US3574480A

US3574480A - Semiaxial fan rotor

Info

Publication number: US3574480A
Application number: US778445A
Authority: US
Inventors: Leo Hoepfner
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1968-10-08
Filing date: 1968-11-25
Publication date: 1971-04-13
Anticipated expiration: 1988-04-13
Also published as: DE6801232U; NL6816027A; FR1603979A; GB1206328A

Abstract

The vanes of a fan rotor have an outer contour shaped as a circular arc concentric to the hub axis of the rotor, whereas the inner contour of the vanes, where the vanes are joined with the hub, have a curvature reversed with respect to that of the outer contour. The outer region of the fan rotor acts essentially as an axial fan, whereas on account of the reversal and curvature the inner region of the vanes produces a radial fan action.

Description

1L2"; United States at t [72] lnventor Leo Hoepfner Neustadt, Aisch, Germany [211 Appl. No. 778,445 [22] Filed Nov. 25, 1968 [45] Patented Apr. 13, 1971 [73] Assignee Siemens Aktiengesellschaft Berlin, Germany [32} Priority Oct. 8, 1968 [33] Germany [31] G 68 01 232.8

[54] SEMIAXIAL FAN ROTOR 4 Claims, 3 Drawing Figs.

[52] US. Cl 415/209, 415/219 [51] Int. Cl ..F04d 25/16, F04d 25/06 [50] Field of Search 230/ l 34, 119,127; 103/88;415/209 [56] References Cited UNITED STATES PATENTS 1,015,274 1/1912 Keith 230/134 Primary Examiner1'1enry F. Raduazo Att0rneysCurt M. Avery, Arthur E. Wilfond, Herbert L.

Lerner and Daniel]. Tick ABSTRACT: The vanes of a fan rotor have an outer contour shaped as a circular arc concentric to the hub axis of the rotor, whereas the inner contour of the vanes, where the vanes are joined with the hub, have a curvature reversed with respect to that of the outer contour. The outer region of the fan rotor acts essentially as an axial fan, whereas on account of the reversal and curvature the inner region of the vanes produces a radial fan action.

PATENTEU APR 1 3 P-Tl SEMIAXIAL FAN ROTOR My invention relates to fan rotors. Such rotors are available substantially in two general types: as axial fans and radial fans. It is known that axial fans deliver large quantities of air at relatively low pressure, as compared with radial fans which deliver relatively small air quantities at higher pressure.

There are, however, conditions under which it is desirable to move large quantities of air but to have the air leave the fan in the radial direction. This is the case, for example, for such purposes as the ventilation of rooms and various encased equipment. It is then necessary to guide the output jet of air coming from an axial fan by baffles or other air-guiding members so that it will issue from the fan in radial directions. This entails considerable power losses or unduly reduces the quantity of air being exhausted. The use of a radial fan, as a rule, is not well suited for such purposes because the delivered quantity of air is too small.

It is an object of my invention to devise a fan rotor which possesses the high delivering ability of an axial fan, but which also affords producing high pressures and causes the air to leave the rotor with an already considerably radial component.

To achieve these ends, and in accordance with a feature of my invention, the vanes of the fan rotor are given the profile of a substantially circular arc in their outer region but are so shaped that they exhibit a reversal in profile toward the hub member or axis of the fan rotor. The outer peripheral contour in the shape of a circular arc imparts to the vanes the action of an axial-type fan rotor, whereas the inverse curvature toward the interior of the rotor has the effect of producing a radial component of the air being delivered.

It has been found particularly favorable, and constitutes another, more specific feature of the invention, to have the vane leading edge extend at an angle of about l to the radius from the axis to the vane tip, and to have the trailing edge extend approximately in the radial direction.

For hydraulic-technological and manufacturing reasons, it is further of advantage to give the hub member of the rotor an approximately conical or frustoconical shape, and to provide it with only as many vanes as will not cause overlapping of these vanes.

According to a further feature of my invention, a particularly good air distribution is attained if, seen in the flow direction, the vanes have approximately 40 to 60 percent of their axial extent protrude out of the housing jacket, and if a baffle plate is placed at some distance behind the vanes in the rotor plane. Preferably, a baffle plate is joined with the jacket portion of the fan housing and serves also as fastening means for the drive motor of the fan.

The invention will be further described with reference to an embodiment of a fan rotor assembly according to the invention illustrated, by way of example, in the accompanying drawing, in which:

FIG. 1 is an inclined perspective view of the fan rotor;

FIG. 2 is the top view of the same rotor; and

FIG. 3 is a side elevation of the rotor assembled with the housing jacket and a baffle plate, the jacket being shown partly in section.

As illustrated, the hub member 1 has a generally frustoconical shape and carries a number of vanes 2 each having a trailing edge 3 and a leading edge 4. The vanes have a profile substantially in the shape of a circular are at their outer region, the are having the radius +R, for example. Each vane further is so shaped as to reverse the curvature of its profile from the outer periphery toward the shaft 5 and hence toward the axis of the rotor. For example, the vanes are given a profile which along the hub member 1 is substantially in the shape of a circular arc having the radius -r. It will thus be seen that whereas the peripherally outer contour of each vane is convex if seen from above in FIG. 1, the contour of the same vane at the surface of the hub member 1 is concave. Such a rotor combines the properties of a radial fan with those of an axial fan and hence ma also be called a semiaxial rotor."

The leading ge 4 of each vane forms an angle of approximately 15 with the radius extending from the rotor axis to the vane tip. In other words, the extension of the leading edge 4 inwardly does not intersect the rotor axis 5 but forms an angle of about 15 with the radius issuing from this axis. It will further be seen from the drawing that the vanes 2 are not mounted in mutually overlapping relation. This is favorable from the air-hydraulic viewpoint because it secures a uniformly good efficiency together with many working points; and is also advantageous from the viewpoint of manufacture, for example when the rotors are made of synthetic plastic and are to be pulled out of an injection mold.

As is apparent from FIG. 3, the vanes 2, seen in the direction of the airflow l0, protrude with approximately 60 percent of their axial extent out of the housing jacket 9, that is, most of the axial width or depth of the vanes is located outside of the jacket 9. In the plane of the rotor, and spaced from the rotor approximately 40 to 60 percent of the just-mentioned width or depth, there is mounted a baffle plate 6 which serves to guide the airflow and promotes the proper development and guidance of the radial flow component. If the axial spacing between baffle plate 6 and rotor is too small, flow losses will occur; on the other hand, if this spacing is too large, then the formation of eddies or whirls at the baffle plate may likewise result in such losses. The above-mentioned spacing of approximately 40 percent of the axial depth of the rotor vanes has been established by tests to be particularly favorable in these respects.

The baffle plate 6 also carries the drive motor 7 and is joined with the housing jacket 9 by means of spacer pins or bolts 8 distributed about the periphery of the plate 6.

The entire assembly can be installed, for example, above an opening in the ceiling of a room. The inducted quantity of air is delivered into the room in a uniform distribution by rotation of the rotor in the direction of the arrow 11.

Upon a study of this disclosure it will be obvious to those skilled in the art that with respect to construction details my invention may be given various other embodiments than the one illustrated and described herein, without departing from the essential features of theinvention and within the scope of the claims annexed hereto.

Iclaim:

1. In combination with a fan rotor having a central hub portion and fan vanes mounted on and peripherally distributed about said hub portion and protruding outwardly away therefrom, the improvements according to which said fan vanes each have contour surface means for providing a substantially axial fan action in said outer region and a substantially radial action near said hub portion, a housing jacket coaxially surrounding said rotor, said vanes having approximately 40 to 60 percent of their extent protruding out of said jacket in the direction of the airflow, and a baffle plate mounted in axially spaced relation from said vanes at the protruding side thereof and extending in a plane perpendicular to the rotor axis.

2. In a fan rotor according to claim 1, the spacing between said vanes and said baffle plate being approximately 40 to 60 percent of the axial extent of said vanes.

3. In a fan rotor according to claim 1, said baffle plate being firmly joined with said housing jacket and forming a support for a fan drive motor.

4. In a fan rotor according to claim 1, said fan vanes each having a peripheral edge outlining said surface contour means, said peripheral edge having a circular-arc profile at the radially outer region of said vane and a profile reversal toward the hub axis at the forward edge of said vane.