The dynamic and hydrodynamic properties of the pad in the fluid pivot journal bearing are investigated in this paper. Preload coefficients, recess area, and size gap, which were selected as input parameters to investigate, are important parameters of fluid pivot journal bearing. The pad’s pendulum angle, lubricant oil flow through the gap, and recess pressure which characterizes the squeeze film damper were investigated with different preload coefficients, recess area, and gap sizes. The computational models were established and numerical methods were used to determine the equilibrium position of the shaft-bearing system. Since then, the pendulum angle of the pad, liquid flow, and recess pressure were determined by different eccentricities.
Fluid pivot journal bearing (FPJB) used on the ships was selected as the object of the study in this paper. The ability to form a squeeze film following the recess area ratio of the pad is systematically investigated under the condition that the preload factor and the eccentricity ratio change. Three positions of the load’s characteristic for the moving conditions of boats on the water are considered. Numerical methods are used to calculate the dynamic lubrication in bearing. Equilibrium conditions of force and moment are used to determine the floating conditions of the pads. The results show that during working process, the pad directly applied by the external force satisfies the floating condition, while the remaining pads are satisfied only when the preload factor and eccentricity ratio increase. In the early stages, the pad mostly float on one side. Floating condition curves are constructed as the basis for determining the optimal recess area.
Previous studies have shown that during the operation of a fluid pivot journal bearing (FPJB), almost only the bottom pad floats. The other two pads are not able to float, resulting in no squeeze film damper (SFD) formed in their places. Therefore, the bearing has not yet reached its full advantage. From this situation, the work focuses on studying how to improve the floating efficiency of the pads in FPJB. Based on a thorough study of the hydrodynamic pressure distribution on the pads and related issues, the orifices are placed in the appropriate position to increase the pressure in the recess. According to this proposed method, all three pads reach the floating state during the stable working of the bearing. The numerical model of FPJB in previous studies is applied to evaluate the effectiveness of the proposed solution. The effect of orifice positions on the buoyancy of the pads was then also thoroughly investigated, and results are then provided and discussed. In the case that orifices are in the middle of the pads, only the bottom pad satisfies floating conditions and the other two pads are almost not able to float. The floating effect of the pad increases when the orifice is moved closer to the top of the hydrodynamic pressure. After the orifice's position is adjusted, the recess pressure increases significantly so that the hydrostatic torque increases while the hydrodynamic torque remains unchanged. As a result, all three pads satisfy the floating conditions. The SFD is not only formed, but also reaches a large value, and therefore, the damping will be greatly increased. Then the calculation results are verified based on a comparison with the data in the previous studies.
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