Furnaces – Wall structure
Reexamination Certificate
2000-09-19
2002-06-04
Lazarus, Ira S. (Department: 3749)
Furnaces
Wall structure
C110S338000, C432S252000, C432S254100, C060S752000
Reexamination Certificate
active
06397765
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a wall segment for a combustion area to which a hot fluid can be applied, in particular for a combustion chamber in a gas turbine. The invention also relates to a combustion area.
A thermally highly stressed combustion area, such as a furnace, a hot-gas channel or a combustion chamber in a gas turbine, in which a hot fluid is produced and/or carried, is provided with a lining for protection against excessive thermal stress. The lining is composed of heat-resistant material and protects a wall of the combustion area against direct contact with the hot fluid, and the severe thermal stress associated with this.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,840,131 relates to improved attachment of ceramic lining elements to a wall of a furnace. A rail system, which is attached to the wall and has a number of ceramic rail elements by means of which the lining elements are held is provided in this document. Further ceramic layers may be provided between a lining element and the wall of the furnace, including a layer composed of loose, partially compressed ceramic fibers, which layer has at least 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 composed of a heat-insulating, fire-resistant ceramic fiber material.
U.S. Pat. No. 4,835,831 likewise relates to the fitting of a fire-resistant lining on a wall of a furnace, in particular a vertical wall. A layer composed of glass, ceramic or mineral fibers is fitted to the metallic wall of the furnace. This layer is attached to the wall by metallic brackets or by adhesive. A wire mesh network with honeycomb meshes is fitted to this layer. The mesh network is likewise used to protect the layer composed of ceramic fibers from falling off. A continuous, closed surface composed of fire-resistant material is applied to the layer secured in this way, by means of a suitable spraying method. The described method largely avoids fire-resistant particles produced during the spraying process from being thrown back, as would be the case if the fire-resistant particles were sprayed directly onto the metallic wall.
A lining for walls of highly stressed combustion areas is described in EP 0 724 116 A2. The lining comprises wall elements composed of high-temperature-resistant structural ceramic, such as silicon carbide (SiC) or silicon nitride (Si
3
N
4
), which are mechanically attached by means of a fastening bolt to a metallic supporting structure (wall) of the combustion chamber. A thick insulation layer is provided between the wall element and the wall of the combustion area, so that the wall element is at a distance from the wall of the combustion chamber. The insulation layer, which is three times as thick as the wall element, is composed of ceramic fiber material, which is prefabricated in blocks. The dimensions and the external shape of the heat protection segments can be matched to the geometry of the area to be lined.
Another type of lining for a thermally highly stressed combustion area is specified in EP 0 419 487 B1. The lining is composed of heat protection segments, which are held mechanically on a metallic wall of the combustion area. The heat protection segments touch the metallic wall directly. In order to avoid excessive heating of the wall, for example by direct heat transfer from the heat protection segment or by the ingress of hot active fluid into the gaps formed by mutually adjacent heat protection segments, the area formed by the wall of the combustion area and the heat protection segment has cooling air, so-called sealing air, applied to it. The sealing air prevents the hot active fluid from penetrating as far as the wall, and at the same time cools the wall and the heat protection segment.
SUMMARY OF THE INVENTION
The object of the invention is to specify a wall segment for a combustion area, in particular a combustion chamber in a gas turbine, to which a hot fluid can be applied. A further object is to specify a heat-resistant combustion area.
The object relating to a wall segment is achieved according to the invention by a wall segment for a combustion area, to which a hot fluid can be applied, having a metallic supporting structure and having a heat protection element which is mounted on the metallic supporting structure. The metalllic supporting structure is provided at least in places with a thin, heat-resistant separating layer, with the separating layer being fitted between the metallic supporting structure and the heat protection element. Alternatively or additionally, the object is achieved by a wall segment in which, according to the invention, a metallic, heat-resistant separating layer is fitted at least in places between the supporting structure and the heat protection element. The metallic separating layer may be thin.
The invention is based on the knowledge that the heat protection segment and the wall of a combustion area are composed predominantly of relatively inelastic materials such as structural ceramic and metal. A disadvantage of a lining designed in such a way for a combustion area is that the heat protection elements directly touch the wall of the combustion area. For production reasons and owing to the different thermal expansion of the wall and the heat protection element, the heat protection element may not always be able to lie flat on the wall. In consequence, high forces may be produced locally at the contact points. If the heat protection element and the wall have different thermal expansion characteristics, it is possible in unfavorable conditions for the heat protection segments and/or the wall to be damaged due to the introduction of high forces at the contact points when the operating state of the combustion area changes, for example in the event of a load change in a gas-turbine system. In consequence, gaps between the heat protection element and the wall may be formed between the contact points of the heat protection element and the wall, where there is no contact. These gaps form access channels for hot fluid. In order to prevent the ingress of hot fluid, an increased amount of sealing air would be required in this situation between the wall and the heat protection element.
The refinement of a wall segment according to the invention has the advantage that a deformable separating layer inserted between the metallic supporting structure and the heat protection element can absorb and compensate for possible relative movements of the heat protection element and of the supporting structure. Such relative movements can be caused, for example, in the combustion chamber of a gas turbine, in particular an annular combustion chamber, by the materials used having different thermal expansion characteristics or by pulsations in the combustion area. This can occur in the event of irregular combustion to produce the hot active fluid or as a result of resonance effects, for example. At the same time, the separating layer results in the relatively inelastic heat protection element lying flatter on the separating layer and on the metallic supporting structure overall, since the heat protection element penetrates into the separating layer in places. The separating layer can thus also compensate for irregularities, due to production effects, on the supporting structure and/or on the heat protection element, which can lead to disadvantageous introduction of forces at specific points, locally.
The heat-resistant separating layer inserted between the heat protection element and the metallic supporting structure can advantageously be deformed elastically and/or plastically by the heat protection element. The heat protection element can thus penetrate into the heat-resistant separating layer in places, and deform it, and compensate for irregularities in the contact surface of the heat protection element and/or of the supporting structure due to production effects and/or occurring as a result of operation of the system. Forces can thus be introduced over a
Harness & Dickey & Pierce P.L.C.
Lazarus Ira S.
Rinehart K. B.
Siemens Aktiengesellschaft
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