Abstract:

The inlet velocity affects the flow field of a cyclone separator，and the shape of the inlet pipe is one of the most important factors that may change the velocity. With the optimization for the shape or structure of inlet pipe，cyclones with better performance can be designed. Here the separation efficiency and the flow field of two double-inlet separators with straight inlet pipes and a vortex-tube inlet are analyzed and compared. It is shown that the total separation efficiency of the cyclone with vortex-tube inlet is 1.5% higher than that with the straight inlet，and the pressure drop of the former is 25% lower. The reason for lower pressure drop is that in the vortex-tube inlet cyclone the flows in the inlet pipe and in separation space are both vortex patterns，alleviating the energy consumption when the two streams collide. The higher separation efficiency is resulted from that the tangential velocity in the separator with vortex-tube inlet is 15% higher than that with the straight-pipe inlet. Thus the cyclone with vortex-tube inlet can reduce the cut size and improve the separation efficiency. According to the vortex theory，the local vortex in the inlet pipe of the vortex-tube inlet separator will create an induced velocity field，which increases the tangential velocity in the separation space without additional energy loss. Thus，using vortex-tube inlet and increasing the vortex intensity should be effective to improve the separation performance.

摘要：

旋风分离器进口段管路的结构关系着进口气速的分配，直接影响到下游分离空间三维速度场的形式，合理设计进口管的样式是挖掘分离器分离潜力的可能入手之处。采用实验及数值模拟手段，对环管和直管2种进口管路下轴对称双进口分离器的性能与流场作了对比研究。结果表明，环管进口的分离器分离总效率比两侧进口的平均高1.5个百分点，而压降损失降低25%以上。前者阻力小的原因在于进口环管内气流为局部的涡旋，与分离器内旋涡流动的形式接近，两股气流交汇时碰撞程度轻，附加的额外能耗较小；而总效率提高的原因为，环管进口的分离器切向速度比两侧进口的分离器约高0.15倍进口气速，能增强颗粒受到的离心作用、减小切割粒径，从而提升分离器总效率。根据涡旋理论，局部区域的涡旋会对整个流动空间产生感生的速度场，由于环管进口的分离器进口管内局部涡旋的存在，整个分离空间的切向速度场被增强。这种由涡旋感生速度场提升分离器切向速度的方式，加深了分离器运行过程中压头向速度转换的程度，不会消耗额外的能量。因此，采用旋涡流的进气方式，并合理提高进口涡旋的强度，是分离器分离性能进一步提升的新途径。