Soot measurement and application on diesel exhaust gas using laser-induced incandescence

In this study, we measured soot concentration by laser induced incandescence (LII). To obtain absolute soot volume fraction, laminar diffusion flames stabilized on a co-annual burner were used in calibration process. Our experimental conditions such as fuel and air flow rate were the same as those reported in the data base by National Institute of Standards and Technology (NIST). We used two types of Nd : YAG laser. One has powerful laser beam intensity, usually used in two-dimensional measurement. The other is small and portable, applicable for measurement in outer field. These systems are called system 1 and 2, respectively. For both cases, the LII signals were recorded by a ICCD camera. We applied this compact system to the soot measurement in diesel exhaust gas. For laminar diffusion flames, the measured instantaneous distributions of LII signals exhibit the similar profile of NIST data base. Since the calibrated soot volume fraction is the same as that measured by Artium LII 200, the reliability of our system is confirmed. In system 2, using the laser beam, the signal has enough S/N ratio. Results for diesel exhaust gas show that the monitored back pressure is larger when the engine speed (rpm) is increased, resulting in higher soot concentration. Additionally, the reduced soot concentration is recorded due to soot trap by a diesel particulate filer (DPF).