Low-temperature combustion analysis of butanol isomer/diesel blends under reduced oxygen conditions in a constant volume combustion chamber

Butanol is an attractive biofuel and power resource in the field of power generation, long-haul heavy-duty transportation, and off-road applications. Particularly, when combined with low temperature combustion concepts, the NOx/soot tradeoff can be relieved at the presence of exhaust gas recirculation. Therefore, the combustion and ignition characteristics of butanol isomers at low oxygen (O2) availability should be fully understood. This work focuses on the low temperature heat release and negative temperature coefficient behaviors at low O2% in a CVCC. Three butanol isomers are blended with diesel from 20 to 80 vol% and tested at various temperatures and oxygen concentrations (17 %, 15 %, 13 %). Tert-butanol/diesel blends yield the shortest ignition delay (ID) time. This is likely due to the competition of the OH radical between the butanol and alkane. The results also show ID increases as the blend ratio increases. Specifically, at a low blend ratio, the ignition delay will increase as the oxygen concentration and chamber temperature decrease. As the blend ratio reaches 60 and 80 vol %, ID decreases at low chamber temperature irrespective of the O2%, due to early low temperature heat release. A similar transition trend can be found in the burn duration results as well.