Effects of electrode configurations on the combustion characteristics of premixed methane-air flames

The present paper reported the effects of electric fields produced by the mesh, ring and needle electrodes on outwardly propagating premixed flames in a constant chamber. The input voltages were 0 kV, -5 kV, -10 kV, -12 kV, and the excess air ratios of methane-air mixture were 0.8, 1.0 and 1.2, respectively. The electric field distributions developed by the three electrode configurations all affected the flame propagation in the horizontal direction rather than in the vertical direction. The electric field strength for the mesh electrode in the region between the high-voltage electrodes was the largest, and that for the ring and needle electrode decreased in turn. Under the application of the electric field, the flame front was stretched remarkably and the flame speed was accelerated significantly as the input voltage increased. For the three electrode geometries, the increase of the flame speed for the mesh electrode was the largest, followed by that for the ring and needle electrodes. For various excess air ratios, the increase of the flame speed at lean mixture was the largest, that at rich mixture the less large and that at stoichiometric mixture the smallest. By analyzing the effects of the three electrode geometries on pressure data, it was seen that the applied electric field could markedly enhance the combustion pressure growing up, and the timing of the peak pressure was advanced with the increase of the input voltage. The promotion effect on the combustion is most pronounced for the mesh electrode, while that for the ring and needle electrodes decreased in turn. For the various excess air ratios, the electric field most significantly enhanced the combustion pressure growing up at lean mixture.