Butanol, a four-carbon alcohol, is considered in the last years as an interesting alternative fuel, both for Diesel and for gasoline application. Its advantages for engine operation are: good miscibility with gasoline and diesel fuels, higher calorific value than ethanol, lower hygroscopicity, lower corrosivity and possibility of replacing aviation fuels. Like ethanol, butanol can be produced as a biomass-based renewable fuel or from fossil sources.
In the research project, DiBut (Diesel and butanol) addition of butanol to Diesel fuel was investigated from the points of view of engine combustion and of influences on exhaust aftertreatment systems and emissions. One investigated engine (E1) was with emission class “EU Stage 3A” for construction machines, another one, engine (E2) was HD Euro VI.
The most important findings are: with higher butanol content, there is a lower heat value of the fuel and there is lower torque at full load. With Bu30 the conversion rates of CO and HC in the oxidation catalyst (DOC) are slightly lower, light-off temperatures are a little higher and NO2 production is lower. The PM-emissions with Bu30 are lower, so the soot loading of DPF takes a longer time. No impacts of Bu30 on NOx reduction rates of the SCR-system and on the non-legislated gaseous emission components were found.
The operation of engine (E1) with Bu30 (30% vol butanol in fuel) was instable at lower part load due to the lower Cetane Number of the blend fuel. The electronic control system of the engine (E2) compensated very well the varying properties of fuels up to Bu30. For both investigated engines, the butanol rate (Bu30) can be considered as a limit for a problem-free engine starting and operation.