Showing papers on "Diffuser (thermodynamics) published in 1969"

Diffuser for a centrifugal fluid-flow turbomachine

Abstract: A CENTRIFUGAL FLUID-FLOW TURBOMACHINE HAS DIFFUSER PROVIDED WITH TWO COAXIALLY ARRANGED ROWS OF ROTATABLE GUIDE VANES THROUGH WHICH THE FLUID FLOWS IN SUCCESSION. THE PIVOT AXES OF THE VANES OF SAID TWO ROWS ARE DISPLACEABLE IN RELATION TO ONE ANOTHER IN THE CIRCUMFERENTIAL DIRECTION OF THE ROWS.

Vehicle safety system

Abstract: An improved safety apparatus for protecting an occupant of a vehicle during both critical and noncritical accidents includes a confinement which is expanded to restrain movement of the occupant of the vehicle during a critical accident. Upon the occurrence of a critical accident, the confinement is inflated by fluid which flows from a fluid supply through a diffuser. The diffuser directs the fluid flow to inflate the confinement. In addition, the diffuser is adapted to be crushed or deformed due to impact by an occupant of a vehicle thereagainst during a noncritical accident to reduce the possibility of serious injury to the occupant. To further reduce the possibility of injury to the occupant of the vehicle during a noncritical accident, the fluid supply is mounted closely adjacent to a sidewall of the passenger compartment of the vehicle where it is unlikely to be engaged by the occupant.

Compressors for gas turbine engines

Abstract: 1280113 Centrifugal and axial-flow compressors; gas turbine engines AVCO CORP 30 June 1970 [4 Aug 1969] 31621/70 Headings F1C and F1G A compressor in or for a gas turbine engine comprises an axial-flow section 32, 46, Fig. 1, and a downstream, contra-rotating mixed-flow section 62. The axial-flow section discharges air at subsonic absolute velocity. The mixed-flow section has an inlet portion which is of substantially constant flow area and receives the air at supersonic relative velocity to thereby produce shock waves and reduce supersonic flow to subsonic, whereafter the air is radially accelerated and diffused in the outlet portion of the mixed-flow section. The impeller blades of the latter may be divided into an inlet row and and outlet row separated by a row of stator blades, Fig. 3 (not shown). Stator vanes (150), Fig. 8 (not shown), may be located immediately upstream of the mixed-flow section to equalize the relative velocity of the entering air over the radial extent of the annular flow duct. In the gas turbine engine shown, the compressed air is discharged through a diffuser 84 into combustion apparatus 18 comprising an annular series of cylindrical combustion units 90 which deliver hot gases into a duct 92. The latter discharges the gases through a full-admission inlet nozzle to drive turbine wheels 98, 114, which drive the respective compressor sections, and to either drive a further turbine wheel having an output shaft 30 or exhaust through a nozzle to produce propulsive thrust. Alternatively, the two compressor sections may be driven by a single turbine wheel via gearing. Sump housings 54, 72, 120 for the shaft bearings are each sealed at both ends by friction or labyrinth seal assemblies 60, 74, 106, 122.

Safety cushion air system

Abstract: The device is an inflatable safety air cushion for use as a safety device to protect passengers in vehicles. A gas such as nitrogen or helium is maintained at moderate pressure in an elongated container. It is transferred to a similarly elongated inflatable bag through an elongated nozzle type diffuser between the container and bag. The diffuser has a throat portion in which is positioned explosive opening or valve means in the form of a relatively thin membrane for opening the passageway to rapidly transfer the gas to the bag for inflating it without damaging the bag. The device, practically and effectively makes possible inflation of the bag in a sufficiently limited number of milliseconds to be fully operative for its purpose.

Terminal outlet for air distribution system

Abstract: This disclosure is directed to a controlled volume air terminal outlet for use at a room discharge of an air distribution system for a building. The terminal outlet includes a first damper section which is thermostatically controlled for throttling air passing therethrough and a second damper section which is manually or otherwise controlled. Discharge through the terminal outlets passes through a diffuser for air pattern control. A pressure and temperature branch control is also disclosed.

Fluid-motion apparatus

Abstract: Fluid compressor, pump, or like fluid-motion apparatus having rotor with blades interposed in a housing chamber intermediate the fluid inlet and discharge ports. The blades have relieved areas formed in the lateral edges thereof which interface a wall of the chamber to communicate a high-fluid pressure zone on the one side of said blades with a low-fluid pressure zone at the other side of said blade, thereby to control the fluid boundary layer. Further included is a diffuser with similarly relieved areas in the vanes thereof to communicate the disparate pressure zones to either sides of the vanes.

Pressure Recovery Performance of Straight-Channel, Single-Plane Divergence Diffusers at High Mach Numbers

Abstract: : Measurements were made of the pressure recovery of straight-channel, symmetric, single-plane divergence diffusers with inlet Mach numbers between 0.2 and 1.0. Three aspect ratios, 0.25. 1.0, and 5.0, were studied for a range of length-to-throat width ratios and divergence angles of diffuser geometries near peak recovery. Diffuser performance maps are given that show pressure recovery as a function of diffuser geometry for fixed values of throat Mach number, throat blockage, and aspect ratio for the range of variables tested. Of significant importance to the designer is the alteration in the shape of the pressure recovery contours on the performance maps with variations in Mach number, blockage, and aspect ratio. Four subprograms have measured the effect of changes in diffuser inlet Reynolds number, boundary layer shape factor, asymmetric distribution of inlet blockage around the throat periphery, and the influence of rounded throat corners on the pressure recovery behavior of the straight-channel diffuser. The importance to the designer of a knowledge of how diffuser performance depends upon the diffuser geometric and inlet parameters is discussed. The application of channel diffuser performance data to the design of centrifugal compressor diffusers is described. The channel diffuser performance measured is compared with recovery performance of the channel diffusers in centrifugal compressors.

Additive proportioning, positive displacement, pumplike device

Abstract: A pair of multivaned impellers are rotatably mounted interengaged longitudinally intermediate an inlet and outlet of a main fluid chamber, the impellers during rotation passing fluid in a bifurcated flow path between said vanes transversely outwardly along said impellers and longitudinally along transversely spaced sides of said main fluid chamber. An additive fluid chamber is also formed by the housing spaced from the main fluid chamber, said additive fluid chamber having similarly mounted impellers therein which are axially aligned with the impellers of the main fluid chamber and secured rotatable by said main fluid chamber impellers. The outlet of the additive fluid chamber is connected in fluid communication with a diffuser in the main fluid chamber, said diffuser being positioned midway of said impellers in the main fluid chamber extending axially elongated therealong at the chamber inlet side thereof. Furthermore, the diffuser has outlets transversely midway thereof directed toward the impellers and oppositely generally transversely extending arcuate surfaces closely adjacent each of said impellers extending transversely at least equal to the circumferential spacing of the vanes on the impellers. The chamber inlet side of the diffuser is preferably formed with arcuate surfaces similar to the before-mentioned arcuate surfaces but projecting arcuately in reverse fashion directing fluid from said chamber inlet in said bifurcated flow path. Finally, a diffuser may be similarly positioned in the additive fluid chamber preferably being formed of similar exterior shape, and the impellers of the additive fluid chamber are formed for passing fluid through said chamber of a determined proportionate volume less than the fluid passed through said main fluid chamber by the impellers thereof. Thus, additive fluid through the additive fluid chamber will be metered into the main fluid chamber for mixing with the main fluid flow in determined and exact proportion.

Turbulent Flow Separation Ahead of Forward Facing Steps in Supersonic Two-Dimensional and Axisymmetric Flows

Abstract: Pressure distributions in the separated flow region ahead of forward facing steps and on the step face in supersonic turbulent flows obtained at VKI are compared with those found by previous investigators. The following geometries were investigated : 1. Flat plate step models which (a) spanned the tunnel completely (b) spanned 75% of the tunnel width 2. Cone-Cylinder-step models 3. Axisymmetric internal flow models (a) nozzles followed by a 90 0 contraction (b) ejectors with a 90° contraction of the supersonic diffuser. Parameters such as step height, unit Reynolds number and Mach number we re compared. It was intended, in particular, to relate the axisymmetric results to existing two-dimensional data. A general law relating the variation of the step pressure integral with Mach number was found by analyzing pressure distributions on the step face. The influence of flow inclination, Mach number variation and three-dimensional effects on the characteristic pressures were discussed. The flow has been visualized by schlieren and schadow photographs and by the oil flow technique.

Experimental Evaluation of Moving Sound Diffusers for Reverberation Rooms

Abstract: The acoustic power flowing from a monopole source is proportional to the radiation resistance presented to the source. This value is determined by the modal structure and the acoustic impedance of the walls of the chamber. The rotating sound diffuser modulates the modal structure and with it, the radiation resistance. Comparison of the time average of the radiation resistance as the monopole source location is changed with and without the diffuser rotating indicates the effectiveness of a given diffuser design in removing the dependence of acoustic power output on the source position. The rotating sound diffuser evaluated was a symmetrical biconical surface of revolution rotating at speeds up to 30 rpm. Fifty percent of the surface area of the diffuser was covered with ribbed fiberglass, the remainder was left uncovered. In order to measure the radiation resistance an acoustic impedance head was fabricated from a modified loud speaker. Displacement of the diaphragm was sensed using a noncontacting fiber‐o...

Systems for producing cold and ejectors in such systems

Abstract: 1,187,455. Boundary layer control. PHILIPS' GLOEILAMPENFABRIEKEN N.V. 28 June, 1967 [1 July, 1966], No. 29779/67. Heading F2R. [Also in Divisions F1 and F4] An ejector for a refrigerating or liquefied gas-producing system (see Division F4), comprises a jet pipe 20, a diffuser 21 and a suction inlet 22, increased suction at inlet 22 being achieved by removing the boundary layer surrounding the high-speed gas leaving the jet pipe. As shown, the boundary layer is removed by a groove 25 connected by a conduit 26 to a low-pressure point 27, or to the suction side of a compressor or ejector. In Fig. 4 (not shown), a shoulder is formed on the downstream side of groove 25. In Fig. 5 (not shown), a sleeve surrounds the jet pipe nozzle and has an annular flange spaced downstream from the nozzle opening, the flange aperture being of smaller diameter than the nozzle opening and the space within the sleeve between the flange and the nozzle opening being connected to a low-pressure point.

Forced air diffuser

Abstract: In abstract, a preferred embodiment of this invention is a portable air diffuser including an air duct network fitted at the intake extremity with a blower and having a series of baffles attached to the outflow extremity with intermediate dampening control means.

Turbulent shear layer reattachment downstream of a backward-facing step in confined supersonic axisymmetric flow

Abstract: The reattachment of a supersonic jet with a turbulent boundary layer abruptly expanding into an axisymmetric parallel diffuser has been experimentally investigated using a surface-flow technique. Measurements were made in the started condition, where the blowing pressure is sufficiently high to establish an oblique shock system in the diffuser. The proposed reattachment criterion correlates present measurements in terms of the diffuser area ratio, and also those of other workers for unconfined flow in terms of the free stream Mach number after separation. As already reported for unconfined flow, it is found that disturbances downstream of reattachment do not affect the upstream region.

Performance of the Two-Dimensional Diffusers with Suction at the Entrance

Abstract: Experimental studies were carried out on the caracteristics of diffusers of rectangular cross section which have an angle of expansion 2θ=30°, 60°, 90°, and 180° and an area ratio of 4. Remarkabel improvement of the pressure coefficient and energy loss coefficient is achieved by means of suction at the entrance. It is found that the most effective position of suction is at the point right down stream of the corner. The diffuser efficiency increases with increase of aspect ratio. The efficiency, however, tends to be constant as the aspect ratio exceeds four. When the angle of expansion is 20°, 30°, 60°, and 90°, the rate of optimum suction is 3 to 4 per cent of the total flow rate. With this optimum suction, the efficiency of these wide angle diffusers approaches that of the diffuser of 2θ=10°.

Ground Effect Machines

Abstract: 1,170,747. Air cushion vehicles. NATIONAL RESEARCH DEVELOPMENT CORP. 16 Feb., 1967 [16 Nov., 1965], No. 48568/65. Heading B7K. An air cushion vehicle has ducting and power means for forming the cushion and effecting propulsion comprising a U-shaped planform duct 41 with air intakes 42, 43 at its forward end and with an upwardly hinging rear portion 44, 45, a jet nozzle (not shown) being formed in the base of the duct for discharge of a gas curtain. A leading intake duct and diffuser 47 is connected to duct 41 by lateral ducts 48, 49 in which are housed respectively fans 50, 51 which supply air to duct 41 and, through outlet 54, to the cushion space. Further fans 55, 56 in ducts 57, 58 draw air from intakes 59, 60 for delivery both to duct 41 through nozzles 61, 62 and to nozzles 63, 64 communicating with the aft part of the cushion. In operation at hover and low speed conditions the four fans supply cushion and curtain forming air with the rear portion 44, 45 lowered but at speeds, but at high speed the cushion is formed by ram air, the portion 44, 45 being raised.

Self-pumped electroadiabatic laser

Abstract: An electroadiabatic laser wherein a plenum chamber is provided in which a thermally heated gas is mixed with a relatively cold gas to provide lasing action. An alkali metal compound is mixed simultaneously with the gases to provide additional stimulation of the ionized gases by releasing additional electrons during mixing of the gases. The expanding gases pass through a nozzle into an excitation chamber wherein the gas flows through a magnetic field between two electrodes, generating a current in an electrode load circuit that is identical to the electron flow in the ionized gases. The flowing gases are further expanded through another nozzle into a larger cavity. A pair of electrodes in the second nozzle have an electric field thereacross for further stimulation of the lasing gas. Lasing action of the gas occurs in the larger cavity, a Fabry-Perot optical cavity, and the output therefrom is coupled out of the cavity by mirrors mounted therein. The gases are then exhausted through a diffuser to atmospheric pressure. A magnet provides the magnetic field in the excitation chamber. The excitation chamber electrode load circuit may be connected to provide the potential across the nozzle electrodes, thus using only the field produced by the magnet to generate the additional potential for further stimulated emission.

Imminent Separation Fluid Diffuser Passage

Abstract: 1,153,345. Boundary layer control. CATERPILLAR TRACTOR CO. 20 June, 1966, No. 27509/66. Heading F2R. A radial compressor 15 is formed with an annular diffuser 16 which is contoured so as to achieve a continuous condition of imminent boundary layer separation (defined as a condition wherein the boundary layer is about to, but has not yet, reached boundary layer separation) over the greater part of its length to obtain maximum efficiency with a minimum loss due to friction and heat. Formulµ are specified to derive the diffuser profile, which comprises a converging-, diverging-converging contour as represented by areas 18, 19 and 20 in Fig. 7, wherein as shown downstream of area 19, the flow reaches an imminent separation state denoted diagrammatically by diagrams 25, 26 and 27. One wall may be planar.

Theoretical solutions for the jet flap diffuser

Abstract: This study proposes a jet sheet as an alternative to a rigid diffuser for a momentum propulsor. This appears attractive technically. The diffuser shape can be tailored by modulating jet momentum and angle and can be switched off in forward flight since its main function is increasing thrust/power ratio at static speeds. Theoretical analysis for a steady inviscid incompressible flow predicts impressive thrust augmentations. Taking into account the energy required to feed the jet sheet, it appears that in some cases propulsor thrust can be more than doubled. It could be applied to ducted fans, jet engines and seems particularly attractive for ejector thrust systems. A first approach of the study of the flow is made in the planar and axisymmetric cases by assuming that the velocity is uniform in each section. For the planar problem a linearized solution is presented. A conformal mapping transforms it into a half-plane boundary value problem of the Riemann-Hilbert-Poincare type. It is solved by combining Filbert Transforms, asymptotic expansion and a digital computer program. Then the nonlinear two-dimensional problem is presented with some references to the way it could be solved.

Investigation of heat transfer and hydrodynamic drag in the turbulent flow of a gas in the field of a longitudinal pressure gradient of variable sign. I

Abstract: We present results from a study of heat transfer and hydrodynamic drag in the turbulent flow of a gas through a channel formed by a series of flat nonsymmetric diffusers with a divergence angle of 12° and a series of converging diffuser sections, for the interval Re =(10–80)·103.

Centrifugal fan structure

Abstract: This invention relates to a centrifugal fan having a rotatable fan wheel and stationary diaphragm disposed within a housing having an air inlet and outlet as its opposite ends. The diaphragm is spaced from the end of the housing having the air outlet to form a diffuser chamber. The air inlet of the housing cooperates with an axially disposed inlet of the fan wheel through which air is discharged radially outward to an outlet at the periphery of the fan wheel. The outer periphery of the diaphragm is spaced from the housing to form an annular discharge opening through which air at a high velocity passes from the outlet of the fan wheel to the diffuser chamber. In order to reduce the velocity of the air discharged from the fan wheel to transform its dynamic pressure to static pressure, a helical spring of annular form is disposed in the outer peripheral portion of the diffuser chamber.

An experimental investigation of new concepts in ejector thrust augmentation for v/stol.

Abstract: : The basic concept involved in the investigation is the utilization of the Coanda effect in combination with an external cascade of airfoils That combination served to achieve a more efficient rotation and amplification of the jet thrust vector as a result of both the large induced mass flow from the environment and the simultaneous high lift of the cascaded airfoils The program objective was to establish optimal performance by systematic variation of the pertinent parameters Experimental results showed a gain of 20% in augmented thrust compared to that of a simple Coanda cylinder Since the observed mass flow through the airfoil cascade was small, in-house tests were performed with diffusion The resultant increase in secondary mass flow produced a gain of 65% in thrust augmentation over the tests without diffusion despite large regions of flow separation in the diffuser It appears highly probable that further large gains can result from precise diffuser design and boundary layer control in the diffuser (Author)

An Experimental Method for Locating Streamtubes in a Free Jet Expansion to Near Vacuum

Abstract: : Experimental investigations of free jet expansions into near vacuum conditions have in the past been generally limited to pressure, temperature, and force measurements. This investigation concerned a method of experimentally defining the streamtubes in a free jet expansion by splitting the flow along streamtubes with a series of diffusers operating in a cryogenically pumped vacuum chamber. Conditions necessary for shock attachment at the diffuser inlet were analyzed and streamtubes in a CO2 free jet expansion were experimentally determined. The procedure was found to be applicable for up to 98 percent of the plume mass flow if suitable diffuser inlet design is used. The method is ideally suited for streamtube definition in flows with entrained solids, for condensing flows, or for gaseous mixtures. For the free jet expansion investigated, qualitative information was derived concerning the effect of nozzle boundary layer on the plume expansion, the degree of condensation in the plume, and the applicability of method of characteristics solutions to the expansion process.

Supersonic jet engine inlet flueric bypass control

Abstract: A flueric system for controlling the position of the normal shock wave in a turbojet diffuser is disclosed. Control is accomplished without the use of mechanically moving parts by providing an exhaust tube for reducing the pressure downstream of the normal shock. A fluid feedback path which is responsive to a pressure differential on opposing sides of the shock wave produces a fluid control signal which is capable of deflecting fluid away from the exhaust tube and thereby effectively closing off the exhaust tube whenever the shock wave has relocated itself in a stable position.

On the starting of supersonic nozzles with the aid of cylindrical diffusers

Abstract: : The efficiency of short cylindric diffusers was experimentally investigated in a supersonic wind tunnel provided with exchangeable nozzles with a conical supersonic section designed for M equals 2; 25; 30; 35; 40; and 5 0 and a half cone angle of alpha equals 8 degrees for all M numbers The diffusor lengths varied from one to eight calibers of the nozzle exit cross sections Compressed nitrogen was used as the working substance A graph of the ratio of the aerodynamic stagnation pressure during startup of a nozzle with diffusers to the relative diffuser length showed the advantage of using diffusers at higher nozzle M values A diffuser length of up to 3-4 nozzle calibers practically exhausts the possibility of decreasing the starting pressure of nozzles with calculated M values of less than 3 Diffuser lengths up to 6-7 calibers are expedient on nozzles for nearly hypersonic M values Sufficiently long cylindrical diffusers have an efficiency of 075-085 Diagrams are presented for selecting minimum diffuser lengths in the range of M equals 2-5 The experiments revealed that the maximum rarefaction attainable with cylindrical diffusers at the nozzle exit section during discharge into a normal atmosphere is 004 atm (Author)