Improving the combustion performance of lean hydrocarbon mixtures by hydrogen addition

Abstract To apply the lean-burn technique to real engines two problems must be solved; these are the substantial decrease in the burning velocity and the large increase in the misfire probability when the mixture is as lean as required for exhaust emission reduction and fuel economy improvement. This paper shows that adding a small amount of hydrogen to the lean hydrocarbon/air mixture can substantially increase its turbulent burning velocity and largely extend its quenching limit. Thus, it can solve the above two problems. Mechanisms for such effects of hydrogen addition are discussed qualitatively on the basis of preferential diffusion of hydrogen and other reactants.