ABSTRAKT

The aim of this work is the comparative study of the self-ignition of hydrogen and methane- hydrogen mixture supersonic jets in vitiated confined supersonic airflow. Self-ignition in this configuration was studied by one of the authors in the ONERA's LAERTE test facility designed for the fundamental study of supersonic combustion. The data, that were collected in the combustor are used to validate LES simulations. Planar Laser Induced Fluorescence (PLIF) measurements of the hydroxyl radical were performed to detect the flame structure. The images showed that self-ignition appears in small-scale pockets (spots), comprising fuel and hot air, and randomly distributed in the air-fuel mixing layer. It is concluded that the self-ignition delay lengths cannot be predicted from delay induction times for homogeneous mixtures, because of large effect of turbulent mixing on the preignition chemistry in the pockets. LES subgrid mixing model is developed to reproduce the observed experimental data.