This application claims the priority of German Utility model application Serial No 20 2005 004 180.7 filed Mar. 14, 2005, the subject-matter of which is incorporated herein by reference.
The invention concerns generally a radial fan.
A radial fan which can be considered as a typical configuration comprises a casing having a side portion and a pot-like casing portion, with an impeller wheel which is arranged in the casing and which has radially extending vanes or blades.
Such a fan for conveying gaseous media is generally used in items of equipment which involve a high flow resistance. That can involve for example a cylinder burner or a ceramic surface burner which are used in the most recent developments in gas boilers. Gas heating boilers of that kind may often involve a flow resistance of the order of magnitude of 800 Pascals and more. To ensure stable operating points, the endeavour is to produce pressure-volume characteristics which are as steep as possible, when employing a radial fan.
As an example of such a radial fan reference may be made to EP 0 410 271 A1 disclosing a unit for conveying a gaseous medium, in which the housing portion of the radial fan has a holder for an electric motor for driving the impeller wheel while the side portion is provided with an inlet opening for the feed flow of the fan air.
An object of the invention is to provide a radial fan which while affording an output which is as far as possible the same is particularly compact and inexpensive and simple to produce.
Another object of the present invention is to provide a radial fan which affords a rational structure and which can enjoy reduced pressure losses.
Yet another object of the present invention is to provide a radial fan so designed as to afford a satisfactory output without an increase in noise level.
In accordance with the principles of the present invention the foregoing and other objects are attained by a radial fan comprising a casing having a side portion and a pot-like casing portion. An impeller wheel is arranged therein and has radially extending blades. An electric motor is arranged at the side portion and a pressure chamber which is formed by the casing portion and the side portion, together with the impeller wheel space between the blades of the impeller wheel, forms in cross-section a nozzle in the manner of a venturi nozzle. The ratio of the greatest blade height denoted by H/greatest diameter denoted by D of the scroll or spiral of the radial fan is substantially between H/D=0.08 and H/D=0.3.
As will be seen from the description of a preferred embodiment of the radial fan as set forth in hereinafter, the particular configuration of the above-mentioned pressure chamber geometry and the design of the blades of the impeller wheel in relation to the diameter of the scroll of the pressure chamber provides that the desired output levels are excellently well achieved.
In accordance with a preferred feature the ratio of the greatest blade height to the greatest diameter of the scroll is 0.1, while in accordance with a still further preferred feature that ratio is 0.12. In a structural configuration of the radial fan that can correspond to a largest diameter of about 145.3 mm with a blade height of 18 mm.
In a further preferred feature of the invention provided in the casing portion and/or in the side portion are enlargement cavities or recess portions which continuously three-dimensionally enlarge the spiral-shaped pressure chamber.
In another preferred feature the enlargement cavity or recess portion in the casing portion is larger than that in the side portion. Such a choice in respect of the casing configuration and the arrangement of the larger enlargement cavity or recess portion in the casing portion affords the possible option of providing those recess portions on the side of the fan casing that is remote from the motor, thereby affording a configuration which is generally desired, without involving spatial limitation.
In a preferred feature the ratio of the height to the diameter of the casing can be between 1:7 and 1:9, that ratio in a particularly preferred feature being substantially 1:8.
It is further preferred if, at a rotary speed of n=5250, an air flow by volume of about 11 l/s is delivered at a pressure of 1050 Pascals. That corresponds to a shaft power of about 21 W. That is a very low value in comparison with previous radial fan design configurations.
A further advantageous configuration of the radial fan according to the invention provides that the plane of the connection to the delivery duct of the casing is at an angle α≦90° relative to the delivery direction, denoted by A hereinafter. It is particularly advantageous if the angle is between 90° and 83°, preferably being 86.4°.
A further advantageous configuration of the invention can provide that the delivery duct is afforded on the casing portion.
In another preferred feature the delivery duct can be of a configuration which enlarges trumpet-like.
In a further-preferred feature of the invention the casing can have a tongue portion which extends into the pressure chamber. In that case it is desirable for the tongue portion on the casing portion to be in the form of a ramp which rises in the flow direction on the side wall of the casing portion. The provision of a tongue portion in that way means that the pressure chamber is screened or shielded in relation to the impeller wheel in the delivery region so that pressure losses can be reduced in that fashion.
In a further preferable configuration of the invention it may be advantageous for the tongue portion to be provided on the side portion in the form of a ramp rising in the flow direction towards the casing portion. Providing the tongue portion in the form of the ramp in that way means that the gap between the impeller wheel and the side wall of the casing portion can be reduced without an increase in noise level.
In accordance with yet a further preferred feature of the invention the impeller wheel can include a hub and at least one cover disk, for example a front cover disk, in which case then the blades of the impeller wheel are only held to the hub and the cover disk. It is then possible to dispense with a rearward carrier disk. That configuration can involve inexpensive manufacture of the impeller wheel and thus the radial fan overall.
Further objects, features and advantages of the present invention will be apparent from the description hereinafter of a preferred embodiment thereof.
Referring firstly to
The casing 4 has a pressure chamber which is identified by reference 8 in
Looking now again at
Provided in the casing portion 3 and/or in the side portion 2 are enlargement cavities or recess portions indicated at 19 in
In the illustrated embodiment the enlargement portion 19 in the casing portion 3 is larger than in the side portion 2.
Reference will now be made to
The connection 12 of the delivery duct 13 is disposed in a plane indicated at 11 which in the illustrated embodiment forms an angle of α≦90° with the theoretical air discharge or delivery direction as indicated by the arrow A in
Reference will now be made to
As can be clearly seen from
In accordance with the invention the ratio of the greatest blade height indicated by H in
Attention is now directed to
In the embodiment illustrated in the accompanying Figures, as is diagrammatically shown most clearly in
It will be further appreciated that the above-described embodiment has been set forth solely by way of example and illustration of the principles of the invention and that various modifications and alterations may be made therein without thereby departing from the spirit and scope of the invention.
Number | Date | Country | Kind |
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20 2005 004 180 U | Mar 2005 | DE | national |
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