| At present,the leakage channels between the sealing faces are usually converted into a single channel,or the leakage rate is calculated by introducing spoilers.Considering that the size of leakage channels between the sealing interfaces is generally in the micron scale,surface wettability and surface tension are macro-scale.Some factors which are not paid attention to in the flow,because of the large specific surface area,begin to play an important role.By searching domestic and foreign literature and patents,it is found that the influence of surface wettability has not been taken into account in the existing theories and models,which is a new research direction on leakage of contact mechanical seals.Therefore,this paper takes contact mechanical seals as the research object,builds a porous medium model of micro-channel between the ends based on the real point cloud data of the seal ring surface topography.By changing the interaction force between solid and liquid,considering the important role of surface wettability in the flow of micro-channel fluid,simulates the flow characteristics of fluid in the micro-channel,and expounds the surface wettability’s inhibition on leakage.The main research contents and conclusions are as follows:(1)Laser confocal microscopy is used to scan the surface of dynamic and static rings,and based on porous medium theory,a two-dimensional porous medium model between the sealing interfaces is established.The real rough surface of the static and dynamic rings is reconstructed by scanning the three-dimensional surface morphology data of the dynamic and static rings,and the reverse engineering technology is used to simplify the surface of the dynamic rings into a rigid and smooth plane.Ring contact model.(2)The relationship between the load and the porosity of the sealing interface was studied.The contact model of dynamic and static rings is simulated by finite element method.The pressure is applied on the surface of the dynamic rings,and the variation of porosity with end specific pressure is calculated.The results show that the porosity decreases with the increase of end specific pressure.When the end specific pressure exceeds 0.36 MPa,the porosity is stable at about 0.42%.(3)Measuring the plane static contact angle of the static ring surface.The change of surface roughness and contact angle of static ring under different working time,surface position and end load was investigated,and the relationship between the wear degree of mechanical seal surface morphology and its surface wettability was further explored.The results show that for the surface of the static ring,the contact angle of the material surface is about 90 110 without wear;under the same experimental conditions,the contact angle of the inner diameter to the outer diameter of the static ring increases in turn;the worse the wear of the material surface,the bigger the wall contact angle;the rougher the surface morphology of the static ring is,and the more hydrophobic the material is.Compared with the change of contact angle caused by the change of load,the influence of radial position on wettability is more obvious.(4)Discrete velocity model,equilibrium distribution function and particle evolution mechanism in lattice Boltzmann theory are described.Based on the Shan-Chen phase flow model of lattice Boltzmann method,the spreading patterns of droplets on different wettable solid surfaces are simulated by changing the adsorption force of solid wall to fluid,which verifies the effectiveness of Shan-Chen model in simulating surface wettability.(5)Based on the established two-dimensional porous media model between sealed interfaces,the micro-channels with different surface wettability were simulated numerically,and the flow characteristics of fluid in the micro-channels with different wettability were analyzed.It is found that the wall changes from hydrophilicity to hydrophobicity,the velocity of flow at the outlet of microchannel increases,the mass flow of fluid in microchannel increases,and the more hydrophobic the wall is,the more obvious the drag reduction effect is.It can be predicted that the wettability of the leakage microchannel of contact mechanical seal has a significant impact on the leakage rate.The stronger the hydrophobicity of the wall of microchannel,the greater the leakage rate of mechanical seal.The purpose of this paper is to explore the law and mechanism of reducing resistance and increasing leakage or increasing resistance and reducing leakage due to the change of surface wettability,and expound the leakage suppression of contact mechanical seals based on surface wettability modification,so as to provide a theoretical basis for prolonging the service life of contact mechanical seals.Through the research of this project,the contact mechanical seals can form a comprehensive innovative idea in principle design,structure design and engineering application.At the same time,leak prediction and control technology can be derived,which greatly promotes the development of contact mechanical seals.It has important application prospects and theoretical value. |
