A two-phase flow modeling and interval optimization framework for enhancing the launch safety of propellant charge

• Revealed intense gas–solid heat transfer process, with convective heat transfer for fracture propellant reaching 6.5 × 105 W/m 2 . • Established key relationships for intergranular stress and equivalent shape function under different propellant mass ratio. • Developed an interval optimization framework to actively improve the launch safety under different propellant mass ratio. The large-scale fracture of the propellant charge at low temperatures is the fundamental cause of chamber explosions caused by the propellant charge. To enhance launch safety, develops a novel framework that integrates a high-fidelity two-phase flow dynamic model with an interval uncertain optimization method. The physics-based model explicitly simulates propellant compression and fracture processes, and its accuracy is validated against experimental results, the relative error between the experimental and simulated values of the ballistic indicators does not exceed 0.2 %, showing good agreement in chamber pressure and velocity. Analysis of gas–solid heat transfer and ballistic parameter distributions further confirms model validity. To enable optimization under different propellant mass ratio, we establish relations for intergranular stress and equivalent shape function under different propellant mass ratios. Then we have considered the uncertainty of propellant parameters, an interval optimization model is formulated. A back-propagation artificial neural network surrogate model is trained to approximate the complex interior ballistic response, enabling efficient solution of the two-layer nested optimization problem. The key outcome is an optimized propellant parameter set that significantly reduces compression stress at the projectile base-the root cause of low-temperature fracture. The results showed that the compression stress at the bottom of the projectile decreased by about 12 %, and the maximum chamber bottom pressure is 507.06 MPa, which is lower than the allowable pressure of 510 MPa. In addition, the interval midpoint of the muzzle velocity is 1627.2 m/s, and the interval radius of the muzzle velocity is 10.73 m/s, both of which are within the allowable range of the indicators.