Investigation of heat transfer and heterogeneous reactions during the slow cook off of a composite propellant

• This work is a new approach for the modelling of thermal decomposition of composite propellant.
• Heat and mass transfer are written for each elementary component of the pellet.
• There is no assumption concerning a limiting step in this modelling approach.
• Mains trends which were observed experimentally are well reproduced by this model.
• It is easy to change some part of the model .(modular), such as other elementary step in the heterogeneous chemical process.

In this work, a new modelling of interactions between components of aluminium/ammonium perchlorate/HTPB propellant during slow heating is presented. The phenomenon was previously described by experimental approaches performed in the laboratory. Heat and mass balance will be considered both in the solid and gas phases. The interaction of the decomposition products of both ammonium perchlorate and HTPB binder is shown thanks to previous experiments and a specific numerical model allows us to reproduce this trend. Mass and heat transfers are taken into account in each particle of ammonium perchlorate and inside the matrix of the HTPB binder. The chemical reaction in the gas phase is in interaction with the adsorption desorption of several species with regard to the surface grains. The whole set of equations is solved thanks to Comsol multiphysic solver and the numerical results are compared with mass loss measurements by means of a thermogravimetric device.