Grooved draft tube for inhibiting hump characteristic of pump turbine and use method of grooved draft tube

The invention discloses a grooved draft tube for inhibiting hump characteristics of a pump turbine and a using method thereof, the grooved draft tube comprises a draft tube diffusion section (1), an elbow pipe (2) and a taper pipe (3) are sequentially arranged at the end of the draft tube diffusion section (1), c inner grooves (4) which are annularly and uniformly distributed are formed in the inner wall of the taper pipe (3), the inner grooves (4) are arranged along the inclined surface of the inner wall of the taper pipe (3), and the value range of c is 11-19; the radius from the upper edge of the inner groove (4) to the center of the taper pipe (3) is R1, the radius from the lower edge of the inner groove (4) to the center of the taper pipe (3) is R2, R2 = aR1, and a ranges from 1.00 to 1.10; according to the method, the draft tube can generate the working conditions of prerotation and poor internal flow in the hump area, the flow condition and the prerotation phenomenon of the draft tube are effectively i