Influence of train arrival characteristics on unorganized ventilation in underground subway station with platform screen doors

Unorganized ventilation significantly increases the energy consumption of subway stations. Many factors affect unorganized ventilation, and its variation is still not clear. This study established a validated network model using Subway Environment Simulation and developed two general scripts to investigate changes in the unorganized ventilation with varying train arrival characteristics, including the train arrival density and arrival time interval for two-side trains. Furthermore, the cooling load caused by the airflow was calculated. The results reveal that the train arrival density changes the superposition of the unorganized ventilation caused by the previous and next pairs of trains, and it also determines the location and state of the existing trains in the tunnel. That affects the unorganized ventilation in the station. The arrival time interval changes the "phase difference" of airflow generated by each side trains. The cooling load caused by unorganized ventilation is much larger than the current perception. Controlling the mechanical ventilation based on the unorganized ventilation rate and optimizing the arrival time interval can reduce the load markedly. Besides, low indoor temperature results in a significant increase in cooling load.