Showing papers on "Axial compressor published in 1979"

Axial flow in trailing line vortices

Abstract: Axial flow in the core of a laminar steady trailing vortex from the tip of a semi‐infinite wing is analyzed assuming small departure of the axial velocity from the free‐stream velocity. It is further assumed that the axial pressure gradient is determined by the swirl velocities of an ideal infinite line vortex in which the radial and the associated axial velocity variations are neglected in the equation for the angular momentum. The axial and lateral variations of the axial velocity depend on the strength of the vortex and initial axial velocity distribution which must be specified at some station behind the wing except at the virtual origin of the vortex where a nonintegrable singularity exists. Numerical solutions for the axial velocity are obtained using the axial pressure gradient given by the line vortex and analytical solutions are obtained using an equivalent axial pressure gradient with good agreement between the two sets of axial velocity distributions. Resolution of the previous uncertainties in this field is given which were due to the unrecognized singularity at the virtual origin of the vortex. Using the calculated axial velocity the neglected radial and the associated axial fluxes of angular momentum are determined and the limits of validity of the theory presented here in terms of a suitably defined vortex Reynolds number and a nondimensional distance measured from the virtual origin of the vortex are given.

Active clearance control system for a turbomachine

Abstract: An axial compressor is provided with a cooling air manifold surrounding a portion of the shroud, and means for bleeding air from the compressor to the manifold for selectively flowing it in a modulating manner axially along the outer side of the stator/shroud to cool and shrink it during steady-state operating conditions so as to obtain minimum shroud/rotor clearance conditions. Provision is also made to selectively divert the flow of cooling air from the manifold during transient periods of operation so as to alter the thermal growth or shrink rate of the stator/shroud and result in adequate clearance with the compressor rotor.

The Effect of Temperature Gradient on the Stability of Flow between Vertical, Concentric, Rotating Cylinders

Abstract: The effect of a radial temperature gradient on the hydrodynamic stability in the annular gap formed by two, vertical, concentric cylinders, the inner being rotatable and the outer both stationary and isothermally heated, was studied for the cases of zero and imposed axial fluid flow in the annular gap. For zero axial flow, it was found that the temperature gradient destabilizes the flow while not affecting the form of the secondary flow, viz. the classic Taylor vortex. For imposed axial flow, the point of neutral stability was modified only when natural convection was strong enough to affect the parabolic velocity profile associated with that flow; the extent of this modification was shown to depend on the direction of the axial flow. Also, the longitudinal temperature gradients within the gap were found to influence the axial wave number and the drift-velocity ratio.

Broad spectrum vibration damper assembly fixed stator vanes of axial flow compressor

Abstract: Undesirable vibrations of stator airfoil vanes circumferentially disposed in annular rows, and fixed at their ends by a sectored outer shroud and a sectored inner shroud, in an axial flow compressor of gas turbine engine are damped by a damper assembly that is fitted into, and is frictionally engaged, in the sectored inner shroud which, in turn, is segmented to assist in this damping. The damper assembly includes: A metal seal strip member having indentations; a metal sine wave-shaped damper and spring member that is complementary to, and is engaged with, the seal strip member; and, a honeycomb member affixed to the bottom surface of the seal strip member. The vibrations cause movement of the shroud segments which, in turn, cause rubbing contact; and, the resulting friction heat energy is conducted through the metal components of the damper assembly to the thermal sink that is the through-flowing air in the compressor.

Dynamics of Flexible Cylinders in Axisymmetrically Confined Axial Flow

Abstract: Experiments are described in which flexible cylinders placed centrally within a narrow cylindrical flow channel were subjected to axial flow. The dynamic behavior of such cylinders, either cantilevered or supported at both ends, is described, both in liquid and in simulated two-phase flows; the effect of several parameters, such as the annular confinement, was investigated. It was observed that, with increasing flow, the cylinder is subject sequentially to instabilities of increasing mode number, confinement severely destabilizing the system. The experimental observations are compared to a theoretical model for the dynamics of such systems. In the case of liquid flow, agreement is qualitatively good and quantitatively fair - keeping in mind the experimental difficulties. In the case of two-phase flows, theory and experiment do not agree.

Control systems for multi-stage axial flow compressors

Abstract: A control system is provided for the multi-stage axial flow compressor of a gas turbine engine. The control system embraces a stage of variable angle guide vanes, a first detector adapted to detect a first pressure in the compressor which is influenced by the vane angular setting, and a second detector adapted to detect a second pressure independent of the vane setting but bearing a functional relationship to the rotational speed of a compressor of the engine. A control unit is adapted to use the pressures detected by the detectors to cause an actuation mechanism to adjust the angular setting of the guide vanes in a predetermined manner dependent upon the ratio of the second pressure to the first pressure.

Climatizing of aircraft

Abstract: An aircraft cabin is climatized by tapping air from the engine compressors and feeding it into the cabin through a loop which includes a compressor, a cooling turbine driving the compressor, and several cooling stages. A second loop, using preferably helium, includes a second compressor and a second turbine, the second compressor being driven by both turbines, and the cooled helium is in heat exchange with another cooling loop which runs through instrument compartments. Discharged cabin air is used to precool the compressed helium.

Compressor structure adapted for active clearance control

Abstract: A compressor structure for a gas turbine engine capable of enhanced active clearance control within the compressor is disclosed. Various construction details which enable the discharge of cooling air against the compressor case and which minimize thermal distortion of the case are developed. The concepts are applied to a longitudinally split compressor case and include an external bleed manifold of circular cross section which extends across the longitudinal split in the case. Cooling air is dischargeable beneath the manifold to cool the case structure. Heat shields are provided in access ports to the manifold to inhibit heat transfer to the compressor case at the local regions of the ports.

Core compressor exit stage study, 2

Abstract: A total of two three-stage compressors were designed and tested to determine the effects of aspect ratio on compressor performance. The first compressor was designed with an aspect ratio of 0.81; the other, with an aspect ratio of 1.22. Both compressors had a hub-tip ratio of 0.915, representative of the rear stages of a core compressor, and both were designed to achieve a 15.0% surge margin at design pressure ratios of 1.357 and 1.324, respectively, at a mean wheel speed of 167 m/sec. At design speed the 0.81 aspect ratio compressor achieved a pressure ratio of 1.346 at a corrected flow of 4.28 kg/sec and an adiabatic efficiency of 86.1%. The 1.22 aspect ratio design achieved a pressure ratio of 1.314 at 4.35 kg/sec flow and 87.0% adiabatic efficiency. Surge margin to peak efficiency was 24.0% with the lower aspect ratio blading, compared with 12.4% with the higher aspect ratio blading.

Gas turbine power plant with air reservoir and method of operation

Abstract: A gas turbine power plant is disclosed which uses gas turbine engine components in conjunction with an air reservoir and a motor-generator. The compressor unit has low pressure, intermediate pressure and high pressure compressors and control valves which allow operation of the low pressure compressor by a low power auxiliary motor during starting while the other compressors do not absorb significant power. The power plant can operate by the motor-generator to charge the reservoir, can operate on the air cell with a turbine during peak load, and can function as a conventional gas turbine installation when the air reservoir is exhausted.

Turbine rotor assembly

Abstract: Components of a rotor assembly which is capable of long term reliable operation in an axial flow gas turbine engine environment are disclosed. Various construction details enabling good low cycle fatigue life by reducing stress concentrations in the rotor disk are disclosed. Rotor disk and blade features are combined to provide a seal land on the rotor assembly without the need of disk sideplates.

Silencing system for axial flow fan - has glass wool lined duct with resonator tubes tuned to absorb sound of different frequencies

Abstract: An axial flow fan (12) driven by an electric motor (7) is mounted in a duct (1) The duct is lined with fibre glass supported by a hollow cone of perforated metal The motor cooling air flows through an inner duct which is surrounded with fibre glass (10) The axial gap between the fan blades (13, 14) and the outlet guide-vanes (22) minimises the noise generated by the blades A conical guide (25) is fitted downstream of the fan and carries a number of resonator tubes (30) which can be tuned to absorb all the frequencies generated by the fan

Single rotor engine with turbine exhausting to subatmospheric pressure

Abstract: An automotive single shaft gas turbine engine has a monorotor with a plurality of radial flow compressor blades thereon discharging compressed air to a recuperator for transferring heat from engine exhaust to the inlet combustion air to a combustor which produces motive fluid directed across a plurality of radial inflow turbine vanes on the monorotor and wherein the automotive gas turbine engine is further associated with an exhaust flow system including the regenerator, a series connected intercooler and a secondary compressor to produce a subatmospheric pressure source in the engine gas cycle to improve the thermal efficiency of the engine cycle and to further define a vacuum source for operating automotive accessories; and to provide a heat source at subatmospheric pressure for passenger compartment heater operation. The subatmospheric source is connected to the secondary compressor which is operative to compress turbine exhaust gas back to one atmosphere of pressure for discharge to the environment. The secondary compressor and the inlet compressor establishing a pressure build-up and pressure depression in the system which in one embodiment is across a series arranged, two-stage radial and axial turbine to produce an overall turbine pressure ratio for increasing the temperature drop across the turbine thereby to decrease work load of the downstream heat exchanger components between the outlet of the turbine stages and the secondary compressor.

An Experimental Investigation of the Stability of Spiral Vortex Flow

Abstract: The hydrodynamic stability of the flow in an annular gap, formed by a stationary outer cylinder and a rotatable inner cylinder, through which an axial flow of air can be imposed, is studied experimentally. Two annulus radius ratios of 0.8 and 0.955 are considered, representing wide- and narrow-gap conditions, respectively. It is shown that, when a large, axial pressure gradient is superimposed on the tangential flow induced by the rotation of the inner cylinder, the characteristics of the flow at criticality change significantly from those at zero and low axial flows, the axial length and width of the resultant spiral vortex departing greatly from the known dimensions of a Taylor vortex cell at zero axial flow. Also, the drift velocity of the spiral vortex is found to vary with the axial flow. Axial Reynolds numbers, Rea, of up to 700 are considered.

Basic Studies of Rotating Stall in Axial Flow Compressors.

Abstract: : This report presents the results of a theoretical and experimental program aimed at obtaining a sufficient understanding of the rotating stall phenomena such that its onset and properties can be predicted under a wide set of circumstances. The theoretical research covers the development of two-dimensional stability theories for compressible flows and the progress towards the development of a three-dimensional theory for incompressible flow. The experimental work, performed in an annular cascade facility, studied the effects of rotorstator interference both on the steady-state performance of the blade rows and on rotating stall. The influence of circumferential distortion on the rotating stall boundary for the stage was also determined. Comparisons are made between the experimental results and the predictions of a two-dimensional rotating stall stability theory which had been developed previously for incompressible flows. (Author)

Axial Compressor Blade Optimization in the Low Reynolds Number Regime

Abstract: Original and previously published experimental data are presented in this study of axial compressor blade optimization for use in the subcritical Reynolds number region. Three methods of increasing cascade performance at these low Rc are presented, discussed, and compared: 1) the use of sharp, leading-edge profiles, 2) trip wires or roughness elements, and 3) high freestream turbulence. The original data were collected in the VKI C-l cascade wind tunnel; during these tests, blade chord Reynolds number was varied from 250,000 down to -17,000. Each technique demonstrated an increase in low Rc performance for certain profiles, with the sharp, leading-edge profile as the potential optimum. Axial compressors or pumps that must operate for a significant amount of their design life under low Reynolds number conditions might benefit substantially from these methods.

Rotary fluid device

Abstract: A multiple stage energized fluiel flywheel is contained within a housing. An axially extending shaft is rotatably mounted within the housing. Fluid is introduced into the unit through an initial axial flow section and further pressure increases are experienced in a radial blower section and an annular squirrel cage section peripherally arranged about the radial blower. Pressurized fluid discharged from the squirrel cages is directed to either a peripheral exhaust ring which discharges pressurized fluid to the reservoir interior or to an adjacent hydraulic motor. The hydraulic motor includes a rotor which is secured to the stator section of the initial axial pumping section. The axial shaft, radial blower, squirrel cage and exhaust section rotate as a unit in one direction of operation. The hydraulic motor and axial pumping section stator rotate as a unit in the opposite direction of rotation. The flywheel may operate using air, hydraulic fluid or other motive fluids. Several flywheel units may be mounted in a balanced arrangement on a single shaft within an enclosure.

The effects of some design parameters of an isolated rotor on inlet flow distortions

Abstract: A study of the effects of rotor-blade geometry, steady loading, and distortion wavelength on the distortion flow field upstream and downstream of an unstalled isolated rotor shows that the attenuation of the distortion as it passes through the rotor is a function of the blade stagger angle and the distortion-reduced frequency or the ratio of rotor blade spacing to the distortion wavelength. Maximum attenuation occurs when this ratio is 0.5 and increases with increasing stagger angle. Little influence of rotor incidence angle or steady loading was observed.

Thermal Influences in Gas Turbine Transients: Effects of Changes in Compressor Characteristics

Abstract: During transients of axial-flow gas turbines, the characteristics of the compressor are altered. The changes in these characteristics (excluding surge line changes) have been related to transient heat transfer parameters, and these relations have been incorporated in a program for predicting the transient response of a single-shaft aero gas turbine. The effect of the change in compressor characteristics has been examined in accelerations using two alternative acceleration fuel schedules. When the fuel is scheduled on compressor delivery pressure alone. there is no increase in predicted acceleration times. When the fuel is scheduled on shaft speed alone, the predicted acceleration times are increased by about 5 to 6 percent.Copyright © 1979 by ASME

Determination of the Reynolds-Stress Tensor With a Single Slanted Hot-Wire in Periodically Unsteady Turbomachinery Flow

Abstract: The pitchwise distribution of the components of the Reynolds stress tensor downstream of a rotating blade row can be obtained with a single slanted hot-wire and the technique of periodic sampling and averaging. The requirements imposed on the hot-wire and the sensitivity coefficients to the six stresses are given. Information concerning the electronic set-up and the problems associated with measuring the Reynolds stresses are discussed. It is shown that the sampling technique does not modify the mean square value of the sampled signal if the correlation time of the turbulence is smaller than half the sampling rate, or when the frequency bandwidth of the turbulence is higher than twice the sampling frequency. Typical results, including the 3D-mean flow data obtained downstream of a low-speed axial compressor rotor at different radii are presented. The results show typical modifications of the stresses in the rotor wake region and the regions influenced by secondary flow or tip-leakage flow.Copyright © 1979 by ASME

Wide range compressor

Abstract: This wide range compressor has a casing forming a passage with an inlet and an axial portion, and a rotor with blades extending into the passage and functioning, when the rotor operates, to draw air into the inlet and force it through the passage. One of the problems with wide range compressors is a variation of the pressure as the volume changes rather than maintaining a desired constant or substantially constant discharge pressure. To solve this problem, the present compressor is provided, first, with a ring in the inlet to divide the flow into inner and outer annuluses and, second, with vane or other elements positioned and operative to vary one of the flow annuluses to maintain the output pressure of the compressor substantially uniform over the complete range. The concept embodied in the additional structure disclosed herein is applicable to fans, blowers, compressors, and pumps of axial, centrifugal, or mixed flow configurations which often have difficult wide range requirements.

Axial-flow turbine

Abstract: An axial-flow turbine which is driven by a working fluid which contains dust and moisture is disclosed. The turbine has stator blade means and rotor blade means, and a working fluid exit angle of a first-stage stator blade means is smaller than that of the second-stage stator blade, wherein the absolute exit velocity of the working fluid from the first stage stator blade means is smaller than that of the second stage stator blade means, whereby the flow of the working fluid has the same directional vortical flow with the turbine shaft as the axis of the vortex and dust fouling is checked particularly in connection with the first-stage stator blade means.

Design and Performance Evaluation of Supercritical Airfoils for Axial Flow Compressors..

Abstract: : Pratt & Whitney Aircraft has developed an analytical design procedure for producing supercritical cascade airfoils satisfying practical aerodynamic and structural requirements The purpose of this research is to demonstrate the potential for substantial efficiency improvements in compressor stages incorporating these airfoil designs The midspan section of a fan exit stator was selected for the design application An airfoil was designed, fabricated, and tested in a transonic cascade tunnel Test conditions were varied over a wide range of inlet flow angles and inlet Mach numbers to determine design and off-design performance Test point information included inlet and exit conditions and airfoil surface pressure distribution