Abstract
An experimental investigation on an opposing jet as a thermal protection system in high enthalpy flow has been conducted. The heat flux distributions on a hemispherical-cylindrical test model with and without the opposing jet have been measured in a free-piston shock tunnel. The test gas is air with Mach number of 7.5 or 7.9 with total enthalpy of 20 MJ/kg or 4.8 MJ/kg, respectively. Nitrogen as a coolant gas is injected directly against the test flow through a sonic nozzle at the nose tip of the test model. The effect of alleviating heat loads is investigated by changing total pressure of the opposing jet. A significant reduction of surface heat loads is observed in the case of relatively strong opposing jet under both test flow conditions. The result indicates that thermal protection with the opposing jet is effective in high enthalpy flow. In addition, parameters to characterize the cooling effect of the opposing jet are discussed.
