FR2916833A1 - Annular shaped fuel supplying ramp for e.g. turbo-prop of aircraft, has bosses formed by hydroforming and inclined with respect to axis of curved pipe, where bosses are cut at their top for forming orifices for passage of fuel - Google Patents

Abstract

The ramp has bosses (162) formed by hydroforming using a hydroforming device and inclined with respect to an axis (148) of a curved pipe (146), where the pipe is made of stainless steel or nickel-chromium-iron alloy. The bosses are cut at their top for forming orifices for passage of fuel. The pipe has an end installed on rollers. The pipe is supplied with pressurized fluid e.g. fuel, through channels of pistons for pressurizing a wall of the pipe against an internal cylindrical surface of a matrix (150) of the hydroforming device. An independent claim is also included for a method for fabricating a fuel supplying ramp.

Description

1 Fuel supply ramp of a combustion chamber of

  turbomachine and its manufacturing process

  The present invention relates to a fuel supply ramp of a combustion chamber of a turbomachine, such as an aircraft turbojet or turboprop, and a method of manufacturing such a ramp. A fuel supply ramp of a turbomachine combustion chamber has an annular shape and extends around an outer cylindrical casing of the combustion chamber. It is connected to fuel supply means and to a plurality of injectors which are fixed on the housing and which open into the combustion chamber. In the known art, this ramp is generally formed of a plurality of arcuate curved ducts which are arranged end to end and connected to each other at their ends by T-connectors to which are also connected ducts. fuel supply of the injectors. The T-fittings are attached by soldering or brazing on the ends of the curved ducts. This technique has many drawbacks: the ramp comprises as many T-fittings as injectors to be supplied, for example 16 to 18 connections for a combustion chamber equipped with 16 to 18 injectors, and these connections formed by machining or foundry are costly, - three welds or solders are required for the fastening of a T-fitting, which represents 48 to 54 welds or solders for an annular fuel rail of 16 to 18 injectors, these welding operations or solders being long and to be carried out carefully to prevent fuel leakage, - the ramp is formed of many parts of two different types (16 to 18 curved ducts and 16 to 18 T-joints in the above example) whose storage and supply are expensive.

  The object of the invention is in particular to provide a simple, effective and economical solution to this manufacturing problem. It proposes for this purpose a fuel supply ramp of a turbomachine combustion chamber, this ramp being of generally annular shape and comprising means for connection to fuel supply lines of injectors, characterized in that it comprises at least one curved duct and comprising bosses formed by hydroforming and inclined relative to the axis of the duct, the bosses being cut at their apex to form fuel passage orifices. The feeding ramp according to the invention has the advantage of comprising one or more curved ducts which are each formed in one piece with connection bosses to the injectors. The ramp according to the invention therefore does not include the T-welded fittings of the prior art and its manufacture is much simpler and more economical. Each boss is machined at its top to form a fuel passage opening. These bosses extend substantially parallel to the axis of revolution of the ramp or more or less inclined relative to this axis. According to one embodiment of the invention, the ramp comprises a single curved duct, this duct extending about 360 and comprising as many pierced bosses as there are injectors to feed. The ramp is thus formed of a single duct formed in one piece with the injector connection bosses. This considerably reduces the number of parts required for the manufacture of a ramp (in the aforementioned example of the prior art, the ramp comprises 32 to 36 pieces: 16 to 18 curved ducts and 16 to 18 T-fittings).

  In a variant, the ramp is formed of two curved conduits in semicircle and connected together at one of their ends, each duct

  3 comprising a number of bosses equal to half the number of injectors to feed. In yet another variant, the ramp comprises a plurality of arcuate curved conduits, the conduits being arranged end to end and interconnected at their ends and having hydroformed bosses. In a particular embodiment of the invention, the ramp has a length of about one meter, an outer diameter of about 10 millimeters, and a wall thickness less than 1 millimeter and constant over its entire length. Its bosses each have an outer diameter of less than about 10 millimeters, a longitudinal dimension of the order of about 5 millimeters, and a wall thickness substantially identical to that of the conduit. The or each duct of the ramp may be made of stainless steel or an alloy of the INCO type. The invention also relates to a turbomachine, such as a turbojet or an airplane turboprop, characterized in that it comprises a ramp as described above. Finally, the invention relates to a method of manufacturing a ramp 20 for supplying fuel to a turbomachine combustion chamber, this ramp being of generally annular shape and comprising means of connection to fuel supply lines d injectors, characterized in that it consists in: a) subjecting a duct to hydroforming to bring material 25 into zones corresponding to the locations of the connection means and to form bosses inclined with respect to the axis of the and b) bending the conduit to a generally arcuate or polygonal curved shape, wherein step b) is performed before or after step a). Each arcuate duct is obtained by the method according to

  4 the invention from a rectilinear conduit. Step a) of the method makes it possible to form bosses on the ducts by hydroforming, each of these bosses being intended to form a connection means to an injector. The hydroforming step preferably comprises axial compression of the conduit. Step b) of the device is to bend the conduit by appropriate mechanical means. Step a) can be performed before or after step b), that is to say that the bosses can be formed by hydroforming from a rectilinear or arcuate curved conduit. According to another characteristic of the invention, the or each duct is bent around an axis and the bosses extend substantially parallel to this axis or substantially radially relative to this axis or obliquely to this axis.

  According to another characteristic of the invention, the method consists, after step a), cutting or piercing the top of each boss to form a fuel passage opening. The method may consist of bending a conduit about 360 and connecting both ends of this conduit to fuel supply means. As a variant, it may consist of bending semicircle ducts and then connecting these ducts together at one of their ends and at means of supplying fuel to the other of their ends. In yet another variant, the method consists in bending several arcuate conduits identically, arranging these ducts end to end, and connecting them to each other at their ends and to fuel supply means. The invention will be better understood and other details, characteristics and advantages of the present invention will emerge more clearly on reading the following description, given by way of nonlimiting example and with reference to the appended drawings in which: FIG. 1 is a schematic perspective view of a fuel supply system of a combustion chamber of a turbomachine according to the known technique, seen from downstream, - Figures 2 and 3 are schematic views in axial section. of a device for hydroforming a rectilinear conduit, illustrating step a) of the manufacturing method according to the invention, - Figures 4 and 5 are partial schematic views in axial section of rectilinear ducts, after the hydroforming step, - Figure 6 is a partial schematic view in axial section of a rectilinear conduit, after machining its bosses, - Figures 7 and 8 show very schematically bending means of a tube deformed by hydroforming, illustrating step b) of the method according to the invention, and - Figures 9 and 10 are diagrammatic views in axial section of a device for hydroforming an arcuate curved conduit, illustrating step a) of a variant of the method according to the invention. FIG. 1 shows a system 10 for supplying fuel to an annular combustion chamber of a turbomachine such as an airplane turbojet or turboprop, which is carried by an outer cylindrical casing 12 of the combustion chamber. combustion, this housing 12 having at its axial ends annular flanges 14 for attachment to corresponding housings of a compressor and a turbine of the turbomachine. The system 10 comprises an annular fuel supply ramp 16 which extends around the housing 12, at a distance from the latter, and which is connected on the one hand to means (not shown) for supplying fuel, and on the other hand to injectors 18 which are fixed on the housing 12 and which each comprise a duct 20 which extends radially inside the casing 12 through an orifice 22 thereof and which comprises a radially inner end 24 facing downstream in the combustion chamber. The injectors 18 are held on the housing by means of flanges 26 which close the orifices 22 and which are fixed to the housing by screws 28. These screws also make it possible to fix means 30 for supporting the ramp 16 to the housing 12. The ramp 16 is formed in the known art of a plurality of curved arcuate conduits 32 which are arranged end to end and connected to each other at their ends by T-joints 34. Each connector 34 has two substantially coaxial ends attached to each other. by welding or brazing on the ends of two consecutive curved ducts 32.

  The middle portion of each connector 34 comprises a tip which extends in the example shown substantially parallel to the axis X of the casing 12, and which is connected by welding or soldering to one end of a duct 36 bent in U or L whose other end is connected to an injector 18.

  When the fuel supply system 10 comprises from 16 to 18 injectors, the ramp 16 is formed of 16 to 18 conduits 32 and 16 to 18 connectors 34, the conduits and fittings being secured to each other by welding or soldering . The ramp according to the invention has the advantage of including a reduced number of parts compared to the prior art by integrating these connections to the duct (s) of the ramp. According to a first embodiment of the method according to the invention, the ramp is manufactured from at least one rectilinear conduit which is subjected to hydroforming to form connection bosses 25 to the injectors and which is bent to give the conduit a generally curved shape in an arc. More specifically, the method consists in introducing a rectilinear conduit 46 into a hydroforming device, which comprises in the example shown in FIG. 2, a matrix 50 formed of two straight elongated half-shells and delimiting a cylindrical axial bore 52 opening at both ends of the matrix and within which is

  7 is placed substantially without clearance duct 46. A cylindrical piston 54 is engaged sealingly in the bore 52 at each of its ends, and comprises an axial channel 56 opening at one end inside the bore 52 and connected to its other end to pressurized fluid supply means, such as water. The die 50 comprises a plurality of recesses 60 which are formed in the inner cylindrical surface of one of the half-shells. These recesses 60 are of substantially frustoconical shape whose small diameter bottom has a concave curved shape. They are aligned with each other and evenly distributed along the axis 48 of the matrix and the duct, in zones of the duct 46 corresponding to the bosses to be produced. These recesses 60 are four in number in the example shown. The introduction of a fluid under pressure into the conduit 46 through the channels 56 of the pistons 54 (arrows 58) will cause the pressure of the wall of the conduit 46 against the internal cylindrical surface of the matrix, and the extrusion of material in the recesses 60 of the bore, this material being pressed against the inner surfaces of the recesses 60 to form the walls of the bosses 62 (Figure 3).

  To avoid a thinning of the wall of the duct 46 near the recesses 60 and differences in thickness between the wall of the duct and the walls of the bosses 62, the pistons 54 are moved axially towards each other along the arrows 64 for axially compressing the duct 46 and promoting the creep of material at the periphery of the recesses 60.

  The shape and dimensions of the recesses 60 thus correspond to the shape and dimensions of the bosses 62 to be created. The bosses 62 may extend substantially radially with respect to the axis 48 of the duct (FIG. 4), or may be slightly inclined with respect to this axis. In the example of FIG. 5, the axis of the boss 62 'is inclined in a plane passing through the axis 48 of the duct at an angle (3 with respect to a plane transverse to the duct. example

  8 less than 30. The method according to the invention further comprises cutting the top of each boss to be able to form a hole 66 for fuel passage (Figure 6). This machining operation can be performed by milling, drilling, etc. The duct 46 is then bent in an arc around an axis, the bosses 62 being oriented in the same direction substantially parallel to this axis (FIG. 8) or outwardly in directions substantially radial with respect to this axis ( Figure 7).

  In the embodiment of FIG. 7, each duct is bent locally at one or more points evenly distributed along the length of the duct between two consecutive bosses 62 to form a duct having a generally curved shape with a polygonal contour. The bending device comprises for example in this case two fixed rollers 70, 72 placed close to each other on a substantially horizontal line, and a movable roller 74 placed halfway and above the rollers 70, 72 , this roller 74 being movable in translation along a vertical line. The rollers 70, 72, 74 comprise for example a peripheral annular groove 76 for guiding and centering the conduit. A rectilinear duct 46 having bosses 62 obtained by hydroforming is installed horizontally in the annular grooves 76 of the fixed rollers 70, 72. The movable roller 74 is then moved vertically on a determined path towards the rollers 70, 72, until it comes in contact with the duct and that this duct is deformed in V between the rollers. This operation is repeated several times in several places of the conduit to give it a polygonal contour. The bosses 62 extend here substantially radially with respect to the bending axis of the conduit, but they could be oriented substantially parallel to this axis, as shown in FIG. 8. The bending device of FIG. 8 differs from that of FIG. of Figure 7

  9 in that the rollers are further rotatable about their axes of revolution which are parallel to each other. One end of a duct 46 is installed on the rollers 70, 72 and the roller 74 is brought closer to the rollers 70, 72, as previously described. The rollers 70, 72, 74 are rotated so that the conduit is moved by the rollers (to the left in the drawing) and plastically deforms continuously over its entire length, to have a curved shape in an arc. In the variant shown in Figures 9 and 10, the method is firstly to bend a conduit to give it a curved shape in a circular arc, and then to deform the conduit by hydroforming to form bosses connection to the injectors. The conduit is bent by one of the devices described in Figures 7 and 8 or by any other suitable technique. This duct is then introduced into a hydroforming device comprising a matrix 150 which differs from the matrix of FIGS. 2 and 3 in that it comprises a curved internal arcuate passage inside which is placed substantially without clearance. curved conduit 146. The die 150 comprises a plurality of recesses 160 which extend substantially radially outwardly with respect to the bending axis A of the conduit and which are regularly distributed over a circumference of this axis. These recesses 60 are nine in the example shown. The operation of this hydroforming device is identical to that of FIGS. 2 and 3.

  A final step of the method according to the invention is to cut the top of each boss 162 to form a through hole. As shown in FIG. 10, the duct 146 obtained by the process according to the invention is semicircular and is intended to be fixed at one end by welding or brazing at the end of a second semicircular duct 146 identical, so to form an annular fuel supply ramp of a combustion chamber, the other ends of

  10 conduits 146 being connected to each other and to fuel supply means. The open tops of the bosses are attached by welding or brazing on injectors fuel supply lines.

Claims (16)

  1. Fuel supply ramp of a turbomachine combustion chamber, of generally annular shape and comprising means for connection to lines (36) for supplying fuel to injectors, characterized in that it comprises minus one curved conduit (46) and including bosses (62) formed by hydroforming and inclined with respect to the axis (48) of the conduit, the bosses being cut at their apex to form fuel passage orifices (66).   2. Ramp according to claim 1, characterized in that it comprises a single curved duct, the duct extending over 360 approximately and comprising a number of bosses equal to the number of injectors to supply.   3. Ramp according to claim 1, characterized in that it comprises two ducts (146) curved in a semicircle and connected together at one of their ends, each duct comprising a number of bosses (162) equal to the half the number of injectors to feed.   4. Ramp according to claim 1, characterized in that it comprises a plurality of ducts (46) curved, the ducts being arranged end to end and interconnected at their ends and having bosses (62) hydroformed.   5. Ramp according to one of the preceding claims, characterized in that the or each boss (62) extends parallel to the axis of revolution (A) of the ramp or radially relative to this axis (A) or oblique to this axis.   6. Ramp according to one of the preceding claims, characterized in that the ramp has a length of about one meter, an outer diameter of about 10 millimeters, and a wall thickness less than 1 millimeter and constant over its entire length .   7. Ramp according to claim 6, characterized in that the bosses each have an outer diameter of less than about 10 millimeters 12, a longitudinal dimension of the order of about 5 millimeters, and a wall thickness substantially identical to that of the conduit.   8. Ramp according to one of the preceding claims, characterized in that the or each duct is made of stainless steel or an alloy of INCO type.   9. Turbomachine, such as a turbojet engine or a turboprop aircraft, characterized in that it comprises a ramp according to one of the preceding claims.   10. A method of manufacturing a fuel supply ramp of a turbomachine combustion chamber, this ramp being of generally annular shape and comprising means for connection to lines (36) supplying fuel injectors characterized in that it comprises: a) subjecting a conduit (46, 146) to hydroforming to supply material to areas corresponding to the locations of the connecting means and forming inclined bosses (62, 162) therein relative to the axis of the duct, and b) bend the conduit to give it a generally arcuate or polygonal curved shape, step b) being performed before or after step a).   11. The method of claim 10, characterized in that it consists, after step a), cut or drill the top of each boss (62, 162) to form a fuel passage opening.   12. The method of claim 10 or 11, characterized in that the or each duct is bent around an axis (A) and in that the bosses extend substantially parallel to this axis (A) or radially relative to this axis (A) or oblique to this axis.   13. Method according to one of claims 10 to 12, characterized in that it consists in bending a duct about 360 and to connect the two ends of the duct to fuel supply means.   14. A method according to one of claims 10 to 12, characterized in that it consists in bending conduits (146) in a semicircle and then connect these conduits together at one of their ends and means of supply of fuel to the other of their ends.   15. Method according to one of claims 10 to 12, characterized in that it consists in bending several conduits (46) in a circular arc in an identical manner, arranging these conduits end to end, and connecting them to each other. their ends and fuel supply means.   16. Method according to one of claims 10 to 15, characterized in that the hydroforming step comprises an axial compression of the conduit.