Combined effects of intake flow and spark-plug location on flame development, combustion stability and end-gas autoignition for lean spark-ignition engine operation using E30 fuel

摘要

>Lean or dilute spark-ignition engine operation can provide efficiency improvements relative to that of traditional well-mixed stoichiometric spark-ignition operation. However, to maintain a sufficiently short burn duration with the direct-injection spark-ignition engine hardware of the current study, mixed-mode combustion is required for operation with???-sweeps. A high-octane E30 fuel is used here, and intake heating is used to promote both lean combustion stability and end-gas autoignition. The best lean combustion stability is found for the ALL Three spark strategy, followed by the East-West and Central spark strategies, enabling stable mixed-mode spark-ignition combustion for?down to 0.50 and 0.55, respectively. Here, operation without swirl provides the most stable combustion. High-speed imaging of ultra-lean operation without swirl at??=?0.55 using the East-West spark strategy reveals that the transition from deflagration to end-gas autoignition frequently occurs within the view offered by the small piston-bowl window. These results encourage future optical investigations of fuel effects on this transition process, but a larger piston-bowl window is recommended.]]>