Showing papers on "Axial compressor published in 1981"

Experimental and Theoretical Study of Surge in a Small Centrifugal Compressor

Abstract: Experimental results for deep surge in a small single-stage centrifugal compressor are compared to predictions based on the lumped parameter Greitzer model developed for axial compressors. Both negative and positive flow branches of the steady characteristic, being essential for the model, were measured. Predictions are in fair agreement with data when using a relaxation time smaller than the one proposed for axial compressors. The stability limit of the model equations have been studied for finite amplitude disturbances.

Stalling Pressure Rise Capability of Axial Flow Compressor Stages

Abstract: A procedure for estimating the maximum pressure rise potential of axial flow compressor stages is presented. A simplified stage average pitchline approach is employed so that the procedure can be used during a preliminary design effort before detailed radial distributions of blading geometry and fluid parameters are established. Semi-empirical correlations of low speed experimental data are presented that relate the stalling static-pressure-rise coefficient of a compressor stage to cascade passage geometry, tip clearance, bladerow axial spacing and Reynolds number. Blading aspect ratio is accounted for through its effect on normalized clearances, Reynolds number and wall boundary layer blockage. An unexpectedly strong effect of airfoil stagger and of the resulting flow coefficient of the stage’s vector triangle is observed in the experimental data. This is shown to be caused by the differing ability of different types of stage vector triangles to re-energize incoming low-momentum fluid. Use of a suitable “effective” dynamic head in the pressure rise coefficient gives a good correlation of this effect. Stalling pressure rise data from a wide range of both low speed and high speed compressor stages are shown to be in good agreement with these correlations.

Compressor-simulation model with corrections for the level of suction gas superheat

Abstract: A compressor simulation model, based on empirical performance curves from reciprocating compressor manufacturers, is discussed. The compressor model is part of a heat pump simulation model being developed for potential use in reducing the amount of testing required for air-to-air heat pumps by the new rating procedures being implemented by DOE. Corrections to the compressor performance curves (maps) are developed to account for the effect of different superheat (or quality) levels on refrigerant mass flow rate and compressor power; the corrections are in general agreement with the average of the available information from manufacturers of two- to four-ton, R-22, hermetic, reciprocating compressors. Comparisons are made between the compressor model predictions and available data from four heat pump experiments. The comparisons indicate that more experimental data are needed at the lower ambient conditions in the heating mode under conditions of wet suction gas and with lower air temperatures over the compressor shell.

Laser Anemometer Measurements in a Transonic Axial Flow Compressor Rotor

Abstract: A laser anomometer system employing an efficient data acquisition technique has been used to make measurements upstream, within, and downstream of the compressor rotor. A fluorescent dye technique allowed measurements within endwall boundary layers. Adjustable laser beam orientation minimized shadowed regions and enabled radial velocity measurements outside of the blade row. The flow phenomena investigated include flow variations from passage to passage, the rotor shock system, three-dimensional flows in the blade wake, and the development of the outer endwall boundary layer. Laser anemometer measurements are compared to a numerical solution of the streamfunction equations and to measurements made with conventional instrumentation.

Turbine set with a generator feeding a network of constant frequency

Abstract: In a turbine set with an axial flow which is traversed by water and which is coupled to a generator feeding a network of constant frequency, the flow turbine is a propeller turbine with non-adjustable blades. The stator winding of the generator is connected to the network by means of a frequency-controllable converter, in particular a direct converter. The speed of rotation of the turbine set is controllable continuously according to the power to be delivered. In the case of an asynchronous design of the generator, it is advisable to provide the stator with a waterproof jacket on the inside and to flange it into the turbine tube, since the rotor with its cage winding is swept by water.

System for cooling a gas turbine by bleeding air from the compressor

Abstract: A system for cooling a gas turbine by bleeding air from the compressor and channeling the air at the center of the engine towards the turbine in order to cool it. The air is bled from the plane of the disc bearing the blades of the compressor, said disc having radial ducts for the flow of the air. The invention is utilized in gas turbine engines to cool the turbine.

Compact scroll-type fluid compressor with swing-link driving means

Abstract: A compact scroll compressor capable of maintaining a high efficiency when driven at variable speeds and operating at variable gas pressures. The compressor incorporates a unique swing-link driving means and means to control the flow of high-pressure fluid from the central high-pressure zone defined by the scroll members. The compressor is particularly suited for operation off an automotive engine to provide compressed refrigerant in an automotive air conditioner.

Bleedoff of gas diffusers in fluid flow machines

Abstract: In a fluid flow machine comprising a compressor including a compressor diffuser and a turbine including an exhaust gas diffuser compressed air from boundary layers or vortex flows in the compressor diffuser, or leakage air from the compressor, is bled off and used as a driving medium for removing exhaust gas from boundary layers or vortex flows in the exhaust gas diffuser. Since the pressure of the exhaust gas to be removed from the exhaust gas diffuser is below the ambient pressure a suction has to be established to remove the desired gas from the boundary layers or vortex flows. This suction is established by an ejector or a pump which is driven by the energy of the compressed air bled from the compressor regions.

Flow in Transonic Compressors

Abstract: Introduction B the term transonic compressor we mean an axial flow compressor in which the inlet flow Mach number, relative to the rotating blades, varies from below unity at radii near the inner casing or hub to values substantially above unity at radii near the blade tips. Usually the flow is diffused to subsonic velocities in the flow passages formed by the rotating blades, generating part of the desired pressure rise. A further pressure rise is generated in a stationary blade row downstream of the rotor in the process of removing the swirl imparted by the rotor, but the flow Mach numbers relative to the stator blades are generally below unity. Thus, the flows of principle concern here are those in the rotor passages. Axial flow compressors have been the subject of research and development efforts for at least 40 years, and the transonic compressor for nearly 30. The earliest systematic studies in the United States were carried out by the Lewis Research Center of the NACA about 1950, and the technology was quickly developed for application in the first generation of turbofan engines. Because it offers higher pressure ratios per stage and larger airflows per unit of engine frontal area than the subsonic compressor, the transonic compressor has become a major component of all modern aircraft engines. It has received a proportionately large share of the huge research and development effort expended on these engines. The opinion has often been proffered that it represents a highly developed technology which will not yield significant gains from additional research and development. I argue to the contrary, that there is much scope for improvement in the design of these important components, and that the capability for making these improvements is rapidly coming to hand. This position rests on several facts. First, there are large inefficiencies in transonic compressors due to the three-dimensional character of the inviscid and viscous flows and their coupling. Second, the design methods currently in use do not deal rationally with these loss mechanisms. Third, until recently there has not been a capability for measuring the actual flow in the rotor passages to provide feedback to the design process. The designer has had to rely on overall performance measurements and timeaveraged measurements between the blade rows for verification of the design process. We now have several diagnostic methods capable of providing detailed information about the flow in the blade passages. These include laser velocimetry, gas fluorescent density measurements, and timeresolved pressure measurements, as well as the time-honored hot-wire anemometer. We also have a capability for numerical computation of the three-dimensional transonic flow, inviscid at present but with viscous effects in the near future. Turbomachinery should be one of the major beneficiaries of the advances in this area as was discussed by Chapman in last year's Dryden Lecture. Taken together, the problem of the transonic compressor and these new engineering tools represent an opportunity quite comparable to that presented by recent improvements in high-speed airfoil sections, together with three-dimensional computational techniques in external aerodynamics. My objectives in this paper are to describe the role of the technology and its status, discusss some recent progress toward understanding the flowfield, and indicate the directions which I feel future work should take. I do so with the full knowledge that some of my colleagues in industry and government have much more experience in the design of compressors than I, and that I may not fully represent their viewpoint. My hope is that the view expressed here will prove complementary to that of practicing engineers, and have some beneficial effect on future fan and compressor designs. This review will deal mainly with the question of efficiency. There are many other important problems in the design of transonic compressors, including flutter and forced vibration, stall and surge, foreign object damage, and noise. Some will be mentioned as they impinge on the issue of design for high efficiency, but only the latter will be discussed in detail. Apart from the necessity for focusing on one of these many issues in order to achieve the depth appropriate to a Research Lecture, this choice is motivated by the perception that efficiency is the

Computer program for aerodynamic and blading design of multistage axial-flow compressors

Abstract: A code for computing the aerodynamic design of a multistage axial-flow compressor and, if desired, the associated blading geometry input for internal flow analysis codes is presented. Compressible flow, which is assumed to be steady and axisymmetric, is the basis for a two-dimensional solution in the meridional plane with viscous effects modeled by pressure loss coefficients and boundary layer blockage. The radial equation of motion and the continuity equation are solved with the streamline curvature method on calculation stations outside the blade rows. The annulus profile, mass flow, pressure ratio, and rotative speed are input. A number of other input parameters specify and control the blade row aerodynamics and geometry. In particular, blade element centerlines and thicknesses can be specified with fourth degree polynomials for two segments. The output includes a detailed aerodynamic solution and, if desired, blading coordinates that can be used for internal flow analysis codes.

Multi-stage centrifugal compressor

Abstract: A centrifugal air compressor (11) has an annular air flow path (14) of progressively increasing diameter and progressively diminishing cross-sectional area in which a plurality of internal compression-diffusion stages (30) are provided. The stages of progressively greater diameter are defined by rows (29) of impeller (12) blades which are alternated with rows (32) of stator blades along the air flow path (14) and each such blade row (29, 32) has a diffusion factor below about 0.55 and a de Haller number above about 0.70. The multi-staged construction combines higher isentropic efficiency with reduced size and may be used as a component of a gas turbine engine (18) or a turbocharger (57) or for other purposes requiring gas compression.

Velocity Field and Entrainment of a Pulsed Core Jet

Abstract: A pulsed core jet is one consisting of a steady annular flow with a core, the mass flow of which is unsteady. The combined jet exhausts into a still environment. The velocity field and entrainment characteristics for such a jet have been measured for various mass flow ratios of pulsed-to-steady flow and several frequencies of pulsation. Results show the radial distribution of mean velocity to be similar to those of steady jets except very close to the nozzle, the decay of the centerline mean velocity to be less than that of steady jets, and the entrainment to be larger than that of steady jets but less than fully pulsed ones. No significant sensitivity to frequency of pulsation was observed, but the velocity field is strongly dependent on the ratio of core flow to annular flow.

Turbomachinery: Basic theory and applications

Abstract: "Types of Turbomachines Basic Relations Dimensionless Quantities Centrifugal Pumps and Fans Centrifugal Compressors Axial-Flow Compressors, Pumps, and Fans Radial-Flow Gas Turbines Axial Flow Gas Turbines Steam Turbines Hydraulic Turbines Wind Turbines Appendixes "

Analysis of Turbulent Boundary Layer on Cascade and Rotor Blades of Turbomachinery

Abstract: The momentum integral technique for predicting the boundary-layer growth in three-dimensi onal flow has been extended to include the entrainment equation as the closure model. The numerical solution is compared with the cascade, inducer, compressor, and fan rotor blade data from various sources. The agreement is found to be excellent in all cases, with the exception of the separated flow. Both the momentum thickness and the limiting streamline angle predicted from this analysis compare well with the measured data for a rotor blade. The technique is extremely useful in engineering design, analysis, and performance prediction.

Diffuser for gas turbine engine

Abstract: In a gas turbine engine having an annular combustor and an axial flow compressor discharging compressed air through a discharge annulus upstream of said combustor, the diffuser being supported on the engine independently of the combustor between the discharge annulus and a dome on the combustor and including inner and outer walls operative to direct first and second portions of compressor discharge to radially inner and outer air plenums at the combustor and a remaining third portion of compressor discharge flow to a combustor dome feed chamber ahead of the dome, an improvement in the form of radially oriented pins on the diffuser and guides on the combustor dome slidably received on the pins, the pins and guides cooperating in maintaining a predetermined positional relationship between the diffuser and the combustor during relative thermal growth of the latter whereby at normal operating temperature the diffuser outer wall seals against the combustor while a flow balancing slot is developed between the diffuser inner wall and the combustor.

Linear Stability Theory of Boundary Layer along a Cone Rotating in Axial Flow

Abstract: A linear stability theory is treated for an incompressible laminar boundary layer along a cone rotating about its axis of symmetry with a constant angular speed in an external forced flow field. Small perturbations are assumed to be of spiral vortices. This leads to one set of perturbation equations including an order of magnitude (δ1/R0), where δ1 denotes a displacement thickness of the boundary layer, calculated from a velocity component in the meridional section, and R0 is a local radius of the cone at instability. A numerical procedure for solving the eigenvalue problem is shown. As an example, calculations are carried out for a cone having a total included angle of 30° at a rotating speed ratio 3, where the rotating speed ratio is defined as the ratio of the circumferential velocity at the cone surface to the external flow velocity at the outer edge of the boundary layer. From stability diagrams obtained herein, critical Reynolds number, spiral angle and the associated eigenvalues are determined. The critical Reynolds number is compared with an experiment.

Efficient Laser Anemometer for Intra-Rotor Flow Mapping in Turbomachinery

Abstract: A fringe type laser anemometer is described. Features of the anemometer include; a rapid and efficient data acquisition process; a detailed real time graphic display of the data being accumulated; and input laser beam positioning that maximizes the size of the intrarotor region being mapped. Results are presented that demonstrate the anemometer's capability in flow mapping within a transonic axial flow compressor rotor. A velocity profile, derived from 30,000 measurements along 1000 sequential circumferential positions covering 20 blade passages, was obtained in 30 seconds. The use of fluorescent seed particles allowed flow measurements near the rotor hub and the casing window.

Apparatus for minimizing and maintaining constant the blade tip clearance of axial-flow turbines in gas turbine engines

Abstract: Apparatus and method for minimizing and maintaining substantially constant the effective blade tip clearance between the outer free ends of rotor blades and an adjacent casing shroud of an axial-flow turbine of a gas turbine engine. The casing shroud includes a portion facing the hot gas stream and the outer rotor blade ends and a packing of high heat-resistance, high erosion-resistance ceramic elements secured to the shroud via a metal ring to face the blade tips. A heat insulator is interposed between the packing and the metal ring. A perforated conduit is mounted outside the metal ring for blowing cooling fluid against the metal ring on the side thereof remote from the insulator for equalizing the expansion of the metal ring to that of the turbine wheel. The ceramic packing includes projections facing the outer ends of the blades which are tapered so that they are easily broken off when coming into contact with the blades during running-in of the apparatus.

Propulsion and Energetics Panel Working Group 12 on through flow calculations in axial turbomachines

Abstract: : The objectives of these efforts were to review the existing information on blade performance and wall effect prediction, and to extend this information by systematic application of numerical methods to representative geometries. In its performance period Working Group 12 had confined to axial turbomachines only and split into a Turbine Sub-Group and a Compressor Sub- Group. In the Turbine Sub-Group five correlations were reviewed and evaluated against the test cases. Each correlation had its strengths and weaknesses and room for further improvements. The Compressor Sub-Group report begins with a comprehensive survey of the various loss and deviation mechanisms. For comparison of the prediction methods to the test cases five authors have used their own correlations, while the sixth employed a single code in conjunction with three correlations for the four stage compressor. The results of the evaluation are similar to those of the Turbine Sub-Group, but the spanwise parameter distribution is often poorly predicted. This Advisory Report was prepared at the request of the Propulsion and Energetics Panel of AGARD.

Automatic natural gas compressor control system

Abstract: A control system for a compressor utilized in transferring natural gas from relatively low pressure wells to a relatively high pressure pipe line incorporating automatic shutdown of the compressor and automatic restart of the compressor in response to certain conditions with the compressor operating at a desired flow rate regardless of upstream fluctuations in pressure. The compressor is unloaded upon shutdown and remains unloaded for a timed duration after startup thereby reducing the required motor size, compressor wear and also eliminating manual startup for most of the usual causes of gas compressor shutdown, such as low well pressure and high discharge line pressure.

New Features in the Design of Axial-Flow Compressors With Tandem Blades

Abstract: A multitude of examinations and studies of compressor blades with 100 percent reaction have shown that tandem blades can advantageously be used in stationary industrial axial flow compressors, designed for applications in the chemical, iron and steel industries. Because there are no limitations for axial flow compressors with tandem blades, this type of compressor can operate up to maximum pressure ratios of 10 for suction volume flow of about 600,000 m3 /h. In particular, the handling of light gases, such as helium, leads also to large sizes. Based on measurements taken on a four-stage experimental compressor, criteria are developed for the design of axial flow compressors with tandem blades. The basic concept of a multi-stage industrial compressor provides for the combined arrangement of compressor stages of single and tandem-cascade design. This permits an optimum performance to be achieved at a considerable reduction of the constructional expenditure.Copyright © 1981 by ASME

A Study of Diffuser/Rotor Interaction in a Centrifugal Compressor:

Abstract: Experimental flow data recorded on a low speed centrifugal compressor rig are compared with theoretical predictions of the diffuser field. Results for four diffuser geometries are presented coverin...

Linearized analysis of the three-dimensional compressible flow through a rotating annular blade row

Abstract: Linearized solutions for the flow field of a rotating blade row in an infinitely long annular duct are reviewed. An isolated rotor is assumed to operate in a uniform axial flow so that the disturbance field is steady in a blade fixed co-ordinate system. Both three-dimensional and compressibility effects are included, but attention is confined to subsonic flows. Previously published source-flow solutions omitted a term which affected the thickness part of the rotor flow field constructed from them. Corrected source and rotor-thickness solutions are given, and then the source or monopole solution is used to form a pressure dipole solution. The rotor-loading contribution to the flow field is found by superposition of the revised dipole solutions. The present version of the dipole representation of the steady-loading field is shown to be equivalent to an existing vortex representation, but different from an existing dipole representation. The behaviour of the blade-surface pressure and velocity distributions is described for both the thickness and loading cases. Sample numerical evaluations of the surface quantities are presented.

Nozzle for a coolable rotor blade

Abstract: A coolable rotor stage assembly 14 of the turbine 10 of an axial flow gas turbine engine is disclosed. A cavity 18 for purge air is adjacent the rotor disk 22. A nozzle 34 for metering the flow of cooling air through the rotor blade, for forming a jet of high velocity air and for directing the cooling air from the root of the rotor blade inhibits recirculation, retards formation of the radial pumping boundary layer, decreases the thickness t of the radial pumping boundary layer and does work on the rotor blade.

Balanced bladed rotor

Abstract: A bladed rotor assembly, such as a multi-stage compressor of an axial flow turbofan aeroengine, has at least one stage of rotor blades 23 whose root portions 43 have holes 55 extending through them. Selected blades are provided with means for balancing the rotor assembly comprising plug weights 58 which are adhesively retained in the holes 55.

The Radial Turbine

Abstract: The radial, or centripetal, turbine is used for very small flows, where it is cheaper and simpler to make than an axial flow turbine. It is used in the smallest gas turbine engines, as in some automotive or fire pump or other portable applications, and is used extensively in the smaller turbochargers. It is also suitable for turbo-expansion applications (section 2.9). Its size ranges up to about 0.15 m diameter, and its rotational speed is likely to be between 60 000 and 100 000 rev/min.