濃度分布を有する混合気流の着火特性 [in Japanese] Ignition Characteristics of the Mixture Flow with Concentration Distribution [in Japanese]
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Experimental study was conducted to investigate the effects of concentration distribution, namely, nonuniformity of concentration, in the mixture flow on the minimum ignition energy, E_<min>. Two different types of concentration distributions were examined in this study; two-dimensional distribution with a rectangular burner and axisymmetric distribution with a double circular tube burner. Measurements of E_<min> by the electrical spark were made for methane/air and propane/air mixtures and the relationship between E_<min> and the equivalence ratio at the ignition position, φ, was shown with the equivalence ratio gradient, G_φ, as the parameter, where G_φ was the index of nonuniformity of concentration. Results obtained were qualitatively similar between the two kinds of mixtures and summarized as follows: (1) In the case of two-dimensional distribution, E_<min> vs. φ relationship always shifts to the leaner side with the increase in G_φ. In the case of axisymmetric distribution, on the other hand, this relationship shifts to the richer side when the distribution curve is convex and shifts to the leaner side when the curve is concave as G_φ is increased. These ignition characteristics can be explained by considering that the sigh of ditribution curve curvature and the largeness of G_φ affect the direction of diffusion and the mass transfer rate due to diffusion of fuel and oxygen and change the equivalence ratio of the mixture transferred to the flame kernel after ignition. (2) Th increase in G_φ narrows the region where the flame can easily propagate and therefore makes ignition more difficult, leading to the increase in the minimum value of E_<min>.
- Transactions of the Japan Society of Mechanical Engineers. Series B.
Transactions of the Japan Society of Mechanical Engineers. Series B. 71(705), 1490-1496, 2005-05-25
The Japan Society of Mechanical Engineers