Patent ID: 7686579

Claim:
A ducted fan that is mounted in an aircraft and serves as a device that produces a thrust for the aircraft, comprising: a fan, which generates an airflow that proceeds in a direction substantially parallel to an axial direction of a rotating shaft of the fan; a duct arranged around the fan extending in the axial direction of the rotating shaft, that has an airflow inlet defined by an upstream end and an airflow outlet defined by a downstream end, wherein a ramp portion is formed in an inner face of the airflow inlet of the duct; an airflow guide portion provided at the airflow outlet that introduces air, which blows against a side face of the duct from an outside of the duct, to a position downstream of the airflow outlet; and a negative-pressure forming portion provided at a downstream end of the airflow guide portion, that forms a negative pressure in an area near the downstream end of the airflow guide portion when the air introduced by the airflow guide portion passes by the negative-pressure forming portion, wherein: the airflow guide portion is a cylindrical member; and an outer diameter of the airflow guide portion is less than an outer diameter of the duct.