The Lean-Burn Limit Extending Experiment on Gasoline Engine with Dual Injection Strategy and High Power Ignition System

Abstract

In the context of the energy crisis and global warming, improving thermal efficiency is the most important issue in research on gasoline engines, and lean mixture combustion strategy is becoming the most promising method. Thus, a high compression ratio, a high-power interval ignition system, and a stratified combustion scheme achieved via dual injection were novelly adopted in a single cylinder gasoline engine in this study. The results show that the lean combustion limit could be literally extended and improved thermal efficiency was observed under the ultra-lean condition. Meanwhile, reverse combustion performance trends were observed by altering the second injection proportion from 30% to 45% under the lean condition (λ = 1.6) and ultra-lean condition (λ = 1.9). This was related to a combustion velocity change caused by great concentration gradient at the middle and end combustion stage. Finally, according to research on the effects of altering the timing of the second injection, it is clear that the dual injection strategy is an ideal method for realizing operation under the lean condition (λ = 1.6). But for the operation under the ultra-lean condition (λ = 1.9), more injection times and suitable air flow organization are needed to enhance the robustness of mixture distribution.