Study On Dynamic Characteristics Of Cavitation Flow In High Speed Water Lubricated Spiral Groove Thrust Bearing

This paper systematically studies the dynamic characteristics of high-speed waterlubricated spiral groove thrust bearings lubricated under cavitation flow conditions.Based on the two-phase flow theory,the cavitation flow lubrication theoretical models of water-lubricated bearings in laminar flow state and turbulent state are established respectively.In the theoretical model,the effects of various interface effects of gas and liquid are considered,and the generalized Reynolds equation for cavitation flow lubrication is established.Considering the overall heat convection and heat conduction of the bearing,the energy equation and the heat conduction equation of the moving ring under non-adiabatic conditions are established.Based on the principle of conservation of particle number,a group equilibrium equation for bubble size evolution in cavitation flow lubrication is established.The group equilibrium equation considers the effects of gas core growth at high speeds,as well as the mechanism of bubble aggregation and rupture.Compared with the single-phase mixed-flow cavitation lubrication model,the cavitation flow lubrication model established in this paper considers the gas-liquid interface effect,and can theoretically predict the evolution of the bubble size distribution.The Reynolds equation of cavitation flow disturbance pressure was deduced by the small disturbance method,and the calculation formulas of stiffness and damping of the cavitation flow lubrication state were obtained.In the numerical solution method,the SOR iterative method is used to solve the generalized Reynolds equation,the step method is used to solve the energy equation,and the discrete interval method,the downhill Newton-SOR method,and the time step method are used to solve the nonlinear bubble size group equilibrium equation.The solver completed the coupled solution of the generalized Reynolds equation,energy equation,and bubble group equilibrium equation of cavitation flow,and calculated the stiffness and damping coefficients.In this paper,the experimentally measured bubble volume probability density distribution and the axial stiffness of the spiral groove bearing are compared with the theoretical predictions.The results show that the theoretical predictions are agree with experimental ones,which verifies the correctness of the cavitation flow lubrication model established in this paper.By numerical simulation of the theoretical model in this paper,the results show that the volume probability density distribution of bubbles is a skewed distribution,the number of small bubbles is much higher than the number of large bubbles,and the bubbles are mainly distributed at the junction of the left groove of the spiral groove thrust bearing.Speeds and bearing structure parameters have a great influence on the stiffness and damping coefficient of cavitation water-lubricated bearings.The cavitation effect causes the direct stiffness coefficient of the cavitation flow to be greater than the direct stiffness coefficient of the non-cavitation flow.The influence of the damping coefficient is small.