EP3175119B1 - Flow conducting machine part - Google Patents

Description

The present invention relates to the geometric design of a flow-guiding component with special consideration of the mechanical load, wherein the component transitions between individual areas are affected by notches, the load collective of the notches can be calculated, and the production of such a component.

Flow-guiding components are known in various embodiments. Depending on the conditions of use, ie working pressure, pumped liquid, medium temperature or similar, the component is made of special materials. The static structure of the housing is also heavily dependent on the application.

Particularly stressed areas and, above all, at the transitions between different areas, special mechanical stresses can be built up, resulting in shortened service life. By an advantageous embodiment of the notch tensions can be greatly reduced, but this requires a processing of the transition region with tools.

The EP 1 785 590 A1 shows the design and manufacture of an impeller of a pump or turbine, with particular attention is paid to the design of the notches. The impeller is welded in several layers, whereby voltages are directly suppressed. The procedure requires access to the notches during manufacture with appropriate tools.

Both casting technology and joining technology are rapidly reaching their limits for fluid-conducting components, as some of the notches are difficult and / or not directly accessible on the outside. This leads to considerable limitations in the design of the geometry of the component.

DE 10 2012 106810 A1 . JP 2009 185733 A and US 2004/062636 A1 also describe generic designs of such notches.

The object of the invention is to find and apply a geometric design for the mechanical load at the transition points of a flow-guiding component, especially in the region of the notches, which is simple and inexpensive to produce.

The object is achieved by an article according to claim 1.

The advantage here is that the flow-leading part, which may be an impeller for a centrifugal pump, for example, can be constructed free of classical specifications. Limitations of foundry technology and / or joining methods need not be taken into account in the design of the component, since only the mechanical and hydraulic properties are important. Such an exemption from traditional design principles allows a completely new design of the impeller.

This simple construction method makes it very easy to determine a geometry that takes into account the mechanical load in the component, depending on the direction. Attacking forces are analyzed under the influence of the conveyed medium and the intended working conditions, whereby minimum and maximum values are determined. According to these values, the demand of the impeller for mechanical stability is determined. The calculation method specifies the geometric design and thus also the material usage and the workpiece machining.

In an advantageous embodiment, the flow-guiding component is produced by a generative method, in which, in particular, metal powders are joined to form a component by a jet melting method, such as, for example, laser or electron beam melts. This has the advantage that the impeller is very simple and yet very stable to produce. The methods mentioned make it possible to produce fluid-tight components with a high degree of detail. In addition to this, the components can additionally be given a special surface structure, for example a shark skin, which additionally improves the mechanical and hydraulic properties.

In a further advantageous embodiment, at least one notch is arranged in the interior of the component in the flow-guiding component, in particular in a cavity and / or an undercut. This has the advantage that points in the geometric configuration of the component can be advantageously formed, which are not accessible to the mechanical post. This detailed embodiment allows the production of mechanically stronger components with less material use.

In a further embodiment, the flow-guiding component is a pump component, in particular a centrifugal pump. Of advantage is the geometric design, in particular in wheels and / or guide wheels of centrifugal pumps. These parts are particularly heavily mechanically stressed. The transitions between a guide / impeller blade and a cover plate are sometimes very difficult to access. In the case of a centrifugal pump impeller, of course, in addition to the pure geometric coarse structure, the surfaces of the individual impeller blades can also be designed freely, so that the boundary layer between the impeller and the fluid can be influenced. Among other things, it is also possible for inducers to make components hollow, whereby considerable material savings are possible. The component must then its mechanical stability by the appropriate design of the struts obtained within the cavities, as well as the transitions between mechanically stabilizing areas according to the above design rule.

In a further advantageous embodiment, the component is made of an iron-based material. This allows a simple and cost-effective production on already large-volume tools. Advantageously, the iron-based material is an austenitic or martensitic or ferritic or duplex material. This allows the production of corrosion-resistant components. The preparation of the powders required for the high-energy jet methods mentioned is likewise inexpensive and simple. This becomes even clearer when the iron base material is advantageously a gray or nodular cast iron material.

Reference to an embodiment of the invention will be explained in more detail. The drawing 1 shows the method according to the invention for constructing the notch between two regions of a flow-guiding component. Drawing 2 explains the application of the method according to the invention for the construction of a centrifugal pump impeller, as well as the advantages of a generic production.

The FIG. 1 shows an arbitrary point at which the contour of a component changes discontinuously from a first region 1 into a second region 2, wherein the two regions enclose an angle 3. Significant stresses develop at this point of discontinuity, which can be strongly influenced by a suitably constructed geometric course. In the case of a predetermined breaking point, one would like to use the stresses to allow the component to be selectively crushed at the point of discontinuity during a threshold load. In most cases, however, the opposite is desirable and the point of discontinuity should be sufficiently resilient against the applied forces. Traditionally, a so-called engineering notch is provided here, which forms the sharp angle by a rounding with a selected radius.

On the basis of various observations in nature, a method has been developed for the design of the notch, which is easy to construct and yet absorbs the force at the point of discontinuity so that the loads of the component can be greatly reduced with minimal design and manufacturing costs. For this purpose, an angle bisector 4 is constructed by the angle 3. A point 5 is selected on this bisector 4. By this point 5 are perpendicular to the areas 1 and 2, the lines 6 and 7 laid. To these straight lines 6 and 7 will be at point 5 at an angle of 8 to 45 ° straight lines intersect the areas 1 and 2, wherein in the area 2 of the intersection 11 is set. The distance between the point 5 and the point 11 is halved, whereby the point 9 is obtained, to which a straight line is applied at the angle 10 to 22.5 °, which intersects the area 2 at point 13. The distance between the point 9 and the point 13 is again halved, whereby one obtains the point 12, to which a line is applied at the angle 14 to 12.2 °, which intersects the area 2 at the point 15. The envelope of this construction results in a contour having various points of discontinuity. This would be rather disadvantageous for a machining operation. In a generative manufacturing process, where the workpiece is created by juxtaposing individual volume elements or material layers, that is, where work is done in discrete units, such a construction can be ideally converted into a workpiece.

The proposed construction is based on a non-symmetrical loading of a component. If the component were loaded symmetrically, for example by an alternating left / right rotation, then the construction could be symmetrically supplemented in the direction of the first region 1 in an analogous manner.

The FIG. 2 shows an exemplary application for the construction and manufacturing method according to the invention. In the FIG. 2a an impeller 16 is shown, as used for example in a centrifugal pump. The impeller 16 has a hub portion 17 and a cover plate 20. More details are the FIG. 2b refer to. Here are the impeller blades 18 and another cover disc to see. Such an impeller with the two shrouds 20 and 19 is referred to as a closed impeller. The impeller blades 18 have, both in the region of the impeller hub 17 and in the region of the cover disks 19 and 20, transitions 21 and 22, respectively, which correspond to those in FIG FIG. 1 correspond described. In the region of the cover disk 19, the transition 21 can be described such that the surface of the cover disk 19 represents the first region 1 and the impeller 16 the second region 2. The forces occurring at the point of discontinuity between the two areas 1 and 2 can be determined from the parameters of the impeller, the fluid of the pump and the application. Based on these forces, the point 5 is set in the notch to be constructed. With this point, the notch is constructed. If the impeller 16 is made, for example, in a 3d printing process, the contours of the transitions 21 and 22 at each point of the impeller can be determined with the accuracy of the resolution of the printing process be prepared without any reworking will be necessary. This particularly advantageous contour, which would not be produced with a corresponding shape fidelity with conventional machining methods, can even be constructed in places that would not be attainable with tools for post-processing, which is apparent from the FIG. 2 initially not directly derivable.

The proposed design and manufacturing principle combines the effect of a generic 3d printing production process, which inherently works with discrete elements in which individual voxels or layers are joined to a workpiece with a method of optimizing a non-continuous surface geometry. As a result, it is possible to dispense with further post-processing of the workpiece, during which the individual layers of production must be "smoothed" to form a continuous body.

The application with the shown closed impeller already shows the advantages in the production and the potential for material saving with careful construction. Particularly advantageous method of the invention can be applied in an interior, which is no longer accessible from the outside after the production of the blank. LIST OF REFERENCE NUMBERS 1 First area 12 Point 2 Second area 13 Point 3 angle 14 Angle to 12.25 ° 4 bisecting 15 Point 5 Point 16 Wheel 6 Right angle 17 impeller hub 7 Right angle 18 impeller blades 8th Angle to 45 ° 19 cover disc 9 Point 20 cover disc 10 Angle to 22.5 ° 21 crossing 11 intersection 22 crossing

Claims (9)

1. Flow-conducting component, wherein in the component transitions between individual regions have notches, wherein the load spectrum of the notch can be established arithmetically, wherein the notches which are directly accessible from the outer side only with difficulty and/or not at all are geometrically formed in accordance with the mechanical stress thereof; characterized in that
   the notch is constructed in such a manner that a transition in the component from a first region (1) to a second region (2) encloses an angle (3), wherein the angle bisector of the angle (3) is established, wherein along this angle bisector a first point (5) is determined, wherein in each case a perpendicular (6, 7) from one of the regions (1, 2) which form the angle (3) is dropped from the first point (5), wherein there is placed through the first point (5) to each perpendicular a straight line with an angle (8) of 45º, wherein as a result of the intersection of the straight line, which is placed at the perpendicular (7) from the second region (2), with the second region (2) there is determined a path whose center determines a second point (9), wherein, at the second point (9), a straight line with an angle (10) of 22.5º is placed on the path which intersects the second region (2) at a third point (13), wherein the envelope of this construction predetermines the geometric configuration of the notch.
2. Flow-conducting component according to Claim 1, characterized in that the component is produced using a generative method in which in particular metal powders are connected to form a component by means of a beam melting method, such as, for example, laser or electron beam melting.
3. Flow-conducting component according to one of the preceding claims, characterized in that at least one notch is arranged inside the component, in particular in a hollow space and/or an undercut portion.
4. Flow-conducting component according to one of the preceding claims, characterized in that the component is a pump component, in particular of a centrifugal pump.
5. Flow-conducting component according to one of the preceding claims, characterized in that the component is a centrifugal pump impeller.
6. Flow-conducting component according to one of the preceding claims, characterized in that the component is an inducer.
7. Flow-conducting component according to one of the preceding claims, characterized in that the component is produced from an iron-based material.
8. Flow-conducting component according to Claim 7, characterized in that the iron-based material is an austenitic or martensitic or ferritic or duplex material.
9. Flow-conducting component according to Claim 7, characterized in that the iron-based material is a grey cast iron or a spheroidal graphite iron material.

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