Blowoff orifice

摘要

A blow-off orifice is constituted by an upper wall, a lower wall and a vertical wind deflecting plate (4a,4b). The upper wall inclines so that a flow passage becomes narrow toward downstream and provided with a protrusion (14) at its end portion. The lower wall has a horizontal linear portion (25) on the downstream side and an end portion forming an acute angle at the tip of the linear portion (25). The vertical wind deflecting plate (4a,4b) is provided between the upper wall and the lower wall, and capable of changing an airflow from a horizontal direction to a downward direction. The upper wall protrusion (14) is located more downstream than the lower wall end portion.