Based on RNG k-ε turbulence model and dynamic grid technology, the internal fluid dynamics model of splash lubrication three stage planetary gear reducer system is established. The distribution of lubricating oil and convective heat transfer characteristic in the system at different input rotational speeds are analyzed. The results show that at high speed condition, the oil gas mixing volume and the degree of atomization of lubricating oil are higher, and the convective heat transfer coefficient of tooth surface is larger, and it takes less time for the convective heat transfer coefficient to reach equilibrium. Meanwhile, the mean convective heat transfer coefficient on the tooth surface of sun gear, planetary gear and ring gear decreases successively.
Based on the gearing theory, the calculation formulas of comprehensive curvature radius, relative sliding speed and tooth surface contact stress of internal and external meshing gear pair of the planetary gear system are deduced in this paper. Combined with load sharing theory and thermal elastohydrodynamic lubrication analysis method, the oil film thickness, film bearing ratio and friction coefficient are solved and the effects of roughness and input power on the friction coefficient are studied. The results show that with the increase of tooth surface roughness, the film bearing ratio decreases and friction coefficient increases; As the input power increases, the film temperature increases, the oil viscosity and film thickness decreases, which causes the tooth surface friction coefficient increases.
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