bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of a Hybrid Computer in the Optimization of Gas Turbine Control Parameters
Authors: Saravanamuttoo H. I. H. , MacIsaac B. D.
Published: November 2010

This paper discusses the hybrid computer simulation of a single-spool turbojet engine. The problem is approached from the viewpoint of engineering thermodynamics, using the normal compressor and turbine characteristics. This was found to yield an extremely flexible simulation capable of operation over the entire running range. The simulation was used to investigate methods of improving the thrust response and it was found that a detailed insight into the engine dynamics permitted a significant improvement in thrust response.
Evaluation of Additives for Prevention of High Temperature Corrosion of Superalloys in Gas Turbines
Authors: Lee S. Y. , Young W. E. , Vermes G.
Published: November 2010

A number of commercially available chemical additives for utilization in modern high temperature gas turbines were evaluated for their corrosion and deposit inhibiting characteristics. The evaluation was made in pressurized passages which simulate conditions of operating gas turbines. Initial screening tests of 10 hr each were made with a contaminant level of 50 ppm vanadium, and promising additives were further tested for times up to 300 hr at the more realistic contaminant level of a No. 3 GT fuel. Characteristics of the deposits were studied with x-ray diffraction and ash fusion tests. Corrosion rates for various alloys tested with treated fuel were measured and compared to test results obtained with untreated fuel. Conclusions were drawn as to the type of elements most effective in reducing corrosion caused by combinations of vanadium and sodium. The role of elements in preventing deposit buildup is also assessed.
Sodium Sulphate Formation and Deposition in Marine Gas Turbines
Authors: Hanby V. I.
Published: November 2010

The rate of formation of gaseous sodium sulphate from sodium chloride and the combustion of a sulphur-bearing fuel has been investigated in a controlled mixing history combustor. The reaction was studied in the residence time range 0–16 millisec to simulate conditions resembling those in a gas turbine combustion chamber. The results show that under the conditions investigated, gas temperature was the most significant variable affecting the reaction rate. Gas phase formation of sodium sulphate proceeds too slowly to contribute to sulphatic corrosion in the short residence times which occur in gas turbine combustion chambers. The results obtained, in conjunction with predictions of salt particle behavior in the gas turbine engine indicate that the deposition process on turbine blades occurs via passage of transient high concentrations of particles through the engine.
Direct Coal Fired MHD Power Generation
Authors: Dicks J. B. , Crawford L. W. , Kornstett K. W.
Published: November 2010

This paper describes the results of the first experiments in the operation of a magnetohydrodynamic (MHD) generator on coal at simulated central power conditions. The microscopic examination of the generator after one hour of operation shows no damage to any of the electrode or insulator structures. The relations between these experiments and the full-scale central power direct coal fired plant are discussed along with the problems that have been solved and those that still remain to be solved before this technology can be put into application.
The Periodic Method for Testing Compact Heat Exchanger Surfaces
Authors: Stang J. H. , Bush J. E.
Published: November 2010

The regular periodic method for testing the heat transfer performance of heat exchanger cores is studied in detail. This method, which has received very limited attention in the past, has certain advantages over the more conventional steady-state technique. It is shown to be useful especially in testing matrix surfaces. A theoretical analysis is performed, forming the basis for the periodic method. Directions for use in the range 0.2 < Ntu < 50, an uncertainty analysis, and test results for 2.6 < Ntu < 36.6 are included. It is concluded that the periodic method has the major advantages of: a wide Ntu range, easily generated experimental temperature waves, and the accuracy of an integral technique.
Steam Turbine Driven Circulators for High-Temperature Gas-Cooled Reactors—Part I: Design
Authors: Yampolsky J. , Cavallaro L. , Thurston G. C. , Nichols M. K.
Published: November 2010

The High-Temperature Gas-Cooled reactor is characterized by integration of the primary coolant circuit and components within a Prestressed Concrete Pressure Vessel. This concept requires particular features and assurance in the circulators that are used to circulate the primary coolant fluid. Each circulator employs a single-stage axial compressor driven by a single-stage turbine which is in series with the main steam turbogenerator. The circulator is lubricated by water and is capable of variable speed operation. An extensive design and development program was carried out to provide a family of circulators for a range of reactor sizes. This paper considers the design features of the series steam turbine driven helium circulator and the basis for the adopted design solutions. Part II of this paper considers the experimental development program.
Calculated Design Data for the Multiple-Disk Pump Using Incompressible Fluid
Authors: Crawford M. E. , Rice W.
Published: November 2010

Earlier analyses of the laminar radically outward flow of Newtonian incompressible fluid between parallel corotating disks have been used to calculate the performance of multiple-disk pumps using such flow passages as the rotor. Such pumps are characterized by certain dimensionless parameters and a large number of computerized calculations have enabled preparation of pump performance maps for pumps idealized as having no losses external to the rotor; these maps show the quantitative dependence of pump efficiency, pressure change and required power on the pump geometry, speed, and on fluid properties. Conventional loss information for the pump entrance and diffuser flows, and conventional bearing, seal, and “disk friction” loss information, must be applied in the design process to provide prediction of actual pump performance and comparison with conventional pumps. The design information is also applicable to low-pressure gas blowers.
Turbulence and Unsteadiness Measurements Downstream of a Moving Blade Row
Authors: Evans R. L.
Published: November 2010

Turbulence and unsteadiness levels downstream of an axial-flow compressor rotor have been measured using an ensemble-averaging technique. Free-stream turbulence levels are lowest near the compressor design-point, and increase with decreasing flow coefficient as the compressor nears the stalled condition. The unsteady stator incidence angles have been found to have a peak-to-peak variation of between 12 deg and 15 deg for all flow coefficients tested. These observations have been confirmed qualitatively by hot-wire-anemometer spectral measurements.
Calculation Procedures for Potential and Viscous Flow Solutions for Engine Inlets
Authors: Albers J. A. , Stockman N. O.
Published: November 2010

The method and basic elements of computer solutions for both potential flow and viscous flow calculations for engine inlets are described. The procedure is applicable to subsonic conventional (CTOL), short-haul (STOL), and vertical takeoff (VTOL) aircraft engine nacelles operating in a compressible viscous flow. The calculated results compare well with measured surface pressure distributions for a number of model inlets. The paper discusses the uses of the program in both the design and analysis of engine inlets, with several examples given for VTOL lift fans, acoustic splitters, and for STOL engine nacelles. Several test support applications are also given.
Acoustic Emission Measurements During Electron Beam Welding of Nickel-Base Alloys
Authors: Dickhaut E. , Eisenbla¨tter J.
Published: November 2010

During EB welding of nickel-base superalloys flaws may occur under unfavorable conditions. In welds of Waspaloy “Cameron” flaws appeared in the heat-affected zone, while flaws in the weld seam were observed in the case of Inconel 713 “Nimocast.” The flaws in Waspaloy could not be detected by conventional NDT methods because of their position at the root of the weld. Therefore, for direct observation of flaw formation in these alloys, acoustic emission measurements were made during EB welding of these alloys. Two different types of acoustic emission were found. In nickel-base superalloys and in austenitic steel background noise occurs as so-called burst signals which follow one another at short time intervals; these signals correlate exactly with markings (grooves) on the surface of the weld seam. This type of acoustic emission depends on the local heat transfer (beam current per unit time and area). Apparently this background noise is caused by weld solidification. Flaw formation, on the other hand, is indicated by single burst signals having a much higher amplitude than those due to solidification. In the case of Waspaloy this second type of acoustic emission was observed only at fairly high speeds of welding (i.e., higher than 25 mm/sec). This result is consistent with evaluations of micrographs.
Untwist of Rotating Blades
Authors: Ohtsuka M.
Published: November 2010

This paper deals with the deformation and the stress of an axial flow compressor rotor blade under the loading of centrifugal forces. Coupled deformation of extension, bending, torsion and transverse shear of a pretwisted curved bar with arbitrary cross section is considered. Governing equations derived by means of the principle of virtual work are solved numerically by finite difference method. The warping functions used in the analysis were obtained by the use of finite element method. Measurement of the untwist angles and the stresses were carried out for the verification of the numerical analysis and they were found to be in good agreement.
Experiments With a Model Free Rotating Vaneless Diffuser
Authors: Rodgers C. , Mnew H.
Published: November 2010

Experimental testing of a model free-rotating vaneless diffuser, for application to high pressure ratio single-stage centrifugal compressors, was conducted to determine diffuser performance under braked and free rotating conditions at entry Mach numbers up to unity. The experimental test rig comprised a swirl generating nozzle upstream of the model vaneless diffuser rotor with an outer-to-inner diameter ratio of 1.3. Additional downstream diffusion was completed with stationary vaneless and vaned diffuser inserts. A significant improvement in diffuser performance was achieved under free-rotating conditions even though large wakes generated by upstream stationary swirl nozzles were present. Overall static pressure recovery for the complete diffusion system increased approximately 20 percent at free-rotating conditions corresponding to a tangential velocity ratio (diffuser rotor/incident stream) of 0.43.
The Potential Impact of Multiplane-Multispeed Balancing on Gas Turbine Production and Overhaul Costs
Authors: Badgley R. H.
Published: November 2010

This paper describes recent advances in the development of a practical, cost-effective method for balancing, in a single step, a final shaft-bearing assembly simultaneously in a number of planes and at a number of speeds. This method is capable of overcoming assembly-introduced unbalance, and will permit rotor operation through critical speeds in which component elastic axis bending occurs. Detailed results of test efforts are presented in order to illustrate the effectiveness of the method. The procedure by which the method may be applied to gas turbine engine shafts, and the potential cost advantages expected to accrue therefrom, are described and discussed.
The Leakage Thru Straight and Slant Labyrinths and Honeycomb Seals
Authors: Meyer C. A. , Lowrie J. A.
Published: November 2010

Leakage tests have been run over a wide range of pressure ratios and clearances for several types of seals. The results of tests of labyrinth seals show some important differences compared to previous theory. The discharge coefficient of a single seal has been found to jump from 0.62 to 0.78 when a second seal is added downstream. This effect depends on the clearance, pitch, and the pressure ratio across the seal. This phenomena has not been considered in past theories which assumed fixed seal discharge coefficients independent of the seal position and its pressure ratio in the Labyrinth. The test results are presented in a form which is easier to use than those based on the more complicated previous theory.
A Note on Obtaining Temperatures From Thermocouple EMF Measurements
Authors: Benedict R. P. , Godett T. M.
Published: November 2010

Six methods are given for converting to temperatures the measured values of emf generated by thermocouples. Two are based on the use of thermocouple reference tables alone. Two are based on the use of calibration data alone. And two are based on a combination of calibration data with reference table functions. It is shown that one method is preferred if graphical presentation is required, while another is clearly the best for computer conversions of thermocouple emf to temperatures.
Effect of Rapid Steam Take-Off on Natural Circulation and Water Level in Boilers
Authors: Poon K. L.
Published: November 2010

A theory is presented for predicting the transient behavior of bubbles in the downcomer and riser loop. It is found that a sudden drop in boiler pressure could seriously reduce the circulation velocity and this is attributed to steam formation in the downcomer tube. The reduction of the circulation velocity tends to prolong existence of individual bubbles in the water phase and therefore increases the water level swell. Transient behavior of circulation velocity in the riser, and water level responses in the steam drum were measured in a two-tube experimental boiler following a step increase in steam control-valve opening for various boiler pressures.
Experimental Results of Full Scale Air-Cooled Turbine Tests
Authors: Nouse H. , Yamamoto A. , Yoshida T. , Nishimura H. , Takahara K. , Torisaki T. , Matsuki M.
Published: November 2010

In order to investigate several problems associated with the turbine cooling, an air-cooled two-stage axial flow turbine for an aircraft engine application was designed. Aerodynamic characteristics of the two-stage turbine without coolants were obtained first from the cold air turbine tests, and predictions of the turbine performance with supplying of coolants were made using the test results. Following these experiments, cooling tests of the first stage turbine were conducted in the range of turbine inlet gas temperatures lower than 1360 K by the another test apparatus. The descriptions of the turbine and the two test apparatus and the experimental results of the two test turbines are presented. The performance prediction, coolant effects and Reynolds number effect on the turbine performance are also described.
The Shore Testing of Marine Gas Turbine Ship Propulsion Machinery
Authors: O’Hara D.
Published: November 2010

The paper seeks to clarify the case for the shore testing of a set of ship’s propulsion machinery and argues it to be particularly pressing where gas turbines are employed. The Shore Test Facility built for the Royal Navy’s Command Cruiser is described and the progress with testing covered briefly. The benefits of this particular installation are shown to be significant, such that a large number of improvements can be incorporated in the design prior to installation in the ship and at a substantial cost saving. The limitations of shore testing are also mentioned.
Surge and Rotating Stall in Axial Flow Compressors—Part II: Experimental Results and Comparison With Theory
Authors: Greitzer E. M.
Published: November 2010

This paper reports an experimental study of axial compressor surge and rotating stall. The experiments were carried out using a three stage axial flow compressor. With the experimental facility the physical parameters of the compression system could be independently varied so that their influence on the transient system behavior can be clearly seen. In addition, a new data analysis procedure has been developed, using a plenum mass balance, which enables the instantaneous compressor mass flow to be accurately calculated. This information is coupled to the unsteady pressure measurements to provide the first detailed quantitative picture of instantaneous compressor operation during both surge and rotating stall transients. The experimental results are compared to a theoretical model of the transient system response. The theoretical criterion for predicting which mode of compression system instability, rotating stall or surge, will occur is in good accord with the data. The basic scaling concepts that have been developed for relating transient data at different corrected speeds and geometrical parameters are also verified. Finally, the model is shown to provide an adequate quantitative description of the motion of the compression system operating point during the transients that occur subsequent to the onset of axial compressor stall.
Combustion Generated Noise in Gas Turbine Combustors
Authors: Strahle W. C. , Shivashankara B. N.
Published: November 2010

Experiments are conducted for the noise power and spectra emitted from a gas turbine combustor can exhausting to the atmosphere. The theory of combustion noise is applied to the results to determine the noise generating capability of the flame in the absence of reflecting can surfaces. The results show that for a fixed fuel (JP-4) the noise output is independent of fuel/air ratio for well stabilized can-type flames and heavily dependent on airflow while the spectra are dominated by the can acoustics, primarily through sound absorption by the liner. In an installed configuration the noise output depends heavily on the enclosure acoustics. For well stabilized can-type flames the equivalent unenclosed flame radiates with a thermoacoustic efficiency near 5 × 10−6, for air-flows of the magnitude used in this program. Scaling rules are presented for installed configurations.
Supersonic Compressor Cascades—An Analysis of the Entrance Region Flow Field Containing Detached Shock Waves
Authors: York R. E. , Woodard H. S.
Published: November 2010

When the incoming air flow to a supersonic compressor rotor or cascade has a subsonic axial velocity component, a system of shock and Mach waves originates in the blade leading-edge region, propagates upstream of successive blades, and alters the incident flow conditions. The continuity constraint establishes a unique relationship between the incident Mach number and air flow angle. The shocks are detached and curved with blunt leading edged blades thereby violating the assumptions inherent in the classical simple wave analysis of this flow induction process. The current work employs detached shock models and a rotational flow analysis by the method of characteristics to investigate the effects of airfoil leading edge radius and cascade solidity on the unique incidence values and entrance region total pressure losses. The calculated results are compared to simple wave theory for the entrance region and it is shown that the simple wave assumptions lead to appreciable errors when detached shocks are present in the flow field.
Ground Vortex–Limit to Engine/Reverser Operation
Authors: Motycka D. L.
Published: November 2010

It has been commonly accepted that engine stalls during reverser operation are caused by the temperature distortion created by reingested exhaust gasses. Recent studies have shown that compressors respond to instantaneous inlet distortions of a time duration on the order of one engine revolution. This paper describes the results of a test of a high bypass ratio engine during reverse thrust operation which revealed, through the use of high response temperature and pressure measurement, that instantaneous distortions caused by an induced ground vortex were the cause of engine stalls.
A One-Dimensional Variable Area Computer Simulation of Combustion in a Divided Chamber, Stratified Charge Engine
Authors: Boni A. A. , Chapman M. , Schneyer G. P.
Published: November 2010

A numerical simulation model of a divided chamber, stratified charge engine has been developed. The conservation equations of fluid mechanics, coupled to a single, global chemical reaction model have been solved by use of a generalized Eulerian-Lagrangian numerical technique for a one-dimensional, variable-area combustion volume. The simulation results in a prediction of the flame propagation dynamics which leads to temperatures, pressures, and species concentrations as functions of spatial location, time, and the various engine design parameters such as rpm and fuel/air ratio. The results indicate that both broad, turbulent flame fronts as well as detonations can occur, depending upon the rate of the oxidation reaction and the rate of heat release. The technique should be useful for calculating concentrations of pollutants as well as for investigating various design options such as fuel/air ratio and stratification function on pollution level and engine performance.
Corner Crack at the Bore of a Rotating Disk
Authors: Kobayashi A. S. , Polvanich N. , Emery A. F. , Love W. J.
Published: November 2010

Stress intensity factors of corner cracks at the bore of a rotating disk are estimated from the stress intensity factor of a quarter-elliptical crack in a quarter infinite solid and pressurized by the hoop stress. Curvature effect of the bore is incorporated through a curvature correction factor derived from the stress intensity factors of a single edge-cracked bore in a large plate and a single edge-cracked semi-infinite plate. Stress intensity factors for quarter-elliptical cracks with crack aspect ratios of b/a = 0.2, 0.4, and 0.98 at crack depths of b/Ri = 0.1, 0.3 and 1.0 in a rotating disk with R0/Ri = 8 are determined. Application of the developed procedure to corner crack problems at a through-bolt hole is indicated.
An Analysis of Elevated Temperature Fatigue and Creep Crack Growth
Authors: Do¨ner M.
Published: November 2010

Existing crack growth laws which consider time and temperature effects are examined. Based on phenomenological observations, as well as mechanistic considerations, one of these laws is modified in order to provide an improved, universal elevated temperature crack growth law. It is assumed that there are essentially three processes through which crack growth rates are affected: decrease in strength and modulus with temperature, oxidation damage at the crack tip and creep damage at the crack tip. The rate controlling mechanism(s) which may be associated with each of these processes are discussed. The type of experiments which are needed for the determination of material constant(s) that describe the contribution from each process are outlined. The modified crack growth law, when applied to publish data on HS-188 alloy, results in a prediction of the crack growth rates within a factor of 2.5, in the temperature range of 873–1144 K and at cycle frequencies ranging from 0.01 to 10 Hz.
Stall Margin Improvement by Casing Treatment—Its Mechanism and Effectiveness
Authors: Takata H. , Tsukuda Y.
Published: November 2010

Experiments on the effect of casing treatment were carried out using low-speed axial-flow compressors. Results on the overall compressor performance and on the flow through the blade row as well as the flow within the treatment slots are presented. Then, based on the experiments, a possible mechanism of the stall margin improvement is suggested.
Calculation of the Quasi Three-Dimensional Flow in a Turbomachine Blade Row
Authors: Veuillot Jean-Pierre
Published: November 2010

The equations of the through flow are obtained by an asymptotic theory valid when the blade pitch is small. An iterative method determines the meridian stream function, the circulation, and the density. The various equations are discretized in an orthogonal mesh and solved by classical finite difference techniques. The calculation of the steady transonic blade-to-blade flow is achieved by a time marching method using the MacCormack scheme. The space discretization is obtained either by a finite difference approach or by a finite volume approach. Numerical applications are presented.
A Simple Gas Turbine Combustor NOx Correlation Including the Effect of Vitiated Air
Authors: Sullivan D. A.
Published: November 2010

A set of parametric laboratory tests are used to develop a simple NOx correlation. The correlation is then compared with over 100 data points from various gas turbines operating on liquid and gaseous fuels. The correlation agrees well with constant speed simple cycle and regenerative cycle NOx data. The effect of vitiated air on NOx emissions is also determined from full scale laboratory tests and machine data. The NOx correlation with vitiated air is used to demonstrate the NOx emissions from two combustors operated in series with a variable fuel flow split between them. The nonlinear effect of fuel-to-air ratio on NOx production is shown to be responsible for the NOx reduction which occurs when two combustors are operated in series as opposed to single combustor operation.
A Flow Model for Centrifugal Compressor Rotors
Authors: Balje O. E.
Published: November 2010

A study of the presently available information on flow phenomena in curved ducts and in the flow passage of rotating channels shows that the flow distribution postulated by potential flow arguments occurs only in the initial portion of the channel. The production of turbulent kinetic energy on the concave side and pressure side of the channel in conjunction with stratification tendencies causes the flow distribution to become more uniform in the midsection of the channel and may initiate the generation of a comparatively large wake at the channel exit. These phenomena can be expressed by the Richardson number and a loading parameter which then become significant similarity parameters for the flow development in a rotating channel. The presently available information is insufficient to formulate precise relations for the influence of the Richardson number over the range encountered in typical centrifugal rotors. Thus only tentative values can be offered. More theoretical and experimental studies will be required to derive more exact interrelations.
The Effects of Free-Stream Turbulence Intensity and Velocity Distribution on Heat Transfer to Curved Surfaces
Authors: Brown A. , Burton R. C.
Published: November 2010

This paper describes a novel method for measuring the local heat-transfer distribution over a curved surface. The effect of free-stream turbulence intensity, ranging in value from 0.016 to 0.092, on local heat transfer is investigated for a range of Reynolds numbers from 2.0 × 105 to 7.7 × 105. The geometry of the rig was modified to consider three free-stream velocity distributions covering distributions currently in use on suction surfaces of turbine blades. The results are compared with other workers’ experimental results and with available prediction techniques for heat transfer in laminar and turbulent boundary layers. Special attention is paid to the region of boundary-layer transition.
Structural Designing With Ceramic Materials
Authors: Duckworth W. , Bansal G.
Published: November 2010

A central problem in attempting to use ceramic materials in demanding structural applications is uncertainty about the stresses to which they can be safely subjected. A ceramic rarely, if ever, exhibits a characteristic failure stress. This stress depends on the nature and distribution of microscopic flaws that intensify stress locally, and fracture initiates at a single “worst” flaw when Griffith’s criterion for crack instability is met. Within the basic framework, theories are available for treating effects of time, size, and stress distribution on failure stress. This paper reviews these theories, and discusses their use in specifying limiting stresses in designing structural members.
Boundary-Layer Development on an Axial-Flow Compressor Stator Blade
Authors: Evans R. L.
Published: November 2010

The boundary layer on an axial-flow compressor stator blade has been measured using an ensemble-averaging technique. Although the mean velocity profiles appear to indicate fully developed turbulent flow, ensemble-averaged instantaneous profiles show the boundary layer to be highly unsteady and transitional over much of the blade chord. At a given chordwise position, variations in boundary-layer thickness with time of up to 150 percent were recorded. When compared to boundary-layer development on a similar blade in a two-dimensional cascade the stator blade boundary-layer growth was found to be much greater. The results indicate that extreme caution should be used in attempting to predict blade boundary-layer development from cascade test results or steady calculation procedures.
Elastic Design Methods for Perforated Plates
Authors: Porowski J. S. , O’Donnell W. J.
Published: November 2010

Methods for performing finite element stress analysis of perforated plates under pressure and complex thermal loading conditions are described. The concept of the equivalent solid material of anisotropic properties is employed to define the elasticity matrices to be used for axisymmetric analysis of plates containing triangular and square patterns of circular holes. Generalized plane strain effective elastic constants are used for better approximation of the overall plate behavior. New methods and curves for obtaining local ligament stresses from the nominal stresses in the equivalent solid material are given.
Analysis of Vertically Mounted Through-Tube Heat Exchangers
Authors: Singh K. P.
Published: November 2010

A computer-oriented method for axisymmetric stress analysis of integral tubesheet exchangers is developed. The tubesheet is modeled as a composite plate consisting of a perforated interior and a solid annular plate bonded at the interface radius. The interaction of the shell and channel with the tubesheet is included in the analysis. To incorporate the effect of gravity loads in vertical units, the shell and tubeside pressures are allowed to be different at the two tubesheet locations. An analytical expression for the differential longitudinal expansion of the tubes over the shell is also devised.
Mixing Process Induced by the Vorticity Associated with the Penetration of a Jet into a Cross Flow
Authors: Grive`s E. Le
Published: November 2010

The turbulent process associated with the penetration of a jet into a subsonic cross flow has been investigated in regard to various motivations: cooling of combustion products, discharge of effluents into a waterway, aerodynamic phenomena related to VTOL aircraft. Starting from a theoretical model of the penetration and mixing processes for jets issued from a circular orifice which agrees with experimental data within a wide range of injection patterns, a simple expression was found for the mass flow engulfed by the contrarotating vortices. The coherent vortex structure, which has been identified by several investigators, is superimposed on the turbulent diffusion mixing process, and can be further analyzed in connection with the penetration model. Closed form equations are presented for the vortex strength and spacing, assuming the bidimensional straight vortex filament approximation first proposed by Fearn and Weston. The resulting predictions are found in fair agreement with data from velocity surveys by various techniques.
Design and Operational Influences on Thermal Performance of “Solaris” Solar Collector
Authors: Beard J. T. , Iachetta F. A. , Lilleleht L. U. , Huckstep F. L. , May W. B.
Published: November 2010

Thermal performance characteristics of the “Solaris” water-trickle collector have been experimentally determined using the University of Virginia Solar Energy Research Facility. A theoretical model of the collector has also been used to examine the thermal performance of the collector. The model and experimental measurements were used to determine the sensitivity of the collector’s performance to such variables as ambient temperature, mass flow rate, insolation rate, wind, and glazing cleanliness. It was found that ambient temperature and wind are the two major variables which influence collector performance. Experimental measurements and the model also were used to demonstrate how design changes, such as glazing spacing, glazing material, double glazing, and condensate suppression influence and the performance of the water-trickle collector. Various glazing materials and double glazing were found to greatly change the collector’s performance. Changes in performance are reported in terms of the performance parameters FR, (τα)e and UL and graphically illustrated with plots of collection efficiency versus (Ti − Ta)/I.
A Thermodynamic Study of Heating with Geothermal Energy
Authors: Reistad G. M. , Yao B. , Gunderson M.
Published: November 2010

A thermodynamic analysis of various methods of heating while using either purely geothermal energy or a combination of geothermal energy and conventional energy has been completed. Since geothermal energy, unlike conventional fuels, has an available energy that is markedly lower than its energy, a first law of thermodynamics performance parameter cannot accurately portray the thermodynamic performance and the second law based performance parameter (effectiveness) is used as the objective function during optimization. Results of the analysis present the optimum performance of several systems as a function of heating temperature and geothermal resource temperature. These results show that when only heating is required at a temperature substantially below the existing geothermal resource temperature a conventional direct geothermal heating system is thermodyanmically desirable. However, when heating is desired at temperatures near that of the geothermal resource, systems that use heat pumps can provide superior performance. Furthermore, for the usual range of water-dominated geothermal resource temperatures (up to about 500 or 525 K) some geothermally based heating systems have performance superior to that of fossil-fired furnaces and electric resistance heating systems at heating temperatures up to, and somewhat above, that of the resource temperature. At higher heating temperature, however, it is shown that furnaces and electric resistance heating systems improve their relative position and can have superior performance.
Asymmetric Swirling Flows in Turbomachine Annuli
Authors: Greitzer E. M. , Strand T.
Published: November 2010

An analytical and experimental investigation of asymmetric annular swirling flows is presented. It is shown that, in contrast to the situation in nonswirling flow, the different types of flow disturbances (pressure and vorticity) are not separable in a swirling flow but are strongly coupled. The flows that occur due to this coupling are inherently three-dimensional and exhibit new features not seen in the nonswirling case. The theoretical predictions are in good agreement with experimental measurements carried out in an annular swirl rig.
Influences on Exhaust Emissions from Automotive Gas Turbines
Authors: Buchheim R.
Published: November 2010

Experimental and theoretical investigations on conventional diffusion flame type combustors and on premix/prevaporize combustors were performed. The range of pollutant levels attainable with the various types of combustors is analyzed. The effect of different fuel nozzles, various fuels, and gas turbine thermodynamic cycle data on exhaust emissions is shown. Correlations are developed as far as possible.
Application of Nonseries Airfoil Design Technology to Highly Loaded Turbine Exit Guide Vanes
Authors: Monello J. A. , Mitchell W. S. , Tall W. A.
Published: November 2010

Common practice in turbine exit guide vane design is to utilize standard series airfoils. This paper presents results of an analytical and experimental program where the performance of a series airfoil is compared to an equivalent nonseries airfoil. The nonseries airfoil is designed by selecting airfoil camber and thickness distributions which reduce the potential for suction surface separation. Airfoil pressure distribution and boundary layer analysis techniques are used to identify the optimum nonseries airfoil. Back-to-back annular cascade tests of equivalent series and nonseries airfoils substantiate analytical predictions. The tests indicate nonseries airfoil design technology enables diffusing airfoils to be designed with improved performance at higher loading levels than presently obtainable with equivalent series airfoils.
Periodically Unsteady Flow in an Imbedded Stage of a Multistage, Axial-Flow Turbomachine
Authors: Wagner J. H. , Okiishi T. H. , Holbrook G. J.
Published: November 2010

A periodic-average flow measurement technique involving a hot-wire sensor was used to measure the periodically unsteady velocity field in the first stage of a low-speed, multistage, axial-flow research compressor. In portions of the compressor annulus, the periodic-average velocity patterns for imbedded rotor and stator exit flows showed appreciable sequential variation with the systematically changed data sampling position of the rotor blades. Representative examples of periodic-average flow field variation with rotor blade sampling position in stop-action sequence are shown for various locations in the compressor. A simple, first-order approximation physical description of blade wake flow transport and interaction based on experimental data interpretation is proposed to organize and thus help understand the data obtained.
Reasons for Centrifugal Compressor Surging and Surge Control
Authors: Kolnsberg A.
Published: November 2010

The paper discusses conventional modes of presenting axial and radial compressor operating envelopes and the conditions under which changes of factors such as the polytropic index n and the Reynolds number Re are negligible. It is shown on the basis of operating envelopes under what conditions compressors will surge (erratic flow conditions or stalling). In axial or radial compressor installations, surging can only be controlled by shifting the operating point in the operating envelope to the right away from the surge limit line. One method of doing this is to open the bypass valve to recycle part of the gas from the discharge piping to the suction piping. The paper describes in detail the control system required and discusses universal and simplified control systems. Modifications of control systems to fit, for example, wide suction pressure ranges are studied. The paper concludes with an investigation of methods of providing for high surge control reliability.
Effects of Steam Injection on the Performance of Gas Turbine Power Cycles
Authors: Fraize W. E. , Kinney C.
Published: November 2010

The effect of injecting steam generated by exhaust gas waste heat into a gas turbine with 3060°R turbine inlet temperature has been analyzed. Two alternate steam injection cycles are compared with a combined cycle using a conventional steam bottoming cycle. A range of compression ratios (8, 12, 16, and 20) and water mass injection ratios (0 to 0.4) were analyzed to determine effect on net turbine power output per pound of air and cycle thermodynamic efficiency. A water/fuel cost tradeoff analysis is also provided. The results indicate promising performance and economic advantages of steam injected cycles relative to more conventional utility power cycles. Application to coal-fired configuration is briefly discussed.
Propulsion System Considerations for the Subsonic V/STOL
Authors: Cyrus J. D. , DeVillier M. , Kaminski J.
Published: November 2010

A representative subsonic V/STOL aircraft operating on a single mission has been used as a baseline to investigate the impact of various propulsion system tradeoffs. After establishing a cycle for the propulsion system and estimating V/STOL related installation penalties, parametric engine-aircraft-mission studies have been conducted. These studies have established takeoff gross weight benefits of up to 13 percent that may be obtained by appropriate selection of the core engine sizing location. Studies of two, three and four engine versions of the configuration have shown that three engine and four engine aircraft may have 20 percent lower weight than a two engine version, but this arises at the cost of significantly reduced hot section life.
Reduction of Pollutant Emissions From Industrial Boilers by Combustion Modification
Authors: Cato G. A. , Hall R. E. , Muzio L. J.
Published: November 2010

The use of combustion modification has enabled many utility boilers to meet the emission standards for NOx. Its usefulness in reducing NOx emissions from industrial boilers (ranging from 11 GJ/hr to 528 GJ/hr) has been investigated during a recently completed field test program. The gaseous and particulate emissions from coal, oil, and natural-gas fuels were measured both before and after the combustion modification. Data were taken on particulate size as well as concentration. The principal combustion modification methods that were investigated included reduced excess combustion air, staged combustion air, recirculated flue gas, tuned burners, and reset burner registers. Staging was implemented by the use of overfire air ports or by turning off the fuel to some burners and increasing the fuel to others, thus creating zones of fuel-rich combustion. All of the combustion modification methods were effective to varying degrees in reducing the nitrogen oxides emissions, and reductions of as much as 50 percent were obtained with several of the modifications. In most instances the boiler efficiency was not degraded, although the particulate emissions increased by up to 50 percent in some cases. There was no substantive effect on the other pollutant emissions that were measured.
Economics of Feedwater Heater Replacement
Authors: Fehring T. H. , Gaggioli R. A.
Published: November 2010

As feedwater heaters age, performance deteriorates and leaks invariably occur. In order to keep the heater functioning properly, and to avoid the possibility of water backing into the turbine and causing damage, the leaking tubes are plugged. Usually, the initially plugged tubes cause small, if any, deterioration of performance. Eventually, the number of plugged tubes significantly affects the overall cycle efficiency. This paper presents a straightforward method for calculating the economical time for repair or replacement, without the need for extensive heat balance calculations or special rules of thumb. While the analysis presented here, based on the useful energy concept, is used to solve an operating problem, the same methods can be readily applied at the design stage, and can be used on any other component in the power cycle as well.
Land Gas Turbine Exhaust Noise
Authors: Kantola R. A.
Published: November 2010

An acoustic test program on a 1/7-scale model of the exhaust configuration for a General Electric MS 5000 gas turbine has been carried out. The tests were designed to isolate the noise contributions of the individual exhaust system components and to identify the additional noise due to combinations of two or more components. This model of the MS 5000 system was found to have three principal noise sources. At a high degree of turbine exit swirl all three sources appear with the most dominant due to an interaction between aft bearing support strut wakes and downstream exhaust hood turning vanes. At zero swirl the isolated turning vane noise and an exhaust hood plenum resonance are the remaining principal noise sources. A rather unexpected effect was uncovered in the course of this program; a strong reduction in the noise generation of separated flow downstream of struts and vanes was observed when a diffuser was placed immediately behind the strut or vane exit plane. This reduction in noise was much greater than could be attributed to the reduction in velocity caused by the diffuser.
Approximate Solution to a Class of Transient Forced Convection Problems
Authors: Sucec J.
Published: November 2010

Approximate solutions using integral methods and the method of characteristics are found for the case of laminar, low speed, constant property, two-dimensional planar boundary layer type flow over a body which is initially at the constant temperature of the fluid passing over it and then, suddenly, has its surface temperature changed to a new constant value or has a constant heat flux imposed at the surface. The free stream velocity is variable with position along the body and the entire velocity field is assumed to be in the steady state. Response curves for surface heat flux or of surface temperature as a function of position and time are presented for power law variations of free stream velocity (the “wedge” type flows) and also for one particular nonsimilar (nonwedge) case. The relative ease with which the nonsimilar cases can be handled is thought to make the approach, advanced herein, a useful tool for the engineer to attack other nonsimilar cases. It was also found that the use of an “equivalent” wedge variable gives reasonably satisfactory results for the nonsimilar case chosen. Hence the application of the equivalent wedge methods is valid for transient forced convection problems just as it is, as is well known, for steady-state forced convection.
A Rotating Stall Control System for Turbojet Engines
Authors: Ludwig G. R. , Nenni J. P.
Published: November 2010

This paper describes the operating principle of a rotating stall control system and the results of testing a prototype control on a low-speed research compressor and on a J-85-5 turbojet engine. The control is an electrical feed-back control system which uses unsteady pressure signals produced by sensors within the compressor to detect the presence of stall and provide a correction signal when stall occurs. In the prototype system, the correction signal is used to drive a hydraulic actuator which provides a mechanical operation on some variable geometry feature of the compressor being controlled. On the low-speed research compressor the variable geometry was the stagger angle of the stator rows. On the J-85 engine, the control was installed to override the normal operating schedule of the compressor bleed doors and flaps on the inlet guide vanes. Both series of tests were successful in that the control rapidly eliminated rotating stall when it occurred and in some cases did not allow rotating stall to occur at all.
A New Appraisal of Reynolds Number Effects on Centrifugal Compressor Performance
Authors: Wiesner F. J.
Published: November 2010

This paper summarizes the results of an investigation into the effects of Reynolds number on the performance of centrifugal compressor stages, using a computer program for the detailed prediction of component and overall performance characteristics. This investigation included wide variation of stage geometries, speeds, and fluid conditions, resulting in diffuser inlet absolute Reynolds number variations over the range from 5 × 102 to 5 × 108. The computer results indicate that variations in Reynolds number and in relative roughness will produce variations in all significant performance parameters: the flow coefficient, the work coefficient, and the efficiency. Correlations of these results with various sources of test data on single and multistage centrifugal compressors produce very satisfactory comparisons. As a result of this study, improved empirical methods are recommended for making practical adjustments of compressor performance with variation in Reynolds number. These recommendations should be taken into account in the modernization of all centrifugal compressor performance test codes such as those formulated by ASME and ISO.