Experimental Characterization and Modeling for Equivalence Ratio Sensing in Non-premixed Flames Using Chemiluminescence and Laser-Induced Breakdown Spectroscopy Techniques

Abstract

Real-time monitoring of the local equivalence ratio is of primary importance for combustion efficiency improvement. Chemiluminescence and laser-induced breakdown spectroscopy (LIBS) measurements can be powerful tools for sensing the equivalence ratio. Radicals, such as OH*, CH*, and C2*, are formed within the flame front, and consequently, the related chemiluminescence emission can be considered as a marker to follow the evolution of combustion processes. From LIBS measurements, the ratio of two characteristic spectral lines of fuel (H) and oxidizer (O) is related to the equivalence ratio. In this work, LIBS measurements have been carried out in premixed flames of known equivalence ratio for calibration purposes. Then, the application to non-premixed flames has been performed to evaluate the local equivalence ratio. Chemiluminescence emission spectra have also been collected, and the values of OH*, CH*, and C2* have been properly evaluated, taking into account the contribution of CO2* broad band emission....