Flame Characteristics of Ignited under-expanded Cryogenic Hydrogen Jets

The anticipated upscaling of hydrogen energy applications will involve the storage and transport of hydrogen in a cryogenic state. Understanding the potential hazard arising from small leaks in pressurized storage and transport systems is needed to assist safety analysis and development of mitigation measures. The current knowledge of the ignited pressurized cryogenic hydrogen jet flame is limited. Large eddy simulation (LES) with detailed hydrogen chemistry is applied for the reacting flow. The effects of ignition locations are considered and the initial development of the transient flame kernel from the ignition hot spots is analysed. The flame structures, namely side flames and envelop flames are observed in the study, which are due to the complex interactions between turbulence, fuel-air mixing at cryogenic temperature, and chemical reactions.