Computational Nozzle Design for Pulsed Detonation Thrusters for Vacuum Operations

This study presents the numerical design and optimization of a convergent–divergent nozzle integrated with a pulsed detonation combustor (PDC) operating under reduced outlet pressure conditions. The work builds upon an experimentally validated TRL 4 PDC with demonstrated vacuum operation, which provides realistic inlet boundary conditions for the nozzle simulations. The divergent section of the nozzle is generated using the Method of Characteristics (MOC), while the overall geometry is subsequently optimized using a parametric process aimed at enhancing thrust and specific impulse while minimizing nozzle length, thereby reducing the overall size and mass of the propulsion system. Axisymmetric numerical simulations are performed to evaluate nozzle performance at an imposed external pressure of 100Pa, corresponding to the low-vacuum laboratory conditions of the preceding experimental campaign. The CFD results predict that an appropriately designed and compact nozzle significantly improves propulsive performance relative to the baseline configuration without a nozzle, increasing thrust output from 4.4 N to 5.94 N cycle-averaged with 16.5 N peak thrust. By combining MOC-based contour generation, numerical optimization, and unsteady CFD, the present work provides a computationally assessed nozzle geometry for subsequent manufacturing and experimental testing with the reference PDC. The optimized geometry obtained in this study provides a computational basis for subsequent experimental investigation.