Multi-objective optimization design of shock-focusing detonation initiator

Shock-focusing induced detonation is an efficient technique that has the potential to simplify detonation-based engines. However, the generation of high energy regions relies on an extremely strong shock, and the design of the initiator plays a crucial role in minimizing the threshold of incident shock strength. In this study, a multi-objective optimization design of the shock-focusing initiator was conducted using Computational Fluid Dynamics (CFD). Firstly, the accuracy of the numerical method and the reliability of the optimization platform were validated through a series of experimental data. Subsequently, the Axial Ratio (AR) of the elliptical reflector and the angle of the incident shock were optimized, considering the objectives of focusing pressure and focusing delay time. Three typical focusing patterns were identified from the samples, with pattern C generally exhibiting higher focusing pressure but longer focusing delay time. Four optimization cases were tested and demonstrated good agreement with the predicted results. case 1 corresponded to pattern A but failed to detonate, while the others followed pattern C and successfully detonation. Although pattern C was also observed in the original initiator, it failed to detonate because the focusing region was too distant from the bottom of the cavity. Finally, a best initiator was selected and compared to the original initiator. The results showed that the threshold of the incident shock Mach number M-in was reduced by 24.9%, the pressure of the corresponding driver gas was reduced by 68%, and the focusing delay time shortened by 7.2%.