Ablating soot extinction characteristics diagnosis using laser induced incandescence and light extinction methods

In order to study the extinction effect of ablating soot produced by carbon fiber reinforced composite materials, which are located in an air flow field and are irradiated by laser, Laser induced incandescence (LII) and laser extinction methods are employed. Experiment is set up to diagnose the soot extinction characteristics combining these two methods. In the experiment, a laser light is set in the excitation plane of LII, then laser transmittance and LII signals are recorded synchronously to obtain the laser extinction ratio and soot concentration field. From these data, the mean mass extinction coefficients of soot are derived at a series of air flow velocities. The normalized mean mass extinction coefficient values of soot for 1064 nm laser are 2.51, 1.08, 1.00 at air flow velocities 7 m/s, 10 m/s, 20 m/s, respectively. When the air flow velocity is low, the amplitude of N curve fluctuation is big, and the mean value is big too. When the air flow velocity is high, the N curve fluctuation is slight, and the mean value is small.