Showing papers on "Diffuser (thermodynamics) published in 1976"

Gas nozzle for laser welding

Abstract: A laser system includes a nozzle assembly for use in directing a shielding gas around a laser beam and thereby protecting the point of focus from contamination by the atmosphere as is useful in welding and cutting applications. The nozzle includes a manifold section for admitting a shielding gas such as inert gas through a diffuser formed therein which exits from an outlet aperture through a nozzle tip section. The geometry of the nozzle is such that a certain amount of the shielding gas is flowed backward through an inlet aperture in the manifold section and thence into a housing container reflecting mirrors for directing and focusing the laser beam through the nozzle assembly. The remaining shielding gas, which is the bulk of the gas admitted, passes out through the outlet aperture in column fashion around the laser beam. By producing a back flow of shielding gas, aspiration of air through the housing and onto the workpiece is avoided. In addition, the necessity of having alternative means for preventing such aspiration in the form of windows or lenses closing off access to the housing is also prevented. The nozzle assembly is in two parts to facilitate interchanging of nozzle tips with the manifold, thereby providing a range of outlet opening sizes.

Ultrasonic gas stream liquid entrainment apparatus

Abstract: An atomizer assembly includes an ultrasonic resonator which is clamped along a clamping line near one end and driven along a driving line spaced from the clamping line. The atomizer is positioned centrally in a throat for receiving a gas flow at an inlet end and for emitting the gas flow at an outlet end. A gas diffuser is provided for directing the gas flow from the inlet end to contact the surface of the ultrasonic resonator at a high angle of incidence. A liquid flow path is provided through the clamp for directing a liquid to impinge on the vibratory surface of the ultrasonic resonator. The internal surface tension in the liquid is overcome by the vibratory motion and the liquid is cast from the surface of the resonator in atomized form at a low velocity. The atomized liquid is mixed thoroughly with the gas due to the opposing directions of the atomized liquid and the gas flow. The mixed or entrained atomized liquid is passed through the outlet end of the throat.

Centrifugal compressor advanced dump diffuser

Abstract: Airflow exiting a centrifugal compressor is diffused in multiple shaped passages tangential to the compressor impeller dumped into a plenum to reduce its Mach number and then directed through deswirl vanes to the entrance of a combustor. Deswirl at reduced Mach number significantly reduces pressure losses resulting in reduced complexity and manufacturing cost for the diffuser deswirl system.

The Effect of Variable Geometry on the Operating Range and Surge Margin of a Centrifugal Compressor

Abstract: Two variable geometry techniques have been applied to a small turbocharger compressor, with the objective of trying to move the peak pressure ratio operating point to lower flow rates, thereby yielding a broad flow range map. Variable prewhirl guide vanes and variable vaneless diffuser passage height have been studied separately. The results obtained with both techniques are compared and the relative merits and demerits with respect to improved flow range and isentropic efficiency penalties are considered.Copyright © 1976 by ASME

Flow and heat transfer measurements in a pseudo-shock region with surface cooling

Abstract: An experimental investigation was conducted to acquire information on the flow structure, mean flowfield, and temperature distributions in a pseudo-shock region in a supersonic diffuser with surface cooling. The Mach number upstream was 2.9, and the wall to stagnation temperature ratio was 0.44. A Mach-disk-like shock wave emanated from the thin separated flow region near the beginning of the compression region, and reattachment occurred one diameter downstream so that the flow was not separated over most of the pseudo-shock region. The flow compression was a shock-free, predominantly viscous process. Along the pseudo-shock region the measured heat-transfer coefficient increased approximately as the 0.8 power of the measured wall static pressure. The estimated wall shear stress increased downstream of flow attachment, but was still considerably less than the upstream value.

Compressor-Diffuser Interaction with Circumferential Flow Distortion

Abstract: An analytical and experimental study of axial compressor-diffuser interaction in circumferentially non-uniform flow is reported. An analysis of non-axisymmetric flow in an annular diffuser is presented, based on an inviscid rotational core flow plus the use of a diffuser effective area ratio to account for boundary layer blockage. The analysis is applied to the prediction of the diffuser flow field associated with the presence of a circumferential total pressure distortion. It is found that large static pressure non-uniformities can exist at the inlet of diffusers that are short compared with their mean circumferences, as is usually the case in turbomachinery applications. The analysis is coupled to an asymmetric compressor flow field prediction to provide a method for calculating the effect of an exit diffuser on compressor performance with distortion. It is shown that the velocity defect seen by the compressor can be substantially increased by the presence of the diffuser.The experiments were directed a...

Turbocharger and air cleaner device

Abstract: A turbocharger and intake air cleaning device for use with internal combustion engines. A collection spout is mounted tangent to the volute of the diffuser housing at a position from the turbocharger's discharge port which is upstream relative to the direction of rotation of air within the housing. A nozzle is mounted in the distal end of the collection spout. Dirt and other foreign matter carried in the rotating air stream migrates by centrifugal action into the collection spout where it is separated from compressed air flowing through the discharge port. An opening in the nozzle expels the foreign matter while at the same time limiting air leakage so as to maintain boost pressure within the diffuser.

Vortex jet pump

Abstract: A vortex jet pump is provided in which circumferential flow in a fluid flow passage through the pump is induced by a tangential power liquid jet inlet into the passage between its suction inlet and its outlet. The pump, which has no moving parts, has a housing providing a fluid flow passage between a pumped fluid suction inlet and a pumped fluid outlet downstream therefrom. Downstream from the power liquid jet inlet there is a throat in the passage having a flow cross section less than the flow cross section of the passage adjacent the power inlet jet inlet. A diffuser section is provided in the passage downstream from the throat and includes means for converting primarily circumferential fluid flow to primarily axial fluid flow in the passage. Preferably such means comprises fixed vanes in the passage downstream for the power liquid let inlet. Means are provided upstream from the power liquid jet inlet for injecting fluid into the passage in a primarily tangential direction for initiating circumferential flow in the passage. The velocity head of the injected fluid is less than the velocity head of the power liquid injected through the jet inlet to minimize cavitation.

Analytical Procedure for Calculation of Attached and Separated Subsonic Diffuser Flows

Abstract: An analytical procedure for computing the static and total pressure distributions in subsonic diffusers with axisymmetric or two-dimension al cross sections is described. It includes velocity profile and shear stress parameters which apply to attached and separated flows and allows for a strong interaction between the inviscid and viscous portions of the duct flow. With this approach, solutions can be obtained for separated regions where conventional boundary-layer methods fail. Analytical and experimental static and total pressure distributions are compared for plane-wall and conical diffusers. An approximate technique is used to apply the analysis to actual aircraft diffusers. A Ae a0 al9...,a7 blfb2,b3 CD D d

Variable flow capacity gas turbine engine for improved part load fuel economy

Abstract: A gas turbine engine includes a compressor having a plurality of fixed diffuser passages therein each including a gate and associated cam ring control means for operating each of the gates either open or closed to vary the gas flow through the compressor diffuser for turbine engine control; the gas turbine engine further includes a turbine section having a plurality of turbine nozzle passages each having a separate gate therein selectively operated under the control of cam ring means to vary the amount of motive fluid to the turbine in accordance with desired engine operation and wherein each of the gates are operative with respect to either the diffuser or the nozzle passages to change the area of gas flow therethrough by blocking some or all of the channels without resultant change in incident angle of the gas flow with respect to the inlet of each of the passages.

On Separation of a Divergent Flow at Moderate Reynolds Numbers

Abstract: Flow separation in a divergent channel was investigated in connection with problems of instability and oscillations in physiology at a Reynolds number range much smaller than that usually considered in engineering diffuser design. Experimental data on a divergent flow through a two-dimensional water tunnel in the Reynolds number range Re = 1000 to 6000 are presented. The quantities measured are flow rate, divergence angle, and mean pressure differential between two fixed points at the throat and downstream. In a lower range of divergence angle flow separation is characterized by a sharp decrease in the mean pressure differential when the flow rate is increased continuously and gradually; whereas recovery from separation is signaled by a discontinuous increase in pressure when the flow rate is decreased again. The critical Reynolds numbers for separation and reattachment are detectably different. Some discussion is given about flow separation in external and internal flows.

An Experimental and Analytical Investigation of Axisymmetric Diffusers

Abstract: A finite difference computer program for turbulent compressible flow was used to establish the performance of several diffuser shapes for experimental testing. The diffusers were designed to have a linear change in Mach number, a linear change in pressure, or a curvature fitted by a quadratic equation. Testing was performed with M = 0.1 to 0.9 with and without boundary layer bleed. Above M = 0.6, data were obtained with a normal shock upstream of the diffuser entrance. Peak static pressure recovery occurred with a diffuser inlet M0.75. The quadratic diffuser yielded the highest total pressure recovery.

Diffuser augmentation of wind turbines

Abstract: One of the more promising advanced concepts for overcoming the economic deterrents to widespread use of windpower is the Diffuser-Augmented Wind Turbine (DAWT). The diffuser controls the expansion of turbine exhaust flow, producing a highly subatmospheric pressure at the turbine exit. The low static pressure induces greater mass flow through the turbine in contrast to a conventional turbine design of the same diameter. Thus, the output power of the DAWT is much larger than for an unshrouded turbine. Our wind tunnel investigation of models of two diffuser design concepts is directed toward unconventional, very short, cost-effective configurations. One approach uses the energetic external wind to prevent separation of the diffuser's internal boundary layer. Another method uses high lift airfoil contours for the diffuser wall shape. Diffuser model tests have indicated almost a doubling of wind power extraction capability for DAWTs compared to conventional turbines. Economic studies of DAWTs have used these test data and recent (1975) cost projections of wind turbines with diameter. The specific power costs ($/kW) for a realistic DAWT configuration are found to be lower than conventional wind turbines for very large size rotors, above 50 m diameter, and for rotor diameters less than about 20 m. The cost-to-benefit assessment for intermediate size rotors is affected by the uncertainty band of cost for these rotor sizes.

Damping device for a liquid flow

Abstract: Damping of pressure oscillations and pressure surges in pipelines (1) through which liquid flows is achieved in that there are provided, in the pipeline (1), a perforated plate (4) and at least one flexible wall element (6) immediately adjacent thereto, it being possible advantageously to configure the perforated plate (4) as a step diffuser (5). A damping device of this type is particularly suitable for use in paper-making machines for the uniform supply of a fibrous-material suspension.

Design, development, and test of a laser velocimeter for high speed turbomachinery

Abstract: The paper describes the design, development, and test of a laser Doppler velocimeter (LDV) to map the velocity fields in a small, high speed, 8:1 pressure ratio, 091 kg/s (2 lbm/s), centrifugal compressor This instrument is being used as a diagnostic tool for the study of the basic fluid dynamics of the inducer, impeller and the diffuser regions of high pressure ratio, small, centrifugal compressors The LDV instrumentation has been optimized to permit the measurement of instantaneous velocities up to approximately 500 m/s, measured in absolute coordinates, within a rotating compressor impeller Velocities of the same magnitude can also be measured in the two-dimensional radial plane of the diffuser It is shown that LDV can make nondisturbing gas velocity measurements and surmount the difficulties found in applying other types of aerodynamic instrumentation to this measurement problem

Application of radial-splitters for improved wide-angle diffuser performance in a blowdown tunnel

Abstract: Severe flow separation in the 15:1 area-ratio, 38 deg total angle conical diffuser preceding the settling-chamber of an intermittent blowdown wind tunnel was eliminated by the use of a novel radial-splitter arrangement. As a consequence, the operating life of settling-chamber screens was greatly extended and test-section flow steadiness improved, with no penalty in the tunnel running time.

Powdery material continuous conveyor - has material metering unit coaxial to mixing chamber on upstream side

Abstract: The continuous powdery material pressure conveyor is particularly for pulverised coal, having a gaseous medium discharged through a nozzle under pressure at high speed into a mixing chamber into which the material is metered The metering unit in the direction of flow is mounted axially before and coaxially to the mixing chamber, thus introducing the material into the latter along its centre line and in the axial direction The medium can be discharged via a Laval nozzle and a diffuser attached to it In the axial direction between the diffuser and the mixing chamber is a compression section

Injection type ventilator for industrial use - has group of primary injectors feeding second stage main injector

Abstract: The main diffuser (2) has a convergent section (5) followed by a divergent section (16). Injector fluid is suing from a group of nozzles just upstream of the diffuser entrains secondary air through it to ventilate a mine, sewer, forge, foundry or other industrial location. There are three injector nozzles (1a, 1b, 1c) arranged evenly in a circle and fed from a common source of primary air. Each nozzle is itself a convergent divergent diffuser with an inlet for secondary air so that the fluid driving the main injector has already been increased in volume by a first stage of injection. The primary group of nozzles is mounted (4) to be axially adjustable in relation to the main diffuser (2).

Diesel engine turbocharger pressure control - injects compressor bleed air obliquely into drive turbine flow to increase speed

Abstract: The turbo charger admits air to the diesel engine and is driven by a shaft which is powered by a turbine. Exhaust gases from the engine power the expansion turbine. There is an air bleed from the air inlet to the engine this bleed being controlled by a throttle valve. The air is bled from the diffuser of the turbo charger and injected from the diffuser of the expansion turbine in order to give adequate control. The control of the throttle valve is linked mechanically to a governor, to maintain a constant speed of the turbo charger. The bleed air is injected between exhaust distribution blades (25) through an annular slot (27) from an annular chamber (26). The air is injected at a small angle to the exhaust flow and increases the speed of this flow.

V-STOL Ejector Short Diffuser Study.

Abstract: : Development of thrust augmenting ejectors has produced ejector/diffuser configurations capable of achieving the high levels of thrust augmentation necessary for VTOL aircraft propulsion requirements. Experimental testing has shown that thrust augmenting ejectors can be made more compact by reducing diffuser length with active diffusion boundary layer control employing the Antiseparation Tailored Contour (ATC). Thrust augmentation and internal flow measurements were determined in compact high performance thrust augmentors with various length diffusers. The short ATC/diffusers tested showed significant improvements when compared to previous ejector diffusers. Measured thrust augmentation ratios with an optimum short ATC/diffuser were 10% greater than those with an equivalent straight wall diffuser. Length reductions of 36% were indicated for nominal augmentation ratios of 1.7. The important factors which influence the design and operation of compact thrust augmentor ejector/diffusers have been defined. (Author)

Method and apparatus for the separation of isotope mixtures

Abstract: OF THE DISCLOSURE Method and apparatus for separation of an isotope substance from a mixture of isotope substances such as UF6 by adiabatically decompressing the mixture in vaporous or gaseous form to cool the mixture to a temperature below 100° K and irradiating by an electromagnetic wave selectively absorbed by an isotope substance, passing the mixture after cooling and irradiating in a diffuser at a velocity greater than the speed of sound and decelerating to convert the velocity into pressure with reduced velocity of the mixture. The higher pressure results in substantial reduction in operating costs and capital investment.

An exponential investigation of the behaviour of conical diffusers in turbulent flow

Abstract: Measurements were made of the static-pressure rise coefficient for two representative conical diffusers of 5° and 15° total included angle (both of area ratios 2.5 and 5.0), and of total-pressure loss coefficient for the 5° diffuser of area ratio 1.5, 2.5, 3.5 and 5.0, for a range of entrance pipe lengths of up to 146 pipe diameters and for Reynolds numbers of 1×105 and 4×105. Velocity profiles at inlet to the diffusers were varied. A few static-pressure rise measurements were also conducted with high intensity inlet turbulence profiles and their effect on diffuser performance was assessed. Data for mean velocity profiles at both inlet and exit is also presented. Some improvement in static pressure recovery was obtained by generating high intensity turbulence at the diffuser entry. The results show clearly that further work in this direction is required.

Metering valve for fluids and gases into fluid - esp dissolved chemicals into water for use or drinking

Abstract: An apparatus for injecting metered quantities of fluids or gases into a streaming fluid, esp. dissolved chemicals into water for drinking or other purposes, consists of a spring-loaded baffle producing in the main fluid line a positive or a negative pressure gradient; a branch line taking a part of the main flow, and a vessel connected to the branch line by way of a metered flow line along which the metered additive is drawn by the action of the pressure gradient. The baffle is as is usual, linked to an adjustable needle valve which regulates the open section of the branch line. this is aligned coaxially with the main flow line and has a restriction into which the metered flow line opens. The needle valve has exactly the same conical form as ther outlet of the branch line acting as a diffuser, into which the valve needle projects. The baffle fits with its tapering bore on the outer contour of the diffuser and is displaced axially along its surface. Even with the smallest amounts of the additives, there is a constant interedependance of the metered quantity and the throughout volume which are directly proportional to each other.

Apparatus for separating remanent reedblades from tumbling media

Abstract: Apparatus for and method of separating elongated articles having certain aerodynamic properties from a mixture containing contaminating particles of random shape is disclosed wherein a housing is diagonally divided into upper and lower chambers with a separation apparatus communicating between the chambers. The separation apparatus includes a funnel disposed within the upper chamber, a diffuser tube disposed within the lower chamber and a tubular neck connecting the funnel to the diffuser tube. A hopper is disposed above the funnel for dispensing the mixture to the funnel. A fluid, such as air, is forced into the lower chamber at a sufficient pressure to establish a predetermined flow rate through the diffuser tube and tubular neck to the base of the funnel. This flow rate is adequate to create a "fluidized bed" in the mixture, at the base of the funnel, permitting the articles and contaminating particles to move relative to each other. As a result, the elongated articles align themselves with the flow and, ultimately, present a sufficiently reduced cross section to the flow that they are no longer supported by the flow. Consequently, they fall through the diffuser tube to the lower chamber; whereas the randomly shaped contaminating particles are supported by the flow and are carried into the upper chamber by the flowing fluid.

Effects of Rotation on Diffuser Flow

Abstract: The flow pattern in a rotating, radial passage is largely affected by the flow conditions, rotational speed, and geometrical configuration of the channel. In this report the velocity distribution including primary and secondary flows as well as the pressure distribution in a rotating, conical diffuser, with the opening angle of 2θ=10° and the area ratio of 4:1, is studied. The following results are obtained; (1) With the channel rotation the velocity near the pressure side is increased, while the velocity near the suction side is decreased. (2) When the rotational speed exceeds a certain limit, separation begins on the suction wall and the pressure recovery in the diffuser is largely reduced.

Effect of porous injection and suction on the operation of a stalled conical diffuser

Abstract: The influence of porous injection and suction on the drag, pressure recovery, and efficiency of a conical diffuser in the stalled flow regime is studied experimentally

Spray device for main fluid mixed with input gas and additional fluid - has collector and diffusor type additional spray nozzle with attachments to main chamber for input of fluid

Abstract: A spray device for dispensing a main fluid jet which has an additional gas or fluid component mixed in with it, has a main spray nozzle for dispensation of a fluid spray situated within a vibratory chamber having a collectro jet or nozzle lying co-axial to the main jet. The collector jet is of very narrow cross section and lies upstream of the main jet. Operating in a diffuser type manner. The cross section minimum of the collector jet is smaller than that of the main jet and has at least one attachment to the vibratory chamber for input of the gas or additional fluid component.

Passive flutter suppression

Abstract: References Huo, S., "Optimization Based on Boundary Layer Concept for Compressible Flows," Transactions of the ASME, Journal of Engineering for Power, Vol. 97, April 1975, pp. 195-206. Runstadler, P. W. Jr. and Dean, R. C. Jr., "Straight Channel Diffuser Performance at High Inlet Mach Numbers," Transactions of the ASME, Journal of Basic Engineering, Vol. 91, Sept. 1969, pp. 397-422. Dolan, F. X. and Runstadler, P. W. Jr., "Pressure Recovery Performance of Conical Diffusers at High Subsonic Mach Numbers," NASA CR-2299, Aug. 1973. Stratford, B. S. and Tubbs, H., "The Maximum Pressure Rise Attainable in Subsonic Diffusers," Journal of the Royal Aeronautical Society, Vol. 69, April 1963, pp. 275-278.