Theoretical Research On Thermo-Elasto-Hydrodynamic Effects Of Hydrostatic Mechanical Seals In Reactor Coolant Pumps

A hydrostatic mechanical face seal is basically composed of a rotator and a stator, separated by a thin fluid film. When it is mainly used as the primary seal in a reactor coolant pump, which is operated at high pressure, high speed and over a wide range of temperatures,it may be subjected to face deformation. So the performances of such a seal, which mainly refer to stability, sealing ability and the ability of follow runout, will be obviously affected by the thermo-elastic deformation and the changes of sealed medium properties. In this thesis, the effects of thermo-elasto-hydrodynamic (TEHD) lubrication on sealing performance are studied for a coned-face hydrostatic mechanical seal. The results should be used for the geometric design of such a seal in theory. The works and the results in this thesis are as fllows:First of all, a three-dimensional heat transfer model of such a hydrostatic mechanical seal is established, with the misalignment of the stator considered. In which the variation of dynamic viscosity to fluid pressure and temperature changes are considered. The controlling equations for sealing fluid film pressure, energy balance and heat transfer in rings and fluid film were set up and numerically solved by using finite difference method.Secondly, without considering the effects of face deformations, the performance of such a seal and the distributions of the temperature and pressure of the seal were studied for the different geometric parameters and by varying operation conditions.At last, with both the thermal and the mechanical face deformations considered, the effect of boundary conditions on both face deformations is analyzed by using finite element method. A steady-state of heat transfer model of such a seal with convergence step gap was established. The coupling analyses of the sealed film, the sealing rings and the thermal distortions are performed. The effects of thermo-elastic deformation and operating conditions on the sealing performance of such seal were studied.The results showed that when a coned-face hydrostatic mechanical seal operates, the elastic deformation caused by pressure is greater than the thermal deformation caused by temperature rises, both of them result in obvious effects on the performance of suach a seal. The thermo- elastic deformation will result in a strong convergence gap from outer radius to inner radius, leading to the increase of opening force, leakage and film stiffness. The thermo-elastic deformation, the balancing thickness of the fluid film and the performance of the seal will be obviously effected by operating conditions.