Experimental and Numerical Study of Abnormal Combustion in Direct Injection Spark Ignition Engines Using Conventional and Alternative Fuels

Abstract

In this paper, the potential of alternative fuels to reduce preignition in engines is primarily investigated. Two ketones (2-butanone and 3-methylbutanone), a furan (2-methylfuran), and five alcohols (ethanol, iso-propanol, 2-butanol, iso-butanol, and 1-propanol) are compared to three conventional fuels (RON95E0, RON95E10, and iso-octane). If the alternative fuels can reduce preignition significantly, the efficiency of spark-ignition engines can be potentially increased. One major aim is to categorize the fuels in terms of preignition resistance. Additionally, the distributions of the initial preignition kernels are measured by high-speed luminescence imaging to analyze the reason for preignition. Furthermore, the occurrence of measured preignition is compared with computed ignition delay times at the pressures and temperatures of the engine load points used to find out whether the mixture is prone to autoignition in the bulk gas phase. This is most likely the case for the three conventional fuels because of thermodynamically critical gas-phase conditions. Seemingly, preignition is not induced by droplets, presumably because of an improved injector targeting. Moreover, the preignition resistance of the alternative fuels is significantly higher (critical intake pressure difference: ∼2 bar) compared to that of the three conventional fuels. It can also be concluded that 2-butanone is most resistant against preignition. Similarly, alcohols and 3-methylbutanone are highly beneficial compared to conventional fuels. Overall, the most important fuel properties for preignition appear to be research octane number and enthalpy of vaporization. Apparently, ignition is caused by glow ignition at a hot surface (spark plug) only for 2-methylfuran, iso-butanol, and 1-propanol.

A comparative analysis of knock severity in a Cooperative Fuel Research engine using binary gasoline–alcohol blends

“…Tests were performed from 8:1 for pure gasoline to 16:1 for E84 blend. These results are in accordance with previous studies 29,30–32…”

“…Tests were performed from 8:1 for pure gasoline to 16:1 for E84 blend. These results are in accordance with previous studies 29,[30][31][32] Qian et al 34 demonstrated that the knock-limited spark timing can be advanced progressively as the ethanol injection proportion is increased as well. Tests were carried out in a dual-fuel SI engine.…”

“…[23][24][25] In recent years, research on the behavior of ethanolgasoline blends in SI engines has been numerous. Exhaust gas emissions, 26,27 combustion efficiency, [27][28][29] octane number increase and knock mitigation, 22,[29][30][31][32] or its use with stratified charge SI strategies are some of the most studied fields. 33 Cooney et al 22 studied knock resistance for various ethanol-gasoline blends at different concentrations (pure gasoline, E20, E40, E60 and E84), including variations in CR and ignition time.…”

Alcohol lean burn in heavy duty engines: Achieving 25 bar IMEP with high efficiency in spark ignited operation

“…Super-knock phenomenon and mitigation strategies has been discussed in detail by previous works. [15][16][17][18][19] In addition, studies [20][21][22] have reported preignition potential of various fuels and blends. Despite the high resistance to auto-ignition of ethanol, the longer injection duration and wall wetting increases pre-ignition occurrences that could lead to super-knock.…”