Dynamic Ablation Characteristics of C/C Nozzles under Short-duration Firing Conditions

To investigate the transient ablation behavior of C/C nozzles under short-duration firing conditions, the ground hot-firing experiments and numerical simulations are conducted. The relative error between the theoretically predicted and experimentally measured values of chamber pressure during the stable pressure-rise stage is less than 6.7%. The evolution process of nozzle surface recession is numerically simulated, and the maximum relative error between the simulated and measured results is 3.2%. The results indicate that nozzle ablation under short-duration firing conditions exhibits a pronounced spatial and temporal non-uniformity, and the ablation process can be divided into an initial acceleration stage and a stable stage. The downstream region of the convergent section is most severely affected by the coupled effects of thermochemical ablation and mechanical erosion, whereas the ablation in the throat region is dominated by thermochemical mechanisms, and the divergent section is relatively weakly affected. Further analysis shows that the ablation rate increases with the increase in combustion chamber pressure and gas temperature, and the larger particle size enhances the intensity of mechanical erosion. The present results provide a reference for ablation prediction and structural design of nozzles in short-duration solid rocket motors.