Radial or diagonal flow impeller with modified blade edges

Abstract

The present invention relates to a radial or mixed-flow impeller having impeller blades (4), which are bent in a circumferential direction about a rotation axis and are formed from a single layer of metal sheet, each of the metal sheets having a suction side (11) and a pressure side (12), as well as a blade leading edge (5) and a blade trailing edge (6), wherein at least the blade leading edge (5) of the impeller blade (4) adjacent to its suction side (11) has a geometric edge correction in the form of a rounding (7) over a predetermined partial length of the blade thickness (SD) of the impeller blade (4).

Description

Technical Field

[0001] The present invention relates to a radial or mixed-flow impeller for a fan, the impeller having impeller blades that are bent in a circumferential direction around a rotation axis and made of a metal sheet. Background Art

[0002] Radial or mixed-flow impellers made of various materials are known from the prior art. In particular, depending on the required place of use and purpose, partially fiber-reinforced plastics and metals in the form of metal sheets are used. Fan blades made of metal sheets are manufactured as hollow profile blades or with a constant material strength.

[0003] Bent fan blades made of metal sheets are generally made by a forming process and trimming of the raw material. This results in blunt blade ends on both the leading edge and the trailing edge of the blade, which respectively have two sharp edges at the ends of two opposite blade surfaces, and these edges determine the suction side and the pressure side of the corresponding impeller blade in terms of flow. Such impeller blades can be used directly in the impeller without post-treatment. Summary of the Invention

[0004] The object of the present invention is to provide a radial or mixed-flow impeller formed of a single-layer metal sheet having bent impeller blades, which has a higher efficiency compared to conventional impellers.

[0005] According to the present invention, there is provided a radial or mixed-flow impeller having impeller blades bent in a circumferential direction around a rotation axis. The impeller blades are formed of a single-layer metal sheet and each has a suction side and a pressure side, as well as a leading edge and a trailing edge of the blade. It is further provided that at least the leading edge of the impeller blade adjacent to its suction side has a geometric edge correction in the form of a rounded edge over a predetermined partial length of the entire blade thickness.

[0006] Single-layer metal sheet impeller blades are generally manufactured and formed in a forming process. The external geometry is achieved by trimming the metal sheet, resulting in the surface edges of the flat metal sheet raw material with two sharp outer edges (in the form of hemming) being blunted. From an aerodynamic perspective, airfoil profiles are known to be more suitable, but these cannot be produced with a single-layer metal sheet. The advantage of a single-layer metal sheet is that any free-form surface can be created as a three-dimensionally bent impeller blade, which is not possible in a hollow profile or can only be achieved to a limited extent. The edge correction in the form of a rounded edge on the suction side of the leading edge of the blade can achieve an effect equivalent to an ideally designed flow profile, thereby improving the efficiency of the impeller. In principle, it is sufficient to perform edge correction only on the leading edge of the suction side of the blade to achieve an increase in efficiency, and all other edges of the blade edge can be left without edge correction, so no subsequent treatment is required after forming and trimming.

[0007] The leading edge of the impeller blade adjacent to its pressure side is preferably designed without edge correction and retains the curled shape formed by trimming.

[0008] Edge correction in the form of rounding can be achieved by providing a continuous and constant radius on the sharp outer edge of the suction side of the surface edge of the flat metal sheet raw material remaining after the raw material is trimmed. The path of the edge correction can also have multiple different radii.

[0009] Advantageous effects are also achieved in the embodiment variant, where the edge correction is an oval in the form of rounding.

[0010] As another possibility of edge correction in the form of rounding, one solution provides that the rounding is formed by a chamfer. When observed from the cross-section, the chamfer can usually also have a discontinuous profile. However, the resulting transition is defined as rounding because the sharp outer edge on the surface edge of the flat metal sheet raw material is eliminated by the edge correction that has a positive effect on the flow.

[0011] However, what is unique about the embodiment variant of the radial or diagonal flow impeller is that the trailing edge of the impeller blade adjacent to the pressure side also has a geometric edge correction in the form of rounding over a predetermined partial length of the blade thickness. The variants described above can be used here. The edge correction of the trailing edge of the blade on the pressure side improves the generation of noise and thus provides additional acoustic advantages. An advantageous embodiment provides that the leading edge and the trailing edge of the impeller blade are designed to have the same shape of edge correction.

[0012] Therefore, the edge correction starts from the suction side of the impeller blade on the leading edge and from the pressure side on the trailing edge.

[0013] Furthermore, what is unique about the radial or diagonal flow impeller in an advantageous embodiment is that the edge correction along the leading edge of the blade on the suction side extends at least 20% of the blade thickness as a partial length in the direction of the pressure side of the leading edge starting from the outermost edge of the leading edge.

[0014] If the trailing edge of the blade is also equipped with edge correction, it is preferably provided that the edge correction along the trailing edge of the blade on the pressure side extends at least 20% of the blade thickness as a partial length in the direction of the suction side of the trailing edge starting from the outermost edge of the trailing edge.

[0015] In the case of a radial or diagonal flow impeller, it is also advantageously provided that the impeller blade has a constant blade thickness, i.e., a constant material strength of the metal sheet material.

[0016] Preferably, the unique feature of a radial or diagonal flow impeller is also that the impeller blades between the leading edge and the trailing edge of the blade are designed to be three-dimensionally bent by a forming process. The three-dimensional bending can simulate an airfoil profile with aerodynamic advantages. However, much less manufacturing technology work is required to produce three-dimensionally bent impeller blades from a single layer of metal sheet.

[0017] The radial or diagonal flow impeller preferably also includes a chassis and a cover disk connected by the impeller blades. The cover disk can be designed in different ways and can be designed as wavy and / or rotationally symmetric, particularly in the circumferential direction.

[0018] In order to produce edge correction, edge embossing can be carried out in a forming tool before the impeller blades are installed in the impeller. Alternatively, edge trimming can be carried out in the form of peripheral edge trimming of the integrally formed impeller blades. Finally, machining of the blade edges is also possible.

[0019] The features disclosed above can be combined as required, provided that this is technically feasible and not mutually contradictory. Description of the Drawings

[0020] Other advantageous developments of the present invention are characterized in the dependent claims or are presented in more detail below together with the description of the preferred embodiments of the present invention with reference to the drawings. It shows:

[0021] Figure 1 A perspective view showing a radial impeller;

[0022] Figure 2 Showing Figure 1 A sectional view of the radial impeller of

[0023] Figure 3a Showing Figure 1 And Figure 2 A detailed view of the leading edge of the blade of the radial impeller in

[0024] Figure 3b Showing Figure 1 And Figure 2 A detailed view of the trailing edge of the blade of the radial impeller in

[0025] Figure 4a An alternative embodiment of the detailed view of the leading edge of the blade of the radial impeller (detail C);

[0026] Figure 4b An alternative embodiment of the detailed view of the trailing edge of the blade of the radial impeller (detail D);

[0027] Figure 5a Showing another alternative embodiment of the detailed view of the leading edge of the blade for the radial impeller (detail E);

[0028] Figure 5b Another alternative embodiment showing a detailed view of the trailing edge of the blade for a radial impeller (detail F);

[0029] Figure 6 A graph showing the improvement in efficiency quality. Detailed Description

[0030] These figures are exemplary schematic diagrams. The same reference numerals in the figures denote the same functional and / or structural features.

[0031] Figure 1 Exemplarily shown is a radial impeller 1. However, the present invention can also be directly used for a diagonal impeller whose outflow direction is not radial but diagonal. The radial impeller 1 includes a chassis 2, a rotationally symmetric cover disk 3, and impeller blades 4 extending therebetween and arranged around the rotation axis. The cover disk 3 forms a suction inlet located at the center of the axis. The radial impeller 1 is made of a metal sheet, wherein the impeller blades 4 are connected to the base plate 2 and the cover disk 3, in particular by welding.

[0032] The impeller blade 4 is formed by a single-layer metal sheet having a constant material strength and blade thickness SD, and is bent backward on the one hand against the rotation direction of the radial impeller 1 set in the intended use, and on the other hand is three-dimensionally bent by a forming process, except Figure 1 It can also be clearly seen in the Figure 2 axial section of.

[0033] In the shown embodiment, each impeller blade 4 has the same shape and includes a suction side 11, a pressure side 12, a blade leading edge 5 on the suction side, and a blade trailing edge 6 on the outlet side.

[0034] Referring to the detailed view according to Figure 3a it can be seen that the suction-side blade leading edge 5 of the impeller blade 4 has a geometric edge correction in the form of a fillet 7 with a continuous radius. In the shown embodiment, the edge correction in the form of the fillet 7 extends along the blade leading edge 5 over the entire axial length, starting from the outermost edge of the blade leading edge 5 on the suction side 11 and extending in the direction of the pressure side 12 over a partial length L of approximately 50% of the blade thickness SD. The curled end 20 of the blade leading edge 5 on the pressure side 12 is a sharp edge and particularly forms a right-angled transition.

[0035] In Figure 1 and Figure 2 the shown exemplary embodiment, the blade trailing edge 6 is also provided with a fillet 7, but from the pressure side 12 in the direction of the suction side 11 of the corresponding impeller blade 4, as Figure 3bas shown in the detailed view. The curled end 21 of the trailing edge 6 of the blade on the suction side 11 is also a sharp edge, just like the leading edge 5 of the blade, and in particular also forms a right-angled transition.

[0036] In Figure 4a and Figure 5a for the leading edge 5 of the blade and Figure 4b and Figure 5b an alternative embodiment variant of the edge correction in the form of a rounding 7 is shown in the exemplary embodiments for the trailing edge 6 of the blade. In accordance with Figure 4a , Figure 4b the edge correction in the form of a rounding 7 is achieved by chamfering. In accordance with Figure 5a , Figure 5b the edge correction in the form of a rounding 7 is achieved by an ellipse and extends further along the chord length of the impeller blade 4. The partial length L is less than the solution in accordance with Figure 3a , Figure 3b and is only about 20% of the blade thickness SD.

[0037] Figure 6 shows a comparison diagram of the efficiencies of two identical radial impellers, where the dashed line A shows the characteristics of a radial impeller with a conventional blade leading edge, and the line B shows the characteristics 6 of the radial impeller 1 with a leading edge 6 of the blade with an edge correction in the form of a rounding 7. In particular, in the case where the volume flow rate is in the range of 1000 - 4000 m 3 / h, the efficiency is improved by the edge correction in the form of a rounding 7, and is very significant in the range of 1500 - 3000 m 3 / h.

Claims

1. A radial or mixed-flow impeller for a fan having impeller blades (4), said impeller blades (4) being bent in the circumferential direction about the axis of rotation and being formed from a single layer of metal sheet, said metal sheets each having a suction side (11) and a pressure side (12), as well as a leading edge (5) and a trailing edge (6) of the blade, wherein at least the leading edge (5) of the impeller blade (4) adjacent to its suction side (11) has a geometric edge modification in the form of a rounding (7) over a predetermined partial length of the blade thickness (SD) of the impeller blade (4), characterized in that, The leading edge (5) of the impeller blade (4) adjacent to its pressure side (12) is designed without edge correction and has a curled edge shape.

2. The radial or diagonal flow impeller according to claim 1, wherein The trailing edge (6) of the impeller blade (4) adjacent to the pressure side (12) has a geometric edge correction in the form of a rounding (7) over a predetermined partial length of the blade thickness (SD) of the impeller blade.

3. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The impeller blade (4) has a constant blade thickness (SD).

4. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The rounding (7) has a constant radius.

5. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The rounding is formed by a plurality of radii.

6. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The rounding is elliptical.

7. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The rounding is formed by a chamfer.

8. The radial or diagonal flow impeller according to claim 7, characterized in that, The leading edge (5) and the trailing edge (6) of the blade obtain an initial shape by a shearing edge, and the initial shape is provided with an edge correction by a forming process.

9. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The edge correction along the leading edge (5) on the suction side (11) extends as a partial length at least 20% of the blade thickness (SD) from the outermost edge of the leading edge (5) in the direction of the pressure side (12) of the leading edge (5).

10. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The edge correction along the trailing edge (6) on the pressure side (12) extends as a partial length at least 20% of the blade thickness (SD) from the outermost edge of the trailing edge (6) in the direction of the suction side (11) of the trailing edge (6).

11. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The impeller blade (4) between the leading edge (5) and the trailing edge (6) is three-dimensionally bent by a forming process.

12. The radial or diagonal flow impeller according to claim 1 or 2, characterized in that, The base disk (2) and the cover disk (3) are connected by the impeller blade (4).

13. The radial or diagonal flow impeller according to claim 12, characterized in that, The cover disk (3) is designed in a wavy shape and / or rotationally symmetric in the circumferential direction.

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