Multiblade fan

Abstract

To provide a multiblade fan that enables an improvement in noise characteristics or blowing performance. The multiblade fan includes a scroll type casing that has a bell-mouthed inlet and an impeller housed in the casing. The impeller includes a plurality of blades and a rotation axis m oriented toward the inlet of the casing. The blades are annularly arranged. In the multiblade fan, a center axis of the inlet and the rotation axis of the impeller are arranged at a tilt angle to each other and in any one of an intersecting positional relationship and a skew-lines positional relationship so that a space between the inlet and the impeller increases from the rotation axis of the impeller toward an outlet of the casing.

Description

TECHNICAL FIELD[0001]The present invention relates to a multiblade fan, and more particularly, to a multiblade fan capable of improving noise characteristics or blowing performance.BACKGROUND ART[0002]A typical multiblade fan includes a scroll type casing having a bell-mouthed inlet and an impeller housed in the casing. The impeller is a multiblade impeller (sirocco fan) that includes a plurality of annularly arranged blades and that is housed in the casing with a rotation axis of the impeller oriented toward the inlet of the casing.[0003]In a structure where a center axis of the inlet and the rotation axis of the impeller are coaxially arranged, an inertial force is exerted on air flown into the impeller through the inlet. Hence, airflow inside the impeller is likely to be deflected toward a main plate (a plate that supports blades). Then, the velocity distribution (velocity distribution of air blowing out of the spaces between the blades) of the air passing through between the bla...

AI Technical Summary

Benefits of technology

[0013]In a multiblade fan according to an aspect of the present invention, a space between an inlet and an impeller increases from a rotation axis of the impeller toward an outlet of a casing. This configuration permits air that has flown into the impeller through the inlet to flow in a gentle curve inside the impeller to pass through between blades. This causes velocity distribution (deflection of airflow) of intake air inside the impeller and an incident angle of the intake air on a blade to relatively change, thereby making the velocity distribution of air having passed through between the blades uniform in the axial direction of the rotation axis of the impeller. Hence, the noise characteristics and the blowing performance are advantageously improved.

Problems solved by technology

Because this causes the velocity of flow to be likely to fluctuate, pressure differential of air or a level of air turbulence increases, which can result in louder noise or degradation in blowing performance.

Because this causes the impeller to function insufficiently, it is possible that the multiblade fan provides its blowing performance insufficiently.

However, these configurations are disadvantageous in that because the shape of a casing is complicated or it is difficult to release the casing from a die, cost of production increases.

Hence, changing the shape of the blades of the impeller is disadvantageous in being insufficiently effective.

This is because the changing the shape of the blades is effective for a target airflow; however, there are produced losses in air flows other than the target airflow.

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