In this study, the effects of safflower and sunflower biodiesel blends (B10 and B20) on diesel engine performance, combustion characteristics, and exhaust emissions were experimentally investigated, together with the catalytic performance of a diesel oxidation catalyst (DOC) and a selective catalytic reduction (SCR) system. Biodiesel was produced via transesterification and blended volumetrically with diesel fuel. Experiments were conducted on a single cylinder, direct injection, naturally aspirated diesel engine under full load conditions across an engine speed range of 1200 to 2800 rpm. Engine torque, brake power, brake specific fuel consumption (BSFC), in cylinder pressure, heat release rate (HRR), exhaust gas temperature (EGT), and regulated emissions including CO, HC, and NOx were analyzed. The overall experimental uncertainty of the measurement system was determined as 1.93% using the root sum square propagation method. Increasing biodiesel content led to slight reductions in engine performance due to lower heating value and altered spray characteristics. Compared to diesel, torque decreased by 1.80% and 3.24%, brake power by 0.62% and 1.75%, and BSFC increased by 2.91% and 6.14% for B10 and B20, respectively. Biodiesel blends reduced CO and HC emissions, with the DOC achieving conversion efficiencies exceeding 97% at engine speeds above 2000 rpm. Although biodiesel use alone increased NOx emissions, integration of the SCR system significantly enhanced emission control. At 2400 rpm, NOx conversion efficiencies reached 71.4%, 89.4%, and 93.1% for diesel, B10, and B20, respectively. EGT measurements confirmed that the progressive rise in SCR catalyst inlet temperature with increasing engine speed is the primary thermal mechanism governing speed dependent NOx conversion efficiency.
Horoz et al. (2026) studied this question.