Diffuser (thermodynamics)

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

Simulations of turbulent flow in a plane asymmetric diffuser

Abstract: Large-eddy simulations (LES) of a planar, asymmetric diffuser flow have been performed. The diverging angle of the inclined wall of the diffuser is chosen as 8.5°, a case for which recent experimental data are available. Reasonable agreement between the LES and the experiments is obtained. The numerical method is further validated for diffuser flow with the diffuser wall inclined at a diverging angle of 10°, which has served as a test case for a number of experimental as well as numerical studies in the literature (LES, RANS). For the present results, the subgrid-scale stresses have been closed using the dynamic Smagorinsky model. A resolution study has been performed, highlighting the disparity of the relevant temporal and spatial scales and thus the sensitivity of the simulation results to the specific numerical grids used. The effect of different Reynolds numbers of the inflowing, fully turbulent channel flow has been studied, in particular, Re b = 4,500, Re b = 9,000 and Re b = 20,000 with Re b being the Reynolds number based on the bulk velocity and channel half width. The results consistently show that by increasing the Reynolds number a clear trend towards a larger separated region is evident; at least for the studied, comparably low Reynolds-number regime. It is further shown that the small separated region occurring at the diffuser throat shows the opposite behaviour as the main separation region, i.e. the flow is separating less with higher Re b . Moreover, the influence of the Reynolds number on the internal layer occurring at the non-inclined wall described in a recent study has also been assessed. It can be concluded that this region close to the upper, straight wall, is more distinct for larger Re b . Additionally, the influence of temporal correlations arising from the commonly used periodic turbulent channel flow as inflow condition (similar to a precursor simulation) for the diffuser is assessed.

Effects of Angle of Attack on Inlet Buzz

Abstract: Anaxisymmetric supersonic inlet was tested to study the influence of angle of attack andmass flow rate on the inlet buzz phenomenon at a freestreamMach number of 2 and at various angles of attack 0–10 deg. For each angle of attack, two main frequencies for the buzz were seen in the data. For the moderate mass flow rates, small-amplitude and high-frequency oscillation occurred. In this operation stage, both highand low-frequency oscillations exist, but the higher one is dominant and is very close to the frequency of the second acoustic resonance mode. At lower mass flow, however, low-frequency and large-amplitude oscillation occurred that had a single frequency with a constant period. Increasing the angle of attack decreased the inlet performance and limited the stability margin. At intermediate values of themass flow, the buzz frequencywas seen to be independent of the angle of attack, but, for the lower mass flow rates and at high angles of attack, the frequency of the buzz at front portions of the inlet varied. However, the diffuser end still has a constant frequency. In addition, the total-pressure signal had behavior similar to that of the static data with approximately the same frequency.

Upright fire protection nozzle

Abstract: An upright-type fire protection water spray mist nozzle has a base defining an orifice through which fire-retardant fluid can flow, an inlet section having an upstream end and defining a conduit for flow of fire-retardant fluid along a orifice axis and leading to an upstream end of the orifice, with a diffuser element defining an impingement surface that is at least substantially imperforate in an axial direction and positioned for impingement by a stream of fire-retardant fluid flowing from the orifice in a stream direction along the orifice axis, the diffuser element being positioned generally above a horizontal plane through a downstream end of the orifice.

Centrifugal compressor boundary layer control

Abstract: A centrifugal compressor is shown with an inlet directing a fluid thereto and a diffuser into which the compressor directs its output. A group or array of circumferential grooves are located in the surface of a stationary shroud which covers the blades of the compressor.

Improved Calculation of High Speed Inlet Flows. Part II: Results

Abstract: An improved numerical algorithm that solves the full mean compressible Navier-Stokes equations has been applied to the calculation of the flowfield in three separate configurations of a simulated high speed aircraft inlet. The inlet geometry consists of a converging supersonic diffuser, formed by two nonparallel plates, followed by a constant height "throat." For all cases, the freestream Mach number is 3.51, and the Reynolds number is 13.6 X10 based on the inlet length. The three configurations are characterized by different values of the angle of the converging supersonic diffuser and different boundary-layer bleed schedules. The computed results are compared with detailed experimental data for the ramp and cowl surface pressure distribution, and the boundary-layer pitot profiles at seven different streamwise locations. The agreement with the experimental results is generally good, although the experimental data display evidence of three dimensionality over a portion of the inlet flowfield.