Local equivalence ratio measurements in turbulent partially premixed flames using laser-induced breakdown spectroscopy

One of the most recently applied laser-based techniques in combustion environment is the laser-induced breakdown spectroscopy (LIBS). The technique has been extensively and successfully applied to elemental concentration measurements in solids and liquids. The LIBS signal is much weaker in gases and hence more work is required for quantitative measurements in flames. In the present work we used two orthogonal Nd:YAG lasers that operate at the fundamental wavelength with laser pulse energy of about 100 mJ/pulse. A Princeton-Instruments IMAX ICCD camera attached to a PI-Echelle spectrometer was used for signal detection. The lasers are focused using two 5-cm lenses. Several calibration points have been collected in well defined and homogeneous mixtures of air and fuel in order to be used as references for the measurements in turbulent partially premixed flames. This work shows that the application of the LIBS technique in a turbulent combustion environment is feasible and signal is enhanced by applying an orthogonal dual-pulse arrangement for air–fuel.