A cross timescale modeling of helical gear transmission for heat dissipation and lubrication evaluation

The exponential time span between temperature and multiphase flow evolution poses a challenge for heat dissipation and lubrication evaluation of helical gear transmission under various operating conditions. For the challenge, this paper proposes a cross timescale heat-flow coupled model to realize the fast response of bulk temperature of the gear to the fluid environment by coupling multiphase flow model (small timescale) and thermal network model (large timescale). The average lubricant surface fraction (δl,ave), convective heat transfer coefficient (have), and churning moment (Mave) of the gear are evaluated by this model under load, slope, and acceleration conditions. Based on the evaluation results, the mapping rules between δl,ave, have, Mave and the effect mechanism of operating conditions on them are revealed. The mapping rules show that higher δl,ave is a necessary insufficient condition for stronger have, as well as an unnecessary insufficient condition for larger Mave. In fact, have is mainly proportional to the continuous lubricant film thickness normal to the wall. And the effect mechanism of the operating conditions indicates a positive relationship between δl,ave, have, Mave, only when the operating conditions change have and Mave by affecting δl,ave and the near-wall lubricant film thickness.