Experimental study of combustion and cyclic variations in a CRDI engine fueled with heptanol/iso-propanol/butanol and diesel blends

The present study experimentally investigates main combustion, fuel injection, and cycle-by-cycle variations in a CRDI diesel engine fueled with blends of heptanol/iso-propanol/butanol and diesel. Two percentages of diesel and higher alcohol blends, denoted as D85HIB15 (85% diesel, 5% heptanol, 5% iso-propanol, 5% butanol) and D70HIB30 (70% diesel, 10% heptanol, 10% iso-propanol, 10% butanol), were utilized in the engine at different BMEPs (3.4, 5.2, and 6.9 bar). With increasing ratio of the alcohol blends in diesel, it was founded lower CPmax, PRRmax, and IMEP, prolonged ignition delay, earlier injection timing and combustion center, and also higher injection pressure compared to diesel fuel. Based on the standard deviation and coefficient of variation for 200 consecutive combustion data, diesel-HIB blends showed lower cyclic variations than conventional diesel under all test cases. Notable fluctuations in cycle-by-cycle injection pressure highlighted to cyclic combustion fluctuations. Finally, the relationship between main combustion parameters showed that the highest correlation was around 0.8 between CPmax and PRRmax for diesel-HIB blends at low load, and for pure diesel and D85HIB15 at medium load, indicating that there was a well linear relationship. •Use of heptanol/iso-propanol/butanol blends in automotive common-rail diesel engine.•Cycle-by-cycle combustion analyses including CPmax, PRRmax, and IMEP.•Reduced cyclic variations in cylinder pressure with the higher alcohol blends.•Reduced cylinder pressure, heat release rate, and pressure rise rate with the higher alcohol blends.•The highest correlation coefficient between peak cylinder pressure and peak pressure rise rate.