Multiphase reactive flow and heat transfer simulations in the unlocking components of an ultra-low shock pyrotechnic separation nut

This study presents a multiphase reactive flow and conjugate heat transfer model for the unlocking components in an ultra-low shock pyrotechnic separation nut. The process of the shape memory alloy (SMA) tube heated by the heat released from the combustion of the micro gas pyrotechnic charges was simulated. The established model was validated by comparing the simulation with experimental results for the temperature of the outer wall of the SMA tube. Then, the detailed ignition and combustion of micro gas pyrotechnic charges, transient flow of combustion products, and heat transfer in the SMA tube were analyzed. The effects of the amount and burning rate of micro gas pyrotechnic charges on the unlocking time were investigated. It is found that the unlocking time decreases with an increase in the amount of micro gas pyrotechnic charges. Moreover, the reduction range of the unlocking time decreases with the increase in the amount of micro gas pyrotechnic charges. Reducing the differences in the burning rate contributes to enhancing the consistency of unlocking time.