Annular air supply device for reducing vortex strip of draft tube of axial-flow fixed-paddle water turbine

The invention relates to the field of water turbine equipment, in particular to an annular air supply device for reducing a vortex strip of a draft tube of an axial-flow fixed-paddle water turbine, the annular air supply device comprises an annular tube, a connecting pipeline and an air supply main pipeline, the annular tube is arranged in the draft tube, and a plurality of air supply holes are formed in the annular tube; an air outlet of the connecting pipeline is communicated with an air inlet of the annular pipe, an air inlet of the connecting pipeline is communicated with the main air supply pipeline, the outer wall of the connecting pipeline is connected with a draft tube, and the air outlet of the connecting pipeline is inclined upwards; during natural air supply, the vent valve is in an open state, and during forced air supply, the vent valve is in a closed state. Air can be uniformly supplemented into the draft tube, the pressure pulsation phenomenon of the draft tube caused by a vortex strip formed i