| Lubrication system is an essential part of transmission system. The property of lubricating oil has a very important influence on the lubricating property. Air is inevitably entrained and beaten into lubricating oil as it passes around the system. The bubble in the oil will change oil’s property, such as compressibility and viscosity, which will affect the lubricating property. Thus, it is very important and necessary to study the characteristics of bubbles and the rheology of oil gas two phase flow. This paper demonstrates the evolution of bubbles, the bubble size distribution, bubble deformation and the rheology of oil-gas two phase flow.Firstly, a set of differential equations describing the dynamic process of bubble evolution are established based on Rayleigh-Plesset equation when gas diffusion is under consideration.A univariate cubic equation that indicates the relations of bubble radius and liquid pressure is established based on the force balance of bubble surface. Then the univariate cubic equation is solved analytically based on Cardano formula.The analytical solution is achieved. Another analytical solution is achieved when gas diffusion is under consideration.An experimental device is bilut to measure the radius of bubble under different liquid pressure.The analytical solutions are verfied by the experimental result. The bubble size distribution with different air voids is measured, and a probability density function is achieved. It is shown that bubble size distribution conforms to logarithmic normal distribution. The air voids has little influence on bubble size distribution and mean radius. The relations between air voids and liquid pressure arealso studied based the previous analytical solutions.The deformation of bubbles in shear flow field and the influences of distorted bubbles on rheology are studied by using hydrodynamics. The deformation of bubbles is dominated by capillary number, which is denoted as ration of shear force and surface tensor. When the capillary is small, the amount of bubble deformation approximate to capillary. When the capillary is large, the amount of bubble deformation is exponential function of capillary number. The viscosity of oil-gas two phase flow reachs a steady value after decreasing with the increasing of capillary number. |
