The present research experimentally investigated the effect of different water droplet size on the burning behavior and extinction condition of concentric jet premixed and diffusion flame. Water droplet stream in line with flowing air from lower duct. The burning behavior of concentric jet flame was observed and the extinction of flame was gained by decreasing the flow rate of fuel until the flame exthinguised. The results showed that the burning behavior of concentric jet diffusion and premixed flame had the same tendency. Different water droplet size influenced the burning behavior of flame. Decreasing the water droplet size, luminosity of the flame became thin as well as reducing the flame height. However, the inhibition effect of water droplet was stronger for diffusion flame compared to premixed flame. For smaller water droplet size, water droplet was four times more effective for suppressing the diffusion flame than premixed flame
