EP1660833A2

EP1660833A2 - Thermal shielding brick for lining a combustion chamber wall, combustion chamber and a gas turbine

Info

Publication number: EP1660833A2
Application number: EP04763502A
Authority: EP
Inventors: Holger Grote; Andreas Heilos; Marc Tertilt
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2003-08-22
Filing date: 2004-07-26
Publication date: 2006-05-31
Also published as: EP1508761A1; US20070000252A1; WO2005022061A3; WO2005022061A2; US7793503B2

Abstract

The invention relates to a heat shield block (26), particularly for lining a combustion chamber wall (24), with a hot side (35) that can be subjected to the action of hot medium (M) and with a wall side (33) situated opposite the hot side (35). A core area (31), which has a core material (39), extends inside the heat shield block (26) from the hot side (35) to the wall side (33). The core area (31) is surrounded by an edge area (37) with an edge material (41) whose heat conductivity is lower than that of the core material (39). This targeted thermal insulation in the edge area (37) provided in the form of a material bond between the core material (39) and the edge material (41) renders the heat shield block (26) particularly unsusceptible to the formation and growth of cracks in the core area (31) on the hot side (35). The invention also relates to a combustion chamber (4) provided with heat shield blocks (26) of the aforementioned type, and to a gas turbine (1) provided with a combustion chamber (4) comprising such a heat shield block (26).

Description

description

Heat shield brick for lining a combustion chamber wall, combustion chamber and gas turbine

The invention relates to a heat shield brick, in particular for lining a combustion chamber wall, with a hot side that can be acted upon by a hot medium and a wall side opposite the hot side and with a core area that extends from the hot side to the wall side

Core material. The invention further relates to a combustion chamber with an inner combustion chamber lining and a gas turbine.

A thermally and / or thermomechanically highly loaded combustion chamber, such as a furnace, a hot gas duct or a combustion chamber in a gas turbine, in which a hot medium is generated and / or guided, is provided with an appropriate lining to protect it from excessive thermal stress , The lining usually consists of heat-resistant material and protects a wall of the combustion chamber from direct contact with the hot medium and the associated strong thermal stress.

US Pat. No. 4,840,131 relates to an attachment of ceramic lining elements to a wall of an oven. Here is a rail system that is attached to the wall. The lining elements have a rectangular shape with a planar surface and consist of a heat-insulating, fire-resistant, ceramic fiber material.

U.S. Patent 4,835,831 also deals with the application of a refractory lining from a wall of an oven, particularly a vertically arranged wall. A layer consisting of glass, ceramic or mineral fibers is applied to the metallic wall of the furnace. This layer is attached by metallic clips or by glue attached to the wall. A wire mesh with ... shaped meshes is applied to this layer. The mesh network also serves to secure the layer of ceramic fibers against falling. In addition, a uniform, closed surface made of refractory material is attached using a bolt. The described method largely avoids that refractory particles striking during spraying are thrown back, as would be the case if the refractory particles were sprayed directly onto the metallic wall.

A ceramic lining of the walls of thermally highly stressed combustion chambers, for example gas turbine combustion chambers, is described in EP 0 724 116 A2. The lining consists of wall elements made of high-temperature-resistant structural ceramics, such as. B. silicon carbide (SeC) or silicon nitride (Si ₃ N ₄ ). The wall elements are mechanically and elastically fastened to a metal support structure (wall) of the combustion chamber by means of a central fastening bolt. A thick thermal insulation layer is provided between the wall element and the wall of the combustion chamber, so that the wall element is appropriately spaced from the wall of the combustion chamber. The insulation layer, which is about three times as thick as the wall element, consists of ceramic fiber material that is prefabricated in blocks. The dimensions and the external shape of the wall elements can be adapted to the geometry of the room to be lined. Another type of lining of a thermally highly loaded combustion chamber is specified in EP 0 419 787 B1. The lining consists of heat shield elements, which are mechanically held on a metallic wall of the combustion chamber. The heat shield elements directly touch the metallic wall. To avoid overheating the wall, e.g. B. as a result of direct heat transfer from the heat shield element or by penetration of hot medium into the gap formed by the adjacent heat shield elements, the wall of the combustion chamber and the heat shield element-formed room with cooling air, which applies so-called sealing air. The sealing air prevents the penetration of hot medium 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 chamber and a combustion chamber of a gas turbine. Here, a wall segment for a combustion chamber, which with a hot fluid, for. B. a hot gas, can be acted upon, with a metallic support structure and a heat shield element fastened to the metallic support structure. A deformable separating layer is inserted between the metallic support structure and the heat shield element, which is to absorb and compensate for possible relative movements of the heat shield element and the support structure. Such relative movements can be caused, for example, in the combustion chamber of a gas turbine, in particular an annular combustion chamber, by different thermal expansion behavior of the materials used and by pulsations in the combustion chamber, which can occur in the event of irregular combustion to generate the hot working medium under the resonance effects. At the same time, the separating layer causes the relatively inelastic heat shield element to lie flat on the separating layer and the metallic support structure, since the heat shield element partially penetrates into the separating layer. In this way, the separating layer can compensate for unevenness in the support structure and / or the heat shield element, which can lead to an unfavorable selective force input locally.

Especially on walls of high-temperature gas reactors, such as. B. of gas turbine combustors operated under pressure, their supporting structures must be protected against a hot gas attack with suitable combustion chamber linings. Ceramic materials are suitable for this in comparison to metallic materials due to their high temperature resistance, corrosion resistance and low thermal conductivity ideally. Because of the thermal expansion properties typical of the material and the temperature differences that typically occur during operation (ambient temperature at standstill, maximum temperature at full load), the thermal mobility of ceramic heat shields must be guaranteed as a result of temperature-dependent expansion, so that thermal stresses due to expansion which do not damage the component occur. This can be achieved by the wall to be protected against hot gas attack by a large number of individual ceramic heat shields limited in size, eg. B. heat shield stones from a refractory ceramic is lined. As already discussed above in connection with EP 0 419 487 B1, corresponding expansion gaps must be provided between the individual ceramic heat shield elements which, for safety reasons, must never be completely closed, even when hot, by design. It must be ensured that the hot gas does not excessively heat the load-bearing wall structure via the expansion gaps. The simplest and safest way to avoid this in a gas turbine combustion chamber is to flush the expansion gaps with air, so-called sealing air cooling. For this purpose, the air can be used, which is required anyway for cooling mounting elements for the ceramic heat shields.

WO 02/25173 AI discloses a heat shield brick, in particular for lining a combustion chamber wall, with a hot side which can be exposed to a hot medium, a wall side opposite the hot side and a peripheral side which adjoins the hot side and the wall side and which has a peripheral side surface. A tension element provided in the circumferential direction is provided on the circumferential side, a compressive stress being generated normal to the circumferential side surface. This provides an extremely efficient and long-term stable fuse for a heat shield brick. The tension element is prestressed in the circumferential direction, a certain compressive stress being generated normal to the circumferential side surface. By this normal force, which is towards the inside of the hit zeschildstein in the center, the heat shield stone is secured even with very low normal forces. This effectively counteracts a material crack, for example as a result of a shock load. Existing material cracks cannot develop or expand, or can only do so to a limited extent, if the tension element is arranged and configured accordingly. The traction element holds the heat shield brick together, so to speak, and secures it against material cracks on the one hand and, above all, against a complete material tear through. In addition, the risk of loosening or falling out of smaller or larger fragments is effectively counteracted in the event of a possible material breakdown.

The object of the invention is to provide a heat shield brick which ensures high operational reliability and a long service life both in terms of unlimited thermal expansion and in terms of its resistance to hot gas attack. Another object of the invention is to specify a combustion chamber with an internal combustion chamber lining and to specify a gas turbine with a combustion chamber.

The object directed at a heat shield brick is achieved according to the invention by a heat shield brick, in particular for lining a combustion chamber wall, with a hot side that can be acted upon by a hot medium and a wall side opposite the hot side, and with a core region that extends from the hot side to the wall side with a Core material, the core area being surrounded by an edge area with an edge material whose thermal conductivity is lower than that of the core material.

In this case, the invention is based on the knowledge that, in the case of use, as a result of the air flowing through the gaps cooling the edges of the heat shield stone, the gap between the heat shield stones and the heat input onto the hot side of the β

Heat shield stone due to the exposure to hot gas, a three-dimensional temperature distribution within the heat shield stone. This is characterized by a drop in temperature from the hot side to the wall side and, as a result of the sealing air cooling of the edges ("edge cooling") from central points in the ceramic heat shield brick to the cooled edges. In the case of heat shield stones which are typically parallel to the hot side or to the wall side, the temperature gradient perpendicular to the wall side surface leads to comparatively only low thermal stresses, as long as there is no impediment to the thermally induced bulging for the heat shield stone in the installed state. On the other hand, a temperature gradient parallel to the wall - starting from an edge ^• to an inner area of the heat shield brick - leads particularly easily to increased thermal stresses due to the mechanical rigidity of plate-like geometries with regard to deformations parallel to their size projection surfaces. As a result of their comparatively low thermal expansion, hot edges are subjected to hot central areas that are subject to greater thermal expansion, and if the material strength is exceeded, cracks can form, starting from the edges of the heat shield brick.

With the invention, a completely new concept is now shown, in particular to avoid failure of the heat shield brick as a result of the crack formation problem, starting from the edges of the heat shield brick. The invention makes use of the knowledge that thermally induced tensile stresses generally only occur where there are temperature gradients. If it is now prevented that temperature gradients emanating from the edges of the heat shield brick penetrate deep into the interior of the heat shield brick, cracks caused thereby can penetrate only to a limited extent or do not form at all. Short cracks emanating from the edges and penetrating only slightly towards the inside of the heat shield brick can be tolerated, since these do not affect the functionality of the heat shield brick theoretically or in practical experience.

With the invention, a heat shield brick is provided, the thermal conductivity of which is set locally in order to avoid crack formation and crack growth. For this purpose, the core area is surrounded by an edge area with an edge material whose thermal conductivity is lower than that of the core material. A two-component heat shield brick is therefore specified with thermal insulation in the edge area, due to the targeted choice of material for the edge material, with a reduced thermal conductivity compared to the core material. The core area and the edge area are integral components of the heat shield brick, so that a heat shield brick is provided with a thermal conductivity that is variable over its volume. The greater thermal conductivity in the core area ensures that an approximately balanced temperature profile is established in the core area parallel to the hot side. The core area thus remains largely free of thermal stress. Temperature gradients and associated thermal stresses only occur in the edge area.

The edge region advantageously also includes the outer edges of the heat shield brick, so that, due to the lower thermal conductivity compared to the core region, they act as thermal insulation or as an insulation region. It is particularly advantageous here that the length of cracks caused by thermal stress is shortened because they are limited to the edge region, as a result of which the heat shield brick is stabilized with respect to crack formation.

In a preferred embodiment of the heat shield brick, the thermal conductivity of the edge material is less than 60%, in particular less than 50%, of the thermal conductivity of the core material. The heat shield brick is therefore designed so that there is a significant reduction in the thermal conductivity at the transition from the core area to the edge area. The edge area acts as thermal insulation that surrounds the core area. Advantageously, the edge area directly surrounds the core area, a cohesive composite of the core material and the edge material being realized.

The edge material is preferably porous, the porosity of the edge material being set in such a way that the thermal conductivity of the edge material is thereby reduced compared to the thermal conductivity of the core material. Via • the density distribution and size distribution of the pore structure of the edge material, the thermal conductivity in the edge area can be set in a targeted manner depending on the requirements in the event of a load. If necessary, a variation of the local thermal conductivity can also be achieved within the edge region by a corresponding variation of the pore size and pore diameter distribution.

In a particularly preferred embodiment, the core material and the edge material are formed from the same ceramic base material, in particular a refractory ceramic. This material identity of the base material makes it possible to achieve a particularly good material bond between the core material and the edge material. In order to achieve the desired porous structure within the edge region, it is possible, for example, to incorporate so-called pore formers into the base material during the manufacture of the heat shield brick. The pore former is advantageously pressed or cast in the area near the edge, that is to say in the edge area of the drone. During the Sinther process, the pore former evaporates and leaves the pores, which reduce the effective thermal conductivity of the base material accordingly. This pore former is preferably not used in the core area, so that the desired lowering of the thermal conductivity results in the transition from the core area to the edge area. In an advantageous embodiment, the axial extent of the edge region along the hot side of the heat shield brick is less than 20%, in particular between about 5 and 10%, of the total axial extent of the heat shield brick. In particular, the heat shield brick is provided on all edges encompassed by the edge region with a lower thermal conductivity deviating from the core material at a distance of approximately less than 10% of the respective total extent (bearing length) with a reduction in the thermal conductivity compared to the thermal conductivity of the core area to less than 50% of the core material ,

The edge region preferably extends from the hot side to the wall side. In this embodiment, the core area is completely enclosed on the circumference by the edge area, so that a full-scale thermal insulation of the core area is achieved with a material bond between the core material and the edge material.

The heat shield brick preferably has a peripheral side adjacent to the hot side and the wall side with a peripheral side surface which is at least partially formed by the edge material. In the case of an arrangement of a plurality of heat shield stones required for evaluating a combustion chamber wall, the gaps between the heat shield stones are at least partially delimited by the edge material on the peripheral side surface. The circumferential side surface is advantageously formed entirely by the core material, so that the core material is thermally insulated as well as possible.

The heat shield brick preferably consists of a ceramic base material, in particular of a refractory ceramic. By choosing a ceramic as the base material for the heat shield brick, the use of the heat shield brick is guaranteed up to very high temperatures, while at the same time oxidative and / or corrosive attacks, such as those when the hot side of the heat shield brick is exposed to a hot medium, z. B. occur a hot gas, are largely harmless to the heat shield brick. This is a particularly great advantage when using the heat shield brick in a combustion chamber, because even after the material in the edge region has been torn, the heat shield function of the heat shield brick is still guaranteed, in particular failure of the heat shield brick, for example a complete breakage, is reliably avoided, so that none Fragments can get into the combustion chamber.

Economically, this results on the one hand in the advantage that in normal operation no extraordinary maintenance and / or revision of a combustion chamber having the heat shield brick is required. On the other hand, in the event of special occurrences, the heat shield stone has emergency running properties, so that consequential damage for a turbine, for example for blading, can be avoided, since crack propagation is largely avoided by the targeted setting of the thermal conductivity in different areas of the heat shield stone.

The combustion chamber can be operated at least with the usual maintenance cycles, but it is also possible to extend the service life due to the lower tendency to crack propagation.

The object directed to a combustion chamber is achieved according to the invention by a combustion chamber with an internal combustion chamber lining which has heat shield bricks according to the above statements.

The object directed to a gas turbine is achieved according to the invention by a gas turbine with such a combustion chamber. The advantages of such a combustion chamber or of such a gas turbine result from the explanations given for the heat shield brick.

The invention is explained in more detail by way of example with reference to the drawings. They show schematically and partially simplified:

FIG. 1 shows a half section through a gas turbine,

FIG. 2 shows a perspective view of a heat shield brick,

Figure 3 is a sectional view of the heat shield brick shown in Figure 2 along the section line III-III.

Figures 4 to

FIG. 7 different configurations of a heat shield stone with a core area and with an edge area.

Identical parts are provided with the same reference symbols in all figures.

The gas turbine 1 according to FIG. 1 has a compressor 2 for combustion air, a combustion chamber 4 and a turbine 6 for driving the compressor 2 and a generator (not shown) or a work machine. For this purpose, the turbine 6 and the compressor 2 are arranged on a common turbine shaft 8, also referred to as a turbine rotor, to which the generator or the working machine is also connected, and which is rotatably mounted about its central axis 9. The combustion chamber 4, which is designed as an annular combustion chamber, is equipped with a number of burners 10 for the combustion of a liquid or gaseous fuel. The turbine 6 has a number of rotatable rotor blades 12 connected to the turbine shaft 8. The blades 12 are arranged in a ring shape on the turbine shaft 8 and thus form a number of rows of blades. Furthermore, the turbine 6 comprises a number of stationary guide vanes 14, which are also attached to an inner casing 16 of the turbine 6 in a ring shape, with the formation of rows of guide vanes. The blades 12 are used to drive the turbine shaft 8 by transmitting momentum from the hot medium flowing through the turbine 6, the working medium M. The guide blades 14, on the other hand, serve to guide the flow of the working medium M between two successive rows of moving blades or rotating blade rings seen in the flow direction of the working medium M. A successive pair of a ring of guide blades 14 or a row of guide blades and a ring of rotor blades 12 or a row of rotor blades is also referred to as a turbine stage.

Each guide vane 14 has a platform 18, also referred to as a blade root, which is arranged as a wall element for fixing the respective guide vane 14 to the inner housing 16 of the turbine 6. The platform 18 is a thermally comparatively heavily loaded component that forms the outer boundary of a hot gas channel for the working medium M flowing through the turbine 6. Each rotor blade 12 is fastened in an analogous manner to the turbine shaft 8 via a platform 20, which is also referred to as a blade root.

A guide ring 21 is arranged in each case between the platforms 18 of the guide vanes 14 of two adjacent rows of guide vanes which are arranged at a distance from one another. The outer surface of each guide ring 21 is also exposed to the hot working medium M flowing through the turbine 6 and is spaced in the radial direction from the outer end 22 of the rotor blade 12 opposite it by a gap. The between the adjacent rows of vanes Ordered guide rings 21 serve in particular as cover elements which protect the inner wall 16 or other housing built-in components against thermal overloading by the hot working medium M flowing through the turbine 6. The combustion chamber 4 is delimited by a combustion chamber housing 29, a combustion chamber wall 24 being formed on the combustion chamber side. In the exemplary embodiment, the combustion chamber 4 is configured as a so-called annular combustion chamber, in which a plurality of burners arranged in the circumferential direction around the turbine shaft 8 open into a common combustion chamber space. For this purpose, the combustion chamber 4 is configured in its entirety as an annular structure which is positioned around the turbine shaft 8.

In order to achieve a comparatively high efficiency, the combustion chamber 4 is designed for a comparatively high temperature of the working medium M of approximately 1200 ° C. to 1500 ° C. In order to achieve a comparatively long operating time even with these operating parameters, which are unfavorable for the materials, the combustion chamber wall 24 is provided on its side facing the working medium M with a combustion chamber lining formed from heat shield stones 26. For a hot gas-resistant construction of the combustion chamber 4 designed as an annular combustion chamber, the combustion chamber lining is provided with a large number of high-temperature-resistant heat shield bricks 26, so that in this way a complete, largely leak-free combustion chamber lining is formed in the annular space.

FIG. 2 shows a perspective view of a heat shield brick 26 as it is designed in particular for lining a combustion chamber wall 24 according to the invention. The combustion chamber brick 26 has a cuboid or cuboid-like geometry and extends along a longitudinal axis 43 and a transverse axis 45 which is essentially perpendicular to the longitudinal axis 43. The heat shield brick 26 has a hot side 35 which can be acted upon by the hot medium M and one which is opposite the hot side 35 Wall side 33 on. Of the A hot zone 35 to the wall side 33 extends through the interior of the heat shield brick 26, a core area 31 with a core material 39. The core area 31 is surrounded by an edge area 37 with an edge material 41, the thermal conductivity of the edge material 41 being lower than the thermal conductivity of the Core material 39. The edge region 37 completely surrounds the core region 31 along the edges of the cuboid or cuboid-like heat shield element 26. The material transition from the core material 39 in the core region 31 to the edge material 41 in the edge region 37 takes place by means of a material bond. The thermal conductivity of the edge material 41 is less than 50% of the thermal conductivity of the core material 39. This ensures that when the heat shield brick 26 is used in the combustion chamber 4 of a gas turbine 1 (see FIG. 1), an approximately balanced temperature profile parallel to the hot side 35 is found in the core area established. The core region 31 remains largely free of thermal stress due to the thermal insulation effect of the edge region 37 with the reduced thermal conductivity. Temperature gradients and associated thermal stresses therefore occur only or almost exclusively in the edge region 37, that is to say near the edges of the heat shield brick 26. The length of cracks caused by thermal stress is thus shortened, limited to the edge region 31, and the heat shield brick 26 as a whole is stabilized with respect to crack formation and crack propagation compared to conventional designs.

FIG. 3 shows a sectional view along the section line III-III of the heat shield brick 26 shown in FIG. 2. Here, a view of the heat shield brick 26 in the direction of the transverse axis 45 is shown on the cutting surface. The core area 31 is cuboid or cuboid-like. The edge region 37 completely surrounds the core region 31, the edge region 31 extending from the hot side 35 to the wall side 33. The edge region 37 consists of an edge material 41, the peripheral side surface 49 having the edge material 41. The peripheral side surface 49 is the outermost Boundary surface of the peripheral side 47, which is adjacent to the hot side 35 and the wall side 33. In order to set a reduced thermal conductivity in the edge region 41 compared to the core region 31, the edge material 41 is designed as a porous material with a large number of pores, the porosity of the edge material 41 being specifically set such that the thermal conductivity of the edge material 41 compared to the thermal conductivity of the core material 39 is thereby achieved is lowered to a desired level. The thermal conductivity of the edge material 41 is, for example, less than 60%, in particular less than 50%, of the thermal conductivity of the core material 39. The core material 39 and the edge material 41 can be formed, for example, from the same ceramic base material, in particular a refractory ceramic. This material identity of the base material for the core material 39 and the edge material 41 results in a particularly strong and durable material composite.

A desired porosity for lowering the thermal conductivity in the edge region 37 is set, for example, by mixing suitable pore formers into the ceramic mass, the pore formers being pressed or poured into the region of the blast element defined by the edge region 37. During the sintering process, the pore former evaporates and leaves pores with a predetermined pore diameter distribution and pore density distribution within the edge region 37. The heat shield brick 26 is thus in the edge region 37 with a lower thermal conductivity that deviates from the core material 39, for example with a reduction in the thermal conductivity to less 50% of the core material 39 provided. Along the hot side 35, the axial extent d _{R of} the edge region 37 is less than 20%, in particular between about 5% and 10% of the total axial extent L of the heat shield brick 26. Consequently, in this embodiment, the axial extent d _{κ of} the core region 31 with the Core material 39 significantly larger than the axial extent d _{R of} the edge region 37. The advantages of ^• Core material 39 in the core area 31 with regard to the resistance to high-temperature stress and exposure to a hot medium M, for example a hot gas, are thus largely retained, cracking in particular on the hot side 35 in the core area 31 due to the thermal insulation effect of the porous edge material 41 is largely suppressed even at high temperature loads or temperature changes. A possible crack formation or crack propagation can possibly occur in edge area 37, where this is tolerable.

FIGS. 4 to 7 show further refinements of the heat shield block 26 with modification of the geometry of the heat shield block 26 (see FIGS. 6 and 7) or with variation of the geometry of the core region 31 and edge region 37. In a sectional view, FIG. 4 shows a heat shield element 26 with an edge region 37 which extends from the hot side 35 to the wall side 33, the cross section of the edge region 37 curving towards the wall side 33. Accordingly, the cross section of the core region 31 increases continuously from the hot side 35 to the cold side 33. In contrast, FIG. 5 shows an exemplary embodiment of the heat shield brick 26, in which the edge region 37 forms a partial surface of the peripheral side surface 49 with the edge material 41. The edge region 37 faces the hot side 35 and is at the same time a component of the hot side 35. The peripheral side surface 49 has both the core material 39 and the edge material 41, the edge material 41 facing the hot side 35 and the core material 39 facing the wall side 33 , Depending on the typical load case for the heat shield brick 26, both the geometry of the edge region 37 and the core region 31 and the local heat conduction properties in the edge region 37 can be modified and adapted by setting a corresponding porosity of the edge material 41 in the edge region 37. FIGS. 6 and 7 show different geometries of the heat shield brick 26 in a top view of the hot side 35. In both exemplary embodiments, the geometry of the core region 31 is essentially cylindrical and extends from the hot side 35 to the cold side 33. The outer boundary edge of the heat shield element 26 is 6 of square geometry and FIG. 7 of hexagonal geometry. The edge region 37 essentially results as a complementary volume to the cylindrical core region 31. For the thermal insulation, the edge material 41 has a porosity, so that in the edge region 37 a significantly reduced thermal conductivity compared to the core region 31 is achieved. The core material 39 and the edge material 41 are constructed from identical base material or essentially similar base material, so that the transition from the core region 31 to the edge region 37 is achieved in the form of a materially integral, largely homogeneous material composite, which is chemically identical or similar, but due to the physical effect of the specifically set porosity of the edge material 41 causes the desired lowering of the thermal conductivity from the core area 31 to the edge area 37.

Claims

claims

1. Heat shield brick (26), in particular for lining a combustion chamber wall (24), with a hot side (35) which can be acted upon by a hot medium (M) and a wall side (33) opposite the hot side (35), and with one from the hot side (35) to the wall side (33) extending core area (31) with a core material (39), so that the core area (31) is surrounded by an edge area (37) with an edge material (41) whose thermal conductivity is lower than that of the core material (39).

2. Heat shield brick (26) according to claim 1, so that the thermal conductivity of the edge material (41.) is less than 60%, in particular less than 50%, of the thermal conductivity of the core material (39).

3. Heat shield stone (26) according to claim 1 or 2, since you mark the mark that the edge material (41) is porous, wherein the porosity of the edge material (41) is specifically set so that the thermal conductivity of the Edge material (41) is lowered compared to the thermal conductivity of the core material (39).

4. Heat shield brick (26) according to claim 3, since it is known that the core material (39) and the edge material (41) are formed from the same ceramic base material, in particular a refractory ceramic.

5. Heat shield brick (26) according to one of claims 1 to 4, so that the core material (39) and the edge material (41) form an interlocking material composite.

6. The heat shield brick (26) according to one of claims 1 to 5, so that the axial extent (d _R ) of the edge region (37) is less than 20%, in particular between 5%, along the hot side (35). and 10%, the total axial extent (L).

7. heat shield brick (26) according to any one of claims 1 to 5, characterized ge z e i chne t that the edge region (37) extends from the hot side (35) to the wall side (33).

8. heat shield brick (26) according to any one of claims 1 to 7, characterized ge ge zei chne t, one on the hot side (35) and the wall side (33) adjacent peripheral side (47) having a peripheral side surface (49) at least is partially formed by the edge material (41).

9. Combustion chamber (4) with an internal combustion chamber lining, which has heat shield bricks (26) according to one of the preceding claims.

10. Gas turbine (1) with a combustion chamber (4) according to claim 9.