Enhancing Ignition Probability via Controlled Fuel-Air Phasing in a Coaxial Air-Blast Atomizer Using Laser-Induced Spark

The probability of successful ignition kernel generation via laser-induced spark (LIS) depends not only on fuel type and ignition energy, but also on local flow field characteristics, spatial placement, and timing. Previous studies have highlighted the advantages of LIS for relight applications in aero engines. This work investigates a coaxial air-blast atomizer that has independently controlled air and fuel flow parameters, which are precisely timed, to study how temporal offsets affect atomization dynamics and ignition probability in near-stoichiometric kerosene–air mixtures. Experiments are conducted across air mass flow rates ranging from 10 to 20 g/min at different locations downstream of the injector tip. High-speed backlight imaging, particle image velocimetry (PIV), and OH* chemiluminescence are employed to characterize the near-nozzle behavior, droplet size distribution, flow dynamics, and ignition behavior. Preliminary results show that ignition probability significantly improves when the timing and location of the LIS are synchronized with the atomizing flow, primarily due to increased size and residence time of the ignition kernel, which further depends on the varying droplet size.