In recent years, with the rapid development of the economy and population expansion, the demand for energy has also increased. Directly leading to energy reduction, environmental pollution problems have intensified. The country is vigorously developing clean energy. Wind power generation is a mature and promising power generation method in new energy power generation technology. Its safety and cleanliness have been rapidly developed at home and abroad in recent years. The slewing bearing of the wind turbine is an important part of the mechanical equipment, which ensures the normal operation of the wind power generator.
First, the definition
Wind turbine bearing can also be called wind power bearing. It is a kind of special bearing. It has a harsh environment, high maintenance cost, and high life. Wind turbine bearings mainly include yaw bearing, pitch bearing, spindle bearing, and shifting box bearings, generator bearings.
Second, wind power bearing structure
The structural forms of bearings for wind turbines mainly include four-point contact ball bearings, crossed roller slewing bearings, cylindrical roller bearings, spherical roller bearings, and deep groove ball bearings. The yaw bearing is installed at the connection between the tower and the cockpit, and the pitch bearing is installed at the joint of the root of each blade and the hub.
Third, technical requirements
1. material standards
The standard stipulates that the material of the yaw and pitch bearing ring is 42CrMo. The heat treatment is treated by integral quenching and tempering. The hardness after quenching and tempering is 229HB-269HB, the surface of the raceway is quenched, and the quenching hardness is 55HRC-62HRC. Due to the complicated force of the yaw and pitch bearings of the wind turbine and the relatively large impact and vibration of the bearing, the bearing is required to withstand both impact and large loads. The life expectancy of the wind turbine’s main engine is 20 years, and the cost of bearing installation is relatively large. Therefore, the life of yaw and pitch bearing is required to reach 20 years.
2. low-temperature impact
Low temperature impact energy requirements for yaw and pitch slewing bearing rings: -20°CAkv is not less than 27J, and the Akv value in the cold state can be determined by the user. Wind turbines may work in extremely cold areas, with ambient temperatures as low as -40 °C, bearings operating at around -20 °C, and bearings must withstand large shock loads at low temperatures.
Yaw and pitch bearings have special requirements in terms of play. Compared with the yaw bearing, the impact load of the pitch bearing is relatively large, and the vibration of the wind blows onto the blade is also large, so the clearance of the pitch bearing is required to be zero clearance or a slight negative clearance value, so that in the case of vibration lower the fretting wear of the bearing. The yaw bearing requires a small clearance value.
Wind turbine equipment works in the field, and part of the yaw and pitch bearings are exposed to the outside and will be polluted by the atmosphere. The high humidity environment will also corrode the bearing base. Therefore, the yaw and pitch bearings exposed outside are eroded. The surface is required to be treated with anti-corrosion treatment, usually galvanized. Paint protection treatment is applied outside the galvanized layer as needed.
The slewing bearing of the wind turbine is an extra large bearing, which is mainly used for pitch and yaw systems. The load is complicated and the disassembly and maintenance is very difficult. Therefore, the design and manufacturing requirements of the wind power slewing bearing are strict. Due to its large size and difficult installation and disassembly, the maintenance is very difficult, and the failure of the slewing bearing will directly affect the working performance of the wind turbine and even cause downtime. Therefore, the wind power slewing bearing is required to have high reliability and long service life, and at least to reach the service life of the wind power generator, that is 20 years.