Variable critical flow venturi.

摘要

A variable critical flow venturi capable of improving the controlling accuracy of a movable member (3) provided in a venturi tube (2) in position is described. Said venturi tube (2) smoothly reducing a sectional area of passage thereof along a flow direction (F) of gas to arrive at a throat portion (1) having the minimum sectional area and then smoothly increasing said sectional area of passage thereof along said flowing direction (F) from said throat portion (1). The movable member (3) is dislocatably provided along an axial direction of the venturi tube (2) and an outer circumferential surface of said movable member (3) has a multi-stepped shape comprising a plurality of cylindrical portions (4, 5, 6) different in diameter and a plurality of truncated conical portions (7,8) connecting said cylindrical portions (4, 5, 6). <IMAGE>