GB2080879A

GB2080879A - Flow guides for centrifugal fans

Info

Publication number: GB2080879A
Application number: GB8121946A
Authority: GB
Original assignee: Wilhelm Gebhardt GmbH
Current assignee: Wilhelm Gebhardt GmbH
Priority date: 1980-07-28
Filing date: 1981-07-16
Publication date: 1982-02-10
Also published as: FR2487449B1; DE3028606C2; DE3028606A1; FR2487449A1; NL188595C; ATA176381A; CH656434A5; AT398813B; NL8101876A; GB2080879B; NL188595B

Abstract

A fan suitable for use in a duct in airconditioning and ventilation systems comprises a radial flow impeller (1) driven by a motor driven by a motor (2) and a guide structure (5) downstream from the outlet of the impeller which converts the radial flow from the impeller to an axial flow. <IMAGE>

Description

SPECIFICATION A fan unit for use with duct systems The present invention is with respect to a fan unit designed for use in duct systems as for example in ventilation and airconditioning systems, having a freely running radial impeller without a spiral casing and a driving motor for the impeller. Such fans may be fixed in ducting or the like of round or rectangular crosssection, the fans being responsible for the useful effects of an axial fan-motion of the air or other gas straight through the fan and a simple system for fixing the fan in position.

They do however furthermore give the useful effects of a radial fan---a high pressure and generally quiet operation. For these reasons they are widely used for a great number of different purposes. Fixing such a fan in position is about as simple as fixing a piece ducting or pipe in position. In this respect the air outlet of the fan is turned in the same direction as the air inlet, that is to say generally axially.

However known designs of fans of the sort in question have the shortcoming that the air comes out of the impeller with a high degree of spin so that the volumetric flow makes its way helically even in the downstream duct running from the fan, this being responsible for great losses in energy; a large part of the energy given by the impeller to the flow is not able to be used so that such fans have a representatively low efficiency. One purpose of the invention is that of taking care of this shortcoming.

Put somewhat differently, a purpose of the invention is that of designing a fan unit of the sort in question which, while still having the useful effects of the system noted, puts an end to the undesired effects by making certain that the flow coming from the fan impeller in the downstream duct does not have any spin so that at the outlet side of the fan there is generally speaking a regular, lined-up or parallel flow and the losses of energy noted are unlikely.

In the present invention a fan unit designed for use in a duct system and having a freely turning radial impeller without a spiral casing and a driving motor for the impeller is characterized by a guiding structure placed downstream from an outlet side of the impeller, said guiding structure being designed for turning the direction of the flow coming from the impeller in an axial direction. It is best for the guiding structure to be placed round the outside of the radial impeller and it may be spaced from the outer edge thereof.More specially, the guiding structure may have the form of a wheel, fixed in position, with a number of guide blades, as for example 1 5 to 1 8 or more specially 1 7 such guide blades, which are at such an angle that the inlet angle is the same as the outlet direction of the flow coming from the impeller so that the flow may make its way into the guiding structure gener ally smoothly. A useful effect is to be pro duced in this respect if the guide blades of the guiding structure are placed at such an angle, or have such a curved form, that the flow is changed in direction from the radial direction into the axial direction.The outcome is a fan unit which not only has the uefui properties as produced in the prior art noted but further more is free of the energy losses of known systems which are otherwise generally like the invention because the flow, after coming out of the impeller, is so changed in direction by the guiding structure that it may make its way along axially without any spin and so that the energy losses caused by the spin no longer take place. By designing and placing the blade in the way claimed in the dependent claims the properties of the fan are made even better in connection with cutting down losses.

of energy. With the further measure as claimed in the dependent claim to the effect that the guiding blades are able to undergo adjustment and change in angle together it is possible to make certain of the best possible later adjustment and control of the volumetric flow in small steps and simply without much time being needed for doing this.

Preferably the radial impeller, its driving motor and the guiding structure are put to gether as a single unit which itself may be placed in one piece in the duct or ducting or the like, the guide blades being best placed within a cylindrical casing, which at the same time gakes the form of a housing for the fan unit and keeps the unit together. In this respect the driving motor, which may for example be placed at the side of the impeller opposite to the inlet, may be fixed in position by way of radial support rods fixed at their outer ends to the cylindrical casing, or it may be fixed in position using angled support rods, of which one leg is axial, and which have fixed at their free ends a support ring (on the inlet side) used as well for supporting the impeller, while the other leg of the support rods is radial and is used for supporting the driving motor.By using the measures named here on the one hand the structure is made as simple as possible while on the other hand it is made lower in price so that fixing the fan unit in position later is made much more readily possible and simpler.

Working examples of the invention are to be seen in the accompanying figures.

Figure 1 is a partly cut away, diagrammatic view of a system of the present invention.

Figure 2 is a plan view of the system of Fig.

1.

Figure 3 is a part-development of the impel lers of Figs. 1 and 2 on a greater scale.

Figure 4 is a view of a further working example of the invention, again in a part side view and partly cut away.

Figure 5 is a plan view of the system of Fig.

4.

Figure 6 is a sideview of the guiding structure of a further working example of the invention.

Figure 7 is a plan view of the system of Fig.

6.

Figure 8 is a view of a blade of the guiding structure of Fig. 6 as seen from the front and diagrammatically.

The fan unit of the invention may be seen to be made out of freely running radial impeller 1 without a spiral housing and a driving motor 2 for the impeller, such driving motor best being an external rotor motor with a speed controller so that the speed may be changed, if for example the air flow rate is to be changed to be in line with changing needs, for example for cutting down the power need.

In the invention the flow direction is marked by arrows 3a and 3b and downstream from the impeller outlet 4 there is a guiding structure 5 for turning the flow, coming from the impeller as marked by arrows 6a, in the axial direction as marked by arrows 6b till the flow is able to make its way out of the system as marked by arrows 3b. The reader will see that in the working example of Fig. 1 the guiding structure 5, which is in the form of a fixed wheel with a number of blades 7, is placed round the outside of the radial impeller 1, there being a space between the outer edge of the radial impeller and the guiding structure 5.

As noted earlier, the guiding structure is made up of a number of guide blades, for example 1 5 to 18 and more specially 1 7 blades, and these blades are so positioned that the inlet angle is equal to the outlet angle or direction of the flow from the impeller so that the flow is able to make its way generally smoothly into the guiding structure.

The guide blades of the guiding structure may be designed and placed in a number of different ways, and for example the guide blades 10 of the guiding structure 11 of the system of Fig. 6 may (see Fig. 7) be placed at such an angle to the lengthways axis 1 2 and undergo such adjustment that the flow is guided out of the radial direction into the axial direction. In this respect, for example, the guide blades of the guiding structure may be placed at an angle a of 7 to 15 and more specifically 10, to the impeller axis 1 2. This may be seen as well from Fig. 3 in which the direction of turning of the impeller is marked 1 3 and the change in direction of the flow is as marked by arrow 14 into the axial direction.It is furthermore possible for the guide blades of the guiding structure to have such a curved form that the flow is changed from the radial direction into the axial direction. Furthermore the guide blades may have a circular outline or they may have a curved form which is not circular, the different possible forms of blades helping on the one hand to cut down energy losses and losses caused by impact or changes in direction, and on the other hand to make certain of the best possible and most efficient change in direction of the flow after. 1' coming from the impeller and before it makes its way into the part of the duct or the like placed downstream from the fan unit.It will C be seen from Figs. 7 and 8 that it is possible, again with the purpose of getting the evenest and smoothest flow, to make the length of the blades 1 about five times greater than the radius of curvature r, while the blade height h is about two to three times greater than the blade breadth b. In this case the blades are marked 10.

For making possible the best and simplest driving system, the guide blades may be so supported that they may be changed in angle and undergo adjustment all together or in common so that later adjustment is optimum and adjustment of the volumetric flow is possible in small steps, the system for doing this being simple and low in price.

For more specially making it simpler for the units to be put together and to make certain of a simple design, it is furthermore possible as part of the invention for the radial impeller, its driving motor and the guiding structure to be so made up into a unit that it may be placed in the duct or the like, for which purpose known flanges or reduction pieces or bridge pieces, plugin connections or the like may be used. In the working example of Figs.

1 to 3 the blades are placed within an outer cylindrical casing 15 which at the same time is used as the housing of the fan unit, it keeping all parts of the unit together. In this case the driving motor 2 is placed on the side of the impeller opposite to the inlet 16 into the impeller 1 and it is supported in this position by radial support rods 17, whose outer ends are fixed to the cylindrical housing at 18. It may be seen that the guiding structure and the impeller are placed within the housing, on which the motor is supported.

Using parts, of which no details are given here, the housing may be fixed in a ducting system. In the design of Figs. 4 and 5 the driving motor 20 is again placed on the side, opposite to the inlet 21 into the impeller 22, of the last-named, it being kept in position by angled support rods 23, of which each has a part 24 running axially while their free ends are fixed at 25 to a support ring 26, which is best designed for supporting the impeller 2:t as well, while the other part 27 is radial (paNts 24 and 27 are joined together at 28) and ist used for supporting the driving motor. The * guiding structure is numbered 29 and a sup port plate for the driving motor is numbered 30. In this case as well, in which the fan unit 22 has backwardly curved blades, there-is a housing 31, which is placed the unit and may at the same time be used for handling, putting in position and fixing the unit.

Claims

1. A fan unit designed for use in a duct system, said fan unit comprising a freely turning radial impeller without a spiral casing, a driving motor for the impeller, and a guiding structure placed downstream from an outlet side of the impeller, said guiding structure being designed for changing the direction of the flow coming from the impeller into an axial direction.

2. A fan unit as claimed in claim 1, wherein the guiding structure is placed round the radial impeller.

3. A fan unit as claimed in claim 1, wherein the guiding structure has the form of a wheel, fixed in position, and having a plurality of blades.

4. A fan unit as claimed in any of claims 1 to 3, wherein the guiding structure comprises a plurality of guide blades which are placed at such an angle that the inlet angle for the flow thereinto is the same as the outlet angle or direction of the flow from the impeller so that the flow will make its way generally smoothly into the guiding structure and is changed over from a radial direction into an axial direction.

5. A fan unit as claimed in claim 3 or 4, wherein the guiding structure has between 1 5 and 1 8 blades.

6. A fan unit as claimed in claim 5, wherein the guiding structure has 1 7 blades.

7. A fan unit as claimed in any of claims 3 to 6, wherein the guide blades of the guiding structure are at an angle of between 7 and 15, to the impeller axis.

8. A fan unit as claimed in claim 7, wherein the guide blades are at an angle of 10, to the impeller axis.

9. A fan unit as claimed in any of claims 3 to 8, wherein said guide blades of said guide structure have a curved form.

10. A fan unit as claimed in claim 9, wherein the guide blades of the guiding structure have a circularly curved outline.

11. A fan unit as claimed in claim 9 or 10, wherein the length of the blades is about 5 to 6 times the size of the radius of curvature.

1 2. A fan unit as claimed in any one of claims 3 to 11, wherein the blade height is about 2 to 3 times the blade breadth.

1 3. A fan unit as claimed in any one of claims 3 to 12, wherein means are provided for changing the angle and for adjustment of the guide blades.

1 4. A fan unit as claimed in any one of claims 3 to 13, wherein a cylindrical housing is located round the guide blades, the cylindrical housing also housing the fan unit and keeping the unit together, the drive motor being placed on the side of the impeller which is opposite to the inlet thereto.

1 5. A fan unit as claimed in claim 14, wherein support rods support the driving motor, outer ends of the support rods being fixed to the cylindrical housing.

1 6. A fan unit as claimed in claim 15, wherein angled support rods support the driving motor, each support rod having an axially extending part, and the rods at their free ends mounting a support ring on the inlet side, other parts of the angled support rods being radial and being used for supporting the driving motor.

1 7. A fan unit as claimed in claim 16, wherein the driving motor is supported by the support ring.

18. A fan unit as claimed in any one of the preceding claims, wherein the radial impeller, the driving motor and the guiding structure are put together as a single unit which may be placed in a duct.

1 9. A fan unit substantially as hereinbefore described with reference to Figs. 1 to 3 of the accompanying drawings.

20. A fan unit substantially as hereinbefore described with reference to Figs. 4 and 5 of the accompanying drawings.

21. A fan unit substantially as hereinbefore described with reference to Figs. 6 to 8 of the accompanying drawings.

22. Any novel subject matter or combination including novel subject matter herein disclosed, whether or not within the scope of or relating to the same invention as any of the preceding claims.