Variation of interior ballistic parameters at a constant mean pressure in the postprojectile space of a gun barrel

An analytical solution of the problem of determining the interior ballistic parameters in the postprojectile space of a gun under constant pressure is proposed. Simple formulas for temperature calculation are obtained. It is shown that the temperature can be as high as the thermodynamic value at constant volume, and it can be lower than the thermodynamic temperature at constant pressure. Under quasistationary conditions, the density and temperature of combustion products tend with time to values observed in the case where both the pressure and density are constant. The effect of the initial burning surface of the projectile on parameters corresponding to the beginning of the quasistationary state is estimated. The results obtained can be useful in solving design problems.