GB2063365A

GB2063365A - Radial Flow Fans

Info

Publication number: GB2063365A
Application number: GB8028918A
Authority: GB
Original assignee: Punker GmbH
Current assignee: Punker GmbH
Priority date: 1979-10-08
Filing date: 1980-09-08
Publication date: 1981-06-03
Also published as: SE448018C; GB2063365B; SE448018B; FR2467309A1; DK148008B; DE2940773C2; SE8006990L; DK425880A; FR2467309B1; DK148008C; DE2940773A1

Abstract

A high-power radial flow ventilator comprises a bladed impeller 21 which is shielded at the side adjacent an inlet nozzle 11 by a shroud ring 10. The ring 10 overlaps the inlet nozzle 11 with an annular clearance "S". The curve which determines the shape of the ring and which is arcuate, parabolic or hyperbolic, is described with a radius R, or with several radii, the ratio of which to the smallest diameter (do) of the ring (inlet diameter), is 0.21- 0.30, and is preferably 0.225-0.280 to 1. <IMAGE>

Description

SPECIFICATION High-Power Radial Ventilator The present invention relates to a high-power radial ventilator which has a coiled housing with a lateral inlet nozzle and a suitable impeller, or a wall at the suction side with lateral inlet nozzle and freely outblowing impeller. The impeller of the ventilator has blades1 especially standard, non-streamlined blades, for example arcuate blades, and is shielded at the side turned towards the inlet nozzle by a protecting ring curving inwardly and forwardly, said ring at its admission end, whereat is its smallest diameter "d,", overlapping the adjacent end of the inlet nozzle and masking same in the outwards direction, leaving free an annular clearance of width "S".

Such a ventilator is referred to hereinafter and in the claims as a high-powered radial ventilator of the kind stated.

Radial ventilators of the kind stated are known, which have an impeller, a coiled housing and an inlet nozzle, and in which a clearance is left between the inlet nozzle and the ring shielding of the impeller. A disadvantage of these known radial ventilators is that they have a relatively low power density.By "power density" is meant the product "Sgopt xit'' in which "opt" is the output figure at the point "flopt" and "rSt" is the pressure value for the dopt (total pressure) at Qopr An object of the present invention is to obviate or mitigate the aforesaid disadvantage and to provide a radial ventilator of the kind stated in which, with approximately the same pressure coefficient t and approximately as high a degree of efficiency as for hitherto-known radial ventilators of the kind stated, a greater power density is achieved.

In accordance with the present invention, we provide a high-power radial ventilator of the kind stated in which the curve which determines the shape bf the protecting ring and which is arcuate, parabolic or hyperbolic, is described with a radius, or with several radii, the ratio of which to the smallest diameter at the inlet area of the protating ring (inlet diameter) is 0.21-0.30 to 1.

Preferably, the ratio of the radius or radii to the smallest diameter at the inlet area of the protecting ring (inlet diameter) is 0.225-0.280 to 1. Preferabiy, the arrangement is such that the ratio of the smallest diameter of the intake area of the protecting ring (inlet diameter) to the clearance width is 1 to 0.01 0--0.020.

The ratio of the blade-internal diameter to the effective diameter may, for example, be 0.54- 0.80 to 1 , whilst the ratio of the distance (bo) measured in the direction of the impeller axis, between the nave disc and the plane passing through the center of curvature of the protecting ring, to the smallest diameter (do) at the intake end of the protecting ring (inlet diameter), is preferably 0.52-0.70 to 1. It may'also be arranged, for example, that the ratio of the effective diameter (d2) at the trailing edge of the blade to the blade-width (b2) is 1 to 0.25--0.40, preferably 1 to 0.27-0.38.It is also possible to arrange, for example, that the plane which is parallel to the nave disc plane and passes through the centre of curvature of the protecting ring forms an angle of 10o30o with the radius originating at this centre of curvature and directed to the extreme end point of the blade at the protecting ring side (beginning of blade).

As a result of the invention, with approximately the same Vt and Qopt values, an optimum power density is achieved through a considerably greater (Popt (which is what the invention set out to accomplish), for which a much better C, distribution then is attainable with known means is a prerequisite. The point of departure of the conception was that these aims are most conveniently achieved, firstly by selecting a shallow curvature for the protecting ring and, secondly, by providing a relatively large clearance, which results in a much more energetic flow.

Large clearance widths and shallow curvature produce low deflection losses at the protecting ring and also even lower shock losses at the blade suction sides close the protecting ring and consequently a more even Cr distribution, which signifies a high and optimum conversion of energy in impellers of high power density.

Heretofore, attempts to achieve higher power densities have failed in that it was impossible to obtain greater output figures because the deflection problem could not be neatly solved if the intention was to achieve greater output volumes at all costs. This has now been achieved by an improvement in C, distribution, which led to a higher Qopv A further advantage of the inventive conception and of the resulting relationship proposed by the invention between the intake diameter and the blade-internal diameter results from a production engineering improvement, because inwardly-directed blades can be fitted into slots by their inner edge at a welding or assembly point, that is to say, they can be accurately positioned, and this core can also remain in the impeller even during fitting of the hub ring.This ensures that the centring of the hub ring remains unaltered during the securing of the blades (by welding, riveting, etc.), so that the impeller body then requires no corrective adjustment at all, or very much less adjustment.

The correct selection of the ratio between the diameters also offers the possibility of employing a lesser, optimum number of blades, which is reflected in a reduction in manufacturing costs and in simplification of manufacture. The earlier controlling of the suction flow by the blade cascade, due to the ratio proposed in the invention between the intake diameter and the blade-internal diameter also offers advantages in inflow technique. Finally, it should be noted that the noise level of the new radial ventilator is extremely favourable.

Merely as a matter of form, mention should be made of the fact that the value "S" is a constructional dimension which, in actual practice, involves certain defects of manufacture, e.g. centring of the intake nozzle to the impeller, rotational faults in the impeller, etc. The value is therefore an average one arrived at from the real measured values of a ventilator.

Further advantages and important features of the invention will appear in the following description which refers to the accompanying drawings.

In the drawings, which illustrate certain exemplary embodiments of the invention: Fig. 1 shows the C, distribution over the outer width of the blade in relation to the gap width in an arrangement according to the invention, in diagrammatic form; Fig. 2 shows a first specific embodiment of the invention in side elevation; Fig. 3 is a front elevation view of the arrangement of Fig. 2; Figs. 4, 5 and 6 illustrate three further specific embodiments of the invention, in like manner to Fig. 2; Fig. 7 illustrates another specific embodiment of the invention, in front elevation and diagrammatically; Fig. 8 is a side elevation of the arrangement of Fig. 7, partly in section; Fig. 9 illustrates a detail of yet another specific embodiment of the invention, on a larger scale, and in section in like manner to Figs. 4, 5 and 6; and Fig. 10 is a nondimensional graph of the improvement achieved by the invention in relation to the state of the art.

The high-power radial ventilator of the kind stated according to the invention (with reference, for example, to Figs. 7 and 8) comprises, for example, a coiled housing 1 with a lateral inlet nozzle 2 and an impeller 3 with blades 4. The blades may or may not be streamlined, and, if not streamlined they may be of arcuately curved form; however they may have a parabolic curve, or may even be straight. At the side turned towards the inlet nozzle, the impeller 3 is shielded by a protecting ring 5 curving inwardly and forwardly, said ring 5 at its admission end, whereat is its smallest diameter "d0,,1overiapping the adjacent end of the inlet nozzle 2 and masking same in the outwards direction, leaving free an annular clearance of width "S".

In Fig. 2 there is provided, between the protecting ring 10 and the inlet nozzle 1 a clearance "S", the curve having an arcuate shape determining the shape of the protecting ring being described with a radius of curvature which is in the ratio 0.225-0.280 to 1 to the smallest diameter "d," at the inlet end of the protecting ring (inlet diameter), whilst this smallest diameter at the inlet area of the protecting ring (inlet diameter) is in the ratio 1 to 0.014.02 to the clearance "S".The curve of the protecting ring may be arcuate, as in the specific embodiment illustrated; however, it may also be parabolic or hyperbolic, or, finally, it may be described with a radius, or from several parts with several radii, the ratio between the radius "R" and the inlet diameter "d," generally being 0.21-0.30 to 1.

The inlet diameter "d,", for its part, in relation to the internal diameter "d," at the blades, i.e. to the diameter of the circle described about the impeller axis and containing the inner edges of the blades, is in the ratio 0.97-1.06 to 1 and preferably 1.01-1.06 to 1. The ratio of the internal diameter "d" at the blades to the effective diameter "d2" is 0.540.80 to 1; in the Fig. 2 embodiment, specifically 0.77 to 1. The ratio of the effective diameter "d2" to the bladewidth "b2" at the trailing edge of the blade in the Fig. 2 embodiment is specifically 1 to 0.36, the advantageous range in this case being as a whole between 1 and 0.25--0.40 and preferably between 1 and 0.27-0.38.With this, it will be gathered from Fig. 2 that the ratio of the distance "b," (measured in the direction of the impeller axis, indicated by arrow 12) between the nave disc 13 and the plane passing at 14 through the centre of curvature of the protecting ring 10, to the smallest diameter do at the inlet end of the protecting ring (inlet diameter), is 0.52--0.70 to 1.

In Fig. 10 of the drawings, the improvement achieved by the invention relative to the state of the art with regard to the curve of Vt and lit over Q is shown in nondimensional form.

In the Fig. 4 embodiment, the plane 1 6 parallel to the plane of the nave disc 15 and passing through both the centre of curvature 1 7 and the extremity 1 8 of the protecting ring, forms an angle p of 100--300 with the radius originating at the centre of curvature 1 7 to the extreme end point 19 of the blade 20 at the protecting ring side (beginning of blade).

In the Fig. 4 embodiment, with an angle y of 1 2o1 60 between the tangent 22 to the protecting ring 23 at its external edge and the plane of the nave disc 15 (or a plane parallel thereto), the ratio of the blade-internal diameter "d1" to the effective diameter "d2" is 0.68-0.72 to 1, the ratio of the effective diameter "d2" to the blade-width "b2" at the trailing edge of the blade being 1 to 0.20-0.35.In the Fig. 5 embodiment, with an angle y of 12 16 between the tangent 25 to the protecting ring 26 at its external edge and the plane 28 parallel to the plane of the nave disc 27, the ratio of the bladeinternal diameter "d1" to the blade-effective diameter "d2" is 0.61-0.64 to 1, whilst the ratio of the blade-effective diameter "d2" to the bladewidth "b2" at the trailing edge of the blade is 1 to 0.1 6--0.30.

In the case of a further exemplary embodiment of the high-power radial ventilator of the kind stated according to the invention, which is not illustrated in the drawings, with an angle y of 1 2o1 60 between the tangent to the protecting ring at its external edge and the plane of the nave disc, the ratio of the blade-internal diameter "d1" to the effective diameter "d2" is 0.540.57 to 1, whilst the ratio of the blade-effective diameter "d2,,to the blade-width "b2" at the trailing edge of the blade is 1 to 0.12-0.25.

A further embodiment of the invention is illustrated in Fig. 6. In this case, the outer bladesupporting marginal area of the nave disc 30 is bent aside, in the direction away from the protecting ring 31 through an angle S, as shown at 32, which lies between 100 and 250, whilst the angle y between the tangent 33 to the protecting ring 31 at its external edge and the plane 34 of the nave disc 30, or a plane parallel thereto, lies between 200 and 300. In this case, the depth "b" of the blade decreases from the nave disc 30-32 to the projecting ring 31 in the ratio of 1 to 0.7-0.8, whilst the ratio of the mean blade-internal diameter "dim" to the mean effective diameter "d2m" is 0.800.95 to 1.The ratio of the mean blade width "b2m" at the trailing edge of the blade to the mean effective diameter "d2m" is 0.35-0.50 to 1. Finally, in this embodiment, the arrangement is also such that the ratio of the maximum outside diameter "d2" in the region in which the blade trailing edge 35 comes together with the outlet-side region of the protecting ring 31, i.e. in the region of the point 36, to the mean blade-effective diameter "d2m" is 1 to 0.85-0.95.

It is to be understood that, through theoptimization hereinbefore described of inlet nozzle, clearance geometry and impeller protecting ring curvature, a radial velocity component Cr, which is distributed as uniformly as possible and is as large as possible, is obtained along the leading edges of the blades, this leading finally to improved loading of the blade over its width and, consequently, to a high power density.

With a steeply curved protecting ring and high volume coefficient, the flow would be turbulent along the protecting ring contour, on account of which a displacement of the economic load point Qopt to greater Q values would be impossible, even with appropriate increase of the blade-entering angle 1 With a shallow curvature of the protecting ring and narrow clearance, it might be possible to obtain an acceptable flow along the protecting ring, but the C, distribution and also the value of this radial velocity component are nevertheless always highly irregular.Only through the gently-curved protecting ring according to the invention, in association with a larger clearance, which brings about a more energetic flow, is it possible to obtain an increase not only in the pressure coefficient t but also in the efficiency lit and an improved Cr distribution. Large clearances bring about not only low deflection losses at the impeller protecting ring but, in addition, lower shock losses at the blade suction sides close to the protecting ring and consequently a more even C, distribution. A high and optimum conversion of energy in impellers of high power density is made possible only through impeller protecting rings of shallow curvature together with large clearance.

This is illustrated in Fig. 1 in which the Cr distribution is shown for two clearance widths S and S2 over the impeller width, along with a specific "d1,,.

In Fias. 7 and 8 an embodiment of the invention is shown in complete detail. It will be seen therefrom that the casing has the form of a logarithmic spiral with a pitch related to the base circle 40, which is at most between 7.50 and 8.50. The relationship between the base circle 40 and both the inlet diameter 41 and the width 42 of the casing is important. The relationship between the diameters 40 and 41 has already been fully dealt with hereinbefore. The ratio of the diameter 41 to the width of the casing is 1 to 0.8-1.25. The position of the baffle 45 is also important, the angle 46 which the tangent to the baffle, which passes through the impeller axis 47, subtends with the normal 48, being between 200 and 350.Also important are: the angle p at which the nozzle surface extends in relation to the impeller axis 47, the so-called exit cone angle, which in the present case is preferably 300 to 400; the clearance "e" between the nave disc 50 and the pertaining wall 51 of the casing and the ratio thereof to the diameter 40 which is 0.07 max. to 1; and finally, the length "u" of the clearance in relation to the clearance width "S" as shown for example in Fig. 9; in Fig. 9, the nozzle is shown at 51, the protecting ring at 52, and 53 denotes part of the casing. The inlet nozzle is flared at the throat thereof in order to deflect the flow at the wall in the gap itself tangentially to the protecting ring contour, as is clearly shown at 55 in Fig. 9. The ratio s:u is 0.15 to 0.5.

In the exemplary embodiments illustrated in the drawings, the impeller has eight to eighteen blades. The exact number of blades is governed of course by the respective blade-intake and bladeemergence angles, for example with a bladeintake angle p1 of 1 50 and a blade-emergence angle P, df 360, a maximum number of twelve blades may be selected; with a blade-intake angle p, of 180 and a blade-emergence angle p2 of 460, the maximum number of blades may be taken to be fourteen or fifteen.

Claims

1. A high-power radial ventilator of the kind stated in which the curve which determines the shape of the protecting ring and which is arcuate, parabolic or hyperbolic, is described with a radius, or with several radii, the ratio of which to the smallest diameter at the inlet area of the protecting ring (inlet diameter) is 0.21-0.30 to 1.

2. A high-power radial ventilator of the kind stated as claimed in claim 1 in which the ratio of the radius or radii to the smallest diameter at the inlet area of the protecting ring (inlet-diameter) is 0.225-0.280 to 1.

3. A high-power radial ventilator of the kind stated as claimed in claim 1 or 2, in which the ratio of the smallest diameter of the intake area of the protecting ring (intake diameter) to the clearance width is 1 to 0.10--0.020.

4. A high-power radial ventilator of the kind stated as claimed in any one of claims 1 to 3, in which the ratio of the inlet diameter to the internal diameter at the blades, i.e. to the diameter of the circle described about the impeller axis and containing the inner edges of the blades, is 0.97-1.06 to 1.

5. A high-power radial ventilator of the kind stated as claimed in any one of claims 1 to 3, in which the ratio of the inlet diameter to the internal diameter at the blades, i.e. to the diameter of the circle described about the impeller axis and containing the inner edges of the blades, is 1.01-1.06 to 1.

6. A highpower radial ventilator of the kind stated according to any one of the preceding claims, in which the plane which is parallel to the nave disc plane and passes through the centre of curvature of the protecting ring forms an angle of 100--300 with the radius originating at this centre of curvature and directed to the extreme end point of the blade at the protecting ring side (beginning of blade).

7. A high-power radial ventilator of the kind stated according to any one of the preceding claims, in which the ratio of the blade-internal diameter to the effective diameter is 0.54 ".80 to 1.

8. A high-power radial ventilator according to any one of the preceding claims, in which the ratio of the distance, measured in the direction of the impeller axis, between the nave disc and the plane passing through the centre of curvature of the protecting ring to the smallest diameter (do) at the intake end of the protecting ring (inlet diameter), is 0.52--0.70 to 1.

9. A high-power radial ventilator of the kind s+.ated according to any one of the preceding claims in which the ratio of the effective diameter to the blade-width at the trailing edge of the blade is 1 to 0.250.40.

10. A high-power radial ventilator of the kind stated according to any one of claims 1 to 8, in which the ratio of the effective diameter to the blade-width at the trailing edge of the blade is 1 to 0.27-0.38.

11. A high-power radial ventilator of the kind stated according to any one of claims 1 to 6, in which, with an angle of 120--160 between the tangent to the protecting ring at its external edge and the plane of the nave disc, the ratio of the blade-internal diameter to the effective diameter is 0.68-0.72 to 1, whilst the ratio of the effective diameter to the blade-width at the trailing edge of the blade is 1 to 0.20--0.35.

12. A high-power radial ventilator of the kind stated according to any one of claims 1 to 6, in which with an angle of 120--160 between the tangent to the protecting ring at its external edge and the plane of the nave disc, the ratio of the blade-internal diameter to the effective diameter is 0.61-0.64 to 1, whilst the ratio of the effective diameter to the blade-width at the trailing edge of the blade is 1 to 0.16-0.30.

13. A high-power radial ventilator of the kind stated according to any one of claims 1 to 4, in which, with an angle of 120--160 between the tangent to the protecting ring at its external edge and the plane of the nave disc, the ratio of the blade-internal diameter to the effective diameter is 0.54--0.57 to 1, whilst the ratio of the effective diameter to the blade-width at the trailing edge of the blade is 1 to 0.1 2--0.25.

14. A high-power radial ventilator of the kind stated according to claim 1,2 or 3, in which the outer blade-supporting marginal area of the nave disc is bent aside in the direction away from the protecting ring through an angle which lies between 100 and 250, and the angle between the tangent to the protecting ring at its external edge and the plane of the nave disc lies between 200 and 300, the depth of the blade decreasing from the nave disc to the protecting ring in the ratio of 1 to 0.7-0.8.

15. A high-power radial ventilator of the kind stated according to claim 14, in which the ratio of the mean blade-internal diameter to thq mean effective diameter is 0.80--0.95 to 1 , and the ratio of the mean blade-width at the trailing of the blade to the mean effective diameter is 0.35- 0.50 to 1.

16. A high-power radial ventilator of the kind stated according to claim 14 or 15, in which the ratio of the maximum outside diameter in the region in which the blade-trailing edge comes together with the outletside region of the inlet nozzle, to the mean blade-effective diameter is 1 to 0.85-0.95.

1 7. A high-power radial ventilator of the kind stated according to any one of the preceding claims, in which the inlet nozzle is flared at the throat thereof in order to deflect the flow at the wall in the gap itself tangentially to the protecting ring contour.

1 8. A high-power radial ventilator of the kind stated, substantially as hereinbefore described with reference to Figs. 2 and 3 of the accompanying drawings.

19. A high-power radial ventilator of the kind stated, substantially as hereinbefore described with reference to Fig, 4 of the accompanying drawings.

20. A high-power radial ventilator of the kind stated, substantially as hereinbefore described with reference to Fig. 5 of the accompanying drawings.

21. A high-power radial ventilator of the kind stated, substantially as hereinbefore described with reference to Fig. 6 of the accompanying drawings.

22. A high-power radial ventilator of the kind stated, substantially as hereinbefore described with reference to Fig. 7 and 8 of the accompanying drawings.

23. A high-power radial ventilator of the kind stated, substantially as hereinbefore described with reference to Fig. 9 of the accompanying drawings.