NUMERICAL STUDY OF THE IGNITION DYNAMIC OF A BASE BLEED UNIT DURING THE INTERIOR BALLISTICS PHAS

The aim of this article is to study numerically the ignition dynamic of a base-bleed (BB) unit during the internal ballistics (IB) phase. A Forward Facing Step case is studied under the physical conditions of the first instants of IB, in order to characterize the convective fluxes at the solid propellant surface of the BB. Large-Eddy Simulations are carried out with the CEDRE CFD code. The recirculation zone obtained in the flow significantly increases convective fluxes at the inlet of the BB channel. The instabilities generated by the recirculation zone have frequencies in line with literature. A second case is proposed to study BB ignition using a dynamic mesh technique and an unsteady solid propellant ignition model applied to the BB propellant surface. It can be shown that the propellant ignites quicker at the inlet of the BB channel due to higher convective fluxes, corresponding to the location of the recirculation zone.