Title :
Direct-Coupled Plasma-Assisted Combustion Using a Microwave Waveguide Torch
Author :
Hammack, Stephen ; Rao, Xing ; Lee, Tonghun ; Carter, Campbell
Author_Institution :
Michigan State Univ., East Lansing, MI, USA
Abstract :
A tunable microwave waveguide is used to initiate and enhance combustion by coupling an atmospheric plasma discharge to a premixed methane/air flame. The absorbed microwave power ranges from 60 to 150 W, which was generated from a continuous source operating at 2.45 GHz, whereas combustion power ranges from 200 to 1000 W. OH radical number densities were measured using planar laser-induced fluorescence (PLIF), and temperatures were measured using Rayleigh scattering thermometry for various flow rates, equivalence ratios, and power levels. Increases in reaction volume, OH density, and temperature were observed as power increased. In the plasma-coupled premixed flame, OH number densities, which are quantified on the order of 1016 cm-3, increased by up to 50%, and temperature ranging from 2000 to 3000 K increased by up to 40% as the absorbed microwave power was increased from 60 to 130 W. Air-only plasma discharges exhibited a much greater temperature increase, i.e., up to 190%. The power associated with the measured temperature increases varied greatly with flow and input power but are typically three to four times greater in the air-only plasma compared to the flame coupled plasma, demonstrating a greater degree of nonthermal mechanisms present in plasma-enhanced flame discharge.
Keywords :
air; combustion; discharges (electric); flames; plasma chemistry; plasma density; plasma diagnostics; plasma filled waveguides; plasma flow; plasma temperature; Rayleigh scattering thermometry; air-only plasma; atmospheric plasma discharge; combustion; direct-coupled plasma-assisted combustion; equivalence ratio; flow rate; frequency 2.45 GHz; methane-air flame; microwave power; microwave waveguide torch; planar laser-induced fluorescence; plasma-coupled premixed flame; plasma-enhanced flame discharge; power 200 W to 1000 W; power 60 W to 150 W; radical number density; temperature 2000 K to 3000 K; Combustion; Discharges; Plasma temperature; Rayleigh scattering; Energetically enhanced combustion; Rayleigh scattering thermometry; microwave plasma; planar laser-induced fluorescence (PLIF); plasma-assisted combustion (PAC);
Journal_Title :
Plasma Science, IEEE Transactions on
DOI :
10.1109/TPS.2011.2161778