Bearings in Green Energy
On the last day of May, China's wind power industry certification system finally made substantial progress after three years of preparation. As one of the main drafting units, Schaeffler gave a lot of ideas and experiences on the core components of wind turbines - main shaft rolling bearings.
Then ask everyone, do you know about wind turbine main shaft and its supporting bearings? Today we will briefly introduce it!
When the wind turbine generates electricity, the wind rotor converts wind energy into mechanical energy. The low-speed rotating wind rotor is accelerated by the speed increaser gearbox through the transmission system, and the power is transmitted to the generator for power generation. The transmission system connects the blades of the wind turbine with the generator. The components of the general transmission system include hubs, main shafts, main shaft bearings, fixed units, gearboxes and couplings.
The main shaft of the wind turbine is also known as the low-speed shaft or the impeller shaft, and the main shaft transmits torque from the impeller to other parts of the drive train. The wind turbine main shaft is usually forged from temper hardened steel, the shaft end is processed into a flange to ensure the connection with the bolt, and it is shot peened.
The installation position of the front bearing of the main shaft is located behind the rotor hub, and the rear bearing is located in front of the gearbox, and is used in conjunction with the thrust bearing. The spindle is installed at an angle of approximately 4° to the horizontal.
The force borne by the main shaft bearing mainly includes the weight of the blade and the hub, the self-weight of the main shaft, the supporting force of the main shaft bearing, the thrust force of the thrust bearing, and the force of the wind acting on the main shaft through the blade and the hub. Therefore, the main shaft bearing mainly bears the radial force. Also subject to axial forces due in part to wind forces. The force condition of the main shaft bearing is relatively complicated, changes with the change of wind force, and will generate vibration, so it is difficult to accurately calculate the load on it, so only the load on the bearing can be estimated. The average current load of the bearing is usually determined according to the load, speed and time ratio under several working conditions.
Due to the influence of the force condition and the deformation of the shaft, the main shaft bearing of the wind power generator must have good self-aligning performance, so the commonly used wind power generators use spherical roller bearings as the main shaft bearing. Spherical roller bearings allow slight deflection and misalignment of the inner and outer rings during operation. Although the general inclination angle is not large (generally about 0.5°), it can be guaranteed that any installation between the main shaft of the wind turbine and the bearing seat will not cause edge concentrated stress to damage the bearing. However, the application of spherical roller bearings to the main shaft bearings of wind turbines is not without any problems. Due to the existence of an inclination angle between the installation of the main shaft and the ground, the main shaft bearings are prone to lock-up, resulting in early failure of the main shaft bearings. Some companies have begun to use tapered roller bearings as wind turbine main shaft bearings. For example, FAG has developed double-row tapered roller bearings using carburized steel.
Wind turbine main shaft bearings are installed at a height of tens of meters above the island. It is extremely inconvenient to hoist and replace, and the cost is high. Therefore, high requirements are also placed on the life and reliability of the bearings.
