EP4123180A1 - Radial or diagonal impeller with modified blade edge - Google Patents

Abstract

The invention relates to a radial or diagonal impeller with impeller blades (4) curved in the circumferential direction about an axis of rotation and formed from a single-layer sheet metal, each of which has a suction side (11) and a pressure side (12) as well as a blade front edge (5) and a blade rear edge (6). wherein at least the blade front edge (5) of the impeller blades (4) adjacent to their suction side (11) has 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).

Description

The invention relates to a radial or diagonal impeller for a fan with impeller blades made of sheet metal and curved in the circumferential direction about an axis of rotation.

Radial or diagonal impellers made of various materials are known from the prior art. In particular, depending on the desired place of use and purpose, both plastics, some fiber-reinforced, and metals in the form of sheet metal are used. Sheet metal fan blades are manufactured as hollow profile blades or with a constant material thickness.

The curved sheet metal fan blades are usually produced by a forming process and trimming of the raw material. This results in both the blade leading edge and the blade trailing edge a blunt blade end with two sharp edges each at the ends of the two opposite blade surfaces, which fluidically determine the suction side and the pressure side of the respective impeller blade. Such impeller blades can be used directly in the impeller without any post-processing.

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 an increased efficiency compared to conventional impellers.

According to the invention, a radial or diagonal impeller is proposed which has impeller blades curved about its axis of rotation in the circumferential direction. The impeller blades are formed from a single layer of sheet metal and each have a suction side and a pressure side as well as a blade leading edge and a blade trailing edge. In addition, it is provided that at least the blade front edge of the impeller blades has a geometric edge modification in the form of a rounding, limited to the suction side thereof over a predetermined partial length of the full blade thickness.

Single-layer sheet metal impeller blades are usually manufactured and shaped in a forming process. The outer geometry is achieved by trimming the sheet metal, resulting in blunt surface edges of the flat sheet metal raw material with two sharp outer edges (bent shape). From an aerodynamic point of view, airfoil profiles are known to be better suited, but these cannot be produced with single-layer sheet metal. The advantage of the single-layer sheet is that any free-form surfaces can be created as three-dimensionally curved impeller blades, which is not possible or only possible with hollow profiles limited is possible. The edge modification in the form of a rounding 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 to increase the efficiency of the impeller. 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 improvement in efficiency; all other edges of the blade edges can remain without edge modification and thus remain post-processing-free after the shaping trimming.

The blade leading edge of the impeller blades adjacent to the pressure side thereof is preferably formed without the edge modification and retains the folded shape created by the trimming.

The edge modification in the form of a rounding can be achieved by providing a continuous, constant radius on the suction-side sharp outer edge of the surface margins of the flat sheet metal raw material remaining after the raw material has been trimmed. The course of the edge modification can also have several different radii.

The advantageous effect is also achieved in an embodiment variant in which the edge modification is elliptical in the form of a rounding.

As a further possibility for edge modification in the form of a rounding, one solution provides that the rounding is formed by a chamfer. The chamfer can also have the discontinuous course that is usual when viewed in cross section. The resulting transition is nevertheless defined as a rounding, since a sharp outer edge on the surface edges of the sheet metal raw material has a positive effect on the flow influencing edge modification is eliminated.

However, an embodiment 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 partial length of the blade thickness. The variants described above can be used here. The edge modification of the blade trailing edge on the pressure side improves the generation of noise and consequently provides additional acoustic advantages. A favorable embodiment provides that the blade front edge and the blade rear edge of the impeller blades are designed to be identical in shape with regard to the edge modification.

The edge modification on the blade front edge is therefore formed starting from the suction side, on the blade trailing edge starting from the pressure side of the impeller blades.

Furthermore, the radial or diagonal impeller in an advantageous embodiment 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.

If the blade trailing edge is also equipped with an edge modification, it is preferably provided that 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.

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 metal material.

The radial or diagonal impeller is also preferably characterized in that the impeller blades between the blade front edge and the blade rear edge are designed to be three-dimensionally curved by a forming process. The three-dimensional curvature enables the imitation of aerodynamically advantageous airfoil profiles. However, the manufacturing effort required to produce three-dimensionally curved impeller blades from single-layer sheet metal is far less.

The centrifugal or diagonal impeller preferably also comprises a bottom disk and a cover disk, which are connected by the impeller blades. The cover disk can be designed in different ways and in particular can be embodied in a wavy and/or rotationally symmetrical manner in the circumferential direction.

To produce the edge modification, either an edge embossing can take place in the forming tool before the impeller blades are mounted in the impeller. Alternatively, the edge trimming can take place in the form of a peripheral edge trimming of the impeller blades with integrated forming. Finally, machining of the blade edges would also be possible.

The features disclosed above can be combined as desired, insofar as this is technically possible and they do not contradict one another.

Fig. 1

eine perspektivische Ansicht auf ein Radiallaufrad;

Fig. 2

eine Schnittansicht durch das Radiallaufrad aus Figur 1;

Fig. 3a

eine Detailansicht einer Schaufelvorderkante des Radiallaufrads aus den Figuren 1 und 2 (Detail A);

Fig. 3b

eine Detailansicht einer Schaufelhinterkante des Radiallaufrads aus den Figuren 1 und 2 (Detail B);

Fig. 4a

eine alternative Ausgestaltung zur Detailansicht der Schaufelvorderkante des Radiallaufrads (Detail C);

Fig. 4b

eine alternative Ausgestaltung zur Detailansicht der Schaufelhinterkante des Radiallaufrads (Detail D);

Fig. 5a

eine weitere alternative Ausgestaltung zur Detailansicht der Schaufelvorderkante des Radiallaufrads (Detail E);

Fig. 5b

eine weitere alternative Ausgestaltung zur Detailansicht der Schaufelhinterkante des Radiallaufrads (Detail F);

Fig. 6

ein Diagramm zur qualitativen Steigerung des Wirkungsgrades.

Other advantageous developments of the invention are characterized in the dependent claims or are presented in more detail below together with the description of the preferred embodiment of the invention with reference to the figures. Show it:

1

a perspective view of a radial impeller;

2

a sectional view through the radial impeller figure 1 ;

Figure 3a

a detailed view of a blade leading edge of the radial impeller from FIGS Figures 1 and 2 (Detail A);

Figure 3b

a detailed view of a blade trailing edge of the radial impeller from FIGS Figures 1 and 2 (Detail B);

Figure 4a

an alternative embodiment to the detailed view of the blade leading edge of the radial impeller (detail C);

Figure 4b

an alternative embodiment to the detailed view of the blade trailing edge of the radial impeller (detail D);

Figure 5a

a further alternative embodiment for a detailed view of the blade leading edge of the radial impeller (detail E);

Figure 5b

a further alternative embodiment for a detailed view of the blade trailing edge of the radial impeller (detail F);

6

a diagram for the qualitative increase in efficiency.

The figures are schematic by way of example. The same reference numbers in the figures indicate the same functional and/or structural features.

figure 1 1 shows a radial impeller 1 by way of example. However, the invention can also be applied directly to diagonal impellers in which the outflow direction is not radial, but diagonal. The radial impeller 1 comprises a base disk 2, a rotationally symmetrical cover disk 3 and impeller blades 4 extending between them and arranged around the axis of rotation. The cover disk 3 forms the suction opening located centrally in the axis. That Radial impeller 1 is made of sheet metal, the impeller blades 4 being connected, in particular welded, to the base disk 2 and the cover disk 3 .

The impeller blades 4 are formed from a single-layer sheet metal with a constant material thickness and blade thickness SD and, on the one hand, are curved backwards against the direction of rotation of the radial impeller 1 provided for the intended use, and on the other hand are three-dimensionally curved by a forming process, as is shown next to figure 1 also in axial section of figure 2 is easy to see.

In the embodiment shown, each of the impeller blades 4 is identical in shape and comprises a suction side 11, a 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.

Referring to the detailed view according to Figure 3a it can be seen that 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 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 is approx. 50% of the Blade thickness corresponds to SD. The folded 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.

The blade trailing edges 6 are in the embodiment shown according to Figures 1 and 2 also provided with the fillet 7, however starting from the pressure side 12 in the direction of the suction side 11 of the respective impeller blade 4, as in the detailed view of FIG Figure 3b shown. 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 right angles.

Alternative variants of the edge modification in the form of a rounding 7 are in the embodiments figures 4a and 5a for the blade leading edges 5 and 4b and 5b for the blade trailing edges 6 are shown. In the embodiment according to the Figures 4a, 4b are the edge modification in the form of a rounding 7 realized by a chamfer, in the embodiment according to Figures 5a, 5b For example, the edge modification in the form of a fillet 7 is implemented by an elliptical shape that extends further along the chord length of the impeller blades 4. The partial length L is then less than in the solution according to Figures 3a, 3b and is only about 20% of the blade thickness SD.

figure 6 shows a diagram comparison of the efficiency of two identical radial impellers, with the dashed line A showing the characteristic of the radial impeller with conventional blade leading edges, line B showing the characteristic 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 given in particular for volume flows in the range of 1000-4000m ³ /h and is significant in the range of 1500-3000m 3 /h.

Claims (14)

Radial or diagonal impeller with impeller blades (4) curved in the circumferential direction about an axis of rotation and formed from a single-layer sheet metal, which each have a suction side (11) and a pressure side (12) as well as a blade front edge (5) and a blade rear edge (6), with at least the blade leading edge (5) of the impeller blades (4) adjacent to their suction side (11) has a geometric edge modification in the form of a rounding (7) limited over a predetermined partial length of a blade thickness (SD) of the impeller blades (4). Radial or diagonal impeller according to Claim 1, characterized in that the leading edge (5) of the impeller blades (4) adjacent to their pressure side (12) is formed without the edge modification and has a beveled shape. Radial or diagonal impeller according to Claim 1 or 2, characterized in that the blade trailing edge (6) of the impeller blades (4) adjacent to the pressure side (12) has a geometric edge modification in the form of a rounding (7) over a predetermined partial length of the blade thickness (SD). having. Radial or diagonal impeller according to one of the preceding claims, characterized in that the impeller blades (4) have a constant blade thickness (SD). Radial or diagonal impeller according to one of the preceding claims, characterized in that the rounding (7) has a constant radius. Radial or diagonal impeller according to one of the preceding claims, characterized in that the rounding is formed by a plurality of radii. Radial or diagonal impeller according to one of the preceding claims 1 - 4, characterized in that the rounding is elliptical. Radial or diagonal impeller according to one of the preceding claims 1 - 4, characterized in that the rounding is formed by a chamfer. Radial or diagonal impeller according to the previous claim, characterized in that the blade front edge (5) and the blade rear edge (6) are given an initial shape by edge trimming and the initial shape is provided with the edge modification by a forming process. Radial or diagonal impeller according to one of the preceding claims, characterized in that the edge modification along the blade front edge (5) on the suction side (11) starting from an outermost edge of the blade front edge (5) in the direction of the pressure side (12) of the blade front edge (5) extends as a partial length over at least 20% of the blade thickness (SD). Radial or diagonal impeller according to one of the preceding claims 2-10, characterized in that the edge modification along the blade trailing edge (6) on the pressure side (12) starting from an outermost edge of the blade trailing edge (6) in the direction of the suction side (11) of the blade trailing edge (6) extends as a partial length over at least 20% of the blade thickness (SD). Radial or diagonal impeller according to one of the preceding claims, characterized in that the impeller blades (4) between the blade front edge (5) and the blade rear edge (6) are three-dimensionally curved by a forming process. Radial or diagonal impeller according to one of the preceding claims, characterized by a base disk (2) and a cover disk (3), which are connected by the impeller blades (4). Radial or diagonal impeller according to the preceding claim, characterized in that the cover disk (3) is of wavy and/or rotationally symmetrical design in the circumferential direction.

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