Turbulent Cavitation Flow Thermohydrodynamic Lubrication The Static Characteristic Research For High Speed Spiral-Grooved Thrust Bearing

Water-lubricated spiral groove bearing are expected to be widely used because of convenience,green,safe and energy saving.This paper described the development of water-gas lubrication technology and theory,also expounded research background and significance of this topic.Based on the two-phase flow theory,regarded the cavitation flow as two-phase flow,which compose by pure water that regarded as continuous incompressible fluid and bubbles that seen as discrete compressible round sphere.Based on the generalized law of wall,N-S equations,the continuity equation,this paper derived the generalized Reynolds equation and the energy equation;deduced the Population-Balance Equation by using the conservation of particles to describe the evolution of the bubbles distribution;utilized the force equilibrium relationship to establish the bubble speed control equation.And then,a theory model of a high-speed spiral groove dynamic pressure thrust bearing lubrication of water and gas two-phase turbulent flow which considered turbulence effect,inertial effect,heating effect,interface effect and the breakage and the coalescence of bubbles was established.Numerical calculation methods for the model were discussed in this paper and MATLAB code was compiled to solve the model.The pressure distribution,temperature distribution and the bubble distribution of the spiral groove thrust bearing were shown in this paper.The paper also analyzed the influence of the helix angle,the rotational speed and the depth of groove on the main static characteristics of bearing.Numerical simulation results show that the loading capacity and the friction torque decreases when considered the inertia effect and cavitation effect,the reason are the lubricant is thrown out of spiral groove due to inertia effect and the momentum transfer between water and bubbles created by cavitation surface tension when considered cavitation effect.In high speed condition,the maximum temperature rise is lower than the pure water lubrication but higher than the model which ignored the inertial effect.Because the inertial effect would increase the flow rate of fluid,the collision between fluid and wall would become more intense,so the maximum temperature would rise when consider the inertial effect;on the other hand,the energy transfer between water and bubbles causes the maximum temperature fall when considered cavitation effect.Bubble spread mainly concentrated in the divergent area.With the increase of the rotational speed,the pressure of the water film increases,so the number of micronucleus decreases,finally causes the gas fraction decreases;At the same time,the breakage and coalescence effect would become more and more fierce in the case of rational speed,the average bubble diameter would get smaller but the number gets more.The static characteristic of the spiral groove bearing and the evolution of the bubble distribution are in good agreement with the experimental data.