Single Droplet Combustion Characteristics of Petroleum Diesel- Philippine Tung Biodiesel Blends

The purpose of the present study is to investigate the effects of fuel blending of petroleum diesel and biodiesel made from Philippine Tung on the combustion characteristics of fuel droplets. In this study, petroleum diesel was mixed with biodiesel at volume percentages of 0 to 100 % to produce 5 fuel blends. The ratios of fuel blends (petroleum volume/biodiesel volume) were 100:0 (P100), 75:25 (BP25), 50:50 (BP50), 25:75 (BP75) and 0:100 (B100). Single droplet combustion experiments were prepared to understand the combustion characteristics at 3 levels of ambient pressure (100, 200 and 300 kPa). Observations were carried out on the ignition delay time, the burning rate constant, droplet temperature, and the flame visualization. The results showed some effects of the adding of biodiesel in petroleum diesel and the chamber pressure on droplet combustion characteristics.  The adding of biodiesel into petroleum diesel resulted in a shorter ignition delay time and higher burning rate constants. But, the lower heating value of biodiesel caused the lower flame temperature. The possibility of micro-explosion also increased due to the mixing of fuel. On the other hand, increasing the chamber pressure also resulted in shorter ignition delay, higher burning rate, and higher combustion temperature. The higher ambient pressure also compressed the flame dimension and enhanced the onset of micro-explosion. HIGHLIGHTS The adding of biodiesel into petroleum diesel with different physical and chemical properties impacts the droplet combustion behavior, especially on the characteristics of burning rate, ignition delay time, flame temperature, and micro explosion The high content of unsaturated fatty acids and oxygen in Philippine Tung biodiesel improves the ignition delay time and burning rate constants of the blended fuel, but, the lower heating value causes the lower flame temperature The multi-components of fatty acids with different boiling points in Philippine Tung oil promote the micro-explosion in the combustion of the mixtures of biodiesel and petroleum diesel fuel GRAPHICAL ABSTRACT