Comparison of explosion models for detonation onset estimation in large-scale unconfined vapor clouds

Although industrial denotations in semi-open and congested geometries are often neglected by many practitioners during risk assessment, recent studies have shown that industrial detonations might be more common than previously believed. Therefore, from the explosion safety perspective, it becomes imperative to better assess industrial detonation hazards to improve robustness of explosion mitigation design, emergency response procedures, and building siting evaluation. Having that in mind, this study aims to review current empirical vapor cloud explosion models, understand their limitations, and assess their capability to indicate detonation onset for elongated vapor clouds. Six models were evaluated in total: TNO Multi-Energy, Baker-Strehlow-Tang (BST), Congestion Assessment Method (CAM), Quest Model for Estimation of Flame Speed (QMEFS), Primary Explosion Site (PES), and Confinement Specific Correlation (CSC). Model estimations were compared with large-scale test data available in the open literature. The CAM model demonstrated good performance in indicating deflagration-to-detonation transition (DDT) for test conditions experiencing detonation onset without any modification in the methodology. Some suggestions are provided to improve simulation results from PES, BST and QMEFS.