Application of TNT equivalent model to vented explosions in combustion chambers. Validation with CFD simulations

Combustion chambers are common equipment used in many industries to retrieve heat from fuels (such as in boilers, furnaces, and other fired heaters). Despite the well-documented explosion hazards associated with this equipment, accidents continue to be reported periodically in industry. Risk assessments should therefore account for these hazards, given their potential to cause severe consequences and trigger domino effects. When explosion relief panels are present, the the pressure effects outside the enclosure can be complex and challenging to estimate. Effective plant layout design should also consider vulnerable elements located within the vented explosion’s impact zone. This study evaluates the applicability of the TNT-equivalent model for estimating the consequences of vented explosions in combustion chambers. A total of ten Computational Fluid Dynamics (CFD) explosion simulations were performed using FLACS and compared with TNT-equivalent model predictions. A strong correlation was observed, and adjusted yield factor correlations were developed specifically for vented combustion chamber explosions. These correlations enable worst-case overpressure estimation based on chamber volume and fuel characteristics. The results demonstrate that the proposed methodology can support key engineering tasks, including the optimal placement of vent panels, definition of safety distances, evaluation of explosion consequences and domino effects in risk analysis, plant layout decisions, and retrofitting existing equipment through a better understanding of explosion effects. • A new three-section TNT-equivalent model is developed for vented gas explosions. • Yield factors are correlated with fuel reactivity and enclosure energy content. • Model validated with FLACS CFD across five furnace geometries and two fuel gases. • The method enables accurate overpressure prediction for design and QRA purposes. • Applicable to industrial reboilers, fired heaters and SMRs with vented enclosures.