Abstract:
A device for protecting against oil leaks towards the rotors of a turbomachine turbine includes an upstream cavity in which an oil/air mixture can circulate, the upstream cavity being delimited downstream by a journal of the turbine rotor and on the outside by a sealing flange of the journal extending axially in an upstream direction, a downstream cavity opening towards the discs of the turbine and communicating with the upstream cavity via a plurality of ventilation holes provided in the journal, and an upstream annular deflector fixed to the sealing flange of the journal and extending radially inwards towards the ventilation holes The upstream deflector has oil passage ports provided at the end of same secured to the sealing flange of the journal.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to the general field of turbines of a turbomachine, and especially of the low-pressure turbine. It also relates more precisely to a device for protecting the rotors of a turbine against the risks of an oil fire. 
         [0002]    The low-pressure shaft of a turbomachine drives in rotation the different stages of the low-pressure turbine by means of a journal fixed on the low-pressure shaft. This journal delimits upstream an inner upstream cavity in which air travels intended to ventilate the different discs of the low-pressure turbine arranged downstream from this journal. 
         [0003]    To this end, the journal of the low-pressure shaft has ventilation holes enabling ventilation air taken upstream in the motor to feed an outer downstream cavity by transiting via an inner upstream cavity. This ventilation air is then guided towards the discs of the different stages of the low-pressure turbine downstream of the journal to cool them. 
         [0004]    Also, it is possible for oil originating from leaks of the lubrication circuit and oil containers of the turbomachine to also be present in the inner upstream cavity of the low-pressure turbine. This oil tends to mix with the ventilation air and borrow the same path as the latter, to end up in the downstream cavity of the low-pressure turbine. 
         [0005]    The environment of this downstream cavity is relatively hot, which can cause an oil fire in this cavity with all the harmful consequences this could engender. 
       OBJECT AND SUMMARY OF THE INVENTION 
       [0006]    The principal aim of the present invention therefore is to eliminate such drawbacks by proposing a device for protecting the rotors of the turbine against the risks of an oil fire. 
         [0007]    To this end, a device for protecting against oil leaks towards the rotors of a turbomachine turbine is provided, comprising an upstream cavity in which an air/oil mixture can circulate, said upstream cavity being delimited downstream by a journal of the turbine rotor and to the outside by a sealing flange of the journal axially extending towards upstream, and a downstream cavity opening towards the discs of the turbine and communicating with the upstream cavity by a plurality of ventilation holes made in the journal, and further comprising according to the invention an annular upstream deflector fixed on the sealing flange of the journal and radially extending towards the inside in the direction of the ventilation holes, the upstream deflector exhibiting oil flow orifices made at the level of its end fixed on the sealing flange of the journal. 
         [0008]    The presence of the upstream deflector minimises the quantity of oil moving from the upstream cavity to the downstream cavity. In fact, this upstream deflector especially forms an obstacle to the direct trajectory of the air/oil mixture passing through the ventilation holes made in the journal. 
         [0009]    Also, the positioning of this upstream deflector ensures separation between the trajectory of the air and the trajectory of the oil. In particular, under the effect of the pressure differential between the upstream cavity and the downstream cavity the air of the air/oil mixture will tend to pass under the upstream deflector and travel as far as the downstream cavity by passing through the ventilation holes. As for the oil of the air/oil mixture, once it passes the upstream deflector under the effect of the rotary centrifugal force of the journal it will tend to press against the inner wall of the sealing flange of the journal and rise upstream along the latter. The presence of oil flow orifices at the level of the end of the upstream deflector which is fixed on the sealing flange of the journal allows the oil to be evacuated upstream of the upstream cavity, without encountering countercurrent airflow. 
         [0010]    In this way, the device according to the invention produces deoiling of the air/oil mixture present in the upstream cavity with the oil which is evacuated upstream to be recovered and the air which feeds the downstream cavity to ventilate the rotors of the turbine. 
         [0011]    Preferably, the upstream deflector radially extends towards the inside so as to mask the ventilation holes made in the journal. 
         [0012]    Preferably also, the upstream deflector comprises a fixing flange which is fixed on the sealing flange of the journal by means of fastening systems of the sealing flange of the journal on the journal. In this case, the oil flow orifices are advantageously made in the fixing flange of the upstream deflector and angularly positioned between the fastening systems of the sealing flange of the journal on the journal. 
         [0013]    More preferably, the device further comprises a downstream annular deflector fixed on the journal and radially extending towards the outside in the direction of the ventilation holes so as to delimit with the upstream deflector a baffle for the air/oil mixture circulating in the upstream cavity. The presence of such a baffle favours separation between the air and the oil of the air/oil mixture and accentuates the centrifuging of the oil on the inner wall of the sealing flange of the journal. 
         [0014]    In this case, the downstream deflector extends advantageously radially towards the outside so as to mask the ventilation holes. This masking favours the capturing on the upstream deflector of any direct projections of oil. 
         [0015]    Similarly, the downstream deflector is advantageously axially interposed between the upstream deflector and the ventilation holes made in the journal. 
         [0016]    The device can further comprise stiffeners ensuring a link between free ends of the upstream and downstream deflectors. 
         [0017]    The downstream deflector can comprise a fixing flange which is fixed on the journal by means of fastening systems of the journal on a turbine shaft. 
         [0018]    Another aim of the invention is a turbomachine turbine comprising a device for protecting against oil leaks such as defined previously. Yet another aim of the invention is a turbomachine comprising such a turbine. 
     
    
     
       BRIEF DESCRIPTION OF THE DIAGRAMS 
         [0019]    Other characteristics and advantages of the present invention will emerge from the following description in reference to the appended drawings which illustrate embodiments devoid of any limiting character, in which: 
           [0020]      FIG. 1  is a schematic view of a device for protecting against oil leaks according to the invention; 
           [0021]      FIG. 2  is a perspective view of the upstream deflector of the device for protecting of  FIG. 1 ; and 
           [0022]      FIGS. 3 and 4  are schematic views of devices for protecting against oil leaks according to variant embodiments of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]      FIG. 1  schematically and partially shows a low-pressure turbine  2  of a turbomachine equipped with a device for protecting against oil leaks according to the invention. Of course, the invention applies to any turbomachine turbine. 
         [0024]    As is known per se, the low-pressure turbine  2  comprises a low-pressure  4  shaft centred on a longitudinal axis  6  of the turbomachine. 
         [0025]    For the rest of the description, the terms “upstream” and “downstream” will be used relative to the direction of flow of the gas flow passing through the turbomachine. Similarly, the terms “inside” and “outside” will be used relative to the longitudinal axis  6  of the turbomachine. 
         [0026]    Fixed to the low-pressure shaft  4  is the inner radial end of a journal  8  by means of a plurality of fastening systems  10 , for example of the screw/nut type. At the level of its opposite radial end, the journal  8  is attached to a rotor disc  12  of a stage of the low-pressure turbine which it drives in rotation around the longitudinal axis  6 . As shown in  FIG. 1 , this rotor disc  12  is connected to the rotor discs  12  of the other stages of the low-pressure turbine. 
         [0027]    The journal  8  of the low-pressure turbine also comprises a sealing flange  14  which extends axially upstream. This sealing flange  14  bears a sealing device (for example a labyrinth seal, not shown in the figures). This sealing flange can be fixed to the journal by means of a plurality of fastening systems  16 , for example of screw/nut type. 
         [0028]    The journal  8  of the low-pressure turbine (and its sealing flange  14 ) delimits two cavities, specifically an upstream cavity  18  and a downstream cavity  20 . 
         [0029]    More precisely, the upstream cavity  18  is formed on the inner side and is delimited on the one hand radially to the outside by the sealing flange  14  of the journal, and on the other hand axially downstream by the journal itself. As for the downstream cavity  20 , it is formed on the outer side and is delimited on the one hand axially to the upstream by the journal and on the other hand radially to the outside by the rotor discs  12 . 
         [0030]    The upstream  18  and downstream  20  cavities communicate with each other by means of a plurality of ventilation holes  22  made in the journal  8  and uniformly distributed around the longitudinal axis  6  of the turbomachine. As is known, the downstream cavity  20  terminates towards ventilation circuits of the rotor discs of the different stages of the low-pressure turbine (not shown in the figures). 
         [0031]    Air taken upstream in the turbomachine feeds the upstream cavity  18  to then move to the downstream cavity  20  (by setting up a pressure differential between the two cavities) where it is used to feed the ventilation circuits of the rotor discs. 
         [0032]    Also, it is possible for oil originating from leaks of the lubrication circuit and oil containers of the turbomachine (not shown in the figures) also ends up in the upstream cavity  18 . Now, this oil does not have to end up in the downstream cavity  20  to avoid any risk of triggering a fire. 
         [0033]    To this end, in keeping with the invention an annular upstream deflector  24  is provided which is fixed on the sealing flange  14  of the journal. This upstream deflector  24  is for example formed from sheet metal and radially extends towards the inside in the direction of the ventilation holes  22  made in the journal so as to mask them. 
         [0034]    Also, as shown in  FIG. 2 , the upstream deflector  24  has oil flow orifices  26  which are made at the level of its end fixed on the sealing flange  14  of the journal. 
         [0035]    More precisely, the upstream deflector  24  comprises a fixing flange  24   a  which can be fixed on the sealing flange  14  of the journal by means of fastening systems  16  of the sealing flange on the journal. To this end, the sealing flange  14  of the journal and the journal  8  have scallops, respectively  14   a  and  8   a , which are fixed together by the fastening systems  16 . 
         [0036]    The oil passage holes  26  are made in the fixing flange  24   a  of the upstream deflector  24  and are angularly positioned between the respective scallops  14   a ,  8   a  of the sealing flange  14  of the journal and of the journal  8 . 
         [0037]    These oil passage holes  26  can be uniformly distributed around the longitudinal axis  6  of the turbomachine and their number and their dimensions are adapted especially as a function of the quantity of oil to be evacuated. 
         [0038]    The fixing flange  24   a  of the upstream deflector  24  also ensures masking of the areas angularly located between the respective scallops  8   a ,  14   a  of the journal and its sealing flange so as to force the passage of air to pass through the inside of the upstream deflector. 
         [0039]    Preferably, the dimension of the oil passage holes  26  is relatively small so that they can rapidly be “filled” of oil and avoid any passage of air. The passage of air at the level of the end of the upstream deflector which is fixed on the sealing flange of the journal is also prohibited by the presence of the fixing flange  24   a  of the deflector which forms an obstacle to such passage. 
         [0040]    In this way, the upstream deflector  24  masks the ventilation holes  22  made in the journal  8 , preventing the air/oil mixture flowing in the upstream cavity  18  from passing through these ventilation holes to join the downstream cavity  20 . 
         [0041]    Instead, the air/oil mixture (its trajectory is traced by a solid line in  FIG. 1 ) bypasses the upstream deflector. When leaving the upstream deflector and under the effect of the centrifugal rotation force of the journal  8 , this air/oil mixture separates into an oil trajectory (traced by mixed lines) which presses against the inner wall of the sealing flange  14  of the journal  8  and rises upstream along the latter, especially by borrowing the oil passage holes  26  made in the fixing flange  24   a  of the upstream deflector, and into an air trajectory (traced by dotted lines) which borrows the ventilation holes  22  made in the journal under the effect of the pressure differential in between the upstream and downstream cavities. 
         [0042]    The deoiled air enters the downstream cavity and can feed the ventilation circuits of the rotor discs of the different stages of the low-pressure turbine. As for the oil recovered against the inner wall of the sealing flange of the journal, it travels upstream along this wall under the effect of the centrifugal force and can be recovered further upstream, for example by means of scoops (not shown in the figures). 
         [0043]      FIG. 3  shows a variant embodiment of the device for protecting against oil leaks according to the invention. 
         [0044]    This device for protecting is identical to that described in conjunction with  FIGS. 1 and 2  and further comprises a downstream annular deflector  28  which is fixed on the journal  8 . The downstream deflector  28  is for example formed from sheet metal and radially extends towards the outside in the direction of the ventilation holes  22  made in the journal  8  so as to mask them. 
         [0045]    More precisely, this downstream deflector  28  is axially interposed between the upstream deflector  24  and the ventilation holes  22  and forms with the upstream deflector a baffle for the air/oil mixture circulating in the upstream cavity  18  (its trajectory is traced by a solid line). 
         [0046]    The downstream deflector  28  comprises a fixing flange  28   a  which can be fixed on the journal  8  by means of fastening systems  10  of the journal  8  on the low-pressure shaft  4 . 
         [0047]    So by masking the ventilation holes  22 , the upstream  24  and downstream  28  deflectors prevent the air/oil mixture flowing in the upstream cavity  18  from directly passing through these ventilation holes to join the downstream cavity  20 . 
         [0048]    When leaving the baffle formed by the deflectors  24 ,  28 , and under the effect of the centrifugal rotation force of the journal, the air/oil mixture separates into an oil trajectory (traced by mixed lines) which presses against the inner wall of the sealing flange  14  of the journal and rises upstream along the latter, especially by, and into an air trajectory (traced by dotted lines) which borrows the ventilation holes  22  under the effect of the pressure differential in between the upstream and downstream cavities. 
         [0049]    The deoiled air enters the downstream cavity and can feed the ventilation circuits of the rotor discs of the different stages of the low-pressure turbine. As for the oil recovered against the inner wall of the sealing flange of the journal, it travels upstream along this wall under the effect of the centrifugal force and can be recovered further upstream. 
         [0050]      FIG. 4  shows another variant embodiment of the device for protecting against oil leaks according to the invention. 
         [0051]    The device according to this variant is identical to that described in conjunction with  FIG. 3  and further comprises stiffeners  30  ensuring a link between free ends of the upstream  24  and downstream  28  deflectors (that is, their ends opposite the fixing flange). 
         [0052]    These stiffeners  30  can be simples metal sheets fixed at the free ends of the deflectors  24 ,  28  and angularly spaced to each other to allow passage of the air/oil mixture. They impart a certain mechanical hold on the device for resulting protection.