Utilization of Laser-Induced Breakdown Spectroscopy to Characterize the Combustion of Liquid Petroleum Gas Fuel in Special Design Burner

Abstract

The objective of this research was the utilization of laser induced breakdown spectroscopy (LIBS) technique in combustion characterization to measure local species concentration of carbon, hydrogen, nitrogen and oxygen in the flame of special designed burner beside the measurement of fuel /air ratio, and equivalence ratio. Q-switched-Nd: YAG Laser oriented in orthogonal configuration was used with another Q-swtiched-Nd: YAG laser, with similar parameters, to enhance LIBS signals detected from the flame. Each of these lasers has 10 ns pulse duration, 10 Hz repetition rate and 100 mJ energy per pulse. These lasers were applied to form plasma inside the flame. Spectrograph of ECHELLE type, combined with intensified charge coupled devices camera, was used to record the emission spectra of the combustion plasma. The stability curve for liquid petroleum gas (LPG) fuel in special design burner was deduced to characterize the combustion process for LPG in this burner, then mass fraction of the elements in the flame were calculated in additional to air/fuel ratio at different heights in the flame and through the width of the flame. The mass fraction profiles of the elements was deduced and from the mass fraction profiles of carbon and hydrogen the reaction zone of the flame was obtained to be range from ratio 2.5 to ratio 3 for the height 0.5 cm above the burner and from the ratio 2 to ratio 3 for the other heights. Nitrogen and oxygen masses fractions were calculated at the boundary of the flame (outside the flame), which were found to be 0.77 and 0.23, respectively. The mass fractions were found in good agreement with literatures. For the special design burner used in this work, the results showed that the combustion is rich because ϕ in the ring from 1to 2.5, for the ratio less than three.