炭化水素微小球状伝ぱ層流火炎の基礎燃焼速度特性に関する実験的検討

概要

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Understanding of the burning velocity for micro-scale flames is inevitable in the improved design of micro-combustors for miniaturized power supplies, and also useful for modeling local burning characteristics of turbulent flames. The present study is performed to examine experimentally the burning velocity characteristics of micro-scale spherical laminar flames in the range of flame radius rf approximately from 1 to 5 mm for methane and propane mixtures as hydrocarbon fuel, and also macro-scale laminar flames with rf >7 mm for comparison. The mixtures have nearly the same laminar burning velocity at so-called unstretched flames and different equivalence ratio φ (φ=0.8-1.0 for CH4, φ=1.0-1.4 for C3H8). The radius and the burning velocity of micro-scale flames are obtained by using sequential schlieren images recorded under appropriate ignition conditions. It is found that the burning velocity of all micro-scale flames has a tendency to increase with increasing rf , and approach that of macro-scale flames. The propane mixture with φ1.4 , however, shows that the burning velocity of micro-scale flames can not be explained based on that of macro-scale flames. This suggests that the optimum size and Karlovitz number to improve the burning velocity are existed, depending on φ and fuel types.