An Investigation of the Replacement of E10, E85, and Methane with Gasoline in Reactivity Controlled Compression Ignition Combustion: A Comparison of Alternative Fuels Using Reactivity Controlled Compression Ignition Strategy

The Reactivity Controlled Compression Ignition (RCCI) strategy is a novel Low-Temperature Combustion (LTC) strategy that is used to minimize nitrogen oxides (NO_X) and soot emissions to near zero. Methane and ethanol blends are the most conventional alternatives to gasoline used in the RCCI strategy. In this paper, a three-dimensional Computational Fluid Dynamics (3D-CFD) model was developed and validated against the experimental data at the load of 6.5 bar Indicated Mean Effective Pressure (IMEP) and 1300 rpm. E10, E85, and methane were replaced with gasoline to investigate their effects on emissions and performance. In order to make a fair comparison between cases, combustion phasing (CA50) and cylinder energy and boundary conditions were considered constant. Conventional Diesel Combustion (CDC) was also investigated with the constant cylinder energy to make a comparison between all RCCI cases and CDC. Adding ethanol in gasoline showed that it can increase the gross thermal efficiency (GTE) up to 1.3%, but at the expense of higher fuel consumption. Ethanol fraction resulted in better fuel oxidization, and lower unburned hydrocarbon (UHC) and carbon monoxide (CO). The methane/diesel RCCI case had lower GTE compared to other RCCI cases, but it still showed higher GTE than CDC. One of the main drawbacks of the methane/diesel RCCI case was the high levels of UHC and CO, but fuel consumption was lower than gasoline/diesel RCCI. From the emissions standpoint, all RCCI cases managed to meet EURO6 and EPA2010 emission mandates for NO_X, soot, and CO. However, it is impossible for the CDC strategy to meet these regulations without adopting aftertreatments. The CDC strategy had about 98% of the total produced NO_X and soot in all cases. On the other hand, 63% and 51% of the total produced UHC and CO belonged to the methane/diesel case. From the global warming concerns and carbon dioxide (CO₂) perspective, the CDC case produced 547.1 g/kW-h CO₂ while the methane case produced 350.9 g/kW-h CO₂. Other cases (gasoline, E10, and E85) showed middle levels of CO₂ by about 460 g/kW-h.