Research On Damping Characteristics Of Water-lubricated Bearings Restrictor For A Nuclear Pump

Nuclear pump is one of the important facilities in the nuclear power station. The main pump together with the second nuclear pumps play an important role in ensuring the operational efficiency and reliability of the nuclear power station. The basic shaft of nuclear pump (with the length of over ten meters) works safely relying on two water-lubricated radial bearings and one thrust bearing. The bearings are the key parts in the water pump whose performance determines nuclear pump's safety in the operation. The improvement of bearing's lubricated performance will greatly increase the efficiency and reduce wear. The water-lubricated bearings have the advantages as follows: pollution-free and enormous, nonflammability reducing security risks, low-cost and easy maintenance compared with those lubricated by oil, low friction, vibration and noise; the simple structure of the bearing system.The present thesis studies the damping characteristics of the water-lubricated radial bearing-restrictors in the case of the constant-pressure water-supply. Restrictors play the role of regulating pressure of water chamber and ensuring the bearings' loading abilities and water film's stiffness. Bearings' performances rely on the restrictors' geometry and size parameters to a large extent. Therefore, restrictors' damping characteristics will greatly influence dynamic-static pressure water-lubricated bearings' performances.Because of restrictor's peculiarity in structure and size, up to now it can't be simulated by the present equations directly. To solve this problem, CFD software, FLUENT, is used to analyse water lubricated bearings restrictor. The method is verified by comparing with the simple examples' theoretical solutions. Then damping characteristics of different shapes of restrictors is simulated in the conditions of both laminar and turbulence flows. By plotting and analyzing the flux-pressure-drop curves, some damping relations between the flux and the pressure-drop are obtained for engineering applications. The fitting equations are given from the simulated results. Equivalence relations of rectangular and circle sections are found as well. The basic technical parameters of the restrictors are also provided for the whole bearing's numerical simulation. Conclusions in the thesis are helpful for guiding water-lubricated bearings and restrictor's design and performance predictions.