Air exhaust mechanism for granary ventilation system

The invention discloses an air exhaust mechanism for a granary ventilation system. The air exhaust mechanism comprises a fan housing and a main housing opening and closing door, wherein the fan housing is arranged in a ventilation duct of a granary wall body and looks like a circular truncated cone; a housing air duct is arranged in the fan housing; the small-diameter end of the fan housing is a fan housing air inlet end communicated with the inside of a granary; the large-diameter end of the fan housing is a fan housing air exhaust end communicated to the outside of the granary; a motor and an impeller are arranged in the housing air duct; the impeller is coaxially connected with a rotating shaft of the motor; a housing sealing ring is arranged between the fan housing and the ventilation duct of the granary wall body; the main housing opening and closing door is used for closing the fan housing air exhaust end; one side of the main housing opening and closing door is hinged to the granary wall body. The air