Abstract: Radial sliding bearings have been widely used in power transmission systems such as steam turbines, gas turbines, and gearboxes. Radial sliding bearings have the advantages of high load-bearing capacity, low power consumption, impact resistance, and high operating accuracy. In order to improve the load-bearing capacity and positioning accuracy of sliding bearings, it is necessary to control the temperature rise of sliding bearings. With the increasing demand for high-speed and high load sliding bearings in engineering applications, the design of sliding bearings has become a focus of attention.

Keywords: fluid dynamic pressure; Sliding bearings; Optimized Design

1. Preface

In ship power plants, the shaft power transmission system is a very important component, and the safety and reliability of the shaft system affect the power performance of the ship. Due to the fact that sliding bearings are an important component of ship shaft systems, they play a role in positioning and load-bearing. Cooling sliding bearings can reduce bearing wear and increase their service life. Reasonable lubrication methods can not only improve the friction performance of sliding bearings, but also reduce the temperature rise of bearing shells. Therefore, it is necessary to optimize the design of the bearing structure in order to improve the working performance of the bearing.

2. Mathematical model of flow field in sliding bearings

When solving the flow field inside sliding bearings, it is necessary to fully consider the cavitation effect and viscosity temperature effect. However, the increase in oil film temperature will be affected by the flow characteristics of the lubricating oil, and the flow characteristics of the lubricating oil will change its viscosity. Therefore, when calculating sliding bearings, factors such as the flow characteristics of the lubricating oil, viscosity temperature effect, and viscosity dissipation should be taken into account. If the speed of the sliding bearing is high, turbulence will occur in the flow field.

2.1 Hole Model

Due to the significant role of cavitation effects within sliding bearings, this article mainly adopts the "full cavitation" model for simulating cavitation in sliding bearings, and the fluid is mainly composed of three parts: lubricating oil, steam, and insoluble gases. The essence of cavitation phenomenon refers to the phase transition of mass transfer between gas and liquid phases.

If the speed of the sliding bearing is high and the clearance is large, the flow field of the sliding bearing will experience pulsation and also exhibit turbulent properties. In laminar flow, the fluid mainly flows smoothly in layers without mixing between adjacent fluid clusters. However, when molecules collide and exchange, laminar flow can manifest as a regular flow. Turbulence is a complex, unsteady, and random vortex motion, and in addition to collisions between molecules, fluid micro clusters can exchange mass and momentum through violent mixing and pulsation. The basic characteristics of turbulence can be manifested as randomness or pulsation.

2.2 Discretization of Equation

This article mainly uses the control volume method to solve the transport equation of the sliding bearing flow field. The basic idea of the control volume method mainly refers to dividing the calculation area into a series of grids, and each grid node has at least one non repeating control volume. Then, the differential equations with solutions are controlled on each control volume for integration, resulting in a set of discrete equations. Therefore, the control volume method is also known as the finite volume method, and its physical significance mainly lies in the conservation law of physical field variables within a finite size control volume.

3. Study the static characteristics of sliding bearings

The heat transfer inside sliding bearings is relatively complex, and sliding bearings mainly involve convective heat transfer between the lubricating oil and the inner wall surface of the bearing, as well as convective and radiative heat transfer between the outer wall surface of the bearing and the outside world. At this time, the viscous dissipation of the lubricating oil generates frictional heat and other phenomena. Convection heat dissipation is the main form of heat dissipation in high-speed bearing lubrication systems, accounting for about 90% of total heat exchange. In addition, due to the large temperature gradient inside sliding bearings, temperature can affect the viscosity of lubricating oil. The oil supply temperature and pressure have a direct impact on the static characteristics of sliding bearings, and by selecting appropriate oil supply pressure and temperature, the working performance of sliding bearings can be improved. There are two main reasons for the formation of cavities in sliding bearings: firstly, when the lubricating oil flows into the non load bearing area, the oil film pressure continuously decreases. Compared with the saturation pressure of the sliding oil at the same temperature, the pressure at this time decreases. Secondly, when the lubricating oil undergoes a phase change and produces cavities, it is called a strong cavity; The second type mainly includes insoluble bubbles in the lubricating oil. When the lubricating oil enters the non load zone, due to the continuous decrease in external pressure of the bubbles, the diameter of the bubbles will eventually increase and the oil film will rupture. Under different working conditions, the cavity pressure of East China bearings will also vary, so it is necessary to conduct in-depth research on the influence of cavity pressure on sliding bearings.

The static characteristics of sliding bearings mainly refer to the distribution of parameters such as bearing capacity, friction coefficient, displacement angle, oil film pressure, and temperature under different loads when the sliding bearing works stably. After passing through the oil supply hole, lubricating oil flows into the sliding bearing chamber through a certain pressure and temperature, and the pressure and temperature at this time are called the oil supply pressure and oil supply temperature. The rotation of the shaft neck can inject lubricating oil into the convergence gap, thereby generating fluid dynamic pressure. At this time, the resultant force of the oil film pressure is balanced with the load on the shaft neck, and the balance position is mainly biased towards one side. During the operation of actual bearings, as the oil film pressure in the diverging section continues to decrease, air dissolved inside the lubricating oil will form bubbles, which will eventually cause the oil film to rupture. In addition, if the pressure is lower than the saturation pressure of the lubricating oil at a temperature, the lubricating oil will undergo a phase change into steam, resulting in cavitation in the loose section of the sliding bearing.

The rotation of the shaft neck will cause the oil film to experience wall shear force and generate frictional resistance and heat on the shaft neck. One function of lubricating oil is to separate the bearing shell from the journal, thereby avoiding solid dry friction between the two. Another function is to remove the heat generated by fluid friction. As the viscosity of lubricating oil is affected by temperature, when the temperature of the lubricating oil rises, the viscosity will decrease. If the temperature of the lubricating oil inside the bearing is too high, the viscosity of the lubricating oil will decrease, and the oil film bearing capacity will also be reduced, ultimately causing lubrication failure. Therefore, it is necessary to control the high temperature of the oil film Z of the sliding bearing. The viscosity temperature relationship of lubricating oil can be calculated through viscosity, and studies have shown that within a certain temperature range, the viscosity of lubricating oil exhibits an exponential distribution with temperature. When the journal rotates at high speed, the lubricating oil will generate viscous dissipation and frictional heat under the action of shear force, and this will cause the oil film temperature to continuously increase. After the oil film temperature increases, the viscosity of the lubricating oil will continuously decrease, and the decrease in viscosity will cause its bearing capacity to continuously decrease.

4. Conclusion

Through a reasonable analysis of the heat exchange process inside sliding bearings and the cooling mechanism of lubricating oil heat exchange, it is concluded that the heat conduction process inside bearings is essentially a process of combining parameters such as oil flow rate, viscosity temperature characteristics, eccentricity, etc. After calculation and comparison, if the viscosity temperature effect and energy equation of the lubricating oil are not fully considered, it will affect the bearing characteristics. This article analyzes the effects of oil supply pressure, oil supply temperature, cavitation pressure on the static characteristics and cavitation distribution of multi sliding bearings, in order to improve the friction coefficient of sliding bearings.

2026 July 1st Week Marginal Product Recommendation

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