Patent Publication Number: US-2018045413-A1

Title: Combustion chamber of a turbine engine comprising a through-part with an opening

Description:
TECHNICAL FIELD 
     The present invention relates to the field of turbine engines, and more particularly to the general field of combustion chambers of turbine engines. 
     The invention applies to any type of land or aeronautical turbine engines, and especially to the aircraft turbine engines such as turbojets and turboprop engines. 
     It more precisely relates to a combustion chamber of a turbine engine comprising a wall fitted with a through-part in the combustion chamber which comprises an opening to create an air flow for cooling the wall, as well as a turbine engine comprising a compressor and such a chamber. 
     STATE OF PRIOR ART 
       FIG. 1  illustrates a typical example of a turbine engine  10  of a known type, for example an aircraft twin-spool turbofan engine. 
     The turbine engine  10  comprises, successively along the thrust direction depicted by the arrow F which also corresponds to the general flowing direction of gases in the turbojet engine, a low pressure compressor  11 , a high pressure compressor  12 , an annular combustion chamber  1 , a high pressure turbine  13  and a low pressure turbine  14 . 
     In a well-known manner, a combustion chamber  1  is mounted downstream of the high pressure compressor  12  intended to supply this chamber with pressurised air, and upstream of the high pressure turbine  13  intended to rotate the high pressure compressor  12  under the thrust effect of gases coming from the combustion chamber. 
       FIG. 2  illustrates on a large scale a combustion chamber  1  and its immediate surrounding. 
     The combustion chamber  1  comprises two respectively radially inner  2  and radially outer  3  coaxial annular walls, which extend about the longitudinal axis T of the combustion chamber  1 . 
     These two annular walls  2  and  3  are fastened downstream to inner  5  and outer  6  casings of the chamber  1 , and are connected to each other at their upstream end by a chamber bottom annular wall  4 . 
     The chamber bottom annular wall  4  comprises an annular row of apertures evenly distributed about the axis T of the combustion chamber  1 , and in which are mounted injection systems  7  associated with an annular row of fuel injectors  8  each having a fuel emitting axis  9 . 
     Each injection system  7  comprises apertures intended for injecting, in the combustion chamber  1 , a portion of the air flow coming from the diffuser (not represented) mounted at the outlet of the high pressure compressor  12  of the turbine engine  10 . 
     Besides, the annular walls  2  and  3  of the combustion chamber  1  are connected at their upstream end to an annular fairing  17  comprising apertures aligned with the injection systems  7  for passing injectors  8  and air supplying the injection systems  7 . The main functions of this fairing  17  is to protect the chamber bottom wall  4  and to guide portions  18  and  19  of the air flow coming from the diffuser which travel downstream respectively along the inner  2  and outer  3  annular walls of the combustion chamber  1 , within two respectively inner  20  and outer  21  bypass spaces. These portions  18  and  19  of the air flow are respectively referred to as “inner bypass air flow” and “outer bypass air flow”. The inner  20  and outer  21  bypass spaces form, with an upstream space  22  which connects one to the other, an enclosure in which the combustion chamber  1  extends. 
     Furthermore, the radially outer annular wall  3  comprises an aperture  30  for enabling a plug to pass therethrough, having an axis  27 , and fitted with a cooling bushing  28  in which a spark plug  29  extends, mounted on the outer casing  6  and intended to initiate the combustion of the air and fuel mixture at the turbine engine start. As an alternative, the plug aperture  30  could also be located on the chamber bottom wall  4  or on the radially inner annular wall  2 . 
     The inner temperature of the combustion chamber  1  is such that it is often necessary to create a cooling air film between the flame and the radially outer wall  3  of the chamber in order to significantly increase its lifetime. 
     To do so, the inner surface  3   a  of the radially outer wall  3  can be provided with longitudinal tongues  31   a ,  31   b  enabling an air film to be generated, as shown in  FIG. 3  which is a partial perspective view of the inside of a combustion chamber  1  such as the one of  FIGS. 1 and 2 . 
     However, in some cases, obstacles such as the cooling bushing  28  of the spark plug  29  represented in  FIGS. 2 and 3 , may suddenly cut off this protecting air film. Then, the temperature downstream of the cooling bushing  28  is no longer homogeneous and the cooling bushing  28  generates a hot wake  32  within the outer bypass air flow  19 , as illustrated in  FIG. 4 . 
     Of course, other types of elements penetrating in the combustion chamber  1 , other than a cooling bushing, can be obstacles to the flow of the protecting air film, such as for example fastening axes or starting injectors. 
     The wake  32  can then cause considerable temperature gradients, in the order of several hundreds of Celsius degrees, on a very short distance, in the order of a few millimetres. This can then result in a reduction of the lifetime of the radially outer wall  3 . 
     This wake  32  develops downstream by being centred with respect to a medium axial plane P of the plug aperture  30 , in the case where the air flow coming from the diffuser provided by the high pressure compressor  12  flows downstream substantially with no spinning component. 
     On the contrary, in the case where the air flow provided by the high pressure compressor  12  flows downstream in a helical pattern, that is with a spinning component, the wake  32  develops downstream generally along a tilted direction with respect to the medium axial plane P of the plug aperture  30 . 
     It is to be noted that “axial plane” is meant to signify a plane passing through the axis T (see  FIG. 2 ) of the combustion chamber  1 , which merges with the turbine engine axis. It is to be noted that the plane P corresponds to the section plane of  FIG. 2 . 
     In any cases, the wake  32  results in a depression in the region of the outer bypass air flow  19  covered by the cooling bushing  28  of the plug. 
     Given the presence of such a wake  32  on the radially outer wall  3 , it is necessary to locally cool the area downstream of the cooling bushing  28  by reconstructing an air film. 
     Solutions have been suggested aiming, in some configurations, at adding a multitude of micro-perforations  33  (multi-drill) aiming at cooling the downstream area of the cooling bushing  28 . In the example of  FIG. 4 , these micro-perforations  33  are substantially distributed across the surface of the radially outer wall  3  and are intended to create a cooling air film along this wall  3  within the combustion chamber  1 . For the sake of clarity, these micro-perforations  33  are represented larger and distributed according to a lesser density than in reality. 
     Nevertheless, the addition of such micro-perforations  33  dictates additional operations to be performed during manufacture. Moreover, the air film reconstructed through micro-perforations  33  does not have the same streamline flow as an air film generated using longitudinal tongues  31   a ,  31   b.    
     DISCLOSURE OF THE INVENTION 
     There is therefore a need to provide an alternative solution for cooling a wall of a turbine engine combustion chamber in order to increase its lifetime, reducing at best the temperature gradients and the local hot points. 
     The purpose of the invention is to overcome at least partially the above-mentioned needs and the drawbacks related to prior art implementations. 
     The purpose of the invention is thus, according to one of the aspects thereof, a combustion chamber of a turbine engine, comprising at least one wall, especially an annular or toroidal wall, defining the combustion chamber and comprising an aperture for enabling a through-part to pass in the combustion chamber, characterised in that the through-part comprises, in the portion thereof located within the combustion chamber, at least one opening able to create an air film for cooling the area downstream of the through-part. 
     The invention makes it possible to enable an efficient cooling of the wall of the combustion chamber of the turbine engine by creating an air film downstream of the through-part. This way, it can also be possible to limit the appearance of hot wakes on the wall of the combustion chamber downstream of the through-part. Thus, the invention can enable the lifetime of the combustion chamber to be significantly increased. Moreover, the invention can be implemented in a simple way, avoiding the addition of additional operations and/or components on the combustion chamber. The air film can indeed be recreated simply by adding an opening on the through-part with a low added value. Furthermore, the solution of the invention can make it possible to recreate an air film substantially equivalent in terms of streamline flow to the air film generated by the tongue(s) such as previously described. 
     The combustion chamber according to the invention can further include one or more of the following characteristics taken individually or according to any possible technical combinations. 
     Said at least one opening of the through-part can be made for example by machining. 
     Preferably, said at least one opening of the through-part corresponds to a slot made on the surface of the through-part, especially of an oblong shape. 
     Furthermore, said at least one opening of the through-part can extend longitudinally along the annular edge of the through-part, especially over at least one quarter of the annular edge of the through-part. 
     Said at least one opening of the through-part can be substantially formed at the radially inner end of the through-part. 
     Besides, said at least one opening of the through-part can extend substantially parallel to the direction of the cooling air flow supplying it. 
     Said at least one wall can comprise the radially outer annular wall of the combustion chamber. Said at least one wall can yet comprise the radially inner annular wall of the combustion chamber. Said at least one wall can also comprise the chamber bottom annular wall. 
     Besides, the inner surface of said at least one wall can comprise at least one tongue able to generate an air film for cooling said at least one wall, and especially two tongues extending substantially parallel to each other, the through-part being located between both tongues. 
     Moreover, said at least one wall can comprise a plurality of micro-perforations to enable an inlet of cooling air in the combustion chamber for cooling said at least one wall. 
     The through-part can be any type of element penetrating the combustion chamber and thus constituting an obstacle to the flow of a protective air film. It can especially be a fastening axis or a starting injector. However, preferentially, the through-part is a cooling bushing of a spark plug. 
     Besides, the purpose of the invention is also, according to another of its aspects, a turbine engine, characterised in that it comprises a compressor, especially a high pressure compressor, and a combustion chamber such as previously defined, disposed into an annular enclosure arranged at the outlet of the compressor, and in which a portion of an air flow coming from the compressor is intended to bypass the combustion chamber along said at least one wall. 
     The combustion chamber and the turbine engine according to the invention can comprise any of the previously stated characteristics, taken individually or according to any technically possible combinations with other characteristics. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be better understood upon reading the following detailed description of a non-limiting implementation example thereof, as well as upon studying the schematic partial figures of the accompanying drawing, in which: 
         FIG. 1  is an axial cross-section view, of a turbine engine of a known type, 
         FIG. 2  is an axial cross-section half view, of an annular combustion chamber of the turbine engine of  FIG. 1 , 
         FIG. 3  is a partial perspective view of the inside of a combustion chamber such as the one represented in  FIGS. 1 and 2 , 
         FIG. 4  is a top view of a radially outer annular wall of the combustion chamber of  FIG. 2 , 
         FIG. 5  is a partial cross-section half view of an annular combustion chamber of the turbine engine according to an exemplary implementation of the invention, the cooling bushing being represented in a cross-section, 
         FIG. 6  is an another perspective cross-section view of the annular combustion chamber of  FIG. 5 , the cooling bushing being represented in a perspective cross-section view, the plug being not represented, and 
         FIG. 7  represents an isolated perspective view of the cooling bushing located between the radially outer wall and the chamber bottom wall of the combustion chamber of  FIGS. 5 and 6 . 
     
    
    
     Throughout these figures, identical references may refer to identical or analogous elements. 
     Moreover, the different parts represented in the figures are not necessarily drawn to a uniform scale, in order to make the figures more understandable. 
     DETAILED DISCLOSURE OF A PARTICULAR EMBODIMENT 
     Throughout the description, it is to be noted that the terms upstream and downstream are to be considered relative to a main direction F of normal flow of gases (from upstream to downstream) for a turbine engine  10 . Besides, the axis T of the turbine engine  10  is referred to as the axis of radial symmetry of the turbine engine  10 . The axial direction of the turbine engine  10  corresponds to the direction of the axis T of the turbine engine  10 . A radial direction of the turbine engine  10  is a direction perpendicular to the axis T of the turbine engine  10 . Furthermore, unless otherwise specified, the adjectives and adverbs axial, radial, axially and radially are used in reference to the above-mentioned axial and radial directions. Moreover, unless otherwise specified, the terms inside and outside are used in reference to a radial direction so that the inside portion of an element is closer to the axis T of the turbine engine  10  than the outside portion of the same element. 
     Moreover, in the following description, it is considered that the through-part  28  is a cooling bushing  28  of a spark plug  29 . This choice is of course in no way limiting, since the through-part  28  can be any element penetrating the combustion chamber  1  and constituting an obstacle to the flow of a protecting air film, such as a fastening axis or a starting injector. 
     Furthermore, the wall  3  defining the combustion chamber  1  and comprising an aperture  30  for enabling the through-part  28  to pass therethrough preferentially consists in the radially outer annular wall  3  of the combustion chamber  1 . However, this wall can also consist in the chamber bottom annular wall  4  or the radially inner annular wall  2  of the combustion chamber  1 . 
       FIGS. 1 to 4  have already been previously described in the portion related to the state of prior art. 
     With reference to  FIGS. 5 to 7 , an exemplary embodiment of a combustion chamber  1  in accordance with the invention is beside illustrated. 
     More precisely,  FIGS. 5 and 6  are perspective views of the radially outer annular wall  3  and of the chamber bottom wall  4  of the combustion chamber  1  of the turbine engine, the cooling bushing  28  of the plug  29  being respectively represented in a cross-section and perspective view. Moreover,  FIG. 7  represents, in an isolated perspective view, this cooling bushing  28 . 
     The combustion chamber  1  is similar to the one previously described with reference to  FIGS. 1 to 4 , the cooling bushing  28  being nevertheless modified according to the invention in order to improve the cooling efficiency of the chamber bottom annular wall  4 , as shown in  FIGS. 5 and 6 , whereas the improvement concerned the cooling efficiency of the radially outer annular wall  3  for the example of  FIG. 2 . 
     Thus, the radially outer annular wall  3  of the combustion chamber  1  comprises an aperture  30  enabling the cooling bushing  28  of the spark plug  29  to pass therethrough. 
     According to the invention, the cooling bushing  28  comprises, in the portion thereof located inside the combustion chamber  1 , an opening  34  able to create an air film for cooling the area downstream of the cooling bushing  28 . 
     As can be seen in  FIGS. 5 to 7 , this opening  34  has the form of an oblong shaped slot, machined on the surface of the cooling bushing  28  at the radially inner end  28   a  thereof. 
     This slot  34  makes it possible to create an air film downstream of the cooling bushing  28  and of the spark plug  29 , so as to prevent, or at least to limit, hot wakes such as previously described from being formed, and therefore to be able to increase the lifetime of the combustion chamber  1 . 
     Besides, as can be seen in  FIGS. 5 and 6 , the slot  34  of the cooling bushing  28  extends longitudinally along the annular edge of the cooling bushing  28 , over at least one quarter of the same. Moreover, this slot  34  extends substantially parallel to the direction of the cooling air flow supplying it. 
     Furthermore, as represented in  FIGS. 5 and 6 , the inner surface of the radially outer wall  3  and the inner surface of the chamber bottom  4  respectively comprise a longitudinal tongue  31   b  and  31   a , parallel to each other and between which the cooling bushing  28  of the spark plug  29  is located. 
     Of course, the invention is not limited to the exemplary embodiment which has just been described. Various modifications can be brought by those skilled in the art. 
     In particular, generally and as previously indicated, the invention can also be applied to a radially inner annular wall or a combustion chamber bottom annular wall when such a wall is passed through by a spark plug or any other element penetrating a combustion chamber. 
     The term “comprising a/an” must be understood as being synonymous with “comprising at least one”, unless otherwise specified.