Ignition delay time measurements and modeling for gasoline at very high pressures

Abstract

Ignition delay times (IDT) for high-octane-number gasolines and gasoline surrogates were measured at very high pressures behind reflected shock waves. Fuels tested include gasoline, gasoline with oxygenates, and two surrogate fuels, one dominated by iso-octane and one by toluene. RON/MON for the fuels varied from 101/94 to 106.5/91.5. Measurements were conducted in synthetic air at pressures from 30 to 250 atm, for temperatures from 700 to 1100 K, and equivalence ratios near 0.85. Results were compared with a recent gasoline mechanism of Mehl et al. (2017). IDT measurements of the iso-octane-dominated surrogate were very well reproduced by the model over the entire pressure and temperature range. IDT measurements for the toluene-dominated surrogate were also reproduced by the model to a lesser extent. By contrast, IDT measurements for the neat gasoline and gasoline with oxygenates, show excellent agreement with the trends of the Mehl et al. model only below 900 K. Above 900 K, the model returned IDT values for the two gasolines that were approximately 1.6× the measured values. Finally, we observed that IDT measurements for the toluene-dominated surrogate fuel and the two gasolines, near 70 atm and below 900 K, appeared to be shortened, possibly by non-homogeneous ignition or non-ideal gas processes. This dataset provides a critically needed set of IDT targets to test and refine boosted gasoline models at high pressures.