Abstract:
An assembly for a turbomachine combustion chamber, including a boss for turbomachine combustion chamber, including a tubular body configured to be inserted in a receiving orifice formed in an annular wall of a flame tube and to accommodate a shank of a connecting pin for connecting the flame tube to an external casing, a first end of the boss including an annular flange configured to prevent radial translational movement of the boss in a first direction, and a second end of the boss being configured to be crimped to the wall of the flame tube so as to prevent radial translational movement of the boss in a second direction, and an annular element configured to fit coaxially with the receiving orifice and in radial contact with the annular wall of the flame tube on the one hand and with the annular flange of the boss on the other.

Description:
GENERAL TECHNICAL FIELD 
       [0001]    The invention relates generally to the field of combustion chambers for turbine engines, and more particularly to the attachment of a flame tube in a turbine engine combustion chamber. 
       PRIOR ART 
       [0002]    A turbine engine generally comprises, from upstream to downstream in the gas flow direction, a fan, one or more compressor stages, for example a high-pressure compressor and a low-pressure compressor, a combustion chamber, one or more turbine stages, for example a high-pressure turbine and a low-pressure turbine, and a gas exhaust nozzle. 
         [0003]      FIG. 1  illustrates a longitudinal section view of a combustion chamber  1  according to the prior art. 
         [0004]    The combustion chamber  1  is connected upstream to a compressor (not shown) which supplies the combustion chamber  1  with air under pressure through a diffuser (not shown), and downstream to a distributor  2 . 
         [0005]    The combustion chamber  1  is delimited by an annular outer casing  3  extending along a longitudinal axis  5 . The outer casing  3  is attached to an outer shell of the turbine engine (not shown). 
         [0006]    The combustion chamber  1  comprises a “flame tube” or “fireplace recess”  7  which is the seat of gas combustion. 
         [0007]    The flame tube  7  is surrounded by an annular air supply conduit which is separated from the flame tube  7  by a wall  8  with a toroidal shape overall. 
         [0008]    In the example illustrated in  FIG. 1 , the flame tube  7  is a “reverse flow” type, and the wall  8  has a bent annular shape allowing the gas flow to be directed downstream in the turbine engine, in the direction of the turbine. The gas flow then occurs in succession from downstream to upstream, then again downstream of the combustion chamber  1 . The injectors are generally arranged at the head of the flame tube  7 . 
         [0009]    The flame tube  7  is connected to the combustion chamber  1  by attachment pins  9  each extending radially in a through insertion port  10  provided in the outer casing  3 , and in a through reception port  11  provided in the wall  8  of the flame tube  7  facing the insertion port  10 . These attachment pins  9  make it possible to hold the flame tube  7  within the combustion chamber  1 . 
         [0010]    The reception ports  11  are each provided with a boss  12  having a tubular body  13  inside which the associated attachment pin  9  is slidably mounted so that, when the flame tube  7  expands due to the heat caused by the combustion of the gases, the body  13  of the boss  12  slides along the attachment pin  9 . Each of the bosses  12  further comprises, at one of its end, an annular collar  14  TIG (tungsten inert gas) butt-welded and sealed to the reception port  11  of the wall  8  of the flame tube  7 . 
         [0011]    The use of such bosses  12  has, however, a certain number of disadvantages. 
         [0012]    In particular, the operation of welding the bosses  12  to the wall  8  of the flame tube  7  generates strong deformations of the bosses  12  and of the wall  8  of the flame tube  7 , making necessary, after the welding operation, sheet metal operations and re-machining of the bodies  13  of the bosses  12 , so as to ensure precise positioning of the flame tube  7  relative to the outer casing  3 . 
         [0013]    Moreover, the annular collar  14  of the bosses  12  is planar overall, and is adapted with difficulty to the contour of the wall  8  of the flame tube  7 , so that the bosses  12  do not allow precise positioning of the flame tube  7  relative to the outer casing  3  to be ensured, without re-machining of the bodies  13  of the bosses  12 . 
         [0014]    In addition, it is compulsory, after the welding operation, the carry out heat treatment and non-destructive testing of the bosses  12  and of the flame tube  7 . 
         [0015]    These supplementary operations considerably complicate the manufacture of the combustion chamber  1  and make it more costly. 
         [0016]    Finally, the friction generated between the bodies  13  of the bosses  12  and the attachment pins  9 , when the flame tube  7  expands due to the heat of gas combustion and the bodies  13  of the bosses  12  slide along the attachment pins  9 , have a tendency to wear out the bosses  12 . 
         [0017]    Worn bosses  12  are replaced during maintenance operations. The worn bosses  12  are for example cut away with lasers, then new bosses  12  are positioned and welded to the reception ports  11  of the wall  8  of the flame tube  7 . It is then again necessary to carry out sheet-metal operations on the flame tube  7  and the new bosses  12 , re-machine the bodies  13  of the new bosses  12 , heat treating and non-destructive testing of the new bosses  12  and of the flame tube  7 . 
         [0018]    The replacement of such bosses  12  is therefore particularly inconvenient and costly. 
       PRESENTATION OF THE INVENTION 
       [0019]    The present invention therefore has as its object to correct the aforementioned disadvantages by proposing an assembly for a combustion chamber comprising a boss and an annular element making it possible to ensure precise positioning of the tube in the combustion chamber while still reducing complexity and manufacturing costs of the combustion chamber. 
         [0020]    More precisely, the present invention has as its object an assembly for a turbine engine combustion chamber, comprising:
       a boss for a turbine engine combustion chamber, comprising a tubular body configured to be inserted into a reception port provided in an annular wall of a flame tube and to accommodate a stem of an attachment pin of the flame tube on an outer casing, a first end of the boss comprising an annular collar configured to block radial translation of the boss in a first direction, and a second end of the boss being configured to be crimped to the wall of the flame tube so as to block radial translation of the boss in a second direction, and   an annular element configured to fit coaxially with the reception port, and in radial contact with the annular wall of the flame tube on the one hand and with the annular collar of the boss on the other hand.       
 
         [0023]    The present invention also has as its object a turbine engine combustion chamber, comprising:
       an annular outer casing extending along a longitudinal axis,   a flame tube arranged inside the outer casing and comprising an annular wall extending generally along the longitudinal axis, the wall comprising at least one reception port arranged facing the outer casing,   at least one attachment pin for the flame tube on the outer casing comprising a stem extending through the reception port,   at least one boss, the boss comprising a tubular body inserted into the reception port, and accommodating the stem of the attachment pin, a first end of the boss comprising an annular collar configured to block a radial translation of the boss in a first direction, and a second end of the boss being crimped to the wall of the flame tube so as to block the radial translation of the boss in a second direction,   at least one annular element ( 39 ) arranged coaxially with the reception port ( 29 ) and in radial contact with the annular wall ( 25 ) of the flame tube ( 24 ) on the one hand and with the annular collar ( 35 ) of the boss ( 32 ) on the other hand.       
 
         [0029]    Preferably, the annular element is welded at one or more points to the wall of the flame tube. 
         [0030]    Preferably, the annular element is arranged against an outer surface of the wall of the flame tube, and the second end is crimped against an inner surface of the flame tube. 
         [0031]    Preferably, the annular element has a contact surface with the wall of the flame tube conforming to the shape of the wall of the flame tube. 
         [0032]    More preferably, the annular element comprises an annular collar forming the contact surface with the wall of the flame tube, the annular collar having a land intended to indicate to an operator the orientation of the contour of the contact surface of the annular element. 
         [0033]    The present invention also has as its object a turbine engine comprising a combustion chamber as previously described. 
         [0034]    The invention also has as its object a method for manufacturing a turbine engine combustion chamber, comprising an annular outer casing extending along a longitudinal axis, and a flame tube arranged inside the outer casing comprising an annular wall extending generally along the longitudinal axis, the method comprising the steps of:
       drilling at least one reception port in the wall of the flame tube facing the outer casing,   installing at least one annular element coaxially with the or one of the reception ports against the wall of the flame tube,   inserting into the reception port(s) and the associated annular element(s) ( 39 ) a boss comprising at a first end an annular collar configured to block radial translation of the boss(es) in a first direction, so that the annular collar ( 35 ) of the boss(es) ( 32 ) bears against the annular element(s) ( 39 ),   crimping the second end of the boss(es) to the wall of the flame tube, so as to block radial translation of the boss(es) in a second direction.       
 
         [0039]    More preferably, the method comprises, after the step of crimping the boss(es), a step of welding at one or more points of the annular element(s) to the wall of the flame tube. 
     
    
     
       PRESENTATION OF THE FIGURES 
         [0040]    Other features, aims and advantages of the invention will be revealed by the description that follows, which is purely illustrative and not limiting, and which must be read with reference to the appended drawings, wherein: 
           [0041]      FIG. 1  (already described) is a longitudinal section view of a combustion chamber according to the prior art; 
           [0042]      FIG. 2  is a longitudinal section view of a combustion chamber according to one embodiment of the invention; 
           [0043]      FIG. 3  is a section view, in detail of a boss of the flame tube of the combustion chamber shown in  FIG. 2 ; 
           [0044]      FIG. 4  is a flowchart of a method for manufacturing a combustion chamber according to one embodiment of the invention; 
           [0045]      FIGS. 5, 6 and 7  each illustrate one step of the manufacturing method shown in  FIG. 4 ; 
           [0046]      FIG. 8  is a flowchart of a method for replacing a boss in a combustion chamber manufactured according to the method shown in  FIG. 4 ; 
           [0047]      FIGS. 9 and 10  each illustrate one step of the method shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION 
       [0048]      FIG. 2  shows a longitudinal section view of a combustion chamber  20  of a turbine engine according to one embodiment of the invention. 
         [0049]    The combustion chamber  20  is connected upstream to a compressor (not shown) which supplies the combustion chamber  20  with air under pressure through a diffuser (not shown), and downstream to a distributor. 
         [0050]    The combustion chamber  20  is delimited by an annular outer casing  21  extending along a longitudinal axis  23 . 
         [0051]    The combustion chamber  20  further comprises a flame tube  24  provided with a wall  25  with a toroidal shape overall extending along the longitudinal axis  23 . The wall  25  is provided at a distance from the outer casing  21  so as to form an annular air supply conduit. 
         [0052]    In the example illustrated in  FIG. 2 , the flame tube  24  is of the reverse flow type and the wall  25  has a bent annular shape making it possible to transmit the gas flow downstream in the turbine engine, in the direction of the turbine. The gas flow then occurs in succession from downstream to upstream, then again downstream from the combustion chamber  20 . The injectors are then generally arranged at the head of the flame tube  24 . 
         [0053]    According to a variant (not shown), the flame tube is of the direct flow type and comprises annular walls of revolution connected at an upstream end by a bottom and a shroud comprising fuel injector passage ports carried by the combustion chamber. 
         [0054]    The combustion chamber  20  comprises an attachment pin  26  configured to connect the wall  25  of the flame tube  24  to the outer casing  21 . 
         [0055]    To this end, the attachment pin  26  comprises a stem  27  extending radially in a through insertion port  28  provided in the outer casing  21 , and in a through reception port  29  provided in the wall  25  of the flame tube  24  facing the insertion port  28 , and a head  30  positioned in abutment against an outer surface  31  of the outer casing  21 . 
         [0056]    The combustion chamber  20  further comprises a boss  32  comprising a tubular body  33  extending in the reception port  29  and accommodating the stem  27  of the attachment pin  26 . The stem  27  is slidably mounted in the body  33  of the boss  32 , so that, when the flame tube  24  expands, the body  33  of the boss  32  slides along the stem  27 . 
         [0057]    The boss  32  is for example made of nickel, of cobalt or of chromium. 
         [0058]    The boss  32  shown in  FIG. 2  is shown in detail in  FIG. 3 , prior to the installation of the stem  27  of the attachment pin  26  in the boss  32 . 
         [0059]    Preferably, an outer diameter D 1  of the body  33  of the boss  32  is substantially equal to a diameter of the reception port  29  associated with it. 
         [0060]    A first open end  34  of the boss  32  is formed by an annular collar  35  configured to block radial translation of the boss relative to the longitudinal axis  23  in a first direction A, when the boss  32  is inserted into the associated reception port  29 . As illustrated in  FIG. 3 , an outer surface of the body  33  of the boss  32  is for example connected to the annular collar  35  by a fillet, and an inner surface of the body  33  of the boss  32  is for example connected to the collar  35  by a flare. 
         [0061]    In the example illustrated in  FIGS. 2 and 3 , the annular collar  35  of the boss  32  is arranged facing an outer surface  36  of the wall  25  of the flame tube  24 . Thus the annular collar  35  blocks radial translation of the boss  32  toward the interior of the flame tube  24 . 
         [0062]    The boss  32  also comprises, positioned opposite the annular collar  35 , a second end  37  crimped to the wall  25  of the flame tube  24 , so as to block radial translation of the boss in a second direction B, opposite to the first direction A. The second end  37  is preferably crimped to the wall  25  of the flame tub  24  over its entire circumference. 
         [0063]    In the example illustrated in  FIG. 2 , the second end  37  of the boss  32  is crimped against an inner surface  38  of the flame tube  24 . Thus, the crimping  37  of the boss  32  blocks radial translation of the boss  32  toward the outside of the flame tube  24 . 
         [0064]    Preferably, when it is crimped to the wall  25  of the flame tube  24 , the second end  37  of the boss conforms to the shape of the wall  25  of the flame tube  24 . In the example shown in  FIG. 3 , the second end  37  of the boss  32  is contoured so as to mold itself to the concavity of the inner surface  38  of the wall  25  of the flame tube  24 . The boss  32  thus mounted in the reception port  29  of the wall  25  of the flame tube  24  makes it possible to ensure precise positioning of the flame tube  24  relative to the outer casing  21  without it being necessary to weld it to the wall  25  of the flame tube  24 . 
         [0065]    The combustion chamber  20  further comprises an annular element  39  arranged coaxially with the associated reception port  29 , in radial contact relative to the longitudinal axis  23  with the wall  25  of the flame tube  24  on the one hand, and with the annular collar  35  of the boss  32  on the other hand. 
         [0066]    Thus, the annular element  39  makes it possible on the one hand to protect the wall  25  of the flame tube  24  from the forces exerted on the boss  32  during its assembly, and on the other hand facilitates the crimping of the second end  37  of the boss  32  to the wall  25  of the flame tube  24 . 
         [0067]    The annular element  39  is for example made of nickel, of cobalt or of chromium. 
         [0068]    In the example shown in  FIGS. 2 and 3 , the annular element  39  is arranged against the outer surface  36  of the wall  25  of the flame tube  24 . 
         [0069]    The annular element  39  has a contact surface  40  with the wall  25  of the flame tube  24 . Preferably, the contact surface  40  conforms to the shape of the wall  25  of the flame tube  24 . In the example presented in  FIG. 3 , the contact surface  40  has a slight concavity so as to mold itself to the convexity of the outer surface  36  of the wall  25  of the flame tube  24 . 
         [0070]    According to one embodiment of the invention, the annular element  39  comprises an annular collar forming the contact surface  40 . The annular collar of the annular element  39  has for example a land intended to indicate to an operator the orientation of the contour of the contact surface  40  of the annular element  39 . In this manner, the annular element  39  can be correctly positioned on the wall  25  of the flame tube  24 . 
         [0071]    The annular element  39  also has an abutment surface  41  against which the annular collar  35  of the boss  32  is in abutment, thus blocking radial displacement of the boss  32  in the first direction A. 
         [0072]    The annular element  39  advantageously has a lateral inner surface configured to mold itself to a lateral outer surface of the body  33  of the boss  32 . For this purpose, an inner diameter of the annular element  39  is substantially equal to the outer diameter D 1  of the body  33  of the boss  32 . As illustrated in  FIG. 3 , the annular element  39  can also have a chamfer between the abutment surface  41  and the lateral inner surface, to face the fillet connecting the lateral outer surface of the body  33  of the boss  32  to the annular collar  35  and thus avoid the risk of interference between the outer surface of the body  33  of the boss  32  and the annular element  39 . 
         [0073]    The annular element  39  is for example welded to one or more points on the wall  25  of the flame tube  24  so as to maintain the exact position of the boss  32 . Such an embodiment is particularly advantageous in the event of replacement of the boss  32  as explained below in the description. 
         [0074]    The combustion chamber  20  advantageously comprises several attachment pins  26  to which are associated insertion ports  28 , reception ports  29 , bosses  32  and annular elements  39  as previously described. Preferably, the attachment pins  26  are arranged in a plane P normal to the longitudinal axis  23 . The attachment pins  26  are advantageously distributed equidistantly in the plane P around the flame tube  24 . 
         [0075]    The manufacture  100  of the combustion chamber  20  takes place according to the following steps illustrated in  FIG. 4 . 
         [0076]    During a first step  101 , the reception port  29  is drilled in the wall  25  of the flame tube  24  facing the outer casing  20 . The first step  101  is for example illustrated in  FIG. 5 . 
         [0077]    Then, during a second step  102 , the annular element  39  is positioned against the wall  25  of the flame tube  24 , coaxially with the reception port  29 . 
         [0078]    The boss  32  is then inserted into the annular element  39  and the reception port  29 , during a third step  103 . The boss  32  is inserted by the second end  37 , so that the annular collar  35  bears against the abutment surface  41  of the annular element  39  and thus blocks radial translation of the boss  32  in the first direction A. The third step  103  is for example illustrated in  FIG. 6 . In this example, the annular element  39  is positioned against the outer surface  25  of the wall  25  of the flame tube  24  and the boss  32  is inserted into the reception port  29  from the outside of the flame tube  24 , so that the annular collar  35  blocks radial translation of the boss  32  toward the inside of the flame tube  24 . 
         [0079]    Then, during a fourth step  104 , the second end  37  of the boss  32  is crimped to the wall  25  of the flame tube  24 , so as to block radial translation of the boss  32  in the second direction B. The fourth step  104  is for example illustrated in  FIG. 7 . In this example, the second end  37  of the boss  32  is crimped against the inner surface  38  of the wall  25  of the flame tube  24 , so that the crimping  37  blocks radial translation of the boss  32  toward the outside of the flame tube  24 . 
         [0080]    Once the boss  32  is installed and crimped to the wall  25  of the flame tube  24 , the annular element  39  is for example welded at one or more points to the wall  25  of the flame tube  24  during a fifth step  105 . In the example illustrated in  FIGS. 5 to 7 , the annular element  39  is welded to the outer surface  36  of the wall  25  of the flame tube  24 . 
         [0081]    Independently of steps  101  to  105 , the insertion port  28  is drilled into the outer casing  20  during a sixth step  106 , so that the insertion port  28  and the reception port  29  are facing one another. What is meant by “independently of steps  101  to  105 ” is the fact that the sixth step  106  can just as well be carried out before, in parallel with or even after steps  101  to  104 . 
         [0082]    Finally, during a seventh step  107 , the flame tube  24  is positioned inside the outer casing  21  and the stem  27  of the attachment pin  26  is inserted first into the insertion port  28 , then into the reception port  29  and the boss  32 , until the head  30  bears against the outer surface  31  of the outer casing  21 , thus ensuring precise positioning of the flame tube  24  in the combustion chamber  20 . 
         [0083]    Steps  101  to  107  are for example carried out several times or in parallel so as to position the flame tube  24  by means of several attachment pins  26 , each associated with an insertion port  28 , with a reception port  29 , with a boss  32  and with an annular element  39  in the manner previously described. Preferably, the reception ports  29  are drilled in a plane P normal to the longitudinal axis  23 . The reception ports  29  are advantageously distributed equidistantly in the plane P around the flame tube  24 . 
         [0084]    The replacement  200  of a worn boss  32  previously mounted on the wall  25  of the flame tube  24  according to steps  102  to  104 , previously described, occurs according to the following steps illustrated in  FIG. 8 . 
         [0085]    During a first step  201 , the attachment pin  26  is removed from the insertion port  28 , from the reception port  29  and from the boss  32 . 
         [0086]    Then the annular collar  35  of the boss  32  is removed during a second step  202 , so that the boss  32  is free to translate in the first direction A. The annular collar  35  of the boss  32  is for example machined by milling or grinding. The second step  202  is for example illustrated in  FIG. 9 . In this example, the boss  32  is free to translate toward the inside of the flame tube  24 . 
         [0087]    The boss  32  is then removed from the annular element  39  and from the reception port  29  in the first direction A, during a third step  203 . The third step  203  is for example illustrated in  FIG. 10 . In this example, the boss  32  is removed from the annular element  39  and from the reception port  29  toward the inside of the flame tube  24 . 
         [0088]    It is therefore not necessary to replace the annular element  39  when the associated boss  32  is worn. It is then understood that it is particularly advantageous, during manufacture of the combustion chamber  20 , to weld at one or more points the annular element  39  to the wall  25  of the flame tube  24 , once the boss  32  is crimped, so as to retain the proper positioning of the flame tub  24  relative to the outer casing  21  despite the replacement of the boss  32 . 
         [0089]    Finally, a new boss  32  is mounted to the wall  25  of the flame tube  24  in conformity with steps  103  and  104 , previously described, and the associated attachment pin  26  is re-inserted into the outer casing  21  and the boss  32  in conformity with step  107  previously described. 
         [0090]    The combustion chamber  20  described earlier thus has the advantage of comprising bosses  32  which are easily mounted and dismounted, at a lower cost, which still ensuring precise positioning of the flame tube  24  in the combustion chamber  20 .