which the matrix through flow method suffers when stagnation points are encountered within the flow field. The splitters in the present work have the same profile with the full blades. Three different geometries are tested. In the first, the leading edge is 3 mm from the eye, the next is 6 mm, and the third has the leading edge at the exit of the inducer. The calculations show that the differences shown between the three cases are linked with different circumferential components of velocity. The geometry, therefore, of the leading edge is of basic importance in the development of the velocity profiles inside the different channels of the impeller. It is also shown that the distance between the eye of the impeller and the leading edge of the splitter does not affect the flow greatly as long as the leading edge is within the axial part of the impeller. The presence of splitters in general is shown to reduce the width of the suction side boundary layer.
Interferometrically Measured Aerodynamic Forces on a Vibrating Turbine Blade Group
Authors: Kovats Z.
Published: October 2009

The instantaneous aerodynamic force and force center during a vibration cycle were determined from interferometrically measured pressure distributions around the leading blade of a low pressure turbine blade group vibrating in the tangential, axial or twist modes. The corresponding reduced frequencies were 0.0796, 0.1088 and 0.1312, and the inlet flow Mach number was 0.59 in all tests. The energy exchange per vibration cycle between the air flow and the leading blade of a group, and the lift and drag dynamic loops were determined for each of the three vibration modes. The periodic aerodynamic force coefficients were nearly sinusoidal for the axial and torsional modes but not for the tangential mode. At large negative flow incidence, the four-blade group tested is strongly unstable in the twist mode, weakly unstable in the axial mode, and strongly stable in the tangential mode. The experimental results can be used to investigate the validity of analytical predictions of the aerodynamic forces on a vibrating low pressure blade group.
The Prediction of Sauter Mean Diameter for Gas Turbine Fuel Nozzles of Different Types
Authors: Simmons H. C.
Published: October 2009

Reviewing the more important published equations for predicting SMD for various types of fuel nozzles it is pointed out that there is no universal or common approach to cover different nozzle designs. In particular there is no effort to bridge the gap between pressure-atomizers and air-atomizers, especially the air-assisted simplex nozzle. Furthermore many of the equations provide no basis for estimating the effect of dimensions which is essential in modeling. An equation is presented, based on both new and published data, which satisfies these objections, and is shown to be related to previous methods. Suggestions are made with regard to the choice of constants in the prediction equation so as to represent fairly the present state of the art.
Laboratory Combustibility Testing of Solid Fuel
Authors: Winegartner E. C. , Lin C. J.
Published: October 2009

A laboratory furnace having a controlled wall temperature is used to measure the combustibility of coal and other solid fuels. Operation at wall temperatures of 1260–1370°C (2300°–2500° F) permits determination of percent carbon burnout as a function of residence time and excess oxygen under furnace conditions representative of those encountered in large boilers. Operation at decreasing wall temperatures provides information on flame stability under conditions approaching those encountered under low load conditions in operating boilers. Firing rates are generally in the range of 11.7–29.3 KWt (40–100k BTU/hr) permitting testing of 100–150 kg (200–300 lb.) samples which can reasonably be obtained by core drilling or from small pilot units.
Some Results of the Wetting and Adherence of Synthetic Coal Ash Droplets on Steel
Authors: Moza A. K. , Austin L. G. , Tressler R. E.
Published: October 2009

As part of a study of slagging in boiler furnaces the sticking temperature, strength of adhesion and contact angle of molten mineral glass drops on various oxidized steel substrates have been investigated. The freezing of the interface between the drop and the metal substrate occurs in milliseconds and in this time a bond is formed between the glass and the oxide coating on the steel. Mineral compositions of low melting point which have reduced liquidus temperatures when iron is dissolved from the surface appear to give the lowest sticking temperatures. Stainless steels which were not heavily oxidized gave low strengths of adhesion. Pyrrhotite formed from melting of pyrite wetted the oxidized surfaces well and gave low sticking temperatures.
Composition and Microstructure of a Furnace Ash Deposit from a Coal-Fired Utility Boiler
Authors: Fessler R. R. , Skidmore A. J. , Hazard H. R. , Dimmer J. P.
Published: October 2009

An exploratory study of the structure and composition of furnace-ash deposits was carried out using optical metallography, electron microprobe analysis, scanning electron microscopy, and energy-dispersive X-ray analysis. The results of these analyses were supplemented by studies of particulate melting temperatures using hot-stage microscopy to measure melting temperatures, and energy-dispersive X-ray analyses to measure composition of melted particles. It was found that the general structure of the ash deposit was a matrix of glassy, spherical particles having a wide range of compositions in which unfused particles containing iron oxide and calcium oxide were dispersed. At the imprint of the tube surface a considerable concentration of calcium, sulfur, and iron was found. Near the fused outer surface of the deposit, the glassy materials had melted into a porous, glassy slag containing spherical globules of iron oxide combined with other materials. There were no systematic compositional gradients from the tube surface to the fused outer layer except for the sulfur layer found only at the tube surface. However, there were significant differences in composition from particle to particle, and these differences were similar to those found in the coal mineral matter as isolated by low-temperature ashing. Single particles of low-temperature ash were found having low fusion temperatures, in the range of fusion temperatures for particles in furnace ash. Thus, the glassy spheres found in furnace deposits could originate from single coal particles, without the need for interactions among coal particles or ash particles.
Waste Heat Disposal to Air with Mechanical and Natural Draft—Some Analytical Design Considerations
Authors: Montakhab Ali
Published: October 2009

There is a growing acceptance of the future necessity of dry and wet/dry cooling tower systems for large power stations in spite of their economic penalty compared with once-through cooling, cooling ponds, and evaporative cooling towers. If technological improvements succeed in reducing the current costs of dry cooling towers, their future applications will be accelerated. The main objective of this work is to quantify the factors that reduce the overall size and cost of the tower and the associated heat transfer system and to provide a basis for establishing the conditions that result in dry cooling tower cost reductions. As a first-step, the design equations for forced-and natural-draft dry cooling towers are derived in close form to give explicit relations for salient design variables. Subsequently, these equations are used to establish a set of influence coefficients for quantifying the effects of various key design variables on the design of forced- and natural-draft cooling towers.
Status of Centrifugal Impeller Internal Aerodynamics—Part I: Inviscid Flow Prediction Methods
Authors: Adler D.
Published: October 2009

Recent developments in inviscid prediction methods of internal flow fields of centrifugal impellers and related flows are critically reviewed. The overall picture which emerges provides the reader with a state-of-the-art perspective on the subject. Restricting simplifying assumptions of the various methods are identified to stimulate future research. Topics included in this review are: two-dimensional subsonic and transonic inviscid flows as well as three-dimensional inviscid flows.
Full-Coverage Film Cooling—Part II: Heat Transfer Data and Numerical Simulation
Authors: Crawford M. E. , Kays W. M. , Moffat R. J.
Published: October 2009

Experimental research into heat transfer from full-coverage film-cooled surfaces with three injection geometries was described in Part I. This part has two objectives. The first is to present a simple numerical procedure for simulation of heat transfer with full-coverage film cooling. The second objective is to present some of the Stanton number data that was used in Part I of the paper. The data chosen for presentation are the low-Reynolds number, heated-starting-length data for the three injection geometries with five-diameter hole spacing. Sample data sets with high blowing ratio and with ten-diameter hole spacing are also presented. The numerical procedure has been successfully applied to the Stanton number data sets.
A Numerical Model for Stirling Cycle Machines
Authors: Berchowitz D. M. , Urieli I. , Rallis C. J.
Published: October 2009

The further development of a model to accurately simulate the performance and detailed behavior of Stirling cycle machines is described. The transport equation set (which describe the working gas) is derived in both the so-called integral and differential forms. Only the integral equation set is solved for the simulation. The differential equation set is used to investigate the structure of individual terms in the integral equation set. This procedure allows these terms to be more accurately understood and, hence, modeled. The energy equation includes kinetic energy and dissipation terms while the momentum equation includes the effects of working gas acceleration and viscous friction. Heat leakage and longitudinal conduction in the machine walls are accounted for and due regard is taken of the working gas instantaneous properties. The Reynolds analogy is used to calculate the local heat transfer coefficients.
Stability of a ZrO2(Y2O3) Thermal Barrier Coating in Turbine Fuel with Contaminants
Authors: Singhal S. C. , Bratton R. J.
Published: October 2009

Corrosion behavior of recently developed plasma sprayed duplex thermal barrier coating systems, consisting of Udimet-500 alloy metal substrate, MCrAlY (M = Ni or Ni/Co) bond coat and ZrO2 stabilized with 12 wt percent Y2O3 overcoat, has been evaluated in environments now used or anticipated in utility turbines burning liquid fuels. The base fuel, GT-2, was doped with desired concentrations of sodium, vanadium and sulfur, and burned in a gas turbine simulator which contained the coated, air-cooled specimens. The coatings were found to behave well when exposed to combustion gases obtained by burning clean GT-2 fuel oil and that containing 1 ppm Na. However in the presence of vanadium in the fuel, the ZrO2·12 wt percent Y2O3 oxide coating showed severe cracking, chipping and spalling. Possible causes for such oxide coating degradation are discussed. This work shows that the thermal barrier coating concept is feasible for utility turbines; but further coating development, specifically for utility turbines burning residual fuels, is required.
Fuel Treatment Chemical Additives Progress Report
Authors: Bischof A. E.
Published: October 2009

A detailed discussion of fuel quality as related to associated fuel use problems is presented. The generic chemical solution to the problems is covered with emphasis on the correction of system mechanical and instrumental malfunctions. Three case histories concerning high temperature corrosion, combustion efficiency and deposit accumulation are explored.
On Formation of a Homogeneous Two-Phase Foam Flow
Authors: Fabris G. , Chow J. C. F. , Dunn P. F.
Published: October 2009

This paper presents the results of a series of experiments conducted to evaluate the fluid mechanical performance of various two-phase LMMHD mixer designs. The results from both flow visualization studies of the local two-phase flows downstream from various mixer-element configurations and local measurements performed to characterize these flows are presented. A conceptual LMMHD mixer design is described that insures the generation of small bubbles, prevents the formation of gas slugs and separated regions, and favors the stabilization of a homogeneous foam flow.
Characteristics of Exhaust Gas Pulsation of Constant Pressure Turbo-Charged Diesel Engines
Authors: Azuma T. , Tokunaga Y. , Yura T.
Published: October 2009

The constant pressure turbo-charge system has now been increasingly adopted for marine diesel engines because of its higher thermal efficiency in the range of higher mean effective pressure. However, it seems that there has been no paper published on the exhaust gas pulsation of this sytem. In this study, a gas flow model of the constant pressure turbo-charged diesel engines was assumed as a basic and fundamental one, and an investigation was made of it. As a result, some characteristics of the exhaust gas pulsation of this system have been clarified and a mathematical simulation system has been established. It must be emphasized that the filling and emptying method which neglects wave propagation cannot simulate the pulsation, although it can simulate the average exhaust gas pressure and temperature of this system.