Numerical Analysis of Film Cooling and Mixture Ratio Bias in Oxygen-Methane Liquid Rocket Engines

The high wall heat fluxes occurring in high-pressure liquid rocket engines have to be inevitably managed by an active cooling system. The most commonly used is the regenerative cooling system, which, however, may result insufficient. In such cases, cooling capabilities can be enhanced by other active cooling means, like film cooling or mixture ratio bias of peripheral injectors. However, the additional active cooling system has a cost in terms of performance. The present parametric study provides a general cost-benefit analysis of this cooling systems in an oxygen-methane engine. The analysis is carried out with a CFD approach validated by the Authors for the purpose of heat flux estimation in rockets. For a fixed overall mixture ratio and mass flow rate, results show that diverting part of the fuel for film cooling yields a nearly direct proportionality between throat wall heat flux reduction and specific impulse reduction. A similar result is obtained with mixture ratio bias, showing that the best performance occurs when the throat wall heat flux is at maximum.