Lean Burn Performance of a Spark Ignition Engine with an Ethanol-Gasoline Dual Injection System

A spark ignition (SI) engine with an ethanol direct injection (EDI) and gasoline port injection (GPI) system has been studied quite recently. In order to investigate its application, experiments were carried out on a single-cylinder 250 cm(3) short stroke motorcycle SI engine, which is supplied with the ethanol gasoline dual injection system. Experimental findings have revealed that EDI helped increase the lean combustion limit owing to the combination effects of the dual injection and ethanol fuel. At the identical engine speed and load, the lean burn limit in the dual injection model was, on average, 0.2 times higher than that in the corresponding single GPI model. Increasing ethanol energy ratio (EER) gave rise to the increase in the lean burn limit; nevertheless, the increase rate began reducing when the EER was above 48% and 42% at 4000 and 3500 rpm, correspondingly. Subsequently, late ethanol direct injection (LEDI), following the intake valve closing slightly extended the lean burn limit, probably, owing to the unsatisfactory mixture quality. Early ethanol direct injection (EEDI) prior to the intake valve closing was more helpful in increasing lean burn limit as compared with the LEDI. Nonetheless, further advance of spark timing earlier than 35 crank angle degress before top dead center (CAD BTDC) in LEDI situation, in addition 30 CAD BTDC in EEDI situation, might lead to reduction of the lean burn limit.