Spray combustion and soot formation characteristics of the acetone-butanol-ethanol/diesel blends under diesel engine-relevant conditions

The acetone-butanol-ethanol (ABE) is considered as a promising biofuel to partially substitute the diesel fuel. In this paper, the optical constant volume combustion chamber was used to record the chamber pressure, and measured the soot mass and distribution for ABE and diesel blends. Then, the CFD KIVA-3V code coupled with the CANTERA was used to simulate the formation and oxidation processes of soot during the spray combustion. In addition, the CFD simulation cases for pure diesel and ABE20 were comprehensively validated against the experimental data under different initial ambient oxygen concentrations. Finally, a series of CFD cases were performed to investigate the effects of different ABE/diesel blends (up to 50% by volume), different initial ambient temperatures (mimic the traditional combustion and low temperature combustion modes) and oxygen concentrations (represent the free, low and high EGR conditions) on the combustion and soot formation characteristics under the diesel engine-relevant conditions. The results indicated that with the increase of ABE ratio in the ABE/diesel blends, the combustion pressure and heat release rate decreased and the combustion phase was delayed, the combustion temperature distribution was more uniform, while the flame lift-off length was increased gradually. In addition, the soot mass was decreased and its corresponding generation rate was also decreased with increasing the ABE ratio in blends. Furthermore, high concentration of soot mainly distributed in the temperature range of 1800-2000 K and the equivalent ratio range of 1.8-2.0.