ARTICLE pubs.acs.org/EF
Experimental and Detailed Kinetic Modeling Study of the Effect of Ozone on the Combustion of Methane F. Halter,*,† P. Higelin,† and P. Dagaut‡ † ‡
PRISME, Universite d’Orleans, Polytech Vinci 45072 Orleans cedex, France Institute for Engineering and Systems Sciences (INSIS), Centre National de la Recherche Scientifique (CNRS), 1C, Avenue de la Recherche Scientifique 45071 Orleans cedex 2, France
bS Supporting Information ABSTRACT: New experimental results were obtained to better assess the effect of ozone on the burning velocity of premixed methaneair flames at atmospheric pressure and room temperature. Ozone was produced using a dielectric barrier discharge device, and its quantity was fixed equal to 5 g/Nm3 in air (2369 ppm of ozone). Measurements were performed using a Bunsen burner. Simultaneous to flame height measurements, a 1D Rayleigh scattering system was set up to investigate the impact of ozone on the thermal flame structure. The experimental results showed that the partial conversion of molecular oxygen into ozone has a moderate positive effect on the burning velocity of methaneair flames, confirming previous measurements in the literature. The injection of 5 g/Nm3 of ozone in air increased the burning velocities by ca. 0.81.3 cm/s (ca. 38%). The oxidation of methane in the presence or absence of ozone was modeled using a detailed chemical kinetic scheme taken from the literature, to which an ozone submechanism was added. The computations agreed well with the present set of experimental data and represented the trends previously reported in the literature. Kinetic modeling was used to rationalize the present results and predicts increasing burning velocities with increasing air ozonization.
1. INTRODUCTION Plasma-assisted combustion is an emerging technology that could be widely used to control ignition and extend the range of flame stability under a wide range of conditions.3,4 That technique could be particularly useful for operating under fuel-lean or very lean conditions, where NOx and particulate emissions are reduced, without facing extinction and stability issues. Whereas close plasma-flame coupling can be highly efficient enhancing combustion through injection of short-lived excited species and electrons, injection of long-lived species, such as ozone, might be more practical on the short term and for upgrading existing combustion devices. It is well-known that ozone is readily produced from molecular oxygen in plasma discharge.5 Its effect on the combustion of hydrocarbons has been studied previously. Many of these studies concern methane. Rotzoll6 studied the oxidation of methane in the presence of ozone in a microreactor (0.6 bar and 480830 K) and showed through kinetic modeling that the reaction is initiated by ozone decomposition, producing O atoms. Nomaguchi and Koda1 measured the burning velocity of methaneair (79% N2 and 21% O2) mixtures at room temperature and atmospheric pressure for equivalence ratios in the range of 0.851.25 using a nozzle burner. They measured burning velocities with a 0.2% ozone fraction of oxygen, which were higher by
