固定床中错流流动的流场研究

A Study on Hydrodynamics in Fixed Bed with Cross Flow

实验分别测定了气体垂直于单根和两根圆管呈错流流动时固定床内的压力分布,经数学模拟获得床层中流体的压力分布、速度分布及流函数。对于固定床中内置单根圆管,沿主体流动方向的速度分量u在圆管左右两侧离管中心的2.0Dt范围内显著增大,其影响范围一直延伸到床层边缘;而在圆管正前、后方近壁处,由于管的阻挡,u显著下降,约为主体流速的40%,影响范围在1.5Dt左右;随着离开圆管距离的增大,其影响减弱。垂直于主体流动方向的速度分量v,在圆管前后被影响范围约相当于圆管直径,而在圆管左右两侧的影响范围约相当于2.0Dt。影响的深度随雷诺数的增大而增加。对于内置两根圆管的错流流动,沿主体流动方向的速度分量u在圆管前后呈现流速下降、管间流速增大的波形曲线,其波峰和波幅的大小与管间距、离管中心的距离及Rep有关。

The pressure distribution of the fixed-bed embedded a crossed tube or two tubes was measured and the velocity distribution and stream function were got according to the two-dimensional mathematical model simulation. It indicates that the zone of the velocity field affected by tube is near the wall of the tube. For the case of one crossed tube embedded, the velocity component u, along the main gas flow direction, increases remarkably in the range of twice tube diameter in y direction and this effect reaches to the bed boundary. Maximum of u is 1.5 times the bulk gas velocity. Before and after the tube, u descends to 40% of the bulk gas velocity because of the tube hindrance. The distance that velocity u affected by tube is 1.5 times tube diameter in x direction. Far from the tube, the velocity component v, vertical to the main gas flow direction, is zero. Its maximum appears at the close tube wall and is 50% of the bulk gas velocity. The distance that velocity component v affected by the tube is 1.5 times diameter in x direction while it is about twice diameter in y direction. The bigger Reynolds number, the deeper the tube effect on velocity. For the case of two tubes embedded, the velocity component u descends before and after two tubes and increases between two tubes. The curve peak and width have relation to the space between two tubes, distance to tubes center and Reynolds number.