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. Results show that ignition timing of M100 is advanced much more than other fuels and alcohols have better adaptive capabilities to lean combustion than gasoline within the attainable HCCI operation range. When fueling with M100 and E100, The Lambda can reach up to 1.5 and 1.4 respectively, whereas E0 can only reach 1.3. Also E50, M50, E100 and especially M100, show excellent HCCI operating capabilities in the high-speed and low-load range, where the combustion of E0 is limited by misfire. And also NOx emissions can be reduced to an extremely low level when fueling with methanol.