Abstract:
A device for sealing between the guide vanes ( 1 ) and the rotor ( 17 ) of turbomachines, especially gas turbines has inner rings ( 3 ) suspended on the vane footing ( 14 ) of the guide vanes ( 1 ) in a thermally elastic manner with soldered honeycomb seal ( 4 ) and labyrinth tips ( 5 ) arranged on the rotor ( 17 ). First flow channels, which are connected to the cavities ( 21 ) of the cooled guide vanes ( 1 ), through which said cavities cooling air flows, are led through the vane footings ( 14 ). The first flow channels are connected to at least one of second flow channels led through the inner ring ( 3 ) to the vicinity of the honeycomb seal ( 4 ). The second flow channels open into at least one of third flow channels that are open at the rear edge of the inner ring ( 3 ) or are led to an annular groove ( 10 ) open toward the honeycomb seal ( 4 ) on the underside of the inner ring ( 3 ).

Description:
FIELD OF THE INVENTION 
     The present invention pertains to a device for sealing between the guide vanes and the rotor of turbomachines, especially gas turbines. 
     BACKGROUND OF THE INVENTION 
     In a seal in turbomachines, which has been known from practice, the inner ring suspended on the guide vanes with the soldered honeycomb seal is uncooled. To reliably avoid a metallic contact between the rotor and the stator of the turbomachine, the distance between the honeycomb seal and the tips of the labyrinth must be dimensioned to the largest possible amount of the thermal expansion. The relatively great distance leads to a large leakage flow. 
     A cooled honeycomb seal, which is arranged at the outer limitation of the flow channel within a gas turbine, has been known from DE-A 19 821 365. Part of the cooling air, which is available to the guide vane located upstream at the outer shrouding, is fed for cooling to the honeycomb seal through holes in the ring carrying the honeycomb seal. 
     Gas turbines with internally cooled guide vanes have been known from U.S. Pat. Nos. 5,749,701 and 5,157,914. Sealing segments, which contain a honeycomb seal, are rigidly connected to the guide vanes. The sealing segments are fixed radially and are not suspended in a thermally elastic manner. Cooling air is fed to the sealing segments from the cooled guide vanes. This cooling air is used above all to block the sealing gap between the sealing segments and labyrinth tips and less to cool the honeycomb seal. The width of the sealing gap is not affected by the cooling air because of the non-thermally elastic suspension of the sealing segments. 
     SUMMARY OF THE INVENTION 
     The basic object of the present invention is to design the seal of this type such that the distance between the honeycomb seal and the labyrinth tips can be reduced to reduce the leakage flows while increasing the efficiency of the turbomachine at the same time. 
     According to the present invention a device for sealing between the guide vanes and the rotor of turbomachines, especially gas turbines with an inner ring suspended on the vane footing of the guide vanes in a thermally elastic manner with a soldered honeycomb seal and labyrinth tips arranged on the rotor. Each guide vane has a cavity through which cooling air flows. First flow channels are connected to the cavities of the guide vanes. The first flow channels are led through the vane footings of the guide vanes and the flow channels are connected to at least one of second flow channels. The second flow channels are led to the vicinity of the honeycomb seal and to which at least one connection leading to the outside of the inner ring is connected. 
     The second flow channels may open into at least one of axial third flow channel, which are open at the rear edge of the inner ring and form connections of the second flow channels, which connections lead to the outside of the inner ring. The second flow channels may be led to an annular groove open toward the honeycomb seal on the underside of the inner ring, which forms the connection of the second flow channels, which connection leads to the outside of the inner ring. 
     Fourth flow channels, which may be led to another annular groove open toward the honeycomb seal on the underside of the inner ring, may be branched off from the second flow channels. 
     The first flow channels may be designed as a hole each passing through the vane footing of the guide vanes. The first flow channels may be designed as an inner hole led through a hollow centering pin and as a hole connecting the inner hole to the cavity of the guide vane. 
     The second flow channels may be designed as holes led radially through the inner ring or as holes led three-dimensionally diagonally. The third flow channels may be designed as holes led axially through the inner ring. The fourth flow channels may be designed as holes led obliquely through the inner ring. 
     The inner ring may comprise two parts, which are provided with grooves and projections on sides facing each other. The grooves and projections may engage one another such that a serpentine-like, fifth flow channel is formed, to which at least one connection leading to the outside of the inner ring is connected. 
     The honeycomb seal may be protected by the cooling air discharged from the honeycomb seal and/or the inner ring against the break-in of hot gas. 
     The amount of the cooling air fed to the inner ring can be regulated and depending on the amount of the cooling air, the leakage flows flowing through the gap between the honeycomb seal and the labyrinth tips can flow only forward or both forward and backward. The amount of the cooling air fed to the inner ring can be regulated by the pressure of the cooling air in the guide vane, the diameter of the holes or by selecting the shape of the inlet and outlet of the holes. 
     The annular gap between the honeycomb seal and the labyrinth tips, which gap acts as a sealing gap, is determined decisively by the temperature of the inner ring suspended in a thermally elastic manner. The cooling air led through the inner ring cools this ring and thus lowers its component temperature. As a result, a smaller internal diameter of the honeycomb seal and consequently also a smaller annular gap become established because of the lower thermal expansion. Due to the inner ring being supplied with cooling air, the width of the sealing gap can thus be affected. The sealing gap can be dimensioned to be narrower from the very beginning. 
     Furthermore, the break-in of hot gas from the flow channel of the guide vanes into the honeycomb seal is avoided and the leakage flow will also decrease correspondingly as a result. This is associated with an increase in the efficiency of the turbomachine. The life-limiting material temperature is reduced, the temperature resistance and the corrosion resistance of the components affected are improved, and the service life of the part of the turbomachine exposed to hot gas is prolonged due to the cooling of the inner ring and of the honeycomb seal. A metallic contact between the rotor and the stator in transient states of the turbomachine can be avoided by regulating the cooling. Because of the advantageous properties indicated, the present invention is especially suitable for the hub sealing between the rotor and the stator of gas turbines. 
     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 preferred embodiments of the invention are illustrated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
     FIG. 1 is a detail X of a gas turbine according to FIG. 7 according to an embodiment of the invention; 
     FIG. 2 is a detail X of a gas turbine according to FIG. 7 according to another embodiment of the invention; 
     FIG. 3 is a detail X of a gas turbine according to FIG. 7 according to another embodiment of the invention; 
     FIG. 4 is a detail X of a gas turbine according to FIG. 7 according to another embodiment of the invention; 
     FIG. 5 is a detail X of a gas turbine according to FIG. 7 according to another embodiment of the invention; 
     FIG. 6 is a detail Z according to FIG. 3; 
     FIG. 7 is a schematic view showing the longitudinal section through a gas turbine; 
     FIG. 8 is a detail Z according to FIG. 3 of another embodiment of the invention; and 
     FIG. 9 is a schematic view showing an embodiment of the cooling air flow distributions; 
     FIG. 10 is a schematic view showing another embodiment of the cooling air flow distributions; and 
     FIG. 11 is a schematic view showing another embodiment of the cooling air flow distributions. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings in particular, the design of turbomachines as a gas turbine comprises, according to FIG. 7, a housing  16 , in which a rotor  17  is mounted rotatably. The rotor  17  carries a plurality of rows of guide vanes  18 , between which stationary guide vanes  1  fastened to the housing  16  are arranged. 
     Part of the rotor  17  with two guide vanes  18  and with the lower part of a guide vane  1  are shown in FIGS. 1 through 5 and  9  through  11 . 
     The guide vane  1  is provided with a guide vane footing  14  at its end facing the rotor  17 . An inner ring  3  is suspended at the guide vane footing  14  in a thermally elastic manner. The guide vane footing  14  is provided for this purpose with an attachment  19 , which engages an adapted recess  20  in the inner ring  3 , a gap  13  absorbing the thermal expansion being left between the front surface of the attachment  19  of the guide vane footing  14  and the bottom of the recess  20  of the inner ring  3 . Centering pins  2 , which are inserted into the attachment  19  of the guide vane footing  14  and into the bottom of the recess  20  of the inner ring  3 , ensure the centering of the inner ring  3  at the guide vane footing  14 . 
     A honeycomb seal  4  is soldered on the surface of the inner ring  3  facing the rotor  17 . The honeycomb seal  4  contains an open honeycomb structure, which is formed by webs. The webs are connected to the inner ring  3  and limit the inwardly open honeycombs. Labyrinth tips  5  of a one-part labyrinth ring acting as a seal, which ring is arranged on the rotor  17 , are located opposite the honeycomb seal  4 . There is a sealing gap of a radial height, which is to be kept small, between the labyrinth tips  5  rotating with the rotor  17  and the stationary honeycomb seal  4 . 
     The guide vanes  1  are cooled and have a cavity  21 , through which cooling air flows. The cooling air leaves at the rear edge  6  of the guide vane. 
     To keep the sealing gap between the stationary honeycomb seal  4  and the rotating labyrinth tips  5  small and to reduce the leakage flows passing through the sealing gap, the inner ring  3  and the honeycomb seal  4  are cooled as well. The cooling is brought about by a small partial flow of the cooling air used to cool the guide vane  1 , whose main flow escapes at the rear edge  6  of the guide vane. 
     The cooling air is taken from the guide vane  1 . A first flow channel, which is designed as a hole  15  and opens into the gap  13  between the guide vane footing  14  and the inner ring  3 , is led through the guide vane footing  14  for this purpose. Second flow channels  13 , which are led through the inner ring  3  as radial holes  7  or as three-dimensionally diagonal holes  11 , originate from the gap  13 . The holes  7 ,  11  open into third flow channels, which are led as axial holes  8  through the inner ring  3 . The axial holes  8  are open at the rear edge of the inner ring  3  and form the outlet  25 . The partial cooling air flow, which is taken from the guide vane  1  through the hole  15 , is distributed in the gap  13  between the guide vane footing  14  and the inner ring  3 , enters the radial and three-dimensionally diagonal holes  7 ,  11 , and escapes via the axial holes  8  through the outlets  25 . The cooling air taken from the guide vane  1  lowers the temperature of the inner ring  3  and the honeycomb seal  4  while this passes over the holes  7 ,  11 ,  8  (FIGS. 1,  3 ,  6 ). 
     According to FIG. 8, the first flow channel may also be designed as an inner hole  23  of a hollow centering pin  2 , the inner hole  23  being in connection with the cavity  21  of the guide vane  1  via a hole  24  extending radially through the guide vane footing  14 . At least one of the radial holes  7 , which are likewise designed as a second flow channel, is connected to the inner hole  23  of the hollow centering pin  2 . One of the radial holes  7  each opens into one of the axial holes  8  each. 
     According to FIG. 4, the radial holes  7  end in an open annular groove  10 , which is cut into the surface of the inner ring  3  facing the rotor  17 . The cooling air taken from the guide vane  1  is discharged through the honeycomb seal  4  and cools same directly in the process. 
     As is shown in FIG. 2, fourth flow channels, which are led as oblique holes  9  through the inner ring  3  and end in another annular groove  22 , may branch off from at least one of the radial holes  7 , which act as second flow channels. The honeycomb seal  4  is thus cooled over a large area. 
     According to FIG. 5, the inner ring  3  comprises two parts, which are provided with grooves and projections on the sides facing one another. The two parts of the inner ring  3  are fitted together such that the grooves and projections engage one another and form serpentines  12  as a result, which represent a fifth flow channel led through the inner ring  3 . The serpentines  12  are in connection with the axial holes  8 . Due to this serpentine-like guiding of the cooling air, the residence time of the cooling air in the inner ring  3  is longer than in the other embodiments described. In addition, the surface available for heat transfer (cooling) is increased by the serpentines  12  and so is the effectiveness of the cooling. 
     FIGS. 9 through 11 show the cooling air flows a through  1  in the area of the inner ring  3  for different variants; these cooling air flows are composed as follows: 
     a) Cooling air flowing from the guide vanes  18  of the moving blade ring, which is arranged in front of the guide vane  1  shown, 
     b) as a), but on a radius closer to the rotor axis, 
     c) indifferent distribution flow between the rotor  17  and the inner ring  3 , 
     d) cooling air that escapes into the flow channel in front of the guide vanes  1 , 
     e) hot gas, 
     f) leakage flow (flowing forward in FIG.  10  and backward in FIG.  11 ), 
     g) cooling air that flows from the guide vanes  18  of the moving blade ring that is arranged behind the guide vane  1  shown, 
     h) as d), but behind the guide vanes  1 , 
     k) cooling air that is fed from the cavity  21  of the guide vane  1  to the inner ring  3 , 
     l) leakage flow. 
     FIG. 9 shows the cooling air flows a through h for the uncooled variant of the inner ring  3  according to the state of the art. As is apparent from FIG. 9, a hot gas flow e is drawn from the flow channel of the guide vane  1  into the annular gap between the honeycomb seal  4  and the labyrinth tips  5  and it leads to an increase in the leakage flow f there. This leads, furthermore, to an increase in the temperature of the inner ring  3  with a further thermal elastic expansion of the inner ring  3 . 
     FIGS. 10 and 11 show the cooling air flows a through l for the cooled variant of the inner ring  3 , where the cooling air flow k is small in FIG.  10  and large in FIG.  11 . The amount of the cooling air flow k can be changed by a higher pressure of the cooling air in the guide vane  1 , a larger diameter of the hole  7  or by changing the flow resistance by selecting the shape of the inlet and outlet (rounded, sharp-edged) of the hole  7 . 
     FIG. 10 shows a variant with cooling of the inner ring  3 , where the cooling air flow k is a cooling air flow of a small volume. It can be seen that the break-in of hot gas e is avoided and a substantially smaller leakage flow f flows through the annular gap between the honeycomb seal  4  and the labyrinth tips  5 . The leakage flow f flows through the annular gap between the honeycomb seal  4  and the labyrinth tips  5  in one direction. 
     If the cooling air flow k is increased, as is shown in FIG. 11, it is split into the two leakage flows f and l, which leave the annular gap between the honeycomb seal  4  and the labyrinth tips  5  on both sides of the inner ring  3 . The break-in of hot gas e and the pumping action are avoided in this case as well. The inner ring  3  assumes a lower temperature, and thermal elastic expansion is avoided in both FIG.  10  and FIG.  11 . 
     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.