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Product technology
The function of variable propeller and yaw bearing
 
Wind turbines are mechanical and electrical equipment that converts wind energy into mechanical energy and then transforms mechanical energy into electrical energy. Wind turbines are usually made up of wind turbines, pitch control systems, speed regulating devices, yaw systems, transmission devices, generators and towers.
 
Figure 4-1 schematic diagram of installation position of yaw and paddle bearings
 
 
 
 
Yaw bearing function
 
The yaw bearing is used to rotate the tower top cabin. The gear ring is connected with the cylinder flange through the bolt, and the non gear ring is connected with the engine frame of the engine room to keep the fan forward to the wind, to deviate from the wind direction, or to remove the cable when the cable is Overtwisted.
 
 
The function of rotor bearing
 
The function of the pitch bearing is to rotate the blades installed on the hub, the outer ring is connected to the hub through bolts, and the inner ring is connected with the blades. When the wind speed is too high or too low, the angle of attack is changed by adjusting the pitch of the blade blade, which changes the aerodynamic torque obtained by the wind turbine to keep the power output stable. At the same time, the starting process of the fan also needs to get enough starting distance by variable distance.
 
 
Selection of variable propeller and yaw bearing
 
The working conditions of pitch and yaw bearings are low speed swing, vibration impact, fretting wear and corrosion. They mainly bear axial force and overturning moment when working. It is found that the load distribution of the rotor and yaw bearing is not fully conformed to the cosine law, and the light load area of the theoretical contact pressure is zero in the vicinity of the overturning axis, and the size of the light load area increases with the increase of the clearance. In order to reduce or eliminate the light load area, the bearing of the ball structure can realize the negative clearance through the slight interference between the ball and the raceway, so that the load distribution is even more uniform.
 
The common structure and characteristics of pitch and yaw bearings are as follows:
 
(1) single row four point contact ball bearings have lower cost and higher comprehensive performance.
 
Second, the double row four point contact ball bearing has large torque capacity, high service life, large bearing capacity, small rotary resistance, large allowable wear, low requirement for installation base and low motion precision.
 
Third, the single row of cross roller bearing has high precision and high dynamic load capacity, but it has high requirements for the rigidity and precision of the base, and the edge effect is easy to occur when the roller is in contact with the raceway, which causes the actual stress of the edge to be far greater than the design stress.
 
IV) three row roller bearings generally have very high static bearing capacity.
 
The megawatt grade fan bearings usually choose the double row four point contact ball bearing; the yaw bearing mainly selects the single row four point contact ball bearing or the double row four point contact ball bearing, and also has a small number of cross roller bearings.
 
If you have any doubts about the selection, please consult intercontinental technical engineer.
 
Fig. 4-2 axial force, overturning moment and radial force
under the combined action of pitch (yaw) axis.
 
Design key points of paddle and yaw bearing
 
I) the reasonable radius coefficient of groove curvature and the initial contact angle are used in the design of the bearing raceway, which is beneficial to the improvement of the bearing ability to resist fretting wear and to slow down the fretting wear and tear of the channel.
 
In order to reduce or eliminate the light load area in the bearing work, the load distribution is more uniform and the running friction torque is reduced.
 
Thirdly, the rational core hardness of the bearing ring, the surface hardness of the raceway and the depth of the effective hardening layer can prevent the surface of the raceway from cracking and compression, and have a higher crushing capacity.
 
IV.) bearing seal adopts special double lip structure, which can prevent oil leakage and invasion of water and corrosive gas, and can cope with the deformation of bearing ring due to load and excessive oil pressure inside the bearing. The sealing material is resistant to ultraviolet light and is durable.
 
(V) grease has low torque, load resistance, abrasion resistance, rust resistance and long life at low temperature.
 
(VI) hot spraying zinc and anticorrosive coating on the bearing surface to increase corrosion resistance.
 
Oar and yaw bearing check
 
The contact fatigue strength, static strength and strength of the connecting bolts, fatigue strength and bending strength of the bearing rings should be checked.
 
The analysis of the finite element system
 
Factors such as rigidly installed foundation, flatness of installation support end face and pretightening force of installation bolts will affect the service life of bearings. The analysis of the finite element system is carried out when necessary.

 
Figure 4-3 exact finite element analysis
 
 
 
 
Fatigue life calculation and static strength check (Germanischer Lloyd 2003 Edition)
Equivalent dynamic load method is used to calculate fatigue life (load spectrum average load or fatigue load).
Using the equivalent dynamic load method to solve the life of four point contact ball pitch (yaw) bearing, it can be divided into five steps.
I) the calculation of the rated dynamic load
1) calculation of single row rated dynamic load
I) the calculation of the rated dynamic load
1) calculation of single row rated dynamic load
Checking of static strength (load spectrum limit load)
Contact stress check (Germanischer Lloyd 2010 Edition)
GL2010 version of pitch and yaw bearings does not require fatigue life calculation. The maximum contact stress should be calculated, and the contact stress should not be greater than the stress value of Table 1. Formula of calculation formula (8), (9), (10)
Table 1 recommended contact stress
The calculated contact stress is not greater than the value of Table 1, otherwise it will be rechecked and checked.
 
Gear strength checking and bolt strength checking
 
Gear tooth contact fatigue strength and tooth root bending fatigue strength check reference standard GB/T19406 - 2003 or AGMA 2101 - D04. The safety factor is shown in Table 2
 
The strength of bolts is checked by reference VDI 2230-2003, and the safety factor is shown in Table 2.
 
Table 2 safety factor

Note: * indicates GL2005 marine wind power requirements
 
Selection of lubricating grease
 
In addition to the dilute oil lubrication of gearbox, most other parts of the wind power generation system are grease lubricated. The grease used for pitch and yaw bearings requires low torque, load resistance, wear resistance, rust resistance and long life at low temperature.
 
> > > > sealing
 
A marine wind generator, working in a corrosive salt fog environment for a long time, water or other corrosive substances entering the raceway causes corrosion of the raceway and rolling body; if solid impurities such as dust enter the raceway, abrasive particles will be formed between the raceway and the rolling body, causing depeeling, stripping and even pits, if the grease is lubricated. Loss, easy to cause dry friction, will increase the bearing rotation resistance moment, and will also aggravate the wear of rolling body and raceway.
 
The rotor and yaw bearing adopts a double lip seal structure. This structure can not only effectively prevent the internal oil loss, but also keep the bearing in the lubrication state, and prevent water and oxidizing gas from invading the raceway and pollute the grease. It can also cope with the deformation of bearing rings due to load and the effect of excessive grease pressure inside bearings.
Shanghai Ouji Kete Slewing Bearing Co., Ltd
Address: No. 368, Fulian 3rd Road, Baoshan District, Shanghai
Service hotline:021-33854491
Sales hotline:021-33854491
Technical hotline: 021-33854496
Fax:021-33854473
Zip code: 021-201906
Website: www.oujichina.com
E-mail: oujikfb@oujichina.com