Operation Range Extension of Homogeneous Charge Compression Ignited Small-Bore Off-Road Diesel Engine Using Acetone-Gasoline Blends

The Homogeneous Charge Compression Ignition (HCCI) combustion eliminates the issues of higher particulate matter and nitrogen oxides emissions that prevail in the traditional compression ignition (CI) combustion mode. The complete replacement of traditional fuels with renewable fuels for internal combustion engines is challenging because significant infrastructure changes in the production and delivery systems are required to ensure renewable fuel availability and economic feasibility. Thus, the use of renewable acetone blended with traditional gasoline has been proposed in the present study to smoothen the transition from the traditional CI to the HCCI engines. HCCI experiments were performed in a light-duty diesel engine at 1500 rpm rated speed. By varying the volumetric proportion of the acetone in the gasoline from 20% to 40%, the HCCI engine load range from 20%-60% was achieved, significantly higher than the limited diesel HCCI load range of 20%-38%. An ignition-quality enhancer, 2-Ethylhexyl nitrate, at 6 vol.%, was blended in the acetone-gasoline to prevent the higher cyclic IMEP fluctuations at the lower engine loads. The empirical correlation of the start of combustion (CA10) established on a rapid compression machine facility was validated for the HCCI engine. The combustion phasing (CA50) was predicted using CA10 and fresh air equivalence ratio. A double-Weibe function was developed to characterize specifically the high-temperature heat release rate during the HCCI combustion and determine the extent of its fast-burning core region. An in-depth energy balance study was conducted to elucidate the reason for the indicated thermal efficiency trends. The acetone-gasoline-fuelled HCCI engine generated smoke and nitrogen oxides emissions that were less than 0.0007 g/kW-h and 2.5 g/kW-h, respectively, at all the engine loads. This study concluded that lower exhaust emissions could be obtained without compromising engine performance when the acetone-gasoline blends are used as fuels for operating the HCCI engine.