Radial or diagonal impeller with modified blade edge

Description

[0001] The invention relates to a radial or diagonal impeller for a fan with impeller blades made of sheet metal that are curved in the circumferential direction around a rotation axis.

[0002] Radial or diagonal impellers are known from the state of the art and are made from various materials. Depending on the desired location and purpose, both plastics, sometimes fiber-reinforced, and metals in the form of sheet metal are used. Fan blades made of sheet metal are manufactured as hollow profile blades or with a constant material thickness.

[0003] Curved sheet metal fan blades are typically manufactured through a forming process and trimming from the raw material. This results in a blunt blade end at both the leading and trailing edges, with two sharp edges at the ends of the two opposing blade surfaces, which fluidically determine the suction and pressure sides of the respective impeller blade. Such impeller blades can be installed directly into the impeller without any further processing.

[0004] Printed prior art from the present technical field is known, for example, from documents US 2019 / 024674 A1, US 2019 / 293083 A, EP 2 461 041 A1, and US 2017 / 284412 A1. The invention is based on the object of providing a radial or diagonal impeller formed from a single-layer sheet metal with curved impeller blades, which has increased efficiency compared to conventional impellers.

[0005] According to the invention, a radial or diagonal impeller according to claim 1 is proposed.

[0006] Single-layer sheet metal impeller blades are typically manufactured and shaped in a forming process. The outer geometry is achieved by trimming the sheet metal, creating blunt surface edges of the flat sheet metal raw material with two sharp outer edges (folded shape). From a fluid dynamics perspective, airfoil profiles are known to be more suitable, but these cannot be manufactured with single-layer sheet metal. The advantage of single-layer sheet metal is that any desired free-form surfaces can be created as three-dimensionally curved impeller blades, something that is not possible or only possible to a limited extent with hollow profiles. Edge modification in the form of a rounded section on the suction side of the blade leading edge makes it possible to achieve an effect comparable to that of an ideally designed flow profile and thus increase the impeller's efficiency.In principle, it is sufficient to provide only the leading edge of the blade on the suction side with the edge modification in order to achieve the efficiency improvement; all other edges of the blade edges can remain without edge modification and thus do not require any further processing after the shaping trimming.

[0007] According to the invention, the leading edge of the impeller blades adjacent to their pressure side is formed without the edge modification and retains the chamfered shape created by the trimming.

[0008] Edge modification in the form of a rounding can be achieved by providing a continuous, constant radius on the sharp outer edge of the surface edges of the flat sheet metal raw material on the suction side, which remains after trimming. The edge modification can also have several different radii.

[0009] The advantageous effect is also achieved in a design variant in which the edge modification is elliptical in the form of a rounding.

[0010] Another possible way of modifying edges in the form of a fillet is to create a chamfer. The chamfer can also have the discontinuous shape typically seen in cross-section. The resulting transition is nevertheless defined as a fillet, since a sharp outer edge at the surface edges of the flat sheet metal raw material is eliminated by an edge modification that positively influences the flow.

[0011] However, one design variant of the radial or diagonal impeller is characterized in that the trailing edge of the impeller blades adjacent to the pressure side also has a geometric edge modification in the form of rounding over a predetermined portion of the blade thickness. The variants described above can be used here. The edge modification of the pressure-side blade trailing edge improves noise generation and thus provides additional acoustic benefits. A favorable design provides for the blade leading edge and the trailing edge of the impeller blades to be identical in shape with regard to the edge modification.

[0012] The edge modification at the blade leading edge is therefore formed starting from the suction side, and at the blade trailing edge starting from the pressure side of the impeller blades.

[0013] Furthermore, in an advantageous embodiment, the radial or diagonal impeller is characterized in that 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.

[0014] If the blade trailing edge is also provided with an edge modification, it is preferably provided that the edge modification extends 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, as a partial length over at least 20% of the blade thickness.

[0015] In the case of the radial or diagonal impeller, it is also advantageously provided that the impeller blades have a constant blade thickness, ie a constant material thickness of the sheet material.

[0016] The radial or diagonal impeller is further preferably characterized in that the impeller blades are three-dimensionally curved between the leading and trailing edges through a forming process. This three-dimensional curvature enables the simulation of aerodynamically advantageous airfoil profiles. However, the manufacturing effort required to produce three-dimensionally curved impeller blades from single-layer sheet metal is much lower.

[0017] The radial or diagonal impeller preferably further comprises a base plate and a cover plate, which are connected by the impeller blades. The cover plate can be designed in various ways and, in particular, can be wave-shaped and / or rotationally symmetrical in the circumferential direction.

[0018] To create the edge modification, either edge stamping can be performed in the forming tool before the impeller blades are mounted in the impeller. Alternatively, the edge trimming can be performed by circumferential edge trimming of the impeller blades with integrated forming. Finally, machining of the blade edges is also possible.

[0019] The features disclosed above can be combined as desired, as long as this is technically possible and they do not contradict each other.

[0020] Other advantageous developments of the invention are described in more detail below, together with the description of the preferred embodiment of the invention, with reference to the figures. They show: Fig. 1 a perspective view of a radial impeller; Fig. 2 a sectional view through the radial impeller from Figure 1 ; Fig. 3a a detailed view of a blade leading edge of the radial impeller from the Figures 1 and 2(Detail A); Fig. 3b Detailed view of a blade trailing edge of the radial impeller from the Figures 1 and 2 (Detail B); Fig. 4a an alternative embodiment to the detailed view of the blade leading edge of the radial impeller (Detail C); Fig. 4b an alternative embodiment to the detailed view of the blade trailing edge of the radial impeller (Detail D); Fig. 5a a further alternative embodiment to the detailed view of the blade leading edge of the radial impeller (Detail E); Fig. 5b a further alternative embodiment to the detailed view of the blade trailing edge of the radial impeller (Detail F);

[0021] Fig. 6 a diagram for qualitatively increasing efficiency.

[0022] The figures are schematic examples. Identical reference numerals in the figures indicate identical functional and / or structural features.

[0023] Figure 1shows, by way of example, a radial impeller 1. However, the invention is also directly applicable to diagonal impellers in which the discharge direction is not radial, but diagonal. The radial impeller 1 comprises a base plate 2, a rotationally symmetrical cover plate 3, and impeller blades 4 extending therebetween and arranged around the axis of rotation. The cover plate 3 forms the axially central intake opening. The radial impeller 1 is made of sheet metal, with the impeller blades 4 being connected, in particular welded, to the base plate 2 and the cover plate 3.

[0024] The impeller blades 4 are formed from a single-layer sheet with constant material thickness and blade thickness SD and are curved, on the one hand, backwards against the direction of rotation of the radial impeller 1 as intended in the intended use, and, on the other hand, three-dimensionally by a forming process, as is the case in Figure 1 also in the axial section of the Figure 2 is clearly visible.

[0025] Each of the impeller blades 4 is of identical shape in the embodiment shown and comprises a suction side 11, a pressure side 12 as well as a suction-side blade leading edge 5 and a discharge-side blade trailing edge 6.

[0026] Referring to the detailed view according to Figure 3aIt can be seen that the intake-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, starting 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, which corresponds to approximately 50% of the blade thickness SD. The beveled end 20 of the blade leading edge 5 on the pressure side 12 has sharp edges and, in particular, forms a transition at a right angle.

[0027] The blade trailing edges 6 are in the embodiment shown according to the Figures 1 and 2 also provided with the rounding 7, but starting 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 the Fig. 3bshown. 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 in particular also forms a transition at a right angle.

[0028] Alternative embodiments of the edge modification in the form of a rounding 7 are shown in the embodiments of the Figures 4a and 5a for the blade leading edges 5 and 4b and 5b for the blade trailing edges 6. In the embodiment according to the Figures 4a, 4b the edge modification in the form of a rounding 7 is realized by a chamfer, in the embodiment according to the Figures 5a, 5b the edge modification in the form of a rounding 7 is implemented by an elliptical shape which extends further along the chord length of the impeller blades 4.

[0029] The partial length L is then smaller than in the solution according to the Figures 3a, 3b and is only about 20% of the blade thickness SD.

[0030] Figure 6 shows a diagram comparison of the efficiency of two identical radial impellers, where the dashed line A shows the characteristic curve of the radial impeller with conventional blade leading edges, and line B shows the characteristic curve of the radial impeller 1 with blade leading edges 6 with edge modification in the form of rounding 7. The increase in efficiency due to the edge modification in the form of rounding 7 is particularly evident at volume flows in the range of 1000-4000 m 3 / h and significant in the range of 1500-3000 m 3 / h.

Claims

1. A radial or diagonal impeller for a fan with impeller blades (4) curved about an axis of rotation in the circumferential direction, formed from a single-layer sheet metal, which each have 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 blades (4) adjacent to their suction side (11) has a geometrical edge modification in the shape of a rounding (7) limited over a predetermined partial length of a blade thickness (SD) of the impeller blades (4), characterised in that the blade leading edge (5) of the impeller blades (4) adjacent to their pressure side (12) is designed without the edge modification and has a bevelled shape.

2. The radial or diagonal impeller according to claim 1, characterised in that the blade trailing edge (6) of the impeller blades (4) adjacent to the pressure side (12) has a geometrical edge modification in the shape of a rounding (7) over a predetermined partial length of the blade thickness (SD).

3. The radial or diagonal impeller according to any one of the preceding claims, characterised in that the impeller blades (4) have a constant blade thickness (SD).

4. The radial or diagonal impeller according to any one of the preceding claims, characterised in that the rounding (7) has a constant radius.

5. The radial or diagonal impeller according to any one of the preceding claims, characterised in that the rounding is formed by several radii.

6. The radial or diagonal impeller according to any one of the preceding claims 1-3, characterised in that the rounding is elliptically designed.

7. The radial or diagonal impeller according to any one of the preceding claims 1-3, characterised in that the rounding is formed by a chamfer.

8. The radial or diagonal impeller according to the preceding claim, characterised in that the blade leading edge (5) and the blade trailing edge (6) obtain an initial shape through edge trimming and the initial shape is provided with the edge modification through a reshaping process.

9. The radial or diagonal impeller according to any one of the preceding claims, characterised in that the edge modification extends along the blade leading edge (5) on the suction side (11) starting from an outermost border of the blade leading edge (5) in the direction of the pressure side (12) of the blade leading edge (5) as a partial length over at least 20% of the blade thickness (SD).

10. The radial or diagonal impeller according to any one of the preceding claims 2-9, characterised in that the edge modification extends along the blade trailing edge (6) on the pressure side (12) starting from an outermost border of the blade trailing edge (6) in the direction of the suction side (11) of the blade trailing edge (6) as a partial length over at least 20% of the blade thickness (SD).

11. The radial or diagonal impeller according to any one of the preceding claims, characterised in that the impeller blades (4) between the blade leading edge (5) and the blade trailing edge (6) are designed to be three-dimensionally curved through a reshaping process.

12. The radial or diagonal impeller according to any one of the preceding claims, characterised by a bottom disc (2) and a cover disc (3) which are connected through the impeller blades (4).

13. The radial or diagonal impeller according to the preceding claim, characterised in that the cover disc (3) is designed to be wave-shaped and / or rotationally symmetrical in the circumferential direction.