Design and thermal assessment of a dual micro-combustor air preheater for electric vehicle battery cold start

The performance and usability of Li-ion batteries are severely affected under low-temperature conditions, while maintaining an appropriate operating temperature can effectively enhance discharge capability and prolong battery lifespan. In this study, an air preheater with dual micro-combustors is developed based on a single micro-combustor configuration by introducing an additional combustor, aiming to improve the heating capacity for lithium-ion battery preheating under cold conditions. The developed air preheater maintains a relatively compact structure while providing heated air with good temperature uniformity. Numerical simulations are conducted to examine the influence of combustor number and arrangement, tube spacing, ambient temperature, as well as the equivalence ratio on the overall performance of the air preheater. The results show that increasing the number of combustors can effectively enhance the outlet temperature while maintaining a small temperature difference within 0.9 K. The optimal performance is achieved at a tube spacing of 20 mm, with a maximum efficiency of 91.1%. Raising Vhot can effectively improve the efficiency, while ambient conditions have a limited influence. In addition, increasing the equivalence ratio helps to raise the outlet air temperature but slightly reduces the efficiency.