The investigation of droplet combustion characteristics of biodiesel - diesel blends using high speed camera

Abstract

Biofuels are playing more and more important roles worldwide. While it will reduce the overall emission of greenhouse gases, it may damage the combustion system through corrosion and poor lubrication, and generates more local air pollution than fossil fuels if the biofuel burning properties are not well understood and controlled. This work investigates the effect of blending diesel fuel by biodiesel on the combustion of a single fuel droplet. Biodiesel blends substituting diesel oil in different concentrations on volumetric basis, in addition to pure diesel and purer biodiesel were studied. Schlieren and bbacklighting imaging techniques have been used to track the droplet combustion throughout its complete lifetime using a high speed camera. The results showed that partial substitution of diesel oil by biodiesel at the test conditions led to increasing secondary atomization from the droplet, compared to pure diesel or biodiesel fuel droplets. This in turn enhances evaporation, mixing, and then combustion. Additionally, the results showed a slight decrease in droplet burning rate of the blend compared to the pure fuel droplets. Nucleation has also been traced to take place inside the droplets of the blends. Moreover, flame size (height and width) has been reduced by increasing biodiesel concentration in the blend.