Research On The Thermal-Fluid-Solid Coupling Characteristic And Performance Of The Wavy Endface Hydrodynamic Mechanical Seal For Reactor Coolant Pump

Wavy endface hydrodynamic mechanical seals are key components of nuclear coolant pumps,which are used to avoid the leakage of high-pressure,high-temperature and radiative fluid.The design method and related products are monopolized by the abroad company.To master the design and manufature technology of the wavy endface hydrodynamic mechanical seals,this dissertation carries out the design development of the wavy endface hydrodynamic mechanical seal for reactor coolant pump.Taking the wavy endface hydrodynamic mechanical seal as the research object,considering the cavitation effect of the liquid film,a theoretical model of seal is established,and the influence of the operating parameters on the sealing performance under the constant and non-constant conditions of the liquid film thickness were studied.The operation mechanism of the wavy endface seal was revealed.Considering the influence of the pressure and temperature of the sealing medium on the deformation of the sealing ring,a thermal-fluid-solid coupling model was established,and the physical model was solved by the finite element method.The influence of operating parameters and geometric parameters on the deformation and sealing performance of the seal ring was studied.The precise forming process method and checking method of the complex wavy of the sealing endface are proposed,and the performance tests of the manufactured sealing rings with different waviness numbers and waviness amplitudes under different pressure and temperature conditions were carried out.The main research achievements are given in the following.(1)The sealing performance,the evolution of low-pressure cavitation and the effect of rotational speed on the sealing performance were obtained under the constant lubricating film thickness,and the balance ratio(B=0.7)and balance diameter(d_b=287.6mm)of the seal were determined.When the axial force of the seal ring is balanced,the effect of temperature on the sealing performance can be neglected,and the pressure,waviness number,waviness amplitude and speed have a significant effect on the sealing performance and hydrodynamic and hydrostatic effect of the mechanical seal.(2)Under the effect of heat,fluid and solid coupling,the thermal-mechanical deformation of the sealing endface increases the degree of convergence of the lubricating liquid film in the sealing gap,the hydrodynamic effect of the lubricating liquid film is weakened,and the hydrostatic effect is increased.Operating conditions and endface structure forms are analyzed for the rationality of the structural design,so as to control the thermal-force deformation effectively.Within the research scope,it is more appropriate to select the wave number k=9～12 and the waviness amplitude h_a=5～6.7μm in order to meet the requirements on the leakage rate for the reactor coolant pump in the nuclear power plant.(3)Aiming at the problem of high-precision grinding and forming of the stator wavy endface and the the sealing surface of other sealing rings(such as the rotor,rotating base ring,stationary base ring),a grinding manufacturing and testing process is proposed.The special manufacturing and checking tools are designed to achieve the high-efficiency precision forming of the sealing endface,obtain high quality sealing surface,and meet the expected design requirements.(4)The calibration method of the pressure reducing throttle tube of the mechanical seal system is proposed,and there is a difference between the actual calibrated tube length and the theoretical tube length,which shows that the throttle tube should be calibrated before it can be applied.The test results of the mechanical seal show that there is no phenomenon such as the seal ring locking,overleakage and face wear during the process of boosting and depressurizing process,which proves the operation stability of the mechanical seal with the wavy endface.The mechanical seals with nine waviness numbers(h_a=6.3μm)developed in this paper are installed in the 3#reactor coolant pump of Fuqing Nuclear Power Station.It is operating well and no any leakage over alarm occurs until now.This verifies the good applicability of the designed and processed mechanical seal in the field of the nuclear power plant.In conclusion,in order to realize the design and engineering development of the wavy endface hydrodynamic mechanical seal for reactor coolant pump,a thermal-fluid-solid coupling mathematical model of the mechanical seal and a numerical solution method based on the combination of the finite element method and the numerical iterative method are developed in this paper,and the thermal-stress deformation coupling mechanism of the wavy endface seal is revealed.The structural parameter ranges of the seal that meets the requirements of the leakage rate of the shaft seal operation for reactor coolant pump is obtained.A complete set of the seal endface manufacturing and forming process and checking method with independent intellectual property rights is proposed.The problem of localization of the mechanical seal for the reactor coolant pump is solved and the seal manufacturing technology level and competitiveness in the international nuclear power market is improved.