Patent Document

TECHNICAL FIELD 
       [0001]    The invention relates generally to gas turbine engines, and more particularly to seals for rotating components in a gas turbine engine. 
       BACKGROUND OF THE ART 
       [0002]    Contact seals, often made of carbon and hence referred to correctly or incorrectly as carbon seals, are commonly used to provide a fluid seal around a rotating shaft, particularly high speed rotating shafts used in high temperature environments such as in gas turbine engines. Such contact seals usually comprise ring segments and a seal runner which abut and rotate relative to each other to form a rubbing, contact interface which creates a fluid seal around the shaft. Pressurized gas can be used to force the ring segments against the seal runner and create a gas pressure differential with the bearing cavity which repels impinging oil. Typically, but not necessarily, the seal runner is disposed on the rotating shaft and rotates within an outer stationary ring, causing the rubbing interface between the rotating seal runner and the rotationally-stationary ring. Although efforts are made to limit friction, the rubbing contact can generate significant heat during operation, especially in the context of high rotational speeds of gas turbine engine shafts, and means are provided to dissipate this heat. This heat dissipation is most often accomplished using fluid cooling, for example oil from the engine&#39;s recirculating oil system which is sprayed onto exposed surfaces of the seal runner and/or the ring. 
         [0003]    There always remains room for improvement. 
       SUMMARY 
       [0004]    In one aspect, there is provided a seal runner for use in a contact seal assembly of a gas turbine engine, the seal runner having an annular body securable to a rotating shaft of the gas turbine engine during use whereas ring segments of the contact seal assembly are securable to a case of the gas turbine engine during use, the seal runner having a radially-outer surface having a contacting portion adapted to rubbingly receive ring segments of the contact seal assembly during use, the seal runner having a radially-inner surface opposite to the radially-outer surface, the radially-inner surface extending axially, and a cooling fluid passage having a segment extending along the radially-inner surface of the seal runner and leading axially to an outlet, the outlet having an inlet end receiving the cooling fluid from the cooling fluid passage during use, the inlet end being radially spaced apart from the radially-inner surface of the seal runner by a given spacing distance in a manner to form a pool of cooling fluid having a depth corresponding to the given spacing distance and extending opposite to the contacting portion of the radially-outer surface. 
         [0005]    In another aspect, there is provided a gas turbine engine comprising a contact seal assembly having a seal runner having an annular body securable to a rotating shaft of the gas turbine engine during use whereas ring segments of the contact seal assembly are securable to a case of the gas turbine engine during use, the seal runner having a radially-outer surface having a contacting portion adapted to rubbingly receive ring segments of the contact seal assembly during use, the seal runner having a radially-inner surface opposite to the radially-outer surface, the radially-inner surface extending axially, and a cooling fluid passage having a segment extending along the radially-inner surface of the seal runner and leading axially to an outlet, the outlet having an inlet end receiving the cooling fluid from the cooling fluid passage during use, the inlet end being radially spaced apart from the radially-inner surface of the seal runner by a given spacing distance in a manner to form a pool of cooling fluid having a depth corresponding to the given spacing distance and extending opposite to the contacting portion of the radially-outer surface. 
         [0006]    In a further aspect, there is provided a method of internally cooling a seal runner of a gas turbine engine, the seal runner having an annular body secured to a rotating shaft of the gas turbine engine whereas ring segments are secured to a case of the gas turbine, with the seal runner having a radially-outer surface having a contacting portion adapted to rubbingly receive ring segments of the contact seal assembly during use, the seal runner having a radially-inner surface opposite to the radially-outer surface, the method comprising: rotating the seal runner relative to the ring segments and generating heat from the rubbing engagement therebetween; and feeding a flow of cooling fluid against the radially-inner surface to cool the seal runner from said generated heat including maintaining a pool of cooling fluid having a given depth against the radially-inner surface. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0007]    Reference is now made to the accompanying figures in which: 
           [0008]      FIG. 1  is a schematic cross-sectional view of a gas turbine engine; 
           [0009]      FIG. 2  is a partial cross-sectional view of a bearing and seal assembly; 
           [0010]      FIG. 3  is an enlarged portion of  FIG. 2  showing a contact seal assembly with an internally cooled seal runner in greater detail; 
           [0011]      FIG. 4  is another partial cross-sectional view of a bearing and seal assembly showing the cooling fluid flow configuration; and 
           [0012]      FIG. 5  is a schematic cross-sectional view of another embodiment of a contact seal assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  illustrates a turbofan gas turbine engine  10  of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan  12  through which ambient air is propelled, a multistage compressor  14  for pressurizing the air, a combustor  16  in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section  18  for extracting energy from the combustion gases. 
         [0014]    In the depicted embodiment, the turbine section  18  comprises a low pressure turbine  17  and a high pressure turbine  19 . The engine  10  also preferably includes at least two rotating main engine shafts, namely a first inner shaft  11  interconnecting the fan  12  with the low pressure turbine  17 , and a second outer shaft  13  interconnecting the compressor  14  with the high pressure turbine  19 . The inner and outer main engine shafts  11  and  13  are concentric and rotate about the centerline axis  15  which is collinear with their longitudinal axes. 
         [0015]    The main engine shafts  11 ,  13  are supported at a plurality of points by bearings, and extend through several engine cavities. As such, a number of shaft seals are provided to ensure sealing about the shafts at several points along their length to prevent unwanted fluid leaking from one engine compartment or cavity. For example, in some engine configurations, compressed air in the main engine gas passage must be kept separate from the secondary cooling air or bearing lubrication oil in bearing cavities and cooling cavities adjacent to the main engine gas passage. 
         [0016]    Referring now to  FIG. 2 , at least one of the shaft seals used to seal the rotating shaft  11  and/or  13  in the engine  10  is a contact seal  20 , as will now be described in further detail. 
         [0017]    The contact seal  20  includes generally a number of rotationally stationary ring segments  22  (made of carbon in this embodiment) which together form at least one circumferentially interrupted annular ring assembly, and a rotating seal runner  30  connected to one of the rotating engine shafts of the gas turbine engine  10  (such as the shaft  11  in this example) and rotatable relative to the ring segments  22 . In this embodiment, the ring segments  22  are arcuate carbon segments circumferentially arranged within the seal housing  24 , the housing  24  being, in turn, fastened in fixed position to a supporting engine support and/or casing segment which will be generally referred to herein as a case  25 . Further, as seen in  FIG. 2 , the ring segments  22  may include a pair of axially spaced segmented annular ring assemblies. 
         [0018]    Referring still to  FIG. 2 , the seal and bearing assembly can be seen to include a radially bearing inner ring  62  and a radially bearing outer ring  64  which cooperate in receiving roller bearings  66  therein during use. The radially bearing outer ring  64  is mounted to the engine case  25  and are thus made integral to the ring segments  22  whereas the radially-bearing inner ring  62  is mounted to the shaft  11  and rotates with the seal runner  30 . The radially-bearing outer ring  64  is axially spaced apart from the contact seal  20  and a bearing cavity  67  extends therebetween. The bearing cavity  67  leads to a radially external scavenge window  68  in the case  25 . 
         [0019]    Referring still to  FIG. 2 , the annular seal runner  30  is located adjacent to and radially inwardly from the ring segments  22  to thereby create a rotating contact interface between the ring segments  22  and the rotating seal runner  30 , to form a substantially fluid tight seal therebetween when the engine shaft  11  rotates during operation of the engine  10 . More particularly, a portion  92  of the radially-outer surface  32  of the seal runner  30 , which can be referred to as a contacting portion  92  or ring-segment-receiving portion, contacts the radially-inner surfaces  23  of the ring segments  22 . As will be seen, the seal runner  30  is internally cooled, in that the radially-outer surface  32  of the seal runner does not require external spray cooling but rather is cooled from within by circulating the cooling fluid (such as, but not necessarily, oil) internally within the cooling fluid passage  40  formed within the seal runner  30 , and more specifically against a radially-inner surface  33  which is radially-opposite to the radially-outer surface  32  which receives the heat, and more specifically extends along the axial coordinates of the contacting portion  92 . The cooling fluid is distributed to the seal runner via one or more non-rotating cooling fluid nozzles  21  and the configuration of the seal and bearing assembly is designed for the cooling fluid to be carried, given centripetal acceleration in the context of the rotating components forming the cooling fluid passage, along a given passage and to and along the cooling fluid passage  40  formed in the seal runner  30 . 
         [0020]    As perhaps best seen in  FIG. 3 , in this specific embodiment, the seal runner  30  comprises a first and a second annular portions which will be referred to herein as the runner portion  34  and the sleeve portion  36  for ease of reference. The runner portion  34  and the sleeve portion  36  are concentric with one another, axially elongated and at least partially axially overlapping, and radially spaced apart from one another in a manner that the radial spacing between the sleeve portion  36  and the runner portion  34  forms a returning segment  44  of the cooling fluid passage  40  (e.g. returning toward the bearing). Moreover, in this embodiment, an enclosing portion of cooling fluid passage  40  is formed by the radially-outer surface of the shaft  11  which is also annular (hollow) and axially elongated, extending from a spray receiving inlet associated with the position of the nozzles  21 , radially-inside the bearing and the seal runner  30  where it internally encloses the cooling fluid passage  40 , and leading, in this particular embodiment, to a fan and boost attachment (an example general flow configuration of the cooling fluid being shown with arrows in  FIG. 4  for ease of understanding). Accordingly, an outgoing segment of the cooling fluid passage can be said to be formed between the sleeve portion  36  and the shaft  11 . 
         [0021]    During use, cooling fluid enters the cooling fluid passage  40  via an inlet  46  located at a proximal end  27  of the seal runner  30 . Centripetal acceleration combined with the designed shape of the runner components directs the cooling fluid in a manner to form a film which travels axially against a radially-inner surface of the sleeve portion  36  from the inlet  46  toward the distal end of the seal runner  30 . A radial segment  48  of the cooling fluid passage  40  is provided at the distal end of the seal runner, bridging the outgoing segment  42  and the returning segment  44  of the cooling fluid passage  40 . In this specific embodiment, the radial segment  48  is provided in the form of a gap extending between a distal edge of the sleeve portion  36  and an abutted joint between a distal end of the runner portion  34  and the shaft  11  and which is sealed with an O-ring member  49  trapped therebetween, however, in alternate embodiments, it will be understood that the radial segment  48  can be in the form of apertures formed in the sleeve portion, for instance. Cooling fluid travels in the radial segment  48  in a radially outward direction across radial thickness of the sleeve portion  36 , and against a radially-inward face of the runner portion  34 . Cooling fluid then travels back toward the bearing along the radially-inner surface  33  of the runner portion  34  and exits the cooling fluid passage  40  at the proximal end  27  of the seal runner  30  by an outlet  70  which can be in the form of a plurality of circumferentially interspaced apertures  72  across the proximal end  27  of the runner portion  34  or in the form of an annular aperture or of a plurality of circumferentially interspaced partially-annular (arcuate) apertures formed in the proximal end  27  of the runner portion  34 , to name a few examples. The cooling fluid exiting the cooling fluid passage  40  in the seal runner  30  escapes to the bearing cavity  67  and through the scavenge window  68 . 
         [0022]    It will be noted in this embodiment that the one or more outlet apertures  72  across the runner portion  34  have an inlet end  74  and an outlet end, and that the inlet end  74  of the outlet apertures  72  is radially spaced-apart from the axially-extending internal surface  33  of the runner portion  34  which extends along the outer contact surface  32  of the runner portion  34  which contacts the ring segments  22  and which receives heat from the rubbing engagement therewith during use of the gas turbine engine. This radial spacing  76 , also referred to herein as the ‘given spacing distance  76 ’, between the inlet end  72  of the outlet  70  and the radially-inner (cooling) surface  33  of the runner portion  34 , forms an annular pocket  78  which has the given radial spacing  76  and in which an annular pool of cooling fluid having a corresponding depth can be received and be maintained during use, which can assist in optimizing the cooling action. Accordingly, during use, an annular pool of cooling fluid of a given depth is maintained in the annular pocket as ‘new’, or ‘cold’ cooling fluid enters the annular pool from the radial segment  48  at the distal end  29  and ‘used’ or ‘hot’ cooling fluid exits the annular pool from the outlet  70  at the proximal end  27 . In this specific embodiment, the pool extends at least along the axial length of the contacting portion  92 , opposite thereto, to directly evacuate the heat generated thereon by the rubbing. 
         [0023]    More specifically, in this embodiment, the runner portion  34  has a radially-inward extending portion  80  adjacent to the radially-inner cooling surface  33 , and the outlet  70  is provided in the form of at least one aperture  72  provided across the radially-inward extending portion  80 . 
         [0024]    Moreover, in this embodiment, the sleeve portion  36  of the seal runner  30  is formed with an annular recessed portion  82  on the radially-inner, cooling-fluid-guiding surface thereof, which is positioned near the distal end of the sleeve portion  36 , and in which cooling fluid can accumulate and even out (uniformize) in a manner to then be distributed into the radially-outward segment  48  in a more circumferentially uniform film or flow than if the cooling fluid was not allowed to even out in the recessed portion  82 . Accordingly, in this specific embodiment, the function of the recessed portion  82  in the sleeve portion, which can alternately be referred to herein as a ‘gutter’ for ease of reference, is to allow evening out of the flow of cooling fluid in the circumferential orientation by contrast with the function of the radial spacing  76  between the inlet end  74  of the outlet  70  and the radially-inner surface  33  of the runner portion  34  which is to form the annular pool of cooling fluid having a given depth immediately against the portion of the seal runner which is likely to be most exposed to heat during use. 
         [0025]    It will be understood that in the embodiment shown in  FIG. 2 , the bearing and seal assembly shown is a bearing and seal assembly of a low pressure fan/boost stage, but it will be understood that the internally-cooled seal runner described herein can alternately be applied to a turbine stage, or to a high-pressure compressor stage, for instance. In alternate embodiments, the seal can be forward of the bearing or rearward of the bearing. 
         [0026]    As noted above, at least one cooling fluid passage  40  is radially defined within the seal runner  30 , into which cooling oil is fed to cool the seal runner  30  in general, and the runner portion  34  having the outer contact surface  32  thereon in particular. Accordingly, the cooling fluid passage  40  is internally formed within the seal runner  30  such that the seal runner  30  is cooled from within. Cooling oil within the cooling fluid passage  40  will be forced radially outward by centrifugal force, thereby ensuring that the cooling oil is maintained in contact with the inner surface of the runner portion  34 , which defines the contact surface on the opposed radially-outer surface for rubbing against the ring segments  22 . Thus, the underside of the runner surface is cooled internally, by absorbing the heat therefrom using the circulating oil flow. Further, the centrifugal force of the shaft rotating will also generate pumping of the cooling oil. 
         [0027]    The seal runner  30  may be formed in a number of different manners, and may comprise one, two or more separate components which together form the seal runner  30 . For example, in one embodiment the seal runner  30  may be formed using a three-dimensional printing production technique, whereby the seal runner  30  is integrally formed of a single piece (i.e. is monolithic). In another possible embodiment of the present disclosure, the seal runner  30  is composed of two or more portions, which are separately formed and engaged or otherwise assembled together to form the finished seal runner  30 . Although welds may be used to engage the components of the seal runner  30  together, other suitable engagements means may also be used, such as for example only, brazing, bonding, adhering, fastening, trapping abutment, etc. 
         [0028]    Referring to  FIG. 5 , another embodiment of an annular seal runner  130  is shown. The annular seal runner  130  is located adjacent to and radially inwardly from the ring segments  122  to thereby create a rotating contact interface between the ring segments  122  and the rotating seal runner  130 , to form a substantially fluid tight seal therebetween when the engine shaft  13  rotates during operation of the engine  10 . More particularly, a radially-outer surface  132  of the seal runner  130  contacts the radially-inner surfaces  123  of the ring segments  122 . As will be seen, the seal runner  130  is internally cooled, in that the radially-outer contact surface  132  of the seal runner does not require external spray cooling but rather is cooled from within by circulating the cooling fluid (such as, but not necessarily, oil) internally within the cooling fluid passage  140  formed within the seal runner  130 . The cooling oil is distributed to the seal runner via one or more cooling fluid nozzles  121  which feed the cooling oil radially inwardly onto the circumferentially extending open topped channel  154  disposed at a proximal end  127  of the seal runner  130 . Moreover, radially-bearing inner ring  162  and a radially-bearing outer ring  164  which cooperate in receiving roller bearings  166  therein during use. The radially-bearing outer ring  164  is mounted to the engine case  125  with the ring segments  122  whereas the radially-bearing inner ring  162  is mounted to the shaft  13  with the seal runner  130  and an annular scoop member  153 . 
         [0029]    For instance, an embodiment such as shown in  FIG. 5  can have incorporated therein either one of the feature of the pool of cooling liquid having a given depth on the radially-inner surface of the runner portion and the feature of the gutter on the radially-inner surface of the sleeve portion to uniformize the flow of cooling liquid across the radial segment of the cooling fluid passage. 
         [0030]    When used in a gas turbine engine  10  such as that depicted in  FIG. 1 , the present seal runner may be used about any rotating shaft or other element thereof, such as for example about at least one of the main engine shafts  11  and  13 . Alternately, the seal runner may be employed to seal another rotating shaft in the gas turbine engine  10  or in another turbomachine, pump, compressor, turbocharger or the like. The seal runner  30  may be mounted to the shaft using any suitable means such that it rotates within the ring segments  22  and remains in contact therewith when the shaft rotates. Thus, the contact seal provides a fluid seal about the rotating shaft. Moreover, it will be understood that the seal and bearing assembly can be suitable for use in other gas turbine engines than turbofan engines, such as turboprop or turboshaft engines to name other examples. 
         [0031]    The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. Moreover, in alternate embodiments, the cooling fluid passage can be in the form of a continuous annular passage around the rotation axis of the shaft, or provided in the form of a plurality of arcuate passage portions interspaced circumferentially from one another around the shaft. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.

Technology Category: 2