Experimental investigation on the effects of octane sensitivity on partially premixed low-temperature combustion

Abstract

Partially premixed low-temperature combustion (PPC) has the potential to achieve efficient and clean combustion. Recent studies have shown that the octane number (ON) and sensitivity (S) are two of the crucial factors affecting combustion and emission in PPC. In order to improve the combustion and emission of PPC, this paper respectively used the toluene reference fuel (TRF) and ethanol reference fuel (ERF) to conduct experiments on a single-cylinder diesel engine to explore the effects of ON and S on combustion and emission of PPC. The experiments were carried out at high load with various exhaust gas recycle (EGR) rate and start of injection (SOI) timing. The results show that S shows stronger effects on combustion with RON90 fuels, and the indicated thermal efficiency (ITE) decreases when S is increased. The effect of S on the combustion and emissions of ERF70 and TRF70 is somewhat different. In terms of combustion phase control and highest ITE, the gap between ERF70 and TRF70 is close. But because the benzene ring in toluene promotes the formation of soot, while the ethanol has better volatility and the oxygen in fuels are favorable for soot oxidation, the soot emission of TRF70 is significantly higher than that of ERF70. It is found that TRF70 with low S (S < 2) and ERF70 with S (5 < S < 7) show potential to achieve efficient and clean PPC under high load. However, considering the ITE and overall emissions, the ERF70 shows greater advantages over TRF70 under the current condition.