三维平行微间隙流场数值模拟

为了研究上游泵送机械密封微间隙流体动压效应，将螺旋槽端面微间隙简化为三维直槽端面平行微间隙以排除泵送效应的影响.据此，建立了平底槽、渐扩台阶槽和渐缩台阶槽的平行微间隙液膜几何模型和计算模型，分别在槽板移动和平板移动的情况下针对不同移动速度和不同槽深进行流场数值模拟和开启力计算研究.研究表明：在文中研究参数范围内，无论是平底槽还是台阶槽，液膜收敛区出现高压，液膜发散区出现低压；液膜空化前，无论是槽板移动还是平板移动，平底槽微间隙开启力大小与平移速度、槽深、板间隙大小无关；液膜空化后，平底槽和台阶槽液膜开启力均随平移速度的增大或板间隙的减小而明显增大，但在同等条件下，槽板平移产生的开启力大于平板平移，且槽板平移时加大槽深能增大开启力，渐扩台阶槽平行微间隙能产生更大的开启力.

Numerical simulation of flow in 3D parallel micro gap

The dynamic pressure effect in upstream pumping mechanical seals was studied by using a flow in the 3D parallel micro gap to remove the pumping effect. Three kinds of geometrical and computational models, namely the groove with constant depth bottom, the groove with backward sloping bottom and the groove with forward sloping bottom, were established, respectively; the flow and opening force in those models were calculated by using numerical simulation method when one ring was in motion and one was stationary. The results indicate that there is a high pressure zone in the liquid film thickening zone, and a low pressure zone in the film thinning zone regardless of the bottom shape of a groove in the specified range of parameters. For the groove with constant depth, the opening force is independent on the seal ring moving speed, the groove depth and the gap of the seal when either the flat ring or the grooved ring is in motion before cavitation occurs in the liquid film. After cavitation, however, the opening force significantly increases with increasing translational speed and decreasing gap of the seals. At the same condition, the opening force generated by the moving grooved ring is larger than that by the moving flat one. In addition, deeper groove depth of moving flat ring can increase the opening force and diverging step in the gap will generate further larger result.