Numerical Investigation of Film Cooling in a Thruster

In this work, film cooling of a 10N thrust chamber is investigated using different numerical models. The thruster is modeled by feeding gas at a chemical equilibrium state from the inlet. Heat flux is computed for different flow rates of the coolant and is compared to the analytical Bartz equation for the no coolant case. In the second part, solid wall heat conduction is modeled, and the computed wall temperature profile is compared to the available experimental data. Chemical dissociation of MMH in the coolant layer is modeled by constructing a chemical mechanism for the reactions of Methyl Hydrazine with Nitrogen Tetroxide. Chemical reactor modeling shows a close prediction to other available data for the combustion of MMH/NTO system. To assess the effect of different cooling mechanisms in the coolant layer, different approaches for heat transfer modeling with different levels of complexity are investigated in this paper. The considered models include cold gas, reactive gas, cold droplets, and a reactive evaporating layer of droplets. For the most sophisticated model considered (reactive evaporating layer of droplets), a 48% reduction of heat flux is computed at the throat when 20% of the fuel is used as the coolant. Also, when solid wall heat conduction is considered, the computed wall temperature profile is closest to the experimental data for the case of 20% of the fuel as coolant.