Modeling the burning rate of heterogeneous propellants over a wide range of pressures

The variation of steady burning rate for heterogeneous propellants over a wide range of pressure is studied by experimental methods and theoretical analysis. Two kinds of heterogeneous propellants, GATo-1 CMDB propellant and 86 series composite propellant, are selected. An explanation for two inflection points observed in burning rate-pressure curve is presented. It is concluded that condensed-phase reaction dominates the burning process in the low-pressure region, which presents a low-pressure exponent, whereas heat feedback from the gas phase predominates in the high-pressure region with a high-pressure exponent. In the medium-pressure region, these two factors influence the burning process cooperatively and pressure exponent reduces first and then rises. Results calculated from the model show good agreement with experimental data. Thermal parameters analysis indicate burning rate is more sensitive to thermal conductivity of condensed phase, activation energy of condensed phase, specific heat capacity, and delay time of heat release of the condensed-phase reaction in high pressures. This model is of significance in burning rate characteristics in high pressures and interior ballistic properties in solid-propellant impulsive microthruster.