Diffuser (thermodynamics)

About: Diffuser (thermodynamics) is a research topic. Over the lifetime, 6731 publications have been published within this topic receiving 54738 citations.

The relation between losses and entry-flow conditions in short dump diffusers for combustors

Abstract: An experimental correlation is presented between the losses and the inlet flow conditions in short dump diffusers for turbojet combustors. Cascades of compressor blades upstream of the diffuser were used to make the flow field at inlet similar to that in a real jet engine. The flow field was altered in two ways — by varying the distance between the cascades and the diffuser inlet plane and by changing the blade aspect ratio. The measurements show clearly that distortions in the radial direction affect the losses to a much larger extent than non-uniformities in the circumferential direction. In consequence, the performance can be correlated to a satisfactory degree of accuracy simply by using the radial blockage factor at inlet.

Experimental and Numerical Investigation of Unforced unsteadiness in a Vaneless Radial Diffuser

Abstract: The paper reports combined experimental and numerical investigations of unforced un- steadiness in a vaneless radial diffuser. Experimental data were obtained within the diffuser using stereoscopic time resolved Particle Image Velocimetry (PIV) recording three velocity components in a plane (2D/3C), coupled with unsteady pressure transducers. To characterize the inception and the evolution of the unsteady phenomena, spectral analyses of the pressure signals were carried out both in frequency and time-frequency domains and the PIV results were post processed by an original averaging method. Two partial flow rates were investigated in detail in this paper. A single unforced unsteadiness was identified for the lowest flow rate, whereas, two competitive intermittent modes were recognized for the higher mass flow. Numerical analyses were carried out on the same pump by the commercial code CFX. All the computations were performed using the unsteady transient model and the turbulence was modelled by the Scale-Adaptive Simulation (SAS) model. Numerical pressure signals were compared with the experimental data to verify the development of the same pressure fluctua- tions.

Servo-controlled variable geometry ejector pump

Abstract: A variable geometry ejector pump is configured to receive pressurized fluid from one or more pressurized fluid sources and to control fluid pressure and temperature down stream of the pump to a variety of pressure and temperature values. The variable geometry ejector pump includes a primary inlet, a secondary inlet, a variable geometry ejector, an ejector valve, an actuator, a mixing section, a diffuser section, and an actuator control mechanism. The actuator control mechanism is adapted to receive one or more control signals, and is operable, in response to the control signals, to control the actuator, to thereby control fluid pressure and temperature down stream of the pump.

Pressure recovery in a turbocharger compressor volute

Abstract: The diffusion and pressure recovery in a centrifugal compressor stage is normally accomplished in the diffuser (vaned or vaneless) downstream of the impeller and, at the design flowrate, the volute is designed to collect the gas flow without further diffusion. It is, however, well established that at high flowrates the gas accelerates around the volute and as a consequence the pressure decreases, while at flowrates less than that at design the gas decelerates and a pressure rise occurs. There is little published material with respect to the detailed design of volutes, and the procedure is largely one of experience based on previous designs and tests. This investigation describes the performance of the volute with both a vaneless diffuser and a series of low solidity vaned diffusers upstream. It is shown that the volute provides a significant pressure rise at the best efficiency point and at flowrates down to full surge. It is shown that the volute performance is a function of inlet flow angle and that it plays a significant role in setting both the best efficiency flowrate and the operating range of the compressor.

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.