Film Cooling of a Blunt Body in Supersonic High Enthalpy Flows

摘要

During atmospheric re-entry at hypersonic speed or at very high speedflight in the atmosphere, vehicles experience extremely high thermal loadsfor relatively long times: the classical thermal protection materials do notsurvive and need to be replaced by lightweight actively cooled components.This work investigates experimentally film cooling of a blunt body in asupersonic high enthalpy flow. The coolant injected from the center of theblunt body surface against the free stream, generates a thin, cool,insulating layer, yielding a thickening of the boundary layer, thus reducingthe temperature gradient and the resulting heat flux to the surface.Experiments were performed in the Aerothermodynamics Laboratory inthe Technion, where a 5-MW arc plasma tunnel enables simulation of highenthalpy flows. Two models (with and without injection) were exposed to aMach 2.2 freestream with a total enthalpy of 1.7 MJ/kg. Nitrogen andhelium were used as coolants gases. A parametric study shows theinfluence of coolant physical properties and mass flow rate on thecharacteristics of the flow surrounding the model and on the resultingtemperature reduction at different locations on the test model.