An analysis of engine nacelle compartment leak and explosion hazards for a hydrogen-fuelled aircraft

Abstract

The introduction of hydrogen as a fuel source in aircraft poses significant design and safety challenges, particularly regarding the consequences of hydrogen leaks in confined engine nacelle compartments. This study presents a detailed CFD-based analysis of hydrogen leak dispersion and explosion hazards in a simplified annular nacelle geometry, addressing a critical gap in aviation safety knowledge. STAR-CCM+ was used to simulate hydrogen dispersion, examining the influence of leak location, orientation, mass flow rate, and ventilation rate on the formation of flammable gas regions. FLACS-CFD was employed to predict explosion overpressures resulting from ignition of stoichiometric hydrogen-air mixtures. The work provides original contributions to hydrogen safety in aviation by quantifying tolerable leak limits and ventilation requirements, demonstrating that air-based ventilation alone may be insufficient for managing larger leaks. The results show that even small hydrogen leaks (> 0.1 g/s) can form flammable clouds capable of producing hazardous overpressures, especially under turbulent or congested conditions. Explosion simulations revealed that a 1 g stoichiometric (29.5% v/v) hydrogen-air cloud (occupying ∼1% of the 3.8 m3 compartment volume) can exceed tolerable overpressure thresholds (> 0.1 barg) unless large pressure relief vents are used. The potential impact of the findings is to offer guidance for the safety design, certification, and regulatory development of future hydrogen-fuelled aircraft engine powerplants.