Objective The metro train air supply system provides power for onboard pneumatic equipment. Insufficient airtightness may lead to a reduction in the efficiency of the air supply system, thereby decreasing the reliability of critical onboard equipment such as braking devices, door control systems, and suspension systems. Therefore, it is necessary to study the airtightness condition of the metro train air supply system.

Method Small-orifice leakage models as well as flat-plate or annular gap leakage models are analyzed, the effects of leakage location and leakage opening numbers on leakage speed are summarized. Based on the airtightness requirements of air supply system components, a component model with leakage characteristics is developed. Combining the impact of different leakage parameters on leakage speed, a simulation model of the metro train air supply system is developed. A 24-hour static airtightness simulation analysis is conducted for two typical leakage conditions, and the accuracy of the model is verified.

Result & Conclusion  In the gap leakage model that is closer to the actual leakage characteristics, the total air reservoir pressure can still be maintained at approximately 200 kPa after 24 h of leakage, whereas in the small-orifice leakage model, the pressure approaches zero after 20 h, confirming that the gap leakage is the dominant leakage mode in the system. Leakage location and leakage opening numbers have a relatively small effect on the total leakage speed; at the same pressure level, multiple leakage points can be equivalently represented as a single leakage point. By calibrating the model leakage parameters using measured pressure data, the model can be adapted to different vehicle types, enabling accurate prediction of the airtightness condition and long-term performance evaluation of the air supply system.