Theoretical,Numerical And Experimental Study On Lubrication Of Non-Newtonian Fluid With Separation Flow Method

Although non-Newtonian fluid lubrication has been studied for nearly 50 years, there are still many problems existed in its theoretical solving methods, such as the inappropriate usage of the viscosity and fluid velocity, the complicated calculation process and difficult convergence in programming, etc. In order to solve these problems, a novel non-Newtonian fluid lubrication calculation method based on the continuous fluid mechanics—the Separation Flow Method, is put forward in this thesis.The core of the separation flow method is the treatment of the fluid velocity. The fluid velocity distribution is the key to solve the non-Newtonian fluid lubrication problem, however, the analytical fluid velocity can hardly obtained directly from the constitutive equation of the non-Newtonian fluid for its complex non-linear relationship between the shear strain rate and shear stress. It was found that the non-Newtonian effect of lubricants affected the Poiseuille flow much, while barely had impact on the Couette flow. Then, this thesis calculates the fluid velocity of the Couette flow and the Poiseuille flow separately based on their flow features, and then succeeds in obtaining the analytical velocity and flow rate equation of the non-Newtonian fluid with the usage of the balanced force equation of the arbitrary “control volume” inside the lubricant.The Reynolds equation is the key to solve the non-Newtonian fluid lubrication problems of the separation flow method. Based on the novel flow rate equation of the non-Newtonian fluid and the law of the conservation of mass, the Reynolds equation of general non-Newtonian fluid is derived. And then the temperature rise inside the lubricant has been considered, and the Reynolds equation of the non-Newtonian fluid for thermal lubrication is deduced.Then, the basic equations and numerical calculation methods based on the separation flow method of several non-Newtonian fluid models in hydrodynamic lubrication, EHL and thermal EHL are provided in this thesis. The numerical results show that the separation flow method not only succeeds in the calculation of the pressure, film thickness and temperature rise distribution of the non-Newtonian fluid, but also is a more accurate, simpler method with low computational complexity compared to the other non-Newtonian fluid lubrication methods.At last, some interference figures of lubricants by the ball-on-disc EHL film thickness test rig and the procedure programmed are obtained in this thesis. Then the film thickness distributions under different working conditions have been drawn according to the optical intensity distributions of the interference figures and the revised film thickness calculation equation of the Relative Optical Interference Intensity Technique. The comparisons of the film thickness distribution between the experimental ones and the theoretical ones based on the separation flow method have showed great agreement, which validates the separation flow method again.The separation flow method is a brand new solving method for the non-Newtonian fluid lubrication problems; it is not limited to the non-Newtonian effect of lubricants, and can apply for the viscous non-Newtonian fluid and viscoplastic non-Newtonian fluid lubrication problems. And with the usage of the analytical fluid velocity equation and the Reynolds equation, the separation flow method not only facilitates the calculating process, but also provides more accurate results.