In this work

the effects of the electric fields on the flame propagation and combustion characteristics of methane-air mixtures were experimentally investigated in a constant chamber. The loading voltages were 0

-5

-10 and -12 kV

and the excess air ratios (λ) of mixtures were 0.8

1.0 and 1.6

respectively

representing the three mixed gas states of rich combustion

equivalence ratio and lean combustion. The experiment was performed at room temperature and atmospheric pressure. When the electric field was applied

the flame front in the electric field direction was remarkably stretched

the flame development radius and flame propagation velocity were all accelerated significantly as the loading voltage increased

and the flame shape was changed remarkably. Especial for the lean mixture

the increase of flame development was most obvious. For the mixtures of λ=0.8

1.0 and 1.6 at -12 kV

the maximum values of flame propagation velocity were increased by 42.3%

29.7% and 111.7%

respectively. By analyzing combustion pressure variation

it could be seen that the time of peak combustion pressure (tp) was advanced

and the peak pressure (Pmax) of lean mixture increased with the increase of loading voltage. For the mixtures of λ=0.8

1.0 and 1.6 at -12 kV

tp were advanced by 13.4%

7.5% and 24.6%

Pmax increased by 2.2%

1.0% and 8.1%

respectively

compared to that when no voltage was applied. The results could be explained by the ionic wind effects produced by the electric fields and its induced flame stretch on burning methane-air mixtures.