Simulação fluidodinâmica em ANSYS - CFD da combustão dual-fuel em motores de ignição por compressão utilizando diesel renovável (HVO) com biogás

Abstract

vehicular fleet, which, in general, uses fossil fuels whose burning results in pollutant emissions. Allied with economic factors, there is an urgent concern to replace these fuels with those from renewable sources. Much of the research in this area uses experimental techniques, which are not always feasible. Thus, combining computational analysis with these techniques is of great relevance. In this context, this work analyzed computationally the combustion cycle of a Diesel engine operating with fossil diesel, HVO and HVO with biogas. For this purpose, its 3D combustion chamber geometry was modeled in a CAD software and the CFD simulations were carried on ANSYS/Forte software. A kinetic model with 35 species and 74 chemical reactions, together with the RANS RNG k-ε model, the KH-RT model, a uniform injection profile and experimental values for initial pressure and temperature were considered in the modeling step. In addition, a 0-D analysis in ANSYS/Chemkim-Pro software was performed to estimate some parameters not measured experimentally, and also to obtain two adapted kinetics models to describe the of pure HVO and HVO-biogas blend, which was done together with a mono-objective optimization process by the Lichtenberg algorithm. Both 0-D and 3D approaches were validated with experimental data. From the simulations, in-cylinder pressure and its rise rate, rate of heat release, and its accumulation, turbulence, and emissions characteristics were obtained as a function of crank angle. 3D fields of velocity, temperature, the spray of diesel, and molar fractions of CO, CO2, NO, and NO2 were also obtained. The in-cylinder pressure obtained computationally showed a good agreement with the experimental ones (which were obtained from the R&D project ROTA 2030 by GETEC-UNIFEI at 2021 and 2022), but with a longer ignition delay. It was observed that the in-cylinder pressure is strongly dependent on the duration of injection. It was also verified that the regions closer to the TDC presented the most variations in the analyzed parameters and with the maximum values. Besides, the combustion of HVO and HVO with Biogas reduced the peaks of pressure and heat release, as well as NOx and soot emissions and also presented more significant homogeneity in the velocity and temperature fields.