Two-dimensional particle-resolved numerical simulation for burning particles in laminar boundary layer flows

Abstract

In the present work, two-dimensional particle-resolved simulations of burning char particles near the wall were performed to understand the effects of gap ratio, $G/D$, and particle distance, $L/D$, on the char combustion process of two burning particles, where $D$ is the particle diameter, $G$ is the the distance between the bottom of the particle and the wall, and $L$ is the distance between the two particles. The results indicate that as $G/D$increases, both heterogeneous and homogeneous reaction rates of the particles increase. With $L/D=1.5$, the combustion of two particles can be regarded as an entity. As $L/D$ increases, the reaction rate of the particles also rises. With $L/D=6.0$, the two particles are burning independently. The transport budgets of species on the particle surface are examined. The results show that diffusion and reaction dominate the transport of gascous species on the particle surface, while small $G/D$ and$L/D$ can inhibit species exchange on the surface. The drag and lift forces on combustion particles are measured. It is shown that increasing $G/D$ and $L/D$ results in increased the drag force of the particles, while the lift force first increases and then decreases with increasing $G/D$. Further investigation of the local drag force shows that the increase in drag force is due to the rise in the pressure component from the increased pressure drop and the rise in shear drag from both increased velo city gradient and kinematic viscosity.