As the typical structure of sliding bearing, the working conditions and equipment can be summarized as follows. Systematic analysis was carried out on the basis of their working principles and engineering practices:
1. Core Applicable Working Conditions
High-speed overload
Principle support: axial neck bearing through the rotation of the shaft neck to form a cuneiform oil film, using the hydrodynamic pressure effect to achieve lubrication. The stiffness of oil film is directly related to the bearing capacity of oil film.
Typical equipment: Rotor support systems for rotary machinery, such as steam turbines, generators, and large compressors.
Extreme temperatures and corrosive environments
Material advantages: journal bearings are made of high-temperature resistant materials, such as lead-based or tin based Babbit alloys, and can withstand temperatures above 150°C. Non-metallic bearing shells (such as PTFE and graphite) is suitable for corrosive media environments.
Application: internal combustion engine Crankshaft bearings, chemical process pump bearing.
High accuracy and stability requirements
Dynamic characteristics: Tilt pad sliding bearing automatically adjusts through the pad, eliminates edge pressure and achieves high stability. For example, a CNC machine tool spindle adopts removable multi-oil wedge bearings, the radial clearance can be adjusted to 5-15μm, rotation accuracy reaches the micrometer level.
Data support: COMSOL simulation shows that the worm shell ratio (reflecting rotor stability) of inclined bearing is more than 30% lower than that of fixed bearing.
Low-Speed Heavy Load and impact load scenarios
Boundary lubrication applicability: journal bearing operate through boundary lubrication at low speeds of less than 1.5 m/ s (friction coefficient 0.05-0.1). For example, pins and bushing for construction machinery and hinge points for mining equipment.
Reinforcement measures: using extreme pressure EP) grease or adding molybdenum disulfide solid lubricant can enhance the bearing capacity 2-3 times.
2. Typical application equipment
Energy and electricity
Steam turbine/generator: cylindrical, elliptical or multi-blade journal bearings used to support the radial load of the rotor, while thrust-axle-neck combination bearings are subjected to the axial thrust (for example, a certain type of steam turbine combination bearing has the axial load of 500kN).
Wind turbine generator set: shaft bearing adopts double row conical roller bearings and journal bearings combination, suitable for pitch variation and yaw motion.
Industrial machinery sector
Machine tool spindle: high precision grinder spindle adopts fixed multi-oil wedge bearings. Low-pressure oil (pressure 0.5-2 mpa) is supplied by a hydraulic pump, forming an oil film that avoids dry friction on and off. Mobile multi-oil wedge bearing are suitable for high speed and light loads (rotational speed greater than 400r/min).
Gearbox: The input shaft of the heavy-duty gearbox has a journal bearings and is combined with a forced oil supply system (flow rate 50-100L/min) to ensure continuous oil film formation.
In the area of transport
Ship propulsion system: large ship stern tube adopts white alloy journal bearings, seawater as lubricating medium. the JFO cavitation theory is used to modify the fracture zone of oil film to adapt to variable load conditions.
Rail transit: the bearing of high-speed railway traction motors adopts radial roller composite structure, which takes into account the requirements of high-speed and impact load.
Equipment for special working conditions
Nuclear power main pump: Static pressure journal bearings, through the external oil supply system to form a high pressure oil film (pressure 10-15 mpa), to achieve zero wear and tear operation, nuclear safety seismic requirements.
Aerospace: an aero engine high-pressure turbo shaft adopts chaff bearing with corrugated support structure for high temperature and high-speed environment (speed > 20,000 r/min, temperature > 500°C).
3. Selection and Design Highlights
Selection of lubrication methods
High-speed operating conditions (surface velocity > 10m/s): Preference is given to the use of oil rings or pressurized oil pumps for oil supply to avoid excessive temperature due to grease lubrication.
Low speed and heavy load operating conditions: use pressure grease or semi-lubricated journal bearings (such as sintered bronze sleeves) to self-lubrication by oil storage in pores.
Geometric parameter optimization
Aspect ratio (L/D): generally 0.5 -1.5. At high speeds and light loads, it can be increased to more than 2 to improve stability.
Oil film thickness: Design values are generally 0.01-0.1mm and should be larger than the size of the filter pore size (e.g. 5 microns) to prevent particle scratches.
Material matching
Magazine Material: High strength alloy steel (e.g. 42CrMo), surface quenched to HRC55-60 for wear resistance.
Bearing lining materials: Tin-based Babbitt alloy (ZCSnSb11-6) is suitable for high speed and light loading applications, while lead-based Babbitt alloy (ZCPbSb16-2) is suitable for medium speed and heavy loading applications.