ID 379

Observation on the flame behavior of the biodiesel, diesel, and n-heptane single fuel droplets in a normal gravity condition

 

Abstract:

This paper was performed to understand the flame behavior of the biodiesel, diesel, n-heptane and its mixing fuel droplets under the normal gravity condition. This experimental study would provide the results of the ignition delay (tignition), flame propagation speed (Vflame), flame extinction time (textinction), flame life-time (tflame life-time), and maximum flame length (Lmax. flame) with different initial droplet size (d0) and different fuel types of single droplets under the same ambient conditions. In order to observe the combustion process of test fuels, the combustion visualization and analysis were performed by using the high speed camera. The single fuel droplet was supplied into the stainless wire by using the syringe pump and was combusted by using the heat source of power supply equipment. It was revealed that the ignition delay of the n-heptane fuel droplet was shorter than biodiesel and diesel fuel droplets since the n-heptane fuel has a relatively higher evaporation rate than other fuels in the liquid phase. The longer flame extinction time was also observed in the biodiesel fuel than diesel fuel at the normal gravity condition since the higher boiling point, surface tension, and viscosity of biodiesel fuel may affect to the droplet atomization and evaporation. However, the flame life-time of diesel fuel was a longer than the biodiesel fuel although the flame extinction time of diesel is shorter than biodiesel due to the short ignition delay. The flame propagation speed became slower when the droplet size was the range from 1.209 mm to 1.299 mm due to the time that the measured maximum flame length decreased as the droplet lifetimes decreased. The results of maximum flame length of test fuel were increased since the test droplets can supply the relatively large amount of fuel mass flux to the flame surface when the initial droplet size increased.