ボルテックスバースティングによる細管内の火炎伝播に関する実験的研究(熱工学,内燃機関,動力など)

Abstract

Flame propagation in a small diameter tube has been experimentally investigated. Methane/air and propane/air mixtures were injected into the small diameter tube from a swirl generator installed at one end of the tube, ignited at the other open end, and the propagation limits have been determined as function of air flow rate and the mixture equivalence ratio. Results show that, when the tube inner diameter is greater than 3.6mm, flame through the vortex bursting mechanism become possible. An increase in the air flow rate leads to an increase of the propagation range in equivalence ratio, whereas a decrease in the air flow rate leads to a decrease of the propagation range, and eventually a flame cannot propagate upstream for any equivalence ratio of the mixture. Further experiments have showed that, as the swirl intensity is increased, flame propagation range becomes widened in the mapping of the equivalence ratio and the air flow rate. The range of equivalence ratio Φ for which the flame propagation due to vortex bursting becomes possible is on relatively fuel lean side between 0.75 and 1.1 for methane/air mixtures, whereas the range is quite limited on very fuel rich side between 1.1 and 2.2 for propane/air mixture. These ranges are much narrower than those for the vortex induced flame propagation in an open air or in a very large diameter tube, suggesting strong influence of the Lewis number of a deficient species for the occurrence of vortex induced flame propagation in a small diameter tube.