Patent Application
20110171039
The present invention relates to the field of gas turbine technology in that it refers to a blade arrangement of a gas turbine.
For the efficiency of a gas turbine, it is of great importance, especially in the turbine section in which the hot gases from the combustion chamber are expanded, to minimize as far as possible the gaps which occur in the region of the blading between the bladed, rotating rotor and the encompassing stator.
In the simplest case, as is reproduced in
In order to be able to reduce the clearance 25, blade arrangements 20 according to
The abrasive coating 19, 21 of such a blade arrangement is of a comparatively complex construction as a result of the embedded abrasive bodies and is therefore costly in production. The aim, however, would have to be to create a comparable cutting-in behavior without a special abrasive coating having to be provided on the blade tip.
The present disclosure is directed to a blade arrangement of a thermal turbomachine with at least one blade, which projects in the radial direction into a passage which is arranged concentrically to an axis and is exposed to throughflow by hot gas. The at least one blade terminates in a blade tip which with a clearance lies opposite a heat shield which delimits the passage. The blade and the heat shield are movable in relation to each other in a circumferential direction, and the blade tip and the heat shield are covered with coatings which enable a directed cutting of the blade tip into the heat shield, the heat shield has a porous thermal barrier coating as an outer, abradable coating, and the blade tip is provided with a homogenous, metallic cover coating.
The invention shall subsequently be explained in more detail based on exemplary embodiments in conjunction with the drawings. In the drawings
The invention should provide a remedy in this case. It is therefore the object of the invention to disclose a blade arrangement which avoids the disadvantages of known blade arrangements and with a simultaneously simple construction enables a significant reduction of the clearance between the blade tips and the oppositely disposed stator-side elements.
It is preferable for the heat shield to have a porous thermal barrier coating as an outer, abradable coating and for the blade tip to be provided simply with a homogenous metallic cover coating. The porous thermal barrier coating enables the blade tip, which is covered by the cover coating, to cut into the heat shield even without special abrasive bodies or abrasive coating and so to optimally minimize the clearance between blade tip and oppositely disposed heat shield.
The blade is essentially a rotor blade or a stator blade of a thermal turbomachine, in particular a gas turbine, wherein in the case of a stator blade a heat shield, which is fastened on the rotor, lies opposite the blade tip. According to a preferred embodiment, the blade is a rotor blade which rotates around the axis, whereas the heat shield is installed on the stator of the gas turbine in a fixed manner.
In another embodiment of the invention, the thermal barrier coating is a porous ceramic coating, in particular comprising YSZ. In this case, the porosity of the thermal barrier coating is preferably more than 20%.
An adhesion coating, particularly comprises MCrAlY, is advantageously arranged between the heat shield and the thermal barrier coating.
The metallic cover coating preferably comprises MCrAlY.
In a further embodiment, the rotor blade is part of the first rotor-blade row in the turbine section of the gas turbine.
In
As a coating which is to be abraded during the cutting in, provision is made on the heat shield 12 for a thermal barrier coating 23 which is connected to the substrate of the heat shield 12 via an adhesion coating 22 which lies in between. As an adhesion coating 22, provision may customarily be made for a metallic, anti-oxidation coating comprising MCrAlY.
In trials, it has now been proved that cutting of the blade tip into the thermal barrier coating 23 is possible even without a special abrasive coating on the blade tip 27 and leads to good results if the thermal barrier coating 23—without losing its thermal properties—is to be slightly abraded to an adequate degree. This can be achieved by a porous thermal barrier coating 23 being used.
In this case, a porous ceramic coating, which in particular may comprise YSZ (yttrium oxide stabilized zirconium), is especially suitable as a thermal barrier coating 23, wherein the porosity is created for example by means of embedded polymers which are subsequently heated. It has been proved to be advantageous in this case if the porosity of the thermal barrier coating is more than 20%, that is to say lies within the range of 22-24%, for example.
In the case of such a porous thermal barrier coating 23, the abrasion on the blade tip 27 during cutting in, in relation to the depth of the cutting-in region 28, is comparatively small so that a special abrasive coating on the blade tip 27 can be dispensed with. It suffices, therefore, if the blade tip 27 is covered with a homogenous cover coating 24 (without abrasive bodies) comprising MCrAlY, which is provided anyway as a protective coating against oxidation of the blade material.
In this way, special provisions do not need to be made on the blade 11 for cutting in, as a result of which, production of the blade 11 is substantially simplified.
| Number | Date | Country | Kind |
|---|---|---|---|
| 01285/08 | Aug 2008 | CH | national |
This application is a continuation of International Application No. PCT/EP2009/060387 filed Aug. 11, 2009, which claims priority to Swiss Patent Application No. 01285/08, filed Aug. 15, 2008, the entire contents of all of which are incorporated by reference as if fully set forth.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2009/060387 | Aug 2009 | US |
| Child | 13024545 | US |
