LES of Turbulent Under-expanded Hydrogen Jet Flames

In the frame of hydrogen-powered aircraft, Airbus wants to understand all the H2 physics and explore every scenario in order to develop and manufacture safe products operated in a safe environment. Within the framework of a Large Eddy Simulation (LES) methodology for modeling turbulence, a comparative numerical study of free under-expanded jet H2/AIR flame is conducted. The investigated geometry consists of straight nozzles with a millimetric diameter fed with pure H2 at upstream pressures ranging from 2 to 10 bar. Numerical results are compared with available experimental measurements such as; temperature signals using thermocouples. LES confirms its prediction capability in terms of shock jet structure and flame length. A particular attention is paid for capturing experimental unstable flame when upstream pressure decreases. Furthermore, flame stabilization and flame anchoring are analyzed. Mechanisms of flame stabilization are highlighted for case 1 and stabilization criteria are tested. Finally an ignition map to reach flame stabilization is proposed for each case regarding the literature.