Venturi nozzle and fuel supply device comprising venturi nozzle for controlling a ratio between a fuel gas and an air flow

A venturi nozzle, being disposed upstream from a blower, which is configured to mix combustion air and fuel gas by intake pressure of the blower, comprising:

• a nozzle portion with a shape that is narrowed in diameter to downstream and is configured for the combustion air to be introduced;
• a mixing portion, being disposed downstream from the nozzle portion, with a shape that is enlarged in diameter to downstream and is configured for the combustion air and the fuel gas to be mixed;
• and
• a fuel gas inlet disposed between the nozzle portion and the mixing portion and is configured for the fuel gas to be introduced, and
• a plurality of surfaces forming grooves or ridges disposed along a convexly curved inner surface of the nozzle portion, which extend in a circumferential direction of the inner surface of the nozzle portion, and are arranged at predetermined intervals in a flow direction of the combustion air,
• wherein each of the grooves or ridges is parallel to a central axis or perpendicular to the central axis.