Stable shell device suitable for fan

The utility model belongs to the technical field of draught fans, and particularly relates to a stable shell device suitable for a draught fan, which comprises a flow guide bin, the lower end of the flow guide bin extends outwards along a flange outline to form a volute body, and a centrifugal impeller is arranged in the center of the flow guide bin; the centrifugal impeller comprises a wheel shaft, a shield and centrifugal blades which are coaxially arranged, the shield is coaxially connected with the upper end and the lower end of the wheel shaft, the wheel shaft is radially provided with a plurality of centrifugal blades, the outer edge of the shield is uniformly and vertically provided with a plurality of flow guide grids, the flow guide grids correspond to the centrifugal blades in the number direction, and the side face of the shield abuts against an angle adjuster used for adjusting the flow guide grids. The flow guide grid bars are arranged corresponding to the centrifugal blades in the number directi