Analysis Of Cavitation Performance On CAP1400 Nuclear Reactor Coolant Model Pump

As a clean and efficient energy, nuclear energy is more and more widely recognized and adopted. The CAP 1400 nuclear power plant designed by our country independently marks a tremendous progress in the nuclear power industry. Nuclear reactor coolant pump is the only high speed rotating equipment in nuclear primary coolant circuit and its design performance is very significant for safety operation in nuclear power station. Cavitation damage is a failure mode that generally exists in hydraulic machinery. The occurrence of cavitation will decrease the performance of hydraulic machinery, leading strong noise and vibration, even the damage of blades, and affecting the stable operation of the system. Therefore, it is necessary to consider the cavitation performance in design process of nuclear main pump in order to avoid the occurrence of cavitation.Nuclear reactor coolant pump works at high temperature and high pressure, the vapor/liquid density ratio in this condition is larger than room temperature, other qualities such as saturated vapor pressure in high temperature can influence the thermal field more distinctly than room temperature. Consequently, the local temperature drop due to the vaporization is non-negligible in nuclear reactor coolant pump, hence the energy transport needs to be included in the cavitation model. Based on the homogeneous-fluid method and transport equation, source term which concerns the thermodynamic effect is added in energy equation by importing UDF program. The reliability of the model is checked by comparison between simulation and experiment results of NACA0066(MOD) foil at room temperature. It is found that the cavitation region around foil of water temperature at 373K becomes shorter than room temperature. The impeller cavitation performance is simulated at 373K and 473K, the result shows that mass transfer process causes large temperature decrease. Besides, the temperature difference narrows after consider the decrease of saturated vapor pressure. In some situations the cavitation performance and efficiency of pump are contradictory in the design process of pump. Thus the cavitation performance of the nuclear main pump can be less considered in order to improve the efficiency of the pump.The cavition flow field characteristics of the model pump impeller, guide vane and volute under different NPSHs are analyzed. The model pump’s cavitation performance is revealed when the beginning bubble happens, the performance of pump is compared between the impeller and the complete pump simulation, the influence of guide vane and volute on impeller’s cavitation flow field is discovered. Furthermore, precision casting aluminum alloy impeller and sand cast impeller with sand cast guide vane are produced to carry out the model pump experimental research. The result shows that the manufacturing precision of the impeller has a great influece on critical NPSH. In addition, the pressure pulsation time-domain plot of inlet surface become disorder at low cavitation number in the unsteady numerical simulation of pump, a strong re-entrant jet is found at the end of severe cavitation region.A water injection hole is placed on the suction side of the foil to barrier the re-entrant jet and suppress cavitation. It is found that the water injection hole can barrier the re-entrant jet rushing from the trailing edge to the leading edge of the foil, the cavitation region is shortened with the increase of injection ratio, it shows that cloud cavitation could be controlled effectively by water injection placed on the foil. Besides, it results in a reduction of amplitude of lift and drag coefficients of the foil, and has little effect on the average values.