SIMULATION OF IGNITION AND COMBUSTION OF LOW-VULNERABILITY PROPELLANT FOR ARTILLERY

摘要

This paper deals with a novel approach to numerically simulate the ignition and combustion of a bed of grains consisting of low-vulnerability ammunitions (LoVA) propellants in a gun tube. The originality of the work relies on a dual approach, since the same combustion wave model is used both for ignition and stationary combustion near the surface of the propellant grains. The rate of decomposition for propellant grains is written in terms of a transient one-dimensional heat equation inside the solid with a heat source. This heat source is related to the flame structure developing at the burning propellant surface and allows sustaining the thermal decomposition process in a stationary combustion. This stationary combustion follows the Vieille's law and the attainment of ignition depends on the level of incoming heat flux. Another aspect of the modelling is related to the porous medium, which is taken into account since spherical grains are packed inside the gun combustion chamber. Fluid flow equations for the gas phase are written with a full compressible flow in 2D transient formulation and a multistep reaction source is considered in the energy equation. Finally, the propagation of the combustion front after ignition during the early stages of the internal ballistic cycle of the gun tube is considered in a simplified geometry. The results are compared to the experimental Vieille's law of the propellant, showing the relevance of the proposed approach for future multidimensional studies.