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CAI combustion has the potential to be the most clean combustion technology in internal combustion engines and is being intensively researched. Following the previous research on CAI combustion of gasoline fuel, systematic investigation is being carried out on the application of bio-fuels in CAI combustion. As part of an on-going research project, CAI combustion of methanol and ethanol was studied on a single-cylinder direct gasoline engine with an air-assisted injector. The CAI combustion was achieved by trapping part of burnt gas within the cylinder through using short-duration camshafts and early closure of the exhaust valves. During the experiment the engine speed was varied from 1200rpm to 2100rpm and the air/fuel ratio was altered from the stoichiometry to the misfire limit. Their combustion characteristics were obtained by analysing cylinder pressure trace.

This paper presents results from an experimental programme researching the in-cylinder conditions necessary to obtain homogenous CAI (or HCCI) combustion in a 4-stroke engine. The fuels under investigation include three blends of Unleaded Gasoline, a 95 RON Primary Reference Fuel, Methanol, and Ethanol. This work concentrates on establishing the CAI operating range with regard to Air/Fuel ratio and Exhaust Gas Re-circulation and their effect on the ignition timing, combustion rate and variability, Indicated thermal efficiency, and engine-out emissions such as NOx. Detailed maps are presented, defining how each of the measured variables changes over the entire CAI region. Results indicate that the alcohols have significantly higher tolerance to dilution than the hydrocarbon fuels tested. Also, variations in Gasoline blend have little effect on any of the combustion parameters measured.

In this paper, HCCI combustion characteristics of three typical high octane number fuels, gasoline, ethanol and methanol, are compared in a Ricardo single cylinder port injection engine with compression ratio of 10.5. In order to trap enough high temperature residual gas to heat intake mixture charge for stable HCCI combustion, camshafts of the experimental engine are replaced by a set of special camshafts with low valve lift and short cam duration. The three fuels are injected into the intake port respectively in different mixture volume percentages, which are E0 (100% gasoline), E50 (50% gasoline, 50% ethanol), E100 (100% ethanol), M50 (50% gasoline, 50% methanol) and M100 (100% methanol). This work concentrates on the combustion and emission characteristics and the available HCCI operation range of these fuels. What's more, the detailed comparison of in-cylinder temperature, ignition timing and other parameters has been carried out.