Showing papers on "Diffuser (thermodynamics) published in 1977"

Influence of Inlet Flow Conditions and Geometries of Centrifugal Vaneless Diffusers on Critical Flow Angle for Reverse Flow

Abstract: The authors’ preceding analysis on centrifugal vaneless diffusers is used to examine the influences of diffuser geometries and of flow inlet conditions on the critical flow angle for reverse flow, and the results are presented in graphs. The diffuser width to radius ratio, the inlet Mach number, and the distortion of the inlet velocity distribution have significant influences on the critical flow angle, while the Reynolds number and the boundary layer thickness at the inlet have minor influences.

Gas turbine engine having bleed apparatus with dynamic pressure recovery

Abstract: A gas turbine engine has conduits leading from the compressor to the turbine for bleeding a portion of compressor air through the turbine blades for cooling or other purposes. A radial pump in the conduits formed by a tangential accelerator and a rotating diffuser transmits the air from the non-rotating environment in the engine to the rotating environment of the turbine rotor. The tangential accelerator accelerates the bleed air to a tangential speed higher than that of the rotor, and the radial diffuser is designed to recover the dynamic pressure or relative velocity of the air over the rotor.

Performance of Annular Combustor-Dump Diffusers

Abstract: In this paper results of an experimental investiga- tion of the performance of an annular combustor-dump diffuser are presented. The geometry comprised a straight -walled pre -diffuser followed by a sudden expan - sion in which the flow divides and passes to the two con - centric annuli surrounding the flame tube. Tests were carried out to investigate the influence of: pre -diffuser geometry, the distance between pre -diffuser outlet and the head of the flame tube and, the division of flow between the two concentric annuli. The system is shown to offer good performance and flow stability over a wide range of operating conditions. The way in which the presence of the flame tube improves the performance and stability of flow in the pre-diffuser is demonstrated. Whereas nearly all of the pressure rise occurs in the pre-diffuser most of the total pressure loss occurs near the head of the flame tube. Minimum total pressure loss and a symmetrical pressure distribution on the head of the flame tube was obtained with a symmetrical velocity profile at pre-diffuser outlet. The results also focus attention on the need to carefully match the geometries of the pre -diffuser, flame tube and surrounding annuli. Nomenclature

Compact shrouds for wind turbines

Abstract: As part of a large project aimed at finding the optimal configuration for an aerogenerator to exploit wind power, an investigation was launched to find the most compact shroud possible. The dominant contributor to the shroud length is the structure downstream of the turbine (the diffuser). This component has an ever increasing cross-section as one progresses downstream, however, fast rate of area divergence will cause flow separation and the significant reduction in output power associated with it. It is the purpose of the present paper to demonstrate ways to overcome this difficulty. This can be achieved either by proper diversion and introduction of the shroud's external flow into the diffuser's inner boundary layer or alternatively, by the usage of a ring-flap.

Process for the thermal cracking of hydrocarbons

Abstract: In a process for the thermal cracking of hydrocarbons by the introduction of liquid petroleum feedstock in atomized form into a stream of hot combustion products formed by the combustion of fuel and oxidant in successive burner and mixing zone, constricting throat zone, a velocity acceleration diffuser zone and secondary cracking and reaction zone along the path of hot combustion product stream flow, an improvement is disclosed which comprises: effecting initial mixing, vaporization and cracking of said atomized liquid petroleum feedstock in said stream of hot combustion products in said burner and mixing zone maintained at subsonic velocity flow; effecting substantially complete mixing and vaporization in said constricting throat zone wherein said stream is maintained, at exit, at sonic velocity flow; passing said stream through a velocity acceleration diffuser zone maintained at supersonic velocity flow; passing said stream through a shock region produced by cross-sectional expansion of a diffuser zone; and effecting a final thermal cracking conversion in said stream in a subsonic velocity additional cracking reaction zone before quenching of said stream.

Spring powered, portable, hand held suction and blower apparatus

Abstract: A portable, hand held, air suction and blower unit comprising an air inlet assembly with sequentially arranged nozzle, flexible inlet tube, and diffuser, all detachably connected to the front end of the unit body. The diffuser cooperates with the front end of the body to form a bayonet type joint therebetween. An air inlet passage extends rearwardly from the front end of the body to the tangential fan which is journaled at the rear of the body. The fan is powered by a manually wound flat spiral spring, which spring drives the fan through a gear train. An air outlet passage extends forwardly from the fan to an outlet opening also located at the front of the unit body. A removable, pervious receptacle, with an open forward end, is located in the front portion of the air inlet passage and serves to collect particles or objects which are drawn into the body by the flowing air. Furthermore, a flap valve, which is located in the diffuser, allows the particles or objects to pass by and enter into the receptacle when air is being drawn into the body by the fan. The flaps of the valve, however, relax to close off the receptacle from the nozzle when the fan is not operating.

Dispersion of Buoyant Waste Water Discharged from Outfall Diffusers of Finite Length

Abstract: The three-dimensional flow field created by a simple line plume of finite length in a steady current of uniform density was investigated in a laboratory basin. The results can be used to aid in the prediction of dispersion of buoyant waste water released from line diffusers, particularly sewage discharges into the ocean. The experimental results for minimum surface dilution, S_m, were found to be independent of L/H, in the range 3.7 < L/H < 30 where L is the diffuser length and H the water depth, and independent of Reynolds number, Re = 4uH/ν, in the range 1190 < Re < 12,900 where u is the current velocity. The results are expressed graphically in the form: (S_(m)q)/uH = f(F,θ), where q is the volume flux per unit length, and θ the orientation of the line diffuser to the current. F is a type of Froude number defined by F = u^(3)/b, where b is the buoyancy flux per unit length. The initial momentum flux is assumed to be small. For a current perpendicular to the diffuser, and F > 0.2, the effluent mixes over the receiving water depth due to self-induced turbulence. When the diffuser is of finite length, the diluted effluent separates from the bottom at some point downstream and forms a two-layer flow. However, currents parallel to the diffuser do not produce mixing over the depth, and the flow forms a two-layer system immediately, even for Froude numbers as high as 100. For F 0.1, dilutions when the current is perpendicular to the diffuser are proportional to the current speed. For 0.1 0.1, a diffuser placed perpendicular to the current will result in greater dilutions than if parallel. The ratio of minimum surface dilution when the current is perpendicular to that when the current is parallel increases with F, and is equal to about 4 at F = 100. Horizontal spreading of the waste field is governed by buoyancy forces rather than ambient turbulence. For F ≥ 1 the initial surface plume spreading is found to be linear, and independent of L/H and Re for 3.7 < L/H < 15, and 2,900 < Re < 13,000. Beyond this initial linear spreading zone the rate of plume growth decreases. It is speculated that regimes may exist where the surface width grows as the 2/3 or 1/5 power of downstream distance; the results are not adequate to confirm these growth laws. It is believed that ambient turbulence has no significant effect on diluting the waste within several diffuser lengths from the source. The results have been presented in a manner which makes them immediately applicable for improving outfall designs, and demonstrates the error frequently made in assuming two-dimensional flow fields. This assumption is incorrect even if the diffuser length is an order of magnitude greater than the water depth.

Guide tube flow diffuser

Abstract: Nuclear reactor upper internal guide tube having a flow diffuser integral with its bottom end. The guide tube provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide tube thereby limiting the amount of coolant flow and turbulence within the guide tube, thus enhancing the ease of movement of the control rods.

Experimental performance of a 13.65-centimeter-tip-diameter tandem-bladed sweptback centrifugal compressor designed for a pressure ratio of 6

Abstract: A 13.65 cm tip diameter backswept centrifugal impeller having a tandem inducer and a design mass flow rate of 0.907 kg/sec was experimentally investigated to establish stage and impeller characteristics. Tests were conducted with both a cascade diffuser and a vaneless diffuser. A pressure ratio of 5.9 was obtained near surge for the smallest clearance tested. Flow range at design speed was 6.3 percent for the smallest clearance test. Impeller exit to shroud axial clearance at design speed was varied to determine the effect on stage and impeller performance.

Experimental performance of a 16.10-centimeter-tip-diameter sweptback centrifugal compressor designed for a 6:1 pressure ratio

Abstract: A backswept impeller with design mass flow rate of 1.033 kg/sec was tested with both a vaned diffuser and a vaneless diffuser to establish stage and impeller characteristics. Design stage pressure ratio of 5.9:1 was attained at a flow slightly lower than the design value. Flow range at design speed was 6 percent of choking flow. Impeller axial tip clearance at design speed was varied to determine effect on stage and impeller performance.

Attic exhaust system

Abstract: An attic evacuation system having a solar energy transfer section supported on a roof with a spacer between the energy transfer section and the roof. Air from the attic passes through the energy transfer section through two flow channels. A turbine is provided in one of the flow channels and drives a compressor which supplies compressed air to the other flow channel. A plurality of energy absorbing blades are provided in the flow channel having the compressed air. A transparent window is provided in the energy transfer section adjacent the energy absorbing blades. A diffuser nozzle is provided at the end of the flow channel without the energy absorbing blades. The flow channel containing the energy absorbing blades has an ejector nozzle at the exit end thereof. The ejector nozzle flow is directed into the diffuser nozzle to entrain air to draw air through the turbine to drive the compressor.

The Effect of Rotor Blade Wakes on Centrifugal Compressor Diffuser Performance—A Comparative Experiment

Abstract: A vortex nozzle facility for testing radial vaned diffusers independently of any rotor has been developed [1, 2]. This paper describes a comparative experiment designed to evaluate the applicability of results obtained on this facility to actual rotating compressors. Geometrically scaled diffusers were tested in the vortex nozzle facility and in an actual rotating compressor rig, and the results are compared and shown to be very similar in terms of both performance and stability limits. The implications of these results are that blade wake mixing and unsteadiness do not significantly affect diffuser performance.

Method for exciting a gas dynamic CO2 laser and apparatus for performing the method

Abstract: The present method relates to exciting a gas dynamic CO2 laser, especially at high stagnation temperatures above 2500° K and at a combustion chamber pressure above 50 bar. A liquid fuel and a liquid oxidizer are injected into the combustion chamber at these operating parameters and the produced laser gas is caused to flow through a Laval nozzle into a resonator. The flow cross sectional area of the Laval nozzle adjacent to the resonator is at least 100 times larger than the flow cross sectional area adjacent to the nozzle neck facing the combustion chamber. The flow of the laser gas through this nozzle cools the gas to about 300° K, whereby an inversion state is produced. The laser for performing this type of operation has a combustion chamber connected through the above mentioned nozzle to a resonator which in turn is connected to a diffuser. A tank for liquid fuel and a tank for a liquid oxidizer are connected to the respective injection nozzles of the combustion chamber, whereby the respective conduits preferably extend through cooling jackets of the combustion chamber of the diffuser.

Use of Experimental Separation Limits in the Theoretical Design of V/STOL Inlets

Abstract: Experimental data from several model inlets have been used to generate two parameters which are related to the limit of operation for inlet flow separation. One parameter, called the diffusion ratio, is the ratio of the peak velocity on the inlet surface to the velocity at the diffuser exit and is related to the boundary-layer separation at low throat Mach numbers. The other parameter, the peak Mach number on the inlet surface, is related to the separation at high throat Mach numbers. These parameters are easily calculated from potential flow solutions and thus can be used as a design tool in screening proposed inlet geometries. Any of the geometric design variables can be analyzed by this technique; but, this paper is restricted to the consideration of the internal lip contraction ratio. An illustrative example of an application to an inlet design study for a tilt nacelle VTOL airplane is presented. The study will show what value of contraction ratio is required to meet the operating requirements yet allow the inlet to remain free of separation as indicated by the two separation parameters.

Pressure recovery in chemical lasers

Abstract: A one-dimensiona l flow model of the chemical laser, from combustor to subsonic diffuser, is developed for the study of laser pressure recovery. Combustor and flow chemistry effects, nozzle and cavity boundary-layer losses, laser cavity combustion, and nozzle, cavity, and diffuser geometry influences are included in the analysis. The results from experimental tests on a laser nozzle array with a constant area diffuser are presented. Diffuser exit pressures as high as 263 Torr were measured during these experiments. The one-dimensional flow model is shown to be in agreement with the measured diffuser exit pressures over the full range of test conditions.

Liquid cooled pump motor unit

Abstract: A pump motor assembly comprising a stator with windings, a rotor shaft mounting a rotor in said stator, a diffuser housing arranged adjacent said stator and enclosing at least partly the stator windings, means defining a flow channel in said diffuser housing for circulation of a medium from an inlet to an outlet in said diffuser housing, and disposed in said flow channel for circulating the cooling medium therethrough over the stator windings to cool the same.

Means for improving the performance of burner shroud diffusers

Abstract: The performance of the diffuser action of burner shrouds is improved by establishing a substantially uniform velocity profile across the shroud passage by introducing a strong secondary flow in the form of vortices that lead to a better velocity profile and much improved diffuser action in the shroud passages.

Subsonic MHD-diffuser performance with high blockage

Abstract: Diffuser performance with high blockages is analyzed by a two-dimensional turbulent-flow model. This model is used to analyze the performance of simple two-dimensional, plane-walled diffusers and also of threedimensional diffusers up to and beyond the blockage limits for which previous analytical or experimental data are available. The effects of important design parameters on diffuser performance are investigated. The parameters considered are the blockage, divergence angle, Mach number, aspect ratio, and wall-to-freest ream temperature ratio. The first two parameters affect the diffuser performance significantly; the other parameters influence the performance only slightly. Results obtained from the subject model agree reasonably well with the available experimental data. The diffuser design of the U-25 facility is analyzed and the analysis predicts a pressure recovery of 0.49, which agrees very well with the measured experimental value of approximately 0.48, obtained from a small-scale model. Nomenclature = geometric cross-sectional area of diffuser, A = H> W = effective flow cross-sectional area of diffuser, Aeft=(H-2dH*)(W-2dw*) = aspect ratio , ^ = HI W - diffuser blockage parameter, B s- J — (Acff/A) = static pressure recovery coefficient, Cp - (Pexit ~ Anlet V(Po ~ P ) inlet >

Low viscosity heating oil burner - has oil pre-heater upstream of diffuser nozzle with oil flow path in spiral round heating element

Abstract: The pressure-diffuser type oil burner, handles low-viscosity heating oil below the cooking and cracking temp. It has a heater upstream of the diffuser nozzle, preheating the oil to up to 150 deg., and typically immediately before the nozzle. The nozzle union, oil pipe and heater element can be connected together in a manner such as to give good heat conductivity. The element may be cylindrical, encased by the oil feed pipe or passage and formed with the nozzle union, in a block of material with high heat conductivity, the element screwing into the block. The oil passage way run in a spiral round the element.

Static air pressure diffuser

Abstract: The present invention relates to a static air pressure diffuser that is adapted to be secured to an external probe extending from a structure for use in sensing and measuring static air pressure about the diffuser. Structurally, the static air pressure diffuser of the present invention comprises two generally circular flat plates secured together in spaced apart relationship with the lower plate being provided with a generally centrally located opening formed therein that is communicatively connected with the external probe when the static air pressure diffuser is properly mounted atop the probe. Between the two plates is defined an open area that is radially open to air currents from all directions therearound and which acts to channel air horizontally through the open space between the plates such that a true static air pressure reading may be taken about the opening formed in the lower plate between the two plates and wherein dynamic air pressure factors are minimized due to the horizontal flow of air currents perpendicular to the opening within the lower plate.

Numerical Analysis of Turbulent Separated Subsonic Diffuser Flows

Abstract: : A general finite difference formulation of the incompressible Navier- Stokes equations in terms of the vorticity and the stream function is presented for turbulent internal flows. Turbulent models such as algebraic eddy viscosity models, and the low Reynolds number two-equation k-epsilon models were systematically studied. Numerical solutions are presented for both separated and non-separated subsonic diffuser flows with either a sublayer coordinate stretching or a low of the wall matching procedure. Excellent agreement with experimental data is obtained for the fully developed channel flow. Agreement with data from an 8-deg conical diffuser is also good. The detailed flow-field structure for separated diffuser flows can be obtained including the prediction of the separation point.

Sawtoothed diffuser, vaned, for centrifugal compressors

Abstract: This invention is proposed as an aerodynamically more efficient vaned diffuser for centrifugal compressors than heretofore achieved, while still respecting the usual diffuser requirement of a limited overall diameter. The invention is so to shape the early entering portion of the diffuser side-walls and the vanes as to achieve for the first time, isobars across the so-called throat which are highly oblique to the flow direction there, instead of heretofore always an isobar which is very nearly normal or normal across the passage at that throat. This is more understandably but still briefly explained in the two sections following, on Background, and Summary, of the Invention.

Numerical Computation of Subsonic Conical Diffuser Flows with Nonuniform Turbulent Inlet Conditions

Abstract: : Numerical solutions of the Navier-Stokes equations are obtained and results presented for conical diffuser flows with turbulent nonuniform inlet conditions. The turbulent flow field is described by a two-equation, low- Reynolds-number k-epsilon model with a new turbulence model for axisymmetric flow. Fast convergence is achieved with an improved initial flow-field guess and a multiple grid Gauss-Seidel iteration method. Comparisons are made with existing data for several diffuser divergence angles with and without flow separation. Good agreement was obtained between theory and experiment.

Vorbix augmenter configuration with diffuser and vorbix swirler

Abstract: An augmenter construction for fan engines in which the fan air and the engine gas are distributed through transition ducts terminating in vortex generators and the fuel rich pilot gas discharges around these vortex generators to mix with the vortices for improved combustion. The transition tubes have diffuser sections extending from the vortex generators and these sections have rectangular or multisided terminal ends.

Combined radial diffuser and control valve for high-pressure fans

Abstract: A variable flow diffuser for use in air cushion vehicles to convert the ktic energy of the moving air from the main fan into potential energy of air pressure. The conversion is accomplished by passing the air flow from the fan through a flow splitter and diverting it radially outward in all directions along a plane perpendicular to the initial direction of the air flow. The volume of air passing through the diffuser is controlled by placing control vanes around the flow splitter or by moving the flow splitter and a back plate in and out of the air channel.

Potential application of radial splitter diffuser to shrouded wind turbines

Abstract: The application of a new concept of efficient wide-angle conical diffuser utilizing radial splitters is proposed. With this diffuser concept a significant pressure recovery has been demonstrated with expansion angle as high as 40 degrees together with good exit flow uniformity. Competitive aerodynamic performance will be shown possible with the proposed shroud, with potential for improved cost-effectiveness over the current shroud designs.

Aeration of water using flow energy - in appts. having double venturi with air entrainment into centre of first

Abstract: Device for self-acting artificial aeration of flowing water consists of >=2 venturi tubes mounted axially concentric to each other. These are so arranged that the diffuser end of the first discharge into the throat of the second. There is an air inlet line mounted in the throat of the first venturi to introduce air into the water stream. The venturi tubes have aerofoil section. The angle of opening of the first diffusor 10 degrees. The angle of opening of the second is greater than that of the first. The profile of the venturi tubes is inclined to the axis flow, the inclination of the second being greater than the first. The nozzle of the second tube is so arranged that the flow velocity of the water flowing through it is greater than that of water leaving the first venturi.

Counterbalanced throttle for I.C. engine

Abstract: The throttle for the air inlet passage of an automobile internal combustion engine comprises a variable restriction diffuser within the passage and designed for sonic velocity gas flow through its region of maximum restriction throughout substantially the entire operating range of the engine. The diffuser comprises an orifice member and a closure member movable axially in opposite direction within the passage to vary the aforesaid maximum restriction and operatively coupled with the throttle control linkage for such movement, whereby the force required to move either diffuser member against the force of the fuel and air inlet flow within the passage is counterbalanced by an oppositely directed force exerted by said flow on the other diffuser member.

Unified inlet/diffuser design by an inverse method

Abstract: The equations governing the two-dimensional, steady, inviscid flow of an incompressible fluid have been formulated in an inverse manner to obtain the resultant shape of semi-flush inlet/curved diffusers when the surface velocity distribution is specified. The results of calculations illustrating the effect of each of seven principal design variables on a nominal inlet configuration are presented. One of the configurations obtained was chosen for experimental testing to compare the onand off-design performance of inlets generated by this procedure with that of inlets obtained by more conventional methods. General results and applications of this method are discussed.