Analysis of Gasoline Surrogate Combustion Chemistry with a Skeletal Mechanism

Knocking combustion is a major obstacle towards engine downsizing and boosting—popular techniques towards meeting the increasingly stringent emission standards of SI engines. The commercially available gasoline is a mixture of many chemical compounds like paraffins, isoparaffins, olefins and aromatics⁠. Therefore, the modeling of its combustion process is a difficult task. Additionally, the blends of certain compounds exhibit non-linear behavior in comparison to the pure components in terms of knock resistance. These facts require further analysis from the perspective of combustion chemistry. The present work analyses the effects of blending ethanol to FACE-C gasoline. A range of pressures, temperatures, and equivalence ratios has been considered for this purpose. The open source softwares Cantera version 2.4.0 and OpenSMOKE++ Suite have been used for the simulations. Moreover, the present work proposes a skeletal chemical kinetic mechanism for six component gasoline surrogates with 108 species and 1605 reactions. This mechanism has been formed using the open source chemical kinetic reduction code pyMARS. It has been found from the present study that the octane rating and sensitivity increases with the addition of ethanol to gasoline up to 30% volumetric blend. The increase in the octane sensitivity due to ethanol blending can be assessed from the maximum cool flame heat release rate in a 0-D isochoric batch reactor. The chemical kinetic perspective of the changes in octane numbers and sensitivity has been explained in the present analysis with the help of reaction path analysis.