基于Q判据的不同排气管直径旋风分离器内部涡分析

为了研究排气管直径对旋风分离器内部流场的影响，采用雷诺应力模型对4种不同排气管直径的旋风分离器进行气相流场的数值模拟，同时引入Q判据识别内部空间涡的结构。结果表明，利用Q判据做出的涡等值面，可以较为直观地看出涡结构的变化趋势。在一定范围内，减小排气管的相对直径，可以使旋风分离器内部流动更加稳定；但当排气管直径过小时，内部湍动作用会加剧，能量损失加大。在壁面处，有封闭的涡线形成，能量损失加剧；改善壁面处的涡平衡，可以有效抑制封闭涡线的形成，从而减小能量损失，提高分离效率。此外，涡核摆动并不是随着排气管直径的增大就越剧烈，而是存在一个极值，在极值处涡核摆动整体最小；适当地调整排气管直径，有利于涡结构的平衡，提高流体的稳定性，从而提高分离效率。

Vortex Analysis of Cyclone Separators with Different Vortex Finder Diameter Based on Q Criterion

Aiming to analyze the impact of vortex finder diameter on the flow field in the cyclone separators, Reynolds stress model was used to simulate the flow field in four cyclone separators with different vortex finder diameters. In addition, the Q criterion was applied to identify the structure of the vortex. Simulation results showed that the changing trend of vortex structure can be visually observed based on the 3D iso vortex surface extraction according to Q criterion. Within a certain range, reducing the relative diameter of the vortex finder could lead to more stable internal flow in the cyclone. However, if the vortex finder diameter is too small, this will cause intensified internal turbulence, and thus increased energy loss. Moreover, if  closed vortex lines occurred near the wall, this will cause more energy loss. Therefore, improving vortex balance near the wall can reduce the energy cost and improve the separation efficiency. Furthermore, the vortex core oscillation does not increase linearly with vortex finder diameter, but has an optimum value. At the optimum point, the total vortex core oscillation can be minimized. Therefore, vortex finder diameter can be appropriately adjusted to balance the vortex and thus improve flow stability, and eventually help improve the separation efficiency of the cyclone. 