Influence of Coolant Compound Injection Orifices on Film Cooling Effectiveness

ABSTRACT

An experimental investigation is conducted to bring out the influence of coolant injector configuration on film cooling effectiveness, film cooled length, film stability and its uniformity. A series of measurements are performed using hot air as the core gas and gaseous nitrogen as the film coolant in a cylindrical test section simulating a thrust chamber. Compound angle injection of coolant gas at two different configurations, viz., of 30°–10° and 45°–10°, simple angular injection at 30° and 45° and straight injections were evaluated in detail and results compared for different blowing ratios. The film cooling- effectiveness is found to be higher for the injector configuration with compound angle orifices and is maximum for 30°–10° injection as compared to others. The effective film cooled length is found to increase with increasing blowing ratios for a specific main-stream temperature whereas it reduces with increasing main-stream temperature. The study brings out the fact that there exists an optimum coolant injector configuration for which the effectiveness is maximum. It also further indicate that the film uniformity and stability are independent of each other.

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