Abstract:
An inventive hot gas seal for sealing an opening, e.g. a gap or hole, in a heat shield element or between heat shield elements of a heat shield or a liner comprises at least one resilient portion for providing a force which is designed such that the hot gas seal can be held in said opening by said force and/or that the sealing efficiency of the hot gas seal is increased by said force. Thus, further means for holding the seal in place and/or for increasing the sealing efficiency are not necessary. The invention is particularly useful if the design of said resilient portion is such that the force provides a holding action and increases the sealing efficiency, at the same time.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a hot gas seal and a hot gas seal assembly.  
       BACKGROUND OF THE INVENTION  
       [0002]     Walls of high temperature gas reactors, e.g. the walls of turbine combustion chambers, need to be shielded by a suitable thermal shielding against attack of the hot gas. The thermal shielding can be achieved by providing a hot gas resistant liner, which usually comprises a number of shield elements covering a wall to be shielded. The heat shield elements can e.g. be implemented in form of ceramic heat shield elements (CHS elements) or in form of suitable metallic heat shield elements. To allow for thermal expansion when being exposed to the hot gas, the heat shield elements are arranged such that gaps are left between neighboring heat shield elements. In order to prevent hot gas from passing through these gaps from the hot gas side of a heat shield, e.g. to a carrier structure to which the heat shield elements are fixed, gaps would need purging with air to avoid overheating. This air is costly leakage.  
         [0003]     In EP 1 302 723 A1 it is proposed to seal gaps between heat shield elements with sealing elements to prevent hot gas from passing the gaps.  
       SUMMARY OF THE INVENTION  
       [0004]     It is an object of the present invention to provide an improved hot gas seal.  
         [0005]     It is a further object of the present invention to provide an improved hot gas seal assembly.  
         [0006]     The first object is solved by a hot gas seal as claimed in claim  1 , the second object is solved by a hot gas seal assembly as claimed in claim  28 .  
         [0007]     An inventive hot gas seal for sealing an opening, e.g. a gap or hole, in a heat shield element or between heat shield elements of a heat shield or a liner comprises at least one resilient portion for providing a force which is designed such that the hot gas seal can be held in said opening by said force and/or that the sealing efficiency of the hot gas seal is increased by said force. Thus, further means for holding the seal in place and/or for increasing the sealing efficiency are not necessary. The invention is particularly useful if the design of said resilient portion is such that the force provides a holding action and increases the sealing efficiency, at the same time.  
         [0008]     In a first embodiment of the inventive hot gas seal, the at least one resilient portion may form a leg portion of a clamp. Preferably, two resilient portions are provided, each forming a leg portion of a clamp.  
         [0009]     In a second embodiment of the inventive hot gas seal, at least two leg portions are provided which are linked by a resilient bracket portion which forms said at least one resilient portion for providing said force. The leg portions do therefore not necessarily need to be resilient themselves. In a further development of this embodiment, the resilient bracket portion is pre-tensioned for providing said force. The pre-tension may be chosen such that the leg portions tend to open or, alternatively, such that the leg portions tend to close. The pretension can be used to assure a secure fixing of the hot gas seal to a liner and/or to provide a tight sealing by pressing the leg portions against a wall of a liner.  
         [0010]     In a third embodiment, a metallic sealing plate comprising at least one corrugated portion is provided. The at least one corrugated portion forms said at least one resilient portion for providing said force.  
         [0011]     In a fourth embodiment, the hot gas seal comprises at least one spring like portion which forms said at least one resilient portion for providing said force. By setting the spring parameters of the spring like portion, it is possible to adjust the force provided by the spring like portion.  
         [0012]     In a fifth embodiment, the hot gas seal comprises a tubular sealing body which comprises a resilient core which forms said at least one resilient portion for providing said force. The resilient core may comprise a spring element which may, e.g., have a spiral shaped cross section, a cross section which has the shape of an elliptical spiral, or an omega shaped cross section. As an alternative to forming the resilient core by a spring element, it is possible to provide at least one gas tight and gas filled space inside of the tubular sealing body. The gas filled space forms the resilient core of the tubular sealing body, i.e. the sealing body acts similar to a gas spring. The spring force provided by the gas depends on the gas temperature and the gas pressure inside the gas tight space at a reference temperature. By suitably setting the gas pressure at the reference temperature, the resilient properties of the seal may be set.  
         [0013]     In a sixth embodiment, the hot gas seal comprises a flexible rolled sheet which forms said at least one resilient portion for providing said force. The flexible rolled sheet may have a sandwich structure comprising a soft, compliant or flexible surface on a flexible material. In a further development of the fifth embodiment, the cross section of said flexible rolled sheet may resemble the shape of an elliptical spiral.  
         [0014]     In a seventh embodiment, the hot gas seal comprises a body and a number of resilient extensions extending from the body. In the seventh embodiment, the extensions form said at least one resilient portion for providing said force. The body may have a planar shape. The extensions then protrude from at least one side of the planar shaped body. As an alternative, the body may have a circular or elliptical cross section. The extensions then protrude radially from the body. The extensions may e.g. have a bristle like shape, a wedge like shape, a coil like shape, or a serpentine like shape. Preferably, the body and/or the extensions are surrounded by a cloth seal.  
         [0015]     In the inventive hot gas seal, said at least one resilient portion is preferably pre-tensioned for providing said force.  
         [0016]     An inventive hot gas seal assembly for sealing an opening, e.g. a gap or a hole, in a heat shield element or between heat shield elements of a heat shield or liner against a hot gas, comprises a sealing body and at least one further sealing element which is in a solid state at room temperature and in a high viscosity liquid state at the temperature of the hot gas. During installation of the hot gas seal assembly, the further sealing element is solid. During operation of the heat shielded structure, i.e. when hot gas is present, the further sealing element melts, and the inventive sealing assembly provides a tight seal of the opening.  
         [0017]     Further features, properties, and advantages of the present invention are described hereinafter with reference to the accompanying drawings, by means of detailed embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  shows a first example of a first embodiment of the inventive hot gas seal.  
         [0019]      FIG. 2  shows a second example of the first embodiment of the inventive hot gas seal.  
         [0020]      FIG. 3  shows a third example of the first embodiment of the inventive hot gas seal.  
         [0021]      FIG. 4  shows a fourth example of the first embodiment of the inventive hot gas seal.  
         [0022]      FIG. 5  shows a first example of a second embodiment of the inventive hot gas seal.  
         [0023]      FIG. 6  shows a second example of the second embodiment of the inventive hot gas seal.  
         [0024]      FIG. 7  shows a third example of the second embodiment of the inventive hot gas seal.  
         [0025]      FIG. 8  shows an example of a third embodiment of the inventive hot gas seal.  
         [0026]      FIG. 9  shows an example of a fourth embodiment of the inventive hot gas seal.  
         [0027]      FIG. 10  shows a first example of a fifth embodiment of the inventive hot gas seal.  
         [0028]      FIG. 11  shows a second example of the fifth embodiment of the inventive hot gas seal.  
         [0029]      FIG. 12  shows an example of a usage of a hot gas seal according to the fifth embodiment.  
         [0030]      FIG. 13  shows a third example of the fifth embodiment of the inventive hot gas seal.  
         [0031]      FIG. 14  shows a first example of a sixth embodiment of the inventive hot gas seal.  
         [0032]      FIG. 15  shows a second example of the sixth embodiment of the inventive hot gas seal.  
         [0033]      FIG. 16  shows a third example of the sixth embodiment of the inventive hot gas seal.  
         [0034]      FIG. 17  shows a first example of a seventh embodiment of the inventive hot gas seal.  
         [0035]      FIG. 18  shows a second example of the seventh embodiment of the inventive hot gas seal.  
         [0036]      FIG. 19  shows a third example of the seventh embodiment of the inventive hot gas seal.  
         [0037]      FIG. 20  shows a fourth example of the seventh embodiment of the inventive hot gas seal.  
         [0038]      FIG. 21  shows a fifth example of the seventh embodiment of the inventive hot gas seal.  
         [0039]      FIG. 22  shows an embodiment of the inventive hot gas seal assembly. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0040]     A first embodiment of the present hot gas seal will now be described with reference to  FIGS. 1-4 . The first example of the first embodiment of the inventive hot gas seal is shown in  FIG. 1 . The figure shows a first heat shield element  1 , a second heat shield element  3 , and a hot gas seal  5 . Each heat shield element  1 ,  3  comprises a projection  2 ,  4  which projects towards the respective other heat shield element  1 ,  3 . The heat shield elements  1 ,  3  are arranged such that the projections  2 ,  4  are located adjacent to each other. The first heat shield element  1  further comprises a wall portion  6  which forms, together with the respective projection  2 , a space for accommodating therein the hot gas seal  5 , and for receiving the projection  4  of the second heat shield element  3 . When the hot gas seal  5  is accommodated in the opening, a resilient leg portion  7  is clamped between the projection  4  of the second heat shield element  3  and the wall portion  6  of the first heat shield element  1 . Thus, the leg portion  7  exerts, by means of a spring force, a pressure to the projection  4  which presses this projection  4  onto the projection  2  of the first heat shield element  1 .  
         [0041]     A second example of the first embodiment is shown in  FIG. 2 . Like  FIG. 1 ,  FIG. 2  shows a first heat shield element  11 , a second heat shield element  13 , and a hot gas shield  15 . The first heat shield element  11  and the second heat shield element  13  are arranged such that a gap  12  is left between them. The hot gas seal  15  comprises two leg portions  17 ,  18  and a sealing portion  19  linking both leg portions  17 ,  18 . The leg portions  17 ,  18  are resilient and provide a spring force urging the leg portions  17 ,  18  towards the heat shield elements  11 ,  13 . By said spring force, the hot gas seal  15  is held in place to seal the gap  12 . The sealing portion  19  can be shielded against the hot gas by an additional shield element  16  arranged between the sealing portion  19  and the end faces  11   a ,  13   a  of the shield elements  11 ,  13  such that the sealing portion  19  and the leg portions  17 ,  18  are protected against the hot gas. The hot gas seal  15 , in particular the sealing portion  19  of the hot gas seal  15 , may be fixed, e.g. screwed, to a carrier structure  14  carrying the heat shield elements  11 ,  13 . In this example, the hot gas seal  15  is located completely under the heat shield elements  11 ,  13  so that it is well protected against the hot gas.  
         [0042]     A third example of the first embodiment is shown in  FIG. 3 . The hot gas seal  25  of  FIG. 3  is very similar to the hot gas seal  15  shown in  FIG. 2 . It comprises a first resilient leg portion  27 , a second resilient leg portion  28 , and a sealing portion  29  linking both leg portions  27 ,  28 . Like the hot gas seal  15  in  FIG. 2 , the hot gas seal  25  seals a gap  22  between two heat shield elements  21 ,  23 . Across the hot gas seal  25 , a pressure gradient is build up to increase the sealing pressure pressing each leg portion  27 ,  28  against the respective heat shield element  21 ,  23 . To achieve this, the pressure p acting on the leg portions  27 ,  28  for pressing them towards the heat shield elements  21 ,  23  is set to be higher than the pressure p 0  of the hot gas the gap  22  between the heat shield elements  21 ,  23 .  
         [0043]     A fourth example of the first embodiment of the inventive hot gas seal is shown in  FIG. 4 . The hot gas seal  30  comprises a first holding portion  35  and a second holding portion  36 . The holding portions  35 ,  36  are linked by a sealing portion  39 . The sealing portion  39  forms a loop projecting into a gap  32  between two heat shield elements  31 ,  33 . The section of the sealing portion  39  which projects furthest into gap  32  is surrounded by a shielding material  34  to provide a shielding from the high temperatures of the hot gas. Suitable shielding materials are ceramic materials or metallic materials, e.g. ceramic or metallic cloths.  
         [0044]     The holding portions  35 ,  36  each comprise a leg portion  37   a ,  38   a , which can be used together with central sections  37   b ,  38   b  of the hot gas sealing portion  39  to clamp the hot gas seal  35  to the heat shield elements  31 ,  33 . The sealing is provided by a pre-tension of the hot gas seal, e.g. by a pre-tension of the leg sections  37   a ,  37   b  and/or the central sections  38   a ,  38   b.    
         [0045]     The first sample of the second embodiment is shown in  FIG. 5 . The Figure shows a first heat shield element  41  and a second heat shield element  43  between which a gap  42  is formed. The gap  42  is sealed by a hot gas seal  45  which comprises a first leg portion  47  and a second leg portion  48 . Both leg portions  47 ,  48  are linked by a resilient bracket portion  46  which is pre-tensioned such that the leg portions  47 ,  48  tend to open. When being inserted into the gap  42 , therefore, the legs  47 ,  48  are urged against the walls of the heat shield elements  41 ,  43  for providing the sealing action. In order to secure the hot gas seal  45  against loss, the leg portion  47  is longer than the leg portion  48  and comprises a holding section  49  by which it is fixed in a recess  44  of a carrier structure  40  for carrying the heat shield elements  41 ,  43 .  
         [0046]     A second example of the hot gas seal according to the second embodiment is shown in  FIG. 6 . Like the seal  45  in  FIG. 5 , the seal  55  in  FIG. 6  is arranged in a gap  52  between two heat shield elements  51 ,  53 . The hot gas seal  55  comprises a first leg portion  57  and a second leg portion  58 , which are linked by a pre-tensioned bracket portion  56 . The pre-tension, like in the example shown in  FIG. 5 , is such that the legs  57 ,  58  tend to open. The sealing action is provided by the spring force which is exerted by the bracket portion  56  and transmitted to the surfaces of the heat shield elements  51 ,  53  through the leg portions  57 ,  58 . Further, the hot gas seal  55  comprises a fixing section  59 , which allows the hot gas seal  55  to be fixed e.g. screwed, to carrier structure  50  for carrying the heat shield elements  51 ,  53 .  
         [0047]     A third example of the second embodiment is shown in  FIG. 7 . In  FIG. 7 , a first heat shield element  71 , a second heat shield element  73 , and a third heat shield element  74  are shown. In a gap  72  between the first heat shield element  71  and the second heat shield element  73 , a hot gas seal  75  is disposed. The hot gas seal  75  according to the third example of the second embodiment comprises two parts, a holding part  76  and a shielding part  77 . In  FIG. 7 , both parts are shown in cross section. They extend through a major part of the gap  72  in a direction perpendicular to the cross section.  
         [0048]     The shielding part  77  of the hot gas seal  75  is made of a bent metal sheet which is bent such that the center section  77   a  of the metal sheet forms a closed loop in cross section and that the peripheral sections  77   b ,  77   c  of the metal sheet are folded back onto each other. The folded back peripheral sections  77   b ,  77   c  are fixed to a rod  78  which extends through a major part of the gap  72  in a direction perpendicular to the cross section.  
         [0049]     The holding part  76  of the hot gas seal is also made of a bent metal sheet. The metal sheet is bent such that the central section  76   a  of it forms a loop and that its peripheral sections  76   b ,  76   c  are substantially parallel to each other with leaving a gap there between. The central section  76   a  of the holding part  76  is pre-tensioned such that the peripheral sections  76   b ,  76   c  tend to open.  
         [0050]     When the hot gas seal  75  is placed in the gap  72  between the heat shield elements  72  and  73 , the peripheral sections  77   b ,  77   c  of the shielding part  77  are inserted into the holding part  76  such that the rod  78  extends through the tubular space formed by the central section  76   a  of the holding part  76 . Then, the holding part  76  is inserted into the gap  72  while pressing the peripheral sections  76   b ,  76   c  against the pre-tension together, thereby fixing the shielding part  77  in the holding part  76 . After being inserted into the gap  72 , an opening movement of the peripheral sections  7   ab ,  76   c  of the holding part  76  due to the pre-tension is restricted by the heat shield elements  71 ,  73 . Therefore, the spring force provided by the central section  76   a  of the holding part  76  provides for a tight sealing of the gap  72 . In the example shown in  FIG. 7 , a ceramic or metallic hot gas part  79  that provides shielding from the high temperatures of the hot gas is provided around the central section  77   a  of the shielding part  77 .  
         [0051]     An example of the third embodiment is shown in  FIG. 8 . The heat shield elements  61 ,  63  shown in  FIG. 8  comprise front surfaces  64 ,  66  which face each other. Between the front surfaces  64 ,  66  a gap  62  is formed. Further, recesses  67 ,  68  are formed in each front surface  64 ,  66 . The hot gas seal  65  has a plate like shape which, in  FIG. 8 , is shown in cross-section. Its center section  65   a  is corrugated, while its outer sections  65   b ,  65   c  are substantially flat. When being disposed in the gap  62  between the heat shield elements  61 ,  63 , the outer sections  65   b ,  65   c  are placed in the recesses  67 ,  68 . The corrugated center section  65   a  then urges the outer sections  65   b ,  65   c  away from each other. Thus, it presses the outer sections  65   b ,  65   c  into the recesses  67 ,  68  and, as a consequence, provides a holding and sealing action.  
         [0052]     An example of the fourth embodiment of the inventive hot gas seal is shown in  FIG. 9 . The figure shows a heat shield element  81  and a carrier structure  83  in which a notch  82  is formed. Between a bottom section  84  and an opening of the notch  82 , a narrow section  86  of the notch  82  is formed. A hot gas seal  85  is provided in the notch. The hot gas seal  85  comprises a plate like portion  85   a  which extends through the bottom section  84  of the notch  82 , a sheet like portion  85   b  which protrudes from the notch  82  in the direction of the heat shield element  81 , and a spring like portion  85   c  linking the plate like portion  85   a  and the sheet like portion  85   b.    
         [0053]     The spring like portion  85   c  is made from a spring loaded metal. It allows for thermal movement of the heat shield element  81  while still maintaining the sealing. Although the spring like portion  85   c  is, in the example shown in  FIG. 9 , formed integrally with the hot gas seal  85  it may as well be a separate part.  
         [0054]     The plate like portion  85   a  of the hot gas seal  85  is captured in the bottom part  84  of the notch  82 , thus holding the hot gas seal  85  in place. This way of holding the hot gas seal  85  in place provides the advantage of increased serviceability.  
         [0055]     A first example of the fifth embodiment of the inventive hot gas seal is shown in  FIG. 10 . The hot gas seal  90  is made from a tubular cloth  92  which increases the sealing efficiency by providing a soft, compliant or flexible surface which can be pressed against e.g. walls of heat shield elements. The cloth  92  may be made from a suitable ceramic, metallic, or other material which can be exposed to the hot gas. Inside of tubular cloth  92 , an omega shaped spring  94  is arranged which provides a spring force for pressing the outer surface of the tubular cloth  92  e.g. towards the walls of heat shield elements. The omega-shaped spring  94  is preferably made of metal. As an alternative, an E-shaped spring may be used instead of the omega shaped spring, as well.  
         [0056]     A second example of the fifth embodiment is shown in  FIG. 11 . Like in the first example, the hot gas seal  100  comprises a tubular cloth  102 . In the present example, the interior of the tubular cloth  102  forms a gas tight and gas filled interior space  104 . The gas tight sealing of the interior space  104  of the tubular cloth  102  may be provided by a suitable coating of its inner wall. When the hot gas seal  100  is exposed to the hot gas, the gas inside the gas tight interior space  104  heats up and, as a consequence, expands, and thereby increases the force by which the soft, compliant or flexible surface is pressed against e.g. the walls of heat shield elements. As an alternative, the interior space may as well be filled with a liquid or a solid that either expands or evaporates and increases the force by which the soft, compliant or flexible surface is pressed against e.g. the walls of heat shield elements.  
         [0057]     An example of the use of a hot gas seal  90 , as shown in  FIG. 10 , or a hot gas seal  100 , as shown in  FIG. 11 , is shown in  FIG. 12 .  FIG. 12  shows a first heat shield element  111  and a second heat shield element  113 , which are arranged such that a gap  112  is left there between. In the heat shield elements  111 ,  113 , recesses  117 ,  119  are formed. A hot gas seal  90 , as shown in  FIG. 10 , or a hot gas seal  100 , as shown in  FIG. 11 , is disposed in each recess  117 ,  119 . In addition, a sealing plate  114  is present, which is partly disposed in the first recess  117  and partly disposed in the second recess  119 . The sealing plate  114  is pressed against the upper walls  115 ,  116  of the recesses  117 ,  119  by the hot gas seals  90 , thus providing good sealing.  
         [0058]     A third example of the fifth embodiment is shown in  FIG. 13 . In the present example, the cross section of the hot gas seal  120  resembles a half circle with a flat side  124  and an arcuate side  126 . The flat side  124  is pressed against a carrier structure  125  carrying heat shield elements  121 ,  123  of a heat shield. Inside the hot gas seal  120 , either a spring, as in the first example of the fifth embodiment, or a gas filing, as in the second example of the fifth embodiment, may be provided.  
         [0059]     A first example of the sixth embodiment of the inventive hot gas seal is shown in  FIG. 14 . The hot gas seal  130  is made from a metal sheet  132  which is rolled up so as to have a spiral cross section. The spiral cross section provides a spring force for providing holding and sealing. The rolled metal sheet  132  may be surrounded by tubular cloth made from metal or ceramics.  
         [0060]     A second example of the sixth embodiment is shown in  FIG. 15 . The hot gas seal  140  shown in  FIG. 15  is made, like the hot gas seal  130  shown in  FIG. 14 , from a rolled metal sheet  142  so as to have a spiral cross section. However, the rolled metal sheet  142  is laminated with a soft, compliant or flexible surface  144  made from e.g. TBC, metallic cloth or ceramic cloth. The soft, compliant or flexible surface  144  provides for a better sealing when contacting e.g. the walls of heat shield elements.  
         [0061]     A third example of the sixth embodiment is shown in  FIG. 16 . In this example, the spiral cross section of the rolled metal sheet  152  forming the hot gas seal  150  has an elliptic shape to optimize the direction in which the force provided by the rolled up metal sheet  152  is acting.  
         [0062]     A first example of the seventh embodiment of the inventive hot gas seal is shown in  FIG. 17 . The Fig. shows a first heat shield element  161  and a second heat shield element  163 . The heat shield elements  161 ,  163  are fixed to a carrier structure  164  such that a gap  162  is left between them. Between the carrier structure  164  and the heat shield elements  161 ,  163  hot gas seals  165 ,  166  are arranged. The seals  165 ,  166  each comprise a metal plate  165   a ,  166   a  which is fixed to the carrier structure  164 . Spring loaded metal strips  165   b ,  166   b  extend from each metal plate  165   a ,  166   a  which is oriented such that the metal strips  165   b ,  166   b  project towards the heat shield elements  161 ,  163 . Due to the spring load, the metal strips  165   b ,  166   b  are pressed against the lower surfaces  167 ,  168  of the heat shield elements  161 ,  163 , thereby providing the sealing. A hot gas seal as described with reference the  FIG. 17  can have a long sealing length. Further, compared to brush seals, no flow between individual metal strips occurs.  
         [0063]     A second example of the seventh embodiment of the inventive hot gas seal is shown in  FIG. 18 . The seal  190  shown in  FIG. 18  is a so-called brush seal. The brush seal  190  is rope shaped and has a center core  191  which provides support for sealing bristles  193  extending radially from the core  191 .  
         [0064]     Instead of sealing bristles  193 , flexible sealing wedges  194 , as in the brush seal  191   a  shown in  FIG. 19 , flexible sealing serpentines  195 , as in the brush seal  191   b  shown in  FIG. 20 , or flexible sealing coils  196 , as in the brush seal  191   c  shown in  FIG. 21 , may be provided.  
         [0065]     An embodiment of the inventive hot gas seal assembly is shown in  FIG. 22 . The figure shows a first heat shield element  201  and a second heat shield element  203  which are arranged such that a gap  202  is left between them. In front surfaces  204   205  of the heat shield elements  201 ,  203 , recesses  206 ,  207  are formed. In the gap  202 , a seal  208 , which may by e.g. a ceramic seal, a metallic seal, or a cloth seal, is disposed. The seal  208  extends partly into each recess  206 ,  207 . In the inventive sealing assembly, the recesses  206 ,  207  are partly filled with a solid material  209  which has a melting point lower than the temperature of the hot gas. During installation of the hot gas seal assembly, the solid material  209  is disposed in the recesses  206 ,  207 . When, during operation, the solid material  209  is exposed to the hot gas, it melts and forms a closed join with the seal  208  due to its high viscosity. The melted solid  209  then provides, together with the seal  208 , an excellent sealing.