JPS55151199A - Electric fan - Google Patents

Abstract

PURPOSE: To lower the noises produced by an electric fan during its low flow-rate operation, by forming clearance between a volute tongue and a volute wall with an angle greater than 90 degrees to the tangential line of impeller drawn in the direction of its rotation, so that air or gas is made to flow smoothly from the volute passage toward impeller but air or gas flow in the opposite direction is hindered substantially.

CONSTITUTION: In the state that an electric fan is operated in its low flow-rate region, air is drawn from volute passage 18 and introduced through clearance 17 to a region on the inner wall surface of volute tongue 12 and volute wall 13 where separation of flow is caused. Here, the clearance 17 is formed between volute tongue 12 and volute wall 13 to extend with an angle substantially equal to about 135° (greater than 90°) to the tangential line of impeller 8 drawn in its counterclockwise direction of rotation. With such an arrangement, air is made to flow smoothly from volute passage 18 toward impeller 8 but the opposite air flow is hindered substantially, so that there is formed an air flow through clearance 17 for removing separation of flow. Therefore, it is enabled to lower the noises produced during low flow- rate operation of fan, without causing drop in the efficiency of fan.

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