Study on the Ablation Mechanism of the First Pulse Insulation Layer in a Double-Pulse Solid Rocket Motor

In this work, numerical simulation and experimental research were carried out on ablation mechanism of the first pulse (I pulse) insulation layer in a double-pulse solid rocket motor (SRM). Firstly, based on the internal thermal environment of the typical double pulse SRM, the internal flow field in combustion chamber of the double-pulse SRM with soft type pulse separation device (PSD) under the second pulse (II pulse) working condition was numerically simulated. The results showed that the main reason for the difference of ablation in I pulse insulation layer was the difference of gas phase velocity. Secondly, based on the simulation analysis results, the experimental system for ablation of insulation layer was developed, and the ablation performance experiments under two gas phase velocities were carried out. It was found that a brittle carbonized layer had been formed on the surface of the insulation layer after the completion of I pulse work. In addition, at the beginning of II pulse work, the suddenly generated gas flow made a denudation effect on the carbonized layer, which consumed a part of the carbonized layer. After the carbonized layer was peeled off, the gas flow continued to ablate the matrix of the insulation layer. Finally, the simulation analysis of the ablation process of the insulation layer under two gas phase velocities was carried out. The results showed that the velocity of the fuel gas is the main factor affecting the ablation rate of the insulation layer, which was consistent with the experimental results. It is proven that the model can be used to estimate the ablation amount of insulation of solid rocket motor. The conclusion can provide a significant reference for the internal heat protection design of the double-pulse SRM.