Direct numerical simulation of flow past a reactive/inert mixed particle pair

Abstract

During the pyrolysis and gasification processes inside fluidized bed reactors, a single reactive particle is generally surrounded by multiple inert heat carrier particles. In this work, we focus on the simplest mixed particle pair (one reactive particle: P1, and one inert particle: P2) to investigate the joint effects of the Stefan Reynolds number (Resf), the particle Reynolds number (Re), separation distance normalized by particle diameter (L), and relative orientation (α) on the drag force exerting on each particle by particle-resolved direct numerical simulations. The results show that when particles are placed in a tandem arrangement, the blocking effect on P2 is weakened/strengthened with negative/positive Stefan flow since the effective diameter of P1 is smaller/larger than its real diameter. When L = 1.25, Re = 3, and particles are placed in tandem, the drag force of P1 decreases as Resf increases, but the reduction of the drag force decreases as Re increases. Under such conditions, the positive Stefan flow induces the repulsion between the two particles; thus, the drag force of P2 increases as Resf increases. When Resf = 3 and P2 is located downstream, the repulsive force felt by P1 can partially offset the drag force at L = 1.25, Re = 3. Moreover, the negative/positive Stefan flow enhances/weakens the drag force of P2 when it is located upstream. The Stefan flow has a negligible effect on the drag force of P2 when L = 3.