旋风分离器自然旋风长的试验研究

Experimental Study of the Natural Cyclone Length of a Cyclone Separator

采用激光多普勒测速系统(LDV)对φ300mm、升气管直径为De=100、135和180mm的旋风分离器内气相流场进行了测量,主要分析了旋风分离器的自然旋风长。测量结果表明,旋风分离器内的旋转流呈现明显的衰减特性。沿升气管出口轴向向下,切向速度和轴向速度逐渐减小,对于直径100mm升气管,最大切向速度由2.55Vi开始衰减,并且最大切向速度的径向位置由0.28R逐渐向壁面移动,内部的刚性涡逐渐扩大,外部的准自由涡逐渐缩小,最终在轴向5.2D处最大切向速度点接近筒体壁面,准自由涡消失,此位置以下形成完全的刚性涡;对于直径135和180mm升气管,最大切向速度的值和位置也具有相似的变化。在此基础上,提出了旋风分离器自然旋风长的定义,即从升气管下口到准自由涡消失位置的距离为旋风分离器的自然旋风长Lc,依据实验结果给出了计算式(5)的关系式。最后通过分析旋风分离器内旋转流的衰减特性和两涡之间的能量传递过程,进一步说明了旋风分离器自然旋风长的物理意义。

By using a Laser Doppler Velocimetry (LDV) system, measured was the gas-phase flow field in a φ300 mm cyclone separator, of which the riser diameter is 100, 135 and 180 mm respectively. Mainly, the natural cyclone lengths of the separator were analyzed. The measurement results show that the swirling flow inside the cyclone separator assumes conspicuous attenuation characteristics. Downwards along the axial direction from riser outlet, the tangential and axial speed will gradually diminish. For the riser with a diameter of 100 mm, the maximal tangential speed will begin to attenuate, starting from 2.55 Vi. Moreover, the location of the maximal tangential speed in the radial direction will progressively shift to the wall surface beginning from 0.28 R. The internal rigid vortex will gradually expand and the external quasi free vortex becomes smaller. Finally, the maximal tangential speed point will approach the shell wall surface at the location of 5.2 D in the axial direction, and the quasi free vortex, disappear, thus forming a full rigid vortex below the above-mentioned location. For the risers with a diameter of 135 mm and 180 mm, the value and location of the maximal tangential speed will undergo a similar change. On this basis, the definition of the natural cyclone length of the cyclone separator was presented, i.e. the distance from the lower port of the riser to the location where the quasi free vortex disappears shall be defined as the natural cyclone length Lc of the separator. The result of the formula (5) was given according to the test results. Finally, by analyzing the attenuation characteristics of the swirling flow in the cyclone separator and the energy transfer process between the two vortexes, further explained was the physical meaning of the natural cyclone length of the cyclone separator.