迷宫密封湍流增阻的数值研究

Numerical study on resistance enhancement of labyrinth seal by turbulence

迷宫密封是依靠节流间隙中的节流过程和迷宫空腔内的动能耗散过程来实现密封的,这两个流体流动过程从本质上规定了迷宫密封的密封性能。通过密封内部流动本质的研究,合理利用湍流流动的规律和特点,能够发挥密封内部湍流的增阻作用,提高密封性能。本文数值计算了一种锯齿型径向迷宫密封的内部流动,得到了密封内部的流动形态,揭示了密封内部流动与密封性能的关系。结果表示,密封存在一个最佳的齿插入长度。在最佳齿插入长度时,尽管节流间隙较大,但由于节流间隙内流动收缩和偏转,间隙的有效通流面积却很小,泄漏介质可以在间隙中获得较大的速度,在迷宫空腔内形成正确的耗散涡流,密封具有最佳的密封效果。所以,充分发挥湍流增阻的作用,可以突破节流间隙的微小尺寸限制,实现较大间隙下的良好密封。这不仅会给迷宫密封的制造、安装及运行等带来很大的方便,而且可以为发展新的迷宫密封技术奠定理论基础。

The property of labyrinth seal relies on the throttling process in the clearances and the kinetic dissipation process in the cavities just behind the clearance, these two procedures play decisive roles in essential to the sealing property of the labyrinth. Study on the internal flow pattern of labyrinth seal is helpful for us to make use of some characters of turbulence in improving the sealing property. In the present paper, the flow field in a crenellated radial labyrinth seal is numerically studied, the flow pattern is obtained, and the relationships between the turbulent flow in the seal and the sealing properties are revealed. The numerical results show that there is an optimal teeth insert length for the sealing property. Under the condition of the optimal teeth insert length, although the throttling clearance is large, the inertial deflection and contraction of the jet flow through the clearance decreases the effective flow area of the clearance, thus the discharge medium can obtain higher velocity in the clearance and proper dissipating vortex can be formed in the cavity, so the seal reaches the best sealing property. We can conclude that by making use of the resistance enhancement by turbulence, better sealing property can be achieved under the condition of large clearance, which is of great importance to the design, manufacture and operation of labyrinth seal, and lays the theoretical foundations for new labyrinth seal techniques.