Modelling and Calculation of the Initial Ignition Gas Pressure Flow through a Rigid Porous Medium in a 100 mm Ignition Simulator

To acquire a better understanding of the early ignition phenomena in a 100 mm ignition simulator loaded with a packed propellant bed, a theoretical model of the ignition gas flow through the rigid porous medium was developed. Three pressure gauges were installed in the lateral side of the ignition simulator for post ignition measurement of the chamber pressure. The pseudo-propellant loaded into the chamber was similar in size to the standard 13/19 single-base cylindrical propellant. It was composed of a rigid ceramic composite with low thermal conductivity. It was assumed that the pseudo-propellant bed was rigid in contrast to the assumption of an elastic porous medium. The calculated pressure values were well verified by the experimental data at a low loading density of the pseudo-propellant bed of 0.18 g•cm-3. However, there was still error between the experimental and the calculated results in the early pressure peak position closest to the ignition primer when the loading density of the pseudo-propellant bed was increased to 0.73 and 1.06 g•cm-3. This error is attributed to the change in local permeability of the pseudo-propellant bed at high loading densities, which is assumed, for ease of modelling, to be constant in the model. These calculations may enable a better understanding of the physical processes of ignition gas flow in an ignition simulator loaded with a pseudo-propellant bed.