旋风分离器内颗粒浓度场的数值模拟

Numerical simulation on particle concentration distribution in cyclone separator

采用改进的雷诺应力模型和颗粒随机轨道模型对旋风分离器全空间内颗粒浓度分布进行了数值模拟。结果表明,旋风分离器分离空间的浓度场沿径向可划分为中心的颗粒逃逸区、边壁的颗粒捕集区和中间的颗粒分离区。颗粒捕集区的颗粒在器壁表面形成高浓度的灰带螺旋下行,灰带以一定的频率上下波动;颗粒分离区浓度分布均匀,颗粒处于被分离状态;颗粒逃逸区的颗粒浓度很低,颗粒螺旋上升逃逸。旋风分离器的浓度场沿轴向分布比较复杂,在环形空间的上部和灰斗的上部存在顶灰环,浓度分布具有显著的非轴对称性,在升气管入口下方0.25倍筒体直径(Φ)范围内存在短路流造成的高浓度区,在排尘口处存在旋转气流摆动造成的颗粒返混高浓度区。模拟结果与实验数据吻合较好。

The particle concentration distribution in a cyclone separator was numerically simulated based on the modified Reynolds stress model and stochastic particle tracking model on the platform of commercial software of FLUENT 6. 1. The interaction between the particles and the gas phase and the turbulent diffusion of particles were taken into account. The particle concentration along the radial direction inward from the wall in the separation space was divided into collecting zone near the wall, escaping zone in the center region and separating zone in the middle. In the collecting zone, particles showed helix sol- id strand distribution and moved downward. The solid strand was unstable and moved up and down with a low frequency. Particle concentration was uniform and particles would be separated in the separating zone. In the escaping zone, particle concentration was very low and most of particles escaped with the inner vortex flow. Particle concentration distribution was complex along the axial direction. The asymmetric dust ring existed near the top plate of the annular space and dust hopper. The local high concentration existed urlder the entrance of the exit tuhe with a distance about 0. 25 Φ（ barrel diameter） and the entrance of the dust hopper, which resulted from the short-circuit flow and the re-entrainment of the fine particles in the inner vortex flow due to the agitation of separated particles, respectively. The numerical simulation results agree well with the experimental ones.