High-efficiency combustion of gasoline compression ignition (GCI) mode with medium-pressure injection of low-octane gasoline under wide engine load conditions

Abstract

Gasoline Compression Ignition (GCI) mode with medium injection pressure has the potential to achieve high engine efficiency while keeping costs low. In this study, the combustion and emission characteristics of GCI mode with medium-pressure injection of low-octane gasoline were studied and compared to conventional diesel combustion (CDC) under wide engine loads. The results showed that under low to medium loads, GCI mode had improved particulate emissions and indicated thermal efficiency (ITE) compared to CDC mode. However, at high loads, the PM emissions were much higher than CDC mode, and the ITE decreased for IMEP increasing from 10 to 12 bar due to limited injection pressure. To address this, a dual direct injection GCI mode with medium injection pressure was proposed to improve combustion under high loads. With this strategy, NOx emissions were significantly reduced, and ITE was simultaneously improved for IMEP of 10 and 12 bar. Using low octane gasoline and dual direct injection, the ITE of GCI mode can reach or exceed 50% for IMEP from 4 to 12 bar. Compared to gasoline with a research octane number (RON) of 83, gasoline with an RON of approximately 72 had higher ITE under most tested conditions and is recommended as the fuel for GCI mode.