Investigation on the soot formation of biodiesel fuel by laser diagnostics

A burner fueled with liquid fuel was set up, which could produce a laminar diffusion flame. A two-color laser induced incandescence (2C-LII) technique was used for measuring absolute soot volume fraction in the flame. Based on LII signal of the same point in the flame recorded at two wavelengths, the temperature of the laser-heated soot particles was first derived and then the soot concentration of the point could be acquired. The 2D soot concentration distribution in the flame was obtained by mapping. The 2D concentrations of polycyclic aromatic hydrocarbons (PAHs) which are main precursor of soot were obtained by laser induced fluorescence (LIF). The laminar diffusion flames of diesel fuel and biodiesel/air were measured by 2C-LII and LIF. The result shows that with the increase of biodiesel proportion in the blended fuel, the maximum soot and PAHs concentration decrease as well as their distribution area.