Numerical Simulation And Test Verification Of High-parameter Upstream Pumping Mechanical Seal

As a non-contact shaft seal,the upstream pumping mechanical seal can meet the working requirements of zero leakage and zero overflow.It has been widely used in large rotating machinery such as pumps.The thickness of liquid film between sealing end faces is micron.At present,the technical level of upstream pump mechanical seal is mainly applicable to low pressure of 0.3～1.0MPa.However,the instability of the thickness of liquid film will lead to the decrease of sealing performance under high parameter conditions,which puts forward higher requirements for the upstream pump mechanical seal technology to meet a wide range of working conditions.Therefore,it is urgent to design a mechanical seal which is suitable for high parameters and better pumping performance.This paper takes the spiral groove upstream pumping mechanical seal as the research object,and adopts a combination of numerical calculation and experiment to analyze and study the performance of the high parameter spiral groove upstream pumping mechanical seal to obtain the best spiral groove structural parameters.Next,in order to improve the pumping rate,the coupling groove structure of the spiral groove and the micro-cavity is designed on the sealing end surface,and the geometric parameters of micro-cavity are optimized to achieve the best sealing performance.The main research work and conclusions are as follows:Firstly,the fluid state and continuity of the liquid film are judged,and the Reynolds equation is discretized by using the finite difference method and the central difference scheme.Then the corresponding boundary conditions and convergence conditions are set,and the specific expressions and numerical calculation flow chart of sealing performance parameters are given.On the basis of satisfying the axial force balance,use the over-relaxation iterative method to solve and calculate the relevant characteristic parameters of the seal end face.Secondly,the flow field in the micro gap of the high parameter spiral groove upstream pumping mechanical seal is numerically calculated.Taking the pumping rate and friction coefficient as the evaluation indicators,the influence of working condition parameters and structural parameters on the seal lubrication performance is analyzed,and it is found that the influence of working condition parameters is greater than that of structural parameters.At the same time,the variation range of structural parameters(groove depth,ratio of groove length to dam length,spiral angle)of the optimization study is determined.Thirdly,in order to improve the pumping rate and ensure the stable operation of the seal,the micro cavity design and parameter optimization of the mechanical seal face based on dynamic and static lubrication are carried out.By calculating the sealing performance parameters of the groove-cavity coupling structure at different pressures and speeds,and comparing with the performance parameters of the pumping mechanical seal upstream of the spiral groove under the same working conditions,it is obtained that the greater the rotation speed of the groove-cavity coupling end face seal,the greater the pumping rate.It is verified that the coupling groove has a good pumping effect.Through analyzing the influence of working condition parameters and structural parameters on the performance of the groove-cavity coupling mechanical seal,it is found that the influence of working condition parameters is greater than that of structural parameters.After that,by analyzing different microcavity combination structures,the optimal range of microcavity geometric parameters is determined,and the results show that the groove-cavity coupling groove has higher pumping rate and better stability.Finally,the mechanical seal test platform is used to carry out the pumping rate test of the spiral groove upstream pumping mechanical seal,so as to verify the correctness and rationality of the algorithm in this paper.In the test,the test medium is clean water,the rotatic and static ring are made of silicon carbide,and spiral grooves are formed on the surface of the rotatic ring.In order to reduce the influence of temperature changes on the test results,the temperature of the medium is kept constant by controlling the flow of circulating water in the cooling system.After the seal is operating stably,the pumping rate under different inlet pressures is measured;and then the theoretical pumping rate under the corresponding working conditions is calculated.Through comparative analysis,it is found that the calculated value is in good agreement with the measured value,the calculated value is slightly larger than the measured value,and the maximum error is less than 14.3%.The research results of this subject have important theoretical significance for improving the upstream pumping mechanical seal technology,and can provide certain technical support for the subsequent application and development of high-parameter upstream pumping mechanical seal.