Gas-air mixing device for combustor

An air and gas mixing valve for a water heater, the mixing valve comprising,

• a housing connected on one side to a turbo fan and provided with a space of a predetermined size in the interior thereof through which gas and air can flow;
• a discharge part disposed on the one side of the housing and in contact with the turbo fan;
• a first air supply part and a second air supply part disposed on another side of the housing and separated by a first partition, for suctioning outside air;
• a first gas supply part and a second gas supply part separated by a second partition, for supplying gas which mixes with air flowing in from the first air supply part and the second air supply part and discharged via the discharge part, wherein the second gas supply part has an upper end disposed at the same height as an upper end of a protruding part protruding for a predetermined length from an upper portion of the second partition;
• and
• an opening/closing means for blocking flow of gas and air by closing the second air supply part and the second gas supply part in a low-output mode, and for opening the second air supply part and the second gas supply part in high-output mode,
• wherein the opening/closing member comprises a valve body for closing the second air supply part and the second gas supply part by being in contact with the upper ends of the second gas supply part and the protruding part when moving downward, and for opening the second air supply part and the second gas supply part when moving upward.