Abstract
In order to study the force and life of the key components in the gearbox of an existing double-rotor wind turbine, the design and structural parameters of the gearbox in the traditional National Renewable Energy Laboratory (NREL) 5 MW single-rotor wind turbine are adopted, and the fixed ring gear of the first planetary stage transmission is released to form a differential gearbox suitable for a double-rotor wind turbine with two inputs. The double input is used to connect the double rotor. Subsequently, the characteristics of the gearbox in a double-rotor wind turbine are discussed. On the basis of the constant rated power of the whole wind turbine, the total power is divided into two parts, which are allocated to the double rotors, then two rotational speeds of the two inputs are given according to different power ratios by complying with the matching principle of force and moment. Furthermore, the force acting on the pitch circle of the planet gear, as well as the force and life of the planet bearing of the two-stage planetary transmission are calculated and compared with a single-rotor wind turbine. The results show that the structural advantages of a double-rotor wind turbine can reduce the stress of key components of the gearbox and increase the life span of the planet bearing, thereby the life of the whole gearbox is improved and the downtime of the whole wind turbine is reduced.
Highlights
The past decades have witnessed a booming expansion in scales, such as the emergence of the tens of megawatts wind turbines, which include two types of direct-drive and gearbox
The results show that the power generated by a double-rotor wind turbine (DRWT) is 7% higher, but the complexity of their structure brings about larger wind load and more complex wake features
The force and life of the planet gear and its bearing with a high failure rate in the gearbox were calculated to compare with traditional single-rotor wind turbine (SRWT), and the following conclusions can be drawn: (1) The force on the gearbox of the DRWT is nearly half smaller than that of the SRWT, including the tangential force on the pitch circle of the planet gear and the force of the planet gear bearing
Summary
The past decades have witnessed a booming expansion in scales, such as the emergence of the tens of megawatts wind turbines, which include two types of direct-drive and gearbox. The advantages of the DRWT structure to the gearbox are highlighted: (1) by dividing the high power into two parts and input simultaneously, the transmission torque and forces of gears and their bearings are effectively reduced, and the service life of the bearing is improved; (2) in actual design, different power ratios of double rotors can be selected according to the specific conditions of manufacture, installation, operation and maintenance; (3) the blade length can be shortened to varying degrees and the moment balance of nacelle can be achieved. Part 4 establishes the statics model of the force and life of planetary gears and their bearings in the gearbox of a DRWT at different power ratios. Part shows the analysis of the calculation results of Part 4 and compares the results with those of the traditional single-rotor wind turbine (SRWT) planetary gears and their bearings. Part 6 is the summary and conclusions of this paper
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