PUMP ARRANGEMENT

Description

[0001] The invention relates to a pump arrangement, in particular a centrifugal pump arrangement, comprising a hydraulic housing, a suction port formed on the hydraulic housing with an inlet opening, a pressure port formed on the hydraulic housing with an outlet opening, a flow chamber at least partially bounded by the hydraulic housing, a housing cover closing the hydraulic housing, an impeller arranged in the flow chamber and driven about an axis of rotation via a shaft, and an inlet nozzle with a first end connected directly or indirectly to the hydraulic housing and a substantially cylindrical section extending coaxially to the axis of rotation towards the inlet opening, wherein a second section opposite the first endThe free end is arranged at the transition from the inlet opening to the flow chamber in a recess of the inlet opening, and a radial annular gap is created in the area of ​​the recess between the section of the inlet nozzle and the hydraulic housing.

[0002] Such pump arrangements are used, for example, in nuclear main coolant pumps.

[0003] From US 4,177,008 A, a main coolant pump is known which comprises a spherical housing, an inlet with an outer section rigidly connected to the housing and inclined with respect to the axis of the impeller, a discrete inner section installed in the housing, and an outlet which serves to convey the pressurized fluid out of the housing and preferably extends radially from the housing.

[0004] GB 1 353 554 A discloses a centrifugal pump with a casing having a spherical or ellipsoidal shape and at least two openings for the flow of the pumped medium and a further opening for connecting the pump assembly to a drive mechanism. The casing consists of at least two welded sections forming overlapping segments of the casing surface, the sections having either pre-formed or welded suction, discharge, and connection ports at the corresponding positions of the openings in the casing, and the inner working surface of the casing being provided with a layer of corrosion-resistant material.

[0005] The free end of the inlet nozzle and the hydraulic housing form an annular gap connecting the high-pressure and low-pressure sections of the pump. Due to the pressure difference between these two sections, a flow of fluid occurs through this gap, leading to volumetric losses and thus reduced pump efficiency. These volumetric losses depend on the pressure difference and the gap width between the housing and the inlet nozzle. A certain radial annular gap between these two parts is unavoidable to allow for the installation of the inlet nozzle. Additionally, during operation at high temperatures, the gap is enlarged by the expansion of the hydraulic housing due to internal pressure and temperature. This leads to increased volumetric losses through this gap during operation at high temperatures and consequently to reduced efficiency.The aim of the present invention is to minimize the annular gap, in particular the radial gap width, during hot operation, thereby reducing volumetric losses and increasing the pump's efficiency. This is achieved while taking into account the fact that a certain gap is still necessary at ambient temperature for assembly reasons.

[0006] The present invention is based on the objective of mitigating or even completely eliminating the shortcomings of devices known from the prior art. Specifically, it is an objective of the present invention to provide a pump arrangement in which the increase in the gap due to pressure and temperature during hot operation of the pump is reduced and the efficiency of the pump is increased.

[0007] This problem is solved by a pump arrangement with the feature of claim 1, wherein the cylindrical section is divided into a first subsection and a second subsection near the free end, and in the region of the free end the second subsection comprises a sleeve- or ring-shaped expansion element, wherein the material of the expansion element has a higher coefficient of thermal expansion than the material of the hydraulic housing.

[0008] To reliably reduce or completely close the annular gap, it has proven particularly advantageous for the expansion element to be made of austenitic steel. Austenitic materials exhibit a high coefficient of thermal expansion while simultaneously offering good resistance to the conveyed medium.

[0009] A simple and reliable embodiment can be obtained by welding the expansion element and the first subsection together, wherein the material of the expansion element has a higher coefficient of expansion than the hydraulic housing.

[0010] In order to enable precise alignment of the first subsection with the second subsection without significant step during operation, and to ensure that the inner surface of the expansion element and the inner surface of the first subsection are essentially in line with each other in a flow-optimized manner, the expansion element preferably has a contact surface facing the first subsection, which includes an axial annular protrusion and an axial recess.

[0011] In addition, the first subsection has a contact surface directed towards the expansion element, which is at least partially complementary to the contact surface of the expansion element.

[0012] In an alternative embodiment, the second subsection near the free end comprises the sleeve- or ring-shaped expansion element and a holding device that at least partially surrounds the expansion element.

[0013] Advantageously, for a reliable design, the holding device is formed integrally with the first section and the expansion element is arranged in the holding device.

[0014] The material of the retaining device advantageously has a lower coefficient of thermal expansion than the material of the sleeve- or ring-shaped expansion element. This allows the retaining device to expand outwards at higher temperatures due to the higher coefficient of thermal expansion of the sleeve- or ring-shaped expansion element, thus reducing or closing the gap to the hydraulic housing.

[0015] For easy installation and safe operation, the expansion element and the retaining device are connected using a shrink-fit press fit. This eliminates the need for welding.

[0016] In order to ensure that the radial annular gap can be securely closed during hot operation, the holding device advantageously has an area with an enlarged inner diameter, such that the holding device has flexibility in the radial direction.

[0017] Further advantages, features and effects of the present invention will become apparent from the figures below. Fig. 1 shows a longitudinal section through a pump arrangement with an inlet nozzle according to the prior art, Fig. 2 shows a longitudinal section through a first embodiment of the inlet nozzle according to the invention, Fig. 3 shows a longitudinal section through a second embodiment of the inlet nozzle according to the invention.

[0018] The Fig. 1 Figure 1 shows a pump arrangement 1 in the form of a main coolant pump arrangement according to the prior art. The pump arrangement 1 comprises a housing part designed as a hydraulic housing 2, a housing cover 3 and a lantern 4.

[0019] The hydraulic housing 2 has an inlet opening 6 at a suction port 5 for drawing in a pumped medium and an outlet opening 8 at a pressure port 7 for expelling the pumped medium. The housing cover 3 is located on the side of the hydraulic housing 2 opposite the inlet opening 6. The lantern 4 is attached to the side of the housing cover 3 facing away from the hydraulic housing 2. A motor (not shown) is connected to the hydraulic housing 2 by means of the lantern.

[0020] A shaft 9 rotatable about an axis of rotation A, which in the exemplary embodiment is designed in multiple parts, extends from the motor (not shown) through an opening 10 provided in the housing cover 3 into a flow chamber 11 bounded by the hydraulic housing 2 and the housing cover 3.

[0021] A bearing device (not shown) for supporting the shaft 9 is provided in the opening 10. A sealing assembly 12, comprising several sealing devices arranged one behind the other in the axial direction, seals the flow chamber 11 against leakage into the lantern 4.

[0022] An impeller 14 is attached to an end 13 of the shaft 9 located within the flow chamber 11. In the exemplary embodiment, a guide vane 15 surrounding the impeller 14 is arranged or attached to the hydraulic housing 2 on the side opposite the suction port 5 or the inlet opening 6. The guide vane 15 is rotationally fixed and axially displaceable. The guide vane 15 ensures that the swirling flow exiting the impeller 14 is deflected into a swirl-free flow with minimal loss, thereby reducing the absolute velocity and increasing the static pressure.

[0023] An inlet nozzle 17 is attached to the guide wheel 15 at a first end 16. The inlet nozzle 17 has a substantially cylindrical section 18 that extends coaxially to the axis of rotation A towards the inlet opening 6. A second, free end 19, opposite the first end 16, is located at the transition from the inlet opening 6 to the flow chamber 11 in a recess 20 of the inlet opening 6, i.e., a region with an enlarged inner diameter. In the region of the enlarged inner diameter, a radial annular gap 21 is formed between the section 18 near the region of the free end 19 of the inlet nozzle 17 and the hydraulic housing 2.

[0024] In another embodiment, which is not shown, the inlet nozzle 17 and the guide wheel 15 can be designed as a one-piece or single-piece component.

[0025] Instead of an inlet nozzle 17 that is indirectly connected to the hydraulic housing 2 via guide wheel 15 and housing cover 3, an inlet nozzle 17 that is directly connected to the hydraulic housing 2 can also be provided.

[0026] The Figure 2 Figure 1 shows the arrangement of the free end 19 of a first embodiment of the inlet nozzle 17 according to the invention in the retraction 20, wherein the left area of ​​the Fig. 2The complete inlet nozzle 17 and the right-hand area essentially show its free end 19. Section 18 is subdivided into a first subsection 22 and a second subsection 23 near the free end 19. In the region of the free end 19, the second subsection 23 includes a sleeve- or ring-shaped expansion element 24. The expansion element 24 and the first subsection 23 are welded together. The inner surface of the expansion element 24 and the inner surface of the first subsection 22 of section 18 are essentially aligned. The material of the expansion element 24 has a higher coefficient of thermal expansion than the material of the hydraulic housing 2 and / or section 18. The expansion element 24 has a contact surface 25 facing the first subsection 22, which includes an annular axial protrusion 26 and an axial recess 27.The first subsection 22 has a contact surface 28 directed towards the expansion element 24, which is at least partially complementary to the contact surface 25 of the expansion element 24. In particular, the contact surface 28 has a groove 29 into which the projection 26 engages.

[0027] Thus, during operation, precise alignment of the second section 23 or the expansion element 24 with the first section 22 is possible without any significant step. The inner surface of the expansion element 24 and the inner surface of the first section 22 are thus essentially in line, which is aerodynamically favorable.

[0028] Welding can be partial, as in Figure 2 depicted, act or a continuous weld over the entire radial extent of subsection 23.

[0029] The annular gap 21, which has a radial gap width w, is designed such that, when the centrifugal pump 1 is cold, backflow of the pumped medium through the annular gap 21 into the inlet opening 6 is possible, thus from the high-pressure area via the annular gap 21 into the low-pressure area. During operation with a typically hot pumped medium, the free end 19, in particular the expansion element 24, expands. Since the material of the expansion element 24 has a higher coefficient of thermal expansion than the material of the hydraulic housing 2, the expansion element 24, particularly due to its radial expansion, comes into contact with the hydraulic housing 2 in the recess 20 of the inlet opening 6 or at least reduces the annular gap 21 in the radial direction.

[0030] The Figure 3 Figure 1 shows another embodiment of the inlet nozzle 17 according to the invention. The left area of ​​the Fig. 3The first section shows the complete inlet nozzle 17, and the right-hand section essentially shows the free end 19 of the inlet nozzle 17. The second subsection 23, located near the free end 19, comprises, in the region of the free end 19, the sleeve- or ring-shaped expansion element 24 and a retaining device 30 that at least partially surrounds the expansion element 24. The retaining device 30 is formed integrally with the first subsection 22 and thus creates a region with an enlarged inner diameter. The expansion element 24 is arranged in the retaining device 30. The expansion element 24 and the retaining device 30 are connected to each other by means of a shrink-fit press fit. In this embodiment as well, the inner surface of the expansion element 24 and the inner surface of the first subsection 22 of section 18 are essentially aligned.The material of the expansion element 24 has a higher coefficient of thermal expansion than the material of the hydraulic housing 2 and the holding device 30. The holding device 30 has a region 31 with an enlarged inner diameter, so that the holding device 30 has some flexibility in the radial direction.

[0031] During operation with a hot conveying medium, the expansion element 24 expands. Due to its radial expansion component, the expansion element 24 brings the flexibly arranged holding device 30 in the recess 20 of the inlet opening 6 into contact with the hydraulic housing 2 or at least reduces the annular gap 21, in particular the radial gap width w, in the radial direction.

[0032] The described embodiments of the inlet nozzle 17 reduce volumetric losses and increase the pump's efficiency during hot operation by narrowing or closing the annular gap 21. The expansion element 24 preferably comprises austenitic steel.

Claims

1. Pump assembly (1), in particular a centrifugal pump assembly, comprising: a hydraulic casing (2); a suction port (5), which is formed on the hydraulic casing (2) and has an inlet opening (6); a pressure port (7), which is formed on the hydraulic casing (2) and has an outlet opening (8); a flow chamber (11), which is at least partially delimited by the hydraulic casing (2); a casing cover (3), which closes the hydraulic casing (2); an impeller (14), which is arranged in the flow chamber (11) and can be driven about an axis of rotation (A) via a shaft (9); and an inflow nozzle (17) having a first end (16), which is connected indirectly or directly to the hydraulic casing (2), and a substantially cylindrical portion (18), which extends coaxially with the axis of rotation (A) toward the inlet opening (6); wherein a second, free end (19) opposite the first end (16) is arranged in a recess (20) of the inlet opening (6) at the transition from the inlet opening (6) to the flow chamber (11), and a radial annular gap (21) is produced between the portion (18) of the inflow nozzle (17) and the hydraulic casing (2) in the region of the recess (20), characterized in that the portion (18) is divided into a first sub-portion (22) and a second sub-portion (23), which is close to the free end (19), and the second sub-portion (23) comprises a sleeve- or ring-like expansion element (24) in the region of the free end (19), wherein the material of the expansion element (24) has a higher coefficient of thermal expansion than the material of the hydraulic casing (2).

2. Pump assembly (1) according to Claim 1, characterized in that the material of the expansion element (24) comprises austenitic steel.

3. Pump assembly (1) according to one of Claims 1 or 2, characterized in that the expansion element (24) and the first sub-portion (22) are welded to one another.

4. Pump assembly (1) according to one of Claims 1 to 3, characterized in that the expansion element (24) has a contact face (25) that faces the first sub-portion (22) and comprises an annular axial elevation (26) and an axial offset (27).

5. Pump arrangement (1) according to Claim 4, characterized in that the first sub-portion (22) has a contact face (28) that faces the expansion element (24) and is at least partially complementary to the contact face (25) of the expansion element (24).

6. Pump assembly (1) according to one of Claims 1 or 2, characterized in that the second sub-portion (23) close to the free end (19) comprises, in the region of the free end (19), the sleeve- or ring-like expansion element (24) and a holding device (30) at least partially surrounding the expansion element (24).

7. Pump assembly (1) according to Claim 6, characterized in that the holding device (30) is formed integrally with the first sub-portion (22), and the expansion element (24) is arranged in the holding device (30).

8. Pump assembly (1) according to one of Claims 6 or 7, characterized in that the expansion element (24) and the holding device (30) are connected to one another by means of a shrink fit.

9. Pump assembly (1) according to one of Claims 6 to 8, characterized in that the holding device (30) has a region (31) with a reduced internal diameter such that the holding device (30) has flexibility in the radial direction.