撞击流气化炉内气粒两相流动的数值模拟

Numerical simulation of gas-particle two-phase flow in impinging streams gasifier

对撞击流气化炉内气粒两相流动进行了三维数值模拟。在Euler坐标系中计算气相流场,在Lagrange坐标系中跟踪颗粒运动轨迹,考虑了熔融灰渣颗粒间的碰撞合并、反弹。模拟结果与冷模流场测试数据、热模实验现象一致。通过考察不同工况下的流场计算发现:增加喷嘴以上直段高度使流场更对称,物料停留时间增加,若同时提高入口气速将使颗粒在炉壁的沉积量增加;模拟结果与热模实验都表明撞击形成的强烈湍流和火焰主要集中在撞击中心;颗粒碰撞合并使炉内颗粒选择性团聚,但炉内颗粒浓度分布整体比较合理;Stokes数为0.19的小颗粒跟随性较好,较大Stokes数颗粒不易被流场控制,且对流场具有较大的影响。

To investigate the behavior of gas-particle two-phase flow in the impinging streams gasifier, a 3D numerical model was used to simulate the flow field characteristics inside the gasifer. The model was based on the Euler-Lagrange concept. The gas flow was treated as continuous phase with an Euler frame of reference, while the Lagrange method was used to trace the particles. The behavior of inter-particle collision and its effects on particle dispersion were presented. The predicted results agreed well with cold- model and hot-model experimental data. In order to investigate the influence factors on the flow field that might have a significant effect on the coal gasification process, some parametric studies were performed by changing the gas-solid flow inlet velocity, size of particle distribution, and gasifier geometry. The results showed that the residence time of particles increased with the straight section height above the burner, and the deposition flux increased with the inlet velocity. The model and experiment results showed that the highest turbulence intensity and flame of collision converged near the center of the impinging zone. The inter-particle collision led to particle agglomeration, but the holistic distribution of particle concentration was reasonable. Finally, the parameter of particle size was also investigated, and the particles with a smaller Stokes number had weaker influence on the flow field.