Pump assembly
By using expansion elements with high thermal expansion coefficient material in the inflow nozzle of the centrifugal pump, the problem of gap increase during thermal operation is solved, and the effect of reducing volume loss and improving pump efficiency is achieved.
Patent Information
- Application Number
- CN202380056512.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-07-25
- Filing Date
- 2023-07-06
- Publication Date
- 2025-03-14
AI Technical Summary
During the thermal operation of the centrifugal pump, due to changes in pressure and temperature, the radial annular gap between the hydraulic housing and the inflow nozzle increases, resulting in volume loss and pump efficiency decreases.
A sleeve-shaped or annular expansion element is used, and the material has a higher coefficient of thermal expansion than the hydraulic housing. It is connected to the sections of the inflow nozzle by welding or heat shrinkage to ensure that the expansion element and the hydraulic housing are abutted or reduced in gap during thermal operation.
Effectively reduce or close radial annular clearance, reduce volume loss, improve pump efficiency, and maintain reliability during assembly and operation.
Smart Images
Figure CN119630887A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a pump assembly, in particular a centrifugal pump assembly, comprising a hydraulic housing, a suction pipe with an inlet opening and configured on the hydraulic housing, a pressure pipe with an outlet opening and configured on the hydraulic housing, a flow chamber at least partially delimited by the hydraulic housing, a housing cover closing the hydraulic housing, an impeller arranged in the flow chamber and drivable around a rotation axis via a shaft, and an inlet nozzle, the inlet nozzle having a first end directly or indirectly connected to the hydraulic housing and a substantially cylindrical section, the section extending coaxially with the rotation axis in the direction of the inlet opening, wherein a second free end arranged opposite the first end is arranged in a recess of the inlet opening at the transition from the inlet opening to the flow chamber and a radial annular gap is generated in the region of the recess between the section of the inlet nozzle and the hydraulic housing. Background Art
[0002] Such pump assemblies find application, for example, in nuclear primary coolant pumps.
[0003] The free end of the inflow nozzle and the hydraulic housing form an annular gap, which connects the high-pressure area and the low-pressure area of the pump. Due to the pressure difference between the high-pressure area and the low-pressure area, a volume flow through the gap is generated, which leads to volume loss and thus reduced pump efficiency. These volume losses depend on the pressure difference and the gap width between the housing and the inflow nozzle. In order to achieve the assembly of the inflow nozzle, a certain radial annular gap between these two components is inevitable. In addition, the gap increases during hot operation due to the expansion of the hydraulic housing caused by internal pressure and temperature. This leads to increased volume loss through the gap during hot operation, and thus leads to reduced efficiency. The object of the present invention is to minimize the annular gap, especially the radial gap width, during hot operation, and thereby reduce volume loss and improve pump efficiency. This takes into account the fact that for assembly technology reasons, a certain gap is always required at ambient temperature. Summary of the invention
[0004] The object of the present invention is to alleviate or even completely eliminate the disadvantages of the devices known in the prior art. In particular, the object of the present invention is to provide a pump assembly in which the increase in clearances due to pressure and temperature in hot operation of the pump is reduced and the efficiency of the pump is increased.
[0005] This object is achieved by a pump component having the features of claim 1, according to which the cylindrical section is divided into a first partial section and a second partial section close to the free end, and in the area of the free end, the second partial section includes a sleeve-shaped or ring-shaped expansion element, wherein the material of the expansion element has a higher thermal expansion coefficient than the material of the hydraulic housing.
[0006] In order to reliably reduce or completely close the annular gap, it has proven to be particularly advantageous if the material of the expansion element comprises austenitic steel. Austenitic materials have a high coefficient of expansion and at the same time are highly resistant to the pumped medium.
[0007] A simple and operationally reliable embodiment can be achieved in that the expansion element and the first subsection are welded to one another, wherein the material of the expansion element has a higher coefficient of expansion than the hydraulic housing.
[0008] Thus, precise alignment of the first partial section with the second partial section is possible during operation without significant offset, and the inner circumference of the expansion element and the inner circumference of the first partial section are essentially aligned in a flow-beneficial manner, the expansion element preferably having a contact surface pointing to the first partial section, which comprises an axial annular protrusion and an axial recess.
[0009] For this purpose, the first subsection has a contact surface which is oriented toward the expansion element and which is designed at least partially complementary to a contact surface of the expansion element.
[0010] In an alternative embodiment, the second partial section close to the free end comprises, in the region of the free end, a sleeve-shaped or ring-shaped expansion element and a retaining device which at least partially surrounds the expansion element.
[0011] For an operationally reliable structure, the holding device is advantageously designed in one piece with the first subsection and the expansion element is arranged in the holding device.
[0012] The material of the retaining device advantageously has a lower coefficient of expansion than the material of the sleeve-shaped or annular expansion element. As a result, the retaining device is stretched outwards at higher temperatures via the sleeve-shaped or annular expansion element due to the higher coefficient of expansion of the sleeve-shaped or annular expansion element, and thus the gap with the hydraulic housing is reduced or closed.
[0013] For easy assembly and reliable operation, the expansion element and the holding device are connected to one another by means of a shrink fit, thereby eliminating the need for welding processes.
[0014] In order to be able to reliably close the radial annular gap during hot operation, the retaining device advantageously has a region with an enlarged inner diameter, so that the retaining device is flexible in the radial direction. BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Further advantages, features and effects of the present invention are obtained from the following figure. In which:
[0016] Figure 1shows a longitudinal section through a pump assembly with an inflow nozzle according to the prior art,
[0017] Figure 2 shows a longitudinal section through a first embodiment of an inflow nozzle according to the invention,
[0018] Figure 3 A longitudinal section through a second embodiment of an inlet nozzle according to the invention is shown. DETAILED DESCRIPTION
[0019] Figure 1 A pump assembly 1 according to the prior art is shown in the form of a main coolant pump assembly. The pump assembly 1 has a housing part designed as a hydraulic housing 2 , a housing cover 3 and a lantern 4 .
[0020] The hydraulic housing 2 has an inlet opening 6 for sucking in the conveying medium at the suction connection 5 and an outlet opening 8 for discharging the conveying medium at the pressure connection 7. The housing cover 3 is arranged on the side of the hydraulic housing 2 opposite the inlet opening 6. The lantern 4 is fixed 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.
[0021] A shaft 9 rotatable about an axis of rotation A, which in the exemplary embodiment shown is constructed in multiple parts, extends from a motor (not shown) through an opening 10 provided in the housing cover 3 into a flow chamber 11 delimited by means of the hydraulic housing 2 and the housing cover 3 .
[0022] A not shown bearing device for supporting the shaft 9 is arranged in the opening 10. The flow chamber 11 is sealed against leakage into the lantern 4 by means of a sealing set 12 which comprises a plurality of sealing devices arranged one behind the other in the axial direction.
[0023] The impeller 14 is fastened to the end 13 of the shaft 9 which is located in the flow chamber 11. In the exemplary embodiment, a stator 15 is arranged or fastened to the hydraulic housing 2 on the side opposite the suction connection 5 or the inlet opening 6 so as to be rotationally fixed and non-displaceable in the axial direction around the impeller 14. The stator 15 ensures that the turbulent flow losses leaving the impeller 14 are diverted into a turbulence-free flow with as few as possible losses, wherein the magnitude of the absolute velocity is reduced and the static pressure is increased.
[0024] The inlet nozzle 17 is fastened with a first end 16 to the guide wheel 15. The inlet nozzle 17 has an approximately cylindrical section 18 which extends coaxially with the axis of rotation A in the direction of the inlet opening 6. A second free end 19, which is located 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, i.e. in the region of the increased inner diameter. In the region of the increased inner diameter, a radial annular gap 21 is produced between the section 18 in the region close to the free end 19 of the inlet nozzle 17 and the hydraulic housing 2.
[0025] In other embodiments (not shown, however), the inflow nozzle 17 and the guide wheel 15 can be designed as a single part or as a one-piece component.
[0026] Instead of the inlet nozzle 17 which is indirectly connected to the hydraulic housing 2 via the stator 15 and the housing cover 3 , an inlet nozzle 17 which is directly connected to the hydraulic housing 2 may also be provided.
[0027] Figure 2 The arrangement of the free end 19 of the inlet nozzle 17 according to the first embodiment of the invention in the recess 20 is shown, wherein: Figure 2 The left area of the sectional view shows the complete inflow nozzle 17, while the right area shows substantially its free end 19. The segment 18 is divided into a first partial segment 22 and a second partial segment 23 near the free end 19. In the region of the free end 19, the second partial segment 23 comprises a sleeve-shaped or annular expansion element 24. The expansion element 24 and the first partial segment 23 are welded to each other. The inner circumference of the expansion element 24 and the inner circumference of the first partial segment 22 of the segment 18 are substantially 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 the segment 18. The expansion element 24 has a contact surface 25 pointing to the first partial segment 22, which comprises an annular axial protrusion 26 and an axial recess 27. The first partial segment 22 has a contact surface 28 oriented toward the expansion element 24, which is configured to be 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 elevation 26 engages.
[0028] During operation, precise alignment of the second subsection 23 or the expansion element 24 on the first subsection 22 is therefore possible without significant deflection. The inner circumference of the expansion element 24 and the inner circumference of the first subsection 22 are essentially aligned in a flow-friendly manner.
[0029] Welding can be partial welding, such as Figure 2 , or a through-weld over the entire radial extension of the partial section 23 .
[0030] The annular gap 21 with the radial gap width w is designed such that in the cold state of the centrifugal pump 1, a return flow of the conveying medium via the annular gap 21 into the inlet opening 6 (thus from the high-pressure area via the annular gap 21 into the low-pressure area) is possible. During operation with a generally hot conveying 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, in particular due to its expansion in the radial direction, comes to bear against 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.
[0031] Figure 3 A further embodiment of an inlet nozzle 17 according to the invention is shown. Figure 3 The left area of the embodiment shows the entire inflow nozzle 17, while the right area shows essentially the free end 19 of the inflow nozzle 17. The second partial section 23 near the free end 19 comprises a sleeve-shaped or annular expansion element 24 and a retaining device 30 at least partially surrounding the expansion element 24 in the area of the free end 19. The retaining device 30 is constructed in one piece with the first partial section 22 and thus forms an area with an increased 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 shrink fit. In this embodiment as well, the inner circumference of the expansion element 24 and the inner circumference of the first partial section 22 of the section 18 are substantially 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 retaining device 30. The retaining device 30 has an area 31 with an increased inner diameter, so that the retaining device 30 has a certain flexibility in the radial direction.
[0032] During operation with a hot transport medium, the expansion element 24 expands. Due to its radial expansion component, the expansion element 24 brings the flexibly arranged retaining 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.
[0033] By means of the described embodiment of the inflow nozzle 17, volume losses are reduced and the pump efficiency is increased during hot operation by constricting or closing the annular gap 21. The expansion element 24 preferably consists of austenitic steel.
Claims
1. A pump assembly (1), in particular a centrifugal pump assembly, comprising: Hydraulic housing (2), a suction connection (5) with an inlet opening (6) formed on the hydraulic housing (2), a pressure connection (7) with an outlet opening (8) formed on the hydraulic housing (2), a flow chamber (11) at least partially delimited by the hydraulic housing (2), a housing cover (3) closing the hydraulic housing (2), an impeller (14) arranged in the flow chamber (11) and drivable about a rotation axis (A) via a shaft (9); and an inlet nozzle (17) having a first end (16) connected directly or indirectly to the hydraulic housing (2) and a substantially cylindrical section (18) extending coaxially with the axis of rotation (A) in the direction of the inlet opening (6), in, 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 In the region of the recess (20), a radial annular gap (21) is produced between the section (18) of the inlet nozzle (17) and the hydraulic housing (2). It is characterized in that The section (18) is divided into a first section (22) and a second section (23) close to the free end (19), and in the region of the free end (19), the second section (23) comprises a sleeve-shaped or ring-shaped expansion element (24), wherein the material of the expansion element (24) has a higher coefficient of thermal expansion than the material of the hydraulic housing (2).
2. The pump assembly (1) according to claim 1, characterized in that The material of the expansion element (24) includes austenitic steel.
3. The pump assembly (1) according to any one of claims 1 or 2, characterized in that The expansion element (24) and the first subsection (23) are welded to one another.
4. The pump assembly (1) according to any one of claims 1 to 3, characterized in that The expansion element (24) has a contact surface (25) facing the first subsection (22) and having an annular axial elevation (26) and an axial depression (27).
5. The pump assembly (1) according to any one of claims 1 to 4, characterized in that The first partial section (22) has a contact surface (28) oriented toward the expansion element (24) and configured to be at least partially complementary to a contact surface (25) of the expansion element (24).
6. The pump assembly (1) according to any one of claims 1 or 2, characterized in that A second partial section (23) close to the free end (19) comprises, in the region of the free end (19), a sleeve-shaped or ring-shaped expansion element (24) and a retaining device (30) at least partially surrounding the expansion element (24).
7. The pump assembly (1) according to claim 6, characterized in that The holding device (30) is formed integrally with the first partial section (22), and the expansion element (24) is arranged in the holding device (30).
8. A pump assembly (1) according to any 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. The pump assembly (1) according to any one of claims 6 to 8, characterized in that The retaining device (30) has a region (31) with a reduced inner diameter, such that the retaining device (30) is flexible in the radial direction.