Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
1999-11-18
2001-05-01
Freay, Charles G. (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
Reexamination Certificate
active
06223538
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a ceramic lining for thermally highly-stressed walls of combustion chambers. Such linings are used in particular as an internal wall insulation of metallic combustion chambers, for example for gas turbines.
2. Brief Description of the Related Art
Combustion chamber walls may be designed with polygonal surface elements of ceramic material or metal. The number of corners of these elements is usually 3 or 4. But hexagonal surface elements are also known. These surface elements are structured like a plate and are attached to the metallic support structure with a separate bolt.
DE 195 02 730 A1 describes, for example, a ceramic lining of a combustion chamber consisting of at least one wall plate of high-temperature-resistant structural ceramic, also called monolithic ceramic, with at least one continuous opening and one attachment element per opening. The attachment element is attached by its foot in a metallic retention device provided on a metallic support wall, whereby the head of the attachment element rests in the opening of the wall plate. The attachment element also consists of high-temperature-resistant structural ceramic and is connected spring-elastically to the retention device. An insulation layer of fiber ceramic is provided between the metal wall and the ceramic wall plate.
The advantages of this solution are that the lining can be uninstalled without destroying it and therefore can be used several times. The spring-elastic connection of the ceramic structure with the metallic retention construction furthermore makes it possible for the thermal expansions between metallic and ceramic components or deformations of the insulation layer through mechanical stresses to be absorbed.
These advantages are counteracted by the disadvantages that the attachment of the lining on the metallic support structure is relatively complex because of the separate bolt and retention device, and that the lining is complicated because it requires several layers.
Because of the plate structure, the insulation layer on the side facing away from the hot gas also must be constructed from plates in a ceramic design of the combustion chamber. The usually porous structure of the insulating material makes the insulation plates sensitive to vibrations, which may cause a breaking of the parts. It is also necessary that retainers for the insulation are provided.
In addition, the hot-gas-conducting, plate-shaped combustion chamber tiles are also very sensitive to vibrations and damage due to foreign parts, since the plates are very thin and fragile.
SUMMARY OF THE INVENTION
The invention attempts to avoid these disadvantages. It is based on the objective of developing a ceramic lining for combustion chambers that is resistant to vibrations and large temperature gradients, that is easy to manufacture, and that does not require any additional retainers for the insulation.
According to the invention, this is achieved for a ceramic lining in that the ceramic elements essentially have the shape of a straight, regular pyramid whose base has n corners and faces the combustion chamber, and into whose tip the retention bolt is integrated.
The advantages of the invention are that, as a consequence of the voluminous construction of the ceramic elements, a functionally favorable shape is achieved. Large, hot surfaces of the ceramic element continuously change into the retention bolt, so that the heat is continuously dissipated from the hot surface into the (cooled) bolt. This reduces rough changes between cross-sections that would have an unfavorable effect on the tensions in the component. The integrated retention bolt makes the ceramic elements resistant to vibrations and temperature gradients, so that they do not break. In addition, the shaped elements are easy to manufacture. Because of their shapability on all sides during the molding of the blanks, it is possible to achieve a good degree of compacting.
It is useful that the hollow spaces formed by the ceramic elements with their surfaces facing away from the combustion chamber are filled with insulation bodies that are form-fitted between the ceramic elements on the one side and the metallic support structure on the other side. This shields the metallic support structure especially well from the high temperatures of the combustion chamber. This form-fitting is also advantageous because it eliminates the need for additional retainers for the insulation bodies.
In one embodiment it is furthermore advantageous if the hollow spaces formed by the ceramic elements with their surfaces facing away from the combustion chamber, i.e., the hot gas side, are filled with air. This is a very cost-effective embodiment since cheap air functions in this case as insulation material.
It is also useful if the ceramic elements have a triangular base, preferably a tetrahedral shape. This shape is the one that can be manufactured most efficiently, and because of the stout shape of the ceramic elements a good degree of compaction is achieved.
It is finally also advantageous that the ceramic elements are pressed along with the insulation bodies using elastic elements, preferably plate springs, cylindrical pressure springs or corrugated metal sheets against the metallic support structure, or the insulation bodies are pressed by means of elastic elements against the ceramic elements. This makes additional retainers for the insulation superfluous, reduces cooling air leakage, and achieves a dampening of vibrations. The latter is also accomplished with an elastically positioned retention bolt. The spring-elastic connection of the ceramic structure or insulation material absorbs the thermal expansions between the various components and the deformations of the insulation material due to mechanical stresses.
It is furthermore possible to construct the surfaces of the ceramic elements and insulation bodies in convex or concave shape. This has the advantage that curvatures in the combustion chamber wall can be followed, permitting an optimum lining.
It is furthermore useful if the base of the ceramic elements, which forms the hot gas side, is provided with thermal insulation layers or abrasion-resistant layers. This is a good option if instead of monolithic ceramic a less resistant but cheaper base material is used for the element. This also permits a stable lining of the combustion chamber that is resistant to vibration and high temperatures.
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Benz Urs
Heger Armin
Konig Marcel
Kranzmann Axel
Pfeiffer Andreas
Asea Brown Boveri AG
Burns Doane Swecker & Mathis L.L.P.
Freay Charles G.
Torrente David J.
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