Improvements in axial flow propeller blade rotors, in particular for axial flow fans

摘要

925,931. Axial-flow fans. S. M. F. ENG. DAHL. May 27, 1960 [May 28, 1959], No. 18825/60. Drawings to Specification. Class 110 (1). [Also in Group XXXIII] In an axial-flow fan impeller, in each blade section taken along a cylindrical surface coaxial with the axis of rotation of the impeller the camber line of the blade has the shape of an arc of a circle when the blade section is developed in a plane, the radius of curvature of the arc being the same for all blade sections; the width of each blade, substantially corresponding to the length of the chord of the camber line of the blade section when developed in a plane, decreases from hub to tip in inverse proportion to the square root of the distance of the blade section from the axis of rotation; and the pitch of each blade increases continuously from tip to hub. The angle of attack of the blades decreases continuously from hub to tip. The blades are of laminar or aerofoil form. Preferably the midpoints of the camber lines of each blade lie on a radius of the impeller.