Electric field control of soot distribution in flames using laser-induced incandescence

A laser-induced incandescence (LII) diagnostics system with 2-color calibration unit was set up. The system used a high-energy laser pulse to heat the soot particles in flame up to 3500-4000 K and induced the incandescence, then used the 2-color calibration unit to find the relationship between light intensity and absolute value of particle volume fraction, and finally get the 2-D image of soot particle volume fraction distribution. Based on this method, an optical experimental facility was set up to investigate the effect of electric fields on soot particle concentration in flames. With the presence of electric field, soot volume fraction will be decreased, but whatever it is negative or positive, the soot volume fraction will increase first because of the electric force below the value of ±6 kV. Ionic wind will take an important role to reduce the flame height and soot particles volume concentration after ±6 kV. Thermophoretic sampling particles diagnostics (TSPD) results show negative electric field is stronger than positive electric field in decreasing the soot volume concentration. When the voltage is -15 kV, the soot volume fraction is reduced to 10% of the value without electric field.