EP2730370B1 - Method to adjust a predetermined radial tip clearance of a turbomachine blade - Google Patents

Description

The present invention relates to a method for setting a predetermined radial gap of arranged in a housing of a turbomachine blades.

Blades of turbomachines, in particular turbine blades, are subject during operation to a very high material stress and a correspondingly large wear. For this reason, the blades are usually replaced by new blades during maintenance work after a predetermined period of operation. The operating time is advantageously chosen such that the exchanged blades can still be repaired.

When the vanes of a turbine are replaced, the turbine blades, the turbine vanes and the guide segments are replaced. In order to be able to ensure the maintenance of the original turbine performance in such an exchange, the original radial blade clearance must also be achieved in the new turbine blades. For this purpose, the blade tips of the new blades are machined accordingly prior to their assembly. Since the radial gap dimension depends not only on the manufacturing tolerances of the new blades but also on other influencing factors, the final radial blade gap results only after complete replacement of all blades. Factors influencing this are, for example, the contour of the new guide vanes, the contour of the new guide rings, the coating of the new vanes and guide rings, the change in the position of the new vanes relative to the position of the replaced old vanes, and the like. The finally adjusting gap dimension is correspondingly difficult in advance and can only be calculated within a fairly broad tolerance band.

The machining of the blade tips of new blades to adjust the radial gap is usually done in the context of grinding. This is always carried out away from the turbomachine, since otherwise there would be a risk that the turbomachine is affected by the resulting during processing sanding dust. Thus, for example, the blades can be machined using a conventional grinding system mounted on the original wheel disc state, including the runner must be unstacked in advance, which is associated with a lot of effort. Alternatively, instead of the original wheel disc and a so-called dummy wheel disc can be used, which eliminates the unstacking of the rotor. However, the use of such a dummy wheel disc is in turn associated with a lower machining accuracy, which can adversely affect the performance of the turbomachine. It is also possible to machine the blades without wheel disc with a so-called single blade grinding, which is associated with further losses in terms of machining accuracy.

The patent DE-19908708 describes, for example, a grinding device.

Based on this prior art, an object of the present invention to provide a method of the type mentioned and a grinding apparatus for performing the method, with which the setting of a predetermined radial gap of arranged in a housing of a turbomachine blades in the context of a grinding of the Shovel tips easy, fast and convenient with very high machining accuracy feasible without endangering the proper operation of the turbomachine.

To achieve this object, the present invention provides a method of the type mentioned, comprising the steps of: a) removing a housing part with at least partial exposure of the blades to be machined; b) placing a grinding device portion of a blade to be machined such that the tip of the blade can be processed with a grinding wheel of the grinding device; c) shielding the processing area by disposing a shielding device configured to oppose leaving of grinding dust from the shielded processing area; d) providing a suction such that it sucks sanding dust from the shielded processing area; and e) grinding the bucket tip of the bucket in situ to produce the predetermined radial gap. The inventive method is characterized in particular by the fact that the shielding of the processing area and the suction prevent fouling of the turbomachine by grinding dust, whereby machining in situ on a mounted in the intended condition blade is made possible. The processing of the blades in situ is on the one hand to the advantage that a very high, the known method superior machining accuracy is achieved, so that not only maintaining an original performance of the turbomachine but also optimize the performance by adjusting the radial gap can be done. On the other hand, a destacking of the rotor is not required for carrying out the method, whereby time and cost can be saved. The blades may be, for example, those of a compressor or a turbine.

Preferably, after completion of step e), the grinding device and a further blade are aligned with each other, whereupon again steps c) to e) are performed. In other words, several blades are processed one after the other here.

According to a variant of the method according to the invention, step e) is carried out on a blade with an already ground blade tip. The pre-grinding of the blade tip, for example, in a state in which the blade is fixed to a dummy wheel disc as described above, or using a Einzelschaufelschleifvorrichtung. The final or fine machining is then carried out in the intended mounted state of the blade using the method according to the invention, which then highest machining accuracies and a correspondingly optimal performance of the turbomachine can be achieved.

The shielding device is preferably formed by a brush arrangement provided on the grinding device and encircling the grinding wheel in an annular manner. The use of a brush arrangement as a shielding device is advantageous in that the flexible brushes are sealingly applied to the component to be processed, so that gaps are eliminated by which grinding dust can escape from the shielded processing area.

Advantageously, the dimensions of the grinding device used are matched to the distances between axially adjacent blade arrangements of the turbomachine, that the blades of all blade assemblies can be edited collision-free with the grinding wheel of the grinding device. Accordingly, for example, the blades of all stages of a turbine can be machined with a single grinder, thereby avoiding changeover times.

Preferably, cooling fluid bores provided on the rotor blade are at least partially closed before the implementation of step e). In this way it can be prevented that during the processing resulting grinding dust within the shielded processing area clogs existing cooling fluid bores. Also, clogging of the cooling fluid bores is counteracted if abrasive dust should leave the shielded processing area despite the shielding means and the suction.

The closing of cooling air holes is advantageously carried out using adhesive tape and / or wax. Tape becomes preferred at those locations that do not come into contact with the shielding device. The use of wax is particularly suitable in the area of the blade tips, since wax is normally not dissolved upon contact with the shielding device.

According to one embodiment of the method according to the invention, the grinding device is held movably on a cross slide arranged on a base plate in two mutually perpendicular directions. Accordingly, the grinding wheel can be moved appropriately for machining the blade tip.

Preferably, the base plate is attached in step b) to the housing of the turbomachine. Accordingly, unwanted relative movements between the grinding wheel and the blade to be machined can be excluded and thus a proper work result can be ensured.

To achieve the object mentioned above, the present invention further provides a grinding apparatus, in particular for carrying out the method described above, which comprises a grinding wheel, a grinding wheel enclosing shielding device, which is designed such that it shields the processing area during normal operation of the grinding device, and a suction device, which is designed such that it sucks abrasive particles from the shielded processing area during the normal operation of the grinding device.

The shielding device is provided in accordance with an embodiment of the grinding device according to the invention in the form of a grinding wheel annularly enclosing brush assembly. With such a brush arrangement very good results were achieved.

The grinding device is preferably arranged on a cross slide arranged on a base plate in two relative to one another vertical directions held movable.

On the base plate advantageously a fastening device is provided, which is designed such that the base plate is detachably fastened to a housing of a turbomachine.

• Figur 1 eine schematische Vorderansicht einer Schleifvorrichtung gemäß einer Ausführungsform der vorliegenden Erfindung;
• Figur 2 ein Ablaufdiagramm, das schematisch die Schritte eines unter Verwendung der in Figur 1 dargestellten Schleifvorrichtung durchgeführten Verfahrens gemäß einer Ausführungsform der vorliegenden Erfindung zeigt;
• Figur 3 eine schematische perspektivische Teilansicht einer Strömungsmaschine, die drei axial benachbart angeordnete Laufschaufelanordnungen bzw. Stufen bei abgehobenem oberen Gehäuseteil zeigt;
• Figur 4 eine schematische vergrößerte perspektivische Teilansicht der in Figur 3 dargestellten Strömungsmaschine, die die Bearbeitung einer Schaufelspitze einer Laufschaufel der Strömungsmaschine unter Verwendung der in Figur 1 dargestellten Schleifvorrichtung zeigt; und
• Figur 5 ein Ablaufdiagramm, das schematisch die Schritte eines unter Verwendung der in Figur 1 dargestellten Schleifvorrichtung durchgeführten Verfahrens gemäß einer weiteren Ausführungsform der vorliegenden Erfindung zeigt.

Further features and advantages of the present invention will become apparent from the following description of an embodiment with reference to the accompanying drawings. In it is:

• FIG. 1 a schematic front view of a grinding apparatus according to an embodiment of the present invention;
• FIG. 2 a flow chart schematically illustrating the steps of using the in FIG. 1 illustrated grinding apparatus according to an embodiment of the present invention;
• FIG. 3 a schematic perspective partial view of a turbomachine showing three axially adjacent blade assemblies or stages with lifted upper housing part;
• FIG. 4 a schematic enlarged partial perspective view of in FIG. 3 illustrated turbomachine, the processing of a blade tip of a blade of the turbomachine using the in FIG. 1 shown grinding device shows; and
• FIG. 5 a flow chart schematically illustrating the steps of using the in FIG. 1 illustrated grinding method according to another embodiment of the present invention.

FIG. 1 shows a grinding apparatus 1 according to an embodiment of the present invention. The grinding device 1 comprises a grinding wheel 2, which is rotationally driven by a drive 3. The grinding wheel 2 is annularly bordered by a shielding device, which in the present case is formed by a brush arrangement 4. The brush assembly 4 comprises a plurality of flexible bristles projecting outwardly over the grinding wheel 2 so as to come into contact with a workpiece to be machined during normal operation of the grinding apparatus 1. Furthermore, the grinding device 1 comprises a suction device 5 arranged underneath the grinding wheel 2, which during the normal operation of the grinding device 1 draws off abrasive particles from the shielded processing region of the grinding device 1, which is defined by the brush arrangement 4. The drive of the grinding wheel 2 and the suction 5 are coupled to one another such that the drive is switched off automatically in case of failure of the suction 5. The grinding device 1 is held movably on a cross slide 7 arranged on a base plate 6 in two mutually perpendicular directions in the plane of the base plate 6. The movement of the grinding device 1 is realized via a drive unit not shown in detail and an associated control. The dimensions and the weight of the grinding device 1 are chosen overall such that they can be easily packaged and transported to the operating location of turbomachines. Preferably, the grinding device 1 is designed to be portable.

FIG. 2 FIG. 10 is a flow chart of a method according to an embodiment of the present invention, which is performed using the methods of FIG FIG. 1 Grinder 1 shown is performed. The method is used to optimize a predetermined radial gap of arranged in a housing of a turbomachine blades and, accordingly, to optimize the performance of the turbomachine.

• In einem ersten Schritt S1 wird ein Gehäuseteil der Strömungsmaschine unter zumindest teilweiser Freilegung von zu bearbeitenden Laufschaufeln entfernt. Figur 3 zeigt beispielhaft eine Teilansicht einer Strömungsmaschine 8 nach Durchführung des Schrittes S1. Die Strömungsmaschine 8 umfasst ein zweiteiliges Gehäuse mit einer unteren Gehäuseschale 9 und einer oberen Gehäuseschale, die auf die untere Gehäuseschale 9 aufgesetzt und im bestimmungsgemäßen Zustand entlang einer Teilfuge 10 fest mit dieser verschraubt ist. In dem in Figur 3 dargestellten Zustand ist die obere Gehäuseschale abgehoben, so dass die Laufschaufeln 11 der vorliegend drei Stufen 12, 13 und 14 aufweisenden Strömungsmaschine frei zugänglich sind.
• In einem zweiten Schritt S2 werden Kühlfluidbohrungen der einzelnen Laufschaufeln 11 unter Verwendung von Klebeband 15 und/oder Wachs verschlossen, um zu verhindern, dass Schleifstaub während der Durchführung einer sich in Schritt S6 anschließenden Schleifbearbeitung die Kühlfluidbohrungen zusetzen kann. Klebeband 15 wird an denjenigen Stellen eingesetzt, die nicht mit der Bürstenanordnung 4 im Rahmen der Schleifbearbeitung in Kontakt kommen. An allen anderen Stellen, insbesondere im Bereich der Schaufelspitzen, wird hingegen Wachs eingesetzt, da sich dieses auch bei Kontakt mit der Bürstenanordnung 4 nicht ablöst.

The starting point of this process variant according to the invention is a turbomachine whose radial gap or power was already set by shortening the blades with one of the known methods described above by shortening the blades. Due to the fact that the blades are processed in the disassembled state in all of these methods, the adjustment of the radial gap and correspondingly the performance of the turbomachine can be further optimized, according to the invention, the following steps are carried out:

• In a first step S1, a housing part of the turbomachine is removed with at least partial exposure of blades to be machined. FIG. 3 shows an example of a partial view of a turbomachine 8 after performing step S1. The turbomachine 8 comprises a two-part housing with a lower housing shell 9 and an upper housing shell, which is placed on the lower housing shell 9 and screwed in the proper condition along a parting line 10 with this. In the in FIG. 3 illustrated state, the upper housing shell is lifted so that the blades 11 of the present three stages 12, 13 and 14 having turbomachine are freely accessible.
• In a second step S2, cooling fluid bores of the individual rotor blades 11 are closed using adhesive tape 15 and / or wax in order to prevent the grinding dust from clogging the cooling fluid bores during the execution of a subsequent grinding operation in step S6. Adhesive tape 15 is used at those locations that do not come into contact with the brush assembly 4 in the course of grinding. In all other places, especially in the area of the blade tips, however, wax is used, since this does not detach even when in contact with the brush assembly 4.

In step S3, the grinding device 1 is arranged in the region of a blade 11 to be machined of the step 12 such that the tip of the blade with the grinding wheel 2 of the grinding device 1 can be edited. More specifically, the base plate 6, on which the grinding device 1 is mounted, is fastened to the parting line 10 of the lower casing shell 9 of the turbomachine 8 by using screws 16, as shown in FIG FIG. 4 is shown schematically. Accordingly, the grinding wheel 2 can be moved in the direction of the arrows 17 and 18 using the cross slide 7 for machining the blade 11.

As soon as the grinding wheel 2 is brought up to the tip of a blade 11 to be machined in the direction of the arrow 18, the brushes of the brush assembly 4 come into sealing contact with the blade 11, whereby according to step S4 the working region is shielded in such a way that it leaves during grinding sanding dust from the shielded processing area is counteracted. It should be noted that in FIG. 4 the upper row of brushes of the brush assembly 4 is not shown to release the view of the grinding wheel 2.

With approach of the grinding wheel 2 to the blade 11, the suction 5 is automatically provided in accordance with step S5 such that it sucks during the grinding grinding dust from the shielded processing area.

In a further step S6, the blade tip of the blade 11 is now ground in situ to produce the predetermined optimized gap dimension. Thanks to the fact that the grinding is performed on the blade 11 in the intended mounted state, this highest machining accuracies are achieved. During processing, the grinding dust is prevented by the brush assembly 4 from leaving the shielded processing area, and removed using the suction 5 from the processing area. In this way, contamination of the turbomachine by grinding dust is effectively counteracted. If the suction 5 fails during grinding, the drive of the grinding wheel 2 is automatically switched off, since lack of suction pollution-free machining can not be guaranteed.

In a further step S7, the step 12 is rotated such that the tip of another blade 11 can be processed with the grinding wheel 2 of the grinding device 1, whereupon the steps S4 to S6 are carried out again. This process is repeated until all blades 11 of stage 12 have been optimally processed with respect to the gap dimension.

For machining a blade 11 of the adjacent step 13, the grinding wheel 2 can be moved in the direction of the arrow 17 to the step 13 as a function of the width of the base plate 6 or of the length of the cross slide 7. Alternatively, the base plate 6 can naturally also be displaced manually along the parting line 10 of the turbomachine 8.

The dimensions of the grinding device 1 are matched to the distances between the individual stages 12, 13 and 14 such that the moving blades 11 of all stages 12, 13 and 14 can be processed without collision with the grinding wheel 2 of the grinding device 1. In other words, the width of the grinding device 1 is selected such that when processing a blade 11 of the stage 12, a collision of the grinding device 1 with the radially above the blades 11 of the stage 12 projecting blades 11 of the stage 13 is not to be feared. Likewise, a machining of the blades 11 of the stage 13 is possible without the grinding device 1 colliding with the blades 11 of the stage 14.

FIG. 5 FIG. 10 is a flowchart of a method according to another embodiment of the present invention for replacing worn blades. FIG to reset the original gap with new blades. Method steps of this second variant, the method steps of referring to FIG. 2 For the sake of simplicity, identical reference symbols are provided in FIG. 5 for the sake of simplicity. A further explanation of these mutually corresponding method steps will be omitted below.

In step S1, a housing part of a turbomachine is removed with at least partial exposure of blades to be machined of the turbomachine, so that, for example, an arrangement according to FIG. 3 results.

In a subsequent step S8, blades to be replaced are removed.

In a further step S9, new blades are provided which replace the worn blades.

In step S10, the blade tips of the new blades provided in step S9 are pre-machined in an abrasive machining process. This preprocessing can be done, for example, using a dummy wheel disc or a single blade grinding device, as has already been described in connection with the methods known in the prior art.

In step S11, the pre-machined blades are installed to replace the blades removed in step S8.

This is followed by the previously described steps S2, S3, S4, S5 and S6 to shorten the pre-machined blades to restore or optimize the predetermined radial gap in the course of grinding their blade tips and bring to final dimensions.

The preprocessing of the new blades in step S10 when disassembled takes place primarily against the background that the amount of grinding dust accumulated in step S6 is to be reduced to a minimum. The less grinding dust accumulates in step S6, the lower the risk of fouling of the turbomachine during the execution of grinding. In step S6, therefore, only a fine machining is performed.

It should be noted, however, that the step S10 according to the present invention basically also omitted and the entire grinding of the blade tips can be performed in step S6.

Although the invention has been illustrated and described in detail by the embodiments, the invention is not limited by the disclosed examples, and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention as defined by the claims.

Claims (9)

1. Method for setting a predetermined radial gap width for rotor blades arranged in a housing of a turbomachine, wherein the method comprises the following steps:

   a) removing a housing part, at least partially exposing the rotor blades (11) which are to be machined;

   b) arranging a grinding device (1) in the region of a rotor blade (11) which is to be machined such that the tip of the rotor blade (11) can be machined using a grinding disk (2) of the grinding device (1);

   c) screening off the machining region by arranging a screening device which is formed so as to counter a release of grinding dust from the screened-off machining region;

   d) providing a suction extraction (5) such that it extracts grinding dust from the screened-off machining region; and

   e) grinding the tip of the rotor blade (11) in situ, producing the predetermined radial gap width.
2. Method according to Claim 1,
   wherein, upon completion of step e), the grinding device (1) and a further rotor blade (11) are oriented toward each other, whereupon steps c) to e) are repeated.
3. Method according to either of the preceding claims,
   wherein step e) is carried out on a rotor blade (11) whose tip is already pre-ground.
4. Method according to one of the preceding claims,
   wherein the screening device is formed by a brush arrangement (4) which is provided on the grinding device (1) and encloses the grinding disk (2) in annular fashion.
5. Method according to one of the preceding claims,
   wherein the dimensions of the grinding device (1) used are adapted to the separations between axially adjacent bladings (12, 13, 14) of the turbomachine, such that the rotor blades (11) of all bladings (12, 13, 14) can be machined using the grinding disk (2) of the grinding device (1) without there being any collision.
6. Method according to one of the preceding claims,
   wherein cooling fluid bores provided on the rotor blade (11) are at least partially closed off before step e) is carried out.
7. Method according to Claim 6,
   wherein cooling air bores are closed off using adhesive tape (15) and/or wax.
8. Method according to one of the preceding claims,
   wherein the grinding device (1) is held on a compound slide (7) arranged on a base plate (6) so as to be movable in two mutually perpendicular directions (17, 18).
9. Method according to Claim 8,
   wherein in step b) the base plate (6) is fastened to the housing of the turbomachine.

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