Proceedings of Ecos 2021 - The 34 th International Conference On Efficiency, Cost, Optimization, Simulation and Environmental Impact of Energy Systems June 27-July 2, 2021, Taormina, Italy Thermodynamic analysis of the fuel spray evaporation process for wet ethanol during the compression stroke of a direct-injection spark-ignition engine Alessandro J. T. B. de Lima a and Waldyr L. R. Gallo b a University of Campinas, Campinas, Brazil, alessandrojtblima@gmail.com b University of Campinas, Campinas, Brazil, gallo@fem.unicamp.br Abstract: The current worldwide challenge that humankind faces towards a cleaner environment and a better energy usage requires constant improvement on first and second law efficiencies of diverse tech- nologies. The phenomena of fuel spray injection and evaporation in direct-injection spark-ignition engines draw attention in this context, although they are not well explored. The application of some wet ethanol volumetric compositions as a fuel is consolidated in some countries, although its potential is not entirely explored on current engine configurations. The modeling characteris- tics regarding the previously mentioned phenomena are vastly detailed in the specific literature, although there are only a few references relating this area with the second law of thermodynamics. A second law analysis provides opportunities to reach higher energetic and exergetic efficiencies through the application of more appropriate thermodynamic states in an energetic process. There- fore, this paper presents a thermodynamic parametric analysis in a wet ethanol spray simulation during the compression stroke of a direct-injection spark-ignition engine. Its purpose is to find the best strategy to develop an adequate fuel injection and consequent evaporation during the engine operation in terms of entropy generation. Additionally, the effects of initial water content in wet ethanol on the evaporation process and its efficiency are also evaluated. A probability distribution function is used to simulate the droplet diameter distribution for fuel injection. A Lagrangian ap- proach is adopted to simulate the behavior of the droplets, while a homogeneous Eulerian one is assumed for the in-cylinder gases. Results are presented in terms of suggested first and second law efficiencies of the evaporation process, besides the evaporative cooling effect and knock integral value. Keywords: Direct-injection spark-ignition engines; Entropy generation; Multicomponent droplet evaporation; Spray evaporation efficiency; Wet ethanol. 1. Introduction Despite the intense growth of renewable energy production in the last decade, liquid fuel energy demand reached its peak value in 2019 [1]. Direct-injection spark-ignition (DISI) engines also make