Showing papers on "Diffuser (thermodynamics) published in 1985"

Air conditioning apparatus

Abstract: An air flow rate sensor and throttle valve which controls the opening of a duct in accordance with the detection signals from the air flow rate sensor are provided in a control duct between a supply chamber utilizing double ceilings and the air diffusers in the supply chamber. The quantities of air fed from the respective air diffusers can be equalized or can be set to the desired values. In this case, since the air blowing can be automatically controlled for each diffuser, it is not necessary to individually adjust the quantities of air for the respective air diffusers after the installation of the air conditioner, thereby eliminating the adjusting works of the air diffusers.

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 thereby 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.

Fluidized patient support apparatus

Abstract: A patient support structure that employs fluid pressure to fluidize granular material for patient support. Fluidizable granular material is received within the structure atop a fluid diffuser surface. Separate plenum chambers are located below the diffuser surface with each plenum chamber being associated with valved fluid manifolds. Operators are associated with the valves and a control system for sequential or otherwise 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.

Low noise fan

Abstract: A fan assembly provides for the compact and efficient movement of ambient air in areas requiring very low noise generation. In this new configuration, stationary turning vanes are placed at the air inlet followed by a sound cell, axial discharge fan and short axial (vaned) diffuser splitter sections. The stationary turning vanes induce a predetermined air rotation which provides a smooth rotating air flow into the rotating fan blades. The stationary turning vanes also block radiated noise from discharge through the air inlet and support the fan motor. The fan blades impart an opposite rotational momentum just sufficient to obtain an axial or nearly axial velocity discharge increment. The resulting axial fan discharge velocity is slowed in the short diffuser sections where diffuser vanes also block rear noise radiation. The slowed but pressurized air can now enter into an air distribution system with significantly reduced fan generated noise. Further noise reductions can be provided by inlet sound baffles, outlet acoustic diffuser splitters, and acoustic absorption materials in the inlet and short, rear axial diffuser short sections.

Gas compressor for jet engine

Abstract: A gas compressor is provided which can be utilized in a jet engine for propulsion of a flight vehicle at velocities ranging from static to very high Mach numbers. The jet engine includes a housing with an inlet, a mixing chamber in fluid communication with the inlet, a diffuser section in fluid communication with the mixing chamber, a combustion chamber in fluid communication with the diffuser section and an outlet in communication with the combustion chamber. Auxiliary gas injection nozzles located downstream of the mixing chamber direct a high velocity gas stream toward the outlet to induce a region of sufficiently low pressure within the mixing chamber to cause a supersonic flow of gas from the inlet section through the mixing chamber. Cryogenic fuel is injected into the mixing chamber to modify the stagnation enthalpy, pressure and temperature of the supersonic flow therethrough. Fuel is injected into the combustion chamber where the mixture of the compressed air flow from the diffuser and the fuel is ignited to produce thrust. The outlet is adjustable to provide the amount of back pressure required in the combustion chamber for stable operation.

Numerical simulation and comparison with experiment for self-excited oscillations in a diffuser flow

Abstract: This paper describes numerical simulations of self-excited oscillations in a two-dimensional transonic diffuser flow obtained by solving the Navier-Stokes equations with a two-equation turbulence model Comparisons were made between the computational results and experimental data For the mean flowfields, the agreement between computation and experiment is good for the wall pressures, shock location, and the separation and reattachment points However, the thickness of the computed recirculation zone is about 50 percent of the measured thickness For the fluctuating flowfields, a great deal of qualitative similarity exists between the computation and experiment; however, the predicted oscillation frequency is about 50 percent higher than the measured value The formation of a succession of downstream-traveling counter-rotating vortices, as seen experimentally, is also vividly displayed in the numerical results

Analysis of unsteady inviscid diffuser flow with a shock wave

Abstract: A finite difference scheme with a shock-fitting algorithm has been used to investigate unsteady inviscid now with a shock in an inlet diffuser. The flowfield consists of three different regions: the supersonic and the subsonic regions, and a region containing both air and liquid fuel droplets, separated by a normal shock wave and a fuel injection system. The analysis is based on a two-phase, quasi-one-dimensional model. The response of a shock wave to various disturbances has been studied, including large-amplitude periodic oscillations and pulse perturbations.

Diffuser construction for a centrifugal compressor

Abstract: Constant flow width through the last stage diffuser of a centrifugal compressor is maintained against widening by the forces of differential pressure via a diffuser defined between oppositely positioned radial faces of a diaphragm and an annular diffuser plate secured spaced from the diaphragm at the desired width. Although slight movement occurs in the compressor components, the width of the diffuser flow passageway is not affected since its width is fixed and the diffuser plate is free to move because of the pressure balance provided by the annular cavity and vent holes extending through the plate.

The prediction of separated flow using a viscous-inviscid interaction method

Abstract: The separation of boundary-layer flow from a wing or in a diffuser usually defines the limit of efficient operation, so it is important that the onset and development of separated flow can be predicted. The calculation of the interaction of the shear layout close to an aerofoil with the external inviscid flow has offered an attractive alternative to solving the Reynoldsaveraged Navier Stokes equations for attached flow: the interaction method is much faster. In this paper it is shown how the interaction approach can be extended for use with separated flows and the development of a practical method is described. The calculation of the shear layer through the singularity at separation is accomplished by using an inverse mode. Beyond separation the empirical definition of a new family of velocity profiles allows an integral calculation of the shear layer to proceed up to the reattachment. The solutions for the shear layer close to the aerofoil are matched to the external inviscid flow by a ‘semi-inverse’ method. A careful examination of the stability of this method leads to rapid convergence for separated and attached flows. As an illustration the stall and post stall behaviour of a twodimensional aerofoil is predicted and compared with experimental results.

Spray nozzle, particularly adapted for spray guns

Abstract: The nozzle of the invention comprises a rotary element placed within a central body and traversed by a channel having a spray orifice, a safety tip placed on the front of the nozzle and an adapter placed between the central body and the diffuser of the spray gun. The seal between the nozzle and the diffuser is provided by a joint, the front part of which has ribs introduced into corresponding grooves in the rotary element to assure appropriate positioning.

Negatively Buoyant Flow in a Diverging Channel

Abstract: Negatively buoyant (plunging) flow from a horizontal, constant width channel into a diverging channel has been studied in the laboratory. The study was undertaken to provide information on reservoir inflow and discharges onto beaches. The flow is a diffuser flow, and as a result, the boundary layer in a diffuser decelerates and thickens rapidly. In addition to being a diffuser flow, the flow studied is subjected to two other major effects. One of these is the shear stress on the channel bottom which causes the development of a boundary layer and vorticity in a vertical plane. The second is buoyancy which can strongly affect the distribution of flow in the diffuser. The paper discusses the experimental study, experimental facilities and variables, classification scheme, and experimental results.

Calibrating apparatus and method for a movable diffuser wall in a centrifugal compressor

Abstract: An apparatus and method is provided for initializing and calibrating a microprocessor controlled refrigeration system including a centrifugal compressor having a variable width diffuser section.

Air-conditioning system for motor vehicles

Abstract: An air-conditioning system for motor vehicles has a heat exchanger for heating fresh air, an air diffuser box with defroster nozzle, foot space nozzle and/or side nozzle and a fresh-air duct for leading the fresh air, bypassing the heat exchanger, to a central nozzle In order to obtain a low overall height of the air-conditioning system with low internal resistance for the hot air flowing through, the diffuser box is arranged directly on the heat exchanger and the fresh- air duct is led to the left and right past the heat exchanger in two separate branch lines

Centrifugal compressor with injection of a vaporizable liquid

Abstract: An assembly for producing wet compression of gas being compressed in a centrifugal-type, multistage gas compressor having an impeller, a diffuser "downstream" of the impeller, and a cross-over channel connected to the downstream end of the diffuser includes a plurality of liquid jets for injecting a vaporizable liquid such as water into a gas stream undergoing compression. The liquid jets are positioned axisymmetrically about the longitudinal axis of the compressor shaft and are adapted to inject liquid into the diffuser substantially upstream of the cross-over channel, and, in a preferred embodiment, have a radial spacing from such axis of about 1.05 to 1.1 times the maximum radius of the compressor impeller. The invention attains a marked increase in vaporization of the injected liquid, providing better compressor performance and reduced wear of compressor internal parts.

An Investigation of High Performance, Short Thrust Augmenting Ejectors

Abstract: The design of air-to-air, thrust augmenting ejectors having short curved wall diffuses utilizing boundary layer control is discussed. The design is achieved by an inverse method which uses the vorticity at the diffuser inlet as a flow parameter in the analysis. Three diffusers having ejector length-to-mixing chamber diameter ratios of approximately 6:1 and mixing chamber inlet area-to-primary nozzle area ratios of 20:1 and 40:1 were designed and tested. A new high level of performance was analytically predicted and achieved experimentally. Comparisons between predicted and observed performances, velocity distributions and pressure distributions are presented.

Tests of wall suction and blowing in highly offset diffusers

Abstract: Tests were conducted in the Boeing Diffuser Test Facility to investigate the effect of centerline offset, wall suction, and blowing on diffuser performance. Effects of offset were studied using a family of two-dimensional diffusers. Effectiveness of wall suction and blowing in controlling the diffuser boundary layer was investigated initially with the highest offset two-dimensional diffuser. This was followed by a more detailed investigation of wall suction and blowing using a three-dimensional offset diffuser model. Configuration variables included centerline offset, hole area for distributed suction, and blowing slot height. Diffuser exit total pressure profiles and longitudinal wall static pressure distributions were measured to determine diffuser overall performance and obtain an indication of local flow behavior. Test results indicate that good performance can be achieved for diffusers with large offset by using small amounts of wall suction or blowing upstream of the separation point.

Ram constriction vane diffuser for jet engine

Abstract: A ram constriction vane diffuser adapted as an air intake of an air plenum-engine pod wherein vertical multiple vanes are fitted on the vertically inclined air intake opening and include fixed vanes positioned adjacent the centerline portion of the air plenums which define an envelope for the airflow including nozzles locate on both sides of a jet engine, a plurality of deflectable vanes positioned in an equally spaced relationship in the air intake openings on both sides of fixed vanes, and wherein each deflectable vane has a leading edge and a drivable trailing section pivotally mounted on the rigid leading section of the deflectable vane and with the drivable trailing sections of each vane and with an actuator for adjusting the angle of the deflectable vanes relative to the freestream air flow for enabling the drivable trailing section of each vane to be turned away from a parallel position to the centerline of an engine suction diffuser, which is the original position thereof for speed flight, to reduce the area of the air intake openings to produce oblique ram-airstream adjacent the engine suction diffuser intake and with each ram-airstream flowing in a tangentially constricted path at critical pressure which forms a convergent-divergent freestream throat and a ram pressure stream in the air plenum on each side of the engine pod resulting in the velocity of the airstream decreasing with an increase in the static pressure thereof and a gain in the air plenums producing a ram constriction pressure airflow to air-inducing nozzles is shown.

Air intake control for an adjustable air inlet, particularly two-dimensional oblique shock diffuser for gas turbine jet engines for the propulsion of high performance aircraft

Abstract: A variable air inlet includes an air intake duct with upper ramps, an air inlet bottom spaced below the ramp and a movable air scoop lip pivotally secured to the end of the air inlet bottom closer to the opening into the air intake duct. The air scoop lip is pivotally displaceable through two angular operating ranges, a wider one in the subsonic/transonic range and a narrower one in the upper supersonic range. Various control members including computers are used to control the position of the lower air scoop lip. The movement in the subsonic/transonic range is effected in response to the flight machnumber and the aircarft angle of attack based on a given control law. The control in the supersonic range is established in response to a variable demand pressure ratio between the static pressure above the upper ramps and the free stream total pressure, with the variable demand pressure ratio being a function of the actual air scoop lip position.

Downhole fluid supercharger

Abstract: An apparatus for directing "supercharged," i.e., high velocity streams of drilling fluid upward around a reduced area between the apparatus and the borehole. These high velocity "supercharged" streams, by virtue of the Bernoulli effect become very low in static fluid pressure. These high velocity, low pressure streams decrease the hydrostatic pressure at the drill bit and accomplish a more efficient drilling by the bit. What is provided is a main tool body positioned along the drill string intermediate a section of drill pipe and the drill bit. The tool further comprises lower an external body portion which is rotated at a rotational velocity three times slower than the rotation of the velocity of the drill string. There is further provided a fluid jetting and diffuser system allowing the fluid or a portion of the fluid to be jetted out of the wall of the sub at a high velocity exterior to the sub in a reduced area between the sub and wall of the borehole whereby hydrostatic pressure is isolated and the pressure is reduced in that area around the drill bit thus reducing the hydrostatic pressure around the bit, for more efficient drilling. Upon further rotation of the external body portion, a porting system interrupts fluid flow to diffuser ports and allows flow back down into the drill bit area for the necessary washing away of the cuttings as the bit drills into the earth. Simultaneously, the reduced annular area is enlarged, allowing unobstructed passage of drill cuttings.

Apparatus and methods for preventing compressor surge

Abstract: To prevent surge in a compressor, the flow therethrough is automatically altered when the static pressure differential taken laterally across one of its diffuser vanes approaches a magnitude indicative of a surge condition.

Two-dimensional viscous simulation of inlet/diffuser flows with terminal shocks

Abstract: Two-dimensional Navier-Stokes solutions of the flow through three inlet/diffuser configurations with terminal shock systems are reported. Calculations without bleed indicate that the terminal shock location is very sensitive to the outflow back pressure. For cases where there are little or no available experimental results, it becomes difficult to estimate the back pressure that will result in a terminal shock. Estimates based on quasi-onedimensional analysis are not found adequate for complex two-dimensional flows. It is found that since the flow downstream of the terminal shock is subsonic, and what happens at the outflow boundary affects the flow inside the inlet, enough of the subsonic diffuser must be modeled to accurately predict the terminal shock region. The diffuser portion should be fairly long with the outflow boundary occurring in a region of more or less uniform flow to be able to prescribe a uniform back pressure. The second configuration studied was investigated with and without incorporating bleed in the code. It is found that the use of bleed stabilizes the shock location and allows solutions which, without bleed, result in unstarting of the inlet. The third configuration required a significant amount of bleed through the ramp and cowl surfaces (both ahead and behind the throat) to avoid separation and provide uniform flow at the engine-face station. Comparisons are made with available experimental data. Nomenclature h - throat height M = Mach number P = pressure, N/m2 Re = Reynolds number T = temperature, K x = streamwise location from the inlet face a. = angle of attack Subscripts b = outflow boundary conditions / = inflow boundary conditions 0 = stagnation oo = freestream condition

Multi-stage turbo machine

Abstract: PURPOSE:To raise the efficiency of a multi-stage turbo machine without increasing the diffuser diameter, by shaping guide vanes disposed at the diffuser portion of the turbo machine to have a cross section capable of turning fluid flow in the radial direction. CONSTITUTION:Guide vanes 9 are disposed at a diffuser portion 3 of a multi- stage turbo machine at which the gas flow discharged from an impeller 1 is regulated and the velocity of gas flow is reduced, and in order to turn the gas flow in the radial direction, the camber line of the guide vanes 9 is imparted with a camber to approach the radial direction with increasing of the radius. Since, with such an arrangement, the flow of gas discharged from the impeller 1 can be turned in the radial direction, it is enabled to enhance the speed reducing and pressure raising function of the diffuser.

Jet pump, in particular for hot-water heating systems with return-flow mixing

Abstract: A jet pump, in particular for hot-water heating systems or water-heating systems with return-flow mixing has a feeder head which is connected with a housing containing the receptor nozzle 13. The housing (7) contains a mixing tube (14) which is connected via a diffuser if needed with a second line connection (12), is coaxial with an injector nozzle (10) and adjoins the receptor nozzle (13); the mixing tube (14) also extends longitudinally through a chamber (22) of the housing in which at least a third line connection (18) and, if desired, a fourth line connection (19), directed respectively transversely to the mixing tube, discharges. In order to attain, e.g., a substantially reduced operating noise and simultaneously increased efficiency, the discharge opening(s) (20, 21) of the third and, if needed, a fourth line connection (18, 19) are disposed spaced laterally apart from the injector nozzle (10); and a portion of housing chamber, which is embodied in the form of an elongated annular conduit (22) and surrounds the mixing tube (14) is located between the discharge openings (20, 21) of the third (and fourth) line connections (18, 19) and the injector nozzle (10).

A Study of Aerodynamic Performance of Diffusers for Centrifugal Compressors

Abstract: The performance of vaneless diffusers and the flow distribution discharged from the impellers of various specific speed centrifugal compressors were studied. The experimental results of eighteen different stages showed, that (1) the impeller exit flow distortion in axial direction increased with an increase in specific speed, and (2) the pressure recovery of vaneless diffusers for high specific speed compressors was extremely low compared with the value expected by an ideal two dimensional analysis. New type diffusers with half guide vanes on the shroud side wall are proposed in order to improve the pressure recovery of the diffuser under the distorted inlet flow condition. The results show that the pressure recovery of diffuser under distorted inlet flow is considerably improved by half guide vanes, and the best height of the guide vanes is a little less than one half the diffuser width.

Venturi powder pump

Abstract: A powder pump for pumping air entrained solid particulate powder material comprising a pneumatic coveyor line (38) within which there is located a low pressure venturi pumping chamber (64). This venturi pumping chamber is intersected by a powder supply passage (74) through which powder is drawn into the conveyor line. Located within the powder supply passage is a tubular powder diffuser (100) through which metering air flow is directed into the powder supply passage to control the rate of flow of powder through the powder supply passage and into the venturi pumping chamber (64). The metering air flow passes through the diffuser at an angle directed toward the venturi pumping chamber and flows into the powder supply passage (110) of the diffuser (100) at an angle tangential to the flow passage.

Process and device for cleaning the surfaces of filter media

Abstract: The invention relates to a process and to a device for cleaning the surfaces of filter media by compressed air blasts. As Figure 1 shows, a Venturi nozzle is integrated into the conventional compressed air reservoir assigned to the filter housing, which Venturi nozzle produces an increase in velocity of the precompressed air. The increased velocity leads to the entrainment of secondary air from the clean air chamber of the filter housing into the main Venturi nozzle. The pressure pulse units having an integrated magnetically-controlled valve and central Venturi nozzle situated adjacently produce the compressed air reservoir. The upstream Venturi nozzle has a relatively moderately constricted first part and relatively moderately expanded diffuser part.

Rotating flow pump with a feed pump unit formed as an ejector

Abstract: A rotating flow pump such as a centrifugal pump is provided with a feed pump unit formed as an ejector. The feed pump unit comprises an inlet portion, a nozzle, and a diffuser arranged in succession, and the diffuser is connected to the inlet opening of the flow pump. The inlet portion, the nozzle, and the diffuser of the ejector are situated in a plane perpendicular to the shaft of the flow pump. The diffuser comprises an inner channel of a uniformly increasing flow cross section at least over part of its length. Furthermore the diffuser comprises an outer jacket situated substantially coaxially about the above channel. Thus the jacket is formed in such a manner that a substantially 180° almost mushroom-shaped turning of the flow direction for the liquid flowing through the diffuser is obtained at the same time as a uniformly increasing flow cross section--seen in the flow direction--is obtained within the annular chamber between the channel and the jacket. In this manner the diffusing capacity of the ejector can be very high at the same time as the flow pump takes up relatively little room.