A consideration of aútoignition timing of alternative low carbon number fuels in 2-stroke ATAC engine

ATAC (Active Thermo-Atmosphere Combustion) is autoignition combustion in two stroke engines, which occurs by diluting fresh gas with residual gas to keep high temperature at low load operation. In this study, a two-stroke ATAC engine test was carried out to obtain fundamental knowledge for controlling the autoignition and combustion characteristics in the premixed charged compression-ignition lean combustion engine. The influences of delivery ratio, equivalence ratio and adiabatic compression speed on autoignition timing, autoignition temperature and combustion duration were investigated. ATAC autoignition temperature and combustion duration do not depend on delivery ratio and equivalence ratio, but is determined by the individual fuel characteristics. Increasing adiabatic compression speed, ATAC autoignition temperature was lowered. ATAC autoignition occurs at the crank angle when the mass-averaged temperature of the mixture reached a constant temperature that belongs to the individual fuel. Then autoignition timing depends on mass-averaged temperature at port closing timing. But over a certain limitation of delivery ratio, autoignition does not occur nevertheless the temperature at this timing is same, we have to analyze more about this result.