Abstract
A flame propagation in the vortex flow in a meso-scale, 10-mm tube has been experimentally investigated using N_2, Ar, He, and CO_2 as diluents. Methane was used as fuel. Results show that, the flame propagation range of Ar- and N_2-dilution is almost the same as their flammability range. However, the propagation range of He-dilution is considerably narrower, whereas the range of CO_2-dilution is wider than their flammability range. These results indicate that the flame can propagate beyond the flammability limits when Lewis number is less than unity, whereas the flame cannot propagate even in the flammability range when Lewis number is greater than unity.
