HK1032765B - A method for producing matched fluidic surfaces - Google Patents

Description

Method for matched surface processing conforming to fluid technology

Technical Field

The invention relates to a method for producing a matching, fluid-technical surface on a rotor unit with integral blades.

Background

The blades of rotor units with integral blades, which are connected to the hub in a rational and seamless manner, for example by welding, forging, brazing or gluing, are generally used more and more for advanced turbomachine designs, owing to the advantages in terms of strength, weight and structural volume. The present invention is primarily concerned with the replacement of the form-fitting turbine blade fastening (for example, fastening with a fir-tree blade profile or a dovetail profile) which is generally customary in rotors which are substantially axially through-flowing. As already recognized, both blade attachment/blade mounting and blade repair/blade replacement are expensive and difficult for rotor units with integral blades compared to form-fitting designs. There is therefore a need to improve or develop new machining and repair methods, where linear friction welding provides a particularly significant and important paradigm. Although named welding, this method of joining is less metal-technically than it is classified as welding, as forging. Another joining method is induction welding, in which a "forge joint" of fine particles is likewise produced by means of joining pressure on the basis of induction heating.

Soldering and bonding methods are also possible in principle, but at least in the joining zone, thermal and mechanical "weaknesses" are formed.

The real joining methods all require that at least one of the parts to be joined has a margin at the joining zone. This requirement can be achieved in the form of component clamping and force transmission, as in the case of linear friction welding, or by the criterion that the joining zone should be completely reworkable, in particular in order to compensate for geometric joining errors. The material which normally occurs during the joining process itself (e.g., "flash" in friction welding) must also be removed in the end. In each case at least the joining zone is reworked and optimized by material removal on its surface contour, taking care here to comply with the fluid-technical and strength requirements. Furthermore, the surface to be machined is adapted to the actual surface, which must be taken into account for this purpose from the measuring-technical point of view. In the modern high-efficiency machining field, the measured values are stored in accordance with a calculation technique, the surface to be machined is spatially calculated and shaped by mechanical removal, all three steps "measuring", "calculating" and "machining" being based on interrelated data processing.

A method for repairing worn blade tips of compressor and turbine blades is known from european publication EP 0837220 a2, in which the worn blade tips are removed at a defined radial height h and replaced by a repair contour that is exactly adapted to the contour, the fixing of which is effected by soldering or welding. After the worn portion has been removed, the actual geometry of the remaining blade at the break-away surface, and at the same time also at the subsequent joining surface portion, is measured and, on the basis of these measurements, machined to an exactly matched repair contour, preferably by laser cutting under three-dimensional cutting control. Furthermore, the remaining blade surface is continuous in a tangential straight line all the way from the break-away/joining surface with the repair contour in the radial direction up to the blade tip. If this is the case, only a rework at the braze or weld is required. The advantage of omitting a negligible reworking is not to be confused with the advantage that the blade can be used again after the partial repair without having to be replaced. This method of providing a special form of "repair" is also suitable for rotor units with integral blades, but only for repairs at the tip of the blade. The method limits the possibility of producing only matching surfaces whose profile lines are straight in the height direction (by means of linear laser cutting) and do not adapt to any spatial curvature, such as the transition from blade to hub. The laser machining of the surface contour of the repair part to the final dimensions must be carried out before it is fixed to the remaining blade, so that geometric joining errors can hardly be compensated for any longer (no workable margin exists). Machining of the repair part/patch to the final dimensions by laser cutting after joining is not possible, since the laser radiation cutting radially to the center from the blade tip will at least partially penetrate and damage the remaining blade.

German laid-open publication DE 4014808 a1 relates to a machine recognition system/vision system for automation of machining processes. The system can be particularly applied to the dressing of worn turbine blade tips by laser-flux-overlay welding. The blade tip has a special geometry, wherein a thin, circumferential blade outer wall projects radially beyond the end face itself. The projecting blade walls are subjected to wear when rubbed through the turbine casing or casing lining, which wear can be removed by overlay welding. The worn blade wall-end edge is first smoothed, i.e. leveled and smoothed. The shaped ring surface formed by the end edges is determined by means of a camera by means of optoelectronics and converted into a mathematical ring curve with a locally determined thickness (width). The data are used directly for controlling the welding process, wherein the local material coating (flux, laser intensity) is adapted to the current remaining blade wall thickness. This results in the defect being continued by the material coating with at least the adjacent flat end face into an outer and inner actual contour, wherein a certain reworking is absolutely necessary.

The repair of blade tips and blade edges by welding is described in the German journal "Werkstatt und Betrieb" at stage 129 (1996) at page 672-. The space actual curve of each blade close to the welding seam is divided into a plurality of segments to be scanned and stored. The actual curve is continuously calculated to the welding position and processed by numerical control equipment. Wherein special geometries on the blade tip, such as curved or bent profile lines, may also be considered. For example, such a special geometry on the main blade is scanned and stored. "intelligent" compensation between the actual geometry with error and the master blade geometry is also suggested. Nevertheless, no visual indication is available to the expert, how this compensation should be achieved.

In rotor units with one-piece blades, the geometry area for the matching surface finish may extend over the entire ring chamber height, i.e. from the hub up to the blade tip. The first application case in this case is the processing of new components, in the context of which the blades, preferably the majority of the already processed blades, are connected to the hub by a joining technique and are formed flat with matching surfaces at least in the region of the joining region next to the hub.

Wear and damage may occur during operation of the rotor, which requires repair. In the most severe cases the entire blade will be replaced, while in more cases only a large or small part or portion of the blade will be replaced. The leading and trailing edges of the blades and the blade tips are of course replaced in most cases. The damaged portion is removed, for example by laser cutting, and replaced with a component or patch with a margin. If the material of the blade is only slightly damaged, it may be sufficient to apply only a coating of the material with a margin, for example by laser flux surfacing, without the need to completely replace the component. In practice, the combination of "blade replacement", "blade component replacement/repair" and "material coating" is more relevant, since different damage patterns can occur over a longer period of operation.

Disclosure of Invention

In view of this situation, the object of the present invention is to provide a matched, fluid-technical surface finishing method on rotor units with integral blades, which is also suitable for new component finishing and repair, which can be applied to the entire blade surface up to the immediate vicinity of the hub, including the transition region up to the hub, which allows the formation of an arbitrarily curved, step-free and knee-free surface, taking into account the minimum curvature, which allows different forms of material removal and joining or material coating to be carried out before this, which method can be operated particularly precisely, rapidly and economically.

According to the invention, a method is provided for machining matching, fluid-technical surfaces on a rotor unit with integral blades, the rotor having a hub and at least one blade flange, mechanically removed after a proper bonding of the at least one blade to the hub and/or the at least one blade part to the at least one blade material and/or after a proper, local coating of the material, wherein at least one of the components or a part of the material coating has a margin in each case wholly or locally in the region of the joining region before removal, in which at least one actual surface, called the local component contour, is determined by means of a measurement technique, and a fluid-technical surface, which is matched to the actual surface and which effectively forms a joining zone in accordance with the fluid technology and the machining technique, is machined, characterized in that:

A) the measurement-technical determination of the at least one actual surface and the machining of the at least one matching surface are carried out on the machining device under constant clamping conditions of the rotor unit, i.e. in a relevant measurement, calculation and machining cycle;

B) the theoretical surface of the theoretical profile in the radial circumscribing theoretical position from the blade tip up to the respective site to be machined close to the hub is formally processed into stored data that can be used by the machining equipment;

C) from at least one actual surface determined by measurement techniques, which extends into the vicinity of the joining zone and which contains errors for the most part in terms of its geometrical dimensions, the actual surface is calculated as the surface extending over the joining zone and is machined by removal, in each case according to the following criteria:

a) the surface to be machined, which corresponds to the fluid technology, approaches each point tangentially as far as possible in a very continuous manner, i.e. without points of inflection and steps, approaches at least one actual surface in a straight line and/or with a locally variable predeterminable minimum curvature and/or approaches a first theoretical repair surface, wherein the repair surface is defined and machined in the component at a locally variable predeterminable minimum distance from the measured actual surface;

b) the surface to be machined, which corresponds to the fluid technology, corresponds to the greatest possible extent to a mathematically continuous, solid, at least largely curved surface, which has a locally and/or variably direction-dependent predefinable minimum curvature at each point,

c) at each point, the surfaces to be machined at these points, which surfaces are in accordance with the fluid technology, may not or not completely correspond to the theoretical surfaces of the theoretical profile in the radial circumscribed theoretical position due to a) and/or b) and/or local component deviations, and the surfaces, taking into account the mathematical continuity, approach the local theoretical profile stored in the form of data at the respective radial height to the greatest possible extent.

According to step A), the measurement technique is determined and processed on a processing device while the rotor unit is constantly clamped in a cycle. Therefore, the processing precision is improved, and the processing period is shortened.

Based on step B), the machining device "identifies" the theoretical surfaces of the respective regions to be machined and the optimal, striving-to-achieve component contours.

The measured technical actual data and the given theoretical data are first systematically converted into a computationally technical, spatial surface and then into a realistic surface of the workpiece in accordance with step C), wherein steps a) to C) define details. Step a) defines the transition between the surface to be machined and the actual surface or so-called repair surface, which is entirely fixed within the actual surface of the component and is machined. Step b) defines the range characteristic of the surface to be machined, wherein the numerical/theoretical requirements are as good as practical for the implementation of the machining technology, i.e. for the cost thereof.

Step c) takes into account the situations in which the theoretical surface (theoretical profile in the theoretical position) cannot or cannot be completely manufactured but is as close as possible to the theoretical surface in relation to the theoretical position.

It is clear to the expert that realistic machining processes, limited by hardware and software conditions, can lead and often lead to deviations from the theoretical/mathematical requirements. But such deviations can be minimized and kept within acceptable, negligible orders of magnitude that comply with fluid technology and strength requirements by reliable and accurate machining techniques. For example, there may be minimal steps, streaks and inflection points on the machined surface, although a theoretically exactly straight, smooth surface course has already been given at these points.

The invention is explained in detail below on the basis of the figures. A very simplified, not to scale, diagram is given here.

Drawings

Fig. 1 is a partial cross-sectional view of a rotor unit with one of several blades, the profile of which has been mostly machined before joining,

fig. 2 is a comparative partial cross-sectional view of a replacement part with a margin, from which a blade is machined,

figure 3 is a side view of a repaired blade,

figure 4 is a longitudinal view of section a-a in figure 3,

FIG. 5 is a blade tip region with a material coating.

Detailed Description

From the rotor unit 1 with integral blades in fig. 1, a part of the hub 4 and a part of the blades 7 can be shown. The blades 7 are preferably fixed by linear friction welding to projections in the form of projections on the hub 4 and have, at the radially inward bottom end, thickened bodies 11 for handling and force transmission. The junction area 14 is indicated by hatching. The blade 7 is fixed in a geometrically incorrect manner as is clear from the intentionally exaggerated illustration. For example, the blades exhibit not only a lateral offset to the right with respect to the hub 4 but also an angular error, i.e. a tilt to the right deviating from the radial direction.

Fig. 1 shows the conditions that may occur in the machining range and repair range of a new component, wherein the identification on the left side of the blade by a letter and number combination is related to the repair condition, and the identification on the right side is related to the machining of the new component.

The surface of the blade 7 should have been machined as far as possible before the joining, for example by precision forging, and thus establish the actual surfaces I1 or I3, which as standard surfaces are not allowed to be altered or damaged any more. At a point above the thickened body 11, this actual surface is determined by a measuring technique, the indications M1 and M3 of the positions given here by dot-dash lines representing measuring zones which determine the actual surface locally in a planar manner, in order to determine the profile course in the longitudinal and transverse directions and the profile change in the radial direction. The measuring field is not a straight line, for example, not a straight line around the contour in radial height, but is often a planar area. The dashed and dotted lines here merely indicate approximate, average height positions of the measurement regions M1 to M3.

The actual surface I2 between the joining zone 14 and the hub 4 in the repair situation (left) is determined at the measuring zone M2.

Such a mutually connected, matching surface O1 between the actual surfaces I1, I2 is machined, which surface has a step-free and inflection-free transition into the actual surface and which itself is also step-free and inflection-free and continues as precisely as possible, taking into account the local and direction-dependent predeterminable minimum curvature. Furthermore, the "precondition" of the theoretical contour preceding the theoretical position is also valid if necessary. The machining criteria and geometric joining errors according to the invention result in a gentle S-shaped curved surface O1 course in the radial direction, wherein the excess material to be removed is drawn in the form of pockmarks.

The situation is similar for the new part machining (right side). But here only in the measuring region M3 above the thickening 11. The projection in the form of a projection on the hub 4 should have a margin in the new component state, so that the matching surface O3 transitions from the upper actual surface I3 down to the theoretical surface S3, where the theoretical surface is likewise machined. The transition of the surface O3, which is matched at a certain radial height, to the theoretical surface S3, although this cannot be indicated as a whole, has the tendency that the deviation of the transition region from the theoretical value is achieved as little as possible, taking into account the minimum curvature.

Fig. 2 shows a repair situation of the rotor unit 2, in which case in fact a complete blade is replaced by a spare part. The actual contour I4 between the joining zone 15 and the hub 5 is determined in the measuring range M4 around the "convex contour" by means of a measuring technique. The overall distance from the measured actual surface I4 defines a so-called repair surface R on the component. The machining of the mating surface O4 starts from the repair surface R and transitions to the theoretical surface S4 with as little radial height as possible, which continues up to the not shown blade tip. The repaired surface R is also machined during this cycle, either before or after the surface O4 in time. Here three forms of surfaces (O4, R, S4) were machined, with O4 producing matching surfaces. All surfaces together constitute the profile of the actual blade 8, where more excess material is removed. The corresponding advantage is that the manufactured blade 8 corresponds as closely as possible to the theoretical value, i.e. is very precise.

Fig. 3 and 4 relate to so-called repair patches, i.e. the replacement of a blade part with a replacement part, which in general leaves an allowance over the entire surface. Fig. 3 shows a blade 9 of the rotor unit 3, here a side view of a turbine blade as seen in the circumferential direction, where the hub 6 is again shown in partial detail. The leading edge of the blade 9 is removed over a large part of its radial height towards the blade tip 12 by a planar, upwardly right-inclined cross section and is replaced by a welded-on repair patch 18, which is more or less rough in shape and which leaves the entire margin close to the blade contour and which can be cut, for example, from a rectangular bar or thick sheet. The junction area 16 is indicated by hatching.

Fig. 4 shows an axial/tangential view of the section a-a in fig. 3, in which the blade profile can be seen. The part of the blade 9 located to the right of the joining region 16 is given in its shape beforehand and is not modified. The actual surface I5 of the blade is determined in a measuring zone M5 on both sides of the contour near the joining zone 16, in order to be able to adapt to the region of the contour to be machined-to the left from the joining zone 16. This is not always possible, as the matching surface O5 should transition to the theoretical surface S5, i.e. the theoretical contour of the theoretical position, in as short a route as possible. At least the surface to be matched is as close as possible to the theoretical surface, wherein the matching of the theoretical contour, i.e. of the theoretical shape, is more important than the matching of the theoretical position (theoretical contour before the theoretical position). The repair patch in the form of fig. 3 and 4 can in principle be at various points of the blade-wherein the repair patch may also be located in the middle of the blade-for example with a circular disc fitted into a corresponding hole in the blade. It is therefore clear that the joining zone is also curved, preferably semicircular, and can close itself, for example to a full circle. The repair patch is usually a replacement part which has a defined shape and at least partial margins for the purpose of extending over a large volume to eliminate blade damage.

In contrast, damage forms exist in which the blade material is eroded primarily at the surface region, for example by mechanical rubbing over the stator part, by corrosive particles in the gas flow or by the corrosive hot gas itself. After the "polishing" of the damaged component surface, which is removal-type, the missing material can be coated in an "amorphous" form more effectively, in particular by welding or soldering in the molten state. A very desirable method of machining components with relatively low thermal stress is laser-flux-deposition welding.

FIG. 5 illustrates repair by material coating with a blade 10 having a renewed tip 13. It can be seen that the material 19 has a margin both laterally and above. The illustration should correspond to a partial cross-sectional view through the blade as seen parallel to the rotor axis. The hatched joint 17 at the upper end of the shortened blade 10 must extend exactly over the entire cross section of the material coating 19 when it is completely plated by welding techniques. The hatching is omitted as much as possible in order to be able to show further details of the interior of the material coating 19 in a more specific manner. The lower actual surface I6 at the joining zone 17 is determined around the blade profile at the measuring zone M6 for data-technical processing. The matching surface O6 is machined, which surface transitions to the theoretical surface S6 or matches as closely as possible to the theoretical surface (here also: "theoretical surface before theoretical position"). A particularly simple method for machining the mating surface is the possibility of the actual surface, here I6, at each point being extended around a straight line of the contour upwards towards the tangent of the blade tip 13, i.e. mathematically given a minimum curvature "infinity" (∞) in the height direction. This is only of significance if the radial height of the material coating is small, i.e. if the transition region in the direction of the theoretical surface or the theoretical contour is not practically achievable. Furthermore, how severely the actual surface near the junction deviates from the theoretical surface plays an important role.

Also shown in fig. 5 is an additional theoretical surface S7, shown in dashed lines, whose relationship with respect to S6 is an ancillary, defined material removal (less pock). This is associated with the suggestion that the blade has a stepped profile change towards the tip, by which "minicontour" the transition to a very thin profile takes place with a thickness that is as constant as possible over the entire length and corresponding to the curvature of the blade back.

Claims (11)

1. Method for machining a matching, fluid-technical surface on a rotor unit with integral blades, with a hub and with at least one blade flange, which is mechanically removed after the at least one blade has been materially bonded to the hub and/or at least one blade part with the at least one blade and/or after a materially bonded, local material coating, wherein at least one of these parts or a part of the material coating has a margin in each case in whole or in part in the region of the bonding zone before removal, wherein at least one actual surface, referred to as the local part contour, is determined by means of a measurement technique, and a fluid-technical surface matching the actual surface, which is effective to form a bonding zone in accordance with the fluid technology and the machining technique, is machined, characterized in that:

A) the measurement technology of the at least one actual surface (I1 to I6) determines that the machining of the at least one mating surface (01, 03 to 06) is carried out on the machining device under constant clamping conditions of the rotor units (1, 2, 3), i.e. in a relevant measurement, calculation and machining cycle;

B) theoretical surfaces (S3 to S7) of the theoretical profile at a radially circumscribed theoretical position from the blade tip (12, 13) up to the respective site to be machined close to the hub (4, 5, 6) are formally processed into stored data which can be used by the machining device;

C) the actual surfaces (I1 to I6) which are determined from at least one measuring technique and extend in the vicinity of the joining zones (14 to 17) and which contain errors for the most part in terms of their geometric dimensions are each calculated as surfaces (01, 03 to 06) extending over the joining zones (14 to 17) according to the following criteria and are machined by removal:

a) the fluidic surfaces (01, 03 to 06) to be machined are tangentially approached as far as possible in a very continuous manner to each point, i.e. without points of inflection and steps, in a straight line and/or with a locally variable predeterminable minimum curvature to at least one actual surface (I1 to I6) and/or to a first theoretical repair surface (R), wherein the repair surface is defined and machined in the component at a locally variable predeterminable minimum distance from the actual surface (I4) being measured;

b) the surfaces (01, 03 to 06) to be machined, which are in accordance with the fluid technology, correspond to a mathematically continuous, solid, at least largely curved surface, which has a locally and/or variably directionally dependent predeterminable minimum curvature at each point,

c) at each point, the surfaces (01, 03 to 06) to be machined at these points, which surfaces are in accordance with the fluid technology, may not or not exactly correspond to the theoretical surfaces (S3 to S7) of the theoretical profile in the radial circumscribing theoretical position due to a) and/or b) and/or local component deviations, the surfaces (01, 03 to 06) approaching the local theoretical profile stored in the form of data at the maximum possible radius heights, taking into account the mathematical continuity.

2. The method according to claim 1, for the case of blades in the machining area of new components, the hydrodynamic contour of which has been largely machined before the joining with the hub, is characterized in that the respective blade (7) is determined by measurement techniques as a machined actual surface (I3) (M3) radially outward and close to the joining region (14), while a matching hydrodynamic surface (03) is machined from the measured actual surface (I3) radially toward the center into a theoretical surface (S3).

3. The method as claimed in claim 1, for the case of blades in the repair sector of new-component machining or replacement blades, the hydrodynamic contour of which has been largely machined before the joining with the hub, is characterized in that a machined actual surface (I1) radially on the outside and close to the joining region (14) and an actual surface (I2) between the joining region (14) and the hub (4) are respectively determined (M1, M2) with measurement technology and are machined between the two actual surfaces (I1, I2) to form a matching hydrodynamic surface (01).

4. A method according to claim 1, applied in the case of the use of at least one component in the repair area of a replacement blade, the profile of which component is left entirely as large as the theoretical profile conforming to the fluid technology, characterized in that an actual surface (I4) between the joining zone (15) and the hub (5) is determined (M4) by measurement techniques, respectively, that a repair surface (R) is defined in the component, which repair surface (R) is located at a distance from the actual surface (I4) radially outwards from the repair surface (R) and is machined to a surface (04) which transitions to the theoretical surface (S4) with as little height as possible, that the profile conforming to the fluid technology of the blade (8) is continuously machined to the theoretical surface (S4) by removing flattening everywhere, and that the repair surface (R) in the direction of the hub (5) is produced by removing machining.

5. The method according to claim 1, applied in the case of the use of at least one component in the repair area with replacement blade parts at the entry and/or exit edge, the profile of which component is entirely redundant with respect to the theoretical profile conforming to the fluid technology, characterized in that the actual surface (I5) (M5) close to the junction (16) is determined by measurement technology on the suction and pressure side of the "repaired" blade (9), respectively, while the actual surface (I5) is completed at the maximum possible access to the data-stored theoretical surface (S5) by removing the respective replacement component (18) at the level of the radius of the blade (9) involved in each repair.

6. Method according to claim 1, applied in the case of the creation of a site within the repair field with a material coating at the entire blade tip, the contour of which is left with a margin with respect to the theoretical contour according to the fluid technology, characterized in that the actual surface (I6) (M6) surrounding the blade (10) is determined in a measuring technology radially inwards and close to the joining zone (17) of the blade concerned, and the surface (06) of the blade (10) is finished by removing the margin from the actual surface (I6) up to the theoretical height of the radius of the coated blade tip (13).

7. A method according to one of claims 1 to 6, characterized in that the machining-compatible removal of the component material is effected mechanically, electrically or electrochemically.

8. A method according to one of claims 1 to 6, characterized in that the surface determination of the measuring technique is effected by means of component contact.

9. A method according to one of claims 1 to 6, characterized in that the surface determination of the measuring technique is effected by means of contactless elements.

10. A method according to claim 7, characterized in that the surface determination of the measuring technique is effected by means of component contact.

11. A method according to claim 7, characterized in that the surface determination of the measuring technique is effected by means of non-contact elements.