Comparative study on Gasoline Homogeneous Charge Induced Ignition (HCII) by diesel and Gasoline/Diesel Blend Fuels (GDBF) combustion

Abstract

Gasoline Homogeneous Charge Induced Ignition (HCII) by diesel uses port fuel injection of gasoline to form a homogeneous charge and direct injection of diesel fuel as an ignition source. Gasoline/Diesel Blend Fuels (GDBFs) uses a premixed blend of diesel and gasoline which is directly injected into the cylinder for combustion. Exploratory studies show that these two ways may integrate the advantages of gasoline and diesel fuels to achieve high thermal efficiency and low emission targets. Combustion characteristics, emission characteristics, thermal efficiency and adaptability of low-temperature combustion in these two combustion modes have been comparatively investigated on a high-pressure common rail single-cylinder diesel engine. The results show that both HCII and GDBF modes can achieve higher thermal efficiency than gasoline SI combustion and a similar or even higher thermal efficiency than diesel CI combustion because the combustion was closer to constant volume combustion. As gasoline ratio increases, the fuel–air mixing is improved in both HCII and GDBF modes, and thus soot emissions reduced dramatically, with a biggest reduction of 90%. The ignition delay in HCII mode remained almost the same, while the ignition delay in GDBF mode increased significantly with the increase of gasoline ratio. As gasoline ratio increases, the combustion duration in both HCII and GDBF modes shortened significantly. Both HCII and GDBF modes can achieve low temperature combustion with extremely low soot and NO emissions when combined with large amounts of EGR. These modes demonstrate an advantage over the diesel CI combustion mode, where the NO emissions decreased and soot emissions increased with the increase of EGR, exhibiting the classical NO-soot trade-off.