SK型静态混合器湍流速度脉动特性

Characteristics of pulse velocity of turbulence in a SK-static mixer

以SK型静态混合器为研究对象,运用激光多普勒测速仪对管内的速度脉动进行测量。结果表明:湍流时在第1个元件内的轴向速度脉动较小,进入第2个混合元件后轴向脉动均方根可达平均流速的0.5—0.7倍且基本达到稳态;每个元件的入口有1个均方根可达到0.8—1.0倍平均流速的轴向速度脉动尖峰;流体离开混合元件后,各个方向上的速度脉动都迅速衰减,经过1个混合元件长度后脉动速度均方根衰减到平均流速的0.3倍左右,流过4—5个混合元件长度后基本衰减到混合器入口处的速度脉动水平。

The pulse velocity in a SK-static mixer was measured by Laser Doppler Velocimetry （LDV）. The results show that the pulsation of axial velocity is lower in the first element; however, the root mean square （RMS） of axial pulse velocity can be 0.5-0.7 times as large as the value of the average velocity and basically approach a steady state in the second element. The peak of the RMS of axial pulse velocity can be 0.8-1.0 times as large as the value of the average velocity and occurs at the entrance of each element. The pulsation of the three-dimensional velocity sharply attenuates when the fluid leaves the last element of mixer; the RMS of the axial pulse velocity attenuates to 0.3 times as large as the value of the average velocity in the position of an element length from the exit and in the position of 4-5 elements length from the exit. It is almost as the same as that of the entrance of the mixer.