OPTIMIZATION STUDY OF BOUNDARY LAYER MASS INJECTION FLOW RATE BY ZONAL DIVISIONS FOR HEAT AND DRAG REDUCTION OF HIGH-SPEED VEHICLES

Boundary layer mass injection is considered to be one of the most effective strategies for solving the thermal protection problem of critical parts of hypersonic vehicles in near-space and reducing their flight drag. However, most existing studies focused on the individual effects of boundary layer mass injection on heat flux or drag, and rarely provided a comprehensive assessment of the heat and drag reduction effects that can be brought about by boundary layer mass injection. In this paper, a numerical simulation study is carried for investigating the heat and drag reduction induced by boundary layer mass injection with blunt wedge and blunt cone under high-altitude hypersonic laminar flow conditions. A multi-objective optimization method is adopted to carry out the optimized design of the mass flow rate distribution for boundary layer mass injection, which can satisfy the drag reduction performance and at the same time improve the overall thermal protection effect, thus realizing optimal integrated performance of heat and drag reduction under the circumstance of a specific coolant mass flow rate. The results show that under laminar flow conditions, boundary layer mass injection can significantly decrease the skin friction and heat flux by adjusting the velocity boundary layer and the temperature boundary layer. For the blunt wedge with an injection mass flow rate of 28.028 g/(m²·s), the design with uniform mass flow rate distribution decreases the drag by 3.60% and the peak heat flux by 12.06%, while the optimization design decreases the drag by 4.30% and the peak heat flux by 91.01%. However, for the blunt cone with a same injection mass flow rate of 28.028 g/(m²·s), the design with uniform mass flow rate distribution increases the drag by 2.60% and decreases the peak heat flux only by 8.57%, while the optimization design decreases the drag by 19.75% and the peak heat flux by 99.95%.