Influence of Cooling-Gas Properties on Film-Cooling Effectiveness in Supersonic Flow

摘要

Film cooling is considered a prerequisite for the safe operation of future high-performance rocket engines. Wall-normal or inclined cooling-gas injection into a laminar boundary-layer airflow at Mach 2.6 through a single infinite spanwise slit with various cooling gases using direct numerical simulations and experiments are investigated. Among the investigated gases, helium and hydrogen perform best with respect to cooling effectiveness and skin friction decrease. An arbitrary variation of various cooling-gas parameters shows that the diffusion coefficient has virtually no influence on the cooling effectiveness, whereas low cooling-gas viscosity, low thermal conductivity, high heat capacity, low molar mass, and low density are highly beneficial. In light of this large number of parameters, an extension of the single-species cooling-effectiveness correlation to binary gas-mixture flows is challenging, if possible at all.