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It is known that the regular gasoline and primary reference fuel (PRF), that have the same research octane number, show the different HCCI engine performance, because of the different phasing and heating value of low temperature heat release. This means that the research octane number is not an “all-round” auto-ignition index, and another index must be developed to evaluate the HCCI combustion characteristics. In this paper, eleven pure hydrocarbon components were blended into twenty three different kinds of model fuels (surrogate fuels), labeled BASE, MC01-MC11 and K01-K11, and the HCCI engine tests were performed under five different intake air temperature conditions to change the auto-ignition characteristic of each hydrocarbon component. As HCCI combustion can be described as a lean and slow gasoline knocking phenomenon, an analysis of HCCI combustion data gives us much more important knowledge of gasoline knocking phenomenon.

Low NOx and soot free premixed diesel combustion can be realized by increasing ignition delays in low oxygen atmospheres, as well as the combustion here also depends on fuel ignitability. In this report single intermittent spray combustion with primary reference fuels and a normal heptane-toluene blend fuel under several oxygen concentrations in a constant volume combustion vessel was analyzed with high-speed color video and pressure data. Temperature and KL factor distributions are displayed with a 2-D two-color method. The results show that premixing is promoted with a decrease in oxygen concentration, and the local high temperature regions, above 2200 K, as well as the duration of their appearance decreases with the oxygen concentration. With normal heptane, mild premixed diesel combustion can be realized at 15 vol% oxygen and there is little luminous flame.