Structure of igniting ethanol and n-heptane spray flames with and without swirl

This paper explores the ignition and subsequent evolution of spray flames in a bluff-body configuration with and without swirl. Ethanol and n-heptane are used to compare the effects of volatility. Ignition is performed by a laser spark. High speed imaging of OH*-chemiluminescence and OH-PLIF collected at 5 kHz are used to investigate the behaviour of the flames during the first stages of ignition and the stable flame structure following ignition. Swirl induces a wider and shorter flame, precession, and multiple reaction zones, while the non-swirling flames have a simpler structure. The reaction fronts seem thinner with ethanol than with heptane. The dataset can be used for model validation.

► Spark ignition of swirling flames by laser shows timescales of successful and failed sparks.
► Ethanol and n-heptane flames show different reaction fronts.
► Fast-response OH-PLIF system reveals flame evolution from ignition to complete flame establishment.