Laser-induced breakdown spectroscopy measurement in methane and biodiesel flames using an ungated detector

Laser-induced breakdown spectroscopy (LIBS) has been applied to measure the equivalence ratio of CH4/air flames using gated detection. In this work, we have developed an ungated, Miniature LIBS-based sensor for Studying CH4/air and biodiesel flames. We have used this sensor to characterize the biodiesel flame. LIBS spectra of biodiesel flames were recorded with different ethanol concentrations in the biodiesel and also at different axial locations within the flame. The sensor performance was evaluated with a CH4/air flame. LIBS signals of N, O, and H from a CH4/air flame were used to determine the equivalence ratio. A linear relationship between the intensity ratio of H and O lines and the calculated equivalence ratio were obtained with this sensor. (C) 2008 Optical Society of America