Showing papers on "Diffuser (thermodynamics) published in 1986"

Pneumatic powder ejector

Abstract: The invention is in a pneumatic powder ejector comprising a suction stage and an injection stage. The suction stage includes a suction chamber (16), a venturi (14) communicating a primary gas to the suction chamber and a lateral suction input (18) offset in relation to the downstream end of the venturi. The injection stage includes a nozzle (22), an injection chamber (36) and a diffuser (38). The stages are located within a coaxially of the body of a tubular ejector. The nozzle includes a path for powder and primary gas between the suction chamber and diffuser, and is formed to provide a flow path of reduced dimension to communicate a secondary or entrainment gas between the diffuser and injection station.

Visualization of automotive catalytic converter internal flows

Abstract: Internal flow details of a prototype dual-bed monolith converter were determined in water-flow visualization tests run on a full-scale transparent acrylic model. Using steadily flowing water seeded with a small quantity of tracer particles, fluid motion within transparent sections of the flow model was deduced from particle pathlines illuminated with a thin plane of laser light. Flow in the inlet transition separated from the diffuser walls and impinged as a constant-diameter jet on the leading face of the first monolith. Velocity profiles from streak photographs showed that the level of flow maldistribution in the first monolith was a function of Reynolds number.

Film coolant passage with swirl diffuser

Abstract: The wall of a hollow turbine airfoil has a longitudinally extending coolant outlet slot in its external surface which intersects, along its length, a longitudinally extending cylindrical channel within the wall Metering passages extend from the inside surface of the airfoil wall to the cylindrical channel and direct a metered amount of coolant into the channel in a manner which results in a swirling motion being imparted to the fluid as the fluid diffuses within the channel The coolant is thereupon ejected from the channel through the slot in the external surface as a film on the external surface of the airfoil along the length of the slot The swirling of the fluid within the cylindrical channel helps diffuse the fluid such that the outlet slot becomes completely filled with coolant, whereby a film of coolant is created on the airfoil surface downstream of the slot over the full length of the slot

Structure of self-excited oscillations in transonic diffuser flows

Abstract: Two-component laser Doppler velocimeter (LDV) measurements were made in a supercritical, separated, transonic diffuser flow exhibiting self-excited oscillations. The velocity data were ensemble-averaged with respect to the shock oscillation phase, and maps of various flow quantities were generated. The time evolution of the fluctuating velocity field shows a large, rotating structure that originates near the upstream edge of the separation bubble and is convected downstream. The streamwise velocity fluctuation pattern for the self-excited oscillations resembles the oscillation pattern that occurs when the flow is mechanically excited at the downstream end. Velocity fluctuations calculated from ensemble-averaged core total and static pressure data show good agreement with the LDV data.

Jet pump beam holder/positioner tool

Abstract: Repair apparatus and a method of repair utilized for securing pressure sensing lines to jet pump diffusers in boiling water nuclear reactors is disclosed. Conventional access is made to the reactor with removal of the jet pump inlet mixer to expose the upwardly disposed frustum-shaped diffuser. The diffuser includes a pressure sensing line mounted by a stand off block. It has been found that this pressure sensing line becomes separated from the diffuser due to vibration and accompanying metal fatigue. A repair is effected by introduction of an arcuate beam configured for live support at each end. This pressure sensing line and stand off block is bracketed by the upper end of a beam to register the line to the stand off block. The lower end of the beam brackets the line and stands off from the diffuser at a second introduced stand off block. The line is provided with two points of support to prevent further dislodging vibration. The beam is in turn captured by an elliptical ring clamp encircling the essentially circular section of the diffuser between the beam and its captured line. A saddle on the elliptical ring opposite the clamped beam tensions the ring diameter. The ring clamp fits in a preformed notch on the beam and is disposed normally to the surface of the diffuser from the saddle. This disposition of the ring urges the beam upwardly in latched engagement with the stand off block so as to position the line at the upper end of the beam to the stand off block. A universal beam holder for the remote clamping and release of the beam as well as universal manipulation of the beam in pitch, yaw and azimuth is disclosed. This universal beam holder enables positioning of the beam in the submerged radio-active environment of the reactor. The clamp also enables the beam to be maintained in position with the line and stand off block while the ring clamp captures the beam. When the ring clamp is fastened to the beam by securing of a wedge fitting at the saddle, the universal beam holder releases the beam and is withdrawn. Clamping of the pressure sensing line at two spaced apart points secures against both initial detachment and further vibration damage.

Near-wall velocity distributions within a straight conical diffuser

Abstract: The measured mean velocity profiles at the various stations along a conical diffuser (8° total divergence angle) were found to consist of log regions, half-power law regions and linear regions. The describing coefficients for the inner half-power law region (which followed a rather narrow log region) differed from the standard values due to the axi-symmetric geometry and lack of moving equilibrium of the flow as it attempted to adjust to a varying adverse pressure gradient. However, these coefficients (like those for the linear region) correlated with the local wall shear stress and the kinematic pressure gradient.

Measurements of the Turbulent Boundary Layer in the Diffuser Behind an Axial-Compressor

Abstract: The paper presents boundary layer measurements in a diffuser behind a one-stage axial-compressor for the case of nearly axial outlet flow-direction from the blades. According to the results, three-dimensional effects caused by the compressor-blading have a great influence on the character and development of the turbulent boundary layer and must be included in methods to predict the diffuser flow.Copyright © 1986 by ASME

Numerical simulation of swirling flow in diffusers

Abstract: SUMMARY A reduced form of Navier-Stokes equations is developed which does not have the usual minimum axial step size restriction. The equations are able to predict accurately turbulent swirling flow in diffusers. An efficient single sweep implicit scheme is developed in conjunction with a variable grid size domain-conforming co-ordinate system. The present scheme indicates good agreement with experimental results for (1) turbulent pipe flow, (2) turbulent diffuser flow, (3) turbulent swirling diffuser flow. The strong coupling between the swirl and the axial velocity profiles outside of the boundary layer region is demonstrated.

Process and device for metering pulverulent materials

Abstract: The invention is in a pneumatic powder ejector comprising a suction stage and an injection stage. The suction stage includes a suction chamber (16), a venturi (14) communicating a primary gas to the suction chamber and a lateral suction input (18) offset in relation to the downstream and of the venturi. The injection stage includes a nozzle (22), an injection chamber (36) and a diffuser (38). The stages are located within and coaxially of the body of a tubular ejector. The nozzle includes a path for powder and primary gas between the suction chamber and diffuser, and is formed to provide a flow path of reduced dimension to communicate a secondary or entrainment gas between the diffuser and injection station.

Three-dimensional flow effects in a two-dimensional supersonic air intake

Abstract: The internal flow in a two-dimensional mixed compression intake having focussed internal compression was examined experimentally at its design Mach number of 3.05, using pressure instrumentation and flow visualization. A pair of streamwise vortices was identified, which apparently resulted from interaction of the sidewall boundary layers with the internal shock system and which, depending on detailed geometry, could dominate the flow in the subsonic diffuser. It is argued that similar flows could exist in a variety of intakes designed for supersonic flight, with implications for both turbine and ram compression engine applications.

Improved film cooling passages with step diffuser

Abstract: A film cooling passage through the wall of a hollow airfoil for a gas turbine engine has a metering section communicating with the interior of the airfoil for directing a metered amount of coolant through the passage in a first direction, followed by a mixing section to create turbulence in the flow as it leaves the metering section, followed by a diffusing section leading to the passage outlet at the outer surface of the airfoil. The mixing section comprises a sudden jog or step in the flow path of the fluid to suddenly disrupt its forward momentum in the first direction and to create turbulence therein whereby the fluid is more readily able to spread out within the following diffusing section and therecy stay attached to more widely diverging diffusion section walls. Wider diffusion angles in the coolant passage permits the same amount of coolant to be spread out over a wider area of the surface of the airfoil.

Compressed-air blowing device

Abstract: The invention relates to a Compressed air blower with a pistol grip-like handle 2, with a compressed air connection element and an air valve, on which a carrier body is arranged with a vortex tube 15th At its one end portion is a cold-air nozzle 18 is coaxial with the central axis of the vortex tube 15 through hole and at the other end portion is an adjustable hot-air nozzle 21 is formed with a coaxial to the central axis of the vortex tube 15 through hole. The cold-air nozzle 18 is associated with a swirl chamber having at least one tangentially directed into the vortex chamber interior aperture. The vortex tube 15 is connected via a channel 14 with the compressed air connection member. The swirl chamber 40 is formed with a central opening as being located on the cold air nozzle 18 flange, a pipe socket for supporting the flange and on the other side, an outer circumferential edge web with a central recess is arranged on one side thereof, tangentially in serving as swirl chamber inner space in the recess opens slit-shaped grooves are formed. The opening of the nozzle body of cold air nozzle 18 is formed as a diffuser. The cold-air nozzle 18 and the hot air nozzle 21 are respectively connected to a muffler 82, releasably connected to the 83rd

Annular nozzle and process for its use

Abstract: A synthetic or fuel gas mixture containing hydrogen and carbon monoxide is made by the partial oxidation in a free-flowing hollow reactor of a slurry of solid carbonaceous fuel in a liquid carrier admixed with a gas containing free oxygen using a nozzle in which an annular slurry stream is enveloped between central and annular streams of high velocity gas. A uniform atomized admixture of solids, liquids and gases is formed by impinging the annular slurry stream on a downstream nozzle diffuser, and then transported through an exit orifice at an accelerated velocity to further atomize the admixture. The nozzle preferably has a slurry passageway (32) formed of two elongate segments (32a, 32b), the upstream segment (32a) being of greater cross-sectional area than the downstream segment (32b). The nozzle also is of general use in mixing a slurry with a gas.

Low-speed performance of an axisymmetric, mixed-compression, supersonic inlet with auxiliary inlets

Abstract: A test program was conducted to determine the aerodynamic performance and acoustic characteristics associated with the low-speed operation of a supersonic, axisymmetric, mixed-compression inlet with auxiliary inlets. Blow-in-auxiliary doors were installed on the NASA Ames P inlet. One door per quadrant was located on the cowl in the subsonic diffuser selection of the inlet. Auxiliary inlets with areas of 20 and 40 percent of the inlet capture area were tested statically and at free-stream Mach numbers of 0.1 and 0.2. The effects of boundary layer bleed inflow were investigated. A JT8D fan simulator driven by compressed air was used to pump inlet flow and to provide a characteristic noise signature. Baseline data were obtained at static free-stream conditions with the sharp P-inlet cowl lip replaced by a blunt lip. Auxiliary inlets increased overall total pressure recovery of the order of 10 percent.

Computer simulation of a wind tunnel test section with discrete finite-length wall slots

Abstract: A computer simulation of a slotted wind tunnel test section which includes a discrete, finite-length wall slot representation with plenum chamber constraints and accounts for the nonlinear effects of the dynamic pressure of the slot outflow jet and of the low energy of slot inflow air was developed. The simulation features were selected to be those appropriate for the intended subsequent use of the simulation in a wall interference assessment procedure using sparsely located wall pressure measurements. It is demonstrated that accounting for slot discreteness is important in interpreting wall pressure measured between slots, and that accounting for nonlinear slot flow effects produces significant changes in tunnel-induced velocity distributions and, in particular, produces a longitudinal component of tunnel-induced velocity due to model lift. A characteristic mode of tunnel flow interaction with constraints imposed by the plenum chamber and diffuser entrance is apparent in simulation results and is derived analytically through a simplified analysis.

Fluid-piston driving device

Abstract: A fluid-piston driving device (1) with a fluid piston (17) which can be accelerated in a gas-bubble expansion space (6) operates in a trouble-free manner with a high thermodynamic efficiency and high discharge frequency because a mechanical valve element periodically closing the fluid inlet (2) and in this way closing the gas pressure space (6) towards the front is eliminated, use being made instead of the dynamic damming effect of high-energy reaction gas bubbles (15) which periodically expand in a diffuser (5) adjoining which is the expulsion tube (3).

Non-condensible ejection system for closed cycle Rankine apparatus

Abstract: An ejection system including a steam ejector 48 having a steam nozzle 54 aligned with a diffuser 56 which defines a outlet from the ejection system. The ejector has an inlet 46, 52 to the interface of the nozzle 54 and the diffuser 56. A normally closed, non-condensible flow control valve 24 has an outlet 36 connected to the ejector inlet 46 and an inlet 32 adapted to be connected to a working fluid flow path 30 of a Rankine cycle apparatus. A motor 40, 42 is provided for selectively operating the flow control valve 24. A steam generating reaction chamber 60 is in fluid communication with the steam nozzle 54 and first and second pressure vessels 62, 64 are provided and adapted to contain a different reactant of a multi-reactant steam producing chemical reaction. A valve 66 controls fluid communication between the pressure vessels 62, 64 and the reaction chamber 60.

Spraying-arm bearing in dish-washing machines

Abstract: In a spraying-arm bearing of this type, having an upright pipe (3) attached to the pressure nozzle of a circulation pump for a water inlet, into which a pipe section which tapers to a nozzle (4) is formed and into which a diffuser pipe (5) is inserted so as to be rotatable, the inlet aperture (6) of the diffuser pipe being arranged downstream of the nozzle outlet aperture (7) and approximately corresponding thereto in cross-section and a lower spraying arm (9) being connected to the widened outlet (8) of the diffuser pipe so as to be fixed against rotation, it is proposed that a channel (12) runs in the outer surface of the upright pipe, the inlet (13) of which channel is arranged on the inside wall of the upright pipe and ahead of the nozzle (4) in the flow direction, and the outlet (14) of which is provided on a pipe section, accessible in the washing container (2), of the outer wall of the upright pipe and can be closed by a rotatable ring (15) arranged concentrically around said pipe section.

Annular diffuser of axial compressor

Abstract: PURPOSE: To prevent the separation of a flow by providing a means of introducing a main air flow having a large kinetic energy to boundary layers which are developed in the vicinities of the inner wall face of the outer cylinder and the outer wall face of the inner cylinder of the inlet part of a diffuser. CONSTITUTION: An annular diffuser 7 is formed with an outer cylinder 5 and an inner cylinder 6 in the lower course position of the final stage stationary vane 4, and an air intake port 8 is formed on the front edge part of the stationary vane 4 and air blow-out ports 9, 10 are connected to the intake port 8. Due to difference in kinetic energy between a main flow part with less loss and the vicinities of diffuser wall faces where a friction loss is large, air flows can be blown out of the air blow-out ports 9, 10 from the air intake port 8. Thereby, the flows in the vicinities of the wall faces of the annular diffuser 7 can be made active, preventing the separation of a boundary layer.. COPYRIGHT: (C)1988,JPO&Japio

Fixed vane arrangement for a variable width diffuser

Abstract: © A centrifugal compressor for a refrigeration or air conditioning system is provided having a variable width diffuser assembly (28) having a movable wall (34) and a plurality of vanes (82). The vanes (82) are angularly disposed relative to the impeller (16) within a critical range of angular values to provide high operating efficiencies and high pressure recoveries over a large operating range.

Three-Dimensional Flowfield Calculation of High-Loaded Centrifugal Compressor Diffusers

Abstract: In this paper a method for calculating inviscid three-dimensional flowfields in vaned diffusers of high-loaded centrifugal compressors will be considered. Following the classical theory of Wu different kinds of streamsurfaces have been introduced. The complete three-dimensional result is approximated by a combination of blade-to-blade streamsurfaces (S 1 surface) and S 2 surfaces between the side walls of the diffuser. The geometry of each of the stream sheets depends on the others. A special curvilinear coordinate system has been introduced to take into account the twisted shape of the surfaces. Because of the expected transonic flow pattern due to the high loading of the considered units, a time-marching procedure is applied for solving the conservative form of the governing equations in each kind of streamsurface. To demonstrate the capability of the described calculation procedure, the flow pattern in a radial diffuser with twisted vanes has been considered. The impeller speed is assumed to be so large that the flow may become transonic behind the impeller exit. Shock waves may therefore occur in front of the diffuser vanes. Pressure distributions have been calculated in several stream sheets and have been compared with available experimental data. Also integral results predicted by this theory have been compared with measured performance maps. A simple method to estimate a diffuser blockage factor will be given. As a conclusion it will be indicated that a good agreement between theory and experiment justifies the application of an inviscid three-dimensional method for calculating essential details of the pressure field in radial diffusers. However, a coupling of inviscid theory and boundary layer theory does not provide a sufficient prediction of the losses.

Improved fluidized patient support apparatus

Abstract: A patient support structure employs fluid pressure to fluidize granular material (40) to provide for patient support, the fluidizable granular material being received within a container (15) atop a fluid diffuser surface (28). Separate plenum chambers (25A - 25G) are located below the diffuser surface (28) with each plenum chamber being connected to a compressor (50) via associated valve-controlled fluid manifolds (26A - 26G). Valve operators (32A - 32G) and a control system provide for phased, e.g. sequential, opening and closing of the valves to permit controlled fluidization of the granular material over a selected portion of the diffuser surface according to a predetermined arrangement.

Unsteady separated boundary layer in a transonic diffuser flow with self-excited oscillations

Abstract: A numerical investigation of two-dimensional unsteady boundary layer in a transonic diffuser flow with self-excited oscillations and strong flow separation by solving the compressible, Reynolds-averaged, thin-layer Navier-Stokes equations with two-equations turbulence model is described Three different meshes with constant streamwise mesh distribution and varying vertical mesh distribution were used Results obtained indicate that a refinement of mesh studied here has minimal effect on the mean boundary layer flow but significantly increases the amplitude of oscillation of all flow variables Comparisons of unsteady wall pressure, velocity profile, terminal shock, and separation pocket among computations and with experiment are presented

A Study on the Axially Curved Mixed-flow Vaneless Diffusers

Abstract: From a view point of machine dimension, the axially curved mixed-flow diffuser has a large benefit compared with the purely conical of the radially curved mixed-flow diffuser. In the present study, the flow pattern and pressure recovery in the axially curved mixed-flow diffusers are experimentally examined and the results are compared with those of the purely conical diffusers. The pressure recovery factor and diffuser effectiveness of the axially curved diffuser were low compared with the purely conical diffuser, but the difference between them was small. By use of guide fences at the inner wall, the flow in the axially curved diffuser was rectified and a favorable performance was obtained.

Pumping systems and control means therefor

Abstract: A control device for a pumping system incorporating fluidic devices has an air inlet 19 leading to a convergent/divergent nozzle 40 producing supersonic flow A compressive shock wave 43 is produced just upstream of an intake 41 of a diffuser 42 An outlet from chamber 46 may go to vent or a jet pump Spaced oblique compressive shock waves can be produced in a device with an Oswatitsch intake Fig 5 (not shown) The device can be used in a pumping system for example one incorporating a reverse flow diverter

A Preliminary Study of Annular Diffusers with Constant Diameter Outer Walls (Suitable for Turbine Exits)

Abstract: A systemmatic series of tests has been conducted on a family of annular diffusers where the outer casing is maintained at constant diameter. Such a diffuser is typical of turbine exits. Data, in the form of static pressure recovery coefficient is plotted against diffuser length for several different designs of centerbody closure.It has been shown that such diffusers can have short length centerbodies for which a set of design guides has been established.Copyright © 1983 by ASME

A Theoretical Study of Impeller and/or Vaneless Diffuser Attributed Rotating Stalls and their Effects on the Whirling Instability of a Centrifugal Impeller

Abstract: Fluid forces on a centrifugal impeller rotating and whirling in a vaneless diffuser are analysed on the assumption of a two-dimensional inviscid flow. It is assumed that the number of impeller vanes is infinitely large and that the loss in the impeller can be estimated from the steady hydraulic and incidence losses taking into account the delay time of the loss. Further, the pressure at the outlet of the diffuser is assumed to be constant. On these assumptions impeller and/or diffuser attributed rotating stalls are observed, and the effects of parameters affecting the stalls are discussed. It is found that both stalls may cause the whirling instability of a centrifugal impeller.

Blade diffuser of centrifugal air blower and compressor

Abstract: The utility model belongs to a universal machine, and the shape of the inlet edge of the blade of a blade diffuser is arranged to be a curve shape or a folding line shape according to the actual character of the air flow distribution on the outlet of an impeller. The width of the inlet edge of the blade of a blade diffuser has different diameters and geometric angles. The maximal inlet diameter and the maximal inlet geometric angle are positioned at a distance of a=0.55-0.75b 3 from the side edge of a wheel cover. The minimum inlet diameter and the minimum geometric angel are positioned on the side edge of the wheel cover, of which the inlet diameter is unequal to that of the side edge of a wheel disc, as diagrammatic presentation showed. As a result of reducing shock loss, compared with diffusers having same design parameters in prior art, the utility model obviously improves stage efficiency, obviously decreases surging flux, and obviously enlarging the range of steady working condition.

System and method of controlling compressor surge

Abstract: A method and system for preventing or controlling surge in a compressor 14 having a vaned diffuser 18 measures (at 56 and 58) the static pressure differential laterally across a diffuser plane 20 and derives from that differential and from a reference static pressure (at 70) a function of those three pres­ sures which gives an indication that the compressor is ap­ proaching a surge condition. In consequence, a bleed valve 52 is controlled so as to increase the flow through the compressor to tend to avoid the surge condition even if the load demand from the compressor is not sufficient for that purpose.