Experimental and numerical studies on three gasoline surrogates applied in gasoline compression ignition (GCI) mode

GCI (gasoline compression ignition), as one of the competitive low temperature combustion modes, has great potential to meet the increasingly stringent regulations. In order to understand the combustion mechanism of GCI through chemical kinetics, gasoline surrogates become the focus of research to reproduce the combustion and emission characteristics of real gasoline fuel. In this work, three gasoline surrogates have been compared with commercial RON92 gasoline on combustion and emission characteristics at different loads and EGR (exhaust gas recirculation) conditions. The results show that PRF (primary reference fuel) is not suitable to reproduce the combustion characteristics of RON92 gasoline. The soot emission of TRF (toluene reference fuel) is higher than that of gasoline at high load and high EGR (>20%) conditions. The THC (total hydrocarbons) of TRFDIB (toluene reference fuel with diisobutylene) is slightly higher than that of gasoline at medium and low loads. However, TRFDIB has the potential to better reproduce the NOx and soot emissions of RON92 gasoline under other conditions. The combustion characteristics can be well reproduced by TRFDIB within the whole range of test conditions. The chemical kinetics analysis results show that EGR (mainly CO2 and H2O) has inhibiting effect on the fuel with NTC (negative temperature coefficient) behavior and that the components with low NTC promote the ignition process with the increase of EGR comparatively. The addition of toluene slows down the conversion rate of iso-octane in TRF while the addition of DIB accelerates the surrogates' oxidation rates, since DIB can produce more OH radical and CH2O to speed up the combustion process at low temperature.