Active Control of Dual-Bell Nozzle Operation Mode Transition by Film Cooling and Mixture Ratio Variation

摘要

Anumerical study is conducted to investigate the impact of a film-cooled dual-bell nozzle extension on its operationmode transition behavior. Therefore, unsteady Reynolds-averaged Navier–Stokes simulations of the transitionprocess between the sea level and altitude modes are carried out. The investigated dual-bell nozzle model is fedwith hot gas by a combustion chamber using liquid oxygen as oxidizer and gaseous hydrogen as fuel. Upstream of thedual-bell nozzle contour inflection, gaseous hydrogen is injected as cooling fluid for the nozzle extension wall.The numerical studies yield a clear impact of the cooling fluid mass flow rate on the transition nozzle pressure ratio ofthe dual-bell nozzle. The increase of the cooling fluid mass flow rate leads to a shift of the dual-bell transition nozzlepressure ratio to lower values. Furthermore, the impact of the combustion chamber mixture ratio on the dual-belloperation mode transition is investigated. A clear shift to lower transition nozzle pressure ratio values due to higherpropellant mixture ratios can be observed. A combination of the two effects is introduced for an active control of thedual-bell operation mode transition.