Centrifugal Fan

Abstract

An axial inlet for a centrifugal fan is provided with an inlet cone-shaped to converge at a distance in front of the inlet opening of the wheel sideplate to a diameter less than the diameter of the wheel inlet opening and then reversely curved to terminate adjacent the edge of the wheel sideplate opening. A seal plate may extend from around the exterior of the reversely curved portion of the inlet cone in a manner to overlap the front of the wheel sideplate and an inside edge of the sideplate opening wall may be chamfered towards the interior of the wheel in the direction of the periphery of the wheel.

Description

BACKGROUND OF THE INVENTION

It is known that the performance of an axial inlet centrifugal fan is related to the effectiveness with which the fan blades are loaded or in other words the effectiveness with which the inlet air is distributed uniformly over the full extent of the nose portions of the fan blades. The problem with an axial inlet fan is that the inlet air must be turned into the fan blades in a manner to uniformly distribute the air over the fan blading and there also must be a minimum of air leakage at the side plate inlet opening of the fan wheel.

PRIOR ART

Reference may be made to the U.S. Pat. No. 3,285,501 issued to McDonald on Nov. 15, 1966 which discloses a prior arrangement of inlet cone for an axial inlet centrifugal fan that is however more complex and difficult to manufacture than the arrangement of the subject invention.

SUMMARY

In accordance with the invention, the inlet cone for an axial inlet centrifugal fan is shaped to provide an effective boundary layer control for turning the inlet air to thereby uniformly load the fan blading. In addition, a seal plate together with a specified shaping of the wheel sideplate opening surface is provided to obtain an effective inlet air seal at the wheel sideplate. The centrifugal fan of the invention is of the type mounted in a casing and having a sideplate axial inlet opening for the fan wheel within the casing. One wall of the casing is formed as an inlet cone-shaped to converge at a distance in front of the inlet opening of the wheel sideplate to a diameter less than the diameter of the wheel inlet opening and then reversely curved to terminate adjacent the edge of the sideplate opening. In order to minimize leakage of air from around the inlet opening of the wheel sideplate, a seal plate is positioned to extend from around the exterior of the reversely curved portion of the inlet cone in a manner to overlap the front surface of the wheel sideplate. In order to further define a boundary layer control, an inside edge of the sideplate opening of the wheel may be chamfered toward the interior of the wheel in the direction of the nose portions of the fan blade and the periphery of the wheel.

Further features and advantages of the invention will be apparent with reference to the following specification and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view in section of a centrifugal fan embodying this invention;

FIG. 2 is an end view of the fan of FIG. 1 looking at its inlet end; and

FIG. 3 is an enlarged fragmentary view in section of the curved portions of the inlet cone showing details of the seal plate and chamfered edge of the radial sideplate opening of the wheel.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2 of the drawings it will be seen that the centrifugal fan of the invention is comprised of the fan casing generally shown at 10 within which is journaled a fan wheel generally shown at 11 mounted for rotation on the shaft 12. The casing 10 is provided with the inlet wall 13 and the outlet from the fan issues through the opening 14 of the casing 10. The fan wheel generally shown at 11 is provided with a back plate 15 and a front sideplate 16 between which are fastened a plurality of blades such as shown at 17 and 18. The front sideplate 16 is provided with an axial inlet opening shown at 20 and the inlet cone 13 of the housing 10 is generally coaxial with the fan wheel inlet opening 20.

Referring now more particularly to FIG. 3 of the drawing it will be seen that the inlet cone 13 converges to a point 24 which is of less diameter than the diameter of the sideplate opening 20 at a position in front of the wheel sideplate 16. From the point 24 the inlet cone is reversely curved as shown to terminate at 25 adjacent the wheel inlet opening 20. In the preferred embodiment of the invention the point 25 at the inner end of the inlet cone 13 is curved to extend generally in alignment with the plane of the sideplate 16.

A seal plate 30 is secured by any suitable means such as welding to the exterior of the reversely curved portion of the inlet cone at the point 31 in a manner to overlap the front side of the wheel sideplate 16.

In the preferred form of the invention the inlet opening wall 20 of the sideplate 16 of the wheel is chamfered as shown at 35 to be angled inwardly toward the blade nose 36 and the periphery of the fan wheel.

As previously mentioned the provision of the smoothly curving surfaces of the inlet cone as shown from the point 24 to the point 25 provides a boundary layer effect to aid in turning the inlet air in a manner to uniformly load the noses of the fan blading. The combination of the overlapping seal sideplate 30 and the chamfered edge 35 of the sideplate opening also provides for an effective sealing of the air around the wheel inlet opening and assist in the boundary layer action to distribute the inlet air uniformly over the fan blade nosing.

Various modifications will occur to those skilled in the art.

Claims

I claim:

1. A centrifugal fan comprising a casing, a fan wheel supported for rotation within said casing, said wheel having a radial sideplate with an opening forming an axial circular wheel inlet, the inside edge of said sideplate opening being chamfered towards the interior of the wheel in the direction of the periphery of the wheel, said casing having a wall forming an inlet cone concentric with said wheel inlet opening, said cone being shaped to converge at a distance in front of the wheel inlet opening to a diameter less than the diameter of said wheel inlet opening and then reversely curved to terminate adjacent the edge of the wheel sideplate opening substantially wholly within the confines of those radial planes defining the inner and outer axial limits of the chamfered portion of the sideplate opening for improving boundary layer control through said inlet.

2. The invention of claim 1 in which a seal plate extends from around the exterior of the reversely curved portion of said inlet cone in a manner to overlap the front of the wheel sideplate.