Centrifugal Or Diagonal Impeller With Modified Blade Edge

Abstract

A centrifugal or diagonal impeller has impeller blades (4) that are curved in the circumferential direction about an axis of rotation and are formed from a single-layer sheet metal. Each blade (4) has a suction side (11) and a pressure side (12) as well as a blade leading edge (5) and a blade trailing edge (6). At least the blade leading edge (5) of the impeller blades (4) adjacent to their suction side (11) have a geometric edge modification in the form of a rounding (7) over a predetermined partial length of a blade thickness (SD) of the impeller blades (4).

Claims

1. A centrifugal or diagonal impeller comprising: impeller blades curved in the circumferential direction about an axis of rotation and formed from a single-layer sheet metal; each blade has a suction side, a pressure side as well as a blade leading edge and a blade trailing edge; and at least the blade leading edge of the impeller blades adjacent to their suction side has a geometric edge modification in the form of a rounding that is limited over a predetermined partial length of a blade thickness of the impeller blades.

2. The centrifugal or diagonal impeller as set forth in claim 1, where the blade leading edge of the impeller blades adjacent to their pressure side is formed without the edge modification and has a beveled shape.

3. The centrifugal or diagonal impeller as set forth in claim 1, where the blade trailing edge of the impeller blades adjacent to the pressure side has a geometric edge modification in the form of a rounding over a predetermined partial length of the blade thickness.

4. The radial or diagonal impeller as set forth in claim 1, where the impeller blades have a constant blade thickness.

5. The radial or diagonal impeller as set forth in claim 1, wherein the rounding has a constant radius.

6. The centrifugal or diagonal impeller as set forth in claim 1, wherein the rounding is formed by a plurality of radii.

7. The centrifugal or diagonal impeller as set forth in claim 1, wherein the rounding is elliptical.

8. The centrifugal or diagonal impeller as set forth in claim 1, wherein the rounding is formed by a bevel.

9. The centrifugal or diagonal impeller as set forth in claim 1, wherein the blade leading edge and the blade trailing edge have an initial shape by edge trimming, and the initial shape includes the edge modification through a forming process.

10. The centrifugal or diagonal impeller as set forth in claim 1, wherein the edge modification along the blade leading edge on the suction side, starting from an outermost edge of the blade leading edge in the direction of the pressure side of the blade leading edge, extends as a partial length over at least 20% of the blade thickness.

11. The centrifugal or diagonal impeller as set forth in claim 2, wherein the edge modification along the blade trailing edge on the pressure side starting from an outermost edge of the blade trailing edge in the direction of the suction side of the blade trailing edge extends as a partial length over at least 20% of the blade thickness.

12. The centrifugal or diagonal impeller as set forth in claim 1, where the impeller blades are three-dimensionally curved between the blade leading edge and the blade trailing edge by a forming process.

13. The centrifugal or diagonal impeller as set forth in claim 1, wherein a bottom disc and a cover disc are connected by the impeller blades.

14. The centrifugal or diagonal impeller as set forth in claim 13, wherein the cover disc is undulated and/or rotationally symmetrical in the circumferential direction.

Description

DRAWINGS

[0022] Other advantageous refinements of the disclosure are disclosed in the in the subclaims and/or depicted in greater detail below together with the description of the preferred embodiment of the disclosure with reference to the figures. In the drawing:

[0023] FIG. 1 is a perspective view of a centrifugal impeller;

[0024] FIG. 2 is a section view through the centrifugal impeller of FIG. 1;

[0025] FIG. 3a is a detailed cross-section view of a blade leading edge of the centrifugal impeller of FIGS. 1 and 2 (detail A);

[0026] FIG. 3b is a detailed cross-section view of a blade trailing edge of the centrifugal impeller of FIGS. 1 and 2 (detail B);

[0027] FIG. 4a is a detailed cross-section view of the blade leading edge of the centrifugal impeller in an alternative embodiment (detail C);

[0028] FIG. 4b is a detailed cross-section view of the blade trailing edge of the centrifugal impeller in an alternative embodiment (detail D);

[0029] FIG. 5a is a detailed cross-section view of the blade leading edge of the centrifugal impeller in another alternative embodiment (detail E);

[0030] FIG. 5b is a detailed cross-section view of the blade trailing edge of the centrifugal impeller in another alternative embodiment (detail F); and

[0031] FIG. 6 is a diagram of the qualitative increase in efficiency.

DETAILED DESCRIPTION

[0032] The disclosure is explained in more detail in the following by using a preferred exemplary embodiment with reference to FIG. 1.

[0033] FIG. 1 shows an exemplary centrifugal impeller 1. However, the disclosure can also be applied directly to diagonal impellers where the outflow direction is not radial, but diagonal. The centrifugal impeller 1 includes a bottom disc 2, a rotationally symmetrical cover disc 3, and impeller blades 4 that extend therebetween and are arranged around the axis of rotation. The cover disc 3 forms the axially centered intake opening. The centrifugal impeller 1 is made of sheet metal, with the impeller blades 4 being connected, particularly welded, to the bottom disc 2 and the cover disc 3.

[0034] The impeller blades 4 are made from a single-layer sheet metal with a constant material thickness and blade thickness SD. On the one hand, the blades 4 are curved backward against the intended direction of rotation of the centrifugal impeller 1, when used as intended. On the other hand, the blades 4 are curved three-dimensionally by a forming process, as can clearly be seen not only in FIG. 1 but also in the axial section of FIG. 2.

[0035] In the embodiment shown, each of the impeller blades 4 is identical in shape. Each includes a respective suction side 11 and pressure side 12, as well as a blade leading edge 5 on the suction side and a blade trailing edge 6 on the outlet side.

[0036] With reference to the detailed view according to FIG. 3a, the suction-side blade leading edges 5 of the impeller blades 4 have a geometric edge modification in the form of a rounding 7 with a continuous radius. In the embodiment shown, the edge modification, in the form of the rounding 7, extends over the entire axial length along the blade leading edge 5. It starts from an outermost edge of the blade leading edge 5 on the suction side 11 in the direction of the pressure side 12 over a partial length L. The length L corresponds to approximately 50% of the blade thickness SD. The beveled end 20 of the blade leading edge 5 on the pressure side 12 is sharp-edged and, in particular, forms a transition at right angles.

[0037] In the exemplary embodiment shown in FIGS. 1 and 2, the blade trailing edges 6 are also provided with the rounding 7. It starts from the pressure side 12 in the direction of the suction side 11 of the respective impeller blade 4, as shown in the detailed view of FIG. 3b. The beveled end 21 of the blade trailing edge 6 on the suction side 11 is also sharp-edged, as is the case with the blade leading edge 5, and particularly also forms a transition at right angles.

[0038] Alternative design variants of the edge modification in the form of a rounding 7 are shown in the exemplary embodiments of FIGS. 4a and 5a, for the blade leading edges 5, and in FIGS. 4b and 5b, for the blade trailing edges 6. In the exemplary embodiment according to FIGS. 4a, 4b, the edge modification is implemented in the form of a rounding 7 by a bevel. In the exemplary embodiment according to FIGS. 5a, 5b, the edge modification is implemented in the form of a rounding 7 in an elliptical shape that extends farther along the chord length of the impeller blades 4. The partial length L is then less than in the solution according to FIGS. 3a, 3b and is only approximately 20% of the blade thickness SD.

[0039] FIG. 6 shows a diagram comparing the efficiency of two identical centrifugal impellers. Dashed line A shows the characteristic curve of the centrifugal impeller with conventional blade leading edges. Line B shows the characteristic curve of the centrifugal impeller 1 with blade leading edges 6 with edge modification in the form of the rounding 7. The increase in efficiency due to the edge modification in the form of the rounding 7 is observed particularly with volume flows in the range of 1000-4000 m.sup.3/h and is significant in the range of 1500-3000 m.sup.3/h.

[0040] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.