Super Lean-burn in SI Engine and Fundamental Combustion Studies

Abstract

One of the possible methods for the improvement of thermal efficiency in SI Engine is fuel lean combustion. It contributes to the increase of the mixture specific heat ratio and the decrease of the net heat loss to the engine cylinder through low temperature combustion, in which both of them lead to the higher thermal efficiency. At first, this article introduces the latest study which attempts to increase the thermal efficiency of an SI engine through super-lean burn concept. After identifying the relevant combustion fundamentals required for establishing super lean-burn concept, fundamental studies which report the minimum ignition energy (MIE) transition and initial spherical flame propagations at different Lewis numbers are introduced. Then, some similarities between super lean-burn SI engine experiments and fundamental findings are discussed in terms of ignition enhancement at super lean conditions. Finally, possible correlations between the specific flame growth from small ignition kernel to flame propagations sensitive to the mixture Lewis numbers and elongated arc channel for the effective ignition of lean burn condition are discussed.