Showing papers in "Journal of Engineering for Power in 1982"
TL;DR: In this article, the aerodynamic interaction between the rotor and stator airfoils of a large scale axial turbine stage has been studied experimentally with axial gaps of 15 and 65 percent of axial chord.
Abstract: The aerodynamic interaction between the rotor and stator airfoils of a large scale axial turbine stage have been studied experimentally. The data included measurements of the time averaged and instantaneous surface pressures and surface thin film gage output on both the rotor and stator at midspan. The data also included measurement of the stator suction and pressure surface time averaged heat transfer at midspan. The data was acquired with rotor-stator axial gaps of 15 and 65 percent of axial chord. The upstream potential flow influence of the rotor on the stator was seen as well as the downstream potential flow and wake influences of the stator on the rotor. It was also seen that at the 15 percent axial gap, the stator heat-transfer coefficient was typically 25 percent higher than that at the 65 percent gap.
326 citations
TL;DR: In this paper, a mean line loss system is described, capable of predicting the design point efficiencies of current axial turbines of gas turbine engines, which is a development of the Ainley/Mathieson technique of 1951.
Abstract: A mean line loss system is described, capable of predicting the design point efficiencies of current axial turbines of gas turbine engines. This loss system is a development of the Ainley/Mathieson technique of 1951. The prediction method is tested against the ''Smith's Chart'' and against the known efficiencies of 33 turbines of recent design. It is shown to be able to predict the efficiencies of a wide range of axial turbines of conventional stage loadings to within 1 1/2 percent. 13 refs.
298 citations
TL;DR: In this article, the authors measured heat transfer coefficients on pin and endwall surfaces for several staggered arrays of short pin fins and found that the measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested.
Abstract: Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat-transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat-transfer surface area compared to a plain wall. A heat-transfer data base for these short pins is not available in the literature. Heat-transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat-transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).
204 citations
TL;DR: In this paper, a simple tip-leakage model is proposed that treats the normal velocity component in terms of discharge coefficient and conserves the tangential velocity (momentum) component.
Abstract: Blade tip losses represent a major efficiency penalty in a turbine rotor. These losses are presently controlled by maintaining close tolerances on tip clearances. This two-part paper outlines a new methodology for predicting and minimizing tip leakage flows. Part I of the paper describes a series of experiments and analyses which indicated a predominantly inviscid nature of tip leakage flow. The experiments were conducted on a series of three water flow rigs in which leakage quantities were measured over simulated blade tips. As a result of the experiments, a simple tip-leakage model is proposed that treats the normal velocity component in terms of discharge coefficient and conserves the tangential velocity (momentum) component. Identification of tip leakage controlled by a normal discharge coefficient suggests an optimum tip-treatment configuration may be designed through discharge testing of candidate configurations. A preliminary design optimization was conducted on the simple discharge rigs, and the results were evaluated on the water table cascade rig and on a turbine stage.
152 citations
TL;DR: In this paper, an analysis based on the Jeffcott model is presented to explain 1/2 speed and 1/3 speed whirling motion occurring in rotors which are subject to periodic normal-loose or normal-tight radial stiffness variations.
Abstract: Analysis based on the Jeffcott model is presented to explain 1/2 speed and 1/3 speed whirling motion occurring in rotors which are subject to periodic normal-loose or normal-tight radial stiffness variations. The normal-loose stiffness variation results due to bearing-clearance effects, while normal-tight stiffness variations result from rubbing over a portion of a rotor's orbit. The results demonstrate that 1/2 speed subharmonic motion can be explained as either a linear parametric-excitation phenomenon or as a stable nonlinear subharmonic motion. The 1/3 speed motion is shown to be possible due to the radial stiffness nonlinearity. A linear parametric-excitation analysis demonstrates that during a normal-tight rubbing condition, Coulomb damping significantly widens the potential range of unstable speeds.
130 citations
TL;DR: In this paper, an approximate method is presented with which both of these effects can be included in design through-flow calculations in axial-flow turbomachines, where substantial spanwise mixing of flow properties often occurs.
Abstract: Flow measurements taken in multistage axial-flow turbomachines suggest that substantial spanwise mixing of flow properties often occurs. In addition, measured blade row turnings often show considerable deviation from two-dimensional cascade theory, particularly in the end-wall regions. An approximate method is presented with which both of these effects can be included in design through-flow calculations. 21 refs.
117 citations
TL;DR: In this article, a large-scale, two-dimensional incompressible transitional boundary layer flows were analyzed on a heated flat wall with a zero pressure gradient for two levels of streamwise acceleration.
Abstract: Results from an experimental study of large-scale, two-dimensional incompressible transitional boundary layer flows are presented. Tests were conducted on a heated flat wall with a zero pressure gradient for two levels of streamwise acceleration. Convective heat-transfer distributions, laminar, transitional, and fully turbulent boundary layer mean velocity and temperature profile data, and free-stream turbulence intensity distributions are presented. Boundary layer integral quantities and shape factors are also given. Transition onset Reynolds number data obtained for this program agreed well with the results of other experimental and theoretical studies for both zero pressure gradient and accelerating flows. Comparisons of the profile data and wall heat-transfer distribution data indicated that fully turbulent mean velocity profiles were achieved upstream of fully turbulent wall heat-transfer rates.
82 citations
TL;DR: The detailed nature of the three-dimensional flow over the blading, and in the wake, of an isolated compressor rotor has been studied experimentally in a large scale rotating rig.
Abstract: The detailed nature of the three-dimensional flow over the blading, and in the wake, of an isolated compressor rotor has been studied experimentally in a large scale rotating rig. A variety of flow properties were measured including (1) blade profile and endwall surface flow visualization. (2) radial-circumferential arrays of pneumatic wake data acquired in the rotating frame and (3) full-span blade pressure distribution data. 23 refs.
76 citations
63 citations
TL;DR: Shallow shell theory and the Ritz method are employed to determine the frequencies and mode shapes of turbomachinery blades having both camber and twist, rotating with non-zero angles of attack as discussed by the authors.
Abstract: Shallow shell theory and the Ritz method are employed to determine the frequencies and mode shapes of turbomachinery blades having both camber and twist, rotating with non-zero angles of attack. Frequencies obtained for different degrees of shallowness and thickness are compared with results available in the literature, obtained from finite element analyses of nonrotating blades. Frequencies are also determined for a rotating blade, showing the effects of changing the (1) angular velocity of rotation, (2) disk radius and (3) angle of attack, as well as the significance of the most important body force terms.
60 citations
TL;DR: A generalized mathematical model is described to estimate gas tubine performance in the starting regime of the engine and these estimates are then used to calculate the minimum engine starting torque requirements, thereby defining the specifications for the aircraft starting system.
Abstract: This paper describes a generalized mathematical model to estimate gas tubine performance in the starting regime of the engine. These estimates are then used to calculate the minimum engine starting torque requirements, thereby defining the specifications for the aircraft starting system. Alternatively, the model can also be used to estimate the start up time at any ambient temperature or altitude for a given engine/aircraft starting system combination.
TL;DR: In this paper, the impingement cooled mid-chord region of gas turbine airfoils in cases where an initial crossflow is present is modeled and flow distributions for jet arrays with ten spanwise rows of holes are determined.
Abstract: To model the impingement cooled mid-chord region of gas turbine airfoils in cases where an initial crossflow is present, the paper presents experimentally determined flow distributions for jet arrays with ten spanwise rows of holes, which range from uniform to highly nonuniform. The jet flow after impingement is constrained to exit in a single direction along the channel formed by the jet orifice plate and the impingement surface. The streamwise distributions and crossflow velocities are presented for ratios of the initial crossflow rate to the total jet flow rate ranging from zero to unity. For crossflow to jet velocity ratios greater than a value somewhat less than unity, jet orifice discharge coefficients do not remain constant, but decrease significantly, showing a secondary dependence on z/d, where z is the channel height and d is the jet hole diameter.
TL;DR: In this article, a simple model for full-span stall cells in axial compressors has been formulated and the sudden changes in velocity across blade rows as the blade passages enter and leave the stall are shown to have important dynamical consequences for the stall flow field.
Abstract: A simple model for full-span stall cells in axial compressors has been formulated. The sudden changes in velocity across blade rows as the blade passages enter and leave the stall are shown to have important dynamical consequences for the stall flow field. The one empirical constant needed in the analysis is determined using the data of Day. From this, reasonable predictions of stall cell speed and trends in speed have been obtained for a number of different compressors. 10 refs.
TL;DR: In this paper, a method for automating compressor blade design using numerical optimization, and applied to the design of a controlled diffusion stator blade row, is presented, where a general-purpose optimization procedure is employed, based on conjugate directions for locally unconstrained problems and on feasible directions for local constrained problems.
Abstract: A method for automating compressor blade design using numerical optimization, and applied to the design of a controlled diffusion stator blade row is presented. A general purpose optimization procedure is employed, based on conjugate directions for locally unconstrained problems and on feasible directions for locally constrained problems. Coupled to the optimizer is an analysis package consisting of three analysis programs which calculate blade geometry, inviscid flow, and blade surface boundary layers. The optimizing concepts and selection of design objective and constraints are described. The procedure for automating the design of a two dimensional blade section is discussed, and design results are presented.
TL;DR: In this article, a method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems, which allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces.
Abstract: The method of component mode synthesis is developed to determine the forced response of nonlinear, multishaft, rotor-bearing systems. The formulation allows for simulation of system response due to blade loss, distributed unbalance, base shock, maneuver loads, and specified fixed frame forces. The motion of each rotating component of the system is described by superposing constraint modes associated with boundary coordinates and constrained precessional modes associated with internal coordinates. The precessional modes are truncated for each component and the reduced component equations are assembled with the nonlinear supports and interconnections to form a set of nonlinear system equations of reduced order. These equations are then numerically integrated to obtain the system response. A computer program, which is presently restricted to single shaft systems, has been written and results are presented for transient system response associated with blade loss dynamics with squeeze film dampers, and with interference rubs.
TL;DR: The results of a study supported by NASA under the Energy Efficient Engine Program, conducted to investigate the development of boundary layers under the influence of velocity distributions that simulate the suction sides of two state-of-the-art turbine airfoils, are presented in this paper.
Abstract: The results of a study supported by NASA under the Energy Efficient Engine Program, conducted to investigate the development of boundary layers under the influence of velocity distributions that simulate the suction sides of two state-of-the-art turbine airfoils, are presented. One velocity distribution represented a forward loaded airfoil ('squared-off' design), while the other represented an aft loaded airfoil ('aft loaded' design). These velocity distributions were simulated in a low-speed, high-aspect-ratio wind tunnel specifically designed for boundary layer investigations. It is intended that the detailed data presented in this paper be used to develop improved turbulence model suitable for application to turbine airfoil design.
TL;DR: In this paper, the authors measured the turbulence properties in the annulus wall region of an axial flow compressor rotor using a triaxial, hot-wire probe rotating with the rotor.
Abstract: The turbulence properties in the annulus wall region of an axial flow compressor rotor was measured using a triaxial, hot-wire probe rotating with the rotor. The flow was surveyed across the entire passage at five axial locations (leading edge, 1/4 chord, 1/2 chord, 3/4 chord, and the trailing edge location) and at six radial locations in a low-speed compressor rotor. The data derived include all three components of turbulence intensity and three components of turbulence stress. A comprehensive interpretation of the data with emphasis on features related to rotation, leakage flow, annulus wall boundary layer, and blade boundary layer interactions is included. All the components of turbulent intensities and stresses are found to be high in the leakage-flow mixing region. The radial component of intensities and stresses is found to be much higher than the corresponding streamwise components. The turbulent spectra clearly reveal the decay process of the inlet-guide-vane wake within the rotor passage.
TL;DR: In this article, a new methodology for predicting and minimizing tip flows was proposed, and the control of tip leakage through minimization of the discharge coefficient to control the normal leakage flow component was achieved through viscous analysis.
Abstract: Blade tip losses represent a major efficiency penalty in a turbine rotor. These losses are presently controlled by maintaining close tolerances on tip clearances. This two-part paper outlines a new methodology for predicting and minimizing tip flows, and focuses on the control of tip leakage through minimization of the discharge coefficient to control the normal leakage flow component. Minimization of the discharge coefficient was achieved through viscous analysis and was supported by discharge-rig testing. The analysis for the discharge cross-flow used a stream function-vorticity formulation. Support testing was conducted with a newly developed water table discharge rig in which tip-coolant discharge could also be simulated. Experimental and numerical tip-leakage results are presented on a discharge coefficient parameter for five different tip configurations. In addition, numerical studies were conducted for stationary and rotating blades with and without tip coolant injection.
TL;DR: In this article, heat-flux and pressure mesurements were obtained using state-of-the-art, shock-tube technology and well established transient test techniques (thin-film gages and fast-response pressure transducers).
Abstract: This paper describes heat-flux and pressure mesurements that were obtained using state-of-the-art, shock-tube technology and well established transient-test techniques (thin-film gages and fast-response pressure transducers). These measurements were performed for a full turbine stage of the AiResearch TFE 731-2 engine. 27 refs.
TL;DR: In this article, it was shown that beam theory is generally inadequate to determine the free vibration frequencies and mode shapes of turbomachinery blades and that shallow shell theory is capable of representing all the vibration modes accurately.
Abstract: Vibration analysis of turbomachinery blades has traditionally been carried out by means of beam theory. In recent years two-dimensional methods of blade vibration analysis have been developed, most of which utilize finite elements and tend to require considerable computation time. More recently a two-dimensional method of blade analysis has evolved which does not require finite elements and is based upon shell equations. The present investigation has the primary objective to demonstrate the accuracy and limitations of blade vibration analyses which utilize one-dimensional, beam theories. It is found that beam theory is generally inadequate to determine the free vibration frequencies and mode shapes of moderate to low aspect ratio turbomachinery blades. The shallow shell theory, by contrast, is capable of representing all the vibration modes accurately. However, the one-dimensional beam theory has an important advantage over the two-dimensional shell theory for blades and vibration modes. It uses fewer degrees of freedom, thus requiring less computer time.
TL;DR: In this paper, the authors investigated the factors governing the blowoff velocities of stabilized flames supplied with flowing gaseous combustible mixtures and derived an equation for predicting blowoff.
Abstract: Experimental and theoretical studies are carried out on the factors governing the blowoff velocities of stabilized flames supplied with flowing gaseous combustible mixtures. The test program encompasses wide variations in effective pressure, obtained using the water injection technique, and wide ranges of velocity, flameholder size, and flameholder blockage. An equation for predicting blowoff13; velocities is derived that shows good agreement with the experimental data. In the water-injection technique, low pressures are simulated by injecting water or steam into the fuel-air mixture flowing into the combustion zone. This approach makes it possible for complete stability loops to be drawn for large flameholders, up to 8 cm in
TL;DR: In this paper, the effects of bending-torsion interaction of the flutter boundaries of turbomachinery blading are investigated, in the presence of structural damping, and two different speed regimes are investigated: incompressible flow and supersonic flow with a subsonic leading edge locus.
Abstract: A study of the effects of bending-torsion interaction of the flutter boundaries of turbomachinery blading is presented. The blades are modeled as equivalent sections, and the equations of motion allow for the general case of structural, inertial and aerodynamic coupling, in the presence of structural damping. Two different speed regimes are investigated: incompressible flow, and supersonic flow with a subsonic leading edge locus. Flutter boundaries are presented for cascade design parameters representative of current technology fan rotors. These results illustrate that bending-torsion interaction has a pronounced effect on the flutter boundaries for both speed regimes, although the mode frequencies show no appreciable tendency to coalesce as flutter is approached. Several cases of bending branch instability were observed, without incorporating the effects of finite mean lift or strong shocks in the analysis.
TL;DR: In this article, a rotating three-sensor, hot-wire probe was used along with rotor blade static pressure measurements to investigate the complex inviscid and viscid effects in the annulus wall flowfield, including the three components of mean velocity, turbulence intensity, and turbulence stress inside the rotor blade passage.
Abstract: A rotating three-sensor, hot-wire probe has been used along with rotor blade static pressure measurements to investigate the complex inviscid and viscid effects in the annulus wall flowfield, including the three components of mean velocity, turbulence intensity, and turbulence stress inside the rotor blade passage. It is found that the tip leakage flow originates near quarter-chord, with peak values occurring near mid-chord. The leakage flow, which is in the form of a jet within the blade row, is augmented by the blade rotation and travels further away from the suction surface than that observed in stationary blade rows and cascades. This leakage flow tends to roll up between the mid-passage and the pressure surface near the tip region; the vortex formation does not occur within the passage in this particular case.
TL;DR: In this paper, a small combustor of normal design employing acoustic control of the dilation-air flow has been tested up to half-load conditions, and the results showed that the pressure loss of the unit and its combustion efficiency were insignificantly affected by the acoustic drive.
Abstract: A small combustor of normal design employing acoustic control of the dilation-air flow has been tested up to half-load conditions. This technique can be used to control the exit plane temperature distribution and has the ability to trim the temperature profile. The acoustic driver power requirements were minimal, indicating that driver power at full-load will not be excessive. The nature of the acoustically modulated dilution-air flows is that of a pulsating jet flow with superimposed toroidal vortices. The pressure loss of the unit and its combustion efficiency were insignificantly affected by the acoustic drive. The work contributes to the design of combustors such that a desired exit plane temperature distribution may be achieved.
TL;DR: In this article, the performance tests of a Lysholm engine were conducted at the Lawrence Livermore National Laboratory at the University of California, and the best results were observed at higher speeds and with exhaust to an above-atmospheric backpressure.
Abstract: This is a description of the performance tests of a Lysholm engine completed at the Lawrence Livermore National Laboratory at the University of California. The Lysholm engine is a rotary displacement engine which can accept a low quality (vapor fraction) two-phase mixture. Generally, the well-head condition of geothermal fluids is a mixture of liquid and vapor, with quality up to 40 percent, although for most liquid dominated geothermal resources the vapor fraction is considerably less than 40 percent. As a thermodynamic process, using mixed phase flow has the potential for using significantly more of the available energy output per pound of fluid, as contrasted with other processes that either transfer heat energy to a second fluid, or use only the vapor fraction and discard the liquid. In our tests, the quality was varied between 8 and 27 percent. Our results indicate that the Lysholm engine can operate well with a two-phase mixture as a working fluid. The maximum observed engine efficiency was 53 percent at 8000 rpm, with an inlet pressure of 190.6 psia, 22.2 percent quality, and an exhaust pressure of 30.6 psia. The best results were observed at the higher speeds and with exhaust to an above-atmospheric backpressure.
TL;DR: In this paper, the chemical kinetics of SO/sub 3/ formation were analyzed for a large stationary gas turbine, and the results showed that the SO trioxide in gas turbine exhaust contributes to particulate emissions.
Abstract: Sulfur trioxide in gas turbine exhaust contributes to particulate emissions; reduction of this compound is a means for control of particulate emissions. The chemical kinetics of SO/sub 3/ formation were analyzed for a large stationary gas turbine. 18 refs.
TL;DR: In this paper, the interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines.
Abstract: The interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines. The model is initiated with consideration of the particle phase mass conservation equation for a two-dimensional boundary layer, including the thermophoretic flux term directed toward the cold wall. A formalism of a turbulent flow near a flat plate in a heat transfer problem is adopted, and variable property effects are neglected. Attention is given to the limit of very large Schmidt numbers and the particle concentration depletion outside of the Brownian sublayer. It is concluded that, in the parameter range of interest, thermophoresis augments the high Schmidt number mass-transfer coefficient by a factor equal to the product of the outer sink and the thermophoretic suction.