要約

This paper presents an analytical model for gaseous film cooling applicable to a convergent divergent nozzle of a rocket engine. Since the goal is to develop a simple model, suitable for design and test analysis, a one-dimensional model is considered. The boundary layer growth due to the coolant injection is accounted for by assuming an effective leading edge upstream of the true leading edge. This effective length is calculated based on the overall mass balance. The velocity profile in the boundary layer downstream of the coolant injection is assumed based on the literature available for the wall–jet case. The assumed profile accounts for the wall–jet spreading and the maximum velocity decay downstream of injection. The effect of divergence in the nozzle on the boundary layer flow has been accounted for. Appropriate correction terms are included in the model to account for the free-stream turbulence, multispecies mixing, nozzle divergence, and radiation heat transfer. The wall temperatures obtained are compared with experimental results and are found to be in good agreement. The results showed that the effect of radiation on wall temperature is significant.