Advanced Fire Engineering Tool for Integrated Analysis of Structural Design Parameters

Hydrogen fuel cell vehicles (HFCVs) have garnered widespread attention in recent years owing to their zero emissions and contribution to sustainable transportation. Despite their promising attributions, HFCVs still can present certain hazards and challenges due to the unique characteristics of hydrogen. To minimize the risk of hazards, a thermal pressure relief device (TPRD) mounted on the HFCV is designed to clear the hydrogen storage tank when the surrounding temperature is 110 ℃. However, the TPRD may not be activated even if a fire occurs in an HFCV. In terms of the TPRD activation state, two accident scenarios are regarded in this study - the HFCV fire involving the hydrogen jet fire when the TPRD works and the hydrogen tank rupture triggered by the HFCV fire when the TPRD does not work.

In this thesis, a hydrogen jet fire model is developed in the Fire Dynamic Simulator (FDS) by introducing high-speed Lagrangian particles released from a virtual nozzle. To investigate the influences of FDS parameters on the gas temperature within the hydrogen jet fire model, a sensitivity analysis is conducted with seven FDS parameters, e.g., the vertical height of a spontaneously ignited volume (AEZ), particle insertion offset (OF), particle count (PPS), mesh size, initial droplet velocity (PV), auto-ignition temperature (AIT), and spray angle (SA). The analysis reveals that mesh resolution is the dominant factor for simulating gas temperatures near the compartment ceiling in the FDS simulation. Furthermore, the particle insertion offset, particle count, and spray angle are critical for predicting gas temperature within the direct jet plume.

Subsequently, fire behaviors of concrete structures exposed to HFCV fires are studied through a one-way Computational Fluid Dynamics (CFD)-Finite Element Method (FEM) coupling interface, known as FDS2FTMI. The HFCV fires consisting of hydrogen jet fires and HFCV body fires in a semi-open concrete car park are analyzed in FDS, in which the hydrogen jet fire adopts the developed FDS model, and the HFCV main body fire is modeled by prescribing the heat release rate per unit area on a surface of a solid obstruction. A thermal analysis of a concrete ceiling in a car park is conducted in ANSYS Mechanical APDL. In this study, two parameters including four diameters of the TPRD nozzle and three fire spread times of the HFCV body are taken into account. The simulation results indicate that the maximum temperature of the concrete surface is significantly affected by the TPRD nozzle diameters; a larger TPRD nozzle diameter results in a higher concrete surface temperature. Moreover, the TPRD nozzle diameter has a more substantial influence on the concrete strength than the fire spread time.

In the event of a hydrogen tank rupture in a tunnel, the mechanical behaviors of a tunnel reinforcement concrete (RC) ceiling slab are studied in ANSYS Mechanical APDL and DIANA, through manual CFD-FEM coupling. In the coupling process, the pressure histories are manually extracted from CFD analysis and applied to FEM analysis. Four parameters comprising concrete strength, rebar diameter, constraint conditions, and impulse are considered to investigate the dynamic responses of an RC slab in different FEM software. The results demonstrate that the deflection of the RC slab is significantly influenced by the explosion impulse, rebar diameters, and constraint conditions. Furthermore, a static analysis of the RC structure is conducted in ANSYS and DIANA. This analysis aims to explore modeling issues of RC structures, focused on material models, mesh sizes, and solution methods. The findings from this exploration provide guidance for the simulation of RC structures.