Temperature sensitivity of propellant burning rates

The effect of the solid propellant's initial temperature on its burning rate has long been recognized. This effect causes variations in the pressure, thrust, and burning time of solid propellant propulsion systems. An understanding of the effect of initial propellant temperature upon burning rate is essential for improving the performance of solid propellant propulsion systems. This paper presents the results of an experimental and theoretical investigation of the temperature sensitivity of the JANNAF standard composite propellant. Four combustion models were selected and calculations made using them for comparison to the experimental results. The models are: (1) the granular diffusion flame model based on the uniformly distributed heat release (KTSS) model, (2) the Beckstead, Derr, and Price (BDP) multiple flame model, (3) a modified BDP model, and (4) the petite ensemble model. The petite ensemble model is quite unusual since it describes the sizes of the propellant's oxidizer particles as a polydispersion of particle sizes. Experimentally, strands of the JANNAF standard composite propellant were burned in a modified Crawford type chimney burner with the propellant burning rate being measured as a function of pressure and initial temperature. The numerical values for the temperature sensitivity determined from the experimental results are compared to the results predicted by the theoretical models. It is concluded that the petite ensemble model provides better agreement with the experimental data because it models the size and size distribution of the oxidizer particles more realistically.