As the automotive industry transitions from internal combustion engines to electric vehicles, the need to find alternative renewable fuels for diesel engines that offer superior performance and lower emissions becomes increasingly important. Biogas and syngas, when combined with the Reactivity Controlled Compression Ignition (RCCI) strategy, offer significant potential as viable alternatives. This research examines the combustion char- acteristics of an RCCI engine equipped with both single-stage and two-stage diesel direct injection using computational fluid dynamics (CFD) simulations along with a detailed chemical kinetic mechanism. This paper presents a novel approach for blending two gases fuels to optimize their combined benefits, enhancing perfor- mance and efficiency compared to individual use of them as low reactive fuel. The study shows that a two-stage direct diesel injection configuration using a low-reactivity mixture of 25 % biogas and 75 % syngas with 60 % of the diesel injected in the first stage is the optimal setup to prevent engine knock. This configuration leads to a significant reduction in CO emissions of 71.07 %, while NOx and formaldehyde emissions are reduced by 25.2 % and 73.29 %, respectively. In addition, greenhouse gas emissions (CO2, CH4 and N2O) are reduced by 41.83 % compared to conventional diesel operation. Notably, performance metrics such as power and torque show an increase of 6.21 % compared to conventional diesel operation. These results highlight the potential of biogas and syngas RCCI engines to change the diesel landscape by providing a bio-renewable alternative without sacrificing performance.

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