Impact of recharge duration on the cyclic braking performance in a 20,000-ton heavy-haul train

Heavy-haul trains operating on long and steep downhills must adopt cyclic air braking to prevent overheating and overspeed. The recharge duration between successive braking applications plays a critical role in determining braking effectiveness and longitudinal dynamic behaviour. This study investigates the influence of recharge duration on the cyclic braking performance of a 20,000-ton heavy-haul train on the Shuo-Huang Railway. An air brake system model was developed and coupled with a longitudinal train dynamics model, and simulations were conducted under different recharge durations using actual route and vehicle parameters. The results show that shorter recharge durations significantly reduce brake cylinder pressure and total braking force. When the recharge duration decreases from 320 s to 230 s, the braking distance on a 10.2‰ downhill increases by 6.981 km. In addition, insufficient recharge weakens quick-release functionality and leads to release signal interruptions. However, shorter recharge durations reduce longitudinal in-train forces during release, improving dynamic stability. These findings reveal a trade-off between braking effectiveness and in-train force levels, providing quantitative guidance for optimizing cyclic braking strategies in heavy-haul operations.