Emission Characteristics of Oxygenated Diesel Blends Under Varying Engine Speeds

Abstract

This study investigates the exhaust emission characteristics of various oxygenated diesel blends under different engine speeds and high engine loads. The primary emissions analyzed include carbon dioxide (CO₂), carbon monoxide (CO), and nitrogen oxides (NOₓ), which are key indicators of combustion quality and environmental impact. Experimental tests were performed using pure diesel and its blends with turpentine, alpha-pinene, and oxygenated additives. The results revealed that CO₂ emissions increased with engine speed for all fuels, peaking at 2,400 rpm, where the highest CO₂ level recorded was approximately 11.2% for the APD blend. Notably, the OAPD blend showed the lowest CO₂ emissions across all speeds, indicating less efficient combustion. CO emissions also rose with engine speed, reaching a maximum of 0.65% for diesel at 2,400 rpm. However, the use of oxygenated blends significantly reduced CO emissions—by 0.44% for OTD, and 28.3% for both APD and OAPD—due to improved atomization and fuel-air mixing. NOₓ emissions also increased with engine speed, from 86 ppm at 1,200 rpm to 238 ppm at 2,400 rpm. Blends with turpentine and alpha-pinene exhibited higher NOₓ levels compared to diesel, due to greater premixed combustion and higher in-cylinder peak temperatures. Overall, the findings suggest that oxygenated additives can effectively reduce CO emissions but may increase NOₓ levels, highlighting a trade-off in emission behaviors that must be considered when developing cleaner alternative fuels.