Showing papers on "Axial compressor published in 1987"
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TL;DR: In this article, the vortical flow patterns in the wake of a NACA 0012 airfoil pitching at small amplitudes were studied in a low speed water channel, and it was shown that a great deal of control can be exercised on the structure of the wake by the control of the frequency, amplitude and also the shape of the oscillation waveform.
Abstract: The vortical flow patterns in the wake of a NACA 0012 airfoil pitching at small amplitudes are studied in a low speed water channel. it is shown that a great deal of control can be exercised on the structure of the wake by the control of the frequency, amplitude and also the shape of the oscillation waveform. An important observation in this study has been the existence of an axial flow along the cores of the wake vortices. Estimates of the magnitude of the axial flow suggest a linear dependence on the oscillation frequency and amplitude.
672 citations
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09 Apr 1987
TL;DR: An implantable axial flow blood pump maximizes the blood flow while minimizing the dimensions of the pump as mentioned in this paper, which is made possible by the use of neodymium-boron-iron rotor magnets which allow a substantial gap between the static motor armature and the rotor.
Abstract: An implantable axial flow blood pump maximizes the blood flow while minimizing the dimensions of the pump. By magnetically suspending a rotor of relatively small diameter coaxially in a cylindrical blood conduit of substantially larger inner diameter, an adequate flow area through the pump is provided, and the need for bearings, lubrication and seal purging fluid is eliminated. This is made possible by the use of neodymium-boron-iron rotor magnets which allow a substantial gap between the static motor armature and the rotor. The rotor is simultaneously torqued and maintained in a position coaxial with the blood conduit by individually varying the current in the armature windings while they are being commutated. The position of the rotor axis is accurately sensed by placing magnetically permeable strips into opposite ends of the pump stator blades in such a manner that they transmit to Hall sensors variations in an annular magnetic field surrounding the rotor adjacent the ends of the pump stator blades.
195 citations
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TL;DR: In this article, a relatively simple model is used to examine the influence of various distortions in setting this instability point, and it is found that the model reproduces known experimental trends for the loss of stability margin with increasing distortion amplitude and with changes in reduced frequency.
Abstract: This paper describes the development of a new analysis to predict the onset of flow instability for an axial compressor operating in a circumferentialy distorted inlet flow. A relatively simple model is used to examine the influence of various distortions in setting this instability point. It is found that the model reproduces known experimental trends for the loss of stability margin with increasing distortion amplitude and with changes in reduced frequency. In particular, there is a recognizable 'critical sector angle' which characterizes loss of stability margin. To the authors' knowledge, this is the first time the effects described herein have been theoretically demonstrated as the direct result of a fluid dynamic stability.
114 citations
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TL;DR: Both axial and secondary velocities were measured, enabling a detailed description of the complete flow field, and the development of the axial flow field can be quite well explained from the secondary velocity field.
Abstract: Laser-Doppler velocity measurements were performed on the entry flow in a 90° bend of circular cross-section with a curvature ratio a/R = 1/6. The steady entry velocity profile was parabolic, having a Reynolds number Re = 700, with a corresponding Dean number ? = 286. Both axial and secondary velocities were measured, enabling a detailed description of the complete flow field. The secondary flow at the entrance of the bend was measured to be directed completely towards the inner bend. Significant disturbance of the axial velocity field was not measured until a downstream distance (aR)½. Maximum secondary velocities were measured at 1.7 (aR)½ downstream from the inlet. The development of the axial flow field can be quite well explained from the secondary velocity field.
108 citations
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20 Nov 1987TL;DR: In this article, a turbofan gas turbine engine comprising in axial flow series a fan, a booster compressor and a core engine is provided with a diffuser, which is positioned axially between the booster and the compressor of the core engine.
Abstract: A turbofan gas turbine engine comprising in axial flow series a fan, a booster compressor and a core engine is provided with a diffuser The diffuser is positioned axially between the booster compressor and the compressor of the core engine to efficiently diffuse the air from the fan to the compressor of the core engine The diffuser comprises a plurality of circumferentially arranged geodesic pipe diffusers, the pipe diffusers extend axially and radially and the outlets of the pipe diffusers are displaced circumferentially by an angle of between 20° and 60° with respect to the inlets of the pipe diffusers The geodesic pipe diffusers allows the airflow between the fan and the core engine to be diffused adequately without compromising the efficiency of the core engine, or the high mass flow rate of the fan and also minimizes the length, weight and drag of the gas turbine engine
100 citations
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TL;DR: Analyse numerique de l'ecoulement tridimensionnel d'un fluide visqueux dans un rotor de compresseur transsonique as discussed by the authors.
Abstract: Analyse numerique de l'ecoulement tridimensionnel d'un fluide visqueux dans un rotor de compresseur transsonique. Comparaison avec l'experience
70 citations
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TL;DR: In this article, the kink angles of diffuser inlet both at the hub and at the cylinder are fixed exclusively for the purpose of evening out the energy profile over the duct height at the last rotor blade row in order to shorten the diffuser system and to optimise it in part load operation.
Abstract: In an axial flow gas turbine with reaction blading, whose outlet rotor blades (14) are followed by a diffuser with axial outlet into an exhaust gas pipe (13), the kink angles of the diffuser inlet both at the hub (10) and at the cylinder (9) are fixed exclusively for the purpose of evening out the energy profile over the duct height at the outlet from the last rotor blade row in order to shorten the diffuser system and to optimise it in part load operation. In addition, a mechanism provided to remove swirl from the swirling flow in the form of profile ribs (17). Where the outlet rotor blades have a high Mach number flow, which leads to a large opening angle of the blading, the diffuser is subdivided into several partial diffusers (16) via sheet metal guides (15).
51 citations
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06 Aug 1987
TL;DR: A screw compressor assembly includes a motor housing section, a compressor section and an oil separator downstream of the compressor discharge port as mentioned in this paper, and the motor housing is used to define an integral heat exchange structure through which a passage for the flow of oil is defined.
Abstract: A screw compressor assembly includes a motor housing section, a compressor section and an oil separator downstream of the compressor discharge port. The motor housing section defines a flow path for suction gas traveling to the working chamber of the compressor so that the compressor drive motor is cooled by suction gas. The motor housing section also internally defines an integral heat exchange structure through which a passage for the flow of oil is defined. Discharge pressure in the oil separator drives separated oil into the passage in the motor housing heat exchange structure prior to the delivery of such oil to compressor surfaces requiring lubrication. The oil flowing through the integral heat exchange structure is cooled by the suction gas passing over the surface of the heat exchange structure interior of the motor housing.
50 citations
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TL;DR: The relative importance of convection by secondary flows and diffusion by turbulence as mechanisms responsible for mixing in multistage axial-flow compressors has been investigated by using the ethylene tracer-gas technique and hot-wire anemometry as discussed by the authors.
Abstract: The relative importance of convection by secondary flows and diffusion by turbulence as mechanisms responsible for mixing in multistage, axial-flow compressors has been investigated by using the ethylene tracer-gas technique and hot-wire anemometry. The tests were conducted at two loading levels in a large, low-speed, four-stage compressor. The experimental results show that considerable cross-passage and spanwise fluid motion can occur and that both secondary flow and turbulent diffusion can play important roles in the mixing process, depending upon location in the compressor and loading level. In the so-called freestream region, turbulent diffusion appeared to be the dominant mixing mechanism. However, near the endwalls and along airfoil surfaces at both loading levels, the convective effects from secondary flow were of the same order of magnitude as, and in some cases greater than, the diffusive effects from turbulence. Calculations of the secondary flowfield and mixing coefficients support the experimental findings.
41 citations
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TL;DR: In this paper, the results of an investigation of the solid particle dynamics through a helicopter engine with inlet particle separator are presented, which is characterized by considerable hub and tip contouring and radial variation in the swirling vane shape.
Abstract: Aircraft engines operating in areas where the atmosphere is polluted by small solid particles are typical examples of jet engines operating under hostile atmospheric environment. The particles may be different kinds of sand, volcanic ashes or others. Under these conditions, the gas and particles experience different degrees of turning as they flow through the engine. This is mainly due to the difference in their inertia. This paper presents the results of an investigation of the solid particle dynamics through a helicopter engine with inlet particle separator. The particle trajectories are computed in the inlet separator which is characterized by considerable hub and tip contouring and radial variation in the swirling vane shape. The nonseparated particle trajectories are determined through the deswirling vanes and the five stage axial flow compressor. The results from this study include the frequency of particle impacts and the erosion distribution on the blade surfaces.
40 citations
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27 Feb 1987
TL;DR: In this paper, a method and apparatus for optimizing the radial clearance of rotor and stator vanes with their opposed structure for axial flow compressors of gas turbine power plants in which rotor disks are vented and thermally controlled by compressed air taken from the main flow path in the compressor via openings in the inner surface of the mainflow path at one or more of the compressor stages.
Abstract: A method and apparatus for optimizing the radial clearance of rotor and stator vanes with their opposed structure for axial flow compressors of gas turbine power plants in which rotor disks are vented and thermally controlled by compressed air taken from the main flow path in the compressor via openings in the inner surface of the main flow path at one or more of the compressor stages. The removed air is supplied to annular spaces formed between rotor and/or seal support disks.
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06 Mar 1987
TL;DR: In this article, the inner wall surrounding the tips of axial flow fan/compressor blades in a turbine type power plant is angularly disposed relative to the gas path wall to allow deeper penetration into the trench and minimize leakage around the tips.
Abstract: The trench inner wall surrounding the tips of axial flow fan/compressor blades in a turbine type power plant is angularly disposed relative to the gas path wall to allow deeper penetration into the trench and minimize leakage around the tips. Gap closure between the inner wall of the trench and tip is contemplated by the contour of the blade/trench.
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TL;DR: In this article, a high-power CW CO2 laser with a fast axial flow is investigated experimentally and theoretically, and the active medium is described by assuming a five-temperature model and balancing the quantum densities of vibrational states of the CO2 and N2 molecules.
Abstract: A high-power CW CO2 laser with a fast axial flow is investigated experimentally and theoretically. The gas flow is controlled by several different designs of the discharge tube which is either made of glass of cascaded metal discs. A high laser-gas purity is achieved by a Pt-Rh catalyst placed in the main flow. A laser power of 1.2 kW m-1 with 30% efficiency is reached. The active medium is described by assuming a five-temperature model and balancing the quantum densities of vibrational states of the CO2 and N2 molecules. This system of basic equations is completed by the mass, momentum and energy continuity equations. A model, method of solution and theoretical and experimental results are described and presented. The experimental results are in very good agreement with the theoretical predictions within a broad range of parameters.
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01 May 1987TL;DR: In this paper, the authors present laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan and identify the rotor wake generated and unresolved unsteadiness, respectively.
Abstract: This two-part paper presents laser anemometer measurements of the unsteady velocity field within the stator row of a transonic axial-flow fan. The objective is to provide additional insight into unsteady blade-row interactions within high speed compressors which affect stage efficiency, energy transfer, and other design considerations. Part 1 describes the measurement and analysis techniques used for resolving the unsteady flow field features. The ensemble-average and variance of the measured velocities are used to identify the rotor wake generated and unresolved unsteadiness, respectively. (Rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and the term unresolved unsteadiness refers to all remaining contributions to unsteadiness such as vortex shedding, turbulence, mass flow fluctuations, etc.). A procedure for calculating auto and cross correlations of the rotor wake generated and unresolved unsteady velocity fluctuations is described. These unsteady-velocity correlations have significance since they also result from a decomposition of the Navier-Stokes equations. This decomposition of the Navier-Stokes equations resulting in the velocity correlations used to describe the unsteady velocity field will also be outlined in this paper.
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01 Jun 1987
TL;DR: In this paper, the Squirrel-Cage-like rotor was used for a fluid energy converter with a squirrel-cage-style rotor, in which blades peripherally distributed about a horizontal axis of rotation are in a plane generally parallel to the axis of rotational motion.
Abstract: A fluid energy converter having a squirrel-cage-like rotor in which blades peripherally distributed about a horizontal axis of rotation are in a plane generally parallel to the axis of rotation. An entry at one end of the rotor is arranged to face the oncoming fluid for receipt thereof. A contoured deflector on the interior of the rotor forms an annular path or duct for redirecting the predominantly axial flow of fluid from the entry outwardly to the peripherally distributed blades and through the slots therebetween. The total area of the slots exists through which the fluid passes is preferably made less than either the entry area of the cross-sectional area of the duct leading to the blades such that the blades act as a constriction in the fluid passageway, somewhat as a venturi restriction in the flow path. The high efficiencies obtained in operating the converter are believed due to a jet action of the air released from the venturi slots between blades in addition to the force of reduced pressure produced on each blade to rotate the rotor. A ring about the entry is aerodynamically shaped to cause fluid passing over the entry to direct the fluid exiting from the blades so that it follows a greater diameter aerodynamic aft fairing structure of slightly greater diameter than the entry ring to promote greater efficiency of operation of the unit. Both air and liquid driven blading arrangements are disclosed. A second embodiment of the invention incorporates blades angled upwardly from the axis of rotation but with a directional component predominantly parallel to the axis.
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24 Nov 1987
TL;DR: In this article, the inner and outer wall of an axial compressor rotor is described as an integral, one-piece element and subsequently subdivided into arcuate segments to facilitate attachment to the compressor.
Abstract: A housing for an axial compressor is disclosed having an inner and outer wall surrounding the compressor rotor, the walls being joined by a number of flexible connecting rods, connecting lugs and a connecting block. An outer surface of the inner wall has circumferentially extending corrugation and the rods are attached thereto at peaks in the corrugation. The flexible connecting rods are located in alignment with a leading edge and a trailing edge of stator vanes which extend from an inner surface of the inner wall. The housing may be cast as an integral, one piece element and subsequently subdivided into arcuate segments to facilitate attachment to the compressor.
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29 Apr 1987
TL;DR: A turbine machine axial compressor disc comprises channels 7 which centripetally take off air for cooling the turbine, these channels are machined in thick portions 8 separated by recesses 9 and have a curvature which is identical to that of the working section of the disc as discussed by the authors.
Abstract: A turbine machine axial compressor disc comprises channels 7 which centripetally take off air for cooling the turbine. These channels are machined in thick portions 8 separated by recesses 9 and have a curvature which is identical to that of the working section of the disc. Application to aviation turbine machines.
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31 May 1987TL;DR: In this paper, the rotational wake generated and unresolved unsteadiness of axial flow fan stators was identified using a laser anemometer. Butts et al. used the procedure developed in this paper to identify the rotor wake generated unsteadness from the velocity measurements (rotor wake generated instability refers to the imbalance caused by rotor wake velocity deficit, unresolved unstebleness refers to all remaining unstebiness which contributes to the spread in the distribution of velocities such as vortex shedding, turbulence, etc.).
Abstract: Unsteady velocity field measurements made within the stator row of a transonic axial-flow fan are presented. Measurements were obtained at midspan for two different stator blade rows using a laser anemometer. The first stator row consists of double circular-arc airfoils with a solidity of 1.68. The second features controlled-diffusion airfoils with a solidity of 0.85. Both were tested at design-speed peak efficiency conditions. In addition, the controlled-diffusion stator was also tested at near stall conditions. The procedures developed here are used to identify the rotor wake generated and unresolved unsteadiness from the velocity measurements (rotor wake generated unsteadiness refers to the unsteadiness generated by the rotor wake velocity deficit and unresolved unsteadiness refers to all remaining unsteadiness which contributes to the spread in the distribution of velocities such as vortex shedding, turbulence, etc.). Auto and cross correlations of these unsteady velocity fluctuations are presented to show their relative magnitude and spatial distributions. Amplification and attenuation of both rotor wake generated and unresolved unsteadiness are shown to occur within the stator blade passage.
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TL;DR: In this paper, the origin and development of swirl center precession in engine flows were investigated in a steady flow rig, with and without a porous plate simulating a stationary piston, and in a model engine motored at 200rpm; swirl, in all cases, was generated by means of 60/sup 0/ vanes located in the axisymmetric inlet port.
Abstract: The origin and development of swirl center precession in engine flows has been investigated in a steady flow rig, with and without a porous plate simulating a stationary piston, and in a model engine motored at 200rpm; swirl, in all cases, was generated by means of 60/sup 0/ vanes located in the axisymmetric inlet port. The swirl center performs a helical motion that originates as an instability in the forced-vortex core from its interaction with the axial flow at a free stagnation point and develops in the engine from the piston towards the cylinder head; an opposite trend has been observed in the steady flow case with the open-ended cylinder. In the ensemble-averaged measurements, swirl center precession has been identified by the increased tangential velocity fluctuations around the off-centre zero swirl velocity.
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TL;DR: In this article, ten variants of a supersonic axial compressor stage were designed and tested, including two rotor configurations, three rotor tip clearances, addition of boundary-layer control consisting of vortex generators on both the outer casing and the rotor, and the introduction of slots in the stator vanes.
Abstract: Between 1970 and 1974, ten variants of a supersonic axial compressor stage were designed and tested. These included two rotor configurations, three rotor tip clearances, addition of boundary-layer control consisting of vortex generators on both the outer casing and the rotor, and the introduction of slots in the stator vanes. Design performance objectives were a stage total pressure ratio of 3.0 with an isentropic efficiency of 0.82 at a tip speed of 1600 ft/s (488 m/s). The first configuration passed only 70 percent of design flow at design speed, achieving a stage pressure ratio of 2.25 at a peak stage isentropic efficiency of 0.61. The rotor was grossly separated. The tenth variant passed 91.4 percent of design flow at design speed, producing a stage pressure ratio of 3.03 with an isentropic efficiency of 0.75. The rotor achieved a pressure ratio of 3.59 at an efficiency of 0.87 under the same conditions. Major conclusions were that design tools available today would undoubtedly permit the original goals to be met or exceeded. However, the application for such a design is currently questionable because efficiency goals considered acceptable for most current programs have risen considerably from the level considered acceptable at the inception of this effort. Splitter vanes placed in the rotor permitted very high diffusion levels to be achieved without stalling. However, viscous effects causing three-dimensional flows violating the assumption of flow confined to concentric stream tubes were so strong that a geometry optimization does not appear practical without a three-dimensional, viscous analysis. Passive boundary-layer control in the form of vortex generators and slots does appear to offer some benefit under certain circumstances.
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15 Jun 1987TL;DR: In this paper, the authors present a method of operating a transport refrigeration system having a six cylinder compressor and a prime mover operable at a selected one of low and high speeds, to control the temperature of a served space by cooling and hot gas heating modes.
Abstract: A method of operating a transport refrigeration system having a six cylinder compressor and a prime mover operable at a selected one of low and high speeds, to control the temperature of a served space by cooling and hot gas heating modes. Below a set point temperature 100, system heating capacity is controlled at the low compressor speed by the step 127 of unloading compressor cylinders and the step 129 of reloading compressor cylinders. A temperature rise of the served space above a set point temperature 106 controls cooling capacity by a combination of alternative steps 135, 137, 139, 141, and 143 which may or may not change the number of loaded compressor cylinders, and may or may not change compressor speed, based upon two predetermined trigger events which relate to what the temperature of the served space does relative to time 136 and 142, a set point temperature 106, and a temperature 108 above set point which is normally associated with a change in compressor speed.
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TL;DR: In this article, an etage de compresseur a ecoulement axial radial and resultats d'essais avec un rapport de compression de 3 is presented.
Abstract: Conception d'un etage de compresseur a ecoulement axial radial et resultats d'essais avec un rapport de compression de 3
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16 Nov 1987
TL;DR: In this article, a high ratio positive displacement recirculating rotary compressor is described, which includes an integral heat exchanger and recirculation conduits for returning cooled, high pressure discharge gas to the compressor housing to reduce heating of the compressor and enable higher pressure ratios to be sustained.
Abstract: A high ratio positive displacement recirculating rotary compressor is disclosed. The compressor includes an integral heat exchanger and recirculation conduits for returning cooled, high pressure discharge gas to the compressor housing to reducing heating of the compressor and enable higher pressure ratios to be sustained. The compressor features a recirculation system which results in continuous and uninterrupted flow of recirculation gas to the compressor with no direct leakage to either the discharge port or the intake port of the compressor, resulting in a capability of higher sustained pressure ratios without overheating of the compressor.
01 Jan 1987
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13 Oct 1987
TL;DR: In this paper, the authors propose an equalizing valve arrangement, which allows the delivery of suction gas and entrained oil to the shells of individual operating compressors in quantities which maintain the pressures therein equal.
Abstract: A refrigeration system has multiple compressors in a parallel arrangement. The pressures in the shells of operating compressors are maintained equal by the controlled delivery of suction gas and entrained oil to the shells of individual operating compressors in quantities which maintain the pressures therein equal. A valve, directly responsive to compressor shell pressures, occludes the flow of suction gas to the shell of an operating compressor in which the pressure is greater than that found in the shell of another operating compressor so as to equalize the pressures in the compressor shells. The equalizing valve arrangement directs and apportions essentially the entire amount of suction gas to the shells of operating compressors while cutting off the flow of suction gas into the shells of non-operating compressors. By managing the flow of suction gas so as to maintain shell pressures equal in operating compressors, equal amounts of entrained oil are directed to the shells of the operating compressors so as to ensure that no operating compressor becomes starved for oil.
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19 May 1987TL;DR: In this article, a supervisory computer is provided for controlling a compressor wherein a computer generated set point manipulates flow in a recycle line from the compressor outlet to inlet to prevent the compressor from surging due to changes in flow rate, pressure or the molecular weight of the gas being compressed.
Abstract: A supervisory computer is provided for controlling a compressor wherein a computer generated set point manipulates flow in a recycle line from the compressor outlet to inlet. The supervisory computer manipulates the recycle flow so as to prevent the compressor from surging due to changes in flow rate, pressure or the molecular weight of the gas being compressed. The molecular weight of the gas is calculated on-line from actual measurements of flow, pressure, temperature and speed along with compressor performance data that is prestored in the computer. In addition the supervisory computer automatically maintains a minimum flow for the compressor that is as close as possible to the surge limit without danger of putting the compressor into surge due to changes in flow, pressure or molecular weight of the gas being compressed.