Wind turbine gear box

As the unit is installed in the tuyere of mountains, wilderness, beaches, and islands, it is affected by the unregulated wind force changing to a variable load and the impact of strong gusts. It suffers from the effects of extreme heat and extreme temperatures throughout the year, coupled with the inaccessibility of the natural environment. The gearbox is installed in a narrow space on the top of the tower. Once a failure occurs, repair is very difficult. Therefore, the reliability and service life of the gearbox are much higher than those of general machinery. For example, the requirements for component materials, in addition to the mechanical properties under normal conditions, should also have the characteristics of resistance to cold and brittleness at low temperatures; ensure that the gearbox works smoothly to prevent vibration and shock; ensure adequate lubrication conditions, and so on. For areas where the temperature difference between winter and summer is huge, appropriate heating and cooling devices must be configured. Also set up monitoring points to remotely control the operation and lubrication status.

Different types of wind turbines have different requirements, and the layout and structure of the gearboxes also vary. In the wind power industry, horizontal axis wind turbines are most commonly used with fixed parallel shaft gears and planetary gears.
As mentioned before, wind power generation is affected by natural conditions, and the occurrence of some special meteorological conditions may lead to the failure of the wind turbines, while the narrow cabins may not have a solid foundation like the ground, and the power of the entire drive train. The factors of matching and torsional vibration are always reflected in a certain weak link. A lot of practice has proved that this link is often the gear box in the unit. Therefore, it is particularly important to strengthen the research on gearboxes and pay attention to the maintenance work. Section II Design Requirements Design must ensure that the structure is simplified and the weight is lightest, provided the reliability and life expectancy are met. Generally, CAD should be used to optimize the design, arrange the best transmission scheme, use reasonable design parameters, select stable and reliable components, and have good mechanical properties and materials that remain stable under extreme environmental temperature differences, and so on.

First, the design load gear box as a power transmission component, at the same time to withstand dynamic and static load during operation. Its dynamic load depends in part on the characteristics of the wind turbine, the generator, and the mass, stiffness, damping value of the drive shaft, coupling, and the external working conditions of the generator.
The wind turbine generator load spectrum is the basis for the design and calculation of the gearbox. The load spectrum can be obtained through actual measurement, or it can be determined according to the JB/T10300 standard calculation. When calculated according to the measured load spectrum, the gearbox use factor KA=1. When the load spectrum cannot be obtained, KA=1.3 is used for the three-blade wind turbine.

Second, the design requirements of the wind turbine generator speed increase the design parameters of the box, unless otherwise specified, often using the method of optimization design, that is, the use of computer analysis and calculation, to meet the various constraints to obtain the optimal design.

(a) The efficiency of the efficiency gearbox can be calculated by power loss or measured in the test. The power loss mainly includes gear meshing, bearing friction, lubricating oil splash and agitation loss, windage loss, and damping of other components. The efficiency of gears is inconsistent under different operating conditions.
The professional standards for wind power gearboxes require that the mechanical efficiency of the gearboxes should be greater than 97%, referring to the indicators that should be achieved under standard conditions.

(2) The noise level of the noise-grade wind power acceleration gearbox is about 85dB(A). The noise mainly comes from the various transmission parts, so measures should be taken to reduce noise:
1. Appropriately improve the gear precision, carry out tooth profile trimming, increase the degree of meshing and coincidence;
2. Improve shaft and bearing stiffness;
3. Reasonably arrange shafting and wheel train transmission to avoid resonance;
4. Take necessary vibration reduction measures during installation, and control the mechanical vibration of the gearbox within Class C specified in GB/T8543.

(c) Reliability According to the requirement of an assumed life of at least 20 years, fatigue analysis shall be carried out based on the load distributions listed in the load spectrum, and ultimate strength analysis and fatigue analysis shall be carried out on the design limit state and service limit state of the gearbox and its parts. Stability and deformation limit analysis, dynamic analysis, etc. In addition to the commonly recommended design calculation method, the analysis method can be used to simulate parts under the host operating conditions.
Reliability analysis must be carried out at the beginning of the project design. After the construction design is completed, detailed reliability analysis calculations are performed again, including carefully selecting a reliable structure and estimating the reliability of important components and the whole machine. The third section of the gear box structure First, the type and characteristics of the gear box Wind turbine gear box of many types, according to the traditional type can be divided into cylindrical gear box, planetary gear box and their combination of the gear box; in accordance with The series of transmission can be divided into single-stage and multi-stage gearboxes; according to the rotation arrangement, it can be divided into expandable, split-flow and coaxial, and hybrid and so on. The form of common gearbox and its features and applications are shown in the table. 20.1-1.

Second, the gear box box is an important part of the gear box, it receives the force from the wind wheel and the reaction force generated when the gear transmission, must have enough rigidity to withstand the role of force and torque, prevent deformation, to ensure transmission quality. The design of the box should be based on the layout of the power transmission of the wind turbine, the processing and assembly conditions, and the convenience of inspection and maintenance. Pay attention to the reaction forces and their relative values ​​in different directions of the bearing support and the machine base support, select the appropriate support structure and wall thickness, and add the necessary reinforcing ribs. The position of the rib must be consistent with the direction of the force that causes the box to deform.

The stress of the box is very complex and unevenly distributed. Only by using modern calculation methods, such as finite element method and fracture mechanics, supplemented by photoelastic experiments that simulate actual conditions, can we accurately calculate the stress distribution. With computer-aided design, results that are very close to the actual stress can be obtained.