Pollutant formation simulation models (CO, NOx and UHC) for Ethanol-fueled engines

Author(s)

Alessandro José Truta Beserra de Lima

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Engenharia Mecânica
• Defense date: 2017-09-01

Examining board members

Waldyr Luiz Ribeiro Gallo; Rogério Gonçalves dos Santos; José Eduardo Mautone Barros

• Advisor: Waldyr Luiz Ribeiro Gallo

Abstract

The current worldwide necessity of alternative fuels for automobiles in the planet reflects the importance of ethanol on the international automotive market. The Brazilian ethanol, which mostly comes from sugar cane, presents a more sustainable origin than fossil fuels and may be applied as a fuel on internal combustion engines. Its use presents benefits on technical area and reduction of combustion gases, despite the three-way catalyst presence on current engines. This thesis focuses on the study and development of mathematical models for prevision and formation of regulated pollutants (carbon monoxide, nitric oxide and unburned hydrocarbons) derived from combustion process in spark-ignited engines fueled by ethanol. Concentrations of nitric oxide (NO) and carbon monoxide (CO) were calculated based on concepts of chemical kinetics and chemical equilibrium applied on a zero-dimensional two-zone thermodynamic model of a spark-ignited engine. The continuous formation analysis of these pollutants is evaluated at the same moment as a Wiebe function calculates the amount of unburned and burned masses in the cylinder, considering the conditions previously defined on the engine operation simulator. The kinetic model is composed by 22 chemical reactions and 12 chemical species (Ar, CO, CO2, H, H2, H2O, OH, O, O2, N, N2, NO), which provides a system of differential equations that is solved by the implicit trapezoidal numerical method, applied during combustion and expansion processes of the simulated cycle. Convergence during each iteration is guaranteed by the application of the Newton-Raphson method for nonlinear system of equations, obtaining relatively quick solutions, despite the calculation of the full solution of the system on each iteration. For the unburned hydrocarbon model (UHC), it was developed two simplified models for the phenomenon of crevice and flame quenching, with application of ideal gases and thermodynamic concepts. Results showed qualitatively coherence with formation and emission data presented by literature and with experimental measurements of the studied engine. These models may be applied in the future to predict the effect of auxiliary systems of the engine, such as EGR and turbocharging, on regulated gas emissions, avoiding experimental costs to obtain similar information (AU)

• FAPESP's process: 15/17041-7 - Pollutants formation simulation models (CO, NOx and HC) in ethanol engines
• Grantee: Alessandro José Truta Beserra de Lima
• Support Opportunities: Scholarships in Brazil - Master