A comprehensive transient fluid-solid coupled numerical model for hybrid rocket nozzle erosion and its experimental validation

Abstract

The nozzle ablation of the hybrid rocket is a complex multi-physics coupling phenomenon that significantly influences the performance of the rocket. However, the coupling process for the various physics fields during the nozzle erosion problem remains unclear. To tackle this problem, a comprehensive hybrid rocket nozzle erosion numerical model that integrates the fuel regression process, the altering flame structure, the varying nozzle internal surface morphology, and the transient nozzle material heat transfer process is proposed in this work. Transient simulation is performed on the fluid-solid coupling physics field of the hybrid rocket adopting the dynamic mesh technique to depict the fuel regression and the nozzle erosion. Meanwhile, the nozzle erosion rate is obtained via the solid-fluid coupling heat transfer process and the thermal chemical erosion process. To validate the model proposed, a 20-s firing test is conducted on the 95 % H₂O₂/polyethylene propellant hybrid rocket adopting needle-punched structure carbon-ceramic material throat. The consistency between the simulation and experiment combustion chamber pressure, thrust, nozzle outer surface temperature, and throat radius increment further supports the effectiveness of the model proposed. Simulation results reveal that the heat flux peak in the nozzle internal surface decreased from 18 MW/m² to 2 MW/m² at a declining rate. The maximum erosion rate is observed in the latter of the converging segment and the front of the straight segment. Meanwhile, the uneven axial distribution of the erosion rate further leads to protrusion generation at the entrance of the straight segment of the throat, which further influences the local flow field, heat flux, and erosion rate. Overall, the erosion rate at the throat gradually increases over time and declines as the coordinates move downstream in the nozzle straight section.