Numerical Analysis For Fluid Lubrication On Longitudinal Grooved Water-Lubricated Bearings Based On FLUENT

Compared to metal bearing, the water-lubricated bearing is normally composed of non-metal materials with properties of anti-vibration, anti-silt and anti-wear. Especially it has the characteristics of not polluting rivers, lakes and sea due to the fact that the bearing dose not yields the leak of lubricant. So it is widely applied in many fields. For lubrication mechanism of this kind of bearing, it is difficult to establish accurate analytical model because of the existence of longitudinal grooves in the bearing. Furthermore, the elastic modulus of rubber alloy bearing is quite low, so it will experience serious elastic deformation even under fractional load, which makes more complex the research about the water-lubricated rubber alloy bearing. Considering characteristics of water-lubricated bearing, its lubrication models are set up based on achieved theoretical and practical knowledge.The present research is funded by the National Natural Science Foundation General Project of P. R. China called innovative design theory and method of water-lubricated bearing system with large size and high specific pressure (project number: 50775230). The present work has been done, whose main contents are as follows:First, theoretical analyses of elastic contacting problems are made. Reduced Reynolds equation, elastic deformation equation and water film thickness equation are derived from fluid continuity equation and Navier-Stokes equation. Based on these equations, the formation mechanism of water film and lubrication mechanism of water-lubricated bearing is analyzed theoretically.By employing the FLUENT software, numerical simulation for lubricating model of water-lubricated rubber alloy bearing is carried on, which includes the analyses of the velocity profile and pressure distribution of grooved water-lubricated bearing. Based on the result achieved, the elastic deformation of rubber is profoundly discussed. The effect of contacting pressure on the rubber deformation is analyzed qualitatively. The results show that within converging wedge the pressure on individual working plane of rubber liner is quite high and pressure peaks are formed independently. Indentations in the bearing appear on working plane because of the exiting pressure peaks. The occurrence of water pockets caused by indentations greatly accelerates the formation of lubricating film. Experimental tests on frictional coefficient were operated under increasing rotation speed and applied load. At the same time, in terms of bearing dimensions and lubricant parameters Sommerfeld number was calculated under different velocity and load. Then the relationship between Sommerfeld Number and friction coefficient was mapped under different working conditions. Compared to classical streibeck curves, the lubricating regime of water-lubricated rubber alloy bearing is analyzed. The comparison shows that when the bearing load is above 1000N, the lubrication lies in the mixed regime at low speed (<1000rpm) and will be transferred into elasto-hydrodynamic lubrication phase at high speed(>1000rpm). Compared to speed effect, the applied load contributes little on lubrication regime.