Study on air quality improvement in train compartments by coordinated exhaust of multiple air outlets

Abstract Ventilation is one of the most effective ways to improve the air quality in trains. Top exhaust and bottom exhaust are two commonly used modes. The study hopes to switch the exhaust mode to adapt to the indoor requirements of different scenes without changing the layout of the end pipe. In the study, the airflow characteristics, energy consumption, thermal comfort and air quality in the compartment are evaluated based on computational fluid dynamics. The results show that the energy consumption decreases with the increase of the top exhaust air volume in summer conditions, while the opposite is true in winter conditions. In terms of thermal comfort, combining top and bottom exhaust can effectively improve air speed index, temperature difference index and air diffusion performance index. In addition, the draft rate index and percent dissatisfied index are less than 10% and 3%, respectively, which meet the requirements of ISO 7730 standard. In terms of air quality, the average pollutant concentration inside the vehicle decreased, but the longitudinal penetration capacity of the pollutant has increased. The research results can provide some suggestions and help for the ventilation design of high-speed trains.