| The Reactor Coolant Pump of the third generation nuclear power technology is gradually applied in China. The self-independence research and development of Reactor Coolant Pump becomes the key issue in the development of nuclear power in our country at present. In this study, incompressible fluid seal characteristic was studied for effective and safety seal.In the pressurized water reactor nuclear power plant, nuclear main pump is an important rotating equipment, it is called "heart". Its reliable and efficient operation is the guarantee of the safe operation of the plant. There is a gap between impeller cover and stationary components in Reactor Coolant Pump. If the leakage along the front surface of the impeller is out of control, it will flow back through the clearance and disturb the main flow at the inlet of the impeller. It will lead to a decrease of the hydraulic efficiency of Reactor Coolant Pump. Once the pump operates on a low hydraulic head due to the larger leakage, there will be a serious danger of water coolant undersupply, which leads to excess reactor core temperature. Therefore, designing an appropriate seal to control leakage to guarantee the stable operation of Reactor Coolant Pump, becomes a key subject. Additional stiffness, damping and mass are provided by sealing fluid. Dynamic characteristic of sealing structure is a guarantee to stable operation of impeller. A design of effective and safety hydraulic seal becomes a key topic in the study of Reactor Coolant Pump hydraulic components.Firstly, influence of numerical method and turbulence models on the incompressible flow seal simulation was investigated, respectively from two aspects of flow field and dynamic characteristic. Analysis of advantages and disadvantages of the numerical method and turbulence model were studied, by comparison with experiment results. The reliability of the method in this paper was validated.Secondly, in this study, the calculation method in the mixed-flow pump axial thrust was discussed. Pressure distribution in the clearance between impeller cover and stationary components was changed due to the ring seal installation. Then the axial thrust of impeller was changed correspondingly. The influence of the clearance on the axial thrust was investigated. The formula derivation and computational fluid dynamics calculation method in the axial thrust were discussed. And it could be concluded that the axial force increased with clearance.Thirdly, incompressible fluid sealing characteristic was the main research content of this study. It was divided into two research routes:leakage characteristics and dynamic characteristics. This study built relationship between the dynamic characteristics and fluid parameters (pressure and velocity). Using polar coordinates transformation method of flow field parameters, it was predicted that long ring seal and the whirling clearance flow along the front surface of the impeller were easy to produce negative direct stiffness and higher cross stiffness value in high rotating speed. It might cause the impeller whirling unstability. And the grooved seal with positive direct stiffness and smaller cross stiffness was more stable than the smooth ring. But the direct stiffness of grooved seal was small, and it might not provide enough elastic support for the impeller. The helically grooved seal with negative cross stiffness restrained the whirling effect of impeller. Its higher direct stiffness could provide elastic support for the impeller, especially arc wedge grooved seal further improved the direct stiffness.In terms of leakage characteristics, the friction factor was used as a leakage characteristic parameter in this study. The influence of the geometric shape on the friction factor of rectangle grooved seal was studied in the Reactor Coolant Pump. Then the seal with a high flow resistance was found. In addition, the pumping effect of helically grooved seal improved the friction factor. For all helically grooved stators in this study,20deg and30deg stators had higher resistance to leakage than the circumferential grooved stator. It indicated that the helically grooved seal had high efficiency in Reactor Coolant Pump. New type helically grooved seal including arc wedge grooved seal and helical seal with double tip teeth further improved flow resistance, and the latter’s sealing ability was improved to the triple of helically rectangular grooved seal. In this paper, three new seal designs had obtained two national invention patent authorizations and a utility model patent authorization.Finally, the influence of the new design concepts on the energy dissipation and dynamic characteristics of the incompressible fluid seal was investigated. The design scheme and advantage of new type seal were discussed. The new type hydraulic seal will be used to control the leakage under the condition of large flow rate and high pressure in Reactor Coolant Pump. |
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