Experimental and Predicted Recovery Temperature Distributions in a Rocket Nozzle With Gaseous Film Cooling

The adiabatic wall temperature distribution in nozzles with gas injection through a peripheral slot at the entrance was investigated. Experimental wall temperature distributions were measured in a series of hot gas (hydrogen-air combustion as the primary source) tests with three geometrically different channels—a constant area duct, a gradually converging nozzle, and a rapidly converging nozzle. Cooling effectiveness was found to be significantly higher for the rapidly converging geometry. Prediction of recovery temperature distributions under the test conditions with available boundary layer computer programs was then investigated. Predicted results were consistently higher than measured. Significantly improved agreement between predicted and measured results was achieved by introducing effective initial temperature profiles in the injectant to account for gross mixing between the injectant gas (nitrogen) and free stream gas at the injection station.