Performance, combustion, and emission characteristics of MTBE-enhanced diesel-canola biodiesel blends with DOC-SCR after-treatment: An experimental study

Canola oil biodiesel enhances combustion efficiency, while methyl tert-butyl ether (MTBE) improves the fuel’s vaporization properties and mixture homogeneity, providing a more controlled and balanced combustion character. Additionally, the combined use of diesel oxidation catalysts (DOC) and selective catalytic reduction (SCR) systems enables simultaneous reduction of pollutant emissions. In this study, the effects of ternary fuel blends consisting of diesel-canola oil biodiesel-MTBE used in conjunction with DOC and SCR exhaust gas reduction systems on the performance, combustion, and exhaust emission characteristics of a diesel engine were comprehensively investigated. The experiments were conducted at a constant engine speed of 1800 rpm and engine loads of 10.98, 16.48, 21.97, and 27.46 Nm using five different test fuels (Diesel, B30, B30MTBE5, B30MTBE10, and B30MTBE15). Combustion analyses revealed that the addition of MTBE limited the peak values of maximum cylinder pressure and heat release rate (HRR) and created a controlled delay at the CA10 and CA50 positions. Consequently, the extended combustion duration (CD) associated with biodiesel use was shortened by the MTBE additive, resulting in a smoother and more balanced combustion process. Acceptable combustion stability was achieved at low MTBE ratios, while cyclic variations increased at higher ratios. The B30MTBE15 blend achieved the lowest specific fuel consumption (SFC) of 226.79 g.kWh −1 and the highest thermal efficiency (TE) of 37.91% at an engine load of 21.97 Nm. Additionally, the B30MTBE15 blend reduced the maximum pressure rise rate (MPRR) by 28.24% and ringing intensity (RI) by 30.83% compared to diesel fuel. The emission results showed that carbon monoxide (CO) emissions were eliminated at the exhaust outlet, hydrocarbon (HC) emissions were reduced by up to 41.1%, and nitrogen oxides (NOx) emissions were reduced by up to 59.8% due to the integrated effect of MTBE addition and the DOC-SCR system. The findings indicate that ternary fuel blends containing diesel, canola oil biodiesel, and MTBE could be a low-emission, high-efficiency, and sustainable alternative for modern diesel engines.