Themes: Engineering sciences: fluid mechanics, energetics
Thesis location: Explosion and Fire Laboratory (LIE) - Cadarache (13)
Start: October 2021
master's degree in energy mechanics and/or numerical fluid mechanics
Age limit: 26 years old unless otherwise stated.
The risks of dust explosions are frequently encountered in industrial installations. The industrial sectors are numerous (pharmaceutical, cereal industry, etc.) and the involved particles are of great diversity (organic materials, etc.). In nuclear safety analysis, one of the scenarios deals with the risk of graphite dust explosion that may occur during decommissioning operations of UNGG (Uranium Natural Graphite Gas) reactors. Other situations are affected by the risk of dust explosion, for example zirconium powders used in the manufacture of fuel cladding or tungsten or beryllium dust re-suspended in the future tokamak ITER in the case of loss of vacuum accident. The proposed thesis is part of the development of a predictive calculation tool for the propagation of a planar laminar flame in dust clouds. The turbulent flame speed models being built as a correction of the laminar flame speed, this tool will be used as a preprocessor of a CALIF3S-P2REMICS calculation like CHEMKIN or CANTERA for gaseous mixtures. The development of such a tool is mainly motivated by the number of parameters (composition, particle size, etc.) that appears to be too large to perform a systematic experimental exploration. Moreover, this experimental exploration is made difficult as the suspension of the dust to obtain a homogeneous cloud makes it difficult to overcome the effects of turbulence. The developments carried out during a first thesis on the subject made it possible to develop an Euler-Lagrange simulation code for the combustion of graphite particles. The developments carried out within the framework of an up-scaling methodology have made it possible to provide a critical analysis of the modeling of mass and heat transfers. The proposed thesis subject consists in continuing the developments carried out for graphite particles and taking into account so-called hybrid mixtures, typically mixtures made up of graphite particles and metallic particles. These are mainly particles of iron or aluminum for UNGG applications and tungsten or beryllium for ITER applications. For this kind of particles, the radiative transfers play an important role on the speed of the combustion front and their modeling will be based on the same up-scaling methodology used to describe heat transfers by conducto-convection.