Showing papers on "Diffuser (thermodynamics) published in 1993"

A valveless diffuser/nozzle-based fluid pump

Abstract: A new valveless fluid pump has been designed and tested. The pump consists of two fluid diffuser/nozzle elements on each side of a chamber volume with an oscillating diaphragm. The vibrating diaphragm produces an oscillating chamber volume, which together with the two fluid-flow-rectifying diffuser/nozzle elements, creates a one-way fluid flow. A micropump prototype with a chamber diameter of 19 mm with conical diffuser/nozzle elements has been built and tested. The maximum liquid flow rate is 16 ml/min and the maximum pump pressure is 2 m H 2 O. The pump frequency is of the order of 100 Hz.

Automatic safety valve and diffuser for nasal and/or oral gas delivery mask

Abstract: A self-regulating valve device adapted for use with respiratory equipment of a type which produces a pressurized flow of breathing gas. The valve device affords automatic access to the ambient atmosphere in the event of respiratory equipment malfunction and includes a primary inlet, a secondary inlet and an outlet. The primary inlet is adapted for connection to a ported exhalation valve which, in turn, is connected to one end of an elongated flexible tube, the opposite end of which is connected to a gas flow generator. The outlet, in turn, is connected to the inlet of an oral, nasal or oral/nasal respiratory mask respectively adapted to cover the patient's mouth, nose or mouth and nose. The valve device further comprises a pressure-responsive valve element for regulating gas flow into the inlet of the respiratory mask. In accordance with a further aspect of the invention, there is additionally provided a diffuser element positioned generally at the valve outlet/mask inlet junction. The diffuser element diffuses or disperses the flow of incoming gas (pressurized or ambient) to the mask, whereby the patient's comfort is enhanced while undergoing treatment for sleep apnea, or other respiratory treatment.

Experimental and Computational Investigation of the NASA Low-Speed Centrifugal Compressor Flow Field

Abstract: An experimental and computational investigation of the NASA Lewis Research Center's low-speed centrifugal compressor (LSCC) flow field was conducted using laser anemometry and Dawes' three-dimensional viscous code. The experimental configuration consisted of a backswept impeller followed by a vaneless diffuser. Measurements of the three-dimensional velocity field were acquired at several measurement planes through the compressor. The measurements describe both the throughflow and secondary velocity field along each measurement plane. In several cases the measurements provide details of the flow within the blade boundary layers. Insight into the complex flow physics within centrifugal compressors is provided by the computational fluid dynamics analysis (CFD), and assessment of the CFD predictions is provided by comparison with the measurements. Five-hole probe and hot-wire surveys at the inlet and exit to the impeller as well as surface flow visualization along the impeller blade surfaces provided independent confirmation of the laser measurement technique. The results clearly document the development of the throughflow velocity wake that is characteristic of unshrouded centrifugal compressors.

Gas turbine engine component with compound cooling holes and method for making the same

Abstract: A gas turbine engine component includes a wall portion with at least one compound cooling hole formed therein between an external surface of the component and an interior plenum. The at least one compound cooling hole includes a non-circular diffuser opening formed by a laser beam with a non-circular cross-sectional area, and a channel with a substantially circular cross-section connecting the diffuser opening and the interior plenum. The channel is also formed by the non-circular laser beam in the same laser drilling operation as the diffuser opening. The cooling hole further includes a transition point at which the compound hole begins to convert from a substantially non-circular cross-section to a substantially circular cross-section. The location of the transition point is controlled by positioning a focal point of the non-circular laser beam to undershoot the external surface of the component by a predetermined distance.

Exhaust system for a turbomachine

Abstract: An exhaust system for an axial flow turbomachine is provided having a diffuser that directs the flow of working fluid from a turbine exit to an exhaust housing having a bottom opening, thereby turning the flow 90° from the axial to radial direction In the exhaust housing, the flow exiting at the top of the diffuser turns 180° from the vertically upward direction to the downward direction The strength of the vortex formed in the exhaust housing as a result of this turning is minimized by orienting the outlet of an outer exhaust flow guide portion of the diffuser so that it lies in a plane that makes an angle with a plane perpendicular to the turbine axis As a result, the minimum axial length of the outer flow guide occurs at a location remote from the exhaust housing outlet and the maximum axial length occurs at a location proximate the opening, thereby crowding the vortex against a radially extending baffle in the exhaust housing

Experimental and Theoretical Analysis of the Flow in a Centrifugal Compressor Volute

Abstract: Detailed measurements of the swirling flow in a centrifugal compressor volute with elliptical cross section are presented. They show important variations of the swirl and throughflow velocity, total and static pressure distribution at the different volute cross sections and at the diffuser exit. The basic mechanisms defining the complex three dimensional flow structure are clarified. The different sources of pressure loss have been investigated and used to improve the prediction capability of one-dimensional mean streamline analysis correlations. The tangential flow loss model under decelerating flow conditions and the friction loss model are confirmed. New empirical loss coefficients are proposed for the exit cone loss model and the tangential flow loss model for the case of accelerating flow in the volute

Device for acting upon fluids by means of a shock wave

Abstract: A two-phase mixture of at least two fluids which is supplied with subsonic velocity through associated feed lines (4, 3) is accelerated to sound velocity by means of a nozzle (2). Upon the exit from the narrowest cross-sectional area (6) of the nozzle (2) the two-phase mixture is expanded in an expansion chamber (10) to supersonic velocity. The two-phase mixture expanded to supersonic velocity is thereafter brought to ambient pressure substantially as a one-phase mixture after flowing off through a diffuser passage (9) by means of a shock wave built up in an outlet channel (8). The outlet channel (8) has a constant cross-sectional area the hydraulic diameter of which is as great as the hydraulic diameter of the narrowest cross-sectional area (6) of the nozzle (2) or amounts to up to the three-fold of this hydraulic diameter. An outlet (11) provided with a relief valve (22) is connected to the expansion chamber (10). After termination of a starting operation a continuous operation appears with the shock wave being stably maintained in axial direction in the outlet channel. In this manner a good mixture of the fluids can be obtained because of the angular flow and the relative velocities of the fluids, by condensation during the transition in the two-phase condition as well as by boiling and vaporization in the range of the supersonic flow and following thereto in the shock wave because of its "shattering effect".

Asymptotic Solutions and Behavior of Outfall Plumes

Abstract: The simple model for a buoyant jet in a flow is presented. The model differs from those presently available in that it is forced to satisfy the limiting cases of a buoyant jet in still water, a nonbuoyant jet in a still fluid, a jet in a coflow, a momentum vortex, and an advected thermal. It reproduces these types of flow by using a spread constant both for the Gaussian and the vortex regions and using published data to determine criteria for the transition from the advected Gaussian to the advected vortex distributions. At the transition the minimum dilution for momentum and buoyancy flux are preserved. The flow from an infinite array of merging buoyant jets from an outfall diffuser is also discussed. When the ambient flow is stationary a method of obtaining a complete solution is outlined. When the cross flow is small the merged flow has the form of an advected two‐dimensional plume. For a larger cross flow the fluid becomes sufficiently stretched such that the lower stable surface is almost horizontal,...

Isolator-combustor interaction in a dual-mode scramjet engine

Abstract: A constant-area diffuser, or 'isolator', is required in both the ramjet and scramjet operating regimes of a dual-mode engine configuration in order to prevent unstarts due to pressure feedback from the combustor. Because the nature of the combustor-isolator interaction is different in the two operational modes, however, attention is presently given to the use of thermal vs kinetic energy coordinates for these interaction processes' visualization. The results of the analysis thus conducted indicate that the isolator requires severe flow separation at combustor entry, and that its entropy-generating characteristics are more severe than an equivalent oblique shock. A constant-area diffuser is only marginally able to contain the equivalent normal shock required for subsonic combustor entry.

Diffuser for hair dryer

Abstract: A diffuser for a hair dryer having an air discharge nozzle, the diffuser comprising a body having a side wall defining a first opening adapted to communicate with the nozzle and a second opening, the body defining an air passage communicable between the first and second openings for conducting therebetween an air flow, a grill overlying the second opening and defining a plurality of discharge openings, a plurality of generally hollow fingers extending from the grill outwardly of the air passage, the fingers defining respective finger discharge openings and respective finger discharge passage portions communicable between the air passage and the finger discharge openings, and a valve for selectively and adjustably controlling the flow of air from the air passage through the discharge openings and the finger discharge openings.

Method and apparatus for mixing fluids

Abstract: A device and method for inducing turbulence in the flow of a fluid in the course of continuous flow process are disclosed. The device comprising a series of chambers (C1, C2, C3, C4) extending along an axis. Each chamber is defined by (1) a cylindrical conduit (2) that extends along the axis and between opposite ends and has a constant internal diameter along the axis; (2) a frusto-conical diffuser (1) that has an internal diameter increasing along the axis from a reduced internal diameter at an inlet (1;) of the diffuser (1) to an internal diameter substantially equal to that of the conduit (2) at an outlet (10) of the diffuser; and (3) a frusto-conical confuser (3) that has an internal diameter decreasing along the axis from an internal diameter substantially equal to that of the conduit (2) at an inlet (3;) of the confuser (3) to a reduce diameter at an outlet (30) of the confuser. The conduit (2), diffuser (1) and confuser (3) of each chamber are arranged coaxially and the cylindrical conduit (2) extends from the outlet (10) of the diffuser (1) to the inlet (3;) of the confuser (3). The outlet (30) of one of the confuser (3) and the inlet (1;) of one of the diffuser (1) of adjacent chambers in the series connect the chambers together. According to the method, fluent materials are injected through the device.

Heating, ventilating and air-conditioning systems

Abstract: At an outlet of a heating, ventilating or air conditioning system air passes from the ducting through a plenum chamber, a damper provided with a set of blades which are movable between open and closed positions and a diffuser which directs the air in a desired direction. The plenum chamber is provided with internal vanes which act to guide a flow of air through the chamber between its inlet and outlet. The damper defines a plurality of predetermined blade positions between the open and closed positions and a resilient finger and teeth for retaining the blades in a selected one of said predetermined positions. The damper has a frame comprising a plurality of discrete frame elements interconnected at each corner joint of the frame by a friction fit pin passing through interdigitated projections on the frame elements. The diffuser is formed as a plurality of concentric portions which are each integrally formed with cooperating snap-fitting connections enabling the portions to be interconnected to form a complete diffuser. The blades for the damper have an integrally moulded body and a separate blade spindle received within a bore formed in the moulded body. The diffuser is mounted on a support connected to the plenum chamber by way of a fastening comprising an integrally formed head and shank which is threaded adjacent its free end, together with integrally formed resilient fingers for retaining the fastening in position on part of the diffuser whilst permitting rotation of the fastening.

The Operational Stability of a Centrifugal Compressor and its Dependence on the Characteristics of the Subcomponents

Abstract: A centrifugal compressor was tested with three different diffusers with circular-arc vanes. The vane inlet angle was varied from 15° to 30°. Detailed static wall pressure measurements show that the pressure field in the diffuser inlet is very sensitive to flow rate. The stability limit regularly occurred at the flow rate giving the maximum pressure rise for the overall stage. Mild surge arises as a dynamic instability of the compression system. The analysis of the pressure rise characteristic of each individual subcomponent (impeller, diffuser inlet, diffuser channel,…) reveals their contribution to the overall pressure rise. The diffuser channels play an inherent destabilizing role while the impeller and the diffuser inlet are typically stabilizing. The stability limit was mainly determined by a change in the characteristic of the diffuser inlet. Further, the stability limit was found to be independent of the development of inducer-tip recirculation.Copyright © 1993 by ASME

Single wafer processing in stagnation point flow CVD reactor: prospects, constraints and reactor design

Abstract: A stagnation point chemical vapor deposition (CVD) reactor that obviates substrate rotation can deposit a uniform, thin layer by developing a uniform boundary layer adjacent to the surface of deposition in an axially uniform flow. Such a geometry is highly desirable for high throughput, reproducible single wafer processing in electronic industry. It can also operate effectively at atmospheric pressure if its geometrical and operational parameters are optimized. It is shown here that the nature of the gas distributor, optimized diffuser shape inlet with respect to its angle of divergence, diffuser height and its inverted geometry are the key design parameters. The pressure drop across the gas distributor, inlet gas velocity, gas viscosity, width of hydrodynamic boundary layer on the inner walls of the diffuser that limits the available area for uniform deposition and thermal convection are its important operational parameters. The inverted reactor geometry minimizes the convection related instabilities and helps stabilize the gas flow in the reactor. Analytical expressions are developed to correlate these functional parameters of a stagnation point CVD reactor to its performance in order to develop the reactor design. Finally, the practical aspects including the experimental results of operation of such a CVD reactor design are discussed.

Particulate removal in inflatable restraint system gas generators

Abstract: An apparatus (10) for producing inflation gas for a vehicle occupant restraint includes a container (16) having a first chamber containing a pyrotechnic charge (54) and a second chamber (14) which may contain pressurised gas. The first chamber is closed by a solid metal plug (44) and a thin metal diaphragm (46) which covers an outlet nozzle (42). The second chamber has a constricting outlet orifice (32) covered by a rupturable second metal diaphragm (92) which leads to a diffuser unit with outlet apertures (94). An impingement filter (98) confronts the outlet nozzle (42) and hot gas from the first chamber impinges on the filter (98) where particulate material is deposited by condensation and entrapment. There is at least an approximately 180° cumulative change in gas direction between the gas contacting the filter (98) and the passage of inflation gas into the diffuser.

Comparison of Conventional and Low Solidity Vaned Diffusers

Abstract: Test results are presented comparing the aerodynamic performance of single stage centrifugal compressors with thin flat plate, low solidity vaned diffusers to conventional thin vaned diffusers. The test data were acquired from a low Mach number process gas compressor and a high Mach number industrial air compressor. The data are all normalized relative to baseline vaneless diffuser results. Performance parameters of stability, head rise to surge, overload flow margin, and stage efficiency are compared. The low solidity vane inlet incidence angle is shown to be an important design parameter that influences both compressor operating range and efficiency.Copyright © 1993 by ASME

Detailed Flow Measurements in a Centrifugal Compressor Vaneless Diffuser

Abstract: Hot-wire anemometer measurements have been made in the vaneless diffuser of a 1-3-dia low-speed backswept centrifugal compressor using a phase lock loop technique. Radial, tangential, and axial velocity measurements have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wake flow pattern and the blade wakes. The passage wake is located on the shroud side of the diffuser and mixes out slowly as the flow moves through the diffuser. The blade wakes, on the other hand, distort and mix out rapidly in the diffuser. Contours of turbulent kinetic energy are also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced

Multi-row rib diffuser

Abstract: A multi-row rib diffuser is provided which comprises a first row of low ribs with relatively small height extending into regions of very low flow angle and a row of high ribs located behind the leading edge of the first row of ribs. The high ribs extend further into the region of the low flow angle and accept the connected flow from the low ribs as well as additional low angle flow not corrected by the low ribs.

Foam producing venturi and method of using same

Abstract: A venturi for producing medium expansion foam for use in fire fighting applications. The new venturi contains a swirl inducer bushing near the entry of the nozzle, a two section frustum shaped diffuser, and a plurality of angularly oriented air injector openings. The venturi progressively decreases in cross-sectional area from a discharge point thereof to a throat of the nozzle. The cross-sectional design together with orientation of the air injector permits high quality lasting foam to be produced under a broad fluid supply pressure while minimizing the amount of foam reagent employed.

Detailed Flow Measurements in a Centrifugal Compressor Vaneless Diffuser

Abstract: Hot wire anemometer measurements have been made in the vaneless diffuser of a 1 metre diameter low speed backswept centrifugal compressor using a phase lock loop technique. Radial, tangential and axial velocity measurements have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wake flow pattern and the blade wakes. The passage wake is located on the shroud side of the diffuser and mixes out slowly as the flow moves through the diffuser. The blade wakes, on the other hand, distort and mix out rapidly in the diffuser. Contours of turbulent kinetic energy are also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced.Copyright © 1993 by ASME

Gas turbine exhaust diffuser.

Abstract: The present invention relates to an exhaust diffuser for a gas turbine, the diffuser being designed to be inserted downstream from a last expansion stage constituted by an outlet duct of circular cross-section containing a central bulb. The diffuser includes a flared transition duct having an inlet end of circular cross-section identical to the cross-section of the outlet duct of the last stage, an outlet end of square cross-section, and four fixed fins disposed inside the ducts close to respective corners of the square cross-section for directing the exhaust gases toward the corners of the square cross-section.

Vaned diffuser for centrifugal and mixed flow pumps

Abstract: A vaned diffuser for centrifugal and mixed flow pumps which has vanes in two rows radially displaced from each other, wherein the vanes are arranged in an optimal positional relationship to each other to improve the diffuser performance with the total pressure loss coefficient and the static pressure recovery coefficient. The vaned diffuser includes vanes arranged in a fluid flow field defined at the outer periphery of an impeller of a centrifugal or mixed flow pump. The vanes are circumferentially arranged in two rows, that is, a first row and a second row, which are equal in number of vanes and radially displaced from each other such that the respective chords of each pair of adjacent vanes in the first and second rows are approximately parallel to each other, and the trailing edges of the vanes in the first row and the leading edges of the vanes in the second row are radially spaced from each other at a distance ΔR=0.05 L to 0.4 L, where L is the chord length of the vanes in the first row.

Heat treat furnace with multi-bar high convective gas quench

Abstract: An improved cooling arrangement is disclosed for an industrial heat treat furnace. The furnace includes a closed end cylindrical heat treat chamber in which a plenum plate is suspended adjacent the rear end thereof. The plenum plate has a central underpressure opening and a fan between the rearward end of the furnace and the plate develops a wind mass which circulates into the furnace chamber and is drawn back into the fan through the plates central underpressure opening. Between the plenum plate and the furnace rearward end is positioned a first fixed fan diffuser followed by a second fixed fan diffuser. The first fan diffuser permits wind mass flow therethrough when the fan is rotated in a first direction but not in a second direction and similarly the second fan diffuser permits wind mass flow therethrough when the fan is rotated in a second direction but not in a first direction. A cooling coil arrangement is placed adjacent the second fixed fan diffuser to permit accurate control of the cooling of the work by simply cycling fan rotation direction from clockwise to counterclockwise.

An experimental study of the interaction of an unsteady shock with a turbulent boundary layer at Mach numbers of 1.3 and 1.5

Abstract: In this paper the results are given of an experimental investigation into the flow development and the surface pressures in an unsteady shock boundary layer interaction at Mach numbers of 1.3 and 1.5. The experiment is one in which a naturally grown turbulent boundary layer on the tunnel walls is disturbed by a normal shock wave spanning the test section of the tunnel. The shock wave is oscillated by a periodic pressure disturbance in the tunnel diffuser far downstream of the interaction. Both instantaneous (spatially averaged) and time averaged results for the surface pressures are presented. These results are used to study the flow development and phase changes through the interaction over a frequency range from 34 to 167 Hz. This frequency range was chosen to cover the range of parameters likely to occur in conditions corresponding to stall flutter in the compressor fans of large bypass engines.

Experimental Investigation of the Flow in Diffusers Behind an Axial Flow Compressor

Abstract: The flow fields of four diffusers situated at the rear of a one-stage axial flow compressor was experimentally investigated. Through modification of the compressor operating point a wide range of variations of the side wall boundary layers and the radial velocity distribution outside of the boundary layers at diffuser inlet could be achieved. The three dimensional flow field at both diffuser inlet and outlet is analysed. Changes of inlet blockage and radial velocity distribution and their resulting effects on pressure recovery are thoroughly presented. Compared with the results of measurements at diffusers, typically with ducted flow inlet conditions, higher values of pressure recovery are observed. Established design rules, based on investigations of diffusers with carefully developed inlet flow, are checked regarding their applicability for diffusers in turbomachine environment.Copyright © 1993 by ASME