단파장 필터링을 통한 단일 액적 화염 내 CH₂O, CH, C₂ 화학종 분석 및 액적 연소 특성

Abstract

This paper was performed to observe the flame behavior of the biodiesel, diesel, and n-heptane single fuel droplets and analyze the CH₂O, CH, and C₂ species in a single droplet flame included combustion characteristics experimentally. In order to visualize the combustion process of test fuel droplets, droplet combustion visualization and analysis were conducted using a high-speed camera and a CCD camera coupled with a short wavelength filter. A single fuel droplet was formed on the stainless wire using a syringe and ignited by a heat source provided from the power supply equipment. It was shown that the ignition delay of an n-heptane fuel droplet was shorter than those of biodiesel and diesel fuel droplets due to a higher evaporation rate in the liquid phase. A longer flame extinction and the flame life-time were also observed in the biodiesel and diesel fuel droplets than most n-heptane fuel droplets. In the case of the diesel fuel droplet, it was found that the flame life-time was slightly increased than the biodiesel fuel droplet. The C₂ species produced in the flame during combustion of all fuel droplets were distributed throughout the flame, while the CH and CH₂O chemical species tended to be located in the flame front and center area. As a result of combustion analysis, the biodiesel, diesel, and n-heptane fuels were shown the changes of the CH₂O mole fraction according to the two-stage combustion characteristics, and the mole fraction of CH species was decreased by CH + O₂ and CH + H₂O chemical reactions.