Description
The Tunnel Ventilation System (TVS) is critical for providing acceptable and safe conditions in underground mass rapid transit systems. It maintains acceptable air temperature during normal and congested operations and controls smoke spread in the event of a fire, facilitating passenger evacuation. Various ventilation schemes are typically utilised in different sections of the tunnels. The upcoming Cross Island Line (CRL) in Singapore is set to implement the longitudinal and fully transverse ventilation systems for the main tunnels and trackway respectively.
In Singapore’s hot tropical climate, preventing excessive tunnel air temperature rise during congestion operation is crucial to avoid potential unloading or tripping of the train air-conditioning units. The eight-car configuration and rooftop air-conditioning (A/C) units of the CRL trains present an additional challenge. Traditionally, tunnel ventilation fans (TVFs) supply outdoor air directly to the tunnels via tunnel track dampers. However, this conventional method requires very large capacity TVFs to meet the air demand for temperature control. To address this, the use of nozzles to supply outdoor air to the tunnel was studied and compared with the conventional method.
The effectiveness of using the TVFs to extract smoke through the Over Track Exhaust Ducts (OTED) during a train fire at the platform was also examined and compared with the conventional extraction method.
The implementation of nozzles into the tunnel ventilation system was found to be effective, leading to a significant reduction in the required TVF capacity for temperature control. Additionally, extracting smoke during a train fire at the station platform via the OTED connected to the TVF helps to minimise smoke spillage into the station platform area.
