Effects of asynchronous late intake valve closing combined with high geometric compression ratio and exhaust gas recirculation on combustion and fuel consumption in a turbocharged SI engine:An experimental study

Abstract

To achieve low-carbon transportation, a novel Miller cycle was implemented by using asynchronous late intake valve closing (ALIVC) in the high compression ratio turbocharged SI engine. The effects of the Miller cycle on combustion and performance were investigated and compared with the original Otto cycle. Based on this, EGR was introduced and its effects on Miller cycle engine performance and energy balance were investigated. The results show that the Miller-CR12.5 can reduce pumping loss and suppress knock without sacrificing power output. Compared to the Otto-CR10.5, the Miller-CR12.5 achieves a 6.7 % reduction in BSFC at the lowest fuel consumption point and a 10–11.4 % reduction at high loads. The lower peak combustion temperature allows the Miller-CR12.5 to eliminate fuel-enriched injection at high loads, reducing the heat transfer and combustion loss. The introduction of EGR in the ALIVC Miller cycle engine decreases the peak HRR and extends the combustion duration. However, the advanced 50 % combustion position and increased effective expansion ratio can improve engine performance. At 10 % EGR rate, the BSFC obtains a 2.1 % reduction and NOx emissions are reduced by 62 %. As the EGR rate increases, the heat transfer and exhaust loss decrease, but there is a slight increase in combustion loss.