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A Homogeneous charge induced ignition (HCII) combustion, realized by in-cylinder fuel blending of gasoline and diesel fuel, was developed and carefully optimized, both on a single cylinder and a multi-cylinder light-duty diesel engines, for high thermal efficiency and near zero emissions in a wide engine-operation range up to IMEP of 1 MPa. The effects of mixing and chemical parameters of HCII combustion, which can be controlled by production-viable hard-ware using conventional gasoline and diesel fuel, include injection timing of diesel fuel, injection rate pattern of diesel fuel (such as split injection), the gasoline/diesel ratio, boost pressure and exhaust gas recirculation (EGR). Based on a single cylinder engine, the experimental result shows that the interaction of the mentioned control parameters plays decisive role in determination of exhaust emissions and thermal efficiency.

Two premixed compression ignition modes for low octane gasoline are numerically investigated. The multiple premixed compression ignition (MPCI) mode is featured with a sequence of “spray- combustion- spray- combustion”, while the partially premixed compression ignition (PPCI) mode is a sequence of “spray- spray- combustion”. This paper compares the combustion process of the two modes using multi-dimensional CFD code, KIVA-3v, which can perform chemical reaction calculations for different fuels by a discrete multiple component (DMC) method. The fuel used for simulation consists of 58.5% i-C8H18 and 41.5% n-C7H16 in volume, and has the same RON and similar physical properties to straight-run naphtha used in the experiment. The engine operating condition is fixed at a 1600rpm and 0.7 MPa IMEP. The injection strategies for these two modes are different. All of the parameters in the simulation come from the single cylinder engine experiments.

Super knock which occurs in highly boosted spark ignition engines in low speed pre-ignition regime can lead to severe engine damage. However, super knock occurs occasionally, it is difficult to clearly identify the causes. The widely accepted assumption for the cause of this phenomenon is oil intrusion. Most of oils have been proved to have higher cetane number than n-heptane dose, indicating that the intruded oil is very liable to auto-ignition in a boosted engine. Although there have been reported the type of base oil and additive has significant effect on pre-ignition frequency, the oil induced super knock is still so far not supported by any direct evidence. This paper presents the effect of direct oil intrusion into cylinder on super knock. The experiment was carried out in a single cylinder engine. The diluted oil by gasoline with different ratio was directly injected into cylinder using a modified single-hole injector with 4MPa injection pressure.