Experimental studies on the co-effects of engine operating parameters and fuel functional groups on the performance and emissions of a GDI engine

The distributions of molecular functional groups in gasoline have strong effects on the in-cylinder micro-combustion, macro-heat release and emission generation mechanism. It is quite difficult to study the coupling relationship between fuel functional groups and engine performance with commercial gasoline due to its complex components. In this paper, multi-components gasoline surrogates including toluene reference fuel (TRF), n-heptane/iso-octane/toluene/cyclohexane (CTRF) and n-heptane/iso-octane/toluene/cyclohexane/diisobutylene (CDTRF) were applied to study the effects of fuel functional groups and engine control parameters (spark timing, equivalence ratio) on combustion and emissions of a gasoline direct injection (GDI) engine. Amongst the results, it is worth noting that the surrogates produce 30-40% higher nitrogen oxide (NOx) emissions than gasoline and have obvious advantages in particulate matter (PM) emissions, however, at the cost of high carbon monoxide (CO) and total hydrocarbon (THC) emissions. In addition, there are obvious differences in combustion characteristics and unregulated emissions between the surrogates due to different functional groups.