EP3184823B1 - Centrifugal pump - Google Patents

Description

The invention relates to a centrifugal pump.

Centrifugal pumps are usually driven by electric drive motors. The control of these drive motors and, consequently, the control of the centrifugal pump can be done the better, the more knowledge about the possibly changing during operation operating state of the centrifugal pump. In this respect, it is expedient to continuously detect certain state parameters in a centrifugal pump during their operation in order to allow them to flow into the control of the drive motor. These flow parameters also include the flow rate through the centrifugal pump.

EP 2 072 829 A1 discloses a submersible pump with a arranged on the output side of the submersible pump pump impeller whose speed is detected to determine the flow rate.

It is an object of the invention to improve a centrifugal pump with a device for detecting the flow rate to the effect that the flow rate can be detected with relatively low cost construction with high accuracy.

This object is achieved by a centrifugal pump having the features specified in claim 1. Advantageous developments of this centrifugal pump will become apparent from the dependent claims, the following description and the drawings. Here you can the features specified in the dependent claims advantageous in the specified combination, but also, as far as technically feasible, contribute by themselves or in another combination to the embodiment of the invention.

The centrifugal pump according to the invention is preferably a multi-stage pump. This means that the centrifugal pump preferably has more than one pump stage, which is equipped with an impeller rotatably mounted on a pump shaft. In the usual way, the pump stage also has at least one stator to provide the output side of the pump stage a possible twist-free flow available. Preferably, the centrifugal pump is designed as a multi-stage centrifugal pump, in which in the direction of the pump shaft a plurality of mutually flow-connected pump stages, each with an impeller and at least one stator are provided.

In addition to the pump stage or the pump stages, the centrifugal pump has a turbine wheel. This turbine wheel is arranged on the pump shaft without movement coupling with the pump shaft. Here, the pump shaft passes through a centrally formed on the turbine wheel hub, wherein the pump shaft can rotate relative to the surrounding turbine and / or vice versa. The turbine wheel forms a transmitter of a flow measuring device, with which the flow rate through the centrifugal pump or the flow velocity of the funded by the centrifugal pump fluid is detected within the centrifugal pump. For this purpose, the turbine wheel in principle has an embodiment in which the delivery flow to the turbine wheel exerts a torque about its central axis. As a transmitter, the turbine generates a proportional to the flow measurement signal, which is received by a signal receiver of the flow measuring device and then, for example, in the control of a drive motor for driving the centrifugal pump can flow. The measurement signal generated by the turbine wheel can be the torque exerted by the delivery flow on the turbine wheel or a rotational speed of a rotational movement of the turbine wheel caused by the torque, as described below will be discussed in more detail with preferred developments of the centrifugal pump according to the invention.

Although the turbine wheel is not structurally coupled to the pump shaft, the bearing friction of a radial bearing optionally located between the pump shaft and the turbine wheel and / or solids entering a clearance between the pump shaft and the turbine wheel may cause frictional engagement between the pump shaft and the turbine wheel. Such a frictional engagement causes considerable measurement inaccuracies in the flow measurement, since it causes the actual torque acting on the turbine wheel of the applied torque from the flow to the turbine wheel, which forms the basis for determining the flow rate directly or indirectly, especially at small Speeds of the pump shaft and concomitantly with low flow rate of the centrifugal pump differs.

In order to counteract these measurement inaccuracies in the flow measurement, it is essential to the invention that the torque exerted by the delivery flow on the turbine wheel is directed in opposite direction to a torque exerted on the impeller of the at least one pump stage via the pump shaft. That is, when the pump shaft and the thus fixed impeller of the at least one pump stage in the direction of flow of the centrifugal pump are driven clockwise, the blading of the turbine wheel is such that the turbine wheel is subjected to left-handed force from the flow through the centrifugal pump. In the opposite case, when the pump shaft and the impeller of the at least one pump stage are driven counter-clockwise in the flow direction of the centrifugal pump, the blading of the turbine wheel is typically designed so that the turbine wheel is subjected to dextrorotatory force from the flow through the centrifugal pump. It has been shown that the torque exerted by the flow on the turbine wheel torque in this embodiment, even at a relatively low flow rate of the centrifugal pump forms a largely proportional to the flow rate size, so that the flow rate can be determined with sufficient accuracy.

According to a first preferred embodiment of the centrifugal pump according to the invention, the turbine wheel is arranged downstream of a last pump stage of the centrifugal pump. Accordingly, the turbine wheel is arranged in a centrifugal pump with only one pump stage in the flow direction of this pump stage behind the pump stage and arranged at a multi-stage centrifugal pump in the flow direction of the pump stages behind the furthest from the fluid inlet of the pump pump stage. This measure also aims to increase the measurement accuracy in the flow measurement, since the turbine wheel is in this way as far as possible from occurring possibly in the region of the fluid inlet of the centrifugal pump flow and pressure changes. Incidentally, the pressure chamber downstream of the last pump stage usually provides enough space for the arrangement of the turbine wheel, so that the arrangement of the turbine wheel does not affect the overall size of the centrifugal pump.

As has already been noted, a rotational speed of a rotational movement of the turbine wheel caused by the delivery flow through the centrifugal pump can be used as the measurement signal generated by the turbine wheel. This allows a further advantageous embodiment of the centrifugal pump according to the invention, in which the turbine wheel is rotatably mounted on the pump shaft. The turbine wheel is thus preferably rotatable by the flow through the centrifugal pump relative to the pump shaft and in the opposite direction of rotation to the direction of rotation of the pump shaft.

In connection with this embodiment, at least one signal means, which moves relative to a signal receiver of a measuring transducer of the flow measuring device, is expediently arranged on the turbine wheel. With regard to the largest possible measurement value, it proves to be advantageous if the at least one signal means is arranged on a largest outer circumference of the turbine wheel. In the case of a turbine wheel, this largest outer circumference is generally formed by an outer ring surrounding the outer circumference of the blades of the turbine wheel, and accordingly it is particularly favorable to arrange the at least one signal means on the outer circumference of this outer ring.

In development of this embodiment, it is preferably provided that at least three signal means are arranged on the outer circumference of the turbine wheel, which have a different distance from one another in the direction of rotation of the turbine wheel. The at least three differently spaced in the direction of rotation of the turbine wheel signal means allow in conjunction with a corresponding evaluation, in addition to the rotational speed and to determine the direction of rotation of the turbine wheel. Although this direction of rotation of the turbine wheel should normally be directed counter to the direction of rotation of the pump shaft, under certain circumstances, for example due to the penetration of solid particles into the space between the hub of the turbine wheel and the pump shaft, due to a consequent jamming of the turbine wheel with the pump shaft , coincide with the direction of rotation of the pump shaft. Incidentally, the rotational direction of the turbine wheel always coincides with the rotational direction of the pump shaft due to the friction between the turbine wheel and the pump shaft when the delivery rate of the pump is below a certain value. In this case, the flow measuring device is not functional. However, such a non-operational capability of the flow measuring device can due to the According to the invention possible detection of a wrong direction of rotation of the turbine directly detected and subsequently corrected.

In a turbine wheel rotatably mounted relative to the pump shaft, the rotational speed and direction of rotation of the turbine wheel may be generally determined with all known sensor arrangements for determining the velocity of a moving body relative to a stationary body. Preferably, however, a magnetic-inductive speed measurement is provided. In this respect, an embodiment is preferred in which the at least one signal means is a permanent magnet and the signal receiver of the transducer is a magnetic flux sensor. Accordingly, it is expediently arranged on an outer circumference of the turbine wheel and advantageously on the outer ring surrounding the blades of the turbine wheel that at least one permanent magnet is moved when the turbine wheel rotates relative to a magnetic flux sensor fixedly arranged in the centrifugal pump, wherein the magnetic flux sensor of the sensor is set by rotation detects the changing magnetic field of the turbine wheel and converts it into an electrical signal which serves a signal connected to the transducer control device for determining the rotational speed of the turbine wheel and the flow through the centrifugal pump.

Instead of a magnetic-inductive measurement of the rotational speed of the turbine wheel, this can also be detected optically. Thus, as an alternative to at least one permanent magnet arranged on the turbine wheel and a magnetic flux sensor fixedly arranged in the centrifugal pump, for example, a refinement in which the at least one signal means is a light reflector which rotates through the beam path upon rotation of the turbine wheel a light source is moved, wherein the transducer has a light sensor which is arranged in the reflection beam path of the reflector. In this embodiment, the light sensor receives at each passage of the at least one light reflector through the beam path of a relative to the turbine fixedly arranged light source emitted light beam, a light signal from a signal connected to the transducer control device, the rotational speed of the turbine wheel and, consequently, the flow through the Centrifugal pump determined.

In an alternative to a rotatable relative to the pump shaft arrangement of the turbine wheel, this can also be advantageously arranged rotationally fixed in the centrifugal pump, wherein the pump shaft can rotate in the interior of the turbine wheel. In this case, although the flow of the turbine wheel through the flow causes no rotational movement of the turbine wheel, but still acting on the turbine torque can be detected and thus directly form the basis for determining the flow rate or the flow rate of the fluid flowing through the centrifugal pump ,

In an advantageous embodiment of this embodiment, the flow measuring device on a transducer in the form of a force transducer, which is arranged such that it measures a torque acting on the turbine wheel. Again, the transducer is expediently arranged fixed in or on the centrifugal pump, wherein it is in operative connection with the turbine wheel. In principle, all sensors suitable for detecting forces or moments, such as strain gauges, piezoelastic sensors and the like, can be used as force transducers.

Preferably, the force transducer is not in direct contact with the turbine wheel, but is operatively connected via a suitable for the transmission of forces or moments component with the turbine wheel, which makes it possible to arrange the force transducer at a particularly favorable location in the centrifugal pump. It is advantageously provided that at least one recess is formed on the outer circumference of the turbine wheel, into which engages a torque arm in contact with the force transducer. The moment arm is in this case formed by a torsionally stiff component, by means of which a torque acting on the turbine wheel can be transmitted in an unadulterated manner to the force transducer arranged at a distance from the turbine wheel. The moment arm is expediently with a free end in contact with the force transducer and engages with another end positively in the at least one recess on the turbine wheel.

To fix the moment arm on the turbine wheel, the turbine wheel is aligned during assembly of the centrifugal pump in such a way that the moment arm engages positively in the recess formed on the turbine wheel. This work is facilitated by the fact that, as is further preferred, formed over the outer circumference of the turbine wheel, a plurality of recesses for receiving the moment arm, so that the moment arm for attachment to the turbine wheel in any of the formed on the outer circumference of the turbine wheel recesses can intervene positively.

According to a further preferred development of the invention, the measuring transducer of the flow measuring device is arranged outside the interior of the pump housing of the centrifugal pump. This embodiment, in which the transducer does not engage in the interior of the pump housing, but quite in a Wandungsteil the pump housing may be integrated, is advantageous in that electrical components of the transducer are protected in this way from the flow in the interior of the pump housing, without these components must be encapsulated in a complicated manner fluidly against the flow through the centrifugal pump.

Preferably, an opening is formed on the outer wall of the pump housing, on the outside of which the transducer is arranged. This arrangement of the transducer has the advantage that the transducer is not only sufficiently protected from the flow in the pump housing, but also, for example, is easily accessible for maintenance or repair purposes. In addition, the opening on which the transducer is arranged expediently removable destructive, are also used to vent the pump housing when removing the transducer so that no additional opening must be formed on the pump housing for this purpose.

Fig. 1

in einer teilgeschnittenen perspektivischen Darstellung eine Kreiselpumpe gemäß einer ersten Ausgestaltung,

Fig. 2

eine Einzelheit A aus Fig. 1,

Fig. 3

in einer teilgeschnittenen perspektivischen Darstellung eine Kreiselpumpe gemäß einer zweiten Ausgestaltung,

Fig. 4

eine Einzelheit B aus Fig. 3,

Fig. 5

in einer Gegenüberstellung perspektivisch ein Turbinenrad sowie ein Laufrad und Leitrad einer Pumpenstufe der Kreiselpumpen nach den Fig. 1 und 3 und

Fig. 6

in einer Schnittansicht einen Teil einer Kreiselpumpe gemäß einer dritten Ausgestaltung.

The invention is explained in more detail with reference to exemplary embodiments illustrated in the drawings. In the drawings show in each case schematically simplified and in different scales:

Fig. 1

in a partially cutaway perspective view of a centrifugal pump according to a first embodiment,

Fig. 2

a detail A from Fig. 1 .

Fig. 3

in a partially sectioned perspective view of a centrifugal pump according to a second embodiment,

Fig. 4

a detail B off Fig. 3 .

Fig. 5

in a juxtaposition in perspective a turbine wheel and an impeller and stator of a pump stage of centrifugal pumps after the Fig. 1 and 3 and

Fig. 6

in a sectional view of a part of a centrifugal pump according to a third embodiment.

The in the Fig. 1 and 2 illustrated centrifugal pump has a pump housing 2, which is formed by a lower housing part 4, an adjoining hollow cylindrical housing middle part 6 and a subsequent upper housing part 8. On the lower housing part 4, a fluid inlet 10 and a fluid outlet 12 of the centrifugal pump are formed. The fluid inlet 10 is in fluid communication with five pump stages 14 of the centrifugal pump, which are arranged one above the other in the region of the housing middle part 6 in the direction of the housing upper part 8. Each of the pump stages 14 has a fixed housing 16 in the pump housing, in which an impeller 18 and a guide or stator 20 are arranged, which in Fig. 5 are shown. The housings 16 are in each case flow-connected to adjacent housings 16, with a last housing 16 in the direction of the upper housing part 16 being flow-connected via an opening 22 to a pressure chamber 24 formed in the region of the upper housing part 8.

The wheels 18 of the pump stages 14 are rotatably connected to a pump shaft 26, which is concentric with the middle part of the housing 6 extends through the pump housing 2 and protrudes from the pump housing 2 on the upper housing part 8. There, the pump shaft 26 is connected to the motor shaft of a drive motor, not shown, which is mounted on a formed on the upper housing part 8 motor chair 28. When the pump shaft 26 is driven, the impellers 18 of the individual pump stages convey a fluid from the fluid inlet 10 through the pump stages 14 to the pressure chamber 24, from where the fluid flows via an annular gap 30 between the wall of the housing middle part 6 and the housing 16 of the pump stages to the fluid outlet 12 of the centrifugal pump passes. Alternatively, the fluid outlet 12 could also be located at the opposite axial end of the centrifugal pump.

Downstream of the last in the flow direction, directly adjacent to the pressure chamber 24 pump stage 14, a turbine wheel 32 is rotatably mounted in the pressure chamber 24. This turbine wheel 32 is arranged around the pump shaft 26, wherein the pump shaft 26 passes through a hub 34 of the turbine wheel 32 and the turbine wheel 32 is rotatably mounted on the pump shaft 26. Starting from the hub 34, a plurality of blades 36 extend radially outward, where they are connected to an outer ring 38 of the turbine wheel 32. Here, the blades 36 of the turbine wheel 32 are arranged in the flow direction of the centrifugal pump directly above the formed on the last pump stage 14 opening 22 through which the flow reaches the pressure chamber 24 in the axial direction of the pump housing by the centrifugal pump. By this flow hits the blades 36 of the turbine wheel 32, it applies a torque to the turbine wheel 32, whereby this is set in a rotational movement. The torque exerted by the flow on the turbine wheel is in this case directed opposite to a purpose of fluid delivery via the pump shaft 26 to the impeller 18 torque exerted, which also with reference to the in Fig. 5 each in installed position turbine wheel 32 and of the impeller 18 becomes clear, since it can be seen that the blades 36 of the turbine wheel 32 are oriented virtually opposite to the blades 40 of the impeller 18. Thus, in operation, the turbine wheel 32 rotates counter to the pump shaft 26 in operation.

The turbine wheel 32 forms a transmitter of a flow measuring device, with which the flow rate through the centrifugal pump during operation of the centrifugal pump is continuously determined to then flow, for example, in the control of the drive motor for the centrifugal pump. To form a transmitter that is in the Fig. 1 and 2 shown turbine wheel 32 equipped with three signal means in the form of permanent magnets 42 which are arranged in three recesses 44 which are formed on the outer peripheral side of the outer ring 38 of the turbine wheel 32 in relation to the direction of rotation of the turbine wheel 32 different distances from each other.

On the upper housing part 8 of the pump housing 2, an opening 46 is formed. This opening 46 is penetrated by a transducer 48 of the flow measuring device, which extends into the immediate vicinity of the outer ring 38 of the turbine wheel 32. This sensor 48 has a signal receiver in the form of a magnetic flux sensor, which detects the magnetic fields emanating from the three permanent magnets 42 upon rotation of the turbine wheel 32, whereupon a control device signal-connected to the sensor 48, which is not shown in the drawings, the rotational speed of the turbine wheel 32 and concomitantly determines the flow rate through the centrifugal pump. Due to the different spacing of the permanent magnets 42 from one another, the control device can also determine the direction of rotation of the turbine wheel 32.

In the Fig. 6 only partially illustrated centrifugal pump differs from that in the Fig. 1 and 2 shown centrifugal pump only in terms of the design of the flow measuring device. Again, the transmitter of the flow measuring device is formed by a rotatably mounted on the pump shaft 26 rotatably mounted turbine wheel 32 ', wherein the pump shaft 26, a hub 34' of the turbine wheel 32 'passes through. The type and arrangement of the blades 36 of the turbine wheel 32 'correspond to those of the turbine wheel 32 of the centrifugal pump shown in Figs.

Diagonally above the turbine wheel 32 ', a threaded opening 50 is formed on the housing upper part 8 of the pump housing 2, into which a flow sensor 48' of the flow measuring device is screwed, although the sensor 48 'partially engages in the opening 50, but not in the interior of the pressure chamber 24 protrudes. When removing the transducer 48 ', the opening 50 can be used to vent the pump housing.

Out Fig. 6 not immediately apparent, has the transducer 48 'via a light source and a light sensor, which are arranged substantially on the outside of the housing top 8 and the outside of the pump housing 2. A light beam X emitted by the light source of the measuring transducer 48 'strikes the outer ring 38' of the turbine wheel 32 '.

Unlike the turbine wheel 32 of the centrifugal pump after the Fig. 1 and 2 are on an outer ring 38 'of the turbine wheel 32' instead of the in the Fig. 1 and 2 shown centrifugal pump distributed over the outer circumference of the outer ring 38 'at different intervals a plurality of light reflectors, not shown, arranged at a caused by the flow of rotation of the turbine wheel 32 'move through the beam path of the light beam X. As soon as the light beam X hits one of the light reflectors, it is reflected back to the transducer 48 ', where it is detected by the light sensor arranged in the transducer 48'. From this, a control device, which is signal-connected to the light sensor, also determines in Fig. 6 is omitted for reasons of clarity, the rotational speed of Trubinenrads 32 'and based on the flow rate through the centrifugal pump. In addition, due to the different distance of the light reflectors from each other by the control device, the direction of rotation of the turbine wheel can be determined.

Also in the 3 and 4 shown centrifugal pump differs from the in the Fig. 1 and 2 shown centrifugal pump only in terms of the design of the flow measuring device. In the case of this flow measuring device, too, a transmitter is formed by a turbine wheel 32 ". The arrangement of this turbine wheel 32" in the pressure chamber 24 is such that the pump shaft 26 reaches through a hub 34 "of the turbine wheel 32". The type and arrangement of the blades 36 of the turbine wheel 32 "correspond to those of the turbine wheels 32 and 32 '.""On an outer ring 38" of the turbine wheel 32 ", a plurality of recesses 52 are uniformly distributed on its outer circumference, the meaning of which will be discussed below.

Diagonally above the turbine wheel 32 ", an opening 54 is formed on the upper housing part 8 of the pump housing 2, whose central axis is directed onto the outer circumference of the outer ring 38" of the turbine wheel 32 ". This sleeve 56 is penetrated by a moment arm 58, which engages in the interior of the pressure chamber 24. In the sleeve 56, the moment arm 58 is fixed in a form-fitting manner transversely to its longitudinal extent At the end, the moment arm 58 has a cylindrical projection 60 whose outer cross section corresponds to the cross section of the recesses 52 formed on the outer ring 38 "of the turbine wheel 32". With the projection 60, the moment arm 58 engages in one of the recesses 52 on the outer ring 38 "of the turbine wheel 32", whereby the turbine wheel 32 is prevented from rotating.

In addition to the moment arm 58, a measuring transducer 48 "of the flow measuring device also engages in the sleeve 56. This transducer 48" has a signal receiver, not visible in the drawing, in the form of a force transducer, which is in contact with the moment arm 58. If the blades 36 of the turbine wheel 32 "flowed through by the flow through the centrifugal pump, the turbine wheel 32" can not rotate this, but the flow causes a torque or a force on the turbine wheel 32 "of the turbine wheel 32" on the torque arm 58 is forwarded to the transducer 48 "and is detected there by the force transducer, whereupon a signal connected to the force transducer controller, which is also not shown in the drawing, on the basis of the detected torque or the detected force of the flow through the centrifugal pump is determined.

LIST OF REFERENCE NUMBERS

2

pump housing

4

Housing bottom

6

Housing body

8th

Housing top

10

fluid inlet

12

fluid outlet

14

pump stage

16

casing

18

Wheel

20

stator

22

opening

24

pressure chamber

26

pump shaft

28

motor bracket

30

annular gap

32, 32 ', 32 "

turbine

34, 34 ', 34 "

hub

36

shovel

38, 38 ', 38 "

outer ring

40

shovel

42

permanent magnet

44

deepening

46

opening

48, 48 ', 48 "

transducer

50

opening

52

recess

54

opening

56

shell

58

moment arm

60

head Start

A

detail

B

detail

X

beam of light

Claims (13)

1. A centrifugal pump with at least one pump stage (14), with an impeller (18) which is mounted on a pump shaft (26) in a rotationally fixed manner and with a turbine wheel (32, 32', 32") which is arranged on the pump shaft (26) without a movement coupling to the pump shaft (26), in the delivery flow of the centrifugal pump and which forms a transducer of a flow measuring device, characterised in that a blading of the turbine wheel (32, 32', 32") is such that a torque exerted by the delivery flow onto the turbine wheel (32, 32', 32") is directed counter to a torque which is exerted onto the impeller (18) via the pump shaft (26).
2. A centrifugal pump according to claim 1, characterised in that the turbine wheel (32, 32', 32") is arranged downstream of a last pump stage (14).
3. A centrifugal pump according to one of the preceding claims, characterised in that the turbine wheel (32, 32', 32") is rotatably mounted on the pump shaft (26).
4. A centrifugal pump according to claim 3, characterised in that at least one signal means which moves relative to a signal receiver of a sensor (48, 48') of the flow measuring device is arranged on the turbine wheel (32, 32').
5. A centrifugal pump according to claim 4, characterised in that at least three signal means are arranged an outer periphery on the turbine wheel (32, 32') and have a different distance to one another in the rotation direction of the turbine wheel (32, 32').
6. A centrifugal pump according to one of the claims 4 or 5, characterised in that the at least one signal means is a permanent magnet (42) and the signal receiver of the sensor (48) is a magnetic flux sensor.
7. A centrifugal pump according to one of the claims 4 or 5, characterised in that the at least one signal means is a light reflector which on rotation of the turbine wheel moves through the beam path of a light source, wherein the sensor (48') comprises a light sensor which is arranged in the reflection beam path of the reflector.
8. A centrifugal pump according to one of the claims 1 or 2, characterised in that the turbine wheel (32") is arranged in the centrifugal pump in a rotationally fixed manner.
9. A centrifugal pump according to claim 8, characterised in that the flow measuring device comprises a sensor (48") in the form of a force sensor which measures a torque acting upon the turbine wheel (32").
10. A centrifugal pump according to claim 9, characterised in that at least one opening (52) is formed on the outer periphery of the turbine wheel (32"), into which opening a moment arm in contact with the force sensor engages.
11. A centrifugal pump according to claim 10, characterised in that a multitude of openings (32) for receiving the moment arm is formed over the outer periphery of the turbine wheel (32").
12. A centrifugal pump according to one of the claims 4 to 7 or 9 to 11, characterised in that the sensor (48', 48") is arranged outside the inner space of the pump casing (2) of the centrifugal pump.
13. A centrifugal pump according to claim 10, characterised in that an opening is formed on an outer wall of the pump casing (2), at the outer side of which opening the sensor (48") is arranged.

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