Understanding the ignition delay of E20 gasolines and E20 gasoline surrogates

The autoignition behaviour of E20 gasolines is investigated experimentally using both a rapid compression machine and a high-pressure shock tube. A detailed chemical kinetic model is employed to simulate the data. Four E20 gasolines are studied, two of which are formulated from refinery streams, thereby representing a “real” fuel, while the other two are surrogate blends, which can also be modelled, and which are designed to approximately represent the RON and MON of the fuels made from the refinery streams. The measured ignition delay times (IDTs) of the surrogate fuels are always measured to be shorter than those of the “real” fuels at all temperatures and equivalence ratios, although this is most apparent in the negative temperature coefficient (NTC) regime. This deviation can be, at least partly, explained by the fact that the RON of the surrogates is slightly lower than the RON of the corresponding “real” fuels. For the surrogate fuels, there is an under-prediction of IDTs using the Galway GS_MechV1 chemical kinetic mechanism compared to the experimental results. This under-prediction is found to be more prominent at an equivalence ratio of 0.5. A modification to the original surrogates was made which increased the RON of the surrogate fuels and brought the simulated IDTs closer to the experimental measurements.