Fire scenarios modelling for the safe design of a passenger rail carriage

Effective fire safety design of rail infrastructure is underpinned by application of realistic design fires representing credible train fire incidents. One of the many objectives for passenger train designers is to minimise both the probability of a large interior fire occurring and the maximum fire size and duration. However, current understanding of fire development in passenger train interiors is limited and existing methods for design fire estimation applied to trains are based on crude assumptions and, therefore, appropriate design fires for passenger trains are uncertain. In this paper a summary of the results of a research programme sponsored by the Italian national railways will be presented. The programme involves university as well as experimental laboratories and fire suppression systems manufacturing companies. The project is focused on the development of numerical tools for the reliable fire scenarios simulation and on the definitions of standards for the fire safety design of rail carriage. Cone calorimeter tests have been performed on typical materials that characterize a train fire scenario providing valuable data in terms of exhaust gases concentration, temperature and heat flux measurements. The experimental data have been used to validate the advanced design tools used by Trenitalia (CFD codes and correlative formulations). One of the main goal of the research is to define a reliable procedure for the design of a fire extinguish system for railway passenger train by the use of the code FDS (Fire Dynamics Simulator) developed by the NIST (National Institute of Standards and Technologies). In order to reach the programme objectives, several aspects have been deeply analysed. More in details attention has been paid on the combustion and pyrolysis modelling and a best practice for the evaluation of the solid fuel burning properties has been defined. In particular, a reliable procedure for the evaluation of the pyrolysis parameters required by the code FDS 4 has been selected and tested. The results are encouraging as the cone calorimeter experiments have been successfully replicated by the CFD. The defined methodologies are a potentially industrially useful contribution to rail infrastructure design.