Hydrodynamic resolved simulation of a char particle combustion by immersed boundary-lattice Boltzmann method

A Lattice-Boltzmann model coupled with boundary method is proposed for the hydrodynamic resolved simu-lation of a single char particle combustion. A pure lattice Boltzmann scheme with multi distribution functions is presented for this low Mach reactive flows. Real varying thermodynamic and transport properties are considered, and the fluid density can bear significant change depending on the varying temperature and species concen-trations. The recently proposed boundary-thickening based direct forcing-immersed boundary method is extended to implement the boundary conditions of velocity, temperature, and species concentrations at the char particle surface. Two heterogeneous reactions at particle surface and one homogeneous reaction in fluid are adopted to describe the combustion. The Stefan flow near the particle surface caused by the heterogeneous reactions is also considered. A satisfactory agreement can be found between the present simulation results and the previous experimental and numerical results. Three flame modes of a char particle combustion and the transition mechanisms between them are investigated. Furthermore, the effect of hydrodynamic interaction and the oxygen concentration in O-2/CO2 atmosphere on particle combustion behavior are explored in detail. The present work establishes the foundation for the efficient simulations of particle combustion with size change and motion.

Automated summary

A lattice-Boltzmann model coupled with boundary method is proposed for simulating the combustion of a single char particle. The model considers real varying thermodynamic and transport properties and uses a boundary-thickening based direct forcing-immersed boundary method for implementing boundary conditions. Different reactions are adopted to describe the combustion process. The simulation results show good agreement with previous experimental and numerical results.