The Effect of Spark Ignition on the CAI Combustion Operation

The present paper aims to investigate the influence of spark ignition on CAI combustion based on internal EGR strategy. Controlled Auto-ignition (CAI) combustion is facilitated in a Ricardo single cylinder engine with a pair of special camshafts, which valve lift and cam profile are modified to trap enough hot residuals.

Operation regions and other detailed combustion characteristics of the CAI engine operation are analyzed and compared between pure CAI mode and the CAI mode with assisted spark ignition.

The results show that spark ignition can play an important role in controlling CAI combustion ignition in low load boundary region. The low temperature chemical reaction process is shortened and the auto ignition timing is advanced due to the spark discharge. Meantime, lower fuel consumption and cycle-to-cycle variations can be achieved. The Spark discharge makes auto-ignition easier in low load boundary region, so that the CAI operation can be expanded to lower load through assisted spark ignition.

The primary results show the potential of spark ignition for control of auto-ignition timing and control of CAI/SI mode switch.