Showing papers on "Diffuser (thermodynamics) published in 1972"

Development of a Venturi Type Bubble Generator for Use in the Molten-Salt Reactor Xenon Removal System

Abstract: A venturi type bubble generator was developed for application in the xenon removal system proposed for a molten-salt breeder reactor. Gas injected into the high velocity liquid at the venturi throat is fromed into bubbles by the fluid turbulence in the diffuser cone. Tests were conducted using aqueous solutions to determine the various pressure drops of the bubble generator as a function of liquid and gas flow rates and to determine the bubble diameter produced. Empirical relationships were developed which could be used in combination with the more conventional fluid flow equations to predict the overall head loss and the gas injection pressure of the bubble generator. A dimensionless correlation for predicting the bubble diameter was developed for bubble generators of similar geometry.

Cascade diffuser having thin, straight vanes

Abstract: A cascade diffuser providing high pressure recovery in radial flow turbomachinery has first and second vaned diffuser stages arranged between an impeller and collector. The first and second stages are formed by thin, straight vanes which contribute substantially to the pressure recovery rate. The first stage vanes are preferably spaced apart from the impeller to provide a vaneless region for initially conditioning fluid flow from the impeller. The leading edges of the first stage vanes are preferably tapered to provide a semi-vaneless transition region between the vaneless region and first diffuser stage. The diffuser walls form a flow path between the impeller and collector between which the first and second stage vanes are disposed.

Apparatus for forwarding tow

Abstract: A fluid jet apparatus for receiving a ribbon of parallel continuous filaments, then heating and spreading the filaments for deposit on a moving surface as a nonwoven web includes an adjustable diffuser connected to the outlet end of the jet. The diffuser comprises a pair of spaced plates, adjustable with respect to each other, mounted to the outlet end of the jet. The plates are arranged to form aspiration slots at one end between the jet and the plates. The slots open into a central converging passage formed by the plates for confining and diverting gas out the open sides of the diffuser. The particular structural arrangement of the plates with respect to the jet permits development of static pressure in the diffuser which in turn causes a large percentage of jet fluid to exit from the open edges of the diffuser, generally parallel to the moving laydown surface, while less fluid accompanies the filaments to the laydown surface to reduce web disturbance.

Analytical correlation of centrifugal compressor design geometry for maximum efficiency with specific speed

Abstract: Centrifugal compressor performance was examined analytically to determine optimum geometry for various applications as characterized by specific speed. Seven specific losses were calculated for various combinations of inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, blade exit backsweep, and inlet-tip absolute tangential velocity for solid body prewhirl. The losses considered were inlet guide vane loss, blade loading loss, skin friction loss, recirculation loss, disk friction loss, vaneless diffuser loss, and vaned diffuser loss. Maximum total efficiencies ranged from 0.497 to 0.868 for a specific speed range of 0.257 to 1.346. Curves of rotor exit absolute flow angle, inlet tip-exit diameter ratio, inlet hub-tip diameter ratio, head coefficient and blade exit backsweep are presented over a range of specific speeds for various inducer tip speeds to permit rapid selection of optimum compressor size and shape for a variety of applications.

Turbomachinery and method of manufacturing diffusers therefor

Abstract: A radial flow compressor is described which includes a diffuser having an annular entrance chamber surrounding the circumferential discharge of the impeller of the compressor. Diffuser channels extend from this annular chamber to an axial flow diffuser from which the compressed air is discharged into a collection chamber. The annular chamber is provided with contoured nodes from which the channel diffusers respectively extend at relatively low angles, tangentially in relation to the periphery of the impeller.

A Comparison of the Predicted and Measured Performance of High Pressure Ratio Centrifugal Compressor Diffusers

Abstract: A novel analysis of the hub and shroud wall boundary layer growth through the diffusing system of a centrifugal compressor is proposed to model the physical processes. It is shown that the diffuser throat blockage and total pressure loss characteristics can be accurately predicted for a 6:1 PR stage. The static pressure effectiveness and stalling limit are successfully predicted qualitatively, but are underestimated and overestimated by 14 and 12 percent respectively. It is argued that diffuser performance is largely controlled by the combined effect of the boundary layer conditions on the hub and shroud walls at impeller exit and the diffusion required to the diffuser throat. For this reason, it is contended that, for best performance at high pressure ratio (≃ 12:1), impeller exit Mach number must be minimized by employing zero to negative prewhirl at impeller entry which in turn maximizes impeller entry shroud relative Mach number. Performance maps are presented for a single-stage centrifugal compressor based on this premise with specific speed = 90. At 15, 12 and 101 PR, 72, 75 and 76.8 percent efficiency, respectively, were attached at 2.6 lb/sec.Copyright © 1972 by ASME

Centrifugal supersonic compressor

Abstract: A centrifugal supersonic compressor construction enables a high pressure ratio between the output and the input to be obtained. This compressor comprises an axial input stator, a rotor provided with a rotating diffuser, and a fixed diffuser which is a volute extended by a nozzle rectilinear in section. The rotating diffuser of the rotor consists of two coaxial discs connected together by radial blades, the radial dimensions of the blades and of the discs being such that the speed at the output of the diffuser rotating alone is slightly supersonic thereby obtaining a shock wave at the inlet of the nozzle.

Fluid mixing and spraying apparatus

Abstract: A fluid mixing and spraying apparatus and method. The apparatus includes a body having an elongated chamber with a diffuser positioned therein having a central passageway with an entrance end and an exit end. The diffuser has an end wall at the exit end of the central passageway. The end wall of the diffuser has a plurality of spaced openings to permit a first fluid supplied to the entrance end of the passageway under pressure to exit through the openings into the elongated chamber as a plurality of streams. An intermediate portion of the diffuser has a peripheral recessed portion which defines a distributing chamber for receiving a second fluid under pressure. A plurality of channels formed in the diffuser extend from the recessed portion to the end wall to permit the second fluid in the distributing chamber to exit from the chamber through the channels into the elongated chamber as a plurality of streams to mix with the first fluid. Baffle means also may be provided in the elongated chamber beyond the point where the two fluids first meet and mix to further facilitate mixing of the two fluids prior to their discharge through a fluid spray tip.

Structure of underexpanded supersonic swirling gas jet

Abstract: Results ate presented of a study of a supersonic swirling gas jet issuing from a nozzle in the underexpanded regime. It is shown that the effect of rotation on the wave structure of the axisymmetric jet is qual i ta t ively analogous to the effect of a reduction of the overpressure ratio. On the basis of the formulas for spiral isentropic flow an approximate expression is obtained for determining the location of the disk-shaped shock wave in the swirling flow downstream of the nozzle without a diffuser section. The existence of a reverse-axialflow zone in the highly twisted jets is established, and an estimate is made of the velocit ies in this zone. Some results relating to the nature of the discharge and thrust characteristics of a nozzle with swirling gas flow have been presented in [i-8]. It is well known [4-6] that the discharge of the conventional underexpanded gas jet is accompanied by the appearance of shock waves downstream of the nozzle, if the difference between the pressure Pl at the je t axis and the pressure Pz in the surrounding medium is relat iveIy small, a shock wave of l imited extent is ini t ialIy formed at the edge of the jet [4] (Fig. la ) . Further increase of Pl leads to an increase of the length of the shock wave until i t f inally intersects the flow axis (Fig. lb). By continuing to increase the pressure in the je t we can obtain an X-shaped shock which develops because of reflection of the wave from the jet axis (Fig. lc ) . Finally, beginning with some value of Pl, regular reflection of the shock wave becomes impossible and a Mach configuration is formed with a disk-l ike compression shock perpendicular to the jet axis (Fig. ld) . In the case of a nonswirling jet issuing from a nozzle without a diffuser section the distance between the diskl ike shock wave and the nozzle exit is determined by the degree of je t overcompression Pl/P2 and is described satisfactorily by the very simple reIation [7].

Channel diffuser with splitter vanes

Abstract: A centrifugal impeller discharges supersonic flow into a channel diffuser having a plurality of passages of rectangular cross section with leading edges closely adjacent the periphery of the impeller. A series of splitter vanes in the passage inlets have leading edges closely adjacent the periphery of the impeller and divide the inlet region into two separate passages through which the supersonic flow is shocked down to a subsonic level with an efficient pressure increase.

Tip turbine inflating device

Abstract: An inflating device having the character of a tip turbine type fan particularly adapted to enable a substantially instantaneous inflation of emergency life saving devices such as escape slides and life rafts. It features an improved nozzle configuration for receiving and delivering a small amount of high pressure air to a rotor assembly, in the operation of which the high pressure air is expanded and delivered as a high volume inflating medium, amplified by an ingested portion of ambient air. The rotor housing is distinguished by an inlet the form of which produces a smooth inflow of the ingested air and an outlet characterized by stator blades the mount of which avoids the problems normally anticipated where the device is subjected to extreme changes in temperature. The rotor outlet features a diffuser extension which contributes to its performance and increases its pumping efficiency.

Variable diffuser centrifugal pump shutter control

Abstract: A fluid delivery system includes a shuttered diffuser, constant speed, centrifugal pump, a metering valve for distributing fluid delivered by the pump, and a control system for positioning the shutter in response to the operation of the metering valve. The shutter includes a dual area annular piston, one face of which is subjected to the outlet pressure of the pump, while the other face of which is subjected to a signal pressure which is controlled by means of a signal valve associated with the metering valve. The signal valve operates to open the shutter at high flow rates and close the shutter at low flow rates, thereby reducing fluid temprature rise otherwise associated with a constant speed, centrifugal pump.

The Prediction of the Optimum Performance of Ejectors

Abstract: A simple, incompressible flow, ejector model was formulated and analysed. It was found that the results obtained analytically agreed closely with those of an experimentally conducted optimization carried out by other workers. The model was also used to compare the relative merits of constant static pressure versus constant area mixing: it was shown that the latter was superior to the former when nozzle, mixing tube and diffuser friction losses were taken into account. The work also indicated that the efficiency of an ejector tends to increase as the secondary-to-primary stream density ratio decreases.

Stage for a centrifugal pump

Abstract: Disclosed is an improved stage adaptable for use in multistage centrifugal pumps which find their primary use in moving liquids from deep wells and the like. The pump can include a motor, rotatable drive shaft, external casing and at least one of the improved stages, each stage having an impeller to impart velocity to the liquid and a diffuser to reduce velocity and increase the pressure to force the liquid to the successive stages and to the pump outlet. The impeller is rotated within a stage housing, nonrotatably mounted within the pump casing, and includes a front and rear plate having vanes therebetween which spiral outwardly from the center to the outer edge of the front plate. The front plate extends radially outwardly of the rear plate and terminates in an axially directed flange having a diameter approximating that of the stage housing but clearanced to rotate therein. Liquid thus exits the impeller axially and is received by the overlying diffuser with a minimum of turbulence.

Occupant restraint system

Abstract: An inflator of a vehicle occupant restraint system provided with a source of pressure fluid to inflate a cushion. A manifold receives the pressure fluid from the source and includes a nozzle through which the fluid accelerates to a supersonic flow. The nozzle has a throat that provides for the formation of a normal shock wave within the throat. A passage portion of the manifold is of generally uniform cross-sectional area and receives the supersonic fluid and the normal shock wave from the nozzle. A converging nozzle receives the fluid flow from the passage portion and has a throat for trapping the normal shock wave upstream therefrom to prevent the normal shock wave from traveling downstream of the passage portion and to decelerate the fluid flow to subsonic. A diffuser or apertured outlet portion receives the subsonic fluid from the converging nozzle and communicates the subsonic flow to an inflatable occupant restraint cushion.

Centrifugal flow gas turbine engine with annular combustor

Abstract: A small gas turbine engine having a small, high speed shaft assembly including a central shaft member, a radial outflow compressor rotor secured to one end of the central shaft member with its inlet end disposed outboard of the shaft assembly, and a radial inflow turbine rotor secured to the other end of the central shaft member with its discharge end disposed outboard of the shaft assembly. The shaft assembly is supported at its ends, outboard of the rotors, by a pair of bearings which are axially secured but allow limited radial movement of the shaft assembly. An annular combustor is disposed between the turbine and compressor rotors in encircling relation to the central shaft member. Fuel is supplied to the combustor chamber from the exhaust end of the turbine through an axial passage in the shaft assembly opening at one end outboard of the exhaust end bearing and communicating at its other end with radial ports in the central shaft member arranged to sling fuel into the combustor chamber. The shaft assembly housing comprises two cast sections which are coupled together to enclose the combustor with the end portion of each housing section shaped to define a shroud for the radial blades of the turbine and compressor rotors, respectively. A cast nozzle plate and a diffuser plate are secured to the respective housing sections. The nozzle and diffuser plates each include an annular outer portion defining the vanes for the turbine and compressor rotors, respectively, and a central hollow hub portion embracing the central shaft member of the shaft assembly; the inboard ends of the two hub portions are axially spaced to expose the radial ports in the central shaft member and allow slinging delivery of fuel into the combustor. An annular air inlet to the compressor rotor spaces the shaft assembly housing from a transmission housing, and the compressor end of the shaft assembly is coupled, outboard of the compressor end bearing, to speed reduction gearing journalled within the transmission housing.

Porous diffuser for gas supply to passenger restraint

Abstract: A porous diffuser for an inflatable bag passenger restraint system for automobiles is provided between a supply of gas and the inflatable bag. In one embodiment it has a flow cross-section larger than the flow cross-section for gas at some other portion between the gas supply and the inflatable bag. In one embodiment the diffuser is arranged within the bag for cooling, filtering and distributing gas over a large area for avoiding damage to the bag and also for noise suppression. In another embodiment, the diffuser is between a pyrotechnic gas supply and a metering orifice for cooling and filtering the gas, thereby reducing pressure in the pyrotechnic gas generator. If desired the porous diffuser can serve as a flow limiting ''''orifice''''.

Recent radial turbine research at the NASA Lewis Research Center.

Abstract: The major results obtained in several recent experimental programs on small radial inflow turbines for space applications are presented and discussed. Specifically, experimental and analytical work associated with these systems that has included examination of blade-shroud clearance, blade loading, and exit diffuser design, is considered. Results indicate high efficiency over a wide range of specific speed, and also insensitivity to clearance and blade loading in the radial part of the rotor. The exit diffuser investigation indicated that a conventional conical outer wall may not provide the velocity variation consistent with minimum overall diffuser loss.

Aircraft system lift ejector

Abstract: Apparatus and methods of operation are disclosed for combining high-energy primary flow fluid (normally a gaseous medium obtained from an aircraft system primary power plant or engine) and induced secondary flow fluid (ambient air) in the essentially conventional throat and diffuser sections of an ejector normally installed in an aircraft fixed wing, canard, or similar airfoil member to significantly increase ejector thrust augmentation ratio performance with a limited number of injection slots or openings of limited size to achieve high diffusion rates and substantially reduced propulsion energy losses attributed to flow resistance, flow backage, and flow separation, to permit ejector configurations of relatively small planform and relatively short diffuser lengths, to achieve apparatus stowability in conventional flight, to achieve design simplicity which allows variable geometry ejector for installation in aircraft system wing and canard airfoils, and to obtain other important aircraft system operating characteristics.

External combustion power producing method and apparatus

Abstract: An external power producing method and apparatus are provided in which a mass of a condensable fluid is heated and preferably superheated to a vapor at a predetermined working temperature and pressure and a portion thereof is directed into a positive displacement engine or turbine-pressure recovery diffuser set, where it does non-expansive work. A portion of the superheated or heated vapor at working pressure and temperature is expanded in a work producing expansion device, after which the expanded fluid is condensed. The condensate or a weight equivalent thereof is directed into the superheated or heated condensable fluid in the positive displacement engine, or into the diffuser of the turbine-pressure recovery diffuser set. The mass of fluid from the positive displacement engine or turbine is then directed into the superheater or heater for the mass of fluid.

Effects of transverse ribs on pressure recovery in two-dimensional subsonic diffusers

Abstract: : An experimental investigation was conducted to evaluate the performance of two-dimensional ribbed diffusers. Static pressure recovery of a straight wall diffuser and a corresponding ribbed diffuser was obtained over a wide range of diffuser total angles and subsonic Mach numbers for three diffuser length-to-throat width ratios. At selected geometries, total pressure recovery and distortion index were obtained. In addition to an optimum rectangular rib design, obtained from earlier water table flow visualization test, a chamfered rib and a roughened surface insert were also tested. A high response pressure transducer was used to detect pressure fluctuations occurring within one of the inter-rib cavities.

Vehicle occupant restraint system

Abstract: A safety system for vehicle driver restraint of the type using a collapsed inflatable confinement mounted on the steering column. The confinement is inflated by a collision sensor-actuated explosive charge which activates a fluid pressure source in one embodiment and fluid is discharged to the confinement through a diffuser disposed centrally and annularly about the reservoir. The annular fluid source is nonrotatably attached to the steering column mast jacket and a rotary fluid pressure seal is provided between the diffuser and the steering column mast jacket. In one embodiment of the invention, the fluid pressure supply is a solid propellant gas generator nonrotatably mounted to the steering column mast jacket. In another embodiment, the fluid pressure source is a toroidally shaped reservoir containing fluid stored under pressure.

Nested toroid nozzle apparatus

Abstract: A nested toroid nozzle apparatus for vertical or short takeoff aircraft in which the source of power may be a turbofan, turbotip fan, or turbojet engine thrust unit housed in an aerodynamically clean nacelle. The nacelle also carries the nozzle components making it possible to integrate the continuity of lift and cruise thrust throughout the range required to convert from vertical lift to forward acceleration and into cruise flight. The nozzle components provide a close coupling between the thrust fan plane and the centerline of the downwardly vectored thrust. The nozzle components have a toroidal shape for maximum nozzle efficiency, compactness and lightweight, assumption of primary thrust loads in hoop tension, and diffuser designed for minimum pressure losses during the vectored lift mode and conventional cruise mode.

Tolerance of Mach 2.50 axisymmetric mixed-compression inlets to upstream flow variations

Abstract: An investigation of the tolerances of two Mach 2.50 axisymmetric mixed-compression inlets to upstream flow variations was conducted. Tolerances of each inlet to angle of attack as a function of decreasing free-stream Mach number were obtained. A local region of overcompression was formed on the leeward side of the inlet at maximum angle of attack before unstart. This region of overcompression corresponded to local subsonic flow conditions ahead of the geometric throat. A uniform Mach number gradient of 0.10 at the cowl lip plane did not affect the inlet's pressure recovery, mass flow ratio, or diffuser exit total-pressure distortion.

Method and apparatus for determining the thrust of a jet engine

Abstract: Apparatus is known for determining gross thrust in jet engines by measuring various internal pressures, including measurement of total pressure at the nozzle entrance by means of an immersed probe. The immersed probe has a very short life when an afterburner is used in the engine. The apparatus for the invention is able to determine total pressure at the nozzle entrance, without an immersed probe, from the total pressure in the diffuser and the static pressure at the nozzle entrance. Another embodiment makes use of an additional static pressure in the flameholder region. Also, the invention is for determining the gross thrust of an engine and it distinguishes between an engine with a nozzle operating in a choked condition and an unchoked condition.

Basic flow characteristics of a linear aerospike nozzle segment.

Abstract: The separated base flow region within a linear aerospike nozzle segment is investigated experimentally in an ejector-diffuser system. The nozzle-diffuser system and base pressure characteristics are described over the pressure ratio range from the 'open wake' to the 'closed wake' operation. Schlieren photographs and static pressure distributions along the test section centerline and top contour describe the transition from 'open wake' to 'closed wake' flow fields. Base pressure and static pressure distributions are utilized to present the effects of a ramp diffuser. The effects of base bleed on the base pressure ratio and structure of the nozzle flow field are also presented.

Zone of flow establishment for round buoyant jets

Abstract: A method is developed to predict physical properties within the zone of flow establishment (ZFE) for thermal effluents discharged as buoyant jets through round submerged diffusers. The ZFE is the region immediately beyond the diffuser exit in which the mean flow profiles undergo a transition from their internal flow shapes to a free turbulent flow condition. The integral equations of mass, energy, and momentum conservation are used. The solution includes the length of the ZFE and the values of jet width, jet orientation, and center line temperature throughout this zone. The method can predict buoyant jets with three-dimensional trajectories discharged to flowing stratified ambients. Results obtained with the method agree well with the limited experimental data available and with existing empirical correlations. These results provide the necessary initial conditions for conventional (applicable only in the zone of established flow) jet prediction methods; and thus the accuracy of hydrothermal predictions of thermal effluents from power plants will be improved.

Compressor with cooling

Abstract: Method and apparatus for compressing gaseous fluids with minor amounts liquids, if any; by employing a rotating rotor wherein said fluid is compressed to a pressure that is normally higher than the fluid pressure immediately leaving said rotor; said fluid being usually further pressurized in a diffuser to utilize the kinetic energy of said fluid leaving at high velocity said rotating rotor; said rotating rotor being a centrifuge, with said fluid being compressed in the cavity of said rotor; said rotor cavity being provided with a cooling means to maintain nearly constant fluid temperature during said compression. Discharge nozzles from said rotor cavity are provided for said fluid near the periphery of said rotor; said nozzles may be arranged to discharge said fluid either radially, backward or forward as desired; said nozzles being either converging or converging diverging in shape as required to attain highest possible exit velocity for said fluid.

Analytical and experimental study of axisymmetric truncated plug nozzle flow fields

Abstract: Experimental and analytical investigation of the flow field and base pressure of internal-external-expansion truncated plug nozzles are discussed. Experimental results for two axisymmetric, conical plug-cylindrical shroud, truncated plug nozzles are presented for both open and closed wake operations. These results include extensive optical and pressure data covering nozzle flow field and base pressure characteristics, diffuser effects, lip shock strength, Mach disc behaviour, and the recompression and reverse flow regions. Transonic experiments for a special planar transonic section are presented. An extension of the analytical method of Hall and Mueller to include the internal shock wave from the shroud exit is presented for closed wake operation. Results of this analysis include effects on the flow field and base pressure of ambient pressure ratio, nozzle geometry, and the ratio of specific heats. Static thrust is presented as a function of ambient pressure ratio and nozzle geometry. A new transonic solution method is also presented.