Research On The Properties Of Water-lubricated Thrust Bearing And Mechanical Seal Used In A Nuclear Pump

Nuclear pump, called as the "heart" of the nuclear power station, is the key equipment of the first circuit within the reactor. Its main function is to deliver the coolant and discharge the heat generated by the power. For the nuclear pump, it is necessary to provide the motor with sufficient high load support and low friction using the tilting-pad thrust bearing and the mechanical seal, the most two important parts. Therefore, the safety and running efficiency of the nuclear pump are dramatically influenced by the properties of the thrust bearing and the mechanical se.al. Moreover, the thrust bearing and the end seal face are two relative damageable parts, the maintenance period of the nuclear pump are determined by the service life of the above two parts. In order to endow the nuclear pump with high safety, high running efficiency and low running cost, the properties of the thrust bearing and the mechanical seal should be examined in detail by numerical simulations.For the new generation nuclear pump, the lubricant of the thrust bearing and the mechanical seal is usually water. Compared with the traditional lubricant, oil, water possesses some of the following advantages:abundant source, low cost, low environment pollution and can’t be easily influenced by nuclear radiation. However, water possesses a very low dynamic viscosity. On one hand, a low dynamic can give the thrust bearing and mechanical seal low friction and low energy consumption, on the other hand, the low dynamic viscosity reduces the low load support capacity, which can result in a water film collapse, especially when the design of the bearing and seal is not optimized. Moreover, the low dynamic viscosity usually makes the water film be in turbulence. Obviously, the turbulence should be considered and the numerical simulation would be difficult to carry out. Unfortunately, in order to protect the economic interests, the foreign manufacturers hardly publish their research on the thrust bearing and the mechanical seal used in nuclear pump. In our country, few researches of the thrust bearing and the mechanical seal used in the nuclear pump are published, too. In this thesis, the water-lubricated tilting pad thrust bearing and the mechanical seal are studied by numerical simulation.There are four chapters in this dissertation, and the work mainly covers the following aspects: In chapter1, the development course and application field of the water-lubricated thrust bearing and the mechanical seal in nuclear pump are introduced briefly.In chapter2, the theory of a water-lubricated thrust bearing is introduced briefly. The lubrication equation is established, and then it is modified in a dimensionless form.In chapter3, the water-lubricated tilting-pad thrust bearing is analysed by detail numerical simulation. The influence of the rotation speed and the position of supporting point on the properties of the bearing is analysed. It was found that the supporting point can affect the properties and the inertia force can’t be simply ignored under the condition of heavy loading and high speed.In chapter4, a briefly introduction of the theoretical of mechanical seal is made at first. We examine the parameters of seal groove on the properties of an mechanical seal. Finally, we give a design rule of the sealing ring according to the important parameters such as opening force, leakage and film stiffness which measuring the sealing performance.