To apply the lean-burn technique to real engines two problems must solved; these are the substantial decrease in the burning velocity and the great increase in misfires as the mixture is thinned to the required extent which is near or beyond the flammability limit of the mixture. This paper shows that adding a small amount of hydrogen to the lean hydrocarbon/air mixture can increase its turbulent burning velocity substantially and extend its quenching limit greatly, thus being able to solve the above two problems at the same time. Improvement in the combustion performance by hydrogen addition is attributed to the preferential diffusion of hydrogen to the flamelets convex to the unburned side to increase their local heat release rate by enriching the local mixture. Without extra-supply of hydrogen by preferential diffusion, convex flamelets of lean mixture would be quenched most readily because heat losses from them is more than from other flamelets.
Improvement of lean hydrocarbon mixtures combustion performance by hydrogen addition and its mechanisms
Verbesserung der Verbrennung magerer Kohlenwasserstoffgemische durch Wasserstoffbeimischung und ihr Mechanismus
1994
6 Seiten, 6 Bilder, 9 Quellen
Conference paper
English
Improving the combustion performance of lean hydrocarbon mixtures by hydrogen addition
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