Impact of acetone-butanol-ethanol ternary fuel on combustion and emissions in a low-temperature combustion engine with variable compression ratio

Abstract

In this study, the use of acetone-butanol-ethanol ternary mixture fuel obtained as a result of fermentation in biobutanol production in a homogeneous charge compression ignition engine was experimentally investigated. The experiments were carried out at different lambda and compression ratio values. In order to make the comparative analysis correctly, the intake air inlet temperature was kept constant at 350 K and the engine speed was kept constant at 800 rpm, which is the widest operating range. The increase in the compression ratio provided low temperature combustion under leaner conditions. Thus, the operating range was extended towards lower loads. Compared to the reference neat n-heptane, as the ratio of unpurified ternary fuel in the blended fuels increased, the combustion was delayed, slowed down and could be controlled. In the use of ternary fuel, the high temperature oxidation zone shifted towards top dead center. In the use of ternary fuel, it was determined that the indicated thermal efficiency was above 40 % in almost all test conditions in the use of 60 % ternary fuel. The ternary test fuel containing unpurified butanol both reduced knocking and provided combustion at higher engine loads with its high octane number advantage. With the 40 % acetone-butanol-ethanol mixture fuel, combustion was achieved in the 3.00–6.25 bar engine load range, while with the 60 % mixture fuel, the load range expanded to the 4.00–7.25. Hydrocarbon and carbon monoxide emissions increased in the use of acetone-butanol-ethanol mixture fuels at low engine loads. Because at low engine loads, the end-of-combustion gas temperature decreased and oxidation reactions worsened. The results of this study reveal that compression ratio, fuel composition and lambda values have a great effect on the low-temperature combustion mode. The fuel reactivity, which decreases as the acetone-butanol-ethanol ratio in the mixture fuels increases, can be turned into an advantage with a high compression ratio.