We experimentally investigated the effects of DC electric field（U=10 k V） on flame propagation and combustion characteristics of premixed expanding CH

4

/O

2

/N

2

flames with equivalent ratio of 1.0 on the constant volume combustion bomb

so as to better understand the roles of electric field spatial distribution in the effects of electric field on flames.Five different electric field distributions will exist by changing voltage polarity of the two mesh electrodes

which are both negative（DN）

both positive（DP）

right positive and left negative（RPLN）

right positive and left ground（RP） and left negative and right gro

und（LN）. Flame front can be obviously stretched towards both the mesh electrodes by DN

DP and RPLN

while it can only be stretched towards one side by RP and LN where the electric field exists. The most effective electric field on flame propagation is DN

under which the normalized flame deformation ratio increases by 30.01% compared to that in the absence of electric field. The peak pressure time tp can be advanced and both the initial combustion duration tid and main combustion duration tmd can be shortened by DN

DP

RPLN

LN

and RP. RPLN affects tp most obviously

and tp is advanced by 6.97%. The most effective electric field distribution on tid is DN which can shorten by 12.94%

and in turn is RPLN

LN

DP and RP. The top three of the most effective on tmd are LN

DN and DP

and tmd is shortened by 7.25%

7.06%

and 6.49%

respectively.