| Coolant pump is one of the core equipment of nuclear power system. Shaft-sealed nuclear reactor coolant pump is the key factor to ensure operation of nuclear power plants safely, stabily, reliably. These seal rings are usually made of high hardness materials such as alumina, silicon carbide and tungsten carbide etc, in order to resist high temperature, high pressure and strong corrosion.Because of the complex surface, low surface roughness of rough and high surface accuracy, it is very difficult to ultra-precision manufacture seal ring used in nuclear reactor coolant pump, which lias become a final bottleneck in China’s independent nuclear industry.Aiming at solving the difficult problems of manufacturing the complex shape of seal rings used in reactor coolant pumps with high form accuracy, Based on the pre-deformation plane lapping method of sealing ring used in nuclear reactor coolant pump, a specialized deformation fixture is designed, and the related issues in this method are researched such as precision of pre-deformation, seal performance, and material removal.(1) Model of deformation analysis is built, and a specialized deformation fixture is designed. The effects of geometric parameters of the fixture and pre-deformation force on the end face deformation analyzed. Based on the analysis results of pre-deformation, end surface of seal ring are predicted with the assumption of perfect lapping condition. The results show that: cone-shaped end surface precision of the seal ring by the pre-deformation lapping method is improved by increasing the amount of loading rods. When 9 loading rods are employed, the error of surface profile is less than 0.53 μm It is found that the required wavy surface deformation can be obtained by applying periodic reverse torque. The Equivalent cone angle of end surface is 700 rad and the ratio of wave and cone is 0.94 on the condition of pull rod loading 10.5 N-m and thrust rod loading 9 N·m.(2) The Geometric and physical model of seal system are established. Based on the Reynolds equation, the opening force, contact stiffness and leakage rate of the sealing ring are analyzed. The performance of the sealing ring surface manufactured by pre-deformation lapping method is compared with ideal cone-shaped surface. The results show that:Seal performance of the seal ring with cone-shaped end surface by the pre-deformation lapping method is similar to that of the ideal taper surface. When 9 loading rods are employed, the error of surface profile is less than 0.29 μm, the opening force, leakage rate and contact stiffness of the sealing ring are less than 0.1%,3.5% and 7%, respectively. Seal ring with wavy surface is manufactured by the pre-deformation lapping method.As the load of the thrust rod increases, opening force decreases, leak rate decreases, stiffness of liquid membrane increase firstly and then decrease. As the load of the tension rod increases, opening force increases, leak rate increases, stiffness of liquid membrane decrease slowly.(3) In this paper, the removal characteristics of cemented carbide are researched by plane lapping experiments. The results show that the abrasive size, pressure and rotation speed of lapping plate obviously affect the material removal rate and roughness. The diamond abrasive of 2 μm is suggested to be used to lap the cemented carbide, and the rotation speed of lapping plate is 30 r/min. The material removal rate and the roughness are 2.27 μm/min and 21.3 nm respectively. Surface deformation of seal ring are obtained under the force of pre-deformation fixture. Using the above process parameters, seal ring is successfully manufactured. The possibility of the manufacturing of seal ring which used in nuclear reactor coolant pump using the pre-deformation plane lapping method is verified... |
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