Showing papers on "Diffuser (thermodynamics) published in 1975"

Electrostatic spray apparatus

Abstract: An improved electrostatic spray gun for the deposition of powdered coating material on a workpiece is disclosed. The spray gun includes a housing having a barrel to which a nozzle is attached for directing the powdered material to the workpiece. A charging electrode, which is connected to a high voltage power supply, is mounted on a diffuser assembly which is clamped between the nozzle and the housing, on which the nozzle is threaded. A regulated gas flow supplied through the housing and the diffuser assembly provides a gas shield around the charging electrode to prevent a buildup of the coating material on the electrode. A novel pneumatic safety interlock continuously monitors the pressure of the gas supplied to the diffuser assembly. The interlock turns off the high voltage power supply and a pump for the coating material in response to a drop in such pressure resulting from a loose nozzle.

Laser anemometer measurements in flames with swirl

Abstract: An experimental study has been made of flow fields in turbulent swirling jets under flame and no-flame conditions. Natural gas was supplied separately to a burner with a divergent exit of 20°. The recirculation zone penetrated into, the diffuser at a swirl number of 0.3. Time mean axial, radial and circumferential components of velocity and rms velocity fluctuations were measured. The laser anemometer operated in the double Doppler mode and frequency shifting was obtained with a rotating diffraction grating. Signal processing was carried out by an electronic single particle pulse counter. Substantial changes in flow patterns were detected as a consequence of combustion, and the kinetic energy of turbulence per unit mass under flame conditions was higher than in the corresponding cold conditions in almost all regions of the flame.

Ejector mixer for gases and/or liquids

Abstract: An ejector mixer for gases and/or liquids comprising three coaxial nozzles in communication with a mixing chamber that merges into a diffuser. One component to be mixed is fed into the middle annular nozzle, while the other component is supplied via the outer and the inner annular nozzle, so that the stream or the first component, upon entry into the annular mixing chamber, will be confined by the two streams of the second component.

Behavior of Severely Asymmetric Flow in a Vaneless Diffuser

Abstract: There is controversy about the mechanism of decay of the asymmetric flow in the vaneless diffuser of centrifugal blowers. In order to clearly observe the behavior of asymmetric flow, every other flow passage of a centrifugal impeller is blocked with a punched plate so that a severely asymmetric flow is induced. The flow behavior in the vaneless diffuser is measured with unsteady flow measuring instruments as well as with conventional instruments for steady flow. The experimental results indicate that there are some flow phenomena which cannot be explained by the conception of mixing process. Such flow phenomena can be explained quantitatively as the isentropic energy exchange between relative streamlines due to the circumferential pressure variation. In addition, the wall roughness of the vaneless diffuser is changed, and the influence of the wall friction on the total pressure loss is compared with the predictions based on the two controversial hypothesis. While these data are handled, it is recognized that the time average total pressure is considerably larger than the mass average total pressure for a severely asymmetric flow. Therefore, if instruments for steady flow measurement are used near the impeller exit to measure the total pressure, the impeller efficiency may be overestimated and the diffuser efficiency may be underestimated.

Vaned diffuser and method

Abstract: My invention relates to centrifugal compressors, more particularly to compressors of a known type, in which air enters the compressor rotor parallel to its axis of rotation, engages an inducer portion of the compressor rotor blades which is generally helical, in which the air is accelerated tangentially, and then proceeds through an impeller portion of the rotor formed with substantially radial vanes in which the air is further accelerated tangentially, leaving the rotor periphery with a high tangential velocity. In such a compressor, the air discharged from the rotor is received in a diffuser in which the velocity head of the air is largely converted to static head by a so-called diffusion process of reducing the air velocity. The air is then directed to the outlet or outlets of the compressor. It is to be understood, however, that this invention is concerned not with the rotor but rather with the vaned portion of the diffuser. The principle object of my invention is to increase the compressor efficiency and essentially eliminate surge problems, thereby reducing the power required to drive the compressor which results in various advantages to any machine that requires a continuous flow of high pressure air. This objective is achieved by several features. First, by defining a method to design the shape of the leading edge of the diffuser vanes, thereby reducing the entering shock loss and also the down stream flow separation; second, by defining a method of shaping the vanes and the passage walls such that the shape will cause a suitable rate of pressure rise that will also lessen the causes of flow separation from the passageway, thereby permitting stable operation, without compressor surge, in an operating regime having a higher compressor efficiency.

Fluid-flow assisting devices

Abstract: An inlet line connected to the inlet of a hydraulic pump includes a jet pump having a Venturi nozzle though which the aspired liquid is passed, and into which a coaxial jet of liquid under higher pressure is introduced to raise, by jet-pump action, the pressure of the liquid at the pump inlet. In order to increase the efficiency of pressure recovery in the diffusor part of the Venturi nozzle, fuel under higher pressure than the aspired liquid fuel is also introduced into the flow of incoming fuel through the wall of the Venturi nozzle, at a point preceding the throat, via inlet slots so arranged that, when there is a flow of fuel through the nozzle passage, the Coanda effect of the additional fuel thus introduced causes the thus introduced fuel to form a layer moving along the walls of the throat and diffuser portion of the Venturi nozzle, and separating the stationary surface of the throat and diffusor walls from the flow of fluid obtained by the action of the central jet, thereby counteracting the tendency to wall detachment which in conventional jet pumps is caused by boundary-layer action.

Sequenced orifice fluid supply for occupant restraint system

Abstract: An occupant restraint system for a vehicle including an air bag having a collapsed inoperative condition and an expanded operative condition for restraining movement of an occupant of the vehicle during a collision, a fluid supply, and a diffuser for directing fluid from the fluid supply into the air bag. The fluid supply includes a staged source of fluid for expanding the air bag. Fluid from the first source stage is introduced into the diffuser immediately upon the collision of the vehicle to initiate expansion of the air bag. After a time delay of milliseconds, a greater mass flow of fluid from the second source stage is introduced into the diffuser to complete the expansion of the air bag.

Centrifugal compressor or centripetal turbine

Abstract: A diffuser for a centrifugal compressor or a nozzle assembly for a centripetal turbine comprising a pair of axially-spaced walls defining an annular housing open at its inner and outer peripheries and a plurality of vanes extending between the walls and defining therewith, between adjacent vanes, working fluid passages open to the inner and outer peripheries of the housing, each vane being defined by a pair of partitions having a common edge extending between the housing walls adjacent the inner periphery of the housing and spaced apart circumferentially at positions remote from the inner periphery of the housing.

Eccentric passage pipe diffuser

Abstract: A diffuser is disclosed which provides intersecting passages extending outwardly from an inner circumference which closely surrounds the periphery of the impeller output stage of a centrifugal compressor. The passages are of curvilinear cross-section having entrance throat regions of an eccentric configuration designed to minimize the build-up of shock waves in the fluid flowing from the outlet of an impeller whose blade tips are traveling at supersonic speed. The configuration of the throat region is such that it closely matches the velocity vector profiles of fluid particles which leave the central region of an impeller blade at supersonic velocities and an appreciable angle above the tangential whereas particles leaving near the front and back shrouds of the impeller travel slower at angles approaching the tangential.

Air pump for use in dusty environment

Abstract: Apparatus is disclosed for pumping gases laden with abrasive particles. The pump comprises a cylindrical outer housing within which there are three axially adjacent sections, namely; an inertial bypass inlet; a powered rotor midsection; and an annular exhaust diffuser. The inertial bypass inlet consists of an axially symmetric cone which diverts the heavier sand and dust particles toward the outer walls. Behind the conical deflector is an axially symmetric circular shroud. A rotor within the shroud draws in and accelerates partially clean air from the lee side of the cone while the majority of the sand and dust laden air passes between the shroud and the outside wall. Recombination of the entire airstream occurs at an ejector nozzle serving as an output of the powered rotor midsection. Contaminated air from the ejector nozzle experiences a pressure rise in the annular exhaust diffuser.

Thrust augmenting fluid rectifier for a pulsed combustor

Abstract: A thrust augmenting fluid rectifier for a pulsed combustor comprising ducting having a converging inlet section, a flow redirecting section and a diffuser section, the inlet of the ducting being spaced upstream from the combustor inlet to define a thrust augmentor utilizing the backflow from the combustor inlet as primary fluid. In one embodiment the rectifier ducting extends rearwardly to a chamber that combines it with the combustor outlet. Substantial pressure gain is obtainable making the invention suitable for gas turbine applications.

Aquatic sound generating system for fishing lures

Abstract: The present invention is for fishing lures having a variable pressure diffuser system for generating a particular frequency simulating aquatic sounds. As a fishing lure is pulled through the water, water flows through an entrance venturi into a fluidic diffuser chamber. Also connected to the fluidic diffuser chamber, perpendicular to the normal direction of flow of the fluid, are two control channels. From the fluidic diffuser chamber, the flow of the fluid is exhausted through channels angling off at a predetermined angle from the center line of the normal flow of the fluid through the venturi. The predetermined angle, along with size of the fluidic diffuser chamber determines the frequency at which the diffuser system will self resonate. Fish hooks are attached to the lure having the self resonating system for catching the fish.

Method for Analysis of V/STOL Aircraft Ejectors

Abstract: A digital computer program is described for aircraft ejector performance analyses. The effects on performance of temperature ratios, pressure ratios, specific-heat ratios, pressure losses, and aircraft forward speed are included. Momentum correction factors are computed within the program, and the method by which these are determined for rectangular ejectors with multiple nozzles is described. Theoretical and experimental results are compared for rectangular ejectors employing hypermixing nozzles and microjet nozzles. It is demonstrated that the predictions of thrust augmentation ratio are within 3% of the test data. The effects on performance of pressure ratio, temperature ratio, nozzle spacing, mixing section length, inlet and diffuser performances, and the degree of mixing achieved are presented. The analysis clearly demonstrates the importance of rapid mixing, and the role that the ARL hypermixing nozzle has played in advancing the state-of-the-art of aircraft ejectors.

Comparison of experimental and theoretical boundary-layer separation for inlets at incidence angle at low-speed conditions

Abstract: Comparisons between experimental and theoretical Mach number distributions and separation locations are presented for the internal surfaces of four different subsonic inlet geometries with exit diameters of 13.97 centimeters. The free stream Mach number was held constant at 0.127, the one-dimensional throat Mach number ranged from 0.49 to 0.71, and the incidence angle ranged from 0 deg to 50 deg. Generally good agreement was found between the theoretical and experimental surface Mach number distributions as long as no flow separation existed. At high incidence angles, where separation was obvious in the experimental data, the theory predicted separation on the lip. At lower incidence angles, the theoretical results indicated diffuser separation which was not obvious from the experimental surface Mach number distributions. As incidence angle was varied from 0 deg to 50 deg, the predicted separation location shifted from the diffuser region to the inlet highlight. Relatively small total pressure losses were obtained when the predicted separation location was greater than 0.6 of the distance between the highlight and the diffuser exit.

Experimentally determined aeroacoustic performance and control of several sonic inlets

Abstract: Low speed wind tunnel tests were conducted to determine the aeroacoustic performance of several model sonic inlets. The results were analyzed to indicate how inlet aeroacoustic characteristics were affected by inlet design and operating conditions. A system for regulating sonic inlet noise reduction was developed and tested. Results indicate that pressure losses at forward velocity may be substantially less than those at static conditions. This is particularly true for translating centerbody inlets with the centerbody extended in the approach and landing position. Operation to simulated takeoff incidence angles of 50 degrees was demonstrated with good inlet performance. Inlet sound pressure level reduction was regulation was regulated to within approximately + or - 1 dB by controlling inlet surface static pressure measured at the diffuser exit.

Injection jet pump for central heating - has throughput regulated by means of axially movable disc

Abstract: The pump has a housing with inlets for the liquid being pumped and a pipe connection for the driving fluid. The driving fluid leaves the pipe through side holes and flows round the outside of a cone through the pump throat into the discharge diffuser. An axially movable cone surrounding the fixed cone varies the flow of driving fluid by adjusting the annular space round the solid cone. A disc with a central hole surrounding the outer cone is carried on a bellows and is axially adjustable. Its movement varies the space between itself and the outer cone through which the pumped fluid flows thus varying the throughput.

Gas-blast switch

Abstract: A gas-blast switch embodying a stationary contact element, a movable contact element which is surrounded by an entrainably movable blast nozzle, the inlet side of the blast nozzle being in flow communication with a compression compartment for an extinguishing gas, the compression compartment can be pressurized by the cut-off movement of the switch. Further, there is provided an electrically conductive screening body which is guided along the stationary contact element, the screening body can be shifted out of its cut-off position where it surrounds the stationary contact element by means of the blast nozzle during the cut-on movement. Between the stationary contact element and the screening body in the cut-off position there is provided a through-blowable jacket compartment, the inlet side-internal diameter of which is practically aligned with a blast cone formed by an outlet diffuser of the blast nozzle.

The Choking Pressure Ratio of a Critical Flow Venturi

Abstract: The critical flow venturi has many important applications in the measurement and control of gas flow. In many of these applications, it is desirable to minimize the pressure loss required to maintain critical flow conditions. The performance of the venturi may be characterized by the ratio of outlet static pressure to inlet total pressure just sufficiently small to produce critical flow. This ratio is called choking pressure ratio (CPR). The optimization of diffusers for critical flow Venturis is discussed and suggestions for designs practice are presented. Test results are given for six different diffuser configurations, and a comparison is made with data on 11 configurations from other investigators. This work was done under contract to the National Aeronautics and Space Administration—Marshall Space Flight Center. It is shown that, for the small divergence angles considered, a simply defined diffuser effectiveness parameter is approximately independent of flow conditions and may be used to predict choking pressure ratio. Even very short diffusers greatly improve performance, and, for longer diffusers, critical flow can be maintained at total pressure losses of 5 percent.

Experimental evaluation of a Mach 3.5 axisymmetric inlet

Abstract: Wind tunnel test results for a large scale inlet model designed for Mach 3.5 are presented and compared with analytical predictions. The inlet is an axisymmetric mixed-compression type with a lip diameter of 49.723 cm. The inlet design was developed using analytical procedures. Data are shown for freestream Mach numbers from 0.6 to 3.5. The test results indicate that boundary layer bleed requirements can be accurately predicted. Good agreement was obtained with analytical predictions of the flowfield structure and boundary layer development in the supersonic diffuser yielding high performance at the design Mach number. The highest engine face total pressure recovery at Mach 3.5 was 85.8%; this was obtained at 0.05 Mach tolerance with only 2.8% total pressure distortion and 13.4% bleed. In the started Mach number range from 1.6 to 3.5, the total pressure recovery in the throat, downstream of the terminal normal shock, ranged between 91% and 95%. Total pressure losses in the subsonic diffuser varied from 3% to 13%. The higher losses occuring between Mach 2.5 and 3.2 were believed to be caused by the rapid rate of increase in the area of the diffuser just downstream of the throat, possibly coupled with inadequate centerbody throat bleed. In the unstarted mode at transonic speeds, the maximum inlet flow was over 99% of the theoretical maximum capture mass-flow.

A Note on Diffuser Generated Flow Unsteadiness

Abstract: ) were tried until a best fit was obtained in comparison with the exact solution of reference [6]. The results are shown as data points in Fig. 2 along with the quasi-steady predictions of equations (2) and (3). The "best" fit was determined by en­gineering judgment. Two values are shown for each damping number. The fit in an average sense effectively matched areas in the corresponding responses (see Fig. 10 of [6]) while the fit in the peak sense matched the extremal values of the exact response. The equal value of R

Hermetically sealed valve with fixed diffuser

Abstract: A hermetically sealed valve includes a valve body having an annular seat adjacent the valve inlet with a frusto-conical surface diverging outwardly therefrom toward the valve outlet and a fixed diffuser assembly including a fixed disc guide and a slidable spring biased closure disc. The disc guide has a diverging frusto-conical surface spaced from the first surface to define a high efficiency annular diffuser flow passage. The fluid exposed surfaces of the disc are located upstream of the passage. The closure disc is actuated between an open position and a closed position by an axially movable valve stem acting on a flexible diaphragm. The pressure drop in the diffuser passage at high flow conditions establishes a force differential on the diffuser assembly acting toward the valve seat which is borne entirely by the disc guide thereby eliminating any pull down forces on the closure disc.

Water flow control valve and diffuser for crossflow cooling towers

Abstract: A crossflow cooling tower, water flow control valve and diffuser which includes an open ended inner valve cylinder which moves from a closed to an open position by means of a screw mechanism and allows water to be evenly distributed over a 360° range to all parts of a hot water basin located directly under the valve. The water leaving the valve is directed and proportioned by a series of baffles and a cone to effect a uniform distribution over the basin.

Adjustable stator blade diffuser for centrifugal compressor - has hollow blades with one resilient wall and pressurising means

Abstract: The diffusor has an adjustable cross-sectional flow area. Each hollow stator blade is provided with a resilient wall on the side which is at the shortest distance from the entry side of the adjacent blade and with an inlet orifice for a pressurised fluid. The resilient wall may be spring-loaded to return to its un-deformed condition. The internal pressure in the hollow blade may be controlled as a function of the position of the pre-swirl blades. An advantage, is the fact that separate sealing elements are not essential, since the common control of the diffusor cross-sectional area provides static sealing against the pressure medium.

A pseudo three-dimensional analysis of flows in vaneless diffusers for mixed-flow compressors

Abstract: A solution is given of the equations of motion for inviscid flow with axial symmetry in mixed-flow diffusers of any given geometry. The associated computer programmes have been applied, together with similar programmes for the impeller based on streamline-normal solutions, to predict streamline, velocity and pressure distributions in a variety of vaneless diffusers as follows: (i) radial-flow impeller with radial diffuser; (ii) mixed-flow impeller with pure conical diffuser and (iii) mixed-flow impeller with curved diffusers.The first of these is shown to give essentially stable flow, the second extremely unstable flow and the third conditionally stable flow provided that a suitable combination of initial contraction and hub/shroud profile is adopted.

Pressure jet atomizer

Abstract: A pressure jet atomiser of the centrifugal swirl type wherein a forced vortex is gradually accelerated, by being directed through a smoothly converging passage, and is thereafter refined and thinned. Refining of the vortex occurs in a constant diameter nozzle throat section and thinning is achieved by passage through a smooth diverging diffuser downstream of the throat. A constant spray angle for the thinned vortex is achieved by providing the diffuser with an abrupt set-back.

Performance of vortex generators in a Mach 2.5 low-bleed full scale 45-percent-internal-contraction axisymmetric inlet

Abstract: Steady-state and dynamic flow characteristics associated with two sets of vortex generators having different mixing criteria were determined. The inlet performance with and without these vortex generators is presented. The vortex generators were successful in eliminating separation, increasing area-weighted total pressure recovery, and decreasing distortion. Transmission times obtained from cross-correlations of the wall static pressures and the diffuser exit total pressure showed no effect of the upstream flow characteristics on the diffuser exit pressures when generators were used. Without generators, separation occurred and the upstream pressure characteristics had immediate effects on the diffuser exit pressure characteristics.

Aeroacoustic performance of scale model sonic inlets

Abstract: Various means can be used to vary engine inlet throat areas in order to reduce noise generated at takeoff and approach. Low-speed wind-tunnel tests were performed to evaluate the aeroacoustic performance of two takeoff geometries (cylindrical centerbody and bulb-shaped centerbody) and four approach geometries (bulb-shaped centerbody, annular ring, radial vanes, and step diffuser). The effects of inlet internal lip shape and diffuser length on sonic inlet performance were also investigated. It was found that the single-passage geometries, in particular a cylindrical centerbody takeoff geometry and a bulb-shaped centerbody approach geometry, provide the highest level of aeroacoustic performance. Increasing the inlet lip contraction ratio extends the maximum incidence angle for attached lip flow, while increasing the inlet diffuser length increases total pressure recovery for a given amount of noise suppression.

A General Finite Difference Technique for the Compressible Flow in the Meridional Plane of Centrifugal Turbomachinery

Abstract: There has been an increased concentration of effort recently in the understanding of the complex flow in centrifugal turbomachines, especially industrial machines. Although it is impossible at this time, to model all the phenomena existing in a real machine, it is felt that a systematic approach which makes use of recent advances in computational fluid dynamics, and extends these as further developments occur, will significantly improve our understanding of the flow, and our ability to predict performance and improve efficiency. In this paper, a new general finite difference technique for solving the flow field in the hub-to-shroud plane of any component of a centrifugal turbomachine is described. The technique uses a quasi-orthogonal finite-difference net, and solves the resulting system of equations using a matrix method. Thus the technique offers a stable, accurate computational method, combined with a fixed grid which may be simply applied to the most complex annular passage shape. The results for three numerical examples are presented, a radial to axial inlet, a vaneless radial diffuser and an interstage return bend.Copyright © 1975 by ASME