A Half Direct-drive Small Wind Turbine Based On Line Gear Transmission

This paper studies a type of half direct-drive small wind turbine and its transmission mechanism. The transmission mechanism applies a single-stage line gearbox. Line gear(LG) is an innovative gear mechanism, which is based on the meshing theory of space conjugate curve meshing. With the characteristics of a large transmission ratio, small size and no root cutting, it is mainly applicable to small space transmission. LG mechanism can mesh at the included angle θ from 0 deg to 180 deg. The main contents of this thesis includes as follows:1. Based on line gear theory and wind turbine theory, this paper presents design methods and ideas of a small wind turbine with a single-stage line gearbox. According to the transmission characteristics of LG mechanism and the overall layout requirements of wind turbine, three typical line gear transmission mechanisms are proposed. By comparison and certification, orthogonal axis(oθ =90) line gear assembly is chosen as drive-train of a small wind turbine. Then, Design calculations, modeling and increasing material manufacturing are carried on a single-stage line gear pair. At the same time, the whole structure of line gearbox is designed, including design calculations of shafts and bearings, etc.2. The contact stress and contact fatigue life of line teeth are analyzed for wind turbine gearbox. LG mechanism is the point contact meshing transmission. Based on Hertz point contact theory and ANSYS finite element software, this paper calculates the line tooth contact stress. Comparing two analysis results, the datum are similar, but finite element calculation results are closer to engineering practice. By P-S-N curve graphic method, predict contact fatigue life of line teeth. The results show that line gears applied to a small wind turbine can meet the project fatigue life design.3. A modal analysis on vibration of line gear assembly is studied by ANSYS software. The natural frequencies of this two critical cases where double line teeth mesh and three line teeth mesh are analyzed, respectively, and compare with line gear meshing frequency. The results show that line gear meshing frequency is obviously less than the natural frequency of line gear assembly, so it won’t occur resonance phenomenon. Finally, analyze the influence of three line gear design parameters on natural frequency of line gear assembly.4. Based on Labview software, a small wind turbine test platform is developed. And external characteristics of a half direct-drive small wind turbine are examined. The experimental results show under a small volume and low-cost fabrication situation, this half direct-drive small wind turbine still has a good power performance. For example, under the rated wind speed 10m/s, a power of 80 W or more of electrical energy can easily generated from a half direct-drive small wind turbine with a 0.5m wind wheel radius.