Transpiration cooling effects on nozzle heat transfer and performance

The effects of transpiration cooling on boundary-layer growth, heat transfer, and nozzle performance were investigated. A two-dimensional Mach 2.0 contoured nozzle (Re/m = 5.2 x 10(7)), with one contoured wall constructed of sintered stainless steel (2.0-mu m pore size) was tested. Blowing ratios up to 0.51% of the freestream mass how were tested using high-frequency-response heat flux and pressure instrumentation. Measurements included wall heat flux and static pressure, as well as exit pitot pressure profiles. Shadowgraph photography was: used for flow visualization. A reduction in heat transfer of up to 14% was measured for the highest blowing ratio. On the other hand, large increases in the nozzle exit boundary-layer thickness were found. However, blowing had a minimal effect on the nozzle thrust coefficient and specific impulse. In general, this study highlighted the potential beneficial and adverse effects of transpiration cooling on rocket nozzle cooling.