旋风分离器内颗粒浓度分布特性的数值分析

采用改进的雷诺应力模型和分散的颗粒随机轨道模型，并利用单元内颗粒源法对旋风分离器内的颗粒浓度分布进行数值模拟，与试验结果对比表明两者吻合较好，有较高的预报精度。数值模拟结果表明，旋风分离器外壁的颗粒浓度呈螺旋带状分布，且螺旋灰带以一定的频率上下窜动，在环形空间和灰斗的顶板下方存在顶灰环，且顶灰环不均匀，具有显著的非对称性；在分离空间下部排尘口附近有明显的颗粒返混，范围在排尘口上方约1.5 D (筒体直径)以内，排尘口上方的强旋流动对颗粒有显著的二次分离作用。讨论粒径(3～23 μm)、工作温度(20～ 1 000 ℃)、入口含尘浓度(0.03～10 kg/m3)和进气速度(12～30 m/s)对颗粒浓度分布特性的影响规律。

NUMERICAL SIMULATION ON PARTICLE CONCENTRATION DISTRIBUTION IN CYCLONE SEPARATOR

The particle concentration distribution in cyclone separator is numerically simulated with the particle-source- in-cell (PSIC) method, the interaction between particles and gas phase is taken into account, and the advanced Renolds stress model (ARSM) and stochastic particle tracking model (SPTM) are adopted. Predictions are in reasonable agreement with the experimental results. Numerical simulation reveals that particle concentration near the wall of cyclone separator represents a helix-dust-ring distribution, but the dust ring is unstable and switches up and down with a frequency. There is also an unequal and non-axisymmetric dust ring near the top plate of cyclone separator. The axial distribution of particle concentration in the inner vortex (r/R0.3) is shown that the fine particles are entrained seriously from the dust hopper in a range of height 1.5D (cyclone diameter)above the dust discharge port, but the secondary separation of particles by the strongly swirling flow is also obvious. The radial distribution of particle concentration is divided basically into two regions, the concentration of particles is low and equal in the inner region of r/R0.75, but raise sharply in the outer region of r/R>0.75. Moreover, the influence of particle diameter (3～23 µm), temperature (20～1 000 ℃), inlet dust loading (0.03～10 kg/m3) and inlet velocity (12～30 m/s) on the particle concentration distribution are investigated respectively.