Research PaperNumerical investigation on the optimization of local transpiration cooling effectiveness

- An optimization method to improve local effectiveness is suggested.
- Step coolant allocation can improve local effectiveness of stagnation region.
- Step coolant allocation can reduce coolant demand.
- The optimization feasibility is analyzed through a non-uniform porosity strategy.

With the development of active Thermal Protection System (TPS) of hypersonic vehicles, optimizing active TPS design and reducing weight including the system and coolant loaded are the critical issues to be considered. This paper presents an optimization method of local transpiration cooling effectiveness under supersonic condition with a freestream total temperature of 2310 K, and a freestream Mach number of 4.2. The numerical investigations of transpiration cooling are conducted by performing two strategies of coolant allocation over a nose cone surface, (1) constant coolant velocity allocation; (2) step coolant velocity allocation. The aerodynamic and aerothermal performances including Mach number and pressure distributions, cooling performances and coolant demand are analyzed by the two strategies. The analysis indicates that the step strategy can effectively improve the local cooling effectiveness in the stagnation region and reduce the coolant demand. To accomplish the optimization strategy, a non-uniform porosity strategy of the nose cone is analyzed, and the coolant flow characteristics in the porous matrix at different coolant injection conditions are studied. The study indicates that the non-uniform porosity can improve the efficiency of coolant transportation, and increase coolant mass flow rate in stagnation region.