Investigation On The Effect Of EGR On Knocking Characteristics Of SI Engine Fuelled With N-butanol

Due to the finiteness of oil resources, the growth of energy consumption and the environment problems, the energy and environment situation are becoming more and more serious in China. Exploring new clean alternative fuels is of great significance to alleviate the current situation of energy shortage.Since the anti-detonating quality of n-butanol is good, the application of n-butanol on high compression ratio SI engine can obtain high thermal efficiency, but the engine knock tendency will also increase. EGR is an effective technical way for reducing the engine knock tendency. In order to further reveal the knock influence rules, this paper carried out the knock combustion impact research of different CRs and EGRs on a SI engine fuelled with n-butanol from the aspects of both experiment and simulation.First of all, the experiment research of different CRs on the knock combustion impact was carried out. The results showed that with the increase of CR, the peak pressure was increased and the corresponding crank angle was decreased gradually, the engine knock intensity was amplified. The knock circulation share was increased with the increase of CR, and strong knocks were more likely to occur.The experiment research of EGR on the knock combustion impact under different CRs was carried out on the basis of the same knock intensity when EGR was 0%. The results showed that with the increase of EGR, the maximum amplitude of pressure oscillation was decreased. Under all CRs, the engine torque was decreased and the brake specific fuel consumption was increased with the increase of EGR.At last, the simulation research of different CRs and EGRs on the knock combustion impact was carried out with AVL-FIRE. The results showed that with the increase of CR, the self-ignition delay and the combustion duration were decreased, the combustion temperature and pressure were increased, the knock tendency was increased gradually. With the increase of EGR, the self-ignition delay and the combustion duration were increased, the combustion temperature and pressure were decreased, the knock tendency was decreased gradually.In conclusion, increase the compression ratio of a SI engine fuelled with n-butanol can improve the engine performance, but will also increase the knock intensity. EGR can depress the engine knock combustion effectively so that the engine can work under high compression ratio, thus will improve the engine performance and fuel economy, and improve the utilization rate of n-butanol.