Pool fire burning characteristics of biodiesel

The characteristics of pool fire burning of methyl esters/biodiesels of palm, soybean, coconut and their blends with diesel were compared against baseline diesel. Pool fires were established and investigated using four different crucible sizes, ranging between 40 mm and 70 mm in diameter to obtain the mass burning rate, flame height and emissions of NO, CO, and SO₂ under diffusional flame mode at unconfined atmospheric conditions. The mass burning rate increased with increasing crucible size for all tested fuels, with biodiesel showing higher mass burning rates when compared with diesel. Modified empirical correlations for estimating fuel mass burning rate and flame height showed good agreement with experimental data. Emission-wise, biodiesels generally exhibited higher specific NO emission level than baseline diesel. Blending biodiesel with diesel resulted in an increase of NO level. CO emissions showed a reverse trend, where diesel showed higher emission values than all biodiesels. Burning of neat palm and coconut biodiesels showed non-existent SO₂ emission. The experiment showed that the oxygen content in biodiesel assists in pool fire combustion, as evident by the higher mass burning rate as compared to diesel. Soybean biodiesel with higher density exhibited higher mass burning rate as compared to palm and coconut biodiesels. Biodiesel with high level of unsaturation produced lower NO but higher CO emissions.