Adaptability of alternative fuels to lean burn in 2-stroke ATAC engine (comparison between DME, methanol, ethanol, methane and propane)

ATAC is "bulk-like" and/or "non-propagating" combustion process caused by compression autoignition of premixture, and it is stable in lean combustion region. And ATAC engine is expected to be an engine using alternative fuels which are difficult to apply to usual engines because of their generally low cetane number. In this study, a two-stroke ATAC engine test was carried out to evaluate an adaptability of alternative fuels for lean burn. Methanol, ethanol, dimethyl ether (DME), methane and propane were used as the test fuels. Engine speed, BMEP and equivalence ratio were considered parameters. The influence of fuel characteristics on autoignition timing, combustion duration and autoignition gas temperature were investigated. Using oxygenated fuels, the lean limit of ATAC operating region shifts to lean side. ATAC autoignition temperature of each alternative fuel, except methane and propane, ranges from 950 K to 1150 K regardless of equivalence ratio, delivery ratio and engine speed, and it rises with increasing cetane number of fuel.