Numerical study on smoke spread characteristics of metro carriage fires with lateral multi-openings

Urban rail transit system has emerged as a critical urban lifeline project, while the fire risks it confronts are progressively on the rise. The lateral multi-opening structure of metro train carriages, in conjunction with the interval tunnel, forms a common yet distinctive double-narrow confined space. As important parameters for metro fire hazard assessment, the applicability of models for smoke spread velocity, maximum ceiling temperature rise, and longitudinal distribution of smoke temperature established based on single narrow tunnel or building corridor fire scenarios needs further verification in metro carriage fires. Therefore, this paper employs the method of numerical simulation to investigate the smoke spreading process and temperature distribution characteristics within train carriage and metro tunnel under different fire scenarios. The prediction models concerning the smoke spreading velocity in train carriages and metro tunnels have been developed. The impacts of fire source location, heat release rate, and ventilation velocity on the smoke temperature distribution characteristics have been examined. The prediction models for the maximum ceiling temperature rise and non-dimensional longitudinal temperature distribution of train carriages and metro tunnels have been established, and the accuracies of these prediction models have been validated. This research can enhance and refine the metro system fire safety theory, and provide theoretical and technical support for risk prevention and emergency management in such metro fire scenarios.