Showing papers on "Diffuser (thermodynamics) published in 1999"

A numerical design study of the valveless diffuser pump using a lumped-mass model

Abstract: This paper presents a lumped-mass model especially developed for valveless diffuser pumps. It is implemented using MATLAB. The model is tested for different previously reported valveless diffuser pumps and shows good agreement with the experimental results. The model predicts the flow-pressure characteristics for different excitation levels. The model makes it possible to study flows and pressures inside the pump. The simulations show that the maximum excitation level for the valveless diffuser pump is probably limited by low chamber pressure. Modified designs are tested and it is shown that a pump with two serially connected pump chambers working in anti-phase is advantageous compared with a single chamber pump for both the maximum volume flow and maximum pump pressure. The simulations also indicate that scaling down the diffuser elements from an throat cross-sectional area to a throat cross-sectional area probably increases the attainable pressure head.

Variable-air-volume diffuser, actuator assembly and method

Abstract: An adaptive control device (77) and method (102-108) for control of the operation of an actuator (72), and particularly thermally-powered actuator (72)of the type used in a variable-air-volume diffuser (71). The preferred adaptive control device is an expert system circuit which controls a heater (74) provided on a thermally-powered actuator (72) to implement an adaptive process (102-108) in which a sensed variable, such as room air temperature, is driven toward a target temperature control range. Most preferably, the process steps (106) include driving the room air temperature toward a gross (broader) temperature control range by moving a diffuser damper assembly (80) to a substantially fully open or substantially fully closed position. Thereafter, and while inside the gross temperature control range, the process steps (107, 108) include adjustments to the position of the damper assembly (80) are made only when a sensed parameter, preferably the supply air flow rate, is in a stable condition.

Full ring fuel distribution system for a gas turbine combustor

Abstract: A fuel nozzle system for use in a combustor utilized in a combustion turbine for reducing nitrogen oxides and other pollutants including an annular fuel distribution manifold separately mounted away from a diffusion nozzle, said annular manifold having a plurality of fuel emitting passages or holes disposed along the downstream side of the manifold, said manifold being mounted in a position away from the diffuser nozzle body to allow air to stream around the manifold on all sides allowing for a thorough mixture of fuel and air around the annular manifold for better premixing in the combustion chamber.

Low noise fan

Abstract: A collectorless vacuum fan for floor maintenance machines has a backplate with an inlet plate attached thereto in spaced relationship, and an impeller between the backplate and inlet plate Both the backplate and the inlet plate extend radially beyond the periphery of the impeller A shaft mounts the impeller for rotation The inlet plate has a central opening providing air to the hub of the impeller Vanes on the impeller discharge air out through a diffuser channel defined by the space between the inlet plate and the backplate outside the periphery of the impeller Attachment elements for mounting the inlet plate on the backplate leave the diffuser channel substantially unobstructed so that air is discharged about the entire periphery of the impeller The fan has increased air flow compared to a conventional fan having an integral collector housing and decreased noise compared to a fan having a 360 degree discharge and no diffuser

An experimental investigation of steam ejectors for applications in jet-pump refrigerators powered by low-grade heat:

Abstract: The jet-pump refrigerator cycle offers a low-capital-cost solution for utilizing low-grade waste heat in the production of cooling for buildings and process refrigeration. The heart of the jet-pump refrigerator is an ejector, the performance of which strongly determines the thermal efficiency of the cycle. This paper describes and evaluates the results of an experimental investigation into the operation of ejectors primarily for use in jet-pump refrigerators. The construction of a steam-steam ejector test facility and experimental method are described. Experimental results are provided concerning the effects of primary nozzle exit position within the mixing-entrainment section, primary nozzle exit and diffuser throat areas. The causes and effects of flow instability under conditions of high secondary pressure ratio are also discussed and methods of increasing the critical condenser pressure are identified and rated in order of effect.

Shock Oscillations in Diffuser Modeled by a Selective Noise Amplification

Abstract: Shock waves in supersonic flow oscillate under certain conditions. These oscillations usually have negative effects, especially for flow past transonic airfoils and in supersonic diffusers. It is therefore of practical importance to understand the origin and the consequences of these oscillations. We model and predict some physical characteristics of self-sustained shock oscillations in transonic diffuser flows. We first give the results of a quasi-one-dimensional stability analysis. The mean flow is calculated with a code solving the averaged Navier-Stokes equations. The present stability approach however is limited to the core region where the viscous effects can be neglected

Fine bubble diffuser

Abstract: A diffuser includes a substantially rigid base member having a first side and a second side, and an inlet conduit defining a central bore depending from the second side of the base member. A resilient dome member having a plurality of perforations is sealed to a peripheral edge of the first side of the base member. A coupling member, preferably in the form of a check valve, provides cooperation with a fluid source. As the diffuser is pressurized the dome member expands away from the base member and fluid is diffused by the perforations.

Inflation system and valve for use therein

Abstract: A valve for use in an inflation system wherein the valve has a spring regulated piston which regulates the flow rate through the valve into the inflatable member, such that if the flow rate gets too high, the regulating piston will divert some or all of the flow out a neutral thrust over pressure relief vent, which vents outside the inflatable member. The valve also has a secondary form of overpressure relief in the form of a neutral thrust diffuser which also dumps outside of the inflatable member. Fluid is prevented from flowing out of the neutral thrust diffuser by a burst disk, but if the fluid pressure is high enough, the burst disk will burst, and the fluid will flow out of the neutral thrust diffuser.

Apparatus for production of sub-denier spunbond nonwovens

Abstract: A unique isotropic sub-denier spunbond nonwoven product created by an apparatus comprising a unique multi-head resin metering system, a spinneret head with spinning sections, separated by a quench fluid extraction zone, a two sided, multilevel quench system, a fluid volume control infuser system which automatically guides the filaments into the filament drawing system while conserving energy by using a portion of the quench fluid as part of the drawing fluid and also minimizing turbulence at the entrance to the draw slot. The filament drawing system comprises a draw jet assembly with adjustable primary and secondary jet-nozzles and a variable width draw jet-slot. The entire draw jet assembly is moveable vertically for filament optimization. The offset, constant flow secondary jet-nozzle system provides an unexpectedly high velocity increment to the filaments by oscillating the filaments and increasing their drag resulting in remarkably low fiber denier on the order of 0.5 to 1.2. The apparatus also embodies a draw jet extension with an adjustable slot and contains two in-line or tandem which are also adjustable and maintain fiber tension and draw force through the lower end of the draw system. Drawn filaments are decelerated in an adjustable fluid volume control diffuser system which controls the amount and pressure of fluid in the diffuser and controls turbulence. The filaments enter into the fluid control system and begin to describe a downward spiraling motion results in remarkably uniform isotropic web where the machine to cross direction ratios of the bonded web physical properties such as tensile strength and elongation approach a ratio of 1:1.

Exhaust flow diffuser for a steam turbine

Abstract: An annular diffuser having its inlet located at the exit of a last row of blades of a steam turbine having initially very slowly increasing cross-sectional area with distance to accommodate the diffusion produced by the decaying wakes in the diffuser so as to prevent flow separation from diffuser walls and as a result to foster the diffusion process and to increase the efficiency of the steam turbine. The rate of increase of cross-sectional area, which is much smaller than that appropriate in diffusers having uniform incompressible flow at their inlets, allows wakes which form near the trailing edges of the last turbine blades to dissipate while avoiding flow separation. In the diffuser of this invention, whether it is one of fixed shape or one whose cross-sectional area can be changed by making use of an adjustable guide vane which surrounds at least a portion of the bearing cone, at a distance from inlet of one half of diffuser height at inlet, the cross-sectional area increase is smaller than 5.0% of the inlet cross-sectional area. This is equivalent to the corresponding two-dimensional straight-wall diffuser angle of, approximately, 2.9 degrees. For the diffuser whose cross-sectional area can be changed as required depending on its inlet flow conditions, the above limit applies for preferably most of the travel path of the adjustable guide vane but at least for the adjustable guide vane position closest to the turbine last blades. The length of the diffuser of this invention, in its preferred embodiment, measured along its mean line, is larger than or at least equal to 90% of the length of last turbine blades. The outer flow guide which defines the outer wall of the diffuser should have radius of curvature at its beginning larger than one half of the length of turbine last blades and should have a horizontal tangent there.

Air diffuser with air flow regulator

Abstract: A diffuser adapted to regulate air flow from an underfloor air distribution system A grille sits on a dust receptacle or basket-shaped housing that is supported by a mounting assembly in the floor A flow regulator or damper nests inside the housing Both the housing and the flow regulator have air slots extending through their side walls Air from the underfloor air plenum passes through these slots into the diffuser and is forced through helical slots in the grille into the room above the diffuser The air flow rate can be adjusted by rotating the flow regulator within the housing so that the slots in the flow regulator are either in or out of registry with the slots in the housing The flow regulator can be rotated by turning the grille The grille and mounting assembly have indicators that give a visual indication of the position of the flow regulator with respect to the housing, the opening of the slots, and the flow rate through the diffuser

Experimental and Three-Dimensional CFD Investigation in a Gas Turbine Exhaust System

Abstract: Both experimental and three-dimensional CFD investigations are carried out in a scale model of an industrial gas turbine exhaust system to better understand its complex flow field and to validate CFD prediction capabilities for improved design applications. The model consists of an annular diffuser passage with struts, followed by turning vanes and a rectangular plenum with side exhaust. Precise measurements of total/static pressure and flow velocity distributions at the model inlet, strut outlet and model outlet are made using aerodynamic probes and locally a Laser Doppler Velocimeter (LDV). Numerical analyses of the model internal flow field are performed utilizing a three-dimensional Navier-Stokes (N-S) calculation method with the industry standard {kappa}-{epsilon} turbulence model. Both the experiments and computations are carried out for three load conditions: full speed no load (FSNL), full speed mid load (FSML, 57% load), and full speed full load (FSFL). Based on the overall comparison between the measurements and CFD predictions, this study concludes that the applied N-S method is capable of predicting complicated gas turbine exhaust system flows for design applications.

Improved model for the design and analysis of centrifugal compressor volutes

Abstract: This paper describes a new model for the analysis of the flow in volutes of centrifugal compressors. It explicitly takes into account the vortical structure of the flow that has been observed during detailed three-dimensional flow measurements. It makes use of an impeller and diffuser response model to predict the nonuniformity of the volute inlet flow due, to the circumferential variation of the pressure at the volute inlet, and is therefore applicable also at off-design operation of the volute. Predicted total pressure loss and static pressure rise coefficients at design and off-design operation have been compared with experimental data for different volute geometries but only one test case is presented here. Good agreement in terms of losses and pressure rise is observed at most operating points and confirms the validity of the impeller and diffuser response model.

Annular flow diffusers for gas turbines

Abstract: An annular diffuser has its inlet located at the exit of a last row of blades of a gas turbine having initially very slowly increasing cross-sectional area with distance to accommodate the diffusion produced by the decaying wakes in the diffuser so as to prevent flow separation from diffuser walls and as a result to foster the diffusion process and to increase the efficiency of the gas turbine. The rate of increase of cross-sectional area, which is much smaller than that appropriate in diffusers having uniform flow at their inlets, allows wakes which form near the trailing edges of the last turbine blades to dissipate while avoiding flow separation. In the diffuser of this invention, at a distance from inlet of one half of diffuser height at inlet, the cross-sectional area increase is smaller than 6.5% of the inlet cross-sectional area. This is equivalent to the corresponding two-dimensional straight-wall diffuser angle of, approximately 3.7 degrees.

Fluid Dispensing valve including a fluid diffuser

Abstract: A fluid dispensing device includes a valve body defining a longitudinal opening therein, an inlet in flow communication with the longitudinal opening that defines an axis generally transverse to the longitudinal opening, and an outlet defined by a first end of the longitudinal opening. A sealing member is situated within the longitudinal opening, and a valve stem is linearly movable within the longitudinal opening and adapted to seat against the sealing member to control fluid flow from the inlet to the outlet. A nozzle is coupled to the valve body adjacent the outlet and defines an opening therethrough such that fluid can flow from the outlet through the nozzle. An apparatus is situated within the nozzle so as to cause fluid flowing from the outlet through the nozzle to do work.

Linear diffuser for balancing coal flow

Abstract: In a delivery pipe for pulverized coal fines from a coal mill to a combustion chamber, a device for diffusing unevenly distributed coal flow evenly across the pipe. In a first form, the invention comprises a plurality of static, lateral, linear diffuser elements comprising rows of protrusions or teeth spaced laterally across the coal flow path in the pipe, preferably in a staggered and overlapping relationship. In a second form, the diffuser elements are rotatably mounted across the coal flow path in the pipe, and may be rotated at different speeds and in different directions. The diffuser elements spaced across the coal flow path in the pipe may be supplemented by peripherally-mounted diffuser elements at the inlet of that portion of the pipe or housing to provide an angled pre-diffusion of the coal flow from the sides of the pipe toward the lateral elements extending across the interior of the pipe.

Mass flow measuring assembly having low pressure drop and fast response time

Abstract: An assembly for measuring the mass flow and flow rate of gases such as are used in semiconductor fabrication processes. The assembly includes an axial flow passage, viz., a capillary tube with a bore of about 0.050 inch diameter and a wall thickness of about 0.002 inch, having a downstream end connected to a diffuser section having an axially symmetric, diverging passage. Gas exiting the diffuser section has a low pressure drop because the gas has expanded at a low, controlled rate, converting velocity head into pressure head, and because the tube and diffuser section passage are in-line, eliminating right-angle turns. The assembly also includes two resistance thermometers, coils of iron-nickel alloy wire about 0.0004 inch in diameter, providing a differential temperature measurement with a time constant of less than 4 seconds. When incorporated into a mass flow controller admitting arsine gas from a storage container into a vacuum chamber, the assembly can maintain a flow rate of 5 sccm when the residual gas pressure in the container is as low as 5 Torr. The assembly can also be incorporated into a mass flowmeter.

The Experimental Study of Matching Between Centrifugal Compressor Impeller and Diffuser

Abstract: The centrifugal compressor for a marine use turbocharger with its design pressure ratio of 3.2 was tested with a vaneless diffuser and various vaned diffusers. Vaned diffusers were chosen to cover impeller operating range as broad as possible. The analysis of the static pressure ratio in the impeller and the diffusing system, consisting of the diffuser and scroll, showed that there were four possible combinations of characteristics of impeller pressure ratio and diffusing system pressure ratio. The flow rate, Q P , where the impeller achieved maximum static pressure ratio, was surge flow rate of the centrifugal compressor determined by the critical flow rate. In order to operate the compressor at a rate lower than Qp, the diffusing system, whose pressure recovery factor was steep negative slope near Q P , was needed. When the diffuser throat area was less than a certain value, the compressor efficiency deteriorated ; however, the compressor stage pressure ratio was almost constant. In this study, by reducing the diffuser throat area, the compressor could be operated at a flow rate less than 40 percent of its design flow rate. Analysis of the pressure ratio in the impeller and diffusing systems at design and off-design speeds showed that the irregularities in surge line occurred when the component that controlled the negative slope on the compressor stage pressure ratio changed.

Development of a diffuser/nozzle-type micropump based on magnetohydrodynamic (MHD) principle

Abstract: This paper reports a research effort to microfabricate a nozzle-diffuser type of micropumps based on the magnetohydrodynamic (MHD) principle using LIGA technologies. The micropump is driven using the Lorentz force and can be used to deliver electrically conductive fluids. The major advantage of a MHD-based micropump is that it does not contain any moving parts. It may have potential applications in medicine delivery, biological and biomedical studies. Prototypes of MHD micropumps have been fabricated and tested. Significant bubble generation was observed due to electrolysis effect. These bubbles made the flow two-phase one and resulted in flow rate reduction. To overcome bubble generation, a new generation of MHD micropumps is currently under development. This new, diffuser/nozzle type of the MHD micropumps is based on the similar design as widely used in the diffuser/nozzle pumps with diaphragm.

Underfloor air diffuser assembly

Abstract: An air diffuser assembly for use in combination with an underfloor air distribution system, where the system includes in part a cavity under a floor, having an upper surface, transmitting air under pressure to selected locations above the floor. The air diffuser assembly comprises first and second annular rings threadably engaging one another and secured respectively to above and below the floor, where the first annular ring includes an annular shoulder for receiving a grill assembly. The grill assembly is seated on the shoulder and is in communication with the space above the upper surface. The grill assembly further includes a centrally disposed, downwardly extending, vertically adjustable rod mounting a circular basket at its free end. The basket includes an array of through holes for delivering pressurized air from the underfloor cavity to the diffuser assembly, and means, such as a rod, connecting the basket to the grill assembly to prevent rotation of the basket. Finally, plural, radially extending, fixed vanes are provided and secured about the vertically adjustable rod to discharge air under pressure from the basket and defined sub-chamber to the space above the upper surface to impart a radial spin to the discharged air.

Sanitary beverage dispensing spout

Abstract: A sanitary beverage dispensing spout includes a diffuser housing, a central body integrally formed with the diffuser housing and depending therefrom and discharge ports extending through the bottom of the diffuser housing and opening downwardly about the outer peripheral surface of the central body. The diffuser housing includes a plate diffuser. The central body defines an outer periphery with alternating sets of converging segments. The sets of segments converge at different angles of convergence. Discharge nozzles dispense beverage concentrate from a central manifold extending through the central body. The discharge nozzles define capillary tubes for the retention of a charge of syrup therein between drink dispensing. The flow from the discharge nozzles converges with the converging flow of one set of segments. Flow from a second set of segments converges more rapidly. The mixed beverage concentrate and carbonated water streams continue to converge upon the converged carbonated water stream flowing centrally below the dispensing spout. The outer peripheral surface of the central body is open to atmosphere for the release of outgas carbon dioxide prior to the thorough mixing occurring below the spout assembly.

Suction jet pump having an inlet diffuser with an elliptical inflow cone

Abstract: A suction jet nozzle and a diffuser having an inflow cone with an elliptical cross-section is implemented in a suction jet pump to be used in a motor vehicle's fuel tank. The jet nozzle is configured to produce a flat propulsion jet that seals the diffuser over its entire circumference.

Navier-Stokes computations of the supersonic ejector-diffuser system with a second throat

Abstract: The supersonic ejector-diffuser system with a second throat was simulated using CFD An explicit finite volume scheme was applied to solve two-dimensional Navier-Stokes equations with standard k – e turbulence model The vacuum performance of the supersonic ejector-diffuser system was investigated by changing the ejector throat area ratio and the operating pressure ratio Two convergent-divergent nozzles with design Mach number of 211 and 341 were selected to give the supersonic operation of the ejector-diffuser system The presence of a second throat strongly affected the shock wave structure inside the mixing tube as well as the spreading of the under-expanded jet discharging from the primary nozzle There were optimum values of the operating pressure ratio and ejector throat area ratio for the vacuum performance of the system to maximize

Jet pumping device

Abstract: A jet pumping device includes an injection nozzle ( 1 ) intended for injection of a working fluid, placed in a line ( 3 ) including from upstream to downstream, a substantially cylindrical barrel ( 4 ), a convergent neck ( 5 ), a mixing channel ( 6 ) and a diffuser ( 7 ). The nozzle is placed at the end of a nozzle holder ( 9 ) on the longitudinal axis of the line, the pumped fluid circulates in an annular space ( 3 ) contained between the barrel ( 4 ) and the outside of the nozzle and of the nozzle holder, and the orifice of the nozzle has the longitudinal axis as the axis of symmetry. The device includes of one of the following combinations: a) the nozzle holder has, in its inner channel, an element ( 21; 22 ) for rotating the working fluid stream in the nozzle and a mechanism ( 12, 13, 14 ) for rotating the nozzle around the longitudinal axis, the mechanism being independent of the energy of the working fluid or of the pumped fluid, the nozzle rotating in the opposite direction to the direction of rotation of the working fluid stream; b) the nozzle holder has, on its outer surface, an element ( 24 ) for rotating the pumped fluid stream, such as blades inclined in relation to the longitudinal axis; c) the nozzle holder has, on its outer surface, an element for rotating the pumped fluid stream, such as blades inclined in relation to the longitudinal axis and, in its inner channel, an element for rotating the working fluid stream in the nozzle.

Inlet tube diffuser element for a hydraulic pump

Abstract: A hydraulic fluid pump (10), including a housing (12), a pumping apparatus (14), an inlet (16), a pressure chamber (17), an outlet (18), a bypass valve (20) and a diffuser (24) Wherein cavitation is reduced by using the diffuser (24) to supercharge fluid from the outlet (18) to increase the static pressure of the fluid entering the pumping apparatus (14) And wherein the inlet (16) and the diffuser (24) are designed to minimize the complexity, cost and packaging considerations of the hydraulic fluid pump (10)

Blower, blasting system, and blasting method for the blasting system

Abstract: PROBLEM TO BE SOLVED: To blast air to a distance by leading air from a diffuser air flow passage near the outer periphery of a fan casing to a clearance between an air passage member on a thin sheet and the other side wall provided on a surface opposed to the side wall and blasting the air from a blasting port so as to assure the direction and velocity of the blasting air. SOLUTION: A clearance allowing air to flow axially from a centrifugal diffuser air passage 9 between a semi-circular fan casing and a first air passage member 3 to a centrifugal diffuser air passage rear space 10 is formed as follows. Namely, the clearance between the casing and the first air passage member 3 is constant on the upper half side, and a clearance between the main body side wall and the first air passage member 3 is increased toward the lower half side. Thus, the blast air from a propeller fan is concentrated downward, concentrated in a specified direction without diffusing the flow of air after being left from the fan, and blasted with the air volume and air velocity maintained. Thus, a large air volume can be blasted to a distance.

Energy emission system for photolithography

Abstract: An emitted energy system is provided. The emitted energy system (10) may include a fluid (34) communicated through a nozzle (22). The fluid (34) communicated through the nozzle (22) may form a fluid plume (40). An input energy (64) may be applied to the fluid (34) in the fluid plume (40). The input energy (64) may excite the fluid (34) in the fluid plume (40) into producing an emitted energy (16). The emitted energy (16) is collected and directed by an output optics (18) to a target (20). In one embodiment, the target (20) is a photolithography system interface (68) for fabricating a semiconductor device (70). A remotely-controlled XYZ micro-positioning stage (620) facilitates alignment of the nozzle (510) and the diffuser (512) to the radiated energy beam.

Effect of Air Extraction for Cooling and/or Gasification on Combustor Flow Uniformity

Abstract: Reducing emissions is an important issue facing gas turbine manufacturers. Almost all of the previous and current research and development for reducing emissions has focused, however, on flow, heat transfer, and combustion behavior in the combustors or on the uniformity of fuel injection without placing strong emphasis on the flow uniformity entering the combustors. In response to the incomplete understanding of the combustor's inlet air flow field, experiments were conducted in a 48 percent scale, 360 deg model of the diffuser-combustor section of an industrial gas turbine. In addition, the effect of air extraction for cooling or gasification on the flow distributions at the combustors' inlets was also investigated. The following three different air extraction rates were studied: 0 percent (baseline), 5 percent (airfoil cooling), and 20 percent (for coal gasification). The flow uniformity was investigated for the following two aspects: (a) global uniformity, which compared the mass flow rates of combustors at different locations relative to the extraction port, and (b) local uniformity, which examined the circumferential flow distribution into each combustor. The results indicate that even for the baseline case with no air extraction there was an inherent local flow nonuniformity of 10 ∼ 20 percent at the inlet of each combustor due to the complex flow field in the dump diffuser and the blockage effect of the cross-flame tube. More flow was seen in the portion further away from the gas turbine center axis. The effect of 5 percent air extraction was small. Twenty percent air extraction introduced approximately 35 percent global flow asymmetry diametrically across the dump diffuser. The effect of air extraction on the combustor's local flow uniformity varied with the distances between the extraction port and each individual combustor. Longer top hats were installed with the initial intention of increasing flow mixing prior to entering the combustor. However, the results indicated that longer top hats do not improve the flow uniformity; sometimes, adverse effects can be seen. Although a specific geometry was selected for this study, the results provide sufficient generality to benefit other industrial gas turbines.