Anti-backflow premixing device and fuel gas water heater

An anti-backflow pre-mixer, comprising:

• a housing provided with a premixing chamber that extends through the housing, the premixing chamber comprising an air outlet passage;
• a baffle connected to the housing, wherein the baffle has a first position and a second position, and the baffle is capable of moving continuously between the first position and the second position, the baffle blocks the air outlet passage of the premix chamber when the baffle is in the first position, when the baffle moves from the first position to the second position, an opening of the air outlet passage gradually increases;
• and
• a gas channel being in communication with the premixing chamber,
• wherein two premixing chambers are provided, the two premixing chambers are arranged side by side left and right, both of the premixing chambers are venturi tubes, and both of the premixing chambers are provided with the baffles,
• wherein the gas channel is provided with an adjusting device, and the adjusting device is configured to adjust a minimum flow area of the gas channel,
• wherein the adjusting device comprises a connecting portion and an adjusting portion connected to each other, the connecting portion is located on a peripheral wall of the gas channel and is rotatably connected to the housing, the adjusting portion is at least partially located in the gas channel, and the adjusting portion changes the minimum flow area of the gas channel with a rotation of the connecting portion
• wherein the gas channel comprises a first adjusting section and a second adjusting section that are connected in series in sequence, the first adjusting section and the second adjusting section are perpendicular to each other, the connecting portion is provided on a peripheral wall of the first adjusting section and is rotatably connected to the housing, and the adjusting portion is inserted into the second adjusting section, and
• wherein the gas channel is shaped as a circular tube, the adjusting portion is located at a junction of the first adjusting section and the second adjusting section, the adjusting portion is block-shaped, a cross-sectional area of the adjusting portion is adapted to a pipe diameter of the second adjusting section, and the adjusting portion is arranged eccentrically on the connecting portion.