Autoignition of low and high octane gasolines

Ignition delay times of two high-octane gasolines (RON: 91 and 97.5) and two low-octane gasolines (RON: 70.3 and 71.8) were studied in a high-pressure shock tube and in a rapid compression machine. The high-octane gasolines were oxygenated and contained 5 - 10 % ethanol by volume. Experiments were carried out over a wide range of temperatures (700 - 1300 K), at two pressures (20 and 40 bar) and at two equivalence ratios (0.5 and 1.0). All fuels exhibited very similar reactivity at high temperatures. The RON-dependence was observed to be strongest in the NTC region while the sensitivity (RON - MON) effects were seen both in the intermediate- and low-temperature regions. Binary (PRF) and multi-component surrogates were formulated to simulate the reactivity of these gasolines. It was observed that PRF surrogates captured the reactivity of low sensitivity (and low octane) gasolines adequately while multi-component surrogates were needed to fully describe the autoignition behavior of high sensitivity (and high octane) gasolines. Fuel composition effects on autoignition were elaborated with the help of detailed chemical kinetic simulations.