The demand for fossil fuels can be reduced and environmental harm can be
minimized by producing biodiesel from used cooking oil. This article was focused
on investigating the combustion characteristics and regulated and unregulated
emissions of a common-rail diesel engine fueled with different mixed
concentrations of biodiesel and diesel fuel, including pure diesel fuel (B0),
B10 (diesel containing 10%vol of biodiesel), B20, and B30. Experiments were
conducted with three engine loads, corresponding to brake mean effective
pressures (BMEP) of 0.289 MPa, 0.578 MPa, and 0.867 MPa at a constant speed of
1540 rpm. At medium and high loads, the waste cooking oil biodiesel (WCOB)
increased in-cylinder pressure, advanced both the peak heat release rate and
heat release center (CA50), shrunk the ignition delay (ID), and extended
combustion duration (CD). The high viscosity of B30 blends under low load
worsened the spray and led to poor combustion. Under high-load conditions,
carbon dioxide (CO2) and nitrogen oxides (NOx) emissions
increased by 14.3% and 3.1%, while carbon monoxide (CO), soot, and total
hydrocarbon (THC) emissions decreased by 13.3%, 31.4%, and 30.37%, respectively,
for the B30 blend compared to diesel. The emission trends for nitrogen dioxide
(NO2), formaldehyde (HCHO), methane (CH4), ammonia
(NH3), ethylene (C2H4), and
formic acid (HCOOH) were consistent with increasing volume ratios of WCOB under
the three loads. And they had the lowest emissions at 75% load for B30, with
reductions of 70.5%, 66.7%, 18.4%, 78.8%, 13.2%, and 84.6%, respectively,
compared to diesel. Acetaldehyde (MECHO) emissions increased with increasing
WCOB blending volume ratio at 25% load condition and were highest at the B30
blend. The above results show that the B30 blend is the most effective in
reducing unregulated emissions under all three load conditions, especially at
medium and high loads.
