Fuel property effects on low-speed pre-ignition

Abstract This work explores the dependence of fuel distillation and flame speed on low-speed pre-ignition (LSPI). Findings are based on cylinder pressure analysis, as well as the number count, clustering, intensity, duration, and onset crank angle of LSPI events. Four fuels were used, with three of the fuels being blends with gasoline, and the fourth being neat gasoline. The blended fuels consisted of single molecules of different molecular types: a ketone (cyclopentanone), an alcohol (2-methyl-1-butanol), and an aromatic (ethylbenzene). All three pure molecules have RON values within ±2 and boiling points within ±5 °C. These fuels were blended with gasoline to a 25% mass fraction and were used to run the engine at identical LSPI prone operating conditions. The findings highlight that fuels with similar boiling properties and octane numbers can exhibit similar LSPI number counts, but with vastly different LSPI magnitudes and intensities. Moreover, the results highlight fundamental fuel properties such as flame speed are critical to characterizing the LSPI propensity and behavior of the fuel.