基于喷雾冷却的发动机排气系统减阻

Drag reduction of engine exhaust system based on spray cooling

采用电加热喷雾冷却减阻试验台,系统研究了喷雾流量、喷雾倾角、气流温度、气流速度影响发动机排气系统减阻性能的规律;采用基于离散相模型(DPM)的数值模拟,阐释了喷雾冷却大幅降低排气阻力的原因。研究结果表明:喷雾流量为12~24 mL/s时,减阻率随喷雾流量的增加而增大;喷雾倾角由45°增加至90°时,减阻率先保持不变后减小,45°和60°喷雾倾角时的减阻效果均为最佳;气流温度为200~300℃时,随着气流温度的升高,减阻率呈增大趋势;气流速度由20 m/s增大至30 m/s时,减阻率逐渐下降。排气系统喷雾后阻力大幅度减小的原因是喷雾后气流速度降低,湍流强度降低,局部阻力和摩擦阻力显著减小。

The electric heating spray cooling drag reduction test bench was used to systematically study the influence of spray flow rate,spray inclination angle,airflow temperature,and airflow speed on the drag reduction performance of the engine exhaust system.The reason why spray cooling can significantly reduce drag was revealed by DPM-based numerical simulation.The research results show that the drag reduction rate increases with the spray flow rate when the spray flow rate is between 12 mL/s and 24 mL/s.When the spray inclination angle is increased from 45°to 90°,the drag reduction first remains unchanged and then decreases.The drag reduction effect of 45°and 60°spray inclination is the best.When the airflow temperature is between 200℃and 300℃,the drag reduction rate increases with the airflow temperature.The drag reduction rate decreases gradually when the airflow velocity increases from 20 m/s to 30 m/s.The reason for the significant reduction in the drag of the exhaust system after spraying is that the airflow velocity reduces,the turbulent intensity reduces,and the local and frictional drag reduces.