Showing papers on "Axial compressor published in 1985"

Loss Reduction in Axial-Flow Compressors Through Low-Speed Model Testing

Abstract: A systematic procedure for reducing losses in axial-flow compressors is presented. In this procedure, a large, low-speed, aerodynamic model of a high-speed core compressor is designed and fabricated based on aerodynamic similarity principles. This model is then tested at low speed where high-loss regions associated with three-dimensional endwall boundary layers flow separation, leakage, and secondary flows can be located, detailed measurements made, and loss mechanisms determined with much greater accuracy and much lower cost and risk than is possible in small, high-speed compressors. Design modifications are made by using custom-tailored airfoils and vector diagrams, airfoil endbends, and modified wall geometries in the high-loss regions. The design improvements resulting in reduced loss or increased stall margin are then scaled to high speed. This paper describes the procedure and presents experimental results to show that in some cases endwall loss has been reduced by as much as 10 percent, flow separation has been reduced or eliminated, and stall margin has been substantially improved by using these techniques.

An Eleven Parameter Axial Turbine Airfoil Geometry Model

Abstract: The mathematical derivation, and FORTRAN code, of a comprehensive but easy to use geometry model for axial flow turbine nozzles and rotors is presented. To uniquely define an airfoil on a cylinder the aerodynamicist need only specify the number of blades, and at each radius of interest: the axial and tangential chord, throat, uncovered turning, leading and trailing edge radii, inlet and exit blade angles, and inlet wedge angle. Default values exist for six of these geometric variables, which proves useful when starting a design. Both the suction and the pressure surfaces are described entirely by analytical functions. Sample airfoils are included that demonstrate the effect of each parameter upon blade shape.Copyright © 1985 by ASME

Three-dimensional unsteady flow in an axial flow turbine

Abstract: The results of an experimental program directed at understanding the unsteady mean and turbulent flow in a large-scale -l-Vi stage research turbine are presented. High response instrumentation and the phase-locked averaging data reduction technique were utilized to acquire data having high spatial and temporal resolution. These data included the unsteady three-dimensional distribution of mean and turbulent velocities and total and static pressures. The data between the guide vane and the rotor and downstream of the rotor are presented herein. The flow downstream of the vane was found to be essentially steady and was dominated by large Reynolds stresses in the wakes and secondary flow regions. In contrast, the flow downstream of the rotor was highly unsteady. Two different rotor exit flow regimes were identified, corresponding to maximum and minimum interaction of the rotor leading edges with the upstream vane wakes. During the maximum interaction, the vane wakes merged with the rotor wakes, the midchannel flow was fairly uniform, and two strong secondary flow vortices were present. During minimum interaction, the vane wakes entered the rotor passages between airfoils, the midchannel flow was nonuniform, and the secondary flow vortices were less well defined.

Axial flow compressor surge margin improvement

Abstract: The casing 28 of an axial flow compressor for a gas turbine engine is provided with a plurality of axially extending circumferentially spaced slots 30 in its internal cylindrical surface 32 adjacent the tips of at least one row of blades 26. A benefit in both stall margin improvement and a reduction in efficiency deficit may be achieved by positioning the leading edge of the slot 30 such that it leads the leading edge 30(a) of the blade 26 by an amount termed the overhang A or by reducing the closed to open ratio m/M of the slots 30. A further reduction in efficiency deficit may be achieved by combining the overhang A which individually gave the best stall margin improvement with a slot closed to open ratio m/M somewhat higher than the value which individually gave the best stall margin improvement.

Investigation of the Three-Dimensional Flow Field Within a Transonic Fan Rotor: Experiment and Analysis

Abstract: An experimental investigation of the three-dimensional flow field through a low aspect ratio, transonic, axial flow fan rotor has been conducted, using an advanced laser anemometer (LA) system. Laser velocimeter measurements of the rotor flow field at the design operating speed and over a range of throughflow conditions are compared to analytical solutions. The numerical technique used herein yields the solution to the full, three-dimensional, unsteady Euler equations using an explicit time-marching, finite volume approach. The numerical analysis, when coupled with a simplified boundary layer calculation, generally yields good agreement with the experimental data. The test rotor has an aspect ratio of 1.56, a design total pressure ratio of 1.629 and a tip relative Mach number of 1.38. The high spatial resolution of the LA data matrix (9 radial x 30 axial x 50 blade-to-blade) permits details of the transonic flow field such as shock location, turning distribution, and blade loading levels to be investigated and compared to analytical results.

A discussion of the factors affecting surge in centrifugal compressors

Abstract: Le processus de pompage dans un compresseur centrifuge depend d'un certain nombre de facteurs complexes et souvent relies entre eux. On propose un modele mathematique plus complexe qu'anterieurement qui est capable de prendre en compte des facteurs additionnels. Bon accord avec les etudes experimentales. Ce modele considere les pertes de charge dans la roue, dans le diffuseur, et dans le collecteur, et il est possible d'identifier les elements de decrochage qui sont responsables de l'instabilite globale du compresseur

Rotor thrust balancing

Abstract: Rotor Thrust Bearing A turbine construction in which the axial loading on the rotor including the compressor and turbine resulting from cooling air pressure in the compartment between the compressor and turbine is balanced by making the compressor and turbine areas exposed to the cooling air of equal area as by having the seals at compressor and turbine ends of the compartment equal in radius with respect to the air of the rotor.

Development of Small Rotating Stall in a Single Stage Axial Compressor

Abstract: In this paper we present the results of a detailed experimental study of the development of small rotating stall, as it appears in a one stage axial compressor. Stationary hot-wire probes are used to measure the variation of amplitude and propagation speed of the disturbances caused by small stall. Measurements near the rotor blade surface with rotating probes provide additional information on the nature of the phenomenon. The development of the cell pattern for different operating conditions is studied. The different character from what is known as “big stall” is demonstrated.Copyright © 1985 by ASME

Control system for compressor motor used with air-conditioning unit

Abstract: A control system for a compressor motor used with an air conditioning unit is disclosed. A current for generating a non-rotating magnetic field is supplied to the compressor motor to preheat a compressor. A current for generating a rotating magnetic field is also supplied to the compressor motor together with the current for generating a non-rotating magnetic field to heat the compressor. The heat pump using this control system is thus capable of transmitting sufficient heat energy immediately after start of the operation of the heat pump.

Visualization of flow patterns in axial flow between horizontal coaxial rotating cylinders

Abstract: The structure of Taylor vortices in the annulus of coaxial horizontal rotating cylinders with and without axial flow was studied by a flow visualization technique based on the colour change of analytical indicators. Flow interaction effects can be characterized by three parameters whose numerical values are obtained from photographs and super 8 mm film strips.

Rotor wake characteristics of a transonic axial flow fan

Abstract: State of the art turbomachinery flow analysis codes are not capable of predicting the viscous flow features within turbomachinery blade wakes. Until efficient 3D viscous flow analysis codes become a reality there is therefore a need for models which can describe the generation and transport of blade wakes and the mixing process within the wake. To address the need for experimental data to support the development of such models, high response pressure measurements and laser anemometer velocity measurements were obtained in the wake of a transonic axial flow fan rotor.

Axial compressor reversed flow performance

Abstract: Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1985.

Inlet Boundary Layer Effects in an Axial Compressor Rotor: Part I—Blade-to-Blade Effects

Abstract: This paper discusses experimental data measured on the blading and downstream of an isolated compressor rotor with thick inlet endwall boundary layers. The objective of the study was to compare these results with data acquired previously with thin inlet boundary layers and to assess the impact of inlet boundary layer thickness on the secondary flow. Flow visualization results showed the powerful impact of the hub corner stall and how at the same near stall flow coefficient where with thin inlet boundary layers the blade was separated at midspan, with thick inlet boundary layers it was attached. It was also shown that while secondary flow was very weak, it did produce sufficient radial redistribution to cause an apparent negative loss at the blade root.

A theory of post-stall transients in multistage axial compression systems

Abstract: A theory is presented for post stall transients in multistage axial compressors. The theory leads to a set of coupled first-order ordinary differential equations capable of describing the growth and possible decay of a rotating-stall cell during a compressor mass-flow transient. These changing flow features are shown to have a significant effect on the instantaneous compressor pumping characteristic during unsteady operation, and henace on the overall system behavior. It is also found from the theory that the ultimate mode of system response, stable rotating stall or surge, depends not only on the B parameter but also on other parameters, such as the compressor length-to-diameter ratio. Small values of this latter quantity tend to favor the occurrence of surge, as do large values of B. A limited parametric study is carried out to show the impact of the different system features on transient behavior. Based on analytical and numerical results, several specific topics are suggested for future research on post-stall transients.

Transient gas turbine engine bleed control

Abstract: Flexibility in the control of the compressor bleed valve is of the type utilized in a twin spool axial flow engine for preventing compressor surge is manifested by electronically summing an approximated rate of change of burner pressure that has a first order time constant introduced to actual burner pressure and a burner pressure limit that is scheduled as a function of corrected high pressure compressor speed and the altitude of the aircraft. The signal may be treated by a hysteresis circuit to stabilize the bleed valve.

Rotor of a compressor, more particularly of an axial-flow compressor

Abstract: The rotor of an axial-flow compressor with means for sealing the rotor blade tips relative to a casing wall provided with a coating is to be capable of abrasion but at the same time also low in wear. The present invention resolves these contradicting requirements for the coating on the casing in that individual blades, arranged between normally contoured, unshrouded rotor blades, are widened at their tips and reinforced with a radially outer layer, the material of which is matched to that of the coating. This will enable the coating to be subjected to less wear and to offer more resistance to erosion than heretobefore.

Axial Flow Contra-Rotating Turbines

Abstract: Two types of contra-rotating stages are considered; the first uses guide vanes and the second is vaneless. The wheels of the first type use bladings which are mirror images of each other and they operate with inlet and outlet swirl. The second type uses dissimilar bladings in each of the two wheels with axial inlet velocity to the first wheel and axial outlet velocity for the second wheel. An analysis of their performance indicates that both types can reach stage loading coefficients comparable or larger than conventional turbines with the same number of wheels. A comparison of the contra-rotating stages with conventional ones indicate a significant stage efficiency advantage of the contra-rotating over the conventional single rotation stages due mainly to the elimination of stationary vanes. The off-design performance indicates that relative wheel speed must be controlled. The attributes of contra-rotating turbines suggest their potential use in high performance aircraft engines, in dynamic space power systems and in low speed industrial gas turbines.Copyright © 1985 by ASME

Advanced Prop-fan Engine Technology (APET) single- and counter-rotation gearbox/pitch change mechanism

Abstract: The preliminary design of advanced technology (1992) prop-fan engines for single-rotation prop-fans, the conceptual design of the entire propulsion system, and an aircraft evaluation of the resultant designs are discussed. Four engine configurations were examined. A two-spool engine with all axial compressors and a three-spool engine with axial/centrifugal compressors were selected. Integrated propulsion systems were designed in conjunction with airframe manufacturers. The design efforts resulted in 12,000 shaft horsepower engines installed in over the installations with in-line and offset gearboxes. The prop-fan powered aircraft used 21 percent less fuel and cost 10 percent less to operate than a similar aircraft powered by turbofan engines with comparable technology.

Inlet Boundary Layer Effects in an Axial Compressor Rotor:Part II-Throughflow Effects

Abstract: This paper presents results of an experimental aerodynamic study conducted in the rotating frame of reference downstream of an isolated compressor rotor with both thick and thin inlet endwall boundary layers. The paper focuses on those aspects of the data having particular significance to the assumptions and application of throughflow theory. These aspects include the spanwise distributions of static pressure and blockage, and the radial redistribution of fluid as it passes through the blade row. It is demonstrated that the main contributions to total pressure loss, blockage, and the distortion of the static pressure field were due to the hub corner stall and tip leakage. This is a significant departure from previous conclusions which looked to the endwall boundary layer and to secondary flow as major loss and blockage producing mechanisms.

Supercharger for automobile engines

Abstract: A supercharger for delivering supercharged air to an engine, comprising a shrouded axial compressor, a radial compressor which is located downstream of the axial compressor and a housing. The housing comprising four sections, including a section defining a highly convergent, frustoconical transition duct which favorably directs the discharge of the axial compressor to the inlet of the radial compressor and a hollow, highly convergent, exhaust cone section immediately downstream of the radial compressor which converges into the exhaust port of the supercharger. An annular flow deflector is provided for directing the discharge of the radial compressor into the exhaust cone.

End-wall and profile losses in a low-speed axial flow compressor rotor.

Abstract: The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor, is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

Use of triple hot wires to measure unsteady flows with large direction changes

Abstract: Geometrical limitations of the probes and inadequate description through the response equations limit existing triple hot wire techniques to measurement in flow fields with small changes in flow direction. A triple hot wire probe together with the related technique is developed to measure in cases where large angular changes occur. Yaw, pitch and velocity parameters are derived as functions of the effective cooling velocities of the hot wires. The dependence of these parameters on flow direction, with respect to the probe, is established through a direct calibration. Uncertainty analysis shows that a wide range of pitch and yaw can be used. Application of the technique in a stalled axial compressor demonstrates the ability to measure mean flow quantities in such cases.

Combined solar power and wind power generator

Abstract: In order to utilise both wind and solar energy the rotor of a wind turbine is provided with photovoltaic cells 19. The turbine may be of an axial flow type (Fig. 1) or vertical axis type (Fig. 2). Pitch varying means and tracking means for turning the turbine to face the sun or into wind may be provided. The turbine can be used on the roof of light cars or on the roofs of buildings for such purposes as airconditioning or refrigeration and it can also be used for irrigation, water pumping etc. In the case of the vertical axis device (Fig. 2) the rotor may be driven by an electric motor (18) powered by the cells (19) instead of the wind acting on vanes (16).

Compressor system and start-up method therefor

Abstract: A compressor system includes a compressor, a turbine for driving the compressor, and an auxiliary burner. Compressed air from an external source is supplied to drive the turbine during start-up. The air compressed by the compressor is then supplied to the auxiliary burner to drive the turbine and the compressed air from the external source is shut-off to keep the compressor system running only by the compressed air from the compressor itself.

An Experimental Study of the Compressor Rotor Blade Boundary Layer

Abstract: The three-dimensional turbulent boundary layer developing on a rotor blade of an axial flow compressor was measured using a miniature 'x' configuration hot-wire probe. The measurements were carried out at nine radial locations on both surfaces of the blade at various chordwise locations. The data derived includes streamwise and radial mean velocities and turbulence intensities. The validity of conventional velocity profiles such as the 'power law profile' for the streamwise profile, and Mager and Eichelbrenner's for the radial profile, is examined. A modification to Mager's crossflow profile is proposed. Away from the blade tip, the streamwise component of the blade boundary layer seems to be mainly influenced by the streamwise pressure gradient. Near the tip of the blade, the behavior of the blade boundary layer is affected by the tip leakage flow and the annulus wall boundary layer. The 'tangential blockage' due to the blade boundary layer is derived from the data. The profile losses are found to be less than that of an equivalent cascade, except in the tip region of the blade.