多喷嘴射流式分离器内气固流动特性的数值模拟

基于商用软件Fluent 6.3.26,采用雷诺应力模型及DPM离散相模型并结合理论分析,对基于喷嘴造旋的射流式分离器内两相流动特性进行了模拟计算,得到了较为全面的两相流动规律与细节.结果显示,分离器内部切向速度峰值可达160 m·s^-1,自由涡区的切向速度约为130 m·s^-1,旋流强度明显高于传统旋风单管;沿轴向下,下行流流量逐次减少,其中稳流体顶部下行流降低最为明显,下行流减少致使颗粒卷入内旋流概率增加,分离效果下降;分离器内部局部存在顶部贴壁射流、射流区二次流及灰斗口旋涡流等次级流动;分离器压降约为27.43 kPa,喷嘴区内外旋流能耗分别为4.57 kPa(21.8%)、5.76 kPa(27.6%),稳流体区内外旋流能耗分别为5.85 kPa(27.6%)、4.01 kPa(18.9%);分离器对应的切割粒径较小,约为1.6 μm,极限粒径约为10 μm,符合工业应用要求;基于所建颗粒受力模型及模拟条件下,分离空间可分离的临界粒径为1～2 μm,3 μm及以上颗粒的逃逸浓度小于 0.15 g·m^-3,满足下游烟机对气流的净化要求.

Numerical simulation of gas-solid flow characteristics in multi-jet cyclone

Based on Fluent 6.3.26, the gas-solids two-phase flow behavior and details of multi-jet cyclone with swirling based on nozzles, was simulated and analyzed with the Reynolds stress model (RSM) and discrete particle model (DPM). Compared with conventional cyclones, peak value of tangential velocity and average value of free-vortex reached 160 m·s^-1 and 130 m·s^-1 respectively, generating higher flow rotation intensity. Volume rates of downward flow kept declining along the central line, particularly in the stabilization region, inducing more chances for particles being entrained by inner upward flow with lower collection efficiency. Local roof wall-jet and circulating flow nearby the inlet of the hopper were typical secondary flows of multi-jet cyclone. Gross pressure loss of the separator was 27.43 kPa, consisting of outer swirl flow 4.57 kPa (21.8%), inner swirl flow 5.76 kPa (27.6%) in the nozzles region, and outer swirl flow 5.85 kPa (27.6%), inner swirl flow 4.01 kPa (18.9%) in the stabilization region. Particles with diameters larger than 10 μm could be collected completely with cut-diameter 1.6 μm, making it suitable for industrial application. Analyzing with the particle mechanical model in this paper, the critical diameter of particle that can be separated was 1-2 μm and particle concentration for particles large than 3 μm in the vortex finder was less than 0.15 g·m^-3.