Computational study of ignition delay times and laminar flame speed of POrsche SYNthetic fuels: Comparison with conventional gasoline

Recent years have shown Porsche Synthetic Fuels (POSYN) as one promising and quick solution to be used in both existing and new-generation internal combustion engines (ICEs) to immediately contrast the CO2 emissions. Nevertheless, to make these fuels efficient and effective for ICE applications, extensive testing is needed to evaluate the fuel performance and its impact on tailpipe emissions; numerical simulations (both 1D and 3D) can provide relevant support to reach the target in a faster and economically feasible way, providing guidelines for the design of eFuels and their use. An accurate and reliable modeling framework, able to mimic the chemical and physical characteristics of the fuels for a given set of operating conditions, is therefore mandatory to support the development process. The definition of a fuel surrogate is crucial to integrate the relevant properties in the 3D-CFD modeling framework. In this work, a methodology for the calculation of LFS (Laminar Flame Speed) and IDT (Ignition Delay Time) of different fuels is developed and applied to compare the characteristics of two different POSYN fuels with a conventional RON 98 gasoline by using 0D/1D detailed chemical kinetics simulations. The methodology relies on a proper definition of the composition of a six-component fuel surrogate and on the critical selection from the literature of a suitable chemical kinetics mechanism. The methodology is then applied to calculate IDTs and LFSs on a wide set of engine-relevant conditions, allowing for comparing the fuels' behavior, paving the way for more detailed 1D and 3D-CFD studies. Finally, the LFS calculations of free-aromatics gasoline showed a faster flame speed in a range between 3% and 6% compared to the conventional one at engine-like conditions. Instead, IDTs, according to similarities in RON/MON, showed overall similar output and peculiar NTC behavior when MTBE is present.