Research on the Liquid Film Force of Water Lubricated Bearing in Desalination Multistage Pumps and Its Coupled Dynamics with Rotor

The stability of rotors in high pressure multi-stage pumps used in the seawater desalination device is directly affected by the dynamical characteristics of water sliding bearings. Unsteady Reynolds equations for liquid films in sliding bearings, which were solved by adopting the narrow bearing theory and Gumbel boundary condidtions and the dynamical characteristic coefficients of sliding bearings, were calculated. Dynamical characteristics of water lubricated bearings with different bearing radius clearances and different eccentricities were studied using computational fluid dynamics and the optimized clearance was determined combining with rigidity and bearing capacity. Using ANSYS, the critical rotary speed under different modeling modes of bearing units was calculated, and the unbalance response and the integrated rigidity of the liquid film for water lubricated bearing were systematically analyzed, among which the latter was dimensionless. The results showed that the pressure and the rigidity initially became larger and then reduced with the increase of the thickness of the water film, while the bearing capacity became larger with the increase of eccentricities. The cross-coupling effects between rigidity and damping had evident influences on the calculating results of the critical rotary speed. The first order critical rotary speed satisfied the engineering design for rotor stability. The bearing B1 had more sensitive response to unbalance than the bearing B2 and for both water lubricated bearings B1 and B2, and there were keq>0, gamma st<0, judging from which the rotor system was stable and rigid. The results provided some references for improving the stable design of the system and the safe and reliable operation of rotor system with multistage pump.