Effect of Personalized Ventilation in Seat Armrest on Diffusion Characteristics of Respiratory Pollutants in Train Carriages

As one of the most important means of transportation, high-speed trains have a large capacity for carrying passengers. However, their narrow carriages can easily exacerbate the spread of respiratory diseases. Just like personalized ventilation in an airplane, ventilation in seat armrests of high-speed trains may increase comfort for passengers, but also influence the diffusion characteristics of respiratory pollutants. In this study, the effect of personalized ventilation in seat armrests, on the diffusion characteristics of respiratory pollutants in train carriages, is studied by means of the tracer gas method. Taking the ceiling air supply as the original ventilation system, comfortable temperature and pollutant diffusion characteristics of the personalized ventilation system, with 4 different air supply angles, are investigated. The 4 angles are 0°, 30°, 45° and 60°.  When the personalized ventilation with the above 4 angles is adopted, the fluctuation amplitudes of pollutants in the passenger breathing zone are reduced by 15.84%, 19.27%, 19.76% and 19.68%, respectively, compared with the original ventilation system. It indicates that the sensible use of personalized ventilation can effectively reduce the passengers’ contaminant concentrations in the breathing zone, thereby reducing the possibility of cross-contamination between passengers. In addition, the use of the personalized ventilation system leads to a slight improvement in the thermal comfort and flow uniformity in the carriage. Based on the results, personalized air supply with an angle of 45° is advised for use in high-speed trains.