The invention relates to the field of combustion assemblies for turbomachines, and more particularly to fuel injection devices in the combustion chamber of these sets.

STATE OF THE ART

A turbine engine generally comprises, from upstream to downstream in the direction of gas flow, a blower, one or more compressor stages, e.g., a high pressure compressor and a low pressure compressor, a combustor, one or more turbine stages, e.g., a high pressure turbine and a low pressure turbine, and a gas exhaust nozzle.

Figure 1 attached illustrates schematically, a longitudinal sectional view of the combustion assembly 1 of an embodiment of a turbomachine according to the prior art.

The combustion assembly 1 is in communication upstream (left in Figure 1), with a compressor (not shown), which feeds pressurized air via a diffuser, and is connected in downstream, a dispenser itself connected to a high pressure turbine (not shown in the figures).

The combustion assembly 1 is delimited by an outer casing 2 and an inner annular casing 3, extending one inside the other along a longitudinal axis X-X '.

The combustion assembly 1 comprises a "flame tube" or "combustion chamber" 4 which is the seat of the combustion gases.

The flame tube 4 is arranged between the two outer casings 2 and inner 3 and is provided with revolution of front walls 5 and rear 6 which extend generally one inside the other around the longitudinal axis XX '.

The front and rear walls 5 and 6 show a bent ring-shaped and are connected, upstream, to the inner casing 3, on either side of a centrifugal injection wheel 7, and downstream to the outer casing 2 and the inner casing 3, respectively.

This type of flame tube is called "annular" and extends around the longitudinal axis XX 'of the combustion assembly 1.

The front and rear walls 5 and 6 are generally formed at a distance from the outer and inner casings 2 and 3, so as to form an annular air supply duct 8 surrounding the flame tube 4.

The flame tube 4 comprises a plurality of successive zones from upstream to downstream, namely a primary zone 9 into which the injection wheel 7 and an intermediate zone 10 at the tube bend, wherein is a number diluted 1 1 hoses.

The air enters the flame tube 4 through a plurality of air inlet openings 12 formed through the front wall 5 and a plurality of air inlets 13 formed through the rear wall 6, and, opposite a portion of the primary zone 9.

The injection centrifugal wheel 7 is mounted on a motor shaft 15, and is rotated by it. The drive shaft 15 is coaxial with the longitudinal axis XX 'of the combustion assembly 1.

The combustion assembly 1 is further provided with a plurality of injectors 16, distributed regularly about the drive shaft 15. The injectors 16 are arranged between the motor shaft 15 and the inner casing 3, which also constitutes the bottom (or "inner side") of the flame tube 4 (relative to the longitudinal axis X-X ').

Each injector 16 is arranged so as to project fuel axially (see arrow i) parallel to the longitudinal axis X-X ', on the front face 17 of the injection wheel 7, that is to say the side facing the upstream of the combustion assembly 1.

Since the injection wheel 7 is rotated, the film of fuel which comes into contact with the front face 17 is subjected to centrifugal force and moves outward of the radially wheel (see arrow j).

The annular peripheral rim 18 of the wheel 7 is pierced at regular intervals, several slots 19 extending radially.

The fuel subjected to the centrifugal force through the slots 19 and is projected radially relative to the drive shaft 15 in the flame tube 4 (arrow k) and is atomized into very fine droplets, which promotes mixing with the compressed air in it.

Such set of combustion injection centrifugal wheel has many advantages, especially for small engines, such as helicopter engines. These benefits are:

it is not necessary to have a special type of injector,

- these injectors are very sensitive to the viscosity of the fuel, itself linked to the type of fuel or at room temperature,

the casing of the turbine is of simple structure and of low mass and consequently low cost,

it is possible to obtain a compromise between the nitrogen oxide emissions (NOx) on the one hand, and emissions of carbon monoxide (CO) and unburnt hydrocarbons (HC) of the other part, which is such these emissions are among the lowest of all aeronautical combustion systems.

However, this type of combustion assembly also has drawbacks associated with the position of the injectors, which are under the flame tube, close to the drive shaft and therefore to the inside of the combustion package. Or, turbomachines are used with temperature to progressively rise cycles to reduce specific fuel consumption, which causes a coking (that is to say, solidification) of the fuel. It is therefore necessary to clean increasingly the injection system and many labyrinth seals disposed around, in order to avoid malfunctions (such as for example the blocking of the shaft by solidified fuel ( "coke") , premature wear hot parts due to poor distribution of the fuel, or the non-starting of the engine due to blocking of the fuel supply).

It is then necessary to remove a large portion of the turbine engine (and therefore to perform removing the engine from the helicopter) to access the injectors located in a central, clean and / or replace the seals and access the labyrinth willing near the injection wheel. It is indeed not possible to change the injector when the engine is in place, resulting in additional handling and costs and increases the period of immobilization of the helicopter.

Further, in the combustion assembly such as that shown in Figure 1, the diameter of the injection wheel is important, since it is necessary to leave sufficient space between the motor shaft 15 and the edge of the wheel 7, to arrange the injectors 16. as a result, this injection wheel has a large mass and is subject to high stresses due to the speed.

US 4,040,251 describes a combustion assembly of the aforementioned type, wherein the nozzle and its feed tube are arranged in the thickness of the inner casing and the flame tube from the bottom. The injector spray orifice opens into the opening in the bottom for the passage of the injection wheel.

As for the combustion assembly described above, access to the nozzle is difficult, and maintenance is complex and costly.

PRESENTATION OF THE INVENTION

The invention aims to provide a combustion assembly of the aforementioned type, which retains the above advantages but which solves the drawbacks mentioned above.

The invention has particularly for object to provide a combustion assembly wherein the flame torch or the injectors are readily removable, without it being necessary to disassemble the whole of the turbomachine and of the depositing cell the helicopter.

To this end, the invention relates to a turbomachine combustion, comprising:

an annular flame tube, comprising a front wall provided with an upstream area facing upstream of the combustion assembly, a rear wall provided with an upstream area facing upstream of the combustion assembly and a bottom disposed opposite a drive shaft,

an injection wheel rotated by said coaxial drive shaft to the longitudinal axis XX 'of the combustion assembly, the injection wheel protruding partly into the flame tube through its bottom, and being configured for spraying fuel into the flame tube by centrifugation,

at least one injector, capable of depositing a film of fuel on said injection wheel.

According to the invention, said injector is disposed through said upstream region of the front wall or through said upstream region of the rear wall of the flame tube and so that its injection port opens into the interior of this tube opposite the portion of said injection wheel is in said flame tube.

With these features of the invention, it is much easier to disassemble the injectors, since it is no longer necessary to access the area between the flame tube and the bottom of the drive shaft the injection wheel. This disassembly can be carried out on the place where the device is located (e.g., helicopter) with this set of combustion.

Advantageously and according to a first embodiment, said injector is disposed therethrough from the upstream zone of the front wall of the flame tube, said injection wheel is bent at its periphery, upstream of the entire combustion, so as to have an annular flange, said annular flange is pierced with a plurality of radial injection lights and said injector discharges into the flame tube facing the front face of the annular peripheral portion of said injection wheel which in the flame tube.

Advantageously and according to another alternative embodiment, said injector is disposed therethrough from the upstream zone of the rear wall of the flame tube, said injection wheel is bent at its periphery, downstream of the entire combustion, so as to have an annular flange, said annular flange is pierced with a plurality of radial injection lights and said injector discharges into the flame tube facing the rear face of the annular peripheral portion of said injection wheel which in the flame tube.

Advantageously and according to yet another embodiment, said injection wheel is full and has a radial annular face for receiving the fuel which projects into the flame tube and the injector opens into the flame tube, opposite this annular fuel receiving face.

In this case preferably the injector is oriented so as to project the fuel tangentially on said receiving face of the fuel injection wheel.

It is also possible that the receiving face of the fuel injection wheel forms an angle a with the axis of the injection port of the injector, this angle (a) being between 90 ° and 180 ° .

In a first variant, in the combustion assembly according to the invention, the axis of the injection port of the injector extends in a plane which includes both the axis of the injection wheel and is perpendicular to the median plane of the wheel perpendicular to the axis of the injection wheel.

In a second variation, in the combustion assembly according to the invention, the axis of the injector of the injection port is not perpendicular to the median plane of the wheel perpendicular to the axis of the wheel 'injection.

The invention also relates to a turbomachine comprising a plurality of combustion as mentioned above.

PRESENTATION DES FIGURES

Other features and advantages of the invention will become apparent from the description will now be made with reference to the accompanying drawings, which show, as non-limiting indication, different possible embodiments.

In these drawings:

Figure 1 is a longitudinal sectional view of a combustor according to an embodiment of the prior art,

Figures 2 and 3 are schematic views in longitudinal section of two embodiments of a combustor assembly of a turbomachine according to the invention,

Figure 4 is a schematic view of the combustion assembly, taken along a cutting plane materialized by the line IV-IV in Figure 3.

DETAILED DESCRIPTION

A first embodiment of the invention will now be described in connection with Figure 2.

This figure 2 is a diagram of a combustion assembly 20, which is simplified compared to that of Figure 1, representing only the flame tube and the injection assembly.

The flame tube 21 includes a base 22 (or inner side of the flame tube), a front wall 23 and a rear wall 24. The base 22 connects the front wall 23 and rear wall 24.

As for the combustion assembly 1 above, the flame tube 21 is annular and extends around the longitudinal axis XX 'of the combustion assembly 20.

The bottom 22 is provided with an opening 25 allowing the passage of part of the injection wheel 26 within the flame tube 21. In

other words, the injection wheel 26 is partly projecting into the base of the flame tube 21.

The front wall 23 has an upstream region 230, facing upstream of the combustion assembly and the turbomachine (left in Figure 2), pierced with a plurality of air inlet ports 27, facing the primary combustion zone 28 of the flame tube.

Similarly, the rear wall 24 has an upstream region 240, facing upstream of the combustion assembly and the turbomachine, pierced with a plurality of air inlet holes 29, next to the area primary combustion 28 of the flame tube.

The injection wheel 26 is rotated by the drive shaft 30, coaxial to the longitudinal axis X-X '. It has a front face 31, facing upstream of the combustion assembly and a rear face opposite 32 pointing downstream.

This injection wheel 26 is bent at its periphery so as to define an annular peripheral rim 33, bored, preferably at regular intervals by slots 34 radially oriented with respect to the longitudinal axis XX 'of the assembly combustion 20. These slots 34 may be holes or slots.

Compared to the injection wheel 7 of the prior art

(See Figure 1), it is noted that the injection wheel 26 here penetrates further inside the flame tube 21 since not only its annular peripheral flange 33 integrally therein, but also an annular peripheral portion 260 of the disc which constitutes the wheel 26. the annular portion 260 is located in the extension of the flange 33.

The inner face of the annular rim 33 is thus at a distance D1 of the bottom 22 of the flame tube 21 which is itself under the motor shaft 30.

The combustion assembly also includes one or more injectors 35, of which only one is visible in Figure 2.

This injector 35 is connected to a tube 36 for fuel supply itself connected to a fuel source, not shown in FIG.

The injector 35 has an injection orifice 37.

Unlike the prior art, the injector 35 is arranged so as to cross the front wall 23 of the flame tube 21, preferably the upstream area 230, through which are formed the air inlet ports 27. in addition, the injector 35 is disposed so that its injection port 37 opens into the interior of the flame tube 21.

To this end, it is noted that the distance D1 is sufficient to allow passage of the fuel jet issuing from the injection end 37 of the injector 35.

The operation of the injection is as follows. The fuel from injector 35 leaves through the injection port 37 and is projected against the front face 31 of the portion 260 of the injection wheel 26, where it forms a fuel film F.

Under the action of centrifugal force due to the rotation of the injection wheel 26, the fuel film moves towards the periphery of the wheel and through the openings 34, which has the effect, in contact with the air surrounding the wheel, to spray or atomize fuel into very fine droplets G, distributed within the flame tube 21.

That the injector 31 is disposed through the front wall

23 of the flame tube facilitates disassembly. Preferably, its configuration will be adapted to provide for its extraction through the front wall 23.

Advantageously also, note that the injection wheel 26 has a smaller diameter than that of the prior art shown in Figure 1, since the bottom 22 of the flame tube 21 may be disposed closer to the drive shaft 30. It will be noted in this respect that in figures 1 and 2 are not shown to the same scale.

The injection wheel 26 being of smaller diameter, its mass is smaller than that of a wheel of the state of the art and its mechanical strength is thereby also improved.

Another embodiment of the invention will now be described in conjunction with Figure 3. The same elements have the same reference numerals and will not be described again in detail.

The injection wheel bears the reference 41. It is rotated by the drive shaft 30.

It differs from the injection wheel 26 in that it is full, that is to say, it is not pierced of injection ports 34. The peripheral flange 42 is flared to define a radial annular face 43, preferably flat, fuel film F of the reception.

The injector 35 is disposed so that its injection port 37 is opposite this face 43.

The axis of the injection port 37 forms an angle a (alpha) with the fuel receiving face 43. This angle a is advantageously between 90 ° and 180 °. When it is 180 °, the fuel injection is tangent to the face 43.

Note also that, in this case, if we consider the median plane P of the wheel (41) perpendicular to the axis of the drive shaft 30 driving the wheel, while the axis of the injection orifice 37 of an injector 35 extends in a plane P1 that is both perpendicular to P and that includes the axis of the drive shaft 30. in Figure 3, plane P1 corresponds to the plane of the sheet of the Figure and in Figure 4, the plane P1 is represented by a straight broken lines.

However, it is also possible to orient the axis of the injection port 37 so that it is not perpendicular to P. In other words, this axis then projects or deviates from the plane P1 corresponding to the plane of Figure 3. in Figure 4, this axis is referenced X1 -ΧΊ.

In this embodiment, it is noted that the injector 35 is advantageously introduced less deeply into the flame tube 21 as in the embodiment of Figure 2, since it is not necessary that its injection port reaches the area under the annular rim 33 of the injection wheel. Just allow the injector fuel spray on the face 43. The dismantling of the injector 35 is thereby facilitated.

As before, the fuel film F undergoes the centrifugal force generated by the wheel 41 and is atomized in the form of fuel droplets G.

This embodiment of the invention allows for an injection wheel 41 having a structure of great simplicity and good mechanical strength, since it is not pierced by through lights. Its diameter is also smaller than in the prior art, since the bottom 22 of the flame tube 21 may be closer to the drive shaft 30. Finally, the combustion is situated substantially on one side of the wheel injection 41, here on the left of Figure 3.

Also, note that the invention embodiments are possible. In particular, the injector 35 may be disposed through the rear wall 24 of the flame tube 21, preferably through its upstream zone 240.

In this case, and when the injection wheel 26 is performed according to the embodiment of Figure 2, the annular flange 33 is rotated in the downstream direction of the combustion assembly 20 and the fuel injection is made on the rear face 32 of the wheel.

When the injector is disposed through the rear wall 24 and the injection wheel 41 is consistent with the embodiment of Figure 3, then the receiving face 43 is oriented towards the rear wall 24.

The different possible inclinations of the axis of the injection port 37 and the different values ​​of the angle a described above also apply to this embodiment.

Finally, according to another alternative embodiment, it is possible to provide that the flame tube 21 is made of several parts assembled by means of a flange 50 which facilitates disassembly.

CLAIMS

1. combustion assembly (20) for a turbomachine, comprising:

a flame tube (21) annular, comprising a front wall (23) provided with an upstream region (230) facing the upstream of the combustion assembly (20), a rear wall (24) provided with a upstream region (240) facing the upstream of the combustion assembly (20) and a bottom (22) disposed opposite to a motor shaft (30),

an injection wheel (26, 41) rotated by said motor shaft (30) coaxial to the longitudinal axis XX 'of the combustion assembly (20), this wheel injection (26, 41) projecting partly in the flame tube (21) through its bottom (22) and being configured to spray fuel into the flame tube by centrifugation,

at least one injector (35) capable of depositing a film of fuel on said injection wheel (26, 41),

this combustion assembly being characterized in that said injector (35) is disposed through said upstream region (230) of the front wall (23) or through said upstream region (240) of the rear wall (24) of the tube flame (21) and so that its injection port (37) opens into the interior of the tube (21) facing the portion (260, 43) of said injection wheel (26, 41) which is located in said flame tube (21).

2. combustion assembly (20) according to claim 1, characterized in that said injector (35) is disposed therethrough from the upstream zone (230) of the front wall (23) of the flame tube (21), in that said injection wheel (26) is bent at its periphery, upstream of the combustion assembly so as to have an annular flange (33), in that said annular flange (33) is pierced by several lights (34) radial injection and in that said injector (35) opens into the flame tube (21) opposite the front face (31) of the annular peripheral portion (260) of said injection wheel is in the flame tube (21).

3. combustion assembly according to Claim 1, characterized in that said injector (35) is disposed therethrough from the upstream zone (240) of the rear wall (24) of the flame tube (21), in that said wheel injection (26) is bent at its periphery, downstream from the combustion assembly, so as to have an annular flange (33), in that said annular flange (33) is pierced with a plurality of radial slots ( 34) injection and in that said injector (35) opens into the flame tube (21) facing the rear face (32) of the annular peripheral portion (260) of said injection wheel which is in flame tube (21).

4. combustion assembly according to claim 1, characterized in that said injection wheel (41) is solid and has an annular radial face (43) for receiving the fuel which projects into the flame tube (21) and that the injector (35) opens into the flame tube (21) opposite this annular face (43) for receiving the fuel.

5. Combustion arrangement according to claim 4, characterized in that the injector (35) is oriented so as to project the fuel tangentially to said face (43) for receiving the fuel from the injection wheel.

6. combustion assembly according to claim 4, characterized in that the face (43) for receiving fuel from the wheel injection (41) forms an angle a with the axis of the injection port (37) of the injector (35), this angle (a) being between 90 ° and 180 °.

7. combustion assembly according to one of Claims 4 to 6, characterized in that the axis of the injection orifice (37) of the injector (35) extends in a plane

(P1) which includes both the axis (30) of the wheel of injection (41) and is perpendicular to the median plane (P) of the wheel (41) perpendicular to the wheel axis of injection ( 41).

8. combustion assembly according to one of Claims 4 to 6, characterized in that the axis of the injection port (37) of the injector (35) is not perpendicular to the median plane (P) of the wheel (41) perpendicular to the axis of the injection wheel (41).

9. A turbomachine comprising a combustion assembly according to one of the preceding claims.