Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
2002-08-27
2004-03-30
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S753000, C110S336000, C110S338000
Reexamination Certificate
active
06711899
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority to EP/01120506.9 filed Aug. 28th, 2001 under the European Patent Convention and which is incorporated by reference herein in its entirety.
FIELD OF THE INVENTION
The invention relates to a heat shield block, in particular for lining a combustion chamber wall, having a hot side which can be subjected to a hot medium, a wall side opposite the hot side, and a peripheral side adjoining the hot side and the wall side. The invention also relates to the use of a heat shield block, in particular for lining a combustion chamber wall.
BACKGROUND OF THE INVENTION
A thermally and/or thermomechanically highly loaded combustion space, such as, for example, a furnace, a hot gas duct, or a combustion chamber of a gas turbine, in which a hot medium is produced and/or directed is provided with an appropriate lining for protection from excessive thermal stressing. The lining normally consists of heat-resistant material and protects a wall of the combustion space from direct contact with the hot medium and the associated high thermal loading.
U.S. Pat. No. 4,840,131 relates to a fastening of ceramic lining elements on a wall of a furnace. In this case, a rail system which is fastened to the wall and has a plurality of ceramic rail elements is provided. The lining elements can be mounted on the wall by the rail system. Further ceramic layers may be provided between a lining element and the wall of the furnace, inter alia a layer of loose, partly compressed ceramic fibers, this layer having at least approximately the same thickness as the ceramic lining elements or a greater thickness. The lining elements in this case have a rectangular shape with a planar surface and are made of a heat-insulating, refractory ceramic fiber material.
U.S. Pat. No. 4,835,831 likewise deals with the application of a refractory lining to a wall of a furnace, in particular to a vertically arranged wall. A layer consisting of glass fibers, ceramic fibers or mineral fibers is applied to the metallic wall of the furnace. This layer is fastened to the wall by means of metallic clips or by adhesive. A wire mesh net with honeycomb meshes is applied to this layer. The mesh net likewise serves to prevent the layer of ceramic fibers from falling down. By means of a suitable spray process, a uniform closed surface of refractory material is applied to the layer thus fastened. The method described largely prevents a situation in which refractory particles striking during the spraying are thrown back, as would be the case with direct spraying of the refractory particles onto the metallic wall.
A ceramic lining of the walls of thermally highly stressed combustion spaces, for example of gas-turbine combustion chambers, is described in EP 0 724 116 A2. The lining consists of wall elements of high-temperature-resistant structural ceramic, such as, for example, silicon carbide (SiC) or silicon nitride (Si
3
N
4
). The wall elements are elastically fastened to a metallic supporting structure (wall) of the combustion chamber in a mechanical manner by means of a central fastening bolt. A thick thermal insulating layer is provided between the wall element and the wall of the combustion space, so that the wall element is at a corresponding distance from the wall of the combustion chamber. The insulating layer, which is about three times as thick in relation to the wall element, is made of a ceramic fiber material which is prefabricated in blocks. The dimensions and the external shape of the wall elements can be adapted to the geometry of the space to be lined.
Another type of lining of a thermally highly loaded combustion space is specified in EP 0 419 487 B1. The lining consists of heat shield elements which are mechanically mounted on a metallic wall of the combustion space. The heat shield elements touch the metallic wall directly. In order to avoid excessive heating of the wall, e.g. as a result of direct heat transfer from the heat shield element or by introducing hot medium into the gaps formed by the heat shield elements adjoining one another, cooling air, the “sealing air”, is admitted to the space formed by the wall of the combustion space and the heat shield element. The sealing air prevents the penetration of hot medium up to the wall and at the same time cools the wall and the heat shield element.
WO 99/47874 relates to a wall segment for a combustion space and to a combustion space of a gas turbine. Specified in this case is a wall segment for a combustion space which can be acted upon by a hot fluid, e.g. a hot gas, having a metallic supporting structure and a heat protection element fastened to the metallic supporting structure. Inserted between the metallic supporting structure and the heat protection element is a deformable separating layer which is intended to absorb and largely compensate for possible relative movements of the heat protection element and the supporting structure. Such relative movements may be caused, for example, in the combustion chamber of a gas turbine, in particular in an annular combustion chamber, by different thermal expansion behavior of the materials used or by pulsations in the combustion space, as may arise during irregular combustion for producing the hot working medium or by resonance effects. At the same time, the separating layer causes the relatively inelastic heat protection element to rest in a more planar manner overall on the separating layer and the metallic supporting structure, since the heat protection element partly penetrates into the separating layer. The separating layer, for production reasons, can thus compensate for unevenness at the supporting structure and/or the heat protection element, which unevenness may lead locally to an unfavorable force input.
SUMMARY OF THE INVENTION
The invention is based on the observation that, in particular ceramic, heat shield blocks, on account of their requisite flexibility with regard to thermal expansions, are often only inadequately protected against mechanical loads, such as shocks or vibrations for example.
The object of the invention is accordingly to specify a heat shield block which ensures high operating reliability with regard to both unrestricted thermal expansion and stability relative to mechanical, in particular shock-like, loads. A further object of the invention consists in specifying the use of the heat shield block, in particular for lining a combustion chamber wall.
The object which relates to a heat shield block is achieved according to the invention by a heat shield block, in particular for lining a combustion chamber wall, having a hot side which can be subjected to a hot medium, a wall side opposite the hot side, and a peripheral side adjoining the hot side and the wall side, a tension element which can be prestressed to a prestress being attached to the peripheral side, release of a fragment formed during a fracture being prevented by the prestress of the tension element.
The invention shows a completely new way of providing lasting protection for heat shield blocks against high accelerations as a result of shocks or vibrations. In this case, the invention is already based on the knowledge that steady and/or transient vibrations in a combustion chamber wall induce corresponding vibrations in heat shield blocks as normally used for lining said combustion chamber wall. In this case, considerable accelerations above a limit acceleration may occur, in particular in a resonance case, in the course of which the heat shield blocks lift from the combustion chamber wall and consequently strike again. Such striking on the solid or also partly damped combustion chamber wall leads to very high forces on the heat shield blocks and may cause considerable damage, e.g. fracture of the latter. There is also the exceptionally high thermal loading of the heat shield block on account of the admission of a hot medium to the heat shield block during operation. Incipient cracks may therefore occur on both the wall side and the hot side of the heat shield block, there
Bast Ulrich
Rettig Uwe
Taut Christine
Kim Ted
Siemens Aktiengesellschaft
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