Influence of vibration on the lubrication effect of a splash-lubricated gearbox

In this study, we investigate the effect of rail vibrations on the lubrication and efficiency of a splash-lubricated gearbox; specifically, the gearbox of a rail-transit vehicle. A high-fidelity 3D numerical model of the gearbox in a moving reference system is described, as well as computational fluid dynamics (CFD) simulations of the gearbox with different vibration directions. The effects of rotational speed, oil-immersion depth, and different oil-injection volume rates on lubrication and efficiency are discussed. We propose a method of evaluating the internal lubrication condition of a splash-lubricated gearbox and quantitatively compare the effects of different operating parameters on lubrication and efficiency. Finally, our experiment to verify the feasibility of the simulation method is described. The results show that with vibration, the churning loss and oil supply for the bearings are significantly higher than those under static conditions. In addition, among different vibrational directions, lateral vibration has the greatest influence on the lubrication condition and efficiency of the gearbox. For the studied railway-vehicle gearbox, the best lubrication condition is achieved at a rotational speed of 1600 r/min and an oil-immersion depth of two times the tooth height (2.0h). Rotational speed is the operating parameter that has the most significant effect on the lubrication and efficiency of the gearbox.