Experimental investigation of biodiesel-isopropanol fueled diesel engine coupled with DOC-SCR aftertreatment: Combustion behavior and emission mitigation strategy

This study experimentally investigates the combined effects of biodiesel-isopropanol ternary blends integrated with Diesel Oxidation Catalyst (DOC) and Selective Catalytic Reduction (SCR) emission control technologies on the combustion behavior, performance characteristics, and tailpipe emissions of a DI compression-ignition engine. The engine was run at a constant speed of 1800 rpm across four different engine loads (5.49, 10.98, 16.48, and 21.97 Nm). Test fuels included neat diesel, B20 (80% diesel + 20% biodiesel), B20P5D75 (75% diesel + 20% biodiesel + 5% isopropanol), and B20P10D70 (10% isopropanol). While peak in-cylinder pressure and heat release rate raised with engine load, the addition of 10% isopropanol (B20P10D70) extended ID and shortened the combustion duration (CD) at low and medium loads. Regarding performance, the lower calorific value of the oxygenated blends led to a slight penalty in BTE, which decreased by 4.59% for B20P10D70 at 16.48 Nm according to neat diesel. However, the integration of isopropanol blends with the DOC-SCR system yielded substantial emission mitigation. Notably, the DOC highly promoted oxidation reactions, reducing CO emissions to levels below the detection limit (zero emissions) for B20P10D70 at 10.98 Nm, and for B20P5D75 at 16.48 and 21.97 Nm loads. Furthermore, isopropanol addition resulted in lower CO 2 concentrations under the tested operating conditions, while the SCR system provided a remarkable 47.05% reduction in NO x emissions at full load with the B20P10D70 blend. These findings demonstrate that utilizing isopropanol as a biodiesel co-solvent alongside DOC-SCR systems is a highly effective strategy for suppressing diesel engine emissions.