Air quality on trains – aerodynamic interactions of exhaust and HVAC systems

Air quality is known to have significant health impacts from both short- and long-term exposure. As a significant contributor, the transport sector is working to reduce its adverse impact; however, the impact of rail transport on air quality at local levels, particularly within enclosed spaces (e.g. stations and onboard trains), is still not fully understood. With  30% of rail traction diesel-powered, previously studies have shown that in certain conditions pollution concentrations exceed prescribed EU limits in enclosed stations. Although these studies offer insight into issues at particular strategic locations, there have been none which address issues and identify mitigation measures to risks associated with poor air quality for both passengers and train crews onboard trains for typical journeys. This seminar will present work conducted as part of the Rail Safety and Standards Board (RSSB) Clean Air Research programme on project “T1234 Air Quality on Trains - HVAC and Exhaust Interactions Study”, which focused on providing better understanding of rail’s direct contribution to air pollution onboard trains. The project aimed to determine how exhaust emissions and heating, ventilation, and air conditioning (HVAC) systems interact and impact levels of air pollution onboard passenger trains, establishing factors that can be changed to improve air quality. The programme covered a wide range of techniques, from computational studies through to model- and full- experimental validation. Findings indicated that the design configuration of train roofs were particularly important when considering the interaction of exhaust gases with HVAC systems and that simple alterations in design and shape of the roof and exhaust pipe, as well as the HVAC placement and operation could lead to large improvements in onboard air quality