The blowing device includes an impeller that is rotatable about a center axis and a motor that drives the impeller. The impeller includes a plurality of vanes arranged in a circumferential direction, a flange in which the plurality of vanes are provided at the outer circumferential edge in a radial-direction outside, and a plate-shaped first shielding unit located between the vanes adjacent to each other in the circumferential direction. The first shielding unit is connected to a rear edge surface on an opposite side to the rotation direction of the vane and an outside surface located on the radial-direction outside of the flange.

A hollow forging process for main shaft of large wind turbine generator, wherein, comprising the following steps as: the first step of cutting off the dead head and the bottom of an ingot; the second step of upsetting and punching a hole; the third step of drawing-out; and the fourth step of local upsetting, drawing-out and shaping-up. In the fourth step, the forged piece is shaped up by local upsetting and drawing-out through a turnplate. The hollow forging process for main shaft created by the invention can save the costs for enterprise to purchase large equipment and makes it possible to forge the main shaft of large wind turbine generator with a free forging oil press with a smaller size.

The blowing device includes an impeller that is rotatable about a center axis and a motor that drives the impeller. The impeller includes a plurality of vanes arranged in a circumferential direction, a flange in which the plurality of vanes are provided at the outer circumferential edge in a radial-direction outside, and a plate-shaped first shielding unit located between the vanes adjacent to each other in the circumferential direction. The first shielding unit is connected to a rear edge surface on an opposite side to the rotation direction of the vane and an outside surface located on the radial-direction outside of the flange.

A hollow forging process for main shaft of large wind turbine generator, wherein, comprising the following steps as: the first step of cutting off the dead head and the bottom of an ingot; the second step of upsetting and punching a hole; the third step of drawing-out; and the fourth step of local upsetting, drawing-out and shaping-up. In the fourth step, the forged piece is shaped up by local upsetting and drawing-out through a turnplate. The hollow forging process for main shaft created by the invention can save the costs for enterprise to purchase large equipment and makes it possible to forge the main shaft of large wind turbine generator with a free forging oil press with a smaller size.

Provided is a forged material for a rotor for obtaining, by machining, a rotor including a hub portion and a plurality of blade portions. The forged material for a rotor comprises a hub forming section and a plurality of blade forming sections that one-to-one correspond to the plurality of blade portions. The plurality of blade portions each comprise a first end face that faces an outer peripheral surface of the hub portion and a second end face opposite from the first end face. The plurality of blade forming sections each comprise a blade-shaped surface having a shape that follows at least part of a contour of the second end face of the one-to-one corresponding blade portion.