An investigation of early flame propagation in a lean-burn SI IC engine using time-resolved OH-PLIF measurement

Abstract

This paper describes the ignition and early flame propagation in a high-tumble SI IC engine under super lean-burn condition (excess air ratio (λ) of 2.0). To elucidate the detail process, a high-tumble optically-accessible SI IC engine operating at super lean and stoichiometric conditions were diagnosed by time-resolved OH-PLIF measurements. The engine was operated 2000 rpm with a port fuel injection of isooctane. The cross-sectional imaging of OH distribution was achieved at 12 kHz resulting in a temporal resolution of 1° crank angle at 2000 rpm. The results show that the OH radical is generated without any heat release by the spark discharge during approximately 15 ° crank angle after ignition timing in the super-lean condition. The OH distribution of these crank angles are scatted into small islandlike areas, and then subsequent flame propagation occurs.