Research On Friction Characteristics And Sealing Performance Of Textured End Face Seals In Internal Mixers

The internal mixer is the main equipment for producing mixed rubber.To prevent the leakage of rubber,the rotor shaft must be equipped with an end face sealing device.To improve the sealing performance of the end face seal of the internal mixer,reduce wear and prolong its service life,the surface texture technology was introduced to the end face seal,and the effects of different texture parameters as well as working condition parameters on the textured end face seal were studied in this paper.The effects of friction characteristics and sealing performance were investigated and multi-objective optimization was carried out based on the meta-model.The main research contents are as follows:(1)In this paper,based on the theory of hydrodynamic lubrication,a theoretical model of the textured end face seal of different shapes of internal mixers was established,and the effects of different texture parameters and working parameters on the friction characteristics and sealing performance of textured face seals under steady-state conditions were analyzed.The research results show that the textured end face seal can obtain a certain bearing capacity.When the texture depth is 4?6?m,the Circle texture,Ellipse texture,Ellipse?texture,Triangle texture,Triangle?texture,and Square texture surface can obtain optimal friction performance and better sealing performance.Increasing the area ratio can enhance the hydrodynamic pressure effect,and improve the bearing capacity and oil film stiffness,but it will increase the leakage.When the texture area ratio S_p=18%?21%,Ellipse texture and Triangle texture can obtain the best friction performance and better sealing performance;when the area ratio S_p=31%?35%,the other four textures obtain the best friction performance and better sealing performance.When the sealing gap is increased,the friction coefficient,average dimensionless pressure and oil film stiffness all decrease first and then become stable;if the seal gap h₀ exceeds 5?m,the textures and the matching seal ring no longer produce hydrodynamic pressure effects,and the textures only plays the role of storing lubricating oil.When the rotor speed and lubricating oil viscosity increases,each performance index will increase which indicates that the viscosity and rotational speed can be appropriately increased so that the textured end face seal can obtain better performance(2)The research on the influence of the interaction between textures shows that the interaction between textures can promote the effect of hydrodynamic pressure on the sealing surface;the leakage is most significantly affected by the interaction between the textures perpendicular to the flow direction of the lubricating medium;the interaction between the textures helps to enhance the ability of the oil film between the seal faces to resist slight external disturbances.(3)The DACE-Kriging method was used to build the textured end face seal meta-model of the internal mixer,and the MOGA-?algorithm was used to optimize the Triangle?and Ellipse?textured end face seals,respectively.The optimization results show that the meta-model based on the DACE-Kriging method has high reliability;the optimal values of Triangle?and Ellipse?texture end seals are Q=0.784mm~3/s,?=0.062,P_av=4.15,and Q=0.421mm~3/s,?=0.063,P_av=3.84,respectively.The parameters obtained after the end face seal optimization were brought into the numerical program,the optimization design results of each optimization target are relatively close to the numerical solution results,and the relative errors do not exceed 12%,indicating that the optimization process is positive for improving the performance of textured face seals.(4)Based on the steady-state theoretical model,the effects of periodic loads and step loads on the textured end face seal of the internal mixer were considered,and a theoretical model of the unsteady internal mixer textured end face seal was established by considering the extrusion term.The results show that under periodic load,the maximum oil film pressure increases,and the seal gap and leakage increase as the load decreases,and vice versa;the Ellipse?textured end seal has the best overall sealing performance under periodic load,the effect of lubricant viscosity on the maximum oil film pressure is not significant,and the leakage of each shape of textured sealing surface increases with the increase of lubricant viscosity.Under periodic load,the parameters fluctuate greatly when the rotor speed is low,the higher the speed,the better the stability of the oil film and the sealing performance.Under the action of step load,all the performance indexes changed suddenly,and the step load would obviously enhance the extrusion effect between the two sealing surfaces,which would have a significant impact on the textured end face seal.(5)During the pin-disk test of the TRB~3 friction and wear testing machine,the friction coefficients of different textured surfaces were collected,and the surface of the specimen before and after the test was observed with a three-dimensional topography instrument.The test results showed that when the texture depth increases,the average friction coefficient of the two textures first decreases and then increases;when the texture depth is 6?m,the friction coefficient of the Triangle?texture is the lowest;when the texture depth is 9?m,the friction coefficient of the Triangle?texture is the lowest;compared with the untextured surface,the average friction coefficients of Triangle?texture and Ellipse?texture are reduced by 6.7%?35.23%and5.75%?27.94%,respectively.Under the same texture area ratio,the average friction coefficient of Ellipse?texture is larger than that of Triangle?texture as a whole.Triangle?texture can obtain better tribological properties under the same area ratio.