Review on fundamental combustion parameters of cryogenic fuel systems: Measurement techniques and experimental challenges

Cryogenic systems are gaining increasing industrial relevance as decarbonization strategies promote the use of low-carbon energy carriers with very low normal boiling points. Their storage and transportation therefore require cryogenic conditions, introducing distinct safety and material challenges. Extremely low temperatures significantly alter thermophysical properties and reduce mechanical integrity, increasing susceptibility to brittle fracture and accidental release. In addition to direct cryogenic injury hazards, accidental releases may lead to severe fire and explosion scenarios, including flash fires, jet fires, vapor cloud explosions, pool fires, and boiling liquid expanding vapor explosions. Existing consequence assessment correlations have largely been developed for conventional fuels at ambient conditions and may not be directly applicable under cryogenic regimes due to strong temperature-dependent variations in density, viscosity, diffusivity, and heat capacity. Within this context, the experimental determination of fundamental combustion parameters such as the laminar burning velocity (LBV), flammability limits, and the minimum ignition energy (MIE) becomes essential. The LBV represents an intrinsic measure of mixture reactivity and plays a key role in assessing flame stability, ignition sensitivity, and explosion severity. This work systematically reviews established LBV measurement techniques and evaluates their suitability for low-temperature operation. Particular emphasis is placed on thermal management strategies and methodological limitations under cryogenic boundary conditions. Among the investigated approaches, the heat flux burner concept appears especially promising. In addition, experimental systems for determining the MIE at reduced temperatures are analyzed. Overall, the study highlights the necessity of specifically adapted experimental methodologies to ensure reliable safety parameters for cryogenic fuel systems.