High-Load Liquid Rocket Engine Turbine: Design Optimization and Flow Loss Analysis

A full-flow staged combustion cycle (FFSC) liquid rocket engine can efficiently utilize the propellant energy. However, it increases the demand for turbine mass flowrate and output power. The increased loads will induce secondary flow loss. Considering the complex turbine design and flow field, few studies have investigated the design optimization and flow loss analysis of FFSC engine turbines. To develop a high-efficiency FFSC oxidizer turbine and investigate its flow loss, this study adopted the design method of the reaction turbine and introduced a radial equilibrium equation to design a preliminary FFSC oxidizer turbine. An optimization design framework was proposed, including sensitivity analysis, second-order polynomial response surface model, and genetic algorithm (GA). Large eddy simulation (LES) was employed to analyze the generation and development of the flow loss. The findings indicated that outlet flow angle had a predominant impact on turbine efficiency. The optimized turbine achieved 4.08% increase in efficiency. This improvement resulted from a reduced flow deflection angle in the rotor channel, which weakened the adverse pressure gradient. Consequently, the loss mechanism shifted from the streamwise vortex (SV) entrainment boundary layer loss observed in the preliminary turbine to a smaller passage vortex loss. Summarizing the results of the optimization design framework, design guidelines, including three design parameters were proposed, which could be applied to other high-pressure, high-flow, and high-power turbines.