Desenvolvimento de mecanismos cinéticos químicos reduzidos para diferentes misturas de gasolina e etanol

Abstract

The increase in the energy demand worldwide and the creation of very restrictive regulations to the greenhouse gases emission, raise the need of using renewable fuels, alternatives to gasoline and diesel, which are getting scarce. The use of ethanol as a pure fuel or as an additive to gasoline is an approach on the reduction of fossil fuel dependence and on the reduction of the pollutant gases emission; As a consequence, it is fundamental the development of researches aiming to acquire knowledge on the physical and chemical behavior of gasoline-ethanol blends, on different proportions. For this, chemical kinetic mechanisms capable to characterize those fuels with satisfactory accuracy are needed. However, those mechanisms may have hundreds or thousands of species and elementary chemical reactions, which makes its use on combustion simulations using complex geometries such as internal combustion engines impractical. The situation is even more onerous when working with mixtures of fuels, like the Brazilian gasoline type C, that has 27% of ethanol by volume. Considering the above exposed and the need of numerical simulations to predict the behavior of internal combustion engines working with different proportions of gasolineethanol mixtures, this work aimed to create and validate reduced chemical kinetic mechanisms capable of representing the course of gasoline-ethanol blends combustion. To achieve that, the method of directed relation graph with error propagation associated with sensitivity analyses and isomer lumping was proposed as a systematic tool for the detailed mechanisms reduction. Experimental data of ignition delay time and laminar flame speed were used as validation parameters. At the end of the study, three reduced mechanisms were developed, the first one with 239 chemical species, the second with 115 and the third with 75 species. Good agreement between the experimental and numerical data was reached for both mechanisms, perceiving differences in their accuracy according to the conditions and fuels compositions evaluated