Effect of Gaseous Coolant Temperature on the Transpiration Cooling for Porous Wall in the Supersonic Flow

The problems of the transpiration cooling for porous wall in the supersonic flow is considered. The experimental results are presented for the porous wall temperature distribution along the mainstream, the Mach number of the stream was 2, and the total temperature was +20 degrees C. The temperature of the air injected through the porous surface is varied in a wide range from -12 degrees C to +77 degrees C. It is established that depending on the temperature of injected gas several characteristic regimes can be distinguished. If the temperature of injected gas is less than a certain value then the temperature of the porous wall decreases along the flow. On the other hand, if the injected gas temperature is higher than a certain value, then the temperature of the porous wall increases downstream. In the intermediate range of temperatures of injected gas, the temperature profile along the flow has a minimum. The minimal temperature of the wall can be lower than the temperature of injected gas. The criteria for realization of different types of temperature profiles on the permeable porous surface in a high-speed gas flow are obtained on the base of simple phenomenological model. (C) 2019 Elsevier Ltd. All rights reserved.