Analysis and experimental validation of air resistance changing trend under all-climate condition

Abstract

The extreme low-temperature environment can affect the electrified components of electric vehicles, leading to significantly reduced driving range. Besides, driving resistance is also a crucial factor, especially the air resistance, that influences the overall performance. However, some core parameters are usually regarded as constant values (e.g., air density, air viscosity), even calculating the accurate air resistance under all-climate conditions. Such hypotheses have not been validated well in a wide temperature range, resulting in potential deviation when considering the dynamic and economic issues. To solve this problem, a convenient and universal calculation method to find out the accurate value of air resistance force under all-climate conditions is proposed in this paper. The basic principle that how temperature affects air resistance is elucidated based on aerodynamic analysis, and the formula for calculating air resistance force at different temperatures is redefined. By using interpolation methods, the curve of air resistance with temperature at a certain place is presented. Eventually, the theoretical calculation results are compared with experimental data from an electric passenger vehicle under low-temperature conditions, which verifies the correctness of the conclusions. It is concluded that the air resistance force cannot be regarded intuitively as a certain constant. In detail, the air resistance force increases by about 4% on average for every 10°C drop in temperature, and the lower the temperature the faster the air resistance increases.