Multi-objective aerodynamic optimization of an axisymmetric variable-geometry inlet with a Mach 5 design point

The inlet is a critical component of the air-breathing system of an aircraft engine and an appropriate inlet design can address the issue of aerodynamic contradiction between low and high Mach numbers, restricting aircraft flight over a wide speed range. Therefore, in this study, an axisymmetric variable-geometry inlet with a Mach 5 design point was designed. A multi-point multi-objective optimization design, based on the Kriging surrogate model and non-dominated sorting genetic algorithm-II algorithm, was performed. Wind tunnel tests and numerical simulations were conducted to investigate the inlet performance and flow field details. The steady-state pressure distribution was recorded, and shadowgraph images were obtained simultaneously to comprehensively evaluate the inlet performance. The experimental and numerical results indicate that the design and optimization methods of the inlet are effective. The inlet operated appropriately and stably over a wide range of speeds, and the total pressure recovery (TPR) coefficient reaches 0.421 at the design point. The optimization results show that a 21.36% gain in the TPR coefficient at Ma = 3.0 was achieved at the cost of a 2.44% loss of total pressure recovery at Ma = 5.0. It is also beneficial in terms of the total pressure distortion at Ma = 5.0, which is reduced by 6.54%. This indicates that the inlet design and optimization framework developed in this study is promising for wide use in practical engineering applications.