Diffuser (thermodynamics)

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

Methodology for the Design of Streamline-Traced External-Compression Supersonic Inlets

Abstract: A design methodology based on streamline-tracing is discussed for the design of external-compression, supersonic inlets for flight below Mach 2.0. The methodology establishes a supersonic compression surface and capture cross-section by tracing streamlines through an axisymmetric Busemann flowfield. The compression system of shock and Mach waves is altered through modifications to the leading edge and shoulder of the compression surface. An external terminal shock is established to create subsonic flow which is diffused in the subsonic diffuser. The design methodology was implemented into the SUPIN inlet design tool. SUPIN uses specified design factors to design the inlets and computes the inlet performance, which includes the flow rates, total pressure recovery, and wave drag. A design study was conducted using SUPIN and the Wind-US computational fluid dynamics code to design and analyze the properties of two streamline-traced, external-compression (STEX) supersonic inlets for Mach 1.6 freestream conditions. The STEX inlets were compared to axisymmetric pitot, two-dimensional, and axisymmetric spike inlets. The STEX inlets had slightly lower total pressure recovery and higher levels of total pressure distortion than the axisymmetric spike inlet. The cowl wave drag coefficients of the STEX inlets were 20% of those for the axisymmetric spike inlet. The STEX inlets had external sound pressures that were 37% of those of the axisymmetric spike inlet, which may result in lower adverse sonic boom characteristics. The flexibility of the shape of the capture cross-section may result in benefits for the integration of STEX inlets with aircraft.

Flow Analysis in a Pump Diffuser—Part 2: Validation and Limitations of CFD for Diffuser Flows

Abstract: This paper describes an investigation into the use of CFD for highly loaded pump diffuser flows. A reliable commercial Navier-Stokes code with the standard k-e turbulence model was used for this work. Calculations of a simple planar two-dimensional diffuser demonstrate the ability of the k-e model to predict the measured effects of blockage and area ratio on the diffuser static pressure recovery at low loading levels. At high loading levels with flow separation the k-e model underestimates the blockage caused by the recirculation in the flow separation region and overestimates the pressure recovery in the diffuser. Three steady-state calculations of a highly loaded vaned diffuser of a medium specific speed pump have been carried out using different inlet boundary conditions to represent the pump outlet flow. These are compared to LDA measurement data of the flow field and demonstrate that although the Navier-Stokes code with the standard k-e turbulence model is able to predict the presence of separation in the flow, it is not yet able to accurately predict the static pressure rise of this highly loaded pump diffuser beyond the flow separation point.

Submerged nozzle for the continuous casting of thin slabs

Abstract: A dip pipe (1) which feeds by gravity with a molten metal or alloy (2) from a ladle (3) a slab (4) being formed in a thin mould (5) with cooling walls comprises a length of vertical pipe (6) communicating with the upper ladle (3) and downwards ending into a diffuser (8) of flattened shape having two discharge holes (9, 9'). According to the invention the diffuser (8) has a central partition baffle (14) designed to define two channels (16, 16') for the flow and corresponding to said two discharge holes (9, 9'), and the cross section area (10) of the flow at the highest level of the diffuser is less than the cross section area (11) of the pipe (6). Furthermore the inner side walls (12, 12') of the diffuser, which are directed to the narrow sides of the thin mould, form each an angle α ≤ 7.5° with the vertical axis (13) while departing therefrom in the downward direction, the flow partition baffle (14) narrowing in its lower portion to form two angles β ≤ 7.5° with vertical axis (13).

Internal Flow Investigation of a Centrifugal Pump at the Design Point

Abstract: The unsteadiness of the flow at the leading edge of a vaned diffuser represents a source of low efficiency and instability in a centrifugal pump. Furthermore, the internal flow of the impeller can be affected by asymmetric downstream conditions, which results in extra flow unsteadiness and instabilities. The improvement of machine performances can only be achieved if there is a progress in the comprehension of the nature of the complex flow that develops at the gap between the rotor and the stator. This paper presents the results of LDA investigation of the internal flow of a centrifugal pump equipped with a backswept impeller and a vaned diffuser. The data taken in phase with the impeller rotation are presented as animated frames reconstituting a temporal evolution of the flow in radial planes at the diffuser inlet.

Restrictor valve flow passage pop-up wear indicator

Abstract: In a fluid restrictor valve interposed in a high pressure fluid flow line having a fluid passageway disposed downstream from throttling discs and having a sleeve-like turbulence diffuser nested by the wall forming the fluid outlet passageway, a turbulence diffuser worn out indicator is disposed within a valve wall bore communicating with the periphery of the turbulence diffuser. The indicator includes a piston and rod longitudinally slidable in bores formed in the indicator body. Fluid under pressure against the piston forces the piston rod laterally outward with respect to the wall of the valve for visually indicating a worn out fluid turbulence diffuser.