Performance Study And Face Profile Groove Optimization Design Of Hydroynamic-Static Mechanical Seals In Reactor Coolant Pumps

A million-kilowatt PWR plant has about130kinds of pumps. The reactor main coolant pump(RCP) is the heart of the reactor. The main pump seal is the key component mainly used for control the leakage along the pump shaft, which is important to the safty and reliability of the reactor main coolant pump. According to incomplete statistics,40%of the radioactive material leakage accident is due to the seal problem of the valve, and20%was caused by the mechanical seal for reactor main coolant pump. The accident at Three Mile Island nuclear power plant in America was caused by the failure of the mechanical seal, and the financial loss is about700million dollars. At present, the mechanical seals for reactor main coolant pump still depend on import completely, which have the high price and the limited supply quantity. The highest leadership and the related ministries and commissions have attached great importance to the problem. So to research the theory and methods of the design of the mechanical seal for reactor main coolant pumps, to explore the seal mechanism and the synergistic effect theory of each part of the seal, to predict the working mode and rule under the high parameter condition, to have the mechanical seal for high parameter condition with our own patents can solve the nuclear seal problem fundamentally and fill the gap in the fields of nuclear technology, which not only have big significance to the development of the nuclear power industry but also have strategic significance to the social stability and the long-term sustainable development of the national economy.This paper mainly worked on the thermal-fluid-solid coupling analysis and the invention of the new structure and the research of the design theory and the manufacture methods based on the property of the existing structure of the seal and the susceptibility to the thermal elastic deformation under the high parameter condition. The main contents and conclusions are as follows:(1) An3-D steady state heat transfer model and a thermo-elasto-hydrostatic coupling model were established by considering the variation of dynamic viscosity with fluid pressure and temperature, heat transfer between lubrication film and seal rings and the deformation of end faces. The governing equations for fluid film pressure and temperature were numerically solved by using finite difference method, and the thermal-mechanical deformations were simulated by using finite element method based on the program of Matlab. The thermal-fluid-solid coupled analyses were carried and the changes of the face temperature, thermo-elastic deformation and the equilibrium clearance with the surface texture and the effect to the sealing performance were studied.(2) A new type of double tapered hydrostatic mechanical seal was proposed, and the unified definition of face geometry parameter of the mechanical seal was given, and the optimization design face geometry structure was conducted. The comparison of performance of the single and double tapered hydrostatic mechanical seal in the high operation parameters was analysed. The results validated that the double tapered hydrostatic seal has much higher film stiffness and reliability compared with the traditional single tapered mechanical seal, from which we know that seal face with full double tapered structure have higher stability and reliability than partial tapered structure.(3) The performance variation laws of double tapered fluid hydrodynamic mechanical seal in different flow regime has been investigated. The seal temperature distribution field, face liquid film pressure distribution as well as the varying law of face liquid stiffness of double tapered seal in various flow regime were clarified, coupled with double tapered mechanical seal’s sensitivity towards the flow regime and the face inclinational angle. In comparison to the single tapered structure. The rationality of the highly recommended selection of three friction pair matches, ie, SiC-SiC, WC-WC, Al2O3-Al2O3is verified through the investigation of the influence of matching materials in friction pair towards the double tapered mechanical seal performance in different flow regime.(4) The comparision of the influence of the pores with mm scale and urn scale on the seal performance of the laser textured surface mechanical seal was studied. The mechanical seal with big pores was proposed whose advantage was also proved. The new type of mechanical seal with both surface pores and convergent coning was proposed based on the hydrodynamic effect of the big pores and the advantage of hydrostatic and hydrodynamic mechanical seal, which proved that double tapered mechanical seal not only have high opening force and film stiffness but also have excellentg wear resistance. And the best geometrical structure of the new type of mechanical seal for reactor coolant pump.(5) The method of design and manufacture of the taper of the hydrostatic mechanical seal for reactor coolant pumps. Single tapered and double tapered mechanical seal were manufactured successfully and accurately.the pores manufactured successfully with laser etching technology, based on which sample was successfully used to experimental research.(6) The narrow type test device of the mechanical seal for main coolant pump was designed and built. By measuring the temperature, film thickness and the leakage rate, the comprison research of the single tapered mechanical seal and double tapered mechanical seal, the mechanical seal with both surface micropores and convergent coning, the mechanical seal with both surface big pores and convergent coning, the mechanical seal with both surface huge pores and convergent coning was studied, which proved the accuracy of the theoretical prediction and the advancement and reliability of the new type of mechanical seal with both big pores and convergent coning.