Research On Hydrodynamics Of The Squeeze Film Between Two Plane Annuli With High Rotating Velocity

The squeeze film is widely used in engineering projects, and the related theories and experiments have been the basic problems in fluid lubrication mechanics. The question studied in this thesis comes from the water-lubricated thrust bearings which are used in the nuclear reactor pumps working at very high rotating velocity. The nuclear reactor pump is the key equipment in the nuclear power plant. It is important for the safe of the nuclear power plant that the pumps work stably for a long time. The system of squeeze film bearings is often designed for resisting the load in the axis direction.Water is the lubricating fluid of the bearings in nuclear reactor pumps. Because it has the higher density and lower dynamic viscosity than oil, the inertia effects of the fluid become very important when the bearings work at high rotation velocity. At the same time, the effects of turbulence must be also considered. On the base of a series of hypotheses and the basic functions of fluid mechanics, we got the laminar performance function of the squeeze film including the inertia effects and the analytical solution of the function. With the help of several turbulent lubrication models, we got the turbulence performance function of the squeeze film and then discussed the differences among these models. Furthermore, we researched the influence of boundary conditions and environment parameters on the squeeze film's performances.The results of this research show that:the centrifugal force caused by rotating velocity can decrease performances of the squeeze film by the way of decreasing the effects of squeezing and increasing the radial flow. As long as the rotating velocity is high enough, the film collapse will occur. The turbulence effects which are equal to increasing the fluid viscosity can increase the performances of the squeeze film. At lower rotating velocity, the main factors influencing the performances of the squeeze film are the effects of turbulence, while at higher rotating velocity, the main factors are inertia effects. Both of them determine the relationship of rotating velocity and the performances of squeeze film.A pressure drop, imposed at two sides of the annuli, can improve the squeeze film's performance significantly. Here we define the critical rotating velocity of the squeeze film as the maximum rotating velocity at which the squeeze film could work normally. When we calculate the critical rotating velocity, we not only think about the supporting force, but also consider the distribution of the pressure. Because of the influence of rotating and boundary pressure, the cavitation may happen, which makes the pumps unstable.The performances of the squeeze film can be significantly affected by various environment parameters. Approaching velocity and fluid viscosity can increase the supporting force, while the initial film thickness has the contrary effect.