Dynamics characteristics of wind turbine gear pairs considering lubrication and tooth surface roughness

Lubrication is crucial to the reliability and service life of wind turbine gearbox, especially in the condition of invariable load. The lubrication behavior is mostly determined by the properties of oil film and stress fields near the contact area, which is further influenced by lubrication and tooth surface roughness. In this study, a coupled numerical model combined dynamic model with thermal elastohydrodynamic lubrication model is established to predict the contact lubrication behavior and dynamic characteristics of wind turbine gearbox. The elastohydrodynamic lubrication theory and energy equation is applied to predict contact pressure distribution and the variation of temperature in different surface roughness. In conjunction with numerical model, time-varying meshing stiffness and the transmission error are derived in the form of Fourier series. The effect of the surface roughness and the initial temperature of oil film is discussed by time region diagrams, phase diagrams, Poincare maps and correlation dimension. The bifurcaton diagram is utilized to analyze the bifurcation and chaos characteristics of the gear pairs. The results show that the surface roughness makes pressure distribution and the temperature variation more complicated, and increases the vibration amplitude of gear system. The thermal effect significantly decreases oil film thickness, and increases the degree of chaos. The research provides a basis for the wear fault diagnosis and detection of wind turbine gearbox.