Investigation of Auto-Ignition of a Pulsed Methane Jet in Vitiated Air Using High-Speed Imaging Techniques

摘要

An experimental arrangement for the investigation of auto-ignition of a pulsed CH_4 jet in a coflow of hot exhaust gas from a laminar lean premixed H_2/ air flame at atmospheric pressure is presented. The ignition events were captured by high-speed imaging of the OH~* chemiluminescence associated with the igniting flame kernels at a frame rate of 5 kHz. The flow-field characteristics were determined by high-speed particle image veloci-metry and Schlieren images. Furthermore, high-speed imaging of laser-induced fluorescence of OH was applied to visualize the exhaust gas flow and the ignition events. Auto-ignition was observed to occur at the periphery of the CH_4 jet with high reproduc-ibility in different runs concerning time and location. In each measurement run, several hundred consecutive single shot images were recorded from which sample images are presented. The main goals of the study are the presentation of the experimental arrangement and the high-speed measuring systems and a characterization of the auto-ignition events occurring in this system.