Particle impact ignition in high-pressure oxygen: Experiments, mechanisms, and multiphysics modeling

Particle impact ignition in high-pressure oxygen poses a significant threat to oxygen-rich turbomachinery, yet current experimental tests cannot access the temperatures and pressures encountered in service, limiting their predictive value. This study addresses this challenge through a combined experimental-numerical approach in which particle impact tests are used to calibrate a multiphysics model that predicts ignition under engine-relevant conditions beyond those explicitly tested. Experiments with 100-µm Ti-6Al-4V particles impacting Al₂O₃ and Ni targets reveal a critical impact velocity for ignition that decreases with increasing gas temperature and target hardness. At 300 K, no particle ignitions are observed on Ni, while the critical velocity on Al₂O₃ is 170 m/s; at 500 K, the respective critical velocities are 225 m/s and 84 m/s. The model, anchored by these data, incorporates plasticity, adiabatic heating, and oxidation-driven thermal effects to simulate impact and ignition behaviors. A parametric study over ranges of temperatures, pressures, and particle sizes relevant to rocket engine applications shows that increasing these parameters lowers the critical velocity by enhancing plasticity, oxide rupture, and localized heat generation, with especially high ignition risk above 600 K and 6 MPa, conditions common in oxygen-rich turbomachinery. These findings clarify the governing mechanisms of particle impact ignition, highlight the relative benefits of different mitigations such as soft inert coatings, and establish a predictive framework for ignition risk assessment in high-pressure oxygen systems.