Abstract:
An insulation system for shafts through which hot gases flow, especially exhaust gas shafts of gas turbines has an insulation layer ( 20, 40 ) as well as a flat cover ( 26, 39 ), which holds the insulation layer ( 20, 40 ) and covers it against the gas flow. The cover ( 26, 39 ) is guided by bearing rails ( 21, 41 ). In such an insulation system, the number of spacers ( 22, 23, 24; 47, 48, 49 ) by which the bearing rails ( 21, 41 ) are fastened to a shaft wall ( 25, 50 ) shall be minimized. Furthermore, the insulation system shall be able to be manufactured with a high degree of prefabrication in the workshop and with low assembly effort at the construction site. The bearing rails ( 21, 41 ) are fastened to the shaft wall ( 25, 50 ) with a fixed mount ( 31, 51 ) and at least one movable mount ( 32, 52 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention pertains to an insulation system for shafts through which hot gases flow, especially exhaust gas shafts of gas turbines with an insulation layer as well as a flat cover, which holds the insulation layer and covers it against the gas flow, wherein the cover is guided by bearing rails.  
         BACKGROUND OF THE INVENTION  
         [0002]    Such insulation systems are used in the diffusor and flue area of gas turbines. The insulation systems are exposed to gases with high temperatures above 400° C. in these areas. In addition, there is a high velocity of flow above 30 m/sec in the diffusor area of the gas turbine. As a result, high thermal and dynamic stresses occur on the insulation system, especially on its holding systems, the cover, the bearing rails, fastening bars (spacers) for fastening the bearing rail on a wall of the shaft, etc.  
           [0003]    The cover, the bearing rails and other fastening parts of the insulation system are usually made of a temperature-resistant metal with respect to the temperatures occurring. This also applies to the spacers, by which the bearing rails are fastened to the shaft wall. Thus, the spacers form heat bridges, through which the heat can be transported from the exhaust gas flow of the gas turbine into the shaft wall, because spacers made of metal are good heat conductors. It is therefore important to use as few spacers as possible. This goal is achieved, in principle, already by the use of bearing rails to which the cover for holding the insulation layer is fastened. The bearing rails have sufficient inherent stiffness to securely hold the cover. At the same time, the bearing rails and the cover must have a sufficient possibility of movement while still ensuring a secure hold in order to compensate even great temperature variations by thermal expansion and dynamic stresses.  
           [0004]    In insulation systems of this type which are known from practice, this is guaranteed by the bearing rails being connected to the spacers with a certain clearance when viewed in the longitudinal direction of the bearing rails. Moreover, it is known that spacers can be made of a flat steel, in which case the flat steel is arranged in a plane extending transversally at right angles to the longitudinal axis of the bearing rails. Axial expansions in the bearing rail can thus be compensated by the bending of the flat steel. However, considerable stresses, especially bending stresses on the spacers, still continue to occur in these systems, so that a large number of spacers still continues to be necessary. In addition, the prior-art systems have the drawback that a considerable manufacturing effort is associated with them but the degree of prefabrication is low. The prior-art systems must be assembled almost exclusively at the construction site.  
         SUMMARY AND OBJECTS OF THE INVENTION  
         [0005]    Based on this, the primary object of the present invention is to improve an insulation system of the type mentioned in the introduction such that the number of spacers by which the bearing rails are fastened to the shaft wall is minimized and they can be manufactured in the workshop with a high degree of prefabrication with low assembly effort at the construction site.  
           [0006]    To accomplish this object, the insulation system according to the present invention is characterized in that the bearing rails are fastened to the shaft wall with a fixed mount and at least one movable mount.  
           [0007]    The bearing rail is fixed by the insulation system according to the present invention in at least one point, while it is freely movable in its longitudinal direction in the other fastening points designed as movable mounts. Each bearing rail is thus mounted in a statically defined manner at each temperature and consequently at each amount of thermal expansion. Bending stresses acting on the spacers cannot occur, so that it is possible to work with a minimum of spacers. Depending on the length of the bearing rails, even one fixed mount and one movable mount are sufficient. These can be prefabricated almost completely in the workshop and then be assembled completely at the construction site.  
           [0008]    It is particularly favorable for the bearing rail to be fastened to the shaft wall with an approximately central fixed mount and two outer movable mounts. The bearing rail is fixed approximately in the middle and can expand freely as a consequence of thermal expansion in both directions. It is, of course, also possible to provide a plurality of movable mounts on both sides in the case of longer bearing rails.  
           [0009]    According to a variant of the present invention, the cover is connected to the bearing rails in a non-positive manner, especially by means of clamping strips. The cover is thus also able to expand freely during temperature variations without unacceptable thermal stresses building up. It is particularly favorable for the cover itself to be connected to the bearing rail in a positive-locking manner in the area of the fixed mounts of the bearing rails. According to one design embodiment of the present invention, this is accomplished by providing a notch in the bearing rail in the area of the fixed mount, which notch is engaged by a projection on the cover in a positive-locking manner.  
           [0010]    Further features of the present invention pertain to design details of the movable mount and to the fastening of the cover to the bearing rails.  
           [0011]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    In the drawings:  
         [0013]    [0013]FIG. 1 is a perspective top view of an exemplary embodiment of an insulation system with the features of the present invention;  
         [0014]    [0014]FIG. 2 is a vertical sectional view through the insulation system according to FIG. 1 in plane II-II;  
         [0015]    [0015]FIG. 3 is a vertical sectional view through the insulation system according to FIG. 1 in plane III-III;  
         [0016]    [0016]FIG. 4 is a perspective view of a fixed mount area of the insulation system according to FIG. 1 in the partially assembled state;  
         [0017]    [0017]FIG. 5 is a perspective view of a movable mount area of the insulation system according to FIG. 1 in a partially assembled state;  
         [0018]    [0018]FIG. 5 a  is a perspective view of the movable mount area of the insulation system according to FIG. 1 in a variant of FIG. 5;  
         [0019]    [0019]FIG. 6 is a perspective top view of another exemplary embodiment of an insulation system with the features of the present invention;  
         [0020]    [0020]FIG. 7 is a vertical sectional view through the insulation system according to FIG. 6 in a plane VII-VII;  
         [0021]    [0021]FIG. 8 is a vertical sectional view through the insulation system according to FIG. 6 in a plane VIII-VIII;  
         [0022]    [0022]FIG. 9 is a perspective view of a fixed mount area of the insulation system according to FIG. 6 in a partially assembled state;  
         [0023]    [0023]FIG. 10 is a perspective view of a movable mount area of the insulation system according to FIG. 6 in a partially assembled state;  
         [0024]    [0024]FIG. 11 is a side view of another variant of the movable mount area and of the fixed mount area of the insulation system according to FIG. 1;  
         [0025]    [0025]FIG. 12 is a horizontal sectional view through the movable mount area according to FIG. 11; and  
         [0026]    [0026]FIG. 13 is a horizontal sectional view through the fixed mount area according to FIG. 11. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    Referring to the drawings in particular, the exemplary embodiments of an insulation system shown in FIGS. 1 through 10 are used mainly in exhaust gas shafts for gas turbines. The exemplary embodiment of the insulation system shown in FIGS. 1 through 5 is used especially in the range of higher pressures and pressure variations of such an exhaust gas shaft and because of the high flow velocities of the exhaust gas above 30 m/sec which occur here, while the exemplary embodiment shown in FIGS. 6 through 10 is used preferably in the area of the flue.  
         [0028]    [0028]FIGS. 1 and 6 show a “web” of an insulation system. The complete insulation system always comprises a plurality of webs arranged in front of and next to one another.  
         [0029]    [0029]FIG. 1 shows a detail, namely, a “web” of an insulation system in which the insulation layer  20  proper (see FIGS. 2 and 3) is omitted for reasons of greater clarity. The bearing rails  21  are fastened in this case via three spacers  22 ,  23  and  24  to a shaft wall  25 .  
         [0030]    An essentially flat, but optionally curved cover  26  is used to hold and cover the insulation  20 . The cover  26  lies with its longitudinal side edges on two adjacent bearing rails  21  and is held by four clamping strips  27 . The cover  26  is held by this structure “floatingly” between the bearing rail  21  and the clamping strip  27 . This means that the cover  26  can move freely in relation to the bearing rails  21  as a consequence of thermal expansions, so that no stress leading to warping of the cover  26  or at least no appreciable stresses can occur within the cover  26 . The bearing rail  21  has a U-shaped cross section with an upwardly open U for this purpose. The covers  26  lie on the free legs of the U-shaped bearing rail  21 , so that a linear contact with minimal frictional force is obtained between the covers  26  and the bearing rail  21 .  
         [0031]    The clamping strips  27  may shift, optionally with the covers  26 , in relation to the bearing rails as a consequence of the thermal expansion of the covers, but also to compensate their own thermal expansion. This is accomplished as follows:  
         [0032]    Stay bolts  28  are welded to the U-shaped bearing rail  21 . The stay bolts  28  are passed through between two adjacent covers  26 . The distance between the two adjacent covers  26  and the distance between the covers  26  and the stay bolt  28  is selected to be such that the covers  26  can expand freely in the temperature range to be expected. This distance can be calculated using the coefficient of thermal expansion of the material for the covers  26  or be determined experimentally. The stay bolt  28  is then passed through a hole in the clamping strip  27  placed on the two adjacent covers  26 . One of the holes in the clamping strip  27  corresponds to the diameter of the stay bolt  28 , while the other holes in the clamping strip  27  are so large that they permit a free thermal expansion of the clamping strip  27  without unacceptable stresses leading to warping in the clamping strip  27  building up. Instead of a round hole, it is, of course, also possible to provide elongated holes of a sufficient length in the clamping strip  27 . However, it is less expensive for manufacturing technical reasons to punch or drill simple round holes. The diameter of the holes in the clamping strip  27  is again calculated corresponding to the coefficient of thermal expansion of the material of the clamping strip  27  or is determined experimentally. The holes in the clamping strip  27  are then covered with washer  29 , which are square in this case, and the clamping strip  27  is screwed together with the washer  29  and the covers  26  by means of a nut  30 , which is, e.g., a self-locking nut.  
         [0033]    In the area of the spacer  23 , the spacer  23  is connected to the bearing rail  21 , on the one hand, and the bearing rail  21  is connected to the cover  26 , on the other hand, such that the cover  26  is mounted as a fixed mount  31  when viewed in the longitudinal direction of the bearing rails  21 . In the area of the outer spacers  22 ,  24 , the bearing rail  21  is mounted in the manner of a movable mount  32 . The bearing rail  21  is thus also able to expand freely as a consequence of temperature variations without thermal stresses, or at least unacceptably high thermal stresses building up.  
         [0034]    The fixed mount  31  is designed as shown in FIGS. 2 and 4.  
         [0035]    The spacer  23  is fixedly connected, namely, welded, to the shaft wall  25 , on the one hand, and to the bearing rail  21 , on the other hand. The bearing rail  21  is thus mounted fixedly in this area. The bearing rail  21  has notches  33  on its top side in its two free legs. A guide strap  34  is arranged, namely, welded in this case, on the underside of the cover  26  at least in the area of the longitudinal edge of the cover  26 . This guide strap  34  engages the corresponding notch  33  in a positive-locking manner. As a result, the cover  26  is mounted positively in the longitudinal direction of the bearing rail  21 , but it can move freely transversal at right angles to the longitudinal direction of the bearing rail  21 . The notches  33  are always arranged exactly above the spacer  23  forming the fixed mount  31  in this case. The fixed mount  31  is arranged exactly in the middle of the bearing rail  21  and the cover  26 , so that the absolute values of the thermal expansion will be equal at the free ends of the bearing rails  21  and the cover  26 . However, it is immediately clear that the movable mount  31  may also be arranged offset toward the center or even in the edge areas of the bearing rails  21  and of the cover  26 . The notches  33  and the spacer  23  may also be arranged offset in relation to one another.  
         [0036]    The movable mount  32  is shown in greater detail in FIGS. 3 and 5.  
         [0037]    As was mentioned above, the cover  26  lies freely on the free legs of the bearing rail  21  outside the area of the fixed mount  31  and is held only by the clamping, so that the cover  26  can expand freely in this area (floating mounting). The movable mount  32  for the bearing rail  21  is formed as follows: The spacers  22 ,  24  are again welded to the shaft wall  25 . At their opposite ends, the spacers  22 ,  24  are bent in an L-shaped pattern, so that the bent-off leg  35  of the spacers  22 ,  24  is in contact with the underside of the bearing rail  21 . Notches  36  are provided on the top side of the bearing rail  21  in the free legs of the bearing rail. This notch is engaged by an approximately rectangular ring  37 , which is led around the bearing rail  21 . A gap  38 , which is engaged by the bent-off leg  35  of the respective spacer  23  and  24  with a certain clearance, is formed between the ring  37  and the underside of the bearing rail  21 . Thus, the ring  37  can move freely together with the bearing rail  21  in the longitudinal direction of the bearing rail  21  in relation to the spacers  22 ,  24 . The ring  37  is designed such that it exactly fits the notches  36  in a positive-locking manner.  
         [0038]    Alternatives are, of course, conceivable for the movable mount  32 . For example, the spacers  22 ,  24  may be welded to the ring  37  and the notches  36  may be so long that the ring  37  can be displaced with the necessary clearance in the longitudinal direction of the bearing rail  21 . This variant is shown in FIG. 5 a.    
         [0039]    [0039]FIGS. 6 through 10 show an alternative exemplary embodiment of the present invention, which is especially suitable for parts of the exhaust gas guiding structure of a gas turbine which are not subject to very high velocities of flow, namely, the flue. The covers  39  for an insulation layer  40  are mounted on U-shaped bearing rails  41 . However, the bearing rails  41  are designed as rails with an downwardly open U-shaped cross section in this case, so that the cover  39  lies flat on two adjacent bearing rails  41  in the area of its longitudinal edges. The cover  39  is held by clamping strips  42  in a non-positive manner. Just as in the above-described exemplary embodiment, the clamping strips  42  are held by means of stay bolts  43  and a nut  44 , which is, e.g., a self-locking nut, and washers  45 . As can be clearly recognized from FIGS. 7 and 8, the longitudinal side edges of the cover  39  are again spaced so wide apart from one another and from the stay bolts  43  that the covers  39  can freely expand on the side. Unlike in the above-mentioned exemplary embodiment, all holes  46  in the clamping strips  42 , through which the stay bolts  43  are passed, are provided with a substantially larger diameter than the diameter of the stay bolts  43 , which is also indicated in FIGS. 7 and 8.  
         [0040]    The bearing rails  41  are fastened to the shaft wall  50  by spacers  47 ,  48 ,  49 . The area of the middle spacer  48  is again designed as a fixed mount  51 , while the area of the outer spacers  47 ,  49  is designed as a movable mount  52 .  
         [0041]    The fixed mount is shown in greater detail in FIGS. 7 and 9.  
         [0042]    The spacer  48  is arranged here in a plane corresponding to the longitudinal direction of the bearing rails  41  and is fixedly connected, namely, welded, to the shaft wall  50 , on the one hand, and to the bearing rail  41 , on the other hand. The cover  39  has a guide strap  53  centrally in the area of its longitudinal side edge. However, this guide strap  53  is arranged in this case on the top side, i.e., on the side of the cover  39  facing the flow. Two clamping strips  42  are associated with each bearing rail  41 . As can be clearly recognized from FIG. 9, the guide strap  53  is held between the two clamping strips  42  in a positive-locking manner. The cover  39  is thus again mounted in the manner of a fixed mount in its middle area when viewed in the longitudinal direction of the bearing rails  41 .  
         [0043]    The area of the movable mount  52  is shown in greater detail in FIGS. 8 and 10.  
         [0044]    Just as in the above-mentioned exemplary embodiment, the cover  39  lies here freely on the bearing rails  41  and is held by the clamping strip  42 , so that the cover  39  can expand freely after overcoming the frictional forces (floating mounting). The spacers  47 ,  49  are again welded to the shaft wall  50 , and the plane of the spacers  47 ,  49  extends transversely at right angles to the longitudinal direction of the bearing rails  41 . The spacers  47 ,  49  are first punched or cut out as T-shaped plates. The upper transverse leg  54  of the spacers  47 ,  49  is then bent by 90°, as can be clearly recognized from FIG. 10. The transverse leg  54  thus forms two lateral wings  56 . A slot  55  each, which are engaged by the transverse leg  54  with the wings  56 , is thus formed in the bearing rails  41  on the left and right. The spacers  47 ,  49 , rotated by 90°, are first inserted into the downwardly open U of the bearing rail  41  and then again turned back by 90° into the position shown in FIGS. 8 and 10, while the transverse legs  54  are turned into the slots  55 . The slots  55  are made so long that the bearing rail  41  can move freely on the spacers  47 ,  49  as a consequence of thermal expansion.  
         [0045]    The guide strap  53  of the cover  39  is arranged above the spacer  48  forming the fixed mount  51  in the exemplary embodiment explained last as well. The fixed mount  51  for the bearing rail  41  and the guide strap  53  may, of course, be arranged offset in relation to one another in this case as well. The fixed mount  51  does not necessarily have to be provided exactly centrally in relation to the bearing rail  41 , either. The fixed mount  51  may also be provided at the end area of the bearing rail  41 .  
         [0046]    Other variants of the embodiment of the fixed mount  31  and the movable mount  32  shown in FIGS. 1 through 5 a  are conceivable as well, and these variants are shown in FIGS. 11 through 13. Identical components are designated with the same reference numbers in FIGS. 11 through 13 as in FIGS. 1 through 5 a.  However, the spacers  23   a  for the fixed mount  31  and the spacers  24   a  for the movable mount  32  have a different design here. The spacer  23   a  for the fixed mount  31  is provided with two plate-shaped legs  31  arranged to the side of the bearing rail  21 , and the said legs are fixedly connected, namely, welded, to the bearing rail  21 , on the one hand, to the shaft wall  25 , on the other hand. The plate-shaped legs extend in parallel to the longitudinal central plane of the bearing rails  21 .  
         [0047]    The spacer  24   a  for the movable mount  32  analogously also has plate-shaped, upright legs  58 , which are likewise arranged on both sides of the bearing rail  21  and extend in a plane parallel to the longitudinal central plane of the bearing rail  21 . The bar  59  is arranged under the bearing rail  21  and extends transversely at right angles to the longitudinal central plane of the bearing rail  21 . The legs  58  are L-shaped in the side view (FIG. 11). If the shaft wall  25  is defined as “bottom,” the legs  58  form an upside-down L. Furthermore, the legs  58  are connected to a likewise plate-shaped bar  59 . With their horizontal legs  60 , the legs  58  engage a gap  38 , which is defined by the ring  37 , on the one hand, and by the bearing rail  21 , on the other hand, and is arranged on the right and left of the bearing rail  21 . The legs  60  are thus arranged on the left and right next to the bearing rail  21  and no longer under the bearing rail  21 , as in the variant according to FIG. 5.  
         [0048]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.