Manufacturing of stepped casings using a hybrid process

Abstract

The present invention relates to a centrifugal pump (1) having an impeller (5, 9) surrounded by a casing (22). The casing (22) is provided with at least one guide element (23). The guide element (23) is designed as a hybrid component consisting of at least one conventionally manufactured component and at least one synthetically manufactured component.

Description

Technical Field

[0001] The present invention relates to a centrifugal pump having at least one impeller surrounded by a casing, the casing comprising at least one guiding device.

Background Art

[0002] A pump is called multi-stage when a plurality of impellers are arranged successively and the delivery stream flows continuously through the impellers. The delivery head of a single-stage centrifugal pump is substantially determined by the design of the impeller and the circumferential speed. If the rotational speed cannot be further increased due to other boundary conditions and / or an increase in the impeller diameter results in a very low specific rotational speed and thus uneconomical efficiency, the delivery head can be increased from an economic point of view by successively connecting a plurality of stages. By changing the number of stages while maintaining the dimensions and rotational speed, the delivery stream of such a multi-stage pump remains unchanged, but the output requirement and the delivery head vary in proportion to the number of stages.

[0003] The guiding device most often has a plurality of guide vanes. A guiding flow path for the medium pumped by the pump is formed between the guide vanes. Such a guiding device can be in the form of a guide wheel. The medium pumped by the pump exits the impeller and enters the guiding device. In the guiding device, the kinetic energy is converted into pressure energy. Further deflection of the medium occurs. The swirl is optionally reduced for the approaching flow to another pump stage.

[0004] DE3912279C2 describes a single-stage or multi-stage centrifugal pump having at least one impeller. A guide wheel is arranged downstream in the flow direction of the impeller. The guide wheel has a plurality of guide vanes.

[0005] An example of a pump having multiple identical stage casings connected in series is a ring section pump. This type is frequently used in power plant technology, for example, as boiler feedwater pumps, and in industrial applications where high discharge pressure is required.

[0006] Such centrifugal pumps are also known as double-casing pumps or barrel-casing pumps, and are centrifugal pumps surrounded by a barrel-shaped casing. The barrel casing is equipped with suction nozzles and discharge nozzles and is closed by a cover on a plane perpendicular to the shaft. Such pumps are typically multi-stage pumps used as high-pressure pumps and maximum-pressure pumps. Within the barrel casing, multiple stepped casings are arranged sequentially in the axial direction. Each stepped casing is equipped with a pump impeller and optionally with fixed guide wheels.

[0007] Each stepped casing is typically formed as a coherent pump insertion module together with the pump shaft. The flow transition from the final guide wheel or final stepped casing into the discharge nozzle is generally caused by the flow space formed within the barrel casing. DE102019001882A1 describes a centrifugal pump in which the internal contour of the helical flow space can enable increased efficiency in the final pump stage.

[0008] Guide wheels, and especially guide devices, are characterized by a solid structure with minimal filigree, which is produced in most cases by reshaping and primary molding processes. Improvements in pump efficiency are limited by the solidity of the guide elements, which are not optimized with respect to flow. Even a small increase in efficiency can have a significant economic impact, especially when used continuously as a boiler feedwater pump. [Overview of the project]

[0009] The object of the present invention is to provide a centrifugal pump with optimized flow induction, as well as a multi-stage centrifugal pump. The centrifugal pump has the highest possible efficiency. Flow separation is greatly hindered. Furthermore, the lowest possible delay loss is guaranteed. The centrifugal pump can be individually configured to meet customer requirements. This centrifugal pump consists of as few individual parts as possible, making assembly as easy as possible. Replacement of parts is easily done depending on the configuration of the centrifugal pump. The centrifugal pump can be produced easily and inexpensively.

[0010] This objective is achieved by the present invention with a centrifugal pump having at least one impeller. Preferred modifications are found in the independent claims, this specification and the drawings.

[0011] According to the present invention, the guide element of a centrifugal pump is configured as a hybrid component comprising at least one conventionally manufactured component and at least one generatively manufactured component, together with at least one impeller surrounded by a casing.

[0012] Generatively manufactured components are produced by generative manufacturing processes. The term generative manufacturing process encompasses all manufacturing processes in which materials are bonded layer by layer, thus producing three-dimensional components. Layer-by-layer build-up is performed under computer control from one or more liquid or solid materials according to predetermined dimensions and shapes. Physical or chemical curing or melting processes occur during the build-up. Typical materials for 3D printing include plastics, synthetic resins, ceramics, metals, carbon materials, and graphite materials.

[0013] A generative or additive manufacturing process is understood to be a process in which materials are deposited layer by layer to produce a three-dimensional component. According to the present invention, the guide elements of a guide device are in the form of generatively manufactured components. The guide elements are formed, in particular, using selective laser melting and laser cladding, also known as build-up welding. In alternative variations of the present invention, a process that can be used similarly is cooled gas blowing and extrusion molding combined with the deposition of a molten plastic material.

[0014] In selective laser melting, guide elements are produced by a process in which build-up material layers are first attached to the substrate. The build-up material for producing guide elements of the guide device is preferably metal powder particles. In one variant of the present invention, iron-containing powder particles and / or cobalt-containing powder particles are used for this purpose. These powder particles may contain additives such as chromium, molybdenum, and nickel. The metal build-up material is thinly attached to the plate in the form of powder. The powder material is then locally and completely melted at the desired location using radiation, and after solidification, a solid material layer is formed. The substrate is then lowered by the amount of the layer thickness, and the powder is attached again. This cycle is repeated until all layers have been produced and the completed guide element is formed. According to the present invention, structures that are particularly filigree, optimized with respect to flow, and that cannot be technically produced by conventional processes are produced here.

[0015] As a radiation source, for example, a laser beam can be used to generate guide elements from individual powder layers. Data for guiding the laser beam is generated using software based on a 3D CAD system. Instead of selective laser melting, an electron beam (EBN) can also be used.

[0016] In cladding or overlay welding, guide elements are produced by a process of covering the base structure with welds. Using filler material in the form of wire or powder, overlay welding, particularly filigree, constitutes a volume that produces a guide element shape optimized with respect to flow.

[0017] Until now, generatively manufactured guides could not be used in multi-section high-pressure centrifugal pumps and boiler feedwater pumps because the dimensions of these guides were technically unattainable or only difficult to achieve. Generatively manufactured guides are distinguished by their hydrodynamically optimized geometry, which cannot be achieved through cutting or casting processes. By forming a hybrid guide using multiple generatively manufactured guide elements that fit conventionally manufactured components, a hydrodynamically optimized geometry becomes possible, while component sizes exceeding known manufacturing dimensions possible by generative methods become possible.

[0018] According to the present invention, the guide device has three or more, preferably four or more, particularly five or more, and / or fewer than 24, preferably fewer than 22, particularly fewer than 20 generatively manufactured guide elements. Therefore, advantageously, a hybrid guide device consisting of multiple generatively manufactured and hydraulically optimized guide elements can be produced. The component sizes of the guide elements can be produced by a common manufacturing process that has all their advantages, and can also be very large thanks to the hybrid structure having conventional components.

[0019] Advantageously, the generatively manufactured components, particularly the guide elements, have an outwardly curved shape. The guide elements are hydrodynamically optimized by CFD with respect to their shape, deflecting the flow while reducing vortices without flow separation and without vortex buildup. The radially curved shape of the guide elements guides the flow to the next pump stage in a particularly ideal manner.

[0020] In a particularly advantageous embodiment of the present invention, the generatively manufactured components, in particular the guide element, have flow-guiding forming portions. The flow-guiding forming portions are molded and rounded portions of the guide element, which are in particular filigrees, and optimize the hydraulic efficiency of the pump in a highly advantageous manner. The flow-guiding forming portions allow the flow to be deflected to the next pump stage, ideally reducing flow vortices.

[0021] The pre-formed portion receives the discharge flow from the radial impeller and guides the discharge flow to the second formed portion with particularly low loss, and the second formed portion, together with the guide plate and adjacently positioned guide elements, forms a flow path. The fluid flows from this flow path to the downstream impeller in a particularly vortex-free manner. Ideally, the formed portion of the guide element can be configured to be particularly thin and have a fine radius of curvature as a result of generative manufacturing, which is not known for guide elements manufactured by conventional methods.

[0022] According to the present invention, generatively manufactured components, particularly guide elements, surround the guide plate with virtually no gaps. Thus, erroneous flow and efficiency losses are avoided. Generative manufacturing of guide elements enables extremely precise and accurate manufacturing, and therefore gapless mounting of hybrid guide devices to components manufactured by conventional methods.

[0023] Ideally, generatively manufactured components, particularly guide elements, have sealing elements for gapless connection to the guide plate. The generative manufacturing process allows for the intricately designed geometry of the guide elements, and therefore, when the hybrid elements of the guide device are assembled, a gapless connection can be produced, thereby optimally improving the efficiency of the centrifugal pump.

[0024] In an alternative modified form of the present invention, the walls of the guide element are very thin, and the guide element has an internal lattice structure to increase the strength of the walls. In this advantageous embodiment, a guide element having a particularly excellent ratio of mass to component volume can be realized. In particular, compared to guide devices manufactured by conventional methods, the hybrid form of the guide device has an extremely low mass.

[0025] In a particularly advantageous embodiment of the present invention, the hybrid structure of the guide device does not require further joining techniques. According to the present invention, generatively manufactured components, in particular the guide elements, have elements for engaging within mating elements (pair elements). For example, a short cylindrical pin can be formed on the guide element, and this pin can be inserted into a corresponding recess on a conventional component, thus forming a stable connection. Thus, the assembly of the centrifugal pump is considerably simplified because the components of the hybrid guide device can simply be mated with one another.

[0026] The term "conventional component" refers to components produced using primary forming, reforming, or removal manufacturing processes. Primary forming is the dominant group of manufacturing processes in which a geometrically defined solid body is produced from an intangible material. Primary forming is used to produce the initial shape of the solid body and to create material aggregation. In reforming, a blank of plastically deformable material is intentionally shaped differently without removing any material from the blank. In removal manufacturing processes, some material is removed from a workpiece. In addition to the components produced, chips are primarily formed.

[0027] According to the present invention, at least one conventionally manufactured component is in the form of a casing cover. In particular, in the case of a barrel casing pump, the structure is considerably simplified if the guide device also includes the casing. The number of required components and assembly are considerably reduced.

[0028] Advantageously, the components manufactured by the conventional method are in the form of a guide plate. A simple plate can be produced particularly economically and precisely by casting. The hybrid structure of the guide device combines components that are each produced in a hydraulically optimized manner by the most advantageous manufacturing process in order to form a device that achieves the best possible efficiency of a multistage centrifugal pump.

[0029] Ideally, at least one component manufactured by the conventional method, in particular the guide plate, has a fitting element for the engagement of the elements. For example, the fitting element is in the form of a cylindrical recess into which the pin-shaped element of the guide element engages, and thus a plug-in connection between the guide element and the guide plate can be realized. Thus, the assembly of the hybrid structure can be carried out particularly simply and time-efficiently.

[0030] In an alternative variant, the components produced by generative manufacturing and the components produced by the conventional method are joined by an inseparable connection, preferably a welded connection, in order to form the guide device. Such a connection is characterized by a robust and durable form of the connection.

[0031] When joining two or more solid bodies, the parts to be joined, which have a geometrically defined shape, are permanently connected. In the case of welding, the inseparable connection between the guide element and the guide plate is produced by applying heat and / or pressure, with or without a filler material. The filler material is usually supplied in the form of a rod or wire, melted and thus solidifies at the joint between the joining partners to form a bond. Welding is one of the substance-to-substance adhesion methods and produces a high-strength bond.

[0032] It is also particularly advantageous to manufacture large hybrid guide devices using an integrated additive manufacturing process. The casing cover and the guide plate are first formed by primary shaping and / or cutting. The guide elements are produced using a generative process. The hybrid guide device is completed by installing the guide plate together with the guide elements in the casing cover.

[0033] The build-up material for producing the contact surface of the guide element with the fluid is preferably metal powder particles. In one variant of the present invention, iron-containing particles and / or cobalt-containing particles are used for this purpose. These particles may contain additives such as chromium, molybdenum, and nickel.

[0034] According to the present invention, the guide elements of the guide device are formed by an additive manufacturing process. The three-dimensional morphology of the guide elements is stored in software as a dataset. A robotic arm equipped with various additive process tools operates at the location where the guide elements are to be formed, forming the contact surface with the fluid medium and the support grid structure of the contact surface layer by layer. Advantageously, the appropriate build-up process for each build-up material can be performed sequentially or simultaneously for each layer, thus forming complex guide elements of various materials, and each region of the guide element is optimally adapted to the requirements of the subsequent use of the guide element.

[0035] In one variant of the present invention, a lattice structure is produced using a molten layer tool in an additive manufacturing process, and a grid pattern of dots is deposited on the surface from a molten plastic material. By extrusion with a nozzle and subsequent curing by cooling at the desired location, a load-bearing structure is produced, particularly in the form of a lattice and / or honeycomb. The support areas of the guide elements are produced with particularly high load-bearing capacity so as to form voids, so that the guide elements have considerable strength and at the same time low mass. The guide elements are typically stacked by repeatedly advancing line by line on the work surface, and then moving the work surface upward in a stacking manner, as a result of forming the support areas of the guide elements.

[0036] In a particularly advantageous variant of the present invention, the contact surface of the guide element with the fluid is produced from the build-up material by continuously melting and solidifying layers using radiation. The different properties of each region of the guide element are generated in this case by variations in radiation. By intentionally controlling the local introduction of heat, the material properties change even during the build-up of the guide element. As a result, it is possible to produce zones and microstructures of various material states and thus various properties within a region of the guide element, which is chemically homogeneous.

[0037] The metal buildup material is applied thinly to a plate in powder form. The powder material is locally and completely melted at the desired location using radiation, and after solidification, forms a solid material layer. This base plate is then lowered by the thickness of the layer, and the powder is applied again. This cycle is repeated until all layers are produced. Excess powder is removed from the completed guide element.

[0038] The process according to the present invention is characterized in that the guide device can be configured in particular on an individual basis. The suitability of the guide device according to the requirements of the centrifugal pump can be considered by generative manufacturing. The expensive individual manufacturing becomes significantly more cost-effective as a result of a relatively low-cost hybrid configuration of components manufactured by conventional methods and components manufactured generatively. In addition, generatively manufactured components can achieve higher pump efficiency and can have shapes that were not possible with conventional manufacturing methods.

[0039] Ideally, the guide device is produced in a hybrid form from generatively manufactured components and at least one conventionally manufactured component, and is used as a guide device for centrifugal pumps, particularly for high-pressure segmented pumps. The guide device is characterized by excellent fluid-mechanical properties.

[0040] Advantageously, a multi-stage high-pressure segmented pump can be formed by successively connecting guide devices according to the present invention, each comprising a casing cover and a corresponding impeller. This series connection can be flexibly shortened or lengthened to accommodate changes during operation.

[0041] Further features and advantages of the present invention will become apparent from the description of exemplary embodiments with reference to the drawings, and also from the drawings themselves. [Brief explanation of the drawing]

[0042] [Figure 1] This diagram shows a conventional multi-stage centrifugal pump. [Figure 2] This is a perspective cross-sectional view of the guidance device. [Figure 3] This is a schematic diagram of the guidance elements. [Modes for carrying out the invention]

[0043] Figure 1 shows a known multistage centrifugal pump 1 in a horizontal setup. Vertical or oblique setups are also possible. In a variation of this embodiment, the shaft 3 is equipped with five impellers. Fluid flows into the pump inlet 2 and exits the pump through the pump outlet 4. The fluid to be pumped, for example, a low-boiling-point, gaseous, or flammable fluid, flows toward the first pump stage, which has a radial impeller 5. This first impeller 5 acts as a suction impeller, carrying the fluid into a guide device 6, and the impeller 5 and guide device 6 are surrounded by a casing 7. The casing 7 and guide device 6 form a unit in the form of a barrel casing, from which the name barrel-casing pump is derived. The guide device 6 is equipped with return guide vanes, and the fluid is carried by the return guide vanes to another pump stage having another impeller. The impellers and guide devices each form a unit, a so-called pump stage, within the multistage pump assembly.

[0044] Figure 2 shows a perspective cross-section of the guide device 23 according to the present invention. The guide device 23 comprises casing covers 18 and 20 that form part of the centrifugal pump casing 22. The casing cover 18 has a fitting element 21 into which an element 24 (not shown in this figure) engages. The guide device 23 further comprises a guide plate 19 and, for example, one guide element 17. Device 23 comprises three or more, preferably four or more, particularly five or more, and / or less than 24, preferably less than 22, particularly less than 20 generatively manufactured guide elements 17.

[0045] The casing cover 20 completely surrounds the impeller (not shown) radially and receives the discharge fluid from the impeller. The guide element 17 deflects the fluid flow with its radially outward curved shape and flow-guiding forming portion 25, while reducing vortices. As a result of the optimized flow shape of the guide element, the guide element 17 avoids vortex buildup and flow separation, and thus contributes to improving the efficiency of the centrifugal pump 1.

[0046] The guide device 23 is a part manufactured by a conventional method. That is It is a hybrid component consisting of a guide plate 19 and casing covers 18 and 20 and a generatively manufactured guide element 17. Thus, the hybrid structure of the guide device 23 combines the advantages of each manufacturing process to achieve the optimal efficiency of the centrifugal pump 1 according to the present invention.

[0047] Figure 3 shows a schematic diagram of a guide element 17 with a radially outward curved shape. The generatively manufactured guide element 17 has a formed section 25 for improved flow guidance and a sealing element for a gapless connection to a guide plate 19 (not shown). An element 24 for engaging with a mating element 21 (not shown) enables a plug-in design for a hybrid form of guide device 23.

[0048] The pre-formed portion 27 of the guide element 17 receives the discharge flow from the upstream impeller (not shown) and guides the discharge flow to the second molded portion 28 in a particularly low-loss manner. The second molded portion, together with the guide plate 19 shown in Figure 2 and the adjacently positioned guide element 17, forms a flow path. The fluid flows from this flow path to the downstream impeller in a particularly vortex-free manner. Thanks to generative manufacturing, the molded portion 25 of the guide element 17 has a particularly thin and fine radius of curvature, thereby significantly improving the overall efficiency of the centrifugal pump.

Claims

1. A centrifugal pump (1) having at least one impeller (5, 9) surrounded by a casing (22), wherein the casing (22) includes at least one guide device (23), The guide device (23) is configured as a hybrid component comprising at least one conventionally manufactured component and at least one generatively manufactured component, The at least one generatively manufactured component is configured as a guide element (17), The above-mentioned component manufactured by at least one conventional method is configured as a casing cover, and the casing cover has a fitting element (21), A centrifugal pump (1) characterized in that the guide element (17) has an element (24) for engaging with the fitting element (21), and when the guide device (23) is assembled, the element (24) is engaged with the fitting element.

2. The centrifugal pump according to claim 1, characterized in that the guide device (23) has three or more and / or fewer than 24 generatively manufactured guide elements (17).

3. The centrifugal pump according to claim 1 or 2, characterized in that the generatively manufactured components have a shape that is curved radially outward.

4. A centrifugal pump according to any one of claims 1 to 3, characterized in that the generatively manufactured components have a flow-guiding forming section (25).

5. The centrifugal pump according to any one of claims 1 to 4, characterized in that the generatively manufactured components surround a guide plate (19) which is positioned adjacent to the guide element (17) and together with the guide element forms a flow path with virtually no gaps.

6. The centrifugal pump according to claim 5, characterized in that the generatively manufactured component has a sealing element (26) for gapless connection to the guide plate (19).

7. The centrifugal pump according to any one of claims 1 to 6, characterized in that a component manufactured by a conventional method is configured as a guide plate (19) which is arranged adjacent to the guide element and forms a flow path together with the guide element.

8. A process for manufacturing a centrifugal pump (1) according to any one of claims 1 to 7 using an integrated manufacturing unit, The steps include forming a guide plate (19) which is positioned adjacent to the casing cover (18, 20) and / or the guide element and forms a flow path together with the guide element, by primary molding and / or cutting, The steps include forming the guide element (17) by a generative process, The steps include fitting the guide element (17), the guide plate (19), and the casing cover (18, 20) together to form a hybrid guide device (23) for the centrifugal pump casing (22), and A process that has

9. Use of a hybrid component having at least one generatively manufactured component and at least one conventionally manufactured component as a casing (22) having an integrated guide device (23) for a centrifugal pump (1) according to any one of claims 1 to 7.

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