Use of hydrous ABE-glycerin-diesel microemulsions in a nonroad diesel engine – Performance and unignorable emissions

Oversupply, extra energy consumption, and CO₂ emissions from the refinery of biodiesel-derived glycerin (G) led to the consideration of its use as an alternative fuel. In this study, a nonroad diesel engine generator was employed to represent potential emissions under stringent regulated standards. G-diesel has been reported to reduce nitrogen oxides (NOx) and soot levels but increase CO and hydrocarbon emissions. A bio-producible acetone-butanol-ethanol (ABE) solution with multiple polarities was added to stabilize the glycerin and water in diesel examined in this study. A series of ABE-G-diesel blends were prepared to form the thermostable microemulsions. Four blends with small and well-dispersed bubbles were tested in the engine generator. The specific thermal efficiencies of the engine were slightly improved by using ABE-G from regular diesel due to better spray quality, longer ignition delay, and fuel-oxygen content that would enhance combustion. Meanwhile, the PM-NOx-CO emission trade-off in the previous study has been overcome by using ABE-G-diesel since the better fuel atomization and more premixed combustion were approached, as well as the lower and homogeneous in-cylinder temperature caused by water content and micro-explosion. However, the condensable particulate matter and nitro-PAHs were also observed and realized their unignorable contribution, which has not been regulated and even researched for the generators. Fortunately, the new fuels could inhibit both of them to a certain degree. Consequently, this study proposes using recyclable glycerin with a simple pretreatment mixed with ABE and diesel for greener nonroad diesel engine especially those equipped with low-grade aftertreatment.