Sliding bearings are important components of the turbine shaft system. In addition to supporting the rotor, they also play a crucial role in the vibration of the rotor, greatly determining the safety of the rotor system. Due to its high load-bearing capacity, long service life, and easy processing and maintenance, oil lubricated sliding bearings have been widely used.
There are two ways to maintain lubricating oil pressure in oil lubricated sliding bearings:
1. Using an oil pump outside the bearing to input pressure oil into the bearing, a pressure oil film is formed between the journal and the bearing surface, which is called a static pressure bearing. Even when the journal is not rotating, this type of bearing can maintain an oil film.
2. By relying on the rotation of the journal itself to generate pressure in the lubricating oil layer, an oil film is established to support the rotor, which is called a dynamic pressure bearing.
Steam turbines generally use dynamic pressure bearings, and the oil film pressure of dynamic pressure bearings is generated by the rotation of the shaft itself. In dynamic pressure bearings, there is a certain gap between the shaft neck and the bearing hole, which is filled with lubricating oil.
When the machine is stopped, the journal sinks at the bottom of the bearing.
When the shaft starts to start, the journal relies on the frictional force to climb up along the inner surface of the bearing. After reaching a certain position, the frictional force cannot support the weight of the rotor and begins to slip, which is called semi liquid friction.
As the speed continues to increase, the shaft neck brings viscous lubricating oil into the wedge-shaped gap (oil wedge) between it and the bearing. Because the wedge-shaped gap is convergent, its inlet section is larger than the outlet section, so a certain oil pressure will be generated in the oil wedge, and the shaft neck will be squeezed to the other side by the pressure of the oil. If the lubricating oil flow into the wedge-shaped gap is continuous, the oil pressure in the oil will increase, causing the average flow velocity at the inlet to decrease and the average flow velocity at the outlet to increase. The oil layer accumulated in the gap is called an oil film, and the pressure of the oil film can lift the rotor journal. When the oil film pressure is balanced with the external load, the journal operates stably without contact with the inner surface of the bearing.
2025 April 1st Week Marginal Product Recommendation:
Three-layer metal-polymer self-lubricating bearings:
Three-layer metal-polymer self-lubricating bearing is lighter and has better mechanical and load performance. In addition, the wear resistance and noise absorbing feature is improved while more variable torque range could be fitted.
https://www.marginalbearings.com/bimetallic-bushes/three-layer-metal-polymer-self-lubricating.html
