Centrifugal pump

Abstract

A centrifugal pump (10) has a pump housing (12) enclosing a pump chamber (14, 30, 34), and a pump impeller (16) arranged within the pump chamber (14, 30, 34) and rotatably mounted about a longitudinal axis (17) relative to the pump housing (12). The pump housing (12) includes a pump inlet (36), a pump outlet (38), and an annular channel (30, 34) that partially circumferentially surrounds the longitudinal axis (17) as part of the pump chamber (14, 30, 34). To achieve, in particular, higher efficiency, the pump inlet (36) is radially internal to the pump outlet (38), and a baffle (48) is arranged radially between the pump inlet (36) and the pump outlet (38). Furthermore, the pump impeller (16) has a peripheral ring (50) of blades (52) and at least one through channel (56) which extends radially inwards across the partition area (48) to radially outwards into the annular channel (30, 34).

Description

BACKGROUND OF THE INVENTION 1. Field of the invention

[0001] The invention relates to a centrifugal pump and an impeller for such a pump. 2. Description of the state of the art

[0002] Centrifugal pumps belong to the group of flow pumps and, unlike positive displacement pumps, which use dynamic forces to move a medium by increasing and decreasing the pump volume. The medium flows through the pump without the need for valves or flaps.

[0003] Various centrifugal pumps are known from the prior art. For example, radial centrifugal pumps utilize not only the tangential acceleration of the medium but also the centrifugal force occurring in the radial flow.

[0004] Another type of centrifugal pump is the peripheral impeller pump, in which the medium is conveyed via a flow in a peripheral annular channel. The peripheral impeller pump has a disc-shaped impeller whose periphery is equipped with straight blades oriented radially and transversely to the direction of rotation. In the annular channel, that is, the peripheral space of the casing between the casing wall and the impeller intended for the medium, the kinetic energy of the drive shaft is transferred from the blades to the medium, setting the medium in motion. In conjunction with a constricted segment of the annular channel, this creates a pressure differential to convey the medium.

[0005] The various centrifugal pump concepts have different pumping characteristics, such as efficiency, pumping behavior, maximum pressures, volume flows, etc.

[0006] For example, a centrifugal pump is usually more efficient than a peripheral pump due to its use of centrifugal forces. On the other hand, a peripheral pump has better suction characteristics and can pump larger quantities of gas in the medium. In particular, a peripheral pump has better suction characteristics with regard to cavitation, i.e., the formation and collapse of local vapor bubbles in the pumped liquid medium.

[0007] Attempts have therefore already been made to combine the two pump types by connecting them in series. For example, pumps are known in which several peripheral impeller stages are connected upstream of a separate radial impeller. Pumps with the reverse arrangement are also known. Even pumps in which the various impellers operating in series are driven by one and the same shaft are known.

[0008] In all these concepts, the entire volume flow of the medium first passes through one impeller, for example the radial impeller, and then the other impeller, for example the peripheral impeller. SUMMARY OF THE INVENTION

[0009] Against this background, the object of the present invention is to provide an improved centrifugal pump. In particular, the centrifugal pump according to the invention is to have one or more improved pumping characteristics.

[0010] According to the invention, this problem is solved by a centrifugal pump, with a) a pump housing enclosing a pump chamber, b) a pump impeller arranged in the pump chamber and rotatably mounted about a longitudinal axis relative to the pump housing, c) wherein the pump housing has a pump inlet, a pump outlet and an annular channel partially circumferential about the longitudinal axis as part of the pump chamber.

[0011] According to the invention, it is provided that d) the pump inlet is arranged radially inside the pump outlet and a bulkhead is arranged radially between the pump inlet and the pump outlet, and e) the pump impeller has a peripheral ring of blades and at least one through-channel extending radially inside across the bulkhead to radially outside into the annular channel.

[0012] The inventor recognized that the operating principles of a peripheral pump impeller and a radial pump impeller could be combined in a single, shared pump impeller. This results in the two operating principles working in parallel instead of in series, unlike in the prior art.

[0013] Crucially, the pump impeller has, on the one hand, a peripheral ring of blades, similar to a peripheral pump impeller, which generates a flow in the annular channel. On the other hand, the pump impeller according to the invention also has at least one through-channel, which leads radially outwards from the radially inner pump inlet, similar to a radial pump impeller.

[0014] The passage channel does not have to run along the radius, but it must extend from the inside to the outside with a radial component.

[0015] The bulkhead of the centrifugal pump serves to separate the annular channel from the pump inlet. This is usually achieved by a small gap between the pump housing and the impeller. This allows the impeller to rotate freely. However, a labyrinth seal and / or an axial seal can also be used.

[0016] In the pump impeller according to the invention, the medium to be pumped enters the annular channel through the through-channel. There, the medium is flung outwards by centrifugal force, similar to a radial pump impeller. This increases the efficiency of the centrifugal pump according to the invention compared to a purely peripheral impeller pump.

[0017] Compared to a standard peripheral pump, the centrifugal pump according to the invention has somewhat higher flow rates and a lower delivery head, i.e., lower pressures. The centrifugal pump according to the invention therefore has a flatter characteristic curve compared to peripheral pumps. Furthermore, the centrifugal pump according to the invention has improved self-priming capability compared to a peripheral pump.

[0018] Preferably, the through-channel is designed to lead away from the radially inner pump inlet at an angle of approximately 5° to 90°, preferably between approximately 35° and 90°, to the radius of the pump impeller, in particular tangentially.

[0019] This has advantages with regard to the centrifugal forces that occur, the flow guidance and the pressure profile in the passage channel.

[0020] Preferably, the through-channel is designed to run outwards along a curve in the plane of rotation of the pump impeller.

[0021] A curved profile allows the fluid's movement to be optimally adapted to centrifugal forces. The flow channel can thus exit the pump inlet at one of the aforementioned angles, and this angle can then change along the length of the flow channel.

[0022] Preferably, the through-channel is a channel with a closed cross-section, which is incorporated into the pump impeller.

[0023] The through-channel is then located entirely inside the essentially disc-shaped pump impeller. Such a through-channel can be produced as a bore from the outer circumferential wall of the pump impeller inwards into the area of ​​the pump inlet.

[0024] However, a through-channel is also conceivable, whose cross-section is open on one or both sides and bounded by the pump housing. This allows the through-channel to be integrated into the pump impeller, for example, as a groove. This enables virtually any desired through-channel shape. With a closed cross-section, the pump impeller would have to be manufactured using an additive manufacturing process or produced in multiple parts to allow for any desired through-channel shape.

[0025] Preferably, the passage channel has a clear cross-section that tapers or widens from the inside to the outside along the passage channel.

[0026] This allows for the adaptation to changing pressure conditions along the passageway.

[0027] Preferably, the through channel opens axially centrally into the annular channel.

[0028] Due to the central position of the outlet, the medium flowing from the through-channel integrates more effectively into the peripheral circulation flow created by the peripheral ring of blades. The similar flow angle of the medium between the blade outlet and the through-channel reduces losses.

[0029] Preferably, the blades of the peripheral ring are formed by recesses.

[0030] This allows for simple manufacturing. The recesses can be single- or double-sided grooves on the pump impeller, which are machined, for example, by milling. The recesses can have a cross-section that increases axially from the radial inside to the radial outside. This facilitates the formation of a peripheral helical flow.

[0031] Alternatively, the blades can be attached to the peripheral ring, for example, as attached wings.

[0032] The blades can be arranged axially opposite or offset from each other with respect to the plane of rotation of the pump impeller.

[0033] Preferably, the radially internal pump inlet opens into a distribution channel that rotates around the longitudinal axis, with which the at least one through-channel of the pump impeller is fluidically connected.

[0034] This improves the flow of the medium to multiple channels. The distribution channel preferably runs completely around its longitudinal axis, but this is not mandatory. For example, sections spanning multiple passages, separated by partitions, are also conceivable.

[0035] Preferably, a backflow preventer element can be arranged in the distribution channel, which isolates the distribution channel in a circular segment from the at least one through channel.

[0036] At low flow rates and higher pressure build-up, fluid flows from the pressure-side end of the annular channel back through the passages to the inlet. With tangentially offset bores, this backflow leads directly into the inlet of the bores located on the suction side of the annular channel.

[0037] At high flow rates and lower pressure build-up, this backflow occurs less or not at all. The strength of the backflow generally decreases with increasing flow rate. Furthermore, the strength of the backflow depends strongly on the geometry, in addition to the operating point. The larger the total flow area (number of passages x cross-sectional area of ​​a single passage), the greater the backflow at low flow rates. However, the maximum possible flow rate also increases with the total flow area.

[0038] The backflow significantly reduces the maximum achievable delivery head.

[0039] The solution to this problem lies in sealing off the inlet openings of the passages in the distribution channel using a backflow preventer. Since the medium cannot flow back through the passages, the pressure increases from the pump outlet. At the same time, however, the maximum achievable flow rate decreases compared to a pump without a backflow preventer.

[0040] The backflow preventer is positioned approximately within the angle of the pump outlet. More precisely, the angle within which the backflow preventer is positioned depends on the inclination and / or curvature of the passage(s). For steeply inclined or curved passages, the angle shifts. The backflow preventer is primarily intended to interrupt the flow to the inlets of those passages whose outlets are located within the angle of the pump outlet at that moment.

[0041] The non-return element can be connected to the pump housing, thus creating a stationary position opposite the pump impeller.

[0042] The length of the circumference covered by the backflow preventer element determines the magnitude of the change compared to the pump without a preventer.

[0043] The backflow preventer also has a significant influence on the minimum pressure in the flow channels, i.e., the pump's NPSH values. It is preferable that different backflow preventers can be arranged, differing in the angular range within which the at least one flow channel in the distribution channel is sealed off.

[0044] This allows the characteristic curve to be adjusted without changing the rotational speed by replacing the non-return valve element.

[0045] The backflow preventer can be attached to the pump housing, for example, with screws, and then easily replaced with another backflow preventer that interrupts a different angular range. Alternatively, it can simply be inserted using a positive locking mechanism.

[0046] Since it is a simple component, different backflow preventer element variants allow an otherwise identical pump to achieve different performance curves cost-effectively.

[0047] Preferably, a second pump inlet is arranged on the annular channel, particularly following an interrupter segment section in the direction of rotation.

[0048] Since a strong vacuum is created at the beginning of the annular channel, as with a purely peripheral impeller pump, additional suction ports can be attached to the circumference. This allows the mixing of two media by supplying different media to the two pump inlets.

[0049] Furthermore, a higher efficiency can be achieved due to the increased flow via the second pump inlet at the beginning of the ring channel.

[0050] The centrifugal pump can also pump a higher proportion of gas in the medium at the second pump inlet than at the first pump inlet.

[0051] The number and diameter of the passages influence the possible number, position, and size of the blades that can be attached to the pump impeller. In addition to reduced backflow, fewer passages also allow for more grooves, thus increasing the achievable delivery head.

[0052] Due to the still relatively high pressure build-up in the pump impeller, a magnetic coupling with a containment shell is well suited as a drive. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawings. In these drawings: Figure 1 shows a longitudinal section through a centrifugal pump with an impeller; Figure 2 shows a perspective view of the impeller; Figure 3 shows a cross-section on the axial plane of the impeller with a gray-shaded pressure profile; Figure 4 shows a section through an annular channel with a gray-shaded velocity profile at the circumferential position of a blade recess; Figure 5 shows a section through an annular channel with a gray-shaded velocity profile at the circumferential position of the opening of a through-channel; Figure 6 shows a cross-section on the axial plane of the impeller with a gray-shaded pressure profile of an embodiment with a non-return valve element; Figure 7 shows a perspective view of the non-return valve element; Figure 8 shows a QH diagram with characteristic curves of various centrifugal pump types;Figure 9 shows a cross-section on the axial plane of the pump impeller with a gray-shaded pressure profile from an embodiment with a second pump inlet for mixing media; DESCRIPTION OF PREFERRED EXAMPLES

[0054] Figure 1 shows a centrifugal pump 10 with a pump housing 12 that encloses a pump chamber 14 in which a pump impeller 16 rotates around a longitudinal axis 17.

[0055] In the present embodiment, the centrifugal pump 10 comprises a pump part 18 and a drive part 20.

[0056] The drive unit 20 has a magnetic coupling 22 located inside the pump housing 12, which is connected to the pump impeller 16 via a drive shaft 24. Outside the pump housing 12, the magnetic coupling 22 is enclosed by a magnetic coupling drive unit 26, which in turn is driven by a drive motor (not shown), usually an electric motor.

[0057] For the present invention, however, the details of the drive part 20 are not important to a first approximation and can be designed individually.

[0058] The pump chamber 14 is essentially disc-shaped to accommodate the pump impeller 16. Furthermore, the pump chamber 14 has an annular channel 30, which, except for a smaller interrupter segment section 32 (see figure 32), Fig. 3 (top left) runs around the circumference. The annular channel 30 has a radial cross-section that is wider than that of the pump impeller 16 rotating within it. This leaves a clear radial cross-section 34 around the pump impeller 16 in both radial and axial directions.

[0059] The pump housing 14 also has a pump inlet 36 and a pump outlet 38.

[0060] Again Fig. 1As can be seen, the pump inlet 36 leads axially into the center of the pump chamber 14. The pump inlet 36 leads from the side opposite the drive part 20 towards the pump impeller 16. However, it is also conceivable that the pump inlet 36 could be arranged only near the longitudinal axis 17, for example, to support the drive shaft 24 on both sides of the pump impeller 16.

[0061] It is also conceivable to have a radially positioned pump inlet 36, offset axially to the annular channel 30, from which the medium to be pumped is guided from radially outside to inside at the plane of the annular channel 30 to the central area of ​​the pump impeller 16.

[0062] The pump outlet 38, on the other hand, is arranged radially on the outside and leads away from the annular channel 30. Fig. 1 The pump outlet 38 is designed as a radially and vertically projecting nozzle. However, it can also lead out of the annular channel 30 at an angle, in particular tangentially.

[0063] The pump outlet 38 also represents the end of the annular channel 30, since in the circumferential direction after the pump outlet 38 the interrupter segment section 32 interrupts the extended annular channel 30 as a pressure barrier.

[0064] The pump impeller 16 according to the invention is arranged in the pump chamber 14, which is located in the Fig. 2 is shown in perspective.

[0065] The pump impeller 16 is basically a combination of a radial pump impeller and a peripheral impeller.

[0066] The pump impeller 16 initially has a round disc shape and features a radially internal shaft receptacle 40 with a drive groove 42. Naturally, various power transmission means, including a direct drive of the pump impeller 16, are conceivable.

[0067] Following the shaft mount 40, a fully circumferential distribution channel 44 extends radially, through which the pump impeller 16 communicates with the pump inlet 36 when installed. In the simplest case, the distribution channel 44 can be designed as a circumferential groove open on one side, as shown here.

[0068] The distribution channel 44 is bounded radially outwards by a wall 46. Here, the wall 46 projects slightly in the axial direction and cooperates with the pump housing 12 to form a barrier 48 in its further radial course against a peripheral ring 50 of the pump impeller 16 (see also Fig. 1 The protruding wall 46 and the pump housing 12 thus form a labyrinth seal.

[0069] Additionally or alternatively, circumferential seals can also be arranged between the pump housing 12 and the pump impeller 16 in the compartmentation area 48. Crucially, the distribution channel 44 must be sufficiently sealed off from the peripheral ring 50, which is located in the circumferential annular channel 30 of the pump chamber 14, to achieve the desired pressure differentials.

[0070] The peripheral ring 50 of the pump impeller 16 has several blades 52 distributed along its circumference. These blades 52 are formed by substantially radially extending recesses 54 in the pump impeller 16. The depth of the recesses 54 decreases in the radial direction inwards towards the bulkhead area 48.

[0071] Furthermore, the pump impeller 16 shown here has blades 52 projecting on both sides of the disc shape. These are located opposite the blades 52 on the other side of the disc. However, blades 52 offset from each other in the circumferential direction or blades 52 extending through the disc shape are also conceivable.

[0072] Finally, the pump impeller 16 has several through-channels 56 which, in the embodiment shown here, extend inside the pump impeller 16 from the distribution channel 44 across the partition area 48 to the radial outside into the annular channel 30 of the pump chamber 14.

[0073] The through channels 56 terminate in outlets 58, which are arranged in segment sections without blades 52 on the circumferential wall 60 of the peripheral ring 50.

[0074] How to use Fig. 3As can be seen, the through-channels 56 do not extend radially perpendicularly outwards. Instead, the through-channels extend obliquely within the plane of rotation of the pump impeller 16, in particular approximately tangentially outwards from the distribution channel 44.

[0075] The centrifugal pump 10 operates as follows: As in Fig. 3 As can be seen, the pump impeller 16 is driven rotating relative to the pump housing 12 (in Fig.3 counterclockwise).

[0076] The medium to be pumped enters the distribution chamber 44 from the pump inlet 36, which is located in front of the plane of the drawing. Due to the rotational movement and the associated centrifugal forces, the medium is then forced radially outwards through the passage channels 56 into the annular space 30.

[0077] In the annular space 30, the medium is then carried along by the blades 52 moving along the circumference. This is evident from the velocity profile of the Fig. 4As can be seen, flow vortices form in the recesses 54 between the blades 52, which impart a circumferential velocity to the medium. In three dimensions, the medium performs a kind of screw motion along the peripheral rim 50 of the pump impeller 16.

[0078] As from Fig. 5 As can be seen, the medium at the opening 58 of the through channels 56 already has an imprinted velocity component in the circumferential direction due to the rotation in the through channel 56, so that the exiting medium integrates into the movement of the screw flow present in the annular channel 30.

[0079] The medium is thus moved radially outwards and circumferentially along the annular channel 30 by the rotating pump impeller 16. Overall, the pressure in the medium increases, firstly, from radially inwards to radially outwards due to centrifugal forces. Secondly, the pressure in the medium increases along the annular space 30 from the interrupter segment section 32 to the pump outlet 38.

[0080] This creates a suction effect in the distribution chamber 44, which draws in the medium at the pump inlet 36.

[0081] The suction effect between the beginning of the annular channel 30 and the distribution channel 44 is evident in the pressure profile along the through channel 56. This is located after the interrupter segment section 32 (in Fig. 3(at approximately 10 o'clock) the pressure decreases from the inside out. At the end of the annular channel 30, however, the pressure curve along the through channel 56 increases. This is a fundamental difference compared to conventional centrifugal centrifugal pumps, in which the pressure curve increases from the inside out over the entire circumference.

[0082] Fig. 6 Figure 1 shows a slightly modified embodiment of the invention in which a backflow preventer element 62 is arranged in the distribution channel 44, which is in Fig. 7 is shown in perspective.

[0083] The backflow preventer element 62 has an approximately crescent-shaped projection 64, which is integrally formed on an annular flange 66 and extends circumferentially over an angular range. This angular range can be between approximately 20° and approximately 220°, preferably between approximately 60° and approximately 180°, and particularly around 100°.

[0084] The isolated angle range depends on the desired behavior of the centrifugal pump 10. In principle, the angle range can also be greater than 220°. However, this would probably have mostly negative effects.

[0085] The flange 66 has two screw holes 68, which allow the non-return valve element 62 to be mounted on the pump housing 12 above the distribution channel 44. As a result, the non-return valve element 62, when mounted, projects into the distribution channel 44 with its projection and remains stationary relative to the rotating pump impeller 16.

[0086] The backflow preventer element 62 can also be incorporated directly into the pump housing 12, but then it can no longer be replaced.

[0087] During operation of the centrifugal pump 10, the non-return valve element 62 prevents the medium from being forced back into the distribution channel 44 from the radial outside to the radial inside of the through-channels 56 due to the high pressure in the annular channel 30 near the pump outlet 38. Depending on the inclination of the through-channels 56, the non-return valve element 62 will therefore block the inlet openings of the through-channels 56 in the distribution channel 44 approximately in the angular range of the interrupter segment section 32 of the annular space 30.

[0088] The non-return valve element 62 thus makes it possible to increase the maximum pressure of the centrifugal pump 38.

[0089] Depending on the application, non-return valve elements 62 can be inserted into the pump housing 12, blocking the inlet openings of the through channels 56 over different angular ranges. The pumping behavior of the centrifugal pump 10 can thus be adjusted by simply exchanging different non-return valve elements 62.

[0090] The advantageous pumping behavior of the centrifugal pump 10 according to the invention is based on Figure 8 visible.

[0091] In the Figure 8 The pressure-flow rate diagram (also called QH diagram) shows four pump characteristic curves for the different pump types.

[0092] Pump characteristic curve 70 is typical for a state-of-the-art peripheral impeller pump. It shows a high maximum pressure, which, however, drops rapidly with increasing flow rate.

[0093] Pump characteristic curve 72 is characteristic of a state-of-the-art centrifugal pump. It shows a relatively flat, slightly curved curve, which overall exhibits a rather low maximum pressure.

[0094] The pump characteristic curve 74 corresponds to the centrifugal pump 10 according to the invention, whose pumping behavior corresponds to a mixture of centrifugal and peripheral wheel pump.

[0095] The pump characteristic curve 76 corresponds to the centrifugal pump 10 according to the invention with an inserted non-return element 62. This allows the centrifugal pump 10 to achieve a higher maximum pressure, but at higher flow rates the pressure is slightly below the characteristic curve 74 of the centrifugal pump 10 without the non-return element 62.

[0096] Finally, in Figure 9 Another embodiment of the centrifugal pump 10 is shown.

[0097] This centrifugal pump 10 differs from the previous embodiments only in that a second pump inlet 80 is provided on the annular channel 30 near the interrupter segment section 32.

[0098] As can be seen from the dark gray shading, a vacuum is created at the beginning of the annular channel 30 due to the peripheral impeller pump action. The centrifugal pump according to the invention can therefore be supplied with different media (* and + symbols) via both the first pump inlet 36, which feeds the internal distribution channel 44, and the second pump inlet 80 on the annular channel 30. The centrifugal pump 10 can then be used to mix the two media together.

[0099] Since the through channels 56 each feed into the helical ring flow at the peripheral ring 50 and relatively strong turbulence occurs there, a high degree of mixing is achieved.

Claims

1. Centrifugal pump (10) with a) a pump housing (12) enclosing a pump chamber (14, 30, 34), b) a pump impeller (16) arranged in the pump chamber (14, 30, 34) and mounted so as to be rotatable about a longitudinal axis (17) relative to the pump housing (12), c) wherein the pump housing (12) has - a pump inlet (36), - a pump outlet (38) and - an annular channel (30, 34) partially encircling the longitudinal axis (17) as part of the pump chamber (14, 30, 34), characterized in that d) the pump inlet (36) is arranged radially inwardly opposite the pump outlet (38) and a partition area (48) is arranged radially between the pump inlet (36) and the pump outlet (38), and that e) the pump impeller (16) - has a peripheral ring (50) of blades (52) and - at least one through-channel (56) which extends from radially inward over the partition area (48) to radially outward into the annular channel (30, 34).

2. Centrifugal pump according to claim 1, characterized in that the through-channel (56) leads away from the radially inner pump inlet (36) at an angle of between approximately 5° and 90°, preferably between approximately 35° and 90°, to the radius of the pump impeller, to the radius, in particular tangentially.

3. Centrifugal pump according to one of the preceding claims, characterized in that the through-channel (56) runs outwards along a curve in the plane of rotation of the pump impeller (16).

4. Centrifugal pump according to one of the preceding claims, characterized in that the through-channel (56) is a channel with a closed cross-section which is incorporated into the pump impeller (16).

5. Centrifugal pump according to one of the preceding claims, characterized in that the through-channel (56) has a clear cross-section which tapers or widens along the through-channel (56) from the inside to the outside.

6. Centrifugal pump according to one of the preceding claims, characterized in thatthe blades (52) of the peripheral ring (50) are formed by recesses (54).

7. Centrifugal pump according to one of the preceding claims, characterized in that the radially inner pump inlet (36) opens into a distribution channel (44) which runs around the longitudinal axis (17) and with which the at least one through-channel (56) of the pump impeller (16) is fluidically connected.

8. Centrifugal pump according to claim 7, characterized in that a backflow interrupter element (62, 64, 66, 68) can be arranged in the distribution channel (44), which seals off the distribution channel (44) in a circular segment from the at least one through-channel (56).

9. Centrifugal pump according to claim 8, characterized in thatas a backflow interrupter element (62, 64, 66, 68) different backflow interrupter elements (62, 64, 66, 68) can be arranged, which differ with regard to the angular range in which the at least one through-channel (56) in the distribution channel (44) is sealed off.

10. Centrifugal pump according to one of the preceding claims, characterized in that a second pump inlet (80) is arranged on the annular channel (30), in particular following an interrupter segment section (32) in the direction of rotation.

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