Analysis And Optimization Of Screw Seal Capability And Its Structure Design

The sealing devices, the indispensable part of the modern machinery, are to protect the oil, water or gas from leaking out, and the impurities or dust from invading inside of the equipment. The seal plays a very important role in improving the efficiency, reliability, safety and working life, and saving materials and energy. According to statistics, almost 40-50 percent of workload is consumed in the maintenance of shaft seal. How to seal the machinery has been a problem to be solved urgently.In this article, the screw seal, a kind of non-contacting motive seal, is put forward. The main structure and principle of screw seal is introduced, and the screw seal is a combination of negative seal and positive one. Based on the principle of the screw seal, the region division of sealing part has been obtained. Considering the pressure distribution and working medium leakage, the sealing part has been mainly divided into 2 parts, and the velocity and volume flow in which have been calculated. Referring to the theory of volume flow balance, the new practical calculation formula of screw seal capability has been established. The optimal parameters of the screw seal structure has been achieved by using MATLB. The simulation of CFD is carried out, in which the practicability of the calculation formula and optimal parameters has been verified. At the same time, the common phenomenon appearing in the screw seal, such as gas swallowing, seal failure and stop seal, are discussed. Based on that, the structure of the screw seal is designed.The results clearly show that there are two leakage regions, namely the axial leakage along annular clearance between tooth tip and hole and leakage along the spiral groove. When the leakage volume flow and the pumping one come to a dynamic balance, the medium can be sealed successfully. The screw seal can achieve the maximum capability, when the ratio of tooth width and groove one, of clearance and groove depth is 1.0 and 2.61 respectively, and the screw angle is 15.6°. This article put forward a new seal screw device, which mainly contains the double seal screw unit and stop seal functioning in the state of stop or low speed rotation.