PM2.5细颗粒物分离技术的数值模拟和性能改进

旋风切割器是分离细颗粒物的主流技术,为了提高其分离效率并减少能耗,本文分析了切割器参数对粒子分离的影响.基于计算流体动力学数值模拟的方法,分析了VSCC型旋风切割器的内部湍流流场,比较15~25L/min范围内不同流速下的涡流变化情况;基于"逃逸率"概念,模拟1~6μm内不同粒径的细小粒子逃逸率随流速的变化曲线,考察临界粒径dc并结合气溶胶实验进行验证,分析流速对分离性能的影响程度;之后考察了流速对压降的影响,提出一种几何参数改进方案,在避免压降升高的前提下提高分离性能.研究表明:流速影响旋风切割器内的湍流分布,随着流速增大,临界粒径变小,分离性能得到提升,模拟结果在16 L/min的流速下,临界粒径约为2.5μm,与实验结果基本一致,并且利用曲线给出计算总分离效率的思路;调节几何参数可以实现在低能耗的前提下,将临界粒径进一步降低为1.1μm,收集效率更高.研究结果可为PM2.5切割器的商业选择或工程设计提供理论参考.

Numerical Modeling and Performance Improvement for PM2. 5 Separating Technology

Cyclone separator is a mainstream technology of separating fine particulate matter. To improve separation efficiency and save energy, several key parameters of separator were analyzed in this paper. Based on numerical simulation method of computational fluid dynamics （ CFD）, internal turbulent flow field of VSCC cyclone separator was analyzed and turbulent flows were compared under different flow velocities ranging from 15 L/min to 25 L/min. Then based on the concept of penetration, variation curves of particulate penetration with flow velocity under different particulate sizes ranging from 1μm to 6 μm were simulated. Critical particle size de, was studied and validated by aerosols experiments in order to analyze the influence of flow velocity on separation performance. With observation of flow velocity＇ s impact on pressure drop, a method of optimization geometric parameters was proposed to improve separation performance of separator on the premise of low pressure drop. Results show that flow velocity exerts a sig- nificant influence on the turbulent distribution. When the flow velocity is higher, the critical particle gets smaller and the separation performance gets better. Simulation results show that the critical diameter is approximately 2.5 μm at flow velocity of 16 L/min, approximately consistent with the experimental resuit. The theory for calculating separation efficiency was put forward according to the curve. Meanwhile, adjusting the geometric parameters is an effective way to reduce critical diameter to 1.1 μm under thecondition of low energy loss, and to achieve higher collection efficiency. The results obtained in this paper offer reference for PM2.5 separator commercial operation and engineering design.