| This paper is based on the funded projects of Jiangsu Province Technology Support Program (Industry part) (BE2010156), Jiangsu Province Postgraduate Research and Innovation Program (CX08B-0632) and Zhenjiang City Industrial Research Programs (GY2008002)Centrifugal charging pump is an important part of the chemical and volume control system (RCV) of the nuclear power plant primary circuit, it is one of the most crucial nuclear power equipment, with less difficult only than the main pump of the nuclear safety gradeⅡequipments. Centrifugal charging pump is a horizontal, double shell, tube-like multi-stage centrifugal pump with small flow rate, high head, high speed, high cavitation requirements, and large matching characteristics motor power. The nuclear power specifications of the pump must meet five high-precision operating points, with thermal shock and seismic requirements, which makes its technical highly difficulties. The centrifugal charge pumps of 1000MW nuclear power plant currently are all imported, domestic application is still blank. The industry analysis of constraints on the localization of charge pump is hydraulic model which is the biggest challenge. In addition, the charge pump structure design, thermal shock, seismic performance and reliability of rotor torsional vibration of structures are also the crucial factors which constraint the charge pump to be manufactured.This paper is based on the centrifugal charging pump hydraulic model development, numerical simulation of hydraulic performance, four-stage hydraulic model and cavitation performance of the prototype testing, rotor dynamic torsional vibration calculation, calculation of thermal coupling, seismic, and many other studies, which aimed at the solution of the constraints on the localization of charge pump hydraulic design and structural reliability of the technical problems and the preparation for centrifugal charging pump theoretical basis for localization. In this paper, the main research and creative achievements are:1. Comprehensive and systematic analysis of the domestic and overseas double-shell multi-stage high pressure centrifugal pump research progress, introduction of the charge pump important role of 1000MW nuclear power station, the design of centrifugal charging pump in the hydraulic performance and the special structure design requirements are given. On this basis, thorough analysis of charging pump for the hydraulic design, structural design, rotor system critical speed calculation, calculation of thermal coupling, seismic and other related theoretical development for a more in-depth analysis, and finally a charging pump structure design are given.2. The comparative study of the 8 designs internal flow field numerical simulation of steady flow of charging pump suction chamber was carried out. Use RANS Reynolds averaged equations for numerical calculation, the RNG k-s turbulence model to close the Reynolds stress term, the application for incompressible flow SIMPLEC algorithm to solve the pressure field, the 8 designs flow fields three-dimensional viscous turbulent flow in the impeller were numerically simulated. Through eight kinds of internal flow velocity, pressure, turbulent kinetic energy distribution of comparative analysis of the design flow condition and off-design conditions of water flow, we could find that:the larger suction chamber inlet can reduce water loss, but the annular space using arc-shape and structure of straight have little effect on the hydraulic calculation. The results show that a good straight annular space even has smaller losses than the radial structure of hydraulic. The analysis and assessment of eight kinds suction chamber provids a theoretical basis for the charging pump primary impeller optimization design.3.The charging pump is designed using multistage centrifugal pump multiple working conditions hydraulic design method, taking numerical simulation and comparative study on steady flows and unsteady flows of first impeller and subprime impeller. First impeller and subprime impeller are designed with eight types of design scheme. Results show that the cavitation performance of the first impeller is affected largely by the geometry parameters of impeller, in addition, inlet velocity and pressure distribution along with circular of diffuser are the cyclical fluctuations, and jet flow and wake flow of impeller outlet existence or not and its position have a close relation with pump flow and impeller structure forms, which further confirmed the charging pump asymmetric flow characteristics of the flow field from impeller to diffuser. Through the different design schemes and different flow conditions of numerical simulation analysis, the rotor-stator interaction influence on fluid field between impeller and diffuser is revealed. Based on numerical simulation of multiple design flow conditions, the centrifugal pump performance curve was predicted. As for the charging pump, hydraulic performance must meet the requirements of multiple working points, while conventional hydraulic design method can't meet the design requirements, so multiple working hydraulic design method is very well solving the problem, which provides a new way for the charging pump hydraulic design.4.To validate the charging pump hydraulic design, the four stage prototype of charging pump was manufactured. Through the charging pump prototype experiment, we obtained the characteristics of hydraulic performance and the cavitation performance. By comparision the curves of experiment with the curves of numerical analysis, which verified the correctness of charging pump hydraulic design, the accuracy of numerical simulation and the feasibility of performance prediction. Comparing the test results of four stage prototype of charging pump after similar conversion with required performance parameters, it showed that the requirements of the five working points in hydraulic performance is achieved, and the maximum deviation appears in maximum flow condition, at 4.7%. The speed of the four stage prototype is increased to 4500r/min using the pulley, for the cavitation performance test, and the result showed that the cavitation performance meet the design requirements. On this basis, the numerical calculation of the hydraulic properties of twelve stage charging pump was carried out.5.For the first time the rotor system of charging pump critical speed was analysed. Several factors are analyzed for the influence of the natural frequency (transformed into critical speed) of charging pump rotor, then summing up the influence of various conditions, and finally the rotor critical speed was calculated. After the calculation, it was found that in the elastic supporting the first-order natural frequency is 253.405 Hz, namely 15204.3 r/min, while the actual rated speed of charging pump is 4,500 r/min, so results showed that the structural dynamics design of charging pump meets the design requirements. Additionally, the supporting stiffness of the rotor affects the rotor system critical speed largely, so accurately simplifing supporting, reasonably determining the supporting stiffness and damping matrix are the essential premise for the calculation of critical speed.6. For the first time, through the pressure analysis, transient thermal analysis, thermal stress analysis and the indirect coupling analysis of the shell of charging pump, stress assessment results of the stress superposition method and the indirect coupling method are given. The maximum pressure intensity occurs in the inner wall of the outer shell end node 1849, and the total stress intensity is 42.91 MPa. The total stress intensity of indirect coupling method also occurred outside the inner wall of the shell end node 1849, the total stress intensity is 42.83 MPa. Stress superposition method and the indirect coupling method on the PL+Pb+Q≤3Sm consistent with the assessment results.7. For the first time, the seismic analysis of charging pump is studied. Through ANSYS software for the domestic PWR (pressurized-water reactor) nuclear power plant with double-hulled centrifugal charging pump housing, three-dimensional finite element model of charging pump is established, natural frequencies and vibration pattern are obtained, and seismic performance analysis of the charging pump under the OBE and SSE seismic loads were calculated and given, the results show that:(1) In modal analysis, the fundamental frequency of charging pump is the 655.138 Hz, and it is much larger than 33 Hz, which shows that charging pump owns rigid structure. In addition, the first-order vibration mode is in the horizontal direction, indicating that the displacement response under earthquake is mainly in horizontal direction. Then the consideration of increasing the intensity of the horizontal charge pump in the design stage can be a effective way to reduce seismic impact on the charging pump. (2) Under the OBE seismic loads, weight, and high temperature simultaneously, the maximum stress response of the charging pump is in the central positation of the outer shell,and the maximum stress is 69.13 MPa. The stress calculated by the third strength theory, is under the allowable values, which meets the Secondary Parts Requirements of nuclear power plants; Under the SSE seismic loads, weight, and high temperature simultaneously, the maximum stress response of the charging pump is in the central positation of the outer shell, and the maximum stress is 103.47 MPa. The stress calculated by the third strength theory, is under the allowable values, which meets the Secondary Parts Requirements of nuclear power plants; So the charging pump can ensure the integrity of structure and the normal operation. (3) The maximum response displacement calculated occures in the central place of the outer shell, and it is 0.345 mm, much less than that of the gap (1 mm) between rotating parts and static parts, indicating that double-hull centrifugal charging pump in the structure meets seismic requirements. Seismic design of charging pump meets the Secondary Parts Requirements of nuclear power plants, ensuring the integrity and operation of the structure.
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