Effects of Blowing Ratios on Heat Transfer to the Throat Region of a Porous-Walled Nozzle

摘要

The effects of transpiration cooling on heat transfer in the throat region of aporous-walled nozzle were investigated. The experiments were performed in the AFIT low speed shock tube fitted with a Mach 2 nozzle. A blowing region was limited to the area from 1.3 cm prior to the throat to 1.2 cm downstream of the throat. The blowing ratios from -0.0002 (suction) to 0.0117 (blowing) of the main stream flow were studied. Heat flux data were taken from both sides of the nozzle. One side was transpiration cooled by secondary air injection through a porous wall, while the other side was an impermeable surface. The transpiration cooled side results showed up to a 40% reduction in heat transfer coefficient at the blowing ratio of 0.0116. Also, with this small blowing region (from 1.3 cm upstream of the nozzle throat to 1.2 cm downstream of the nozzle throat), the results of the exit Mach number and boundary layer thickness showed good improvement compared to a larger blowing region (from 1.3 cm upstream of the throat to 8.8 cm downstream of the throat). (MM).