Patent Publication Number: US-2023151768-A1

Title: Combustion assembly

Description:
TECHNICAL FIELD 
     The present disclosure relates to a combustion assembly for a turbomachine. 
     PRIOR ART 
     A turbomachine conventionally includes, from upstream to downstream in the direction of gas circulation within the turbomachine, a fan, one or more compressor stages, for example a low-pressure compressor and a high-pressure compressor, a chamber combustion, one or more turbine stages, for example a high pressure turbine and a low pressure turbine, and a gas exhaust nozzle. 
     The combustion chamber is delimited by internal and external revolution casings which are coaxial and connected upstream to a chamber bottom annular casing. The outer casing of the chamber is fastened on an outer envelope of the turbomachine, the inner casing of the chamber being fastened on an inner envelope or connected to the outer casing. 
     The combustion chamber moreover comprises a flame tube or hearth, which is the seat of the combustion of the gases. 
     The fuel supply of the flame tube is carried out by a plurality of fuel injection devices which open into the flame tube. Each injection device comprises a fuel flow rate limiter which allows, due to its shape, controlling the fuel flow rate supplying downstream a fuel injector, one downstream end of which opens into the flame tube. 
     Conventionally, the fuel flow rate injector and the fuel flow rate limiter are made independently due to their complex three-dimensional conformation. However, the dissociation of the manufacture of the part carrying out the supply of the injector which in turn carries out the mixture of the fuel with the air for its spraying in the room does not make optimal the placement of the limiter relative to the injector such that an impact may result in the fuel spraying into the flame tube. 
     SUMMARY 
     The present disclosure thus relates to a combustion assembly for a gas turbine comprising a flame tube and fuel supply means including a flow rate limiter supplying an injector, characterised in that the flow rate limiter and the fuel injector are formed in one piece. 
     This embodiment allows guaranteeing an optimal placement of the fuel spray injector relative to the flow rate limiter so as to have an optimal combustion in the flame tube. The flow rate limiter and the fuel injector are advantageously manufactured by additive manufacturing which may be of the laser powder fusion type. 
     The flow rate limiter may comprise a first fuel conduit and a second fuel conduit each comprising a succession of chambers which are interconnected by reduced section portions, the first conduit and the second conduit being connected to a fuel inlet, the first conduit opening downstream into a first channel of the fuel injector and the second conduit opening downstream into a second channel of the injector. 
     The series arrangement of the chambers allows obtaining a better flow rate metering accuracy only if a single hole is made with the same production tool by statistical dispersion effect. This is particularly true for the injectors made by additive manufacturing, whose manufacturing tolerances on isolated orifices are not compatible with those of a fuel metering. Thus, by multiplying the chambers and the reduced section portions in series, it is possible to average the shape defects resulting from an additive manufacturing, which allows obtaining the desired final accuracy which can be all the better, the greater the number of chambers and reduced section portion of orifices in series is. 
     The first conduit and the second conduit can extend in one plane and more particularly in the same plane. This arrangement called “flat” arrangement allows an integration of the first and second conduits into an already existing flange for fastening the injector, without addition of space requirement and weight. 
     The fuel injector may have a substantially L-shape, a first branch of which includes the first channel including an upstream end which is connected to the first conduit of the flow rate limiter and a downstream end which opens into a first fuel outlet end piece, and a second branch of which includes a second fuel outlet end piece which is connected to a downstream end of a second channel which extends in the first branch and in the second branch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features, details and advantages will appear on reading the detailed description below, and on analysing the appended drawings, in which: 
         FIG.  1    is a schematic perspective view of a combustion assembly according to the invention. 
         FIG.  2    is a schematic perspective representation of fuel supply means according to the invention; 
         FIG.  3    is a schematic perspective representation with a cut-out of the part of  FIG.  2   ; 
         FIG.  4    is a schematic sectional view of the fuel injector. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The drawings and the description below contain, essentially, elements of a certain character. They may therefore not only be used to better understand this disclosure, but also contribute to its definition, where appropriate. 
       FIG.  1    represents a casing  10  and a combustion assembly  12  according to the present disclosure which is supported by the casing  10 . As shown in  FIG.  1   , the combustion assembly  12  comprises a flame tube  14  inside which fuel supply means open. The flame tube  14  comprises an inner annular shroud (not visible) and an outer annular shroud  16 . These fuel supply means comprise a flow rate limiter  18  supplying fuel to a fuel injector  19 . More specifically, the flow rate limiter  18  comprises a base  20  or a radially outer plate which is fastened on the outer face of a boss  22  of the casing  10  in order to ensure a positioning reference of the flow rate limiter  18  on the casing  10 . The fuel injector  19  has a substantially L-shape formed by a first branch  19   a  and a second branch  19   b  which are connected to each other. 
     As shown in  FIGS.  2  to  4   , the injector  19  which is herein a fuel pre-vaporisation pipe therefore comprises a first branch  19   a  inside which a first channel  24  of flow of an air/fuel mixture, which exits at the downstream end of the first channel  24  via a first end piece  26 , is formed. A second channel  28  extends into the first branch  19   a  and into the second branch  19   b  and opens at the downstream end thereof into a second end piece  30 . The first channel  24  is supplied with fuel by a first conduit  32  of the flow rate limiter and the second channel  28  is supplied with fuel by a second channel  34  of the flow rate limiter  18 . 
     The flow rate limiter  18  thus comprises the first fuel conduit  32  and the second fuel conduit  34  which are separate from each other. These two fuel conduits  32 ,  34  are supplied by a common fuel source, but comprise distinct fuel outlets. The first conduit  32  opens at the outlet facing the upstream end of the first channel  24  of the injector  19 . The second conduit  28  opens at the outlet facing the upstream end of the second channel  28  of the injector  19 . The first conduit  32  and the second conduit  34  each comprise a succession of chambers interconnected by reduced section portions. 
     As shown in  FIG.  3   , the first conduit  32  and the second conduit  34  extend in one plane and in the example represented in the same plane. This arrangement called “flat” arrangement allows an integration of the first  32  and second  34  conduits into an already existing flange for fastening the injector, without addition of space requirement and weight. 
     As shown in  FIG.  1    and in  FIG.  2   , an air inlet  36  is provided at the junction of the fuel injector  19  and the fuel limiter  18 . This air inlet  36  is arranged in the annular space formed between the casing  10  and the outer shroud  16 . 
     According to the present disclosure, the injector  19  and the limiter  18  are manufactured in one piece, for example by additive manufacturing. In particular, it is possible to consider manufacturing this part by laser powder fusion.