Spatial and radiative characteristics of large scale hydrogen jet-fires

Hydrogen refuelling stations carry the risk of hydrogen leakage from flanges, holes, broken pipes, etc., and the possibility of ignition is high due to the low minimum ignition energy of hydrogen. The length of these hydrogen jet flames may have an impact on damage and should be included in risk assessments. The risk assessment of typical hydrogen refuelling infrastructure is highly dependent on separation distances. These distances are estimated partially by jet flame lengths. The use of reliable physical models, engineering models, and risk analysis tools is hence required for safely operating this infrastructure. Generally, the physical models are adapted from hydrocarbon fuels, and they have to be validated for hydrogen especially in the range of operating pressures of FCEVs and refuelling infrastructures. To fill this gap, large scale hydrogen jet-fires tests were conducted in open space at various hydrogen pressures (up to 450 bar) and orifice diameters (1-5 mm). The jets were visualized by a thermal camera (up to 2000°C) and radiation flux sensors facing the jet at different distances were located. Results showed that the hydrogen flames can cover distances of about tens meters, and cause life-threatening conditions by the flame itself and thermal radiation.