Patent Publication Number: US-9410703-B2

Title: Device for injecting a mixture of air and fuel into a turbine engine combustion chamber

Description:
The present invention relates to a device for injecting a mixture of air and fuel into a combustion chamber of a turbine engine such as an airplane turbojet or turboprop. 
     An injection device of this type has centering means for centering a fuel injector, which means are movable radially in support means that are fastened to a wall of the chamber in order to absorb differential thermal expansion between the various parts in operation. 
     An injection device may comprise various elements, including: a centering ring for centering the head of a fuel injector, at least one radial or axial swirler, a Venturi, a bowl pierced by orifices for passing air, and a sheath for mounting and supporting the device, the sheath being fastened in an orifice in the end wall of the chamber by brazing. 
     There are two different technologies for mounting this type of injection device. In the first, the centering ring has an outer radial rim slidably mounted in an annular groove of support means that may then comprise a swirler, a Venturi, a bowl, and a sheath of the above-mentioned type. The annular groove for radial movement of the ring is defined in this technology by an upstream radial wall of the swirler and by an upstream washer that is fitted to the swirler and fastened thereto. 
     In a second technology, the ring, the swirler, the Venturi, and the bowl form a single-piece unit that has an outer radial rim slidably mounted in an annular groove of the sheath that forms the above-mentioned support means. The annular groove for radial movement of the centering means in this technology is defined by an upstream radial wall of the sheath and by an upstream washer fitted to the sheath and fastened thereto. 
     In both of the above-mentioned technologies, the axial retaining means for axially retaining the centering means relative to the support means in an upstream direction, i.e. away from the chamber, are formed by the above-mentioned washer that is fitted to the support means and that is fastened thereto by weld beads. 
     The washer is thus fastened to the support means in non-releasable manner. Should it be necessary to replace all or some of the centering means of an injection device during a maintenance operation, it is necessary to destroy the washer, which constitutes an operation that is difficult since there must be no damage to the sheath, which is brazed to the chamber wall. Furthermore, breaks have already been observed in such weld beads, and that is not acceptable. 
     A particular object of the present invention is to provide a simple, effective, and inexpensive solution to the problems of the prior technologies. 
     To this end, the invention provides a device for injecting a mixture of air and fuel into a turbine engine combustion chamber, the device comprising centering means for centering a fuel injector, which means are movable radially in support means for fastening to a wall of the chamber, the support means carrying retaining means for axially retaining the centering means on a side opposite from the chamber wall, the retaining means are fastened in releasable manner to the support means, the device being characterized in that the retaining means comprise at least one peg carried by the support means, a latch engaged on the peg and holding the centering means against the support means, and a pin having one end portion engaged and prevented from moving in a housing of the peg and having an opposite end portion bearing against the latch to prevent it from moving relative to the peg. 
     The centering means of the injection device can thus easily be released from the support means, e.g. during a maintenance operation. There is no longer any risk of breaking weld beads fastening the retaining means that retain the centering means since such weld beads are eliminated in the invention, which has the advantage of being suitable for use in both of the above-described technologies. 
     According to another characteristic of the invention, the support means comprise at least one radially outer wall or tab for guiding or bearing against the centering means, and the retaining means are releasably fastened to said wall or tab. 
     The support means may comprise two diametrically opposite tabs extending radially outwards. 
     The centering means may also include two radially outer tabs that are diametrically opposite and that are held against the tabs of the support means by the retaining means. The retaining means may pass through orifices or notches in the tabs of the centering means with circumferential and radial clearance so as to allow relative movements in a radial direction and in a circumferential direction between the centering means and the support means. 
     Advantageously, the tabs of the centering means are held against the tabs of the support means by two mutually independent retaining means. Even in the unlikely event of one of the retaining means breaking or failing, the other retaining means can thus hold the centering means in position. Furthermore, the retaining means are situated at a distance from the fuel injector and therefore do not impede mounting it and guiding it in operation. 
     According to the invention, the retaining means comprise at least one peg carried by the support means, a latch engaged on the peg and holding the centering means against the support means, and a pin having an end portion engaged and held stationary in a housing of the peg, with the opposite end portion thereof bearing against the latch in order to prevent it from moving relative to the peg. 
     In order to remove the retaining means, it suffices to deform the pin once more so as to release the latch. The pin is then discarded and needs to be replaced with a new pin. 
     The latch may include a groove into which the end portion of the pin remote from the peg is folded down by plastic deformation. 
     The housing in the peg may be L-shaped and may include a transverse passage receiving one end of the pin and a longitudinal slot connecting the transverse passage to one end of the peg. 
     The axis of elongation of the slot in the peg may be in alignment on the longitudinal axis of the peg. In a variant, the axis of elongation is parallel to and offset from the axis of the peg, thereby serving to create keying means that prevent the latch being wrongly mounted, since the latch can be mounted only in one single position on the peg. 
     Preferably, the peg is engaged in an orifice of the support means and includes an annular shoulder bearing axially against the support means, the shoulder including keying means co-operating by connecting shapes with complementary means of the support means. The peg is correctly positioned when the keying means of the peg co-operate with the complementary means of the support means. 
     The invention also provides a turbine engine combustion chamber and a turbine engine such as an airplane turboprop or turbojet, characterized in that they include at least one injection device as described above. 
    
    
     
       The invention can be better understood and other characteristics, details, and advantages thereof appear more clearly on reading the following description made by way of non-limiting example and with reference to the accompanying drawings, in which: 
         FIG. 1  is a diagrammatic half-view in axial section of a prior art turbine engine device for injecting a mixture of air and fuel; 
         FIG. 2  is a fragmentary diagrammatic half-view in axial section of another prior art turbine engine device for injecting a mixture of air and fuel; 
         FIG. 3  is a diagrammatic perspective view of a turbine engine device of the invention for injecting a mixture of air and fuel; 
         FIG. 4  is a fragmentary diagrammatic view of a combustion chamber end wall carrying a device of the invention, in face view from upstream; 
         FIG. 5  is a fragmentary diagrammatic view of the  FIG. 4  chamber end wall, the wall carrying a sheath of the device of the invention; 
         FIG. 6  is a diagrammatic view in perspective of a shouldered peg of retaining means of the device of the invention; 
         FIGS. 7 and 8  are fragmentary diagrammatic views in perspective of the  FIG. 6  peg mounted on the  FIG. 5  sheath; 
         FIG. 9  is a fragmentary diagrammatic view in perspective and in axial section of the  FIG. 6  peg mounted on the  FIG. 5  device; 
         FIG. 10  is a view corresponding to  FIG. 3  with the retaining means of the device of the invention partially withdrawn; 
         FIG. 11  is a diagrammatic perspective view of a pin of the retaining means of the device of the invention; 
         FIG. 12  is a fragmentary diagrammatic view in perspective of the pin and of the peg of the retaining means of the device of the invention, and it shows a step during the mounting of these means; 
         FIG. 13  is a diagrammatic view in perspective of the latch of the retaining means of the device of the invention; 
         FIGS. 14 and 15  are diagrammatic views in perspective and in axial section of the retaining means of the device of the invention, and they show steps in the mounting of these means; and 
         FIG. 16  is a diagrammatic view in axial section of a variant embodiment of the retaining means of the device of the invention. 
     
    
    
       FIG. 1  shows a device  10  for injecting a mixture of air and fuel into a combustion chamber of a turbine engine such as an airplane turbojet or turboprop, with only an end wall  12  and an upstream annular fairing  14  of the combustion chamber being shown in part. 
     The air fed to the injection device  10  comes from an upstream diffuser (not shown), and the fuel is brought in by an injector fastened to an outer casing (not shown) of the chamber. Each injector has a fuel injection head of axis that is represented diagrammatically by a chain-dotted line  16 , and it is aligned on an axis of an orifice  18  in the chamber end wall  12 . 
     The  FIG. 1  injection device  10  has two coaxial swirlers, respectively an upstream swirler  20  and a downstream swirler  22 , that are separated from each other by a Venturi  24 , and that are connected upstream to means  26  for centering the injector head, and downstream to a mixer bowl  28  that is fastened to a sheath  30  mounted axially in the orifice  18  of the chamber end wall  12 , and brazed thereto. 
     The means for centering the injector head comprise a ring  26  through which the head passes axially and including an annular rim  32  extending radially outwards and slidably mounted in an annular groove. This groove is defined downstream by an upstream radial wall of the upstream swirler  20  and upstream by a washer  34  that is fitted to the upstream end of the swirler  20  and that is fastened by its outer periphery being welded (at A) to an upstream cylindrical rim  36  of the swirler  20 . 
     In the technology shown in  FIG. 1 , the means for centering the device  10  are formed by the ring  26  and its support means are formed by the sheath  30 , the bowl  28 , the swirlers  20 ,  22 , the Venturi  24 , and the washer  34 , the washer  34  forming means for axially retaining the ring  26  in the upstream direction. 
     Reference is now made to  FIG. 2 , which shows another known technology for mounting an injection device  110 , and which differs from that described above in that the centering means in this example comprise an upstream ring (not shown), radial swirlers  120 ,  122 , a Venturi  124 , and a bowl  128 , which are fastened to one another so as to form a one-piece unit. The bowl  128  has an annular rim  132  extending radially outwards and housed in an annular groove of support means that, in this example, comprise a sheath  130  and an upstream washer  134  having its outer periphery fastened by welding (at B) to an upstream cylindrical rim  136  of the sheath. The groove is defined downstream by a radial wall of the sheath  130  and upstream by the washer  134 . 
     As explained above, the two above-described technologies present drawbacks associated with the retaining washers  34  and  134  of the centering means being fastened by weld beads, which weld beads may be weakened and may be in danger of breaking in operation. 
     The invention enables that problem to be remedied by releasable fastening of the centering means on the support means of an injection device, where the releasable fastening does not require welding. 
       FIGS. 3 to 15  show an embodiment of the invention. 
     The injection device  210  of the invention is shown in perspective in  FIG. 3  and in the mounted position in  FIG. 4 . As in the prior technologies, the device  210  may comprise a ring  226  having an injection head passing therethrough, two radial swirlers  220  and  222  that are separated from each other by a Venturi  224 , a bowl (not shown), and a sheath  230  for fastening the device  210  to a chamber end wall  212 . 
     In the example shown, the centering means of the device comprise a ring  226 , the swirlers  220 ,  222 , the Venturi  224 , and the bowl, which together form a one-piece unit. The support means comprise the sheath  230 , which is shown in the mounted position in  FIG. 5 , the sheath  230  being engaged in an orifice  218  of the chamber end wall  212  and being brazed thereto. The device  210  is thus similar to the technology shown in  FIG. 2 . Nevertheless, in a variant, the device  210  could be of the same type as the technology shown in  FIG. 1 . 
     In the invention, the centering means are retained and fastened in releasable manner on the support means. In the example shown, the centering means comprise an outer annular rim  250  carrying two radially outer tabs  252  that are diametrically opposite, which tabs are movable radially and circumferentially over corresponding tabs  254  of the sheath  230 , and are retained and held on those tabs by releasable retaining means  256 . 
     The tabs  254  of the sheath  230  can be seen in  FIG. 5 . These tabs  254  extend radially outwards and they are diametrically opposite about the axis of the sheath  230 , which axis coincides with the axis of the orifice  218  of the wall  212  in which the sheath  230  is mounted. In the mounted position, these tabs  254  extend upstream of the wall  212 , i.e. outside the combustion chamber, and they are both on a common circumference centered on the axis of the combustion chamber. 
     Each tab  254  of the sheath  230  has a through axial orifice  258  for mounting retaining means  256 . 
     The tabs  252  of the centering means can be seen in  FIG. 10 . These tabs  252  have through axial notches  260  in their radially outer ends, each of these notches  260  subdividing the tab into two portions that are to extend on circumferential end regions of the tabs  254  of the sheath, as can be seen in  FIG. 10 . 
     Each retaining means  256  comprises a peg  262  (shown in  FIG. 6 ), a latch  264  (shown in  FIG. 13 ), and a pin  266  (shown in  FIG. 11 ). 
     The peg  262  comprises a cylindrical body carrying an annular shoulder  268  at one end. The body of the peg  262  is hollowed out in part and includes an open through passage  270  substantially in its middle and a longitudinal slot  272  connecting the passage to the end of the peg remote from the shoulder  268 . The passage  270  has a section of circular shape and the slot  272  has a section that is substantially U-shaped. The passage  270  and the slot  272  form a substantially L-shaped housing inside the peg  262 . 
     The peg  262  is mounted in an orifice  258  of a tab  254  of the sheath  230 , as shown in  FIGS. 7 to 9 . The body of the peg  262  passes through this orifice  258 , and the shoulder  268  of the peg comes to bear against a radial face of the tab  254 , which is the downstream radial face of the tab in the example shown ( FIG. 7 ). 
     In the mounted position, the slot  272  in each peg  262  opens radially outwards relative to the axis of the device  210 , i.e. away from the radially opposite retaining means. In order to guarantee that the peg is in this angular position in the orifice  252  of the sheath  230 , the peg  262  includes keying means that co-operate with complementary means of the sheath  230 . In the example shown, the shoulder  268  of the peg includes a flat  274  that is to face an annular rim of the sheath  230  so as to allow the peg to be mounted and to bear against the above-mentioned face of the sheath. In the event of the peg not being correctly angularly positioned in the orifice  252  in the sheath, its shoulder  268  comes into abutment against the above-mentioned rim of the sheath  230  and prevents it from coming to bear against the tab  254 . 
     The peg  262  may be held stationary on the tab  254  by brazing. 
     The pin  266  is generally L-shaped and has two mutually perpendicular rectilinear portions of different lengths. Each portion has a section that is substantially circular in shape, and that is substantially complementary to the shape of the passage  270  and of the bottom of the slot  272  in the peg. By way of example, the portions of the pin present a diameter of about 1.8 millimeters (mm). 
     As can be seen in  FIG. 12 , the shorter portion of the pin  266  is for engaging in the passage  270  of the peg  262 , and its longer portion extends in part inside the slot  272  of the peg. The pin  266  is engaged in the housing of the peg by being moved in translation in a plane containing the axis C of the peg, and substantially in the middle of its slot  272  and its passage  270 , until it comes to bear against the bottom of the slot  272 . In the mounted position, as shown in  FIG. 12 , the axis of the longer portion of the pin  266  coincides with the axis C of the peg. Once deformed, the peg  266  is generally Z-shaped. 
     The latch  264  comprises a substantially rectangular plate having a cylindrical boss  278  on one of its faces, and it is made with a through orifice  280  that extends substantially through the middle of the boss  278  and of the plate. The top end of the boss  278  has a transverse groove  282  connecting the end of the orifice  280  that is situated remote from the plate to the periphery of the boss. 
     The orifice  280  has a top portion and a bottom portion, the top portion having a diameter that is smaller than the diameter of the bottom portion, and these two portions are connected together by a cylindrical shoulder  284 . The bottom portion of the orifice  280  has a section of circular shape complementary to the shape of the body of the peg  262 , and the top portion of the orifice has a section that is circular in shape and complementary to the shape of the pin  266 . The groove  282  in the latch has a section that is C-shaped or U-shaped and that is substantially complementary to the section of a portion of the pin  266 . 
     The latch  264  is engaged on the pin  266  and the peg  262 , as shown in  FIG. 14 , by moving in translation along an axis parallel to the axis C of the pin and of the peg. In the mounted position, the plate of the latch  264  bears against the tab  252  of the centering means, the peg  262  is engaged in the larger-diameter bottom portion of the orifice  280  in the latch, and the pin  266  is engaged in the top portion of the orifice. The end portion of the pin  266  that extends outside the latch  264  is for folding down by plastic deformation until it is received in the groove  282  of the latch  264  ( FIG. 15 ). The step of deforming the pin  266  may be performed by means of a suitable tool. This enables the latch to be held stationary on the peg and serves to terminate mounting the retaining means  256 . The same operation is repeated for the other retaining means  256  of the device  210 . 
       FIG. 16  shows a variant embodiment of the retaining means  256 ′ of the device of the invention, each retaining means including keying means that prevent the latch being wrongly mounted. It is preferable for the deformed portion of the pin  266 ′ to be folded radially outwards, not radially inwards, relative to the axis of the device. The variant shown in  FIG. 16  serves to ensure that mounting is performed in this way because of the fact that the main longitudinal axis D (i.e. the longitudinal axis of the longer portion) of the pin  266 ′ is parallel to and remote from the axis C of the peg  262 ′, when the pin is in the mounted position in the housing in the peg. Since the above-mentioned axis D of the pin is in alignment with the axis of elongation of the slot  272 ′ of the peg, this axis of elongation must be parallel to and spaced apart from the axis C of the peg. Prior to plastic deformation of the pin  266 ′, the free end portion thereof that extends outside the latch is thus not in alignment with the axis C of the peg. The bottom and top portions of the orifice  280 ′ of the latch  264 ′ do not lie on the same axis, as can be seen in  FIG. 16 . The latch  264 ′ can therefore be mounted on the pin  266 ′ and the peg  262 ′ in only one position in which its groove  282 ′ has its end remote from the orifice  280 ′ opening radially outwards. Once deformed, the pin  266 ′ is generally Z-shaped. The above-mentioned keying means prevent the pin adopting a U-shape on being plastically deformed. 
     The device  210  of the invention having the retaining means  256  of  FIGS. 3 to 15  or having the means  256 ′ of  FIG. 16 , may be mounted as follows. 
     The sheath  230  is engaged in an orifice in the chamber end wall  218  and is brazed therein so that its radial tabs  254  are situated on a circumference centered on the axis of the chamber ( FIG. 5 ). A peg  262 ,  262 ′ ( FIG. 6 ) is engaged in the orifice  258  of each tab  254  of the sheath and is positioned in such a manner that its shoulder  268  comes to bear against the downstream radial face of the tabs  254  ( FIGS. 7 to 9 ). The centering means are engaged in the sheath  230  and its tabs  252  are caused to bear axially against the tabs  254  of the sheath, the pegs  262 ,  262 ′ carried by the tabs  254  passing through the notches  260  in the tabs  252  of the centering means ( FIG. 10 ). The pegs  262 ,  262 ′ pass through the notches  260  with radial and circumferential clearance so as to allow the centering means to move relative to the sheath  230  in a plane parallel to the tabs  252 ,  256 . During these movements, the tabs  252  and  254  slide over one another. A pin  266 ,  266 ′ ( FIG. 11 ) is engaged in the housing in each peg ( FIG. 12 ). A latch  264 ,  264 ′ ( FIG. 13 ) is engaged on the pin  266 ,  266 ′, and on the peg  262 ,  262 ′ carried by each tab  254 , until it comes to bear against the corresponding tab  252  ( FIG. 14 ). The free portion of each pin  266 ,  266 ′ is then folded down in the groove  282 ,  282 ′ of the corresponding latch in order to be held stationary therein ( FIGS. 15, 3, 4 ). 
     As described above, the invention may be applied to the technology shown in  FIG. 1 , in which case the retaining means may be mounted upstream from the swirlers and may co-operate with an annular rim or with radial tabs of a centering ring.