Methane Oxidation in a Low-Current Nonsteady-State Plasmatron

Abstract

This paper describes the results on methane oxidation in the plasma torch of low-current plasmatron at typical air expenditure of 0.1–0.55 g/s and at a flow velocity in a longitudinal direction up to 22 m/s. The discharge in a vortex gas flow burns in a glow regime with the spontaneous transitions from glow to spark. Due to special design of the plasmatron nozzle (with a ring groove at the inner surface of the nozzle), an efficient interaction of the gas flow with plasma column and the reproducible data on chemical gas composition in a combustion chamber are provided. An average discharge current in the plasmatron was varied from 0.05 to 0.2 A, which corresponded to an average power dissipated in the discharge from 60 to 150 W. A heat power due to fuel burning in the plasma torch was at a level of 1 kW. The data on chemical gas composition in the combustion chamber in a wide range of air excess coefficient <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\alpha \) </tex-math></inline-formula> had been obtained. For the lean air-to-fuel compositions (that is for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\alpha &gt; 1\) </tex-math></inline-formula> ), the lower flammable limit was of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\alpha \approx 3\) </tex-math></inline-formula> . In a regime of syngas generation, i.e., for the rich air-fuel mixtures, the upper flammable limit was of about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="TeX">\(\alpha \approx 0.55\) </tex-math></inline-formula> . It is demonstrated that both the low and the upper flammable limits depend on the discharge current.