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China Wind Energy Association:Analysis and Suggestions on the Problem of “Running Circle” of Wind Turbine Bearings(2)

Views:130     Author:Site Editor     Publish Time: 2019-04-19      Origin:Site

2. Spindle bearing

(1) The main shaft bearings of MW-class wind turbines with double-row spherical roller bearings are subjected to axial and radial loads at the same time, and the probability of failure is high. This is because the double row spherical roller bearing has a large clearance, and the bearing on the upwind side bears a small load. Most of the radial load and the axial force are received by the downwind bearing, causing excessive roller slippage. Poor lubrication causes the material to change from pitting to sticking, the seat ring and the roller and the cage are deformed unevenly, which changes the coordination between the race and the bearing seat, and causes common faults such as “running circle” and jamming. .
(2) When designing the new transmission system, the spindle bearing has rarely used the self-aligning bearing. It is recommended to use the tapered roller bearing. The radial and axial bearing capacity is strong. The roller can be evenly loaded by pre-tightening, and the roller is not easy. Produces sliding friction. However, due to the high installation and technical requirements of the assembly process, improper adjustment of the bearing clearance can still cause semi-dry rolling friction, and then run-loop failure.

slewing bearing,slewing ring

slewing bearing,slewing ring

(3) The bearing assembly adopts the hot charging method. Since there is not enough heating device, the local heating method is used, and the heating is uneven, resulting in bearing deformation.
(4) During the transportation process, the unit’s damping measures are improper, or a part of the bearing is bearing for a long time, causing local deformation of the raceway.
(5) There are two main lubrication methods for the main shaft bearings of wind turbines currently in operation: grease lubrication and pressure lubricant lubrication, in which the lubricating oil with a higher proportion of lubrication is generally 10-20 rpm, which is low. The rotational speed of the spindle bearing and the planet carrier support bearing is often difficult to form. If the thickness of the oil film is insufficient to separate the two metal surfaces, the lubrication does not achieve the predetermined effect, the bearing will wear out early, the material peeling damage will occur, and the semi-dry sliding friction will occur, which in turn will cause the bearing to run. The pressure lubrication method is very beneficial to improve the working condition of the bearing. In addition to forming the oil film to protect the rolling roller in time, it can also take away heat and abrasive grains to prolong the service life. It is recommended that the spindle bearings be lubricated with pressure oil if conditions permit.

slewing bearing,slewing ring

slewing bearing,slewing ring

2. Transmission bearing
The ratio of the running ring of the high-speed shaft-side bearing in the gearbox is higher than that of the planetary gear bearing, and the reason for the difference is different.
High speed shaft side bearing
(1) The matching tolerance of the bearing and the bearing housing is unreasonable, resulting in insufficient interference. Since the external environment in which the wind turbines operate varies greatly, it is very likely that the standard tolerance zone will not be able to adapt to the operating conditions.
(2) The process control during assembly is not strict, which results in the matching of the limit deviation between the bearing and the bearing seat and the deviation under the limit. At the assembly site, it has actually been found that the assembler selects a bearing with a small amount of interference for fitting.
Planetary wheel bearing
(1) The maximum power of the wind turbine gearbox in actual use may reach more than 3 times of the nominal power. Especially in the case of growing blades, the moment of inertia of the wind turbine is greatly increased, and the impact load on the drive train during the start and stop of the unit is increased. It also greatly increased the domestic unit to increase the blade on the basis of the prototype, and did not redesign the gearbox accordingly, resulting in the case of the gearbox planetary shaft system and the intermediate shaft system with relatively poor rigidity. The load increases the occurrence of bearing stress concentration, which in turn causes the bearing to run.

slewing bearing,slewing ring bearing

slewing bearing,slewing ring bearing

(2) The planetary gear train structure design is weak. The national standard GB / T19073 wind turbine gearbox specifies that the thickness of the planetary gear hub should not be less than 3 times the modulus, in order to ensure that the gear race has sufficient rigidity to resist the deformation caused by the gear force. The deformation of the planetary gear is one of the important reasons for the bearing running circle. The gearbox failure of the planetary gear bearing in the domestic gearbox factory occurs precisely because the design does not meet the thickness requirements of the gear hub proposed by the standard.
For the planetary shaft system, the floating planetary gear shifting mechanism is adopted abroad to achieve the purpose of uniform loading. However, such structures are more complicated in gearbox assembly and adjustment.
Aiming at the situation that the planetary gear structure size is difficult to meet the rigidity requirement due to the space limitation of the wind turbine, the solution of integrating the planetary gear with the bearing outer ring and the integrated flexible pin scheme similar to Timken (see Figure 1) are proposed abroad. Several gearboxes have been trial-produced by the domestic Hangzhou Gear and the South High Gear with integrated structure and integrated flexible pin structure. Since the planetary gears are machined, heat treated and tested in the gearbox and bearing factories according to the machining process, the cost of the gearbox is greatly increased. Domestic wind power machine enterprises are difficult to accept under the current market price. Foreign machine companies have adopted gearboxes of this type in batches.

slewing bearing,slewing ring

slewing bearing,slewing ring bearing,hengguan

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