Recovery Temperature Measurement of Underexpanded Sonic Jets Impinging on a Flat Plate

摘要

An experimental investigation has been carried out to examine heat-transfer characteristics of an axisymmetric, underexpanded, sonic jet impinging on a flat plate. The ratio of nozzle-exit pressure to the ambient pressure, that is, underexpansion ratio ranges from 1.5 to 3.5, and the distance from the nozzle exit to the plate is adjusted from 0.5 to 20.0 nozzle-exit diameters. Detailed measurements of the recovery factor and the surface pressure on the flat plate have been achieved. The results showed that the recovery factor obtained in the present study have distributions that are different from those for low-velocity jets. It has been found that the recovery factor at the stagnation point varies from 0.35 up to over 1.25 for the highest underexpansion ratio of P_e/P_a = 3.5 within the present experimental range.