An optimisation study of a shock-wave-focusing geometry is presented in this work. The configuration serves as a reliable and deterministic detonation initiator in a pulsed detonation engine. The combustion chamber consists of a circular pipe with one convergent–divergent axisymmetric nozzle, acting as a focusing device for an incoming shock wave. Geometrical changes are proposed to reduce the minimum shock wave strength necessary for a successful detonation initiation. For that purpose, the adjoint approach is applied. The sensitivity of the initiation to flow variations delivered by this method is used to reshape the obstacle’s form. The thermodynamics is described by a higher-order temperature-dependent polynomial, avoiding the large errors of the constant adiabatic exponent assumption. The chemical reaction of stoichiometric premixed hydrogen-air is modelled by means of a one-step kinetics with a variable pre-exponential factor. This factor is adapted to reproduce the induction time of a complex kinetics model. The optimisation results in a 5% decrease of the incident shock wave threshold for the successful detonation initiation.

这项工作提出了对冲击波聚焦几何形状的优化研究。该配置在脉冲爆震发动机中用作可靠的确定性爆震起爆器。燃烧室由一个带有一个会聚-发散的轴对称喷嘴的圆形管组成，该管用作入射冲击波的聚焦装置。提出了几何变化以减小成功引爆所需的最小冲击波强度。为此，采用了伴随方法。通过此方法传递的初始流量对流量变化的敏感性可用于重塑障碍物的形状。用一个高阶温度相关多项式描述热力学，避免了恒定绝热指数假设的大误差。化学计量的预混合氢气与空气的化学反应是通过具有可变预指数因子的一步动力学来建模的。该因子适用于重现复杂动力学模型的诱导时间。优化使成功引爆的入射冲击波阈值降低了5％。