A methodology for modeling the thermal behavior of an electric axle in real driving cycles 2024-01-2588

The thermal behavior of the electric axle is an essential indicator which requires certain attention during the development process. Due to the complexity of heat generation mechanism and heat transfer boundary conditions, it is difficult to accurately predict the axle’s temperature, especially in real driving conditions. In this paper, a comprehensive 1D model is developed to simulate its heat transfer process effectively and accurately.

The heat transfer model is developed based on the thermal network method, and the electric axle is divided into thermal mass according to its heat transfer characteristics. The heat generation model, which accounts for meshing loss, bearing loss, churning loss, and windage loss, exchanges heat flux and oil temperature information with the heat transfer model to take into account the effect of lubricating oil temperature on power loss. Meanwhile, 3D simulation is established for the lubricating oil flow inside the axle and the air flow around it, from which the fluid velocity or void fraction could be generated and further applied to calculate the heat transfer coefficient. Thus, the integrated 1D model is realized to simulate the whole heat transfer process.

The proposed model is validated under several real driving cycles of a commercial heavy-duty truck, and the simulation results show positive consistency with experimental results. Further analysis is conducted including proportion of various power loss and oil temperature rise curve, which provides profound insight into understanding thermal behavior of the electric axle. In conclusion, the proposed method exhibits attractive application prospect in the design and optimization process.