화학공학소재연구정보센터
Fuel, Vol.239, 1001-1014, 2019
Load limits of an HCCI engine fueled with natural gas, ethanol, and methanol
Low Temperature combustion (LTC) engines are able to reduce NOx and particulate matter (PM) emissions, simultaneously. But, this combustion process generally leads to higher amounts of HC and CO emissions. Furthermore, higher cyclic variation (misfire) especially at low engine loads as well as high pressure rise rate (knock) at high loads situations, are the main obstacles to application of this concept. Therefore, fuels with good auto-ignition specification (i.e. lower octane numbers) are suitable for low load conditions, while for high load situations, fuels with higher octane numbers are required. In the current study, three fuels with different octane numbers (i.e. natural gas, ethanol and methanol) are experimentally investigated in a single cylinder engine to explore proper operating range for each fuel. Achievements suggested that natural gas is the proper fuel for HCCI strategy at higher intake temperatures and rich mixture conditions (i.e. high loads) while ethanol and methanol are good choices for lower intake temperatures and lean mixtures (i.e. low loads). Results revealed that for the mixtures with the equivalence ratios more than 0.3 (phi > 0.3) and intake temperatures higher than 430 K (T-ivc > 430 K), natural gas is a suitable choice, while at this situation, ethanol and methanol lead to knock and also unacceptable level of NOx emission. Ethanol has good performance for 0.2 < phi < 0.3 and T-ivc < 430 K, while methanol is applicable even for ultra-lean mixtures (phi approximate to 0.1). These results highlight the use of flex fuel vehicles (FFVs) idea for current engine.