EGR rate 변화에 따른 바이오디젤 정적 연소 특성에 관한 수치해석 연구

Abstract

This paper was conducted to investigate the effect of EGR on the combustion characteristics, NO<SUB>X</SUB> and CO formation characteristics of constant volume combustion of the biodiesel fuel. To achieve this, methyl decanoate, methyl 9 decenoate, and n-heptane species were applied for the simulation of the biodiesel and diesel chemical reactions during the constant volume combustion process. The analysis of biodiesel-EGR combustion was performed by simultaneously considering the mole fraction which was composed of the N₂, H₂O, CO₂, and O₂ species according to the EGR rate (10~60%). As a result of the combustion characteristics, the maximum OH radical was reduced as the EGR rate increase, and the ignition delay was increased at the same time. Most of NO<SUB>X</SUB> emission was generated by the thermal NO<SUB>X</SUB> reaction, and it was not emitted after the EGR rate of 30% conditions due to the decrease of combustion temperature and oxygen concentration. The reactivity of CO generation was showed the high absolute rate of production in the reaction path related to the reactions of HCO radical, and it has a trade-off relationship with the tendency of NO<SUB>X</SUB> emissions. In addition, it was indicated that the UHC emission increased rapidly since the chemical reactions related to the fuel oxidation did not occur actively when the ambient temperature was 800~1,000 K and the EGR rate was 60% conditions.