Effect of transport processes on ignition of stretched diffusion flames using laser spark

(2) For successful ignition, the ignition delay time decreases with increasing level of helium dilution, while the opposite is true with argon dilution - the experimental results correlated with the calculated results of the diffusion times with these two inert diluents, suggesting that the successful ignition and the ignition delay time is limited by the thermal diffusion time across the flammable layer in the counter-flow region, rather than resulting from the Lewis number effect.