Diagonal impeller with varying hub area

Abstract

Diagonal impeller (1) with a conical hub (10) which widens from an inflow side (A) to an outflow side (B) in the radial direction (R), wherein a plurality of blades (20) extend radially outward from the hub (10), wherein a blade pair (23) of two immediately adjacent blades (21, 22) of the plurality of blades (20) defines between them a blade channel (2) through which flow can take place from the inflow side (A) to the outflow side (B), wherein the blade channel (2) is delimited radially inwardly by a surface of the hub (10) extending between the two blades (21, 22), wherein the surface of the hub (10) delimiting the blade channel (2) has a first section (11) and a subsequent second section (12) in the flow direction, wherein the surface is curved in the first section (11) and flat in the second section (12), and wherein all second sections (12) each correspond to partial surfaces of a side surface of an imaginary pyramid.

Description

[0001] The invention relates to a diagonal impeller, the hub of which, together with the blades of the diagonal impeller, defines blade channels, wherein the hub has a changing surface, ie a varying hub area, along the flow direction through the blade channel.

[0002] A variety of impellers for fans and ventilators are known from the state of the art. In addition to axial impellers and centrifugal impellers, there are also diagonal impellers, as disclosed, for example, in documents WO 2020 / 099027 A1 and DE 20 2010 013 785 U1.

[0003] So-called diagonal impellers, which can also be referred to as mixed-flow impellers, occupy a position between axial-flow impellers and centrifugal impellers with backward-curved blades. The typical design of a diagonal impeller, as it rotates around a rotational axis, creates an air or fluid flow similar to that of widely used axial fans while simultaneously achieving a higher static pressure.

[0004] The fluid to be pumped enters along the impeller axis, ie along the axis of rotation, on an inflow side and is blown out again at a certain angle to the axis of rotation on the outflow side, ie diagonally.

[0005] According to the state of the art, the hub of diagonal impellers is usually completely or purely conical, whereby the vortex formation in the pumped fluid is to be minimized by the conical shape of the impeller hub.

[0006] As with all impellers, diagonal impellers also experience losses, which impair efficiency and power density. Diagonal impellers also generate noise during operation, which can be disruptive depending on the application.

[0007] Furthermore, diagonal impellers in general and aspects relating to such diagonal impellers, such as a conical hub, are also known from the documents DE 10 2014 006 756 A1, DE 10 2017114 679 A1, DE 10 2018 128 821 A1, DE 10 2020 104 985 A1, DE 10 2020 114 389 A1, DE 20 2004 010 088 U1 and EP 2 218 917 B1.

[0008] The invention is therefore based on the object of overcoming the aforementioned disadvantages and increasing the efficiency and power density of a diagonal impeller as well as improving the noise behavior of a diagonal impeller rotating during operation.

[0009] This problem is solved by the combination of features according to patent claim 1.

[0010] According to the invention, a diagonal impeller with a conical hub is therefore proposed, which can be rotated in particular about a rotational axis, wherein the conical hub widens in the radial direction from an inflow side to an outflow side. As is usual with diagonal impellers, a plurality of blades extend radially outward from the hub. Two immediately adjacent blades of the plurality of blades each form a blade pair. The blade pair or pairs, or more precisely the two blades of the blade pairs, each define a blade channel between them through which fluid, for example air or another gas mixture, can flow from the inflow side to the outflow side. The blade channel is delimited radially inward by a surface of the hub extending between the two blades. Since this is the surface of the hub, it can also be referred to as the hub surface.It is essential that the hub surface bounding the blade channel has a first section and a subsequent second section in the flow direction, i.e., from the inflow side to the outflow side. The surface is curved in the first section or has a curvature, preferably in the radial direction, and is flat in the second section. The surface or hub area varies accordingly, so that the hub, in particular, is not purely or exclusively conical.

[0011] This results in a substantially angular or square shape of the hub or an angular or square cross-section or such a basic shape of the hub in a fluidically rearward, i.e., outflow-side, region of the hub, which is determined by the second sections of the surface. In a front, i.e., inflow-side, region of the hub, this is preferably determined by a common and rotationally symmetrical shape or a common and rotationally symmetrical, in particular round, cross-section or such a basic shape, as described below.

[0012] Unless already clear, it should be noted that the plurality of blades forms a plurality of blade pairs, each pair of which defines a blade channel between them. This results in a plurality of blade channels, each of which is bounded by a respective first section and a respective second section of the hub surface.

[0013] Furthermore, the diagonal impeller is rotatable about a rotation axis to which the diagonal impeller is arranged concentrically.

[0014] Although the prior art generally provides for the hub to have a completely and exclusively conical shape in which the cross-section is round at every point along the longitudinal axis, the first and second sections of the surface of the hub in the region of the blade channel(s) according to the invention ensure that the surface or the hub is / are leveled in the aerodynamically rear region of the blade channel(s). The leveling or flattening in the aerodynamically rear region of the blade channel expands the flow cross-section of the blade channel, which leads to an improvement in efficiency, particularly in very limited installation space. The inventive design of the diagonal impeller thus contributes to increasing the power density.

[0015] Typically for diagonal impellers, the outer diameter of the diagonal impeller, determined by the blades, can also be provided in this case, widening from the inlet side to the outlet side, preferably corresponding to the conical shape of the hub. If the blades are covered by a shroud (explained below), the shroud can also widen in diameter from the inlet side to the outlet side, preferably corresponding to the conical shape of the hub.

[0016] An advantageous development of the invention provides that the surface of the hub or the hub surface in the first section is rotationally symmetrical and / or convexly curved radially outwards to a rotation axis of the diagonal impeller and thus corresponds to a partial surface of a conical or conical body and preferably to a partial surface of the conical basic shape of the hub.

[0017] Preferably, all first sections of the surface of the hub correspond to partial surfaces of a common, ie single, imaginary cone or cone.

[0018] Alternatively, the first sections of the surface of the hub can also be partial surfaces of a common, i.e. single, imaginary sphere or hemisphere or an ellipsoid.

[0019] According to the invention, all second sections each correspond to partial surfaces of a side surface of an imaginary pyramid or an imaginary pyramid-shaped body. This means that such a pyramid or such a pyramid-shaped body, in addition to its base area, has a number of side surfaces corresponding to the number of second sections.

[0020] It also follows that, despite a conical basic shape, the hub does not have to be completely or purely conical, but the shape of the hub can correspond to a hybrid of a cone and a pyramid, in which the first sections form the conical part of the hub and the second sections form the pyramidal part of the hub.

[0021] To improve noise performance, the first section of the surface and the second section of the surface can also be designed to merge continuously and / or rounded and / or via a continuous, i.e., seamless, transition area. Such a transition results in fewer flow separations and eddies, thus correspondingly reducing noise.

[0022] The first section of the surface is preferably visible at least partially and in particular completely without overlap from an inflow-side plan view of the hub, i.e., it is visible and, in particular, is not overlapped by the blades of the respective associated blade pair. Additionally or alternatively, the second section of the surface can be covered at least partially by a blade from an inflow-side plan view of the hub, i.e., by a blade of the associated blade pair.

[0023] Furthermore, it can be provided that the surface of the hub has a third section in the flow direction after the second section, which is arranged on the outflow side of the blade channel, ie after the blade channel or outside the blade channel.

[0024] In this case, it is also preferably provided for noise reduction that the second section of the surface and the third section of the surface merge into one another continuously and / or rounded and / or via a continuous, ie again jump-free, transition region.

[0025] In particular, all second sections of the surface can merge into a common, i.e., single, third section, which is preferably an outer surface of an imaginary cylinder. This means that the outer surface of the cylinder or the third section of the surface of the hub completely surrounds the rotation axis, preferably in the circumferential direction, and furthermore preferably concentrically.

[0026] Furthermore, the diagonal impeller can have a shroud that partially covers the blades, ie, in particular, all of the blades of the plurality of blades on the inlet side, in a radially outer region and, in particular, defines an inlet opening radially inside. The blade channel(s) are thereby preferably delimited radially outward by the shroud. This results in the inventive design enabling smaller angular differences between the shroud and the hub, which also has a positive effect on noise behavior and efficiency.

[0027] Preferably, the blades, ie the blades of the blade pair and in particular all blades of the plurality of blades, each have an inflow-side base point and an outflow-side base point, at which the blades each adjoin the hub, merge into the hub, or are connected to it. According to the embodiment, a boundary line between the first section and the second section of the surface runs in particular in a straight line from an inflow-side base point of a first blade of the blade pair or of a respective blade pair to an outflow-side base point of a second blade of the blade pair or of the respective blade pair.

[0028] The first section of the surface preferably extends from the first blade of the blade pair to the boundary line and the second section of the surface from the boundary line to the second blade of the blade pair.

[0029] Furthermore, a further or second boundary line can also be located between the second section or sections and the third section of the surface, which in particular encircles an axis of rotation in a circle.

[0030] Furthermore, or alternatively, it can be provided that the boundary line between the second section(s) and the third section, i.e., the second or further boundary line, forms a tangent to the outflow-side base points of the blades and connects or tangentially connects them to one another. The boundary line between each two outflow-side base points of two blades arranged directly next to one another can be curved, in particular in the flow direction, and can have a kink at each of the outflow-side base points.

[0031] Although the diagonal impeller can be constructed in multiple parts, it is preferably designed as a single piece, so that the hub, blades, and, if present, the cover plate are integrally connected. Furthermore, the diagonal impeller is preferably manufactured using an injection molding process with one-piece vanes.

[0032] The features disclosed above can be combined as desired, as long as this is technically possible and they do not contradict each other.

[0033] Other advantageous developments of the invention are characterized in the subclaims or are presented in more detail below, together with the description of the preferred embodiment of the invention, with reference to the figures. They show: Fig. 1 inlet-side perspective view of a diagonal impeller; Fig. 2 Side view of the diagonal impeller; Fig. 3 outflow-side perspective view of the diagonal impeller; Fig. 4a,b inlet side view of the diagonal impeller; Fig. 5 Inlet side plan view of the diagonal impeller with cross-sections of schematic basic bodies.

[0034] The figures are schematic examples. Identical reference numerals in the figures indicate identical functional and / or structural features.

[0035] In Fig. 1 shows a diagonal impeller 1 in perspective, with the diagonal impeller being viewed from the inlet side A.

[0036] The diagonal impeller 1 has a hub 10, from which blades 20, and in this case specifically five blades 20, extend outwards in the radial direction R. Furthermore, the completely integrally formed diagonal impeller 1 has a cover disk 30, which completely surrounds the rotation axis X in the circumferential direction U and is connected to the blades 20 in a radially outer region thereof, so that an inlet opening 3 remains free radially inside.

[0037] Each two immediately adjacent blades 20 of the total of five blades 20 form a blade pair 23, so that there are correspondingly five blade pairs 23. For better clarity, only one blade pair 23 is provided with the corresponding reference symbol. Fig. 4b a section with exactly one pair of blades 23 of the intake-side plan view of the diagonal impeller 1 according to Fig. 4a shown.

[0038] Each of the blade pairs 23 has a first blade 21 and a second blade 22, which define a blade channel 2 between them, through which a Fig. 2, the flow S shown as an example can flow from the inflow side A to the outflow side B or is conveyed by the rotation of the diagonal impeller 1 around the rotation axis X.

[0039] In addition to the surfaces of the first blade 21 and second blade 22 facing the respective blade channel 2, the blade channels 2 are each delimited radially inward by the hub 10 or the surface of the hub 10. According to the illustrated embodiment, the blade channels 2 are delimited radially outward by the cover plate 30.

[0040] It is important that the surface of the hub 10 delimiting the blade channel 2 has a first section 11 and a subsequent second section 12 in the flow direction, wherein the surface is curved in the first section 11 or has a curvature in the radial direction R and is flat in the second section 12. The two sections 11, 12 as well as the transition area 14 between them are particularly shown in the detailed representation of the Fig. 4b. This advantageously shows that the flow cross-section, ie the cross-section of the flow channel 2, increases in its area adjacent to the second section 12, particularly compared to its area adjacent to the first section 11, which leads to an improvement in efficiency.

[0041] In order to avoid flow separation and vortices arising from a sharp transition between the first section 11 and the second section 12, the transition region 14 between the first and the second section 11, 12 of the surface of the hub 10 is rounded, resulting in a relatively wide transition region 14 which, however, runs along a boundary line or covers or replaces it.

[0042] Furthermore, it is provided that the hub 10, in addition to the substantially conical section, ie the section widening in the radial direction R, in which the first and second sections 11, 12 are located, has a cylindrical section which determines a third section 13 of the surface of the hub 10. As can be seen particularly in the side view according to Fig. 2, the second sections 12, ie all five second sections 12, each merge into a common third section 13 by means of a corresponding further transition area 15, wherein the transition area 15 from the second sections 12 to the third section 13 is also rounded or continuous to minimize noise and runs along a corresponding boundary line between the second sections 12 and the third section 13 or covers or replaces them.

[0043] At the Fig. 2, it is clearly visible that the boundary line and thus the transition region 15 between the respective second sections 12 and the third section 13 does not run in a straight line, but is curved or bulbous in the flow direction from the outflow-side base point 25 to the outflow-side base point 25 of two immediately adjacent blades 20.

[0044] Due to the flattening of the hub 10 or the surface of the hub 10 in the second sections 12, the hub 10 is not completely conical, but partially angular or pyramid-shaped. This flattening, ie the flat formation of the surface in its second section 12 or in its second sections 12, is in Fig. 3 clearly visible.

[0045] Deviating from the transition area 15 between the respective second section 12 to the third section 13, the transition area 14 from the first section 11 to the second section 12 does not run from the outflow-side base point 25 to the outflow-side base point 25, but - as in Fig. 4a for all five transition areas 14 visible - from an inflow-side root point 24 of a first blade 21 of a blade pair 23 of two immediately adjacent blades 20 to an outflow-side root point 25 of a second blade 22 of the blade pair 23 of two immediately adjacent blades 20. In addition, the transition area 14 between the first section 11 and the second section 12 runs in a straight line between these root points 24, 25 for flow optimization.

[0046] Fig. 4b corresponds to an enlarged detailed view of the diagonal impeller 1 according to Fig. 4a, wherein in particular a blade pair 23 formed from two directly adjacent blades 20 and the blade channel 2 defined by the blade pair 23 are depicted. This also makes the curved first section 11 of the surface of the hub 10, the flat or level second section 12 of the surface of the hub 10, and the transition region 14 between the first section 11 and the second section 12 particularly clearly visible.

[0047] The inflow side plan view in Fig. 5 corresponds to the inflow side plan view according to Fig. 4a, wherein imaginary section lines 16, 18 and base surfaces 17, 19 are drawn in for a clearer representation of the mixed form of the hub 10 consisting of a cone and a pyramid resulting from the first sections 11 and the second sections 12.

[0048] The first sections 11 here correspond to partial surfaces of a single imaginary cone, which also determines the conical basic shape of the hub 10. In a cross-section through the hub 10, the intersection lines 16 running in the first sections 11 form corresponding partial circles or parts of a common, i.e., single, circle 17.

[0049] Furthermore, the second sections 12 each correspond to partial surfaces of a side surface of a single imaginary and, in this case, five-sided pyramid, which determines the angular partial shape of the hub 10 or the angular portion of the shape of the hub 10. In a cross-section through the hub 10, the section lines 18 running in the second sections 12 form corresponding lines as parts of a side surface of a common, i.e., single, pentagon 19, i.e., a regular pentagon 19.

[0050] As shown, the blades 20 of the diagonal impeller 1 are preferably evenly distributed and curved in the circumferential direction U around the rotation axis. In particular, the curvature of the blades 20 results in the second section 12 being curved from the inflow-side plan view of the hub 10, ie as shown in the Fig. 4a, Fig. 4b and Fig. 5, is partially covered by one of the blades 20 of the blade pair 23 and the first section 11 of the surface is free of coverage.

[0051] The invention is not limited to the preferred embodiments described above. Rather, a number of variants are conceivable that utilize the presented solution even in fundamentally different embodiments.

Claims

[1] Diagonal impeller (1) with a conical hub (10) which widens from an inlet side (A) to an outlet side (B) in the radial direction (R), wherein a plurality of blades (20) extend radially outward from the hub (10), wherein a blade pair (23) of two immediately adjacent blades (21, 22) of the plurality of blades (20) defines between them a blade channel (2) through which flow can take place from the inflow side (A) to the outflow side (B), wherein the blade channel (2) is delimited radially inwardly by a surface of the hub (10) extending between the two blades (21, 22), wherein the surface of the hub (10) delimiting the blade channel (2) has a first section (11) and a subsequent second section (12) in the flow direction, wherein the surface is curved in the first section (11) and flat in the second section (12), and wherein all second sections (12) each correspond to partial surfaces of a side surface of an imaginary pyramid. [2] Diagonal impeller according to claim 1, wherein the surface in the first section (11) is rotationally symmetrical and / or convexly curved radially outward to an axis of rotation (X). [3] Diagonal impeller according to claim 1 or 2, wherein all first sections (11) each correspond to partial surfaces of a common imaginary cone or a common imaginary sphere or a common imaginary ellipsoid. [4] Diagonal impeller according to one of the preceding claims, wherein the first section (11) of the surface and the second section (12) of the surface merge continuously and / or rounded and / or via a continuous transition region (14). [5] Diagonal impeller according to one of the preceding claims, wherein the first section (11) of the surface is at least partially and in particular completely free of overlap from an inflow-side plan view of the hub (10), and / or wherein the second portion (12) of the surface is at least partially covered by a blade (20, 22) from an inflow-side plan view of the hub (10). [6] Diagonal impeller according to one of the preceding claims, wherein the surface of the hub (10) has a third section (13) in the flow direction after the second section (12), which is arranged on the outflow side of the blade channel (2). [7] Diagonal impeller according to the preceding claim, wherein the second section (12) of the surface and the third section (13) of the surface merge continuously and / or rounded and / or via a continuous transition region (15). [8] Diagonal impeller according to one of the two preceding claims, wherein all second sections (12) of the surface merge into a common third section (13). [9] Diagonal impeller according to the preceding claim, wherein the common third section (13) is an outer surface of an imaginary cylinder. [10] Diagonal impeller according to one of the preceding claims 6 to 9, wherein a boundary line between the second section (12) and the third section (13) of the surface runs in particular in a circle around an axis of rotation (X). [11] Diagonal impeller according to one of the preceding claims, further comprising a cover plate (30) which partially covers the blades (20, 21, 22) on the inflow side in a radially outer region. [12] Diagonal impeller according to one of the preceding claims, wherein the blades (20, 21, 22) each have an inflow-side base point (24) and an outflow-side base point (25), at which the blades (20, 21, 22) each adjoin the hub (10) or merge into the hub (10) or are connected to the hub (10), and wherein a boundary line between the first section (11) and the second section (12) of the surface runs in particular in a straight line from an inflow-side base point (24) of a first blade (21) of the blade pair (23) to an outflow-side base point (25) of a second blade (22) of the blade pair (23).

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