Study on Expansion Characteristic of Twin Combustion Gas Jets in Five-Stage Cylindrical Stepped-wall Observation Chamber

The five-stage cylindrical stepped-wall observation chamber is designed to investigate the method of controlling the interior ballistic stability in bulk-loaded propellant guns. The expansion and mixing process of twin combustion gas jets in liquid is studied by means of high speed photographic system. The influence of multiple parameters on jet expansion shape is discussed. Based on the experiment, the three-dimensional mathematics model is established to simulate the expansion process of twin gas jets in liquid. The pressure, density, temperature, velocity contours and evolutionary process of vortices are obtained. Results show that vortices behind the corner of the steps are formed due to the inducing effect of steps. The jets can expand along the axial and radial direction simultaneously, weakening the Kelvin-Helmholtz instability. The numerical simulation results of axial expansion displacement are in good agreement with the experimental data.