Side channel pump device

Abstract

Side channel pump devices (10) are known which comprise a pump housing (12), a flow channel (14) which is formed in the pump housing (12), and an impeller (20) which is rotatably mounted in the pump housing (12), said impeller (20) comprising a bearing portion (22), which is provided radially inside and via which the impeller (20) is rotatably mounted about an axis of rotation (R) in the pump housing (12), a blade portion (26), which is provided radially outside and has a plurality of blades (27, 28), and a connecting portion (24) which connects the blade portion (26) to the bearing portion (22). A first connection (23) of the connecting portion (24) to the bearing portion (22) lies on a first radial plane (E1), and a second connection (25) of the connecting portion (24) to the blade portion (26) lies on a second radial plane (E2), said two radial planes (E1, E2) being parallel to each other and mutually spaced in the axial direction. According to the invention, the connecting portion (24) is connected to the blade portion (26) eccentrically with respect to the axial extent (L) of the blade portion (26), whereby deformations of the impeller (20) which change the sealing gap (21) are compensated for.

Description

[0001] DESCRIPTION

[0002] Side channel pump device

[0003] The present invention relates to a side-channel pump device comprising a pump housing, a flow channel formed in the pump housing, an impeller rotatably arranged in the pump housing, the impeller comprising a radially inner bearing section by means of which the impeller is rotatably mounted about an axis of rotation in the pump housing, a radially outer impeller section with a plurality of vanes movable through the flow channel, and a connecting section connecting the impeller section to the bearing section, wherein a first connection of the connecting section to the bearing section is on a first radial plane, and a second connection of the connecting section to the impeller section is on a second radial plane, and the two radial planes are arranged parallel and axially spaced apart from each other.

[0004] Such a side channel pumping device is known, for example, from EP 3 045 731 Al.

[0005] The axial offset of the connection points is advantageous with regard to the use of installation space and results in a particularly compact axial side channel pump device.

[0006] At high rotational speeds, however, significant centrifugal forces act on the connecting section and the adjoining wing section, causing elastic deformation of the connecting section. Due to the axial offset between the connection point of the connecting section on the wing section and the connection point of the connecting section on the bearing section, the connecting section extends both radially and axially. Consequently, the connecting section deforms such that its radially outer end, and thus the second connection, shifts both radially and axially relative to the first connection. More precisely, viewed in a cross-sectional plane, the outer end of the connecting section shifts along a circular path around the first connection. This effect is subsequently referred to as the righting moment.

[0007] The installation torque has a negative effect on the relatively narrow and preferably constant sealing gaps of the side channel pump, since the deformation of the connecting section also displaces the adjoining impeller section in the flow channel, leading to a non-uniformity of the sealing gaps surrounding the impeller and, in particular, the radial sealing gaps between the impeller and an inner wall of the flow channel, and consequently to pressure differences, which result in additional forces acting on the impeller section, further amplifying this effect.

[0008] Previously, attempts were made to compensate for this by using particularly strong materials, which resulted in high material costs. Furthermore, the sealing gaps surrounding the impeller had to be relatively large to prevent contact between the impeller and the inner wall of the flow channel.

[0009] The present invention is based on the objective of creating a side-channel pumping device of the type mentioned above which has relatively constant sealing gaps at high speeds and thus a particularly high pumping efficiency.

[0010] This problem is solved by a side-channel pumping device according to the invention, having the features of main claim 1. A side-channel pumping device according to the invention comprises a pump housing and a flow channel formed in the pump housing. The side-channel pumping device further comprises an impeller rotatably arranged in the pump housing, the impeller comprising a radially internally arranged bearing section by means of which the impeller is rotatably mounted in the pump housing about an axis of rotation. The bearing section can, for example, be non-rotatably connected to a drive shaft, which is driven, for example, by an electric drive motor.

[0011] The impeller further comprises a radially outwardly arranged impeller section with a plurality of blades, which are uniformly spaced apart from one another and distributed along the circumference. As the impeller rotates, the blades are moved through the flow channel, thereby causing the pumped medium to be conveyed through the flow channel. The flow channel extends at least axially beyond the impeller, forming a blade-free flow channel section in which a vortex-like circulation of the pumped medium occurs due to the blade movement. The pumped medium is preferably a fluid, in particular a gaseous fluid, which may also contain liquid components.

[0012] The wings extend from the wing section preferably in axial as well as radial directions.

[0013] Furthermore, the impeller includes a connecting section that links the impeller section to the bearing section. The connecting section is thus connected to the bearing section via a first connection and to the impeller section via a second connection, with the connecting section extending between the radially inner bearing section and the radially outer impeller section.

[0014] The first connection of the connecting section to the bearing section lies on a first radial plane, which is perpendicular to the axis of rotation of the impeller. The second connection of the connecting section to the impeller section lies on a second radial plane, which is also perpendicular to the axis of rotation of the impeller. Both radial planes are therefore parallel and axially spaced apart from each other. The first and second connections are thus offset from each other with respect to the axial direction, which results in a relatively small axial installation space requirement for the side-channel pump device, allowing the side-channel pump device to be relatively compact axially. The first radial plane is preferably located distally and the second radial plane proximally with respect to the interior of the side-channel pump device.

[0015] According to the invention, the connecting section is attached to the wing section off-center with respect to its axial extent. This off-center attachment causes the center of gravity of the wing section to shift such that it is axially offset from the second attachment point. This axial offset results in the centrifugal forces acting at high rotational speeds causing a deformation in the area of ​​the second attachment point that is opposite to the deformation of the connecting section around the first attachment point.

[0016] The basic principle of this opposing deformation is thus similar to the deformation of the connecting section caused by the uprighting moment. Due to the off-center connection, the wing section deforms in such a way that the center of gravity shifts axially and radially along a circular path, with the axial displacement occurring in the opposite direction to the axial displacement of the connecting section resulting from the uprighting moment. Viewed in a cross-sectional plane, the displacement is equivalent to a rotation of the center of gravity, or of the entire wing section, around the second connection, with the direction of rotation around the second connection being opposite to that of the uprighting moment. This generates a restoring moment opposite to the uprighting moment, which counteracts the rotation of the wing section caused by the uprighting moment.The eccentricity is chosen to be so large that the sealing gaps, which particularly surround the wing section, remain essentially constant even at relatively high rotational speeds of, for example, 25,000 revolutions / min.

[0017] Consequently, the design of the impeller according to the invention eliminates the need for costly, high-strength materials for the impeller. Instead, for example, cost-effective and less strong materials such as plastics can be used, making the side-channel pumping device according to the invention particularly inexpensive to manufacture while still requiring relatively little installation space. Furthermore, the sealing gaps can be significantly smaller, thereby considerably increasing the pumping efficiency and thus the overall efficiency of the side-channel pumping device according to the invention.

[0018] In a particularly advantageous embodiment of the invention, the connecting section is attached to the impeller section off-center such that a central plane, running centrally with respect to the axial extent of the impeller section and arranged parallel to the two radial planes, is located axially between the first and second radial planes. Thus, compared to a side-channel pump device according to the prior art, the impeller section is axially offset from the second attachment point on the connecting section in the direction of the first attachment point. This ensures that the restoring torque counteracts the setting torque in such a way that the sealing gaps between the impeller section and the inner wall of the flow channel remain constant even at relatively high rotational speeds.

[0019] In a further embodiment of the invention, the impeller section is designed to be mirror-symmetrical with respect to the central plane, such that the central plane constitutes a plane of symmetry. It follows that the side-channel pump device is designed as a dual-flow system, with the impeller section having a plurality of blades extending from the impeller section in both axial directions as well as in the radial direction. The flow channel is designed correspondingly and has a blade-free flow channel section on each axial side of the impeller. Additionally, the flow channel can have a further blade-free flow channel section that radially surrounds the impeller and fluidically connects the two axial flow channel sections, the overall flow channel cross-section being mirror-symmetrical with respect to the central plane.

[0020] In a further particularly preferred embodiment of the invention, the connecting section extends at least partially at an angle of attack with respect to the radial planes. The connecting section is thus at least partially conical and extends from the first connection on the first radial plane in the axial direction towards the interior of the side-channel pumping device. The angle of attack depends on the axial offset between the first and second connections, with the connecting section extending at the angle of attack connecting the two connections via a relatively short and direct path. The angle of attack should be relatively small, since the angle of attack correlates with the lifting torque, and the lifting torque increases with increasing angle of attack.

[0021] In a further embodiment of the invention, the radial extent of the portion of the connecting section extending at the angle of attack is more than 50% of the total radial extent of the connecting section. Particularly preferably, the radial extent of this portion is more than 75% of the total radial extent of the connecting section. This results in a relatively small angle of attack, so that the setting torque is relatively low. Accordingly, the eccentricity of the second connection can also be relatively small, which can be advantageous with regard to the installation space required for the side-channel pump device. The remaining part of the connecting section preferably extends exclusively in the radial direction.

[0022] In a particularly advantageous embodiment of the invention, the angle of attack is constant over the entire circumference of the impeller. The section of the connecting piece extending at the angle of attack is therefore rotationally symmetrical. This makes the impeller particularly simple and therefore cost-effective to manufacture, and it exhibits a uniform mass distribution, which is advantageous with regard to the moment of inertia, thus enabling particularly high rotational speeds.

[0023] Preferably, the angle of attack is less than 60° and particularly preferably less than 45°. The smaller the angle of attack relative to one of the radial planes, the lower the setting torque. However, the angle of attack should not be too small, as this negatively affects the compactness of the side-channel pumping device. The angle of attack should therefore be at least 10°. In a further particularly preferred embodiment of the invention, the connecting section is vane-free. Thus, the impeller has no vanes radially inside the vane section for conveying the pumped medium and therefore preferably has only a single pumping stage, which can be single- or multi-flow, making the side-channel pumping device relatively simple in design and thus cost-effective to manufacture.

[0024] Furthermore, the connecting section can have a substantially constant thickness. Here, the thickness is the axial extent of the connecting section or, in the area of ​​the section running at an angle of attack, the extent perpendicular to the leg of the angle of attack that lies outside the radial plane. A uniform thickness results in a relatively low rotating mass of the impeller and thus reduces the starting torque, the impeller's moment of inertia, and ultimately the overall mass of the side-channel pumping device. Alternatively, the connecting section can be designed to taper towards the outside, further reducing the rotating mass. Additionally, the impeller can have several through-holes in the connecting section, evenly spaced around its circumference, which further reduce the impeller's rotating mass.

[0025] Furthermore, a hydrogen recirculation blower with a side-channel pump device according to the invention is claimed. The side-channel pump device is preferably used to supply the fuel cell stack of a fuel cell unit with hydrogen. This results in specific boundary conditions for the side-channel pump device with regard to material selection, the dimensioning of the sealing gaps, and the composition of the pumping medium. Due to the possibility of dimensioning the sealing gaps of the side-channel pump device according to the invention smaller than in a side-channel pump device according to the prior art, the side-channel pump device according to the invention is particularly well suited for pumping hydrogen. In addition to hydrogen, the pumping medium to be pumped can also contain liquid components, for example, condensate or product water, which is generated as a product of the chemical reaction in the fuel cell stack.A side channel pumping device is inherently capable of efficiently pumping not only gas or liquid, but also a mixture of gas and liquid, which is why the side channel pumping device according to the invention is particularly suitable for a hydrogen recirculation blower for several reasons.

[0026] An embodiment of a side channel pumping device according to the invention is shown in the figures and is described below.

[0027] Figure 1 shows a half section of a side channel pump device according to the invention in the area of ​​the impeller.

[0028] Figure 2 shows a half-section of a conventional side-channel pumping device according to the prior art.

[0029] Figure 1 shows an embodiment of a side-channel pump device 10 according to the invention in a hydrogen recirculation blower for conveying hydrogen in a fuel cell unit. The side-channel pump device 10 comprises a multi-part pump housing 12 in which a flow channel 14 is formed. The side-channel pump device 10 further comprises a rotationally symmetrical impeller 20, which is rotatably arranged in the pump housing 12. The impeller 20 comprises a radially internally arranged hollow cylindrical bearing section 22, which is rotationally fixed to a drive shaft 15, which is rotatably mounted in the pump housing 12 about an axis of rotation R by means of bearing elements 13.

[0030] The impeller 20 further comprises a radially outwardly arranged annular impeller section 26 with a plurality of vanes 27, 28. The vanes 27, 28 are spaced apart from each other and evenly distributed around the circumference of the impeller 20, extending from a disk-shaped central web 261 of the impeller section 26 on both sides in the axial and radial directions, wherein a first group of vanes 27 extends axially away from the interior of the side-channel pumping device 10 and a second group of vanes 28 extends axially towards the interior of the side-channel pumping device 10.

[0031] The vanes 27, 28 extend axially over the entire axial extent L of the vane section 26. The two vane groups are separated from each other by the central web 261 of the vane section 26, which is located centrally with respect to the axial extent L of the vane section 26. The vane section 26 is thus mirror-symmetrical, with the plane of symmetry being a median plane M located centrally within the vane section 26 with respect to its axial extent L and parallel to the radial planes E1, E2. A fluid chamber is formed between each pair of adjacent vanes 27, 28, which is open axially and radially to the outside. The side-channel pumping device 10 is therefore designed as a dual-flow system.

[0032] Accordingly, the annular flow channel 14 has an annular, bladeless flow channel section 141, 142 with a semicircular cross-section on both axial sides of the blades 27, 28. The two axial flow channel sections 141, 142 are fluidically connected along the radial outer surface of the blade section 26 by a radial flow channel section 143, which radially surrounds the impeller 20. The flow channel 14 extends from an inlet (not shown) to an outlet (not shown).

[0033] The rotational movement of the impeller 20 and the resulting movement of the vanes 27,28 through the flow channel 14 conveys the pump medium, for example a hydrogen-liquid mixture, from the inlet to the outlet, whereby swirling circulation flows form, particularly in the vane-free axial flow sections 141,142, which cause a pressure increase in the flow channel towards the outlet and thus convey the pump medium.

[0034] The wing section 26 is connected to the bearing section 22 by means of a disk-like connecting section 24, which extends between the bearing section 22 and the wing section 26 essentially in a radial direction. The connecting section 24 is connected to the bearing section 22 via a first connection 23, the first connection 23 being located on a first radial plane El, which is arranged perpendicular to the axis of rotation R.

[0035] The connecting section 24 is connected to the wing section 26 via a second connection 25, the second connection 25 being arranged on a second radial plane E2, which is parallel and axially spaced from the first radial plane El. The two connections 23, 25 are therefore offset from each other with respect to the axial direction, causing the connecting section 24 to extend in both the radial and axial directions. In a subsection 25, the connecting section 24 extends with respect to the radial planes E1, E2 at an angle of attack α of 30° towards the interior of the side-channel pumping device 10. The radial extent E of the subsection 25 is approximately 80% of the total radial extent G of the

[0036] Connection section 24. The thickness D of connection section 24 is essentially constant, with connection section 24 being designed without wings.

[0037] At relatively high rotational speeds of the impeller 20, for example 25,000 rpm, the centrifugal force acting on the connecting section 24 and the impeller section 26 causes deformation, particularly of the connecting section 24. The axial displacement between the first connection 23 and the second connection 25, or the axial displacement between the first connection 23 and the center of gravity of the impeller section 26, deforms the connecting section 24 such that the second connection 25 displaces both radially outwards and axially in the direction of the first radial plane El relative to the first connection. The rotating mass formed by the connecting section 24 and the impeller section 26 thus causes a righting moment Ml about the connection 23, such that the axial and radial displacement of the second connection 25 follows a circular path around the first connection 23.

[0038] In a side-channel pump device 10' according to the prior art, as shown in Figure 2, this results in the wing section 26' being displaced along the circular path K together with the second connection 25', which in particular leads to a non-uniformity of the radial sealing gap 21' between the wing section 26' and the inner wall of the flow channel 14'. The displacement of the wing section 26' is illustrated by the dashed lines, which represent the undeformed state.

[0039] To counteract this deformation, the wing section 26 of the inventive side-channel pump device 10 of Figure 1 is connected off-center to the connecting section 24, such that the median plane M lies axially between the first radial plane El and the second radial plane E2. The center of gravity S of the wing section 26 is therefore located, with respect to the axial direction, between the first connection 23 and the second connection 25.

[0040] The shift in the center of gravity causes a deformation at the second connection 25, which in turn causes a displacement of the center of gravity S in the radial and axial directions, with the center of gravity S being displaced radially outwards and axially in the direction of the second connection 25. The rotating mass of the wing section 26 thereby causes a restoring moment M2 about the second connection 25, which opposes the righting moment M1, whereby, in particular, the axial component of the deformation of the wing section 26 opposes the axial component of the deformation of the connecting section 24. The respective axial components of the deformations of the wing section 26 and the connecting section 24 thus cancel each other out, so that the off-center connection of the wing section 26 compensates for the adverse effects of the righting moment M1.Consequently, unevenness, especially of the radial sealing gap 21, is avoided or at least significantly reduced.

Claims

PATENT CLAIMS 1. Side channel pumping device (10), comprising: - a pump housing (12), - a flow channel (14) formed in the pump housing (12), and - a paddle wheel (20) rotatably arranged in the pump housing (12), the paddle wheel (20) comprising: • a radially internally arranged bearing section (22) by which the impeller (20) is rotatably mounted in the pump housing (12) about an axis of rotation (R), • a radially outwardly arranged wing section (26) with a plurality of wings (27, 28), and • a connecting section (24) that connects the wing section (26) to the bearing section (22), wherein a first connection (23) of the connecting section (24) to the bearing section (22) lies on a first radial plane (El), and a second connection (25) of the connecting section (24) to the wing section (26) lies on a second radial plane (E2), and the two radial planes (E1,E2) are arranged parallel and axially spaced apart from each other, characterized in that the connecting section (24) is connected to the wing section (26) off-center with respect to an axial extent (L) of the wing section (26).

2. Side channel pumping device (10) according to claim 1, wherein the connecting section (24) is connected to the wing section (26) in such an off-center manner that a central median plane (M) extending with respect to the axial extent of the wing section (26), parallel to is arranged to the two radial planes (E1,E2), axially between the first radial plane (El) and the second radial plane (E2).

3. Side channel pump device (10) according to claim 2, wherein the wing section (26) is designed in a mirror-symmetrical manner with respect to the median plane (M), such that the median plane (M) represents a plane of symmetry.

4. Side channel pumping device (10) according to one of the preceding claims, wherein the connecting section (24) extends at least partially at an angle of attack (a) with respect to the radial planes (E1,E2), 5. Side channel pump device (10) according to claim 4, wherein the radial extent (E) of the partial section (241) of the connecting section (24) extending at the angle of attack (a) is more than 50%, and particularly preferably more than 75% of the total radial extent (G) of the connecting section (24).

6. Side channel pump device (10) according to claim 4 or 5, wherein the angle of attack (a) is constant over the entire circumference of the impeller (20).

7. Side channel pumping device (10) according to one of claims 4-6, wherein the angle of attack (a) is less than 60° and particularly preferably less than 45°.

8. Side channel pumping device (10) according to one of the preceding claims, wherein the connecting section (24) is designed without wings.

9. Hydrogen recirculation blower with a side channel Pump device (10) according to one of the preceding claims. 5

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