Study On Steady Character Of Liquid Film Seals With Non-Newtonian Lubricant Considering Boundary Slip

With the development of technology,the working conditions of mechanical sealing system have been greatly changed.More and more extreme conditions are taken account,such as heavy load,high pressure,high speed,unstable condition and so on.The non-Newtonian characteristics of fluid and the boundary slip have important influence on the steady performances of liquid film seals.Therefore,in order to more accurately study and predict the performance of liquid film seals,taking spiral groove liquid film seals as object,the influence of non-Newtonian characteristics and boundary slip on sealing performance were analyzed.A mathematical model of spiral groove liquid film seals considering non-Newtonian characteristics of fluid and boundary slip was established based on power law model and Navier model,as well as JFO model.The rheology test was carried out by the rotary viscometer,and the power law index of the lubricating oil was measured.The accuracy of the program was verified by the contrast of the cavitation area and the leakage test.And the influence of multiple factors such as operating parameters,structural parameters,film thickness and property parameters of lubricating oil on steady character of liquid film seals were studied.Moreover,based on the generalized Reynolds equation considering boundary slip,the influence of boundary slip on steady character of liquid film seals were studied under four slip states.Besides,in order to improve the load-carrying capacity and reduce the cavitation rate,a surface micro texture and spiral groove combined type liquid film seal structure is put forward.Finally,the method of combining BP neural network with genetic algorithm was used to optimize the seal structure and the experimental research was carried out.The research results show that: the smaller power law index can help to improve the loadcarrying capacity and reduce the cavitation rate;under the larger power law index,the cavitation on the seal face is serious,and the load-carrying capacity of the liquid film is weakened;the reasonable selection of lubricant is important to improve the sealing performances of liquid film seals;the existence of slip is beneficial for the steady character of liquid film seals under single wall with boundary slip and single combined wall with boundary slip;under double wall with boundary slip and double combined wall with boundary slip,the load-carrying carrying capacity decreases with the existence of boundary slip;when operating parameters were changed,the sealing performance parameters under four slip states shows similar trend;the structure of surface micro texture and spiral groove combined can improve load-carrying capacity and film stiffness of liquid film seals,while reduce friction torque,which has better sealing performance;the liquid film seals perform better with parameters showed in the paper: groove depth should be 20?m,the number of groove is 40,spiral groove angle is 20°,ratio of groove to ridge width is 1.5,ratio of groove to dam width is 1.5.