Showing papers on "Axial compressor published in 1976"

Axial-flow fan

Abstract: An axial flow fan includes a plurality of auxiliary blades disposed upon and projecting from the suction and/or pressure surfaces of primary fan blades radially disposed on a hub member The auxiliary blades extend substantially in the width direction or transversely of the primary blades, and the leading edges of the auxiliary blades, as viewed in the rotational axis direction of the fan, are disposed closer to the rotational center of the hub member than the trailing edges of the auxiliary blades In this manner, the axial flow fan produces an axial fluid flow by means of the primary blades and a radial fluid flow by means of the auxiliary blades

Gas turbine engine with improved compressor casing for permitting higher air flow and pressure ratios before surge

Abstract: A plurality of skewed slots of a particular shape are provided within a compressor casing adjacent at least one stage of compressor blade tips, the slots having an axial length greater than that of the adjacent blade tips. The slots are provided such that upon occurrence of compressor surge or stall, the stagnating air occurring about the blade row may be directed by the slots downstream of the compressor blade row back into the main stream of fluid passing through the compressor. By such an arrangement, the slots provide a compressor in which the air flow and pressure ratio may be increased before reaching compressor stall or surge.

Three Dimensional Characteristics of Turbulent Wakes Behind Rotors of Axial Flow Turbomachinery

Abstract: Analytical and experimental investigations of the characteristics of three-dimensional turbulent wakes downstream of a turbomachinery rotor are reported in this paper. An approximate quasi-three-dimensional turbulent wake model for turbomachinery rotor is developed and compared with the cascade and isolated airfoil wake models. The rotor wake model is capable of predicting the decay of mean component of radial and streamwise velocities as a function of rotor geometry, speed of rotation, and the turbulence properties of the flow field. A rotation parameter based on similarity analysis is derived. The velocity profiles in both the radial and cylindrical planes are coupled together. Measurement of mean velocities (Un , Us , Ur ), turbulent intensities and stresses (un2, us2, ur2, usun, unur, usur) is carried out using a triple sensor hot wire probe in a stationary system at various axial and radial locations downstream of the rotor. Profiles of mean and turbulent quantities are obtained. Semi-theoretical expressions for the decay rates of the defect in mean velocity, turbulence intensity, and Reynolds stress (maximum values) with distance downstream of the rotor are derived. The experimental data on the rotor wake are compared with that of an isolated airfoil and cascade of airfoils. The investigation suggests that rotor wake decays much faster than the cascade or an isolated airfoil wake.

Diaphragms for axial flow fluid machines

Abstract: A diaphragm for an axial flow fluid machine comprising inner and outer walls for defining an annular fluid flow passage therebetween, a blade lattice having a plurality of stationary blades disposed in the fluid flow passage, each of the blades having a concave side surface and a convex side surface, adjacent two stationary blades defining an inter-blade fluid flow path together with the inner and outer walls, a suction port open to a first portion of the fluid flow path adjacent to the concave side surface and the inner or outer wall to suck the fluid therefrom, a blowoff port open to blow off the fluid to a second portion of the fluid flow path adjacent to the inner or outer wall and at which the pressure is lower than that at the first portion, and a passageway for communicating between the suction port and the blowoff port, thereby reducing the secondary flow loss and the blade configuration loss in the blade lattice.

Turbocompound engine with turbocharger control

Abstract: An exhaust energy extraction system for a multi-cylinder engine, comprisingn axial flow turbine arranged to convert time-spaced exhaust pressure pulses into turbine rotor rotation. Output flow from the axial flow turbine is directed through a diffuser that converts velocity pressure to static pressure; a second radial flow turbine is operated by the steady state flow produced by the diffuser. Any tendency of the diffuser to exert an adverse back pressure on the axial flow turbine is counteracted by a pressure-responsive vent valve that establishes a ceiling on the diffuser pressure.

Axial-flow reversible turbine

Abstract: An axial-flow reversible turbine comprises a nozzle assembly and a wheel rotor mounted consecutively in the direction of the flow of the working medium and provided with two-section blades. One section of said blades forms the flow duct of the direct-rotating turbine and the other section, the flow duct of the counter-rotating turbine. The flow duct of the direct-rotating turbine incorporates a valve in the form of variable-incidence airfoil vanes intended to deny the access of the working medium into said duct. The inside diameter of the flow duct of the counter-rotating turbine is larger than the outside diameter of the flow duct of the direct-rotating turbine. The gas flow ducts of the direct- and counter-rotating turbines communicate with each other through a cylindrical bushing with ports. Said bushing is installed coaxially with the wheel rotor at the inlet of the flow into the flow duct before the nozzle assembly and its inside diameter is substantially equal to the outside diameter of the flow duct of the direct-rotating turbine. The bushing is provided with a band arranged along its periphery and being sufficiently wide for overlapping the ports. The band has a device for moving it radially to at least two fixed positions in one of which it fits around the outside circumference of the gas flow duct of the counter-rotating turbine and in the other position it fits around the outside circumference of the gas flow duct of the direct-rotating turbine.

Investigation of a 1500 ft/sec, Transonic, High-through-Flow, Single- Stage Axial-Flow Compressor with Low Hub/Tip Ratio

Abstract: : Complete experimental results are presented from tests of an axial compressor stage designed for a flow per frontal area of 39.7 lb/sec/ft square, a total pressure ratio of 1.912 and a tip speed of 1500 ft/sec. The performance objectives of this stage were derived from a preliminary design study of a multi-stage compressor for an advanced turbojet engine. Since the most serious aerodynamic design problems of the over-all compressor were observed to be associated with the first stage, this stage was chosen as the subject of a research program. Results of the tests indicated that, at design speed, design flow was achieved with a rotor isentropic efficiency of 90.4 percent, a stage isentropic efficiency of 88.2 percent and a stage total pressure ratio of 2.065.

Vortex generators in axial flow compressor

Abstract: An axial flow compressor having a vortex generator system positioned upstream of a rotor with the height of the blades of the vortex generator system being greater then the running clearance of the rotor. The vortex generator system has at least three blades for each of the rotor blades and is spaced from the rotor blades such that the leading edge of the rotor is a distance from the vortex generator system greater then ten times the height of the vortex generator blades and the trailing edge of the rotor blades is a distance from the leading edge of the vortex generator system less then eighty times the height of the vortex generator blades. The spacing between the vortex generator blades is at least four times the height of the vortex generator blades.

A Cascade in Unsteady Flow.

Abstract: : The flow velocity in an axial compressor, with a distorted inlet pressure profile or rotating stall cells, is unsteady in both magnitude and direction with the unsteadiness in direction having a more abrupt effect on airfoil performance. The objective of this research was to obtain pressure distributions and pressure histories on both surfaces on an airfoil in a cascade while its is undergoing a sinusoidal variation in angle of attack.

Effect of casing treatment on performance of an inlet stage for a transonic multistage compressor

Abstract: An inlet stage of a transonic compressor was tested with three rotor tip casing treatment configurations: blade angle slots, circumferential grooves, and axial skewed slots. Significant increases in both rotor and stage total pressure ratio, total temperature ratio, efficiency, flow range, and very large improvements in stall margin were obtained with all three casing treatment configurations. The greatest improvement in performance was achieved with axial skewed slots.

Numerical solution of periodic transonic flow through a fan stage

Abstract: A numerical method of solution of the inviscid, compressible, two-dimensional unsteady flow on a blade-to-blade stream surface through a stage (rotor and stator), or a single blade row, of an axial flow compressor or fan is described. A cyclic procedure has been developed for representation of adjacent blade-to-blade passages, which asymptotically achieves the correct phase between all passages of a stage. A shock-capturing finite-difference method is employed in the interior of the passage, and a method-of-characteristics technique is used at the boundaries. The blade slipstreams form two of the passage boundaries, and are treated as moving contact surfaces capable of supporting jumps in entropy and tangential velocity. The Kutta condition is imposed by requiring the slipstreams to originate at the trailing edges, which are assumed to be sharp. Results are presented for several transonic fan rotors, and compared with available experimental data consisting of holographic observations of shock structure and pressure contour maps. A subcritical stator solution is also compared with results from a relaxation method. Finally, a periodic solution for a stage consisting of 44 rotor blades and 46 stator blades is discussed.

Multistage Axial-Flow Turbomachinery Wake Production, Transport, and Interaction.

Abstract: : The first year results of a study of multistage axial-flow turbomachine wake production, transport and interaction are described in this report. Evidence indicating how the noise level measured at the inlet of a low speed, multistage, axial-flow research compressor was found to vary appreciably with inlet guide vane and stator row relative circumferential positioning with the largest amount of noise reduction occurring at the blade passing frequency is presented. The results of detailed slow- (cobra probe and surface pressure taps) and fast-response (hot-wire) measurements made within the research compressor flow field to aid in understanding the physics involved are shown in scalar and vector plots and tables. Significant local changes in blade-section aerodynamic performance and flow field appearance with variation in stationary blade row placement were observed although corresponding improvement of overall efficiency could not be ascertained. Several interesting periodically unsteady aspects of the flow field and its measurement are demonstrated and some conclusions about blade row interaction are proposed. (Author)

Boundary-Value Thermal-Hydraulic Analysis of a Reactor Fuel Rod Bundle

Abstract: A new computational model for steady-state, single-phase, thermal- hydraulic, multichannel analysis of fluid flow through nuclear reactor fuel elements is presented. The model accounts for the conservation of mass, energy, and momentum subject to pressure-drop boundary conditions and leads to a nonlinear multipoint boundary-value problem. The turbulent interchange, radial thermal conduction, and forced flow due to the wire-wrap or grid between the channels are explicitly taken into account. The temperature distribution of the coolant, cladding, and fuel, and the size of the central void of the oxide fuel after thermal restructuring are computed in the model. Three different thermal- hydraulic channel arrangements, i.e., square, hexagonal, and triangular, can be treated by the method presented here. Multipin analysis with transverse interactions or multiassembly calculations without transverse interactions between the channels can be performed. The most important features of this new computational model are: (a) that the effect of axial flow area variation has been incorporated into the derivation of governing equations, (b) that the cross- flow approximation has been improved so that the assumption of constant transverse momentum flux in the direction under consideration is removed, and (c) that partial flow blockage occurring anywhere along the flow path can be analyzed,more » and the effect on the inlet mass velocity redistribution can be taken into account. (auth)« less

A 2D partially-parabolic procedure for axial-flow turbomachinery cascades

Abstract: A general finite-difference procedure is presented for the calculation of steady, two-dimensional ‘partially-parabolic’ flows, with special reference to turbine cascade problems. It can be used for incompressible, subsonic, supersonic or transonic flows. It can be characterised as an ‘iterative space-marching’ method. The method is more economical in computer storage than time-marching procedures; and computer time is also low. The main distinguishing features of the method are: (a) use of a streamline coordinate system (b) one-dimensional storage for all variables except pressure (c) solution by repeated marching integration from upstream to downstream. The capabilities of the method are demonstrated by application to six different inviscid-flow problems. In each case, computed results are compared with the available analytical or experimental data. Good agreement is shown. The method is capable of including momentum transfer across streamlines by viscous effects; it can easily incorporate a two-equation turbulence model; and heat transfer can be simultaneously calculated.

The Stability of Viscous Axial Flow in the Entry Region of an Annulus with a Rotating Inner Cylinder

Abstract: The stability of developing tangential flow induced by the imposition of an axial velocity on the tangential velocity distribution created by core rotation is theoretically and experimentally investigated. A linear stability analysis is used to examine the influence of axial length, axial Reynolds number and annulus radius ratio on the critical Taylor number for neutral stability when the axial velocity is assumed uniform. Predictions compare favourably with measurements obtained by hot-wire anemometer for air flowing in an annulus of radius ratio 0·9, particularly at small Reynolds number and large values of the axial length parameter.

Experimental and theoretical studies of subsonic fan noise

Abstract: The noise generated by inlet turbulence impinging on a subsonic axial flow fan was studied as a function of tip speed, flow coefficient, and intensity and scale of turbulence was carried out. Both turbulence and far field acoustic measurements were made. The new elements introduced in the theoretical analysis were accounting for blade loading dependent noise mechanisms and consideration of anisotropic turbulence impinging on the rotor because of inlet flow contraction effects. Experimentally an unexplained increase of noise at about 1/2 and 1 1/2 times blade passsing frequency was observed at low flow coefficients even though there was no evidence of compressor surge. In the final version the theory does a fair job of predicting variations of noise with blade loading and tip speed. Alteration of inlet turbulence length scales produced some but not very pronounced changes in the far field PWL spectra. Some degree of eddy contraction and resulting anisotropy were essential to explain the concentration of energy around blade passing frequencies.

Axial fan with automatically controlled variable pitch blades

Abstract: A fan impeller for axial flow having automatically variable-pitch blades ached to a rotatable hub for attaining maximum lift and inhibiting stall in a varying back pressure regime. The blades are attached for rotation about their axes to the hub, and are connected through a crank and link to a drive shaft. The hub is attached to the drive shaft to permit relative axial movement, but to preclude relative rotational movement. Varying back pressure moves the blades and the hub in variable blade rotation planes, causing changes in blade pitch. Springs and dash-pots, connecting the hub and shaft, act axially to give non-linear restoring forces and damping to the blade pitch changes.