EP1817147A1

EP1817147A1 - Heat shield element, method and form for the production thereof, hot gas lining and combustion chamber

Info

Publication number: EP1817147A1
Application number: EP05803716A
Authority: EP
Inventors: Holger Grote; Andreas Heilos; Marc Tertilt
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2004-12-01
Filing date: 2005-11-21
Publication date: 2007-08-15
Also published as: US20120228468A1; US9314939B2; WO2006058629A1; US20070289307A1; US8522559B2; US20100213645A1

Abstract

The invention relates to a heat shield element comprising a hot side (113) which is turned towards the hot medium, a cold side (115) which is turned away form the hot medium (115), peripheral sides (117) which connect the hot side (113) to the cold side (115) and a material volume which is defined by the hot side (113), the cold side (115) and the peripheral sides (117), wherein the material volume comprises at least two material areas (119, 121) which are made of different materials. The materials are different from each other at least in respect of their resistance and/or thermal expansion coefficient.

Description

description

Heat shield element, method and form for its manufacture, hot gas lining and combustion chamber

The present invention relates to a heat shield element, in particular a ceramic heat shield element, a method for producing a ceramic heat shield element, a hot gas lining constructed of heat shield elements and a combustion chamber provided with a hot gas lining, which can be designed in particular as a gas turbine combustion chamber. Moreover, the invention relates to a mold for producing a ceramic heat shield element.

The walls of hot gas-carrying combustors, such as gas turbine plants require thermal shielding of their supporting structure against hot gas attack. The thermal shielding can be realized, for example, by means of a hot gas lining upstream of the actual combustion chamber wall, for example in the form of a ceramic heat shield. Such a hot gas lining is usually constructed of a number of metallic or ceramic heat shield elements, with which the combustion chamber wall is lined flat. Ceramic materials are ideally suited for the construction of a hot gas lining compared to metallic materials because of their high temperature resistance, corrosion resistance and low thermal conductivity. A ceramic heat shield is described, for example, in EP 0 558 540 B1.

Due to material-typical thermal expansion properties and the temperature differences typically occurring during operation - such as between the ambient temperature at standstill of the gas turbine plant and the maximum temperature at full load - the thermal mobility particular ceramic heat shields must be guaranteed as a result of temperature-dependent expansion, so that no heat shields destructive thermal stresses by obstructing the temperature-dependent Elongation occur. Expansion gaps are therefore present between the individual heat shield elements in order to enable thermal expansion of the heat shield elements. For safety reasons, the expansion gaps are designed so that they are never completely closed even at the maximum temperature of the hot gas. It must therefore be ensured that the hot gas does not reach the load-bearing wall structure of the combustion chamber via the expansion gaps. In order to block the expansion gaps against the entry of hot gas, these are often flushed with a flowing in the direction of the combustion chamber interior air flow. Air is generally used as sealing air, which at the same time serves as cooling air for cooling retaining clips holding the heat shield elements, which, inter alia, leads to the occurrence of temperature gradients in the region of the edges of a heat shield element. As a result of purging the expansion gaps with sealing air, the peripheral sides delimiting the gaps are cooled as well as the cold side of the heat shield elements. On the other hand, a high heat input due to the hot gas takes place on the hot side of the heat shield elements. Therefore, within a heat shield element, a three-dimensional temperature distribution arises, which is characterized by a temperature drop from the hot side to the cold side as well as by a drop in temperature occurring from central points of the heat shield element to the edges. This is the reason why ceramic heat shield elements, in particular, are also used without them

Touching adjacent heat shield elements to stresses on the hot side, which can lead to cracking and thus adversely affect the life of the heat shield elements.

Typically, the heat shield elements are formed flat in a gas turbine combustor and disposed parallel to the support structure. A temperature gradient, which runs perpendicular to the surface of the support structure, only leads to comparatively low thermal stresses, as long as the ceramic heat shield element in the installed state, a prevention in the direction of the interior of the combustion chamber without obstruction is possible. A temperature gradient parallel to the support structure, such as that which extends from the peripheral surfaces of the heat shield element to the center of the heat shield element, brings about rapidly increased thermal stresses due to the rigidity of plate-like geometries with respect to deformations parallel to their largest projection surface. These result in the cold edges of the peripheral surfaces being put under tension due to their comparatively low thermal expansion from hotter central regions which are subjected to greater thermal expansion. When the material strength is exceeded, this tension can lead to the formation of cracks which originate from the edges of the heat shield element and run in the direction of central regions of the heat shield element.

The cracks reduce the load bearing cross section of the heat shield element. The longer the cracks, the smaller the load-bearing residual cross section of the heat shield element. The thermally induced cracks can be caused by during operation of the

Extend gas turbine system occurring mechanical stresses, which leads to a further reduction of the remaining cross-section and can make the replacement of the heat shield element necessary. Such mechanical loads occur, for example, in oscillating accelerations of the combustion chamber wall, which can be caused by combustion vibrations, ie vibrations in the combustion exhaust gases.

In order to reduce the need for sealing air - and thus thermally induced stresses in heat shield elements - was proposed in EP 1 302 723 Al to arrange flow barriers in the expansion gaps. This can also lead to a reduction of the temperature gradient in the region of the edges. However, the introduction of flow barriers is not always readily possible and also increases the complexity of a heat shield. Alternative approaches are to use metal heat shield elements. Although metallic heat shield elements have a higher resistance to thermal fluctuations and mechanical stresses than ceramic heat shield elements, they require complex cooling of the heat shield, for example in gas turbine combustors, since they have a higher thermal conductivity than ceramic heat shield elements. In addition, metallic heat shield elements are more susceptible to corrosion and, due to their lower temperature stability, can not be subjected to temperatures as high as those of ceramic heat shield elements.

In order to minimize the formation of cracks, it is therefore generally endeavored to minimize the thermal load on the heat shield elements of a heat shield.

At present, it is common to cast or press ceramic heat shield elements. To illustrate the casting or pressing process, a heat shield element and a mold for producing the heat shield element will be described below with reference to FIGS.

The ceramic heat shield element 100 shown in Figure 7 has a hot side 102, which faces the hot gas when the heat shield element 100 in the heat shield of a

Combustion chamber is installed. Opposite the hot side 102 is the cold side 104 which faces the combustion chamber wall to be protected when the heat shield element 100 is installed in a heat shield. In addition, circumferential sides 106, 108 are present, which extend between the hot side 102 and the cold side 104. Two mutually opposite circumferential sides 108 are also provided with grooves 110 which serve to fix the heat shield element 100 to the supporting wall structure by means of retaining clips.

Figure 8 shows in a perspective view of a mold 200 for producing the heat shield element of Figure 7. The mold 200 consists of a number of moldings 202a to 202e, which are inserted into a molding box 203 and held by this in position. The inner surfaces 204, 206, 208 of the molded parts 202a to 202e constitute the molding surfaces for molding the surface of the heat shield member 100. For example, the inner surface 204 serves to form the cold side 104 of the heat shield member 100, the inner surfaces 206 to form the side surfaces 106 without a groove and the inner surfaces 208 for forming the side surfaces 108 with groove 110. The inner surfaces 208 have spring-like projections 210 for forming the grooves 110.

To produce the ceramic heat shield element 100, a ceramic molding compound 220 is introduced into the mold 200 with the mold parts 202a to 202e inserted and then pressed into the mold by means of a punch 212. The molding compound 220 facing surface 214 of the punch 212 thereby forms the hot gas surface 102 of the ceramic heat shield element 100. The pressure necessary for pressing the molding compound 220 requires that the mold 200 is completely closed during pressing, i. The stamp 212 must be formed to fit the mold 200. In addition, the pressing pressure can lead to a springback of the moldings. Fluctuations in the amount of material of the molding compound 220 can also lead to variations in the thickness of the finished ceramic heat shield element.

Alternatively to pressing, the heat shield element 100 can also be cast using the mold 200, i. without a pressing process takes place. However, since the heat shield member 100 is cast horizontally, either the hot side 102 or the cold side 104 is not defined by the mold during casting. The undefined side requires elaborate finishing after casting to produce the desired shape of the heat shield element 100.

Finally, the molds described are not suitable for producing a heat shield element in a single casting or pressing step, which has different material regions with different material properties. That too Manufacture of heat shield elements with reinforcing elements inside is not possible.

The object of the present invention is to provide a heat shield element which has improved cracking properties.

Another object of the present invention is to provide an advantageous heat shield and a combustion chamber equipped with an advantageous heat shield.

In addition, it is an object of the present invention to provide a method for producing advantageous heat shield elements.

Finally, it is an object of the present invention to provide a mold that is advantageous over the described prior art for producing a ceramic heat shield element.

The first object of the invention is achieved by a heat shield element according to claim 1, the second object by a hot gas lining according to claim 7 or a combustion chamber according to claim 8, the third object by a method according to claim 9 and the fourth object by a mold according to claim 14 The remaining claims contain advantageous developments of the invention.

A heat shield element according to the invention has a hot side to be turned towards a hot medium, a cold side facing away from the hot medium and peripheral sides connecting the hot side to the cold side. The hot side, the cold side and the peripheral sides limit the material volume of the heat shield element. In the heat shield element according to the invention, the material volume comprises at least two material regions made of different materials, wherein the materials differ at least in their strengths and / or thermal expansion coefficients.

With suitable thermal expansion coefficients, the thermal expansion of the material regions can be influenced in a targeted manner. In particular, if material areas provided for relatively high operating temperatures have a relatively low coefficient of thermal expansion and material areas provided for relatively low operating temperatures have a relatively high coefficient of thermal expansion, the stresses within the heat shield element can be reduced during operation of a heat shield and thus reduce the tendency for cracking. In this case, a relatively low or relatively high operating temperature is to be understood in each case with regard to the operating temperature for which the material of the other material regions of the heat shield element is designed. The same applies analogously to the relatively low and the relatively high thermal expansion coefficients.

By different strengths of different material areas, the length of emerging cracks can be influenced in an advantageous manner. A firmer material leads to a more difficult crack propagation and thus in particular to a reduction in the length of the resulting cracks. Short, outgoing from the edges cracks, which penetrate only slightly towards the center of the heat shield element (up to about 10% of the length of the heat shield element), the efficiency of the heat shield element, both theoretically and experience not significantly affect. The combination of solid and less solid material in a heat shield element allows the use of the solid material even if the solid material has a lower thermal capacity compared to the less solid material. It may therefore be particularly advantageous if the material in material areas which are provided for relatively high operating temperatures, has a relatively low strength and the material in material areas, the are provided for relatively low operating temperatures, has a relatively high strength. A relatively low or relatively high strength is to be understood here in each case with respect to the strength of the material of the other material areas of the heat shield element.

The last-mentioned embodiment also makes it possible to optimally adapt the material of those material regions which are intended for relatively high operating temperatures to the high operating temperatures without having to pay too much attention to the strength of the material used. In turn, the material of those areas of material intended for the relatively low operating temperatures can be optimized for strength without having to pay too much attention to its thermal properties.

A particularly advantageous heat shield element is obtained when material areas provided for relatively high operating temperatures have both a relatively low thermal expansion coefficient and a relatively low strength, and material areas provided for relatively low operating temperatures have both a relatively high coefficient of thermal expansion as well as having a relatively high strength. In this case, on the one hand, the cracking rate can be reduced, and on the other hand, a spread of the resulting cracks can be counteracted.

In a further embodiment of the heat shield element according to the invention, at least one material region of a material with a relatively low coefficient of thermal expansion and / or relatively low strength adjoins the hot side of the heat shield element, whereas at least one material region consists of a material having a relatively high thermal expansion coefficient and / or relative high strength adjacent to the cold side of the heat shield element. On the hot side, during the transition from the ambient temperature (for example, when a gas turbine binenanlage) to maximum operating temperature (for example, at full load of a gas turbine plant) greater temperature differences than on the cooled cold side of the heat shield element. The different temperature differences are compensated in the described embodiment in that the thermal expansion coefficient of the heat shield element in the region of the hot side is lower than in the region of the cold side. With a suitable choice of the coefficients of thermal expansion, the temperature-induced material expansion in the region of the cold side can be adapted to the temperature-induced material expansion in the region of the hot side, whereby material stresses in the heat shield element can be reduced. The material which is cooler during operation of the gas turbine plant in a material area adjoining the cold side can also be optimized with regard to its strength. In this case, for example, can also be accepted that this material has a lower resistance to high temperatures than the adjacent to the hot side material.

In addition, at least one material region made of a material having a relatively high coefficient of thermal expansion and / or relatively high strength may be adjacent to the circumferential surface of the heat shield element and at least one material region may be made of a material having a relatively low thermal content

Expansion coefficient and / or relatively low strength from the circumferential surfaces seen from the inside of the material volume to be arranged. In this embodiment, moreover, a material region of a material with a relatively low coefficient of thermal expansion and / or relatively low strength can adjoin the hot side and a material region made of a material with a relatively high coefficient of thermal expansion and / or relatively high strength can adjoin the cold side. Since the heat shield elements of a heat shield are cooled in particular in the area of the peripheral surfaces due to the blocking air flow, high heat strains occur in heat shield elements with a homogeneous coefficient of thermal expansion in the region of the peripheral surfaces. reason arise over the rest of the heat shield element particularly low operating temperatures. The fact that the coefficient of thermal expansion is increased in the area of the circumferential surfaces in comparison to the interior (seen from the peripheral surfaces) of the heat shield element, the voltages occurring can be reduced. On the other hand, the high strength of this range can effectively prevent the propagation of cracks once it has formed. However, the material in the area of the peripheral surfaces preferably has both a high coefficient of thermal expansion and a high degree of strength.

In a further development of the heat shield element according to the invention, mutually adjacent material regions made of materials with different coefficients of thermal expansion and / or different strengths are configured in such a way that there is a zone of the transition from one material region to the other. In this zone, a smooth or continuous transition from the thermal expansion coefficient and / or the strength of the one material to the coefficient of thermal expansion and / or the strength of the other material takes place. Due to the flowing and matched transition in particular of the thermal expansion coefficient, the risk of destruction of the heat shield during the manufacturing process, in particular during the sintering process, which takes place at elevated and approximately homogeneous temperature, can be reduced.

The heat shield element according to the invention can in particular be designed as a ceramic heat shield element.

The reduced voltage formation due to different coefficients of thermal expansion when spatial temperature gradients occur within the ceramic heat shield element leads to a reduced cracking tendency. The presence of a material area with a more rigid material reduces in a ceramic heat shield the Risk of training long cracks. In particular, if the ceramic heat shield element has both material areas whose materials have different coefficients of thermal expansion, and material areas whose materials have different strengths, therefore, a longer life of the heat shield elements can be achieved, resulting in a reduction of replacement rates of heat shield elements in hot gas linings.

An inventive heat shield, in particular as a

A heat shield for a gas turbine combustor can be configured comprises a number of under Dehnspaltbelassung at their peripheral surfaces of adjacent heat shield elements and a barrier fluid supply for supplying a the expansion column against the entry of hot medium blocking

Blocking fluid flow. As a barrier fluid, in particular sealing air can be used. The heat shield according to the invention is characterized in that the heat shield elements are designed as heat shield elements according to the invention.

A combustion chamber according to the invention is lined with a heat shield according to the invention. It can be designed in particular as a gas turbine combustion chamber.

In the method according to the invention for producing a ceramic heat shield element, pressing or casting of a base material mixture takes place and subsequent sintering of the pressed or cast base material mixture. The method according to the invention is characterized in that prior to sintering the pressed or cast base material mixture, the thermal expansion coefficients and / or the strength of different material regions are adjusted.

By adjusting the thermal expansion coefficients of different material regions, the resistance of a heat shield element produced by means of the method according to the invention to temperature gradients can be determined increase within the heat shield element, whereas by adjusting the strength of the expansion of cracks can be prevented, so that as a result only shorter cracks arise than in the prior art.

The adjustment of the coefficients of thermal expansion and / or the strength can be carried out, for example, by using base material mixtures having different compositions during pressing or casting for the corresponding material regions. In particular, the composition of the base material mixture can be changed over smoothly from one composition to the other composition, so that a smooth transition of the thermal expansion coefficient or the strength can be realized.

Alternatively, it is also possible to adjust the thermal expansion coefficients or the strengths by after the pressing or casting of the base material mixture and before sintering a post-treatment of at least one material region takes place, which changed after sintering compared to the rest of the base material mixture, For example, it should have a relatively low coefficient of thermal expansion, or a modified resistance to the rest of the base material mixture. The Nachbehan- your example, by the at least one nachzubehandelnde material area is soaked with a liquid. This procedure permits a particularly good definition of material regions which should have a thermal expansion coefficient which is changed in relation to the rest of the base material mixture and / or a changed strength.

If the heat shield element is produced by means of a casting process in the method according to the invention, then a mold according to the invention can be used for casting, in particular, as described below. A mold according to the invention for producing a ceramic heat shield element has a mold shell comprising a number of molding surfaces and a pouring port for pouring a ceramic material. The mold shell is designed as a one-piece mold shell during casting and the pouring opening is formed as an opening in one of the mold surfaces. The term "one-piece mold shell during casting" should not be understood in this context to mean that the mold shell is monolithically formed from a single piece, but rather that the mold shell is formed in a single piece

Pouring the casting mass not two elements not firmly connected to each other, for example. From only used in a molding box molded parts and a stamp as described with reference to the figures 8, 9a and 9b, there is. However, the mold according to the invention may be composed of a number of individual parts, as long as they are firmly connected to each other during casting of the molding compound. In contrast to the form described above no mold box is necessary in the inventive form. Such a molding box in particular hinders the production of graded and / or reinforced

Heat shield elements, since the mold parts are inaccessible arranged in the inner mold box during the Hersteilens a heat shield element.

When the mold is composed of a plurality of parts to be firmly bonded together for the molding process for forming the one-piece mold shell, easy removal of the cured heat shield element by detaching the individual parts from each other is possible.

In contrast to the prior art mold in which one side of the mold is completely missing during pouring, in the mold according to the invention there is a mold surface with a pouring opening for feeding the mold. In other words, the molding surface in which the pouring opening is present determines the corresponding surface of the heat shield element at least partially. With the mold according to the invention, therefore, all surfaces of the heat shield element can at least approach be formed without a pressing of the heat shield element would be necessary. The rudimentary molding surface in the region of the pouring opening leads to the fact that superfluous casting material present in the region of the inlet opening after hardening with the aid of the

Form surface formed approach the heat shield element surface can be removed as a reference surface. The removal of excess material and the finishing of the heat shield element is therefore possible with relatively little effort.

In addition, the dimensions of the molded heat shield element do not depend on the cast-in amount of material when using the mold according to the invention, since no pressing takes place. Since in the pressing process according to the prior art, the mold is completely closed, there is no possibility for the casting material to emerge from the mold. Fluctuating amounts of casting material therefore lead to the production of heat shield elements of different thickness. On the other hand, in the mold according to the invention, excess casting material can escape through the pouring opening, without thereby affecting the dimensions of the heat shield element. In addition, occurs in casting and no springback of the mold under pressing pressure. The mold according to the invention therefore makes it possible to produce heat shield elements with reduced tolerances.

The mold according to the invention comprises, in particular, molding surfaces for forming a large-area first surface and a large-area second surface, as well as molding surfaces for molding peripheral surface areas which extend from the first surface to the second surface in comparison to these. The pouring port is then formed in a mold surface for molding one of the peripheral surfaces.

In a particular embodiment of the mold according to the invention, at least one separating element is provided, with which different regions can be separated from each other in the interior of the mold shell. The separating element is designed in this way and to arrange in the mold shell that it can be removed again from the interior of the mold shell before the ceramics are cast without the mold being opened. In particular, this embodiment makes it possible to produce graded heat shield elements, that is to say such heat shield elements, which comprise at least two regions which consist of materials having different material properties.

The preparation of a graded heat shield element can then be done, for example, by the inserts are inserted into the mold before pouring the ceramic material, then the ceramic material is poured and after the pouring of the ceramic, the bays are removed again. After removal of the inserts, the different ceramic material can come into contact with each other and thus form a cohesive connection during curing. It is also possible that the adjoining materials mix on removal of the separating elements in the boundary region, so that after curing, a heat shield element is present, in which the two materials have a smooth transition into each other.

The at least one separating element can in particular be designed as a push-in for insertion into the mold shell through the pouring opening. In particular, there may be an insert which separates the interior of the mold shell into a region facing the molding surface for molding the large-area first surface and an area facing the molding surface for molding the large-area second surface. This makes it possible, for example, to produce ceramic heat shield elements in which the cold side has material properties other than the hot side, for example a different strength or a different thermal expansion coefficient.

Another possibility is to provide two inserts, which cover the interior of the mold shell in a central area and in two areas opposite each other Form surfaces facing the molding of peripheral surfaces of the heat shield element, separate. With this embodiment, it is possible to produce heat shield elements which have different material properties in the region of two peripheral sides than in the region lying therebetween, for example other thermal expansion coefficients or a different strength.

In a further embodiment of the form according to the invention, this can comprise at least one retaining element to be inserted into the interior of the shell mold. The retaining element is designed and arranged such that it can fix a body, for example a reinforcing element, in the interior of the shell mold and that it can be removed from the interior of the shell even before the cast ceramic material has hardened. For example. may be present as holding elements retaining pins, which can be moved from the outside of the shell mold inside the shell mold and extended again. In particular, the retaining pins may be arranged in the molding surface for molding a large-area first surface and / or in the molding surface for molding a large-area second surface.

By means of the holding elements, bodies such as, for example, reinforcing elements can be held in the interior of the mold when the ceramic material is poured in. After the ceramic material is poured in, the holding elements can be removed from the interior of the mold, so that the body is held solely by the surrounding ceramic material. After curing, the body forms a body cast into the ceramic heat shield element. In this way, for example, high-strength reinforcing elements can be introduced into a ceramic heat shield element.

Further features, properties and advantages of the present invention will become apparent from the following description of embodiments with reference to the accompanying figures. FIG. 1 shows a heat shield element in a perspective view.

Figure 2a shows a first embodiment of the heat shield element shown in Figure 1 in a section along the line A-A.

FIG. 2b shows a modification of that shown in FIG. 2a

Heat shield element in a section along the line B-B of Figure 1.

Figure 3 shows a second embodiment of the heat shield element shown in Figure 1 in a section along the line A-A.

Figure 4 shows a third embodiment of the heat shield element shown in Figure 1 in a section along the line A-A.

FIG. 5a shows a first step of a first production method for a heat shield element according to the invention.

FIG. 5b shows a second step of the production method from FIG. 5a.

FIG. 5 c shows an alternative variant of the method illustrated in FIGS. 5 a and 5 b.

FIG. 6a shows a first step of a second production method for a heat shield element according to the invention.

FIG. 6b shows a second step of the method shown in FIG. 6a.

Figure 7 shows a ceramic heat shield element in a perspective view. Figure 8 shows schematically a mold for producing a heat shield element, as shown in Figure 7, in a perspective view.

FIG. 9a shows the press mold shown in FIG. 8 in a sectioned side view.

Figure 9b shows the mold shown in Figure 8 in a plan view.

FIG. 10 shows the individual parts of a first exemplary embodiment of the mold according to the invention.

FIG. 11 shows the individual parts of a second exemplary embodiment of the mold according to the invention.

FIG. 12 shows the individual parts for a third exemplary embodiment of the mold according to the invention.

FIG. 13 shows the form of the third exemplary embodiment in a side view.

Figure 14 shows the shape of the third embodiment in a plan view.

FIG. 15 shows an opened mold according to the invention with a ceramic heat shield element arranged therein.

FIG. 16 shows a mold shell with it arranged

Slots for separating various areas in the interior of the shell mold.

FIG. 17 shows a mold shell with a feed arranged therein for separating different regions in the interior of the mold shell. FIG. 1 shows a perspective view of a ceramic heat shield element 501 according to the invention. The heat shield element 501 has a hot side 503 which, after installation of the heat shield element 501 in a heat shield, faces the hot medium. Opposite the hot side 503 is the cold side 505 of the heat shield element 501, which, after installation in a heat shield, faces the supporting structure of the combustion chamber wall and thus faces away from the hot medium. Hot side 503 and cold side 505 are connected to each other via first peripheral surfaces 507 and second peripheral surfaces 509. The second peripheral surfaces 509 have grooves 511 into which retaining clips (not shown) connected to the support structure of the combustion chamber wall can engage to hold the heat shield element in position after installation in a ceramic hot gas liner. By contrast, the first circumferential flats 507 have no groove.

The hot side 503, the cold side 505, the first peripheral surfaces 507 and the second peripheral surfaces 509 enclose the material volume of the heat shield element, which provides the thermal shielding effect.

A first embodiment of the heat shield element according to the invention is shown in Figure 2a in section. The section runs along the line AA from FIG. 1. The hot side 513, the cold side 515 and the groove-free peripheral surfaces 517 of the heat shield element 510 of the first embodiment can be seen. The heat shield element 510 has a first material region 519 and second material regions 521, which differ from the material region 519 by their thermal expansion coefficient. The thermal expansion coefficient of the material regions 521 is greater than the thermal expansion coefficient of the material region 519. In this sense, the material region 519 has a relatively low thermal expansion coefficient, whereas the material regions 521 have a relatively high coefficient of thermal expansion. When constructing a heat shield, for example for a gas turbine combustor, the load-bearing structure of the combustion chamber wall is lined with a number of heat shield elements 510 area-wide. In this case, the heat shield elements 510 are attached to one another in such a way that expansion gaps remain between adjacent heat shield elements 510. These expansion gaps serve to allow expansion of the heat shield elements 510 during operation of the combustion chamber due to the high operating temperatures without the heat shield elements 510 touching each other.

In order to prevent passage of the hot medium, such as hot combustion gases, through the expansion gaps to the supporting structure of the combustion chamber wall, the expansion gaps are flushed with sealing air, which simultaneously serves to cool the retaining clips holding the heat shield elements 510. For this reason, lower temperatures prevail at the first peripheral surfaces 517, which are surrounded by the restricted air flow, and the second peripheral surfaces (also not visible in FIG. 2a) during operation of the combustion chamber than in the central region 513 of the heat shield element 510. Therefore, during operation of the combustion chamber the centrally located material region 519 of a conventional heat shield element experiences a higher thermal expansion than the material regions 521 located in the region of the peripheral surfaces. In the low temperature regions, which are positively connected to the region of higher temperature, tensile stresses are thus formed. In the areas of higher temperature, the compressive stresses occur accordingly. In other words, the relatively cool material regions 521 in a conventional heat shield element would be subject to stress due to their relatively low thermal expansion from the hot central region 519 experiencing greater thermal expansion, and could crack when exceeding the material strength. The cracks would emanate from the edges of the heat shield and extend toward the heat shield interior. Such Cracking can reduce the life of a heat shield element.

In the heat shield element 510 according to the invention, the stresses described with reference to a conventional heat shield element are reduced, in particular in the cool peripheral regions, since the material regions 521 have a higher coefficient of thermal expansion than the central material region 519. The higher temperature of the central material region 519 thus becomes the larger thermal expansion coefficient of the material areas 521 in the region of the peripheral surfaces 517 balanced.

The thermal expansion coefficients of the material regions 519 or 521 and the extent of these material regions in the material volume of the heat shield element 510 can be numerically optimized in such a way that the stresses in the heat shield element 510 are minimized. For example, the expansion of the material regions 521 can be determined with relatively high coefficients of thermal expansion, by first performing a calculation of the temperature field which is set in the desired operating state under corresponding boundary conditions in the heat shield element 510. Subsequently, based on this result, the size of the regions 521 for the selected coefficient of thermal expansion can be adjusted so that this minimizes the stresses in the heat shield element 510. Of course, the thermal expansion coefficients and the expansions of the material regions can be optimized simultaneously. However, it is also possible to specify the extent, for example, of the circumferential material regions 521 and to find suitable thermal expansion coefficients by means of an optimization.

In FIG. 2 a, in the area of the groove-free peripheral surfaces 517 of the heat shield element, material regions 521 with a thermal expansion coefficient increased compared to the central material region 519 and reduced thermal conductivity are shown. available. Additionally or alternatively, the heat shield element 510 according to the invention can also have material regions 520 with an increased thermal expansion coefficient and reduced thermal conductivity in the region of the second circumferential surfaces compared to the central material region 519, ie in the region of the peripheral surfaces provided with grooves 518 (FIG.

A second embodiment of the heat shield element according to the invention is shown in Figure 3 in section. The section runs along the line A-A shown in FIG. Accordingly, the hot side 613, the cold side 615 and the groove-free peripheral surfaces 617 of the heat shield element 610 can be seen.

The heat shield element 610 has on the hot side a material region 619 with a relatively low coefficient of thermal expansion and / or a relatively low thermal conductivity. On the cold side, it has a material region 621 with an increased thermal expansion coefficient, increased thermal conductivity and / or increased mechanical load capacity compared to the hot-side material region 619. In addition, the material of the cold side material region is selected so that it has a higher strength than the material of the hot side material region. The thermal resistance of the cold-side material region does not require as great a weight as the thermal resistance of the hot-side material region, which has properties particularly adapted to the hot gas conditions. Due to the increased strength of the cold-side material area, the strength of the heat shield element increases overall. The thickness of a material range can be from a few millimeters up to about 40 mm. In the case of a thin material region, the respective other material region is correspondingly thicker and vice versa.

The embodiment of the latter embodiment takes into account the fact that the hot side 613 of a heat In the heat shield element 610, therefore, a temperature gradient forms from the hot side 613 to the cold side 615. The lower temperature of the cold side material region 621 is then compensated during operation of the combustion chamber by its higher thermal expansion coefficient than the hot side material region 619. Voltages due to the temperature gradient can therefore be reliably avoided. In addition, the increased strength of the heat shield element causes once formed cracks to not spread so easily towards the center of the heat shield element.

As the material components contain both the hot side

Material area as well as the cold-side material area as main components silicon oxide (SiO ₂ ), corundum (aluminum oxide Al ₂ O ₃ ). In addition, zirconia (zirconium oxide, ZrO ₂ ), silicon carbide (SiC) and silicon nitride (Si ₃ N ₄ ) are present. In addition, lanthanides are present as doping.

The cold-side material region additionally has metallic phases, for example iron (Fe). The material properties of the different material areas are influenced by the differences in the percentage compositions of the constituents and by suitable choice of the dopants and additional constituents (once with and once without Fe).

In a variant of this, the hot-side material region can be produced from a material mixture having a weight fraction of more than approximately 50% aluminum oxide and a weight fraction of less than 50% aluminum silicate, such that the hot-side material region of the fired heat shield element of a refractory lining represents a percentage by weight of more than about 50% and less than about 90% alumina and / or a weight fraction of more than about 10% and less than about 50% aluminum silicate. In addition, the hot-side material mixture may have a weight fraction of less than about 10% colloidal silica solution, which silica solution preferably contains a weight fraction of more than about 30% solids, may be added. Also, a liquid, in particular water, with a weight fraction of more than about 1% and less than about 10% can be added to the material mixture, as well as reactive alumina with a weight fraction of less than about 30%, in particular less than about 25%, to achieve the desired properties of the hot side material region of the two-layered heat shield element.

The cold side material region can be made from a material blend having a weight fraction greater than about 50% silicon carbide and a weight fraction less than about 50% aluminum silicate. In the same ratio as the material mixture on which the hot-side material region is based, it is also possible to add silicic acid solution, water and reactive alumina to the cold-side material mixture. Particularly advantageously, the material mixture for the cold side material region has a weight fraction of more than approximately 5% and less than approximately 20% aluminum oxide and a weight fraction of more than approximately 5% and less than approximately 30% microsilica in order to achieve the different properties of the hot side and cold-side material areas.

A third embodiment of the heat shield element according to the invention is shown in Figure 4 in section. The section runs along the line AA shown in FIG. Accordingly, the cold side 713, the hot side 715 and the groove-free peripheral surfaces 717 of the heat shield element 710 can be seen. The heat shield element 710 has a first, hot-side material region 719 with a first coefficient of thermal expansion, peripheral second material regions 721 with a second thermal expansion coefficient and a cold-side material region 723 with a third coefficient of thermal expansion. The second and third thermal expansion coefficients also be identical. By a suitable choice of the coefficients of thermal expansion of the individual material regions, stresses which occur due to temperature gradients in the interior of the heat shield element 710 can be reliably minimized. In addition, the material areas can also have different strengths.

Further combinations of material areas with mutually different thermal and / or mechanical properties are possible, for example a combination of all the material areas mentioned in the exemplary embodiments described above.

In all three embodiments of the inventive heat shield element shown here are relatively abrupt

Transitions between the different material areas and thus relatively abrupt transitions between different thermal expansion coefficients shown. However, the regions with different coefficients of expansion should, if possible, not be in the form of sharp limits of material properties, but rather in the form of smooth transitions of the material properties in order to avoid the risk of destruction of the heat shield during the manufacturing process, especially during sintering homogeneous temperature takes place, to avoid.

It can be mathematically determined and optimized for the particular application, as the variation of the thermal expansion coefficient and / or the strength must be carried out, so that neither threatens destruction of the heat shield element during the sintering process, but at the same time an optimal effect to avoid the voltage formation in the operating state and to suppress the crack propagation in the material is achieved. From this it is possible, for example, to derive an optimum casting or pressing mold for the production of a green body, that is to say a precursor of the heat shield element made of a polymer-ceramic material in which a partial crosslinking of the polymer is present. Any changes in shape of the heat shield element during the sintering process can be compensated.

An exemplary embodiment of a method for producing a heat shield element according to the invention will be described below with reference to FIGS. 5a and 5b. FIG. 5a shows a first step of the production method, FIG. 5b shows a second step. The method includes casting material blends into a mold 840 so as to form a green body, and then sintering the green compact to complete the ceramic heat shield element.

The casting of the material mixtures is shown in FIGS. 5a and 5b. First, a mixture of materials 821 having a first composition is poured into the mold 840 (Figure 5a). Thereafter, a material mixture 819 having a second composition is poured over the first material mixture 821. For example, the material mixtures described with reference to the second embodiment can be used. The consistency of the material mixtures is such that no complete mixing of the two material mixtures occurs. However, mixing at the interface 820 is desirable.

The compositions of the material mixtures 819 and 821 are selected so that the material mixture 819 after sintering has a lower coefficient of thermal expansion than the material mixture 821.

Although mixing of the material mixtures 819, 821 in the region of the interface 820 is desired in the described production method, however, a heat shield element according to the invention can also be produced without such mixing. After sintering of the cast heat shield element, a heat shield element is obtained, as shown in FIG. In the variant of pouring a heat shield element according to the invention described with reference to FIGS. 5b and 5b, it is cast horizontally, ie either the part of the casting mold serving for forming the hot side or the part of the casting mold serving for forming the cold side, represents the underside of the casting mold In FIGS. 5a and 5b, for example, the part of the casting mold used to form the cold side represents the underside.

In an alternative variant of the casting, the casting of the heat shield element takes place when the casting mold is stationary, i. that part of the casting mold which forms the cold side and that part of the casting mold which forms the hot side are side walls of the casting mold, whereas the lower face of the casting mold is a part of the mold which forms one of the peripheral surfaces of the heat shield element. This variant of the casting is shown in Fig. 5c, which shows a standing mold in plan view. In standing mold 845, stencils 846, 847 may serve to separate different regions 848, 849, 850 of mold 845 from each other. In the various areas of the 848, 849, 850 different material mixtures are poured. For example, three different material mixtures can be used with the mold from FIG. 5c, namely one for the regions 848, one for the region 849 and one for the region 850. However, it is also possible for the two separate sections 848 to also be different To use material mixtures, so that a total of four material mixtures are used. In addition, as described with reference to FIGS. 5a and 5b, different material mixtures can also be successively filled in one area.

After casting, the templates are removed to effect bonding of the cast material mixes. Again, the consistency of the material mixtures is selected such that in the region of the interfaces after the removal of the templates, a mixing of the material mixtures. Of course, it is possible to use templates for dividing the casting mold into different material regions, even when the die is lying.

A second manufacturing method for heat shield elements according to the invention will now be described with reference to FIGS. 6a and 6b. In this method, a material mixture 919 is placed in a mold 940, 950 and then pressed. The result is a green body 910 of the heat shield element. This green compact 910 is shown in FIG. 6b. It can be seen the hot side 913, the cold side 915 and the groove-free peripheral surfaces 917 of the green body 910. In the area of the groove-free peripheral surfaces 917, the green body 910 is impregnated with a liquid that influences the sintering process. The liquid is selected so that the impregnated regions 921 after sintering have a higher coefficient of thermal expansion and / or a higher strength than the non-impregnated region 919.

Optionally, the grooved circumferential surfaces of the green body 910 (not visible in FIG. 6b) may also be soaked to increase the thermal expansion coefficient and / or the strength of the respective regions. The result of the method described with reference to FIGS. 6a and 6b is a heat shield element as shown in FIG.

Even when the heat shield element is pressed, the mold can be filled horizontally or vertically and the material mixtures can be filled using stencils. The mold can thereby - as well as the mold when pouring a heat shield element - are placed or filled at any angle.

Although the manufacture of a heat shield element as shown in FIG. 3 is described by way of example with reference to FIGS. 5a and 5b, it is also possible to use FIG the same process heat shield elements, as shown in Figures 2 or 4, produce. The same applies to the method which has been described with reference to FIGS. 6a and 6b. Even with this method, it is not only possible to produce a heat shield element as described with reference to FIG. Rather, it is also possible with this method to produce heat shield elements, as shown in Figures 3 or 4.

In the preceding embodiments, mainly material regions with different coefficients of thermal expansion were described. It should therefore be noted that even in those exemplary embodiments in which only different thermal expansion coefficients have been described with regard to the material regions, these material regions may additionally or alternatively also have different strengths.

A first exemplary embodiment of a mold according to the invention for producing a ceramic heat shield element, as shown schematically in FIG. 1, is shown in FIG. 10. The FIGURE shows the individual parts of the mold shell, which are firmly but detachably connected to each other before casting a ceramic material. The connection takes place in the present embodiment by means of clamping connections, but it can just as well by means of other releasable connections, for example. Screw connections, brought about. However, clamping connections have the advantage over screw connections that they can be manufactured and loosened without tools.

The individual parts which can be connected to the mold shell comprise the shell elements 1 and 3 which have molding surfaces 2 and 4 with which the hot side 102 and the cold side 104 of the heat shield element 100 are formed.

Furthermore, side parts 5 and 7 are present, which each have a spring-like projection 6, 8. These two items form the molding surfaces for the grooves 110 provided circumferential sides 108 of the heat shield element 100. In this case, the spring-like projections 6, 8 serve to form the grooves.

In addition, the mold shell comprises a bottom element 9 which has a forming surface 10 for forming one of the peripheral sides 106 of the heat shield element 100 without grooves. When casting the heat shield element, the shape is on the bottom element. 9

Finally, there are two shell elements 11, 13, which lie opposite the bottom element 9 in the composite shell mold. The two shell elements 11, 13 are provided with recesses 12, 14, which are arranged such that they form a pouring opening for pouring the ceramic material after assembly of the two shell elements 11, 13. In addition, these two shell parts each have a forming surface 15, 17, are formed with the edge regions of the second peripheral side 106 without a groove. Furthermore, in the recesses webs 16, 18 are provided, with which the pouring of the assembled shell mold is divided into two partial openings. If the ceramic material is poured only in one partial opening, air can escape from the interior of the shell mold through the other partial opening.

FIG. 15 shows the mold shell in the partially assembled state after the casting of a ceramic heat shield element 100. The shell parts 4, 5 and 7 from FIG. 10 can be seen. FIG. 15 shows in particular that parts of the peripheral side 106 are formed during casting in the region of the pouring opening. Casting residues 112 on the ceramic heat shield element 100 are mechanically removed after curing. The already formed parts of the peripheral side 106 can serve as a reference surface.

For firmly interconnecting the shell elements, the shell element 1 is equipped with four clamping elements 19, which engage with hooks 20 of the shell element 3. can be brought and tightened. In order to prevent slippage of the side elements 5, 7, of the base element 9 arranged between the shell elements 1 and 3 and of the shell elements 11 and 13 forming the pouring opening during clamping, there are formed form protrusions 21 with various form protrusions or recesses of other shell elements interact positively. In addition, pins 22 are present, which engage in receptacles 23 of adjoining mold elements and thus prevent a displacement of the mold elements against each other.

The mold shown in FIG. 10 also includes slots 24 which can be inserted through the pouring hole into the interior of the mold tray to separate different areas inside the mold tray. To guide the slots 24 when inserted into the composite shell mold 1 guide grooves 25 are present in the shell element. In addition, the shell element 11 has guide recesses 26 for guiding the inserts 24.

The inserts 24 are inserted into the composite shell mold prior to casting a heat shield element, so that in its interior regions which are adjacent to the shell elements 5, 7 with the spring-like projections 6, 8 are separated from a central region. In the to the at the

Shell elements 5, 7 adjacent areas, a different ceramic material is poured than in the central region of the shell mold. After pouring the inserts 24 are removed from the shell mold, so that the two materials can mix together in the border area and produce a cohesive connection during curing. In this way, graded heat shield elements can be produced.

The composite shell mold with Einschub arranged therein is shown in Fig. 16.

A second embodiment of the mold according to the invention is shown in FIG. Like FIG. 10, FIG. 11 shows the Mold shell of the mold in individual parts. To avoid repetition, only the differences from the form shown in FIG. 10 will be discussed. The reference numerals of the shell elements shown in Figure 11 are consistent with the reference numerals of the corresponding shell elements of Figure 10.

In contrast to the shape shown in FIG. 10, the mold shown in FIG. 11 comprises only one insert 34, which is suitable for bringing the interior of the composite molding shell into a hot-side region, i. a portion adjacent to the shell member 1 having the molding surface 2 for forming the hot side 102 and a cold side portion, i. an area adjacent to the shell member 3 with the molding surface 4 for molding the cold side 104 separates. Accordingly, no guide grooves are present in the shell elements 1 and 11. Instead, the spring-like projections 6 and 8 have guide grooves for guiding the insert 34.

The composite shell mold of Figure 11 with therein arranged insertion is shown in FIG. 17.

A third embodiment of the mold according to the invention is shown in FIG. 12. Like FIGS. 10 and 11, FIG. 12 shows the mold shell disassembled into its individual parts. The individual parts are designated by the same reference numerals as the corresponding individual parts from FIGS. 10 and 11. In order to avoid unnecessary repetition, reference will be made here only to the differences from the shapes shown in FIGS. 10 and 11.

The mold shell of Figure 12 is not intended for the insertion of inserts. Accordingly, the shell elements also have no guide grooves for such molded parts.

Instead, in the shell elements 1 and 3 retaining pins 40 are present, which are arranged to be movable so that they in composite shell mold from the exterior of the shell elements 1, 3 from are introduced into the interior of the mold shell. For this purpose, a retaining pin plate 42 supporting the retaining pins 40 is arranged on the outside of the shell molds 1, 3, the distance of which can be varied from the outside of the respective shell element 1, 3 by means of a crank 44 or by means of an automated embodiment of the retaining pins 40. When the retaining pin plate 42 abuts completely on the outside of the shell element 1, the retaining pins 40 protrude maximally into the interior of the shell mold. This state is illustrated with reference to the shell element 1 in FIGS. 12 and 13. On the other hand, if the retaining pin plate 42 has its greatest distance from the outside of the shell element 1, then the retaining pins 40 are completely sunk in the wall of the shell element, so that they no longer protrude into the interior of the shell mold. This state is shown in Fig. 14 and in Figure 6 in the shell element 3.

The retaining pins 40 can be used as holding elements to, for example, to keep reinforcing elements during the pouring of the ceramic material in the interior of the shell mold. The

Holding can be accomplished, for example, solely by pressing the holding pins 40 against the reinforcing element from two opposite sides and fixing the latter by means of the resulting friction. Alternatively, it is also possible to provide openings in the reinforcing element, in which the retaining pins 40 can engage to hold the reinforcing element.

As reinforcing elements, in particular planar reinforcing elements can be introduced into the interior of the shell mold, which for example extend parallel to the hot side or cold side 102, 104 of the heat shield element 100 to be formed. However, rod-shaped or bone-shaped reinforcing elements can also be introduced into the interior of the shell mold, which extend substantially along the shell elements 5, 7, 9, which form the peripheral sides 106, 108 of the heat shield element 100. In the finished heat shield The reinforcing elements then extend along the peripheral sides 106, 108.

After fixing the reinforcing elements in the interior of the shell mold, a ceramic material is poured into the shell mold. Subsequently, the retaining pins 40 are withdrawn from the interior of the shell by means of the crank 44 or a pull-out mechanism. This condition is shown in FIG. The reinforcing elements are then fixed in their position solely by the introduced ceramic material.

Claims

claims

A heat shield element (501, 510, 610, 710, 910) having a hot side (503, 513, 613, 713, 913) facing a hot medium

a cold side (505, 515, 615, 715, 915) to be turned away from the hot medium

- The hot side with the cold side connecting peripheral sides (508, 509, 517, 617, 717, 917) and

a volume of material bounded by the hot side (503, 513, 613, 713, 913), the cold side (505, 515, 615, 715, 915) and the peripheral sides (507, 509, 517, 617, 717, 917) characterized in that the material volume comprises at least two material regions (519, 521, 619, 621, 623, 719, 721, 919, 921) made of different materials, wherein the materials differ from each other at least in their strengths and / or thermal expansion coefficients.

2. heat shield element (501, 510, 610, 710, 910) according to claim

1, characterized in that provided for relatively high operating temperatures material regions (519, 619, 719) are made of a material of relatively low strength and / or relatively low thermal expansion coefficient, whereas provided for relatively low operating temperatures material regions (521, 621, 721, 723 ) are made of a material of relatively high strength and / or relatively low thermal expansion coefficient.

3. heat shield element (501, 510, 610, 710, 910) according to claim 2, characterized in that at least one made of a material having a relatively low strength and / or a relatively low coefficient of thermal expansion material region (619, 719) on the hot side (613 , 713) and at least one material region (621, 723) produced from a material having a relatively high strength and / or a relatively high thermal expansion coefficient adjoins the cold side (615, 715).

4. heat shield element (501, 510, 610, 710, 910) according to claim 2 or 3, characterized in that at least one material region (521, 721) made of a material having a relatively high strength and / or relatively high thermal expansion coefficient to the peripheral sides ( 517, 717) and at least one area of material

(519, 719) is arranged from a material with relatively low strength and / or a relatively low coefficient of thermal expansion from the peripheral sides (517, 717) seen in the center of the material volume.

5. heat shield element (501, 510, 610, 710, 910) according to any one of the preceding claims, characterized in that adjacent material areas of materials with different material properties are designed such that in a zone of the transition from one material region to another material region flowing transition from the material properties of one material area to the material properties of the other material area takes place.

6. heat shield element according to one of the preceding claims, characterized by its design as a ceramic heat shield element.

7. A hot gas lining, in particular for a gas turbine combustion chamber, having a number of heat shield elements adjoining one another at their circumferential surfaces and a barrier fluid supply for supplying a barrier fluid flow blocking the expansion gaps against the entry of hot medium into the expansion gaps, characterized in that the heat shield elements ( 501, 510, 610, 710, 910) according to one of claims 1 to 6 are configured.

8. combustion chamber, in particular gas turbine combustor, with a hot gas lining according to claim 7.

9. A method for producing a ceramic heat shield element (501, 510, 610, 710, 910), in particular a heat shield element according to claim 6, wherein a pressing or casting of a base material mixture (819, 821) and then sintering the pressed or cast base material mixture (819, 821), characterized in that prior to sintering the pressed or cast base material mixture (819, 821) adjusting at least the strength and / or the thermal expansion coefficients of different material areas.

10. The method according to claim 9, characterized in that the adjusting of the material properties of different material areas is carried out by using basic material mixtures (819, 821) with different compositions when pressing or casting for the corresponding material areas.

11. The method according to claim 10, characterized in that when pressing or casting of adjacent material areas, the composition of the base material mixture (819, 821) is changed over from one to the other composition flowing.

12. The method according to any one of claims 9 to 11, characterized in that the adjustment of the material properties takes place by after pressing or casting of the base material mixture (919) and before sintering a post-treatment of at least one material region (921), which after sintering The remainder of the basic material mixture (919) is said to have altered material properties.

13. The method according to claim 12, characterized in that the post-treatment is carried out by the at least one nachzubehandelnde material region (921) is impregnated with a liquid.

14. A mold for producing a ceramic heat shield element (501, 510, 610, 710, 910) having a mold shell which has a number of mold surfaces (2, 4, 6, 8, 10, 15, 17) and a pouring opening for pouring a ceramic material. as comprises, characterized in that the mold shell is designed as a one-piece mold shell during casting and the pouring opening is formed as an opening in one of the mold surfaces (15, 17).

15. A mold according to claim 14, characterized in that molding surfaces (2, 4) for forming a large-area first surface (102) and a large-area second surface (104) and forming surfaces (6, 8, 10, 15, 17) in the mold shell for forming small area peripheral surfaces (106, 108) extending from the first surface (102) to the second surface (104) as compared to the first and second surfaces, the pouring orifice in the forming surface (15, 17) Forming one of the peripheral surfaces (106) is formed.

16. A mold according to claim 14 or 15, characterized in that the mold shell of a plurality of individual parts (1, 3, 5, 7, 9, 11, 13), which for the Eingießprozess for forming the one-piece mold shell firmly and in particular releasably to each other connect.

17. A mold according to any one of claims 14 to 16, characterized in that at least one separating element (24, 34) is provided, with the different areas can be separated from each other in the interior of the mold shell and which is formed and arranged in the mold shell that it can be removed again from the interior of the mold shell before curing of the cast ceramic material without the mold shell to open.

18. A mold according to claim 17, characterized in that the at least one separating element (24, 34) is designed as a slot for insertion into the mold shell through the pouring opening.

A mold according to claim 18, characterized in that there is an insert (34) which projects the interior of the mold shell into a first region facing the molding surface for molding the large-area first surface (102) and one of the molding surface for molding the large-area second surface (104) facing the second region separates.

A mold according to claim 18, characterized in that there are two trays (24) separating the interior of the tray into a central area and two areas facing opposite mold surfaces for forming peripheral surfaces (108).

21. A mold according to any one of claims 14 to 20, characterized in that at least one to be introduced into the interior of the mold shell holding element is provided, which is designed and arranged in the mold shell, that it can fix a body in the interior of the mold shell and that it still can be removed from the interior of the shell mold again before curing of the cast ceramic material without opening the shell mold.

22. A mold according to claim 21, characterized in that holding elements (40) are provided as holding elements, which can be extended from the exterior of the mold shell into the interior of the mold shell and extended.

23. A mold according to claim 22, characterized in that the retaining pins (40) in the mold surface (2) for forming a large-area first surface (102) and / or in the mold surface (4) for forming the large-area second surface (104) are.

24. The method according to any one of claims 9 to 11 for producing a ceramic heat shield element (100) according to one of claims 1 to 6 using a casting process, characterized in that for casting a mold according to one of claims 14 to 23 is used.