| In a pressurized water reactor (PWR), cooling water in the first loop is in direct contact with the nuclear reactor, absorbing and transfer large amount of heat. The working fluid is under severe operating conditions, for instance high temperature and pressure, large flow rate and strong radioactivity etc. Therefore, the nuclear main pump which drives the coolant inside the cooling system must have the characteristics of high pressure and temperature, and large flow rate as well. Moreover, as the only existing high speed rotary equipment inside the first loop, there are stricter requirements on its safety and performance than general water pumps. Currently the key technique of design and manufacturing of the nuclear main pump is monopolized by few western countries. In order to break the monopoly and the technique blockage from the western countries, it is of great importance of achieving independent design and manufacturing of the nuclear pump.In this thesis an innovative CFD-based design method of high efficient hydraulic components from a third-generation nuclear main pump AP1000is investigated and improved. The design and analysis were conducted for a nuclear pump which consists of an impeller of7moving blades, a diffuser of18guiding blades and a central outlet volute. The resultant hydraulic model of the nuclear main pump has the optimal match between the numbers of moving blades and guiding blades, excellent hydraulic performance and anti-cavitation characteristics. This study provides a preliminary attempt to achieve the nationalized design of the third-generation nuclear main pump.We firstly discuss and extend the issue of modeling design of blade number using previously proposed CFD approach. The blade number of the impeller was increase from5to7and three-dimensional numerical simulations were conducted using three turbulent models i.e. k-ε, SA and SST model. According to the computed results the characteristics of hydraulic and cavitation were analyzed and the profile and inlet angle of the impeller blades are optimized. It was shown that the adopted optimal strategy is properly constructed and the design performance is significantly improved.The guiding blades (18blades) of diffuser were then designed from the perspective of the match between the numbers of moving and guiding blades, and the central outlet volute of constant cross section was also designed by ensuring operating reliability and safety. The interfering effect between the moving and guiding blades was computationally analyzed using the transient Harmonic algorithm and the effect of the radial gap between the impeller and guiding blades on the overall performance was also emphasized. By taking into account of the requirements of pump lift and efficiency, it was revealed that the gap value of15-17mm can deliver the best performance and this can be used as guide for future design. The computationally derived overall performance curve has a decent trend and a hydraulic efficiency of86%was achieved. The final design meets the strict requirements of hydro-dynamic strength, cavitation and hydraulic etc.Finally, the unit design of a nuclear main pump with different power requirements was attempted in this paper. It was found that although the CFD-base modeling design approach was proposed in the process of impeller component design, it can also be extended to the unit design. It was revealed in the attempted unit design of the nuclear main pump AP1200and AP1400that the improved modeling design method has prominent features of facilitating the unit design (including impeller, guiding blade and volute), inheriting desirable performance from model pumps, simplifying the design process and shortening the design period. |
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