Short tube gas replenishing device for draft tube of water turbine

The invention relates to a short tube gas replenishing device for a draft tube of a water turbine, belonging to the field of gas replenishing of a water turbine generator set. The short tube gas replenishing device for the draft tube of the water turbine is characterized in that the short tube gas replenishing device is arranged in the draft tube, passes through the tube wall of the draft tube through four branch tubes and is communicated with the atmosphere through an annular tube to form a gas replenishing loop; four short tubes are uniformly distributed on the same horizontal plane of the draft tube; and each short tube is in an upward arched form, i.e. each short tube forms an angle of 30-45 degrees with the upward horizontal plane or is parallel with the horizontal plane, each short tube is sealed by a plug, a gas outlet hole is formed below each short tube, and each gas outlet hole is positioned in the third quadrant of the cross section of each short tube seen from the center of the draft tube. The short tube gas replenishing device operates stably, and the gas replenishing quantity meets the requirement of the set. The short tube gas replenishing device does not generate the pipeline falling phenomenon, thereby reducing the daily maintenance, lowering the maintenance cost, avoiding the condition that the set operates without the gas replenishing device, and improving the safety and the stability of operation of the set.