Compression fracture, heat transfer, and uncertain optimization of launch propellant charge

In response to the abnormal phenomenon of a certain large caliber artillery having a maximum chamber pressure at low temperatures higher than normal temperature, and the maximum chamber pressure at low temperatures exceeding the allowable pressure of the index, this large caliber artillery is taken as the research object. The interval uncertain optimization method is used to conduct uncertain optimization research on the interior ballistic parameters, to improve the firing safety of the propellant under uncertain conditions. First, an interior ballistic model was established without considering the fracture of the propellant at room temperature, as well as an interior ballistic model considering the compression fracture of the propellant under low temperature conditions. Then, numerical solutions were carried out using dispersion controllable schemes. The variation curve of the bottom pressure of the chamber showed good consistency with the measured results. At the same time, simulation and experimental results jointly proved that the propagation speed of stress waves between particles of the propellant at low temperature was greater than that of flame waves, resulting in the compression stress acting on the propellant at the bottom of the projectile and causing it to fracture before ignition. Finally, based on the interval uncertainty optimization method, an interior ballistic interval uncertainty optimization model considering the compression and fracture of the launching charge was established. A two-layer nested optimization strategy and a backpropagation neural network approximation model were used to solve the problem. The calculation results showed that after optimization, the maximum breech pressure decreased from 526.40 MPa to within the range of [478.86, 502.29] MPa, meeting the requirements of the design indicators. The lower limit of the optimized muzzle velocity was 1616.64 m/s, meeting the minimum muzzle velocity requirement. At the same time, the compression stress at the ignition time of the bottom area of the projectile was reduced by 16.8%, reducing the degree of fracture of the launching charge in the bottom area and suppressing the rapid increase in gas generation rate. The optimization results obtained provide reference for improving the launch safety of large caliber artillery in uncertain environments.