A Modeling Approach to Simulate Binder melt Effects in Composite Solid Propellant Combustion

Combustion modeling of composite solid propellants is essential for the prediction of ballistic parameters such as burn rate, pressure index, and temperature sensitivity. One such modeling technique which has shown excellent predictive capability for AP-HTPB propellants of solid loading >85%, is the Heterogeneous Quasi One-Dimensional (HeQu1D) model, which computes the ballistic parameters of composite propellants while accounting for the heterogeneity in the propellant. However, the model needs to consider binder melt effects to accurately predict the burn rates of relatively low solid loading (<85%) propellants. This work extends the current HeQu1D model by incorporating the effect of binder melt into the modeling framework, thereby improving the accuracy of the predictions. A theoretical model for binder melt from literature is mapped onto the HeQu1D model, and the governing equations are suitably revised to account for binder melt. The revised HeQu1D model is calibrated to simulate the effect of binder modifiers, namely Di-octyl Adipate and Isophorone Di-isocyanate, which influence the thermophysical characteristics of the binder melt. As such, the revised model in its current form can be applied to perform burn rate computations for AP-HTPB propellants of solid loading ≥ 80% with/without binder additives in the pressure range 20 to 130 atm. However, the model fails to capture the occurrence of quenching in propellants of solid loading ≤ 75%. Possible reasons for this and way forward are outlined.