Combustion chamber

Abstract

Combustion chamber This document relates to a combustion chamber (18) for a longitudinal axis turbomachine (L) comprising an outer annular wall (24) and an inner annular wall connected by a bottom annular wall of the chamber, at least one of the inner and outer annular walls (24) comprising dilution orifices, said dilution orifices (26a, 26b) comprising at least a first series of orifices (26a) and a second series of orifices (26b) and means for opening / closing the orifices (26a, 26b) of said first and second series of orifices so as to selectively allow the passage of air in the orifices of only one of the first series of orifices (26a) and the second series of orifices (26b), the effective area of ​​the orifices of the first series of orifices being equal to the effective area of ​​the orifices of the second series of orifices. Figure from the summary: Figure 2

Description

Title of the invention: Combustion chamber Technical field

[0001] The present disclosure relates to the field of aircraft combustion chambers, and more specifically relates to the supply of dilution air to the combustion chamber. More particularly, the invention relates more particularly to an optimization of the position of the dilution holes present on the walls of the combustion chamber. Prior art

[0002] In the remainder of the description, the terms "upstream" or "downstream" will be used to designate the positions of the structural elements relative to each other in the axial direction, taking as reference the direction of flow of the gases. Similarly, the terms "internal" or "radially internal" and "external" or "radially external" will be used to designate the positions of the structural elements relative to each other in the radial direction, taking as reference the axis of rotation of the turbomachine.

[0003] A turbomachine comprises one or more compressor(s) delivering pressurized air to a combustion chamber where the air is mixed with fuel and ignited to generate hot combustion gases. These gases flow downstream of the chamber to one or more turbine(s) which transform(s) the energy thus received to drive the compressor(s) in rotation and provide the energy necessary, for example, to power an aircraft.

[0004] Conventionally, a combustion chamber of a turbomachine with a longitudinal axis comprises two radially inner and outer annular walls connected to each other by an annular chamber bottom wall comprising openings distributed circumferentially around the longitudinal axis and each traversed by an injection device which allows the supply of a mixture of air and fuel into the chamber between the inner and outer walls. These inner and outer walls together define a flame tube which is annular and in which the combustion of the fuel is carried out.

[0005] Generally speaking, a combustion chamber must meet several requirements and is sized accordingly. First of all, it must allow the fuel to be used optimally, i.e., achieve the highest possible combustion efficiencies. It must also provide the turbine with hot gases, the temperature distribution of which at the chamber outlet must be, on the one hand, compatible with the required reliability and, on the other hand, as uniform as possible. It must also degrade the energy of the flow as little as possible, and therefore generate a loss of pressure between its minimum inlet and outlet. The components of the combustion chamber must finally have good mechanical strength, which requires reducing the temperature of the chamber walls.

[0006] Inside the chamber, combustion takes place in two main phases, to which physically correspond two zones. To produce the air / fuel mixture, air is injected both at the injectors, at the bottom of the chamber and through the walls of the chamber through a first row of orifices called primary holes. The temperature reached by the gases resulting from combustion in the primary zone is very high. It can reach, for example, 2000 C, a temperature incompatible with the good mechanical strength of the materials of the turbine and the chamber. It is therefore necessary to cool these gases, which is carried out in a second zone. Generally, the primary zone represents approximately the first third of the length of the chamber. In the second zone, also called the dilution zone, fresh air, called dilution air, from the compressor, is injected into the chamber through its walls through orifices called dilution holes.Dilution air cools the combustion gases and the chamber walls. Dilution air, by cooling the gases, homogenizes the temperature of the hot gases entering the high-pressure turbine downstream of the combustion chamber.

[0007] Currently, the sizing, positioning and number of dilution holes as well as the sizing of the stator and rotor blades of the high-pressure turbine are determined so that the fining of the blades is minimized at all operating phases of the turbomachine. The choice of the number of dilution holes and their positioning determines once and for all the radial portion of the geometry of a blade which will be subjected to a maximum temperature in operation. However, it is desirable to be able to change this radial portion subjected to a maximum temperature (and therefore to fining) during the operation of the turbomachine.

[0008] This leads to the blades not being mechanically stressed optimally and can have a negative impact on their service life. An increase in the service life of the parts is desirable to limit the climate impact, in particular the greenhouse gas emissions resulting from the production of said parts. The applicant pays particular attention to the development of methods and techniques aimed at increasing the service life of the parts in order to reduce its carbon footprint.

[0009] To this end, the invention proposed below is part of the research and development programs aimed at very significantly improving the performance of aircraft and, in this sense, contributes to reducing the environmental impact of aircraft. Summary

[0010] A combustion chamber for a turbomachine with a longitudinal axis is proposed, comprising an outer annular wall and an inner annular wall connected by an annular chamber end wall, at least one of the inner and outer annular walls comprising dilution orifices, said dilution orifices comprising at least a first series of orifices and a second series of orifices and means for opening / closing the orifices of said first and second series of orifices so as to selectively allow the passage of air into the orifices of only one of the first series of orifices and the second series of orifices, the effective section of the orifices of the first series of orifices being equal to the effective section of the orifices of the second series of orifices.

[0011] According to the invention, the simultaneous opening of the orifices of the first series makes it possible to obtain a first temperature field at the outlet of the combustion chamber, the orifices of the second series being closed. The simultaneous opening of the orifices of the second series makes it possible to obtain a second temperature field at the outlet of the combustion chamber, the orifices of the first series being closed. These two configurations of openings of the dilution orifices make it possible to operate in finage a larger radial part of the stator and rotor blades of the high-pressure turbine. The preservation of the overall effective section of the chamber guarantees not to modify the operation of the chamber but only the flow upstream of the two rows of dilution holes.

[0012] Said first series of orifices may comprise a first annular row of upstream orifices and said second series of orifices comprises a second annular row of downstream orifices.

[0013] The means for opening / closing said series of orifices may comprise at least one ring with a longitudinal axis connected to a plurality of connecting rods each connected to a cam whose periphery is in contact with an actuator for simultaneously opening / closing the orifices of the first series of orifices and the orifices of the second series.

[0014] The actuator may comprise a support rotatably articulated between a first position in which the orifices of the first series of orifices are in the open state and the orifices of the second series of orifices are in the closed state and a second position in which the orifices of the first series of orifices are in the closed state and the orifices of the second series of orifices are in the open state.

[0015] Return means can provide permanent contact between the support and the cams.

[0016] The opening / closing of the orifices of the first series and the second series can be controlled by an electrical device.

[0017] The present document also relates to a turbomachine comprising a combustion chamber as described previously.

[0018] This document also relates to a method of using the combustion chamber or the turbomachine described above, comprising a step of selecting the opening of the orifices of one of the first and second series of orifices as a function of a thermodynamic parameter of the combustion chamber which may be for example an outlet temperature of the combustion chamber, and / or a parameter of the turbomachine intended to comprise said combustion chamber which may be for example the rotation speed of the high pressure compressor or low pressure compressor. Brief description of the drawings

[0019] Other characteristics, details and advantages will appear on reading the detailed description below, and on analyzing the attached drawings, in which:

[0020] [Fig-1] is a schematic view of a turbomachine according to the known technique;

[0021] [Fig.2] illustrates an embodiment of a combustion chamber according to the present document, in particular means of opening / closing the dilution orifices;

[0022] [Fig.3] is a schematic view of the means for opening / closing the orifices of dilution according to this document;

[0023] [Fig.4] is a schematic view of another embodiment of the invention. Description of the embodiments

[0024] We now refer to [Fig.l] which represents a turbomachine 10 of longitudinal axis L according to the known technique comprising from upstream to downstream in the direction of air flow, a low pressure compressor 12, a centrifugal compressor 14 comprising a radial annular diffuser 16 whose downstream end supplies air to an annular combustion chamber 18, a high pressure turbine 20 then a low pressure turbine 22. The combustion chamber 18 is here with reverse flow, that is to say that it is observed that the air flow flows along the longitudinal axis in a direction opposite to that in which the air flows in the low pressure 14 and high pressure 16 compressors. Obviously, the present document applies to any type of chamber and also to that having a flow of hot gases in the same direction as that of the air flowing in the compressors.

[0025] As mentioned previously, a combustion chamber comprises an inner annular wall and an outer annular wall 24 connected to each other at an annular chamber bottom wall. In [Fig.2], only the outer annular wall is shown. The combustion chamber radially inside a casing 26 surrounding it externally.

[0026] The external annular wall 24 comprises air dilution orifices 26a, 26b which are preferably arranged downstream of primary orifices used to provide an air supply necessary for the proper combustion of the fuel supplied by the injectors. According to the present document, the external annular wall 24 comprises at least a first series of orifices 26a and a second series of orifices 26b and means for opening / closing the orifices of said first and second series of orifices so as to selectively allow the passage of air into the orifices of only one of the first series of orifices 26a and the second series of orifices 26b, the effective section of the orifices of the first series of orifices 26a being equal to the effective section of the orifices of the second series of orifices 26b.

[0027] In the embodiment shown, the orifices of the first series of orifices are arranged in a first annular row and the orifices of the second series of orifices are arranged in a second annular row. The first row is arranged upstream of the second row. The simultaneous opening of the orifices 26a of the first series makes it possible to obtain a first temperature field at the outlet of the combustion chamber, the orifices of the second series 26b being closed. The simultaneous opening of the orifices 26b of the second series makes it possible to obtain a second temperature field at the outlet of the combustion chamber, the orifices 26a of the first series being closed. These two configurations of openings of the dilution orifices make it possible to operate in finage a different radial part of the stator and rotor blades of the high-pressure turbine 20.Furthermore, the radial shift of the hottest point at the chamber outlet can also help to improve the performance of the turbomachine by reducing the clearances between the rotor and stator parts. In fact, by shifting the hot point radially inwards, this promotes the closing of the clearance by balancing the thermomechanical movements.

[0028] The first series of orifices 26a could comprise the same number of orifices 26b as the second series of orifices. It would also be possible to have a different number of orifices between the first series and the second series provided that the effective section between said two series is identical.

[0029] According to the present document, the means for opening / closing said series or rows of orifices comprise at least one ring 28 with a longitudinal axis which is arranged outside the casing 26 ([Fig. 3]). This ring 28 is connected to a plurality of connecting rods 30 articulated in rotation on the ring 28 at a first end and secured to a cam 32 at a second end. Each cam 32 comprises a rod 34 capable of rotating about its axis A. The external peripheral surface of the cam 32 has a non-circular shape relative to the axis A. The peripheral surface may be elliptical, for example, as shown in [Fig. 3]. In this way, the rotation of the cam 32 makes it possible to achieve a radial displacement of a support 36. In practice, all the cams 32 cooperate with a first radially external surface 38 of the support 36, a second opposite surface of the support comprising a first series of rods 40a and a second series of rods 40b. The rods 40a each carry a member 42a for closing the orifices of the first series or first row 26a. The rods 40b each carry a member 42b for closing the orifices of the second series or second row 26b.

[0030] As shown in [Fig. 3], the ring is actuated in rotation about the longitudinal axis L by means of a jack 4L. [Fig. 2] illustrates the support in contact with the cams 32 at a first end which carry for example the first rods 40a. The support comprises a pivot about which the support can pivot between a first position in which the orifices of the first series of orifices 26a are in the open state and the orifices of the second series of orifices 26b are in the closed state and a second position in which the orifices 26a of the first series of orifices are in the closed state and the orifices 26b of the second series of orifices are in the open state.

[0031] In order for the contact between the cams 32 and the support 36 to be permanent, it is possible to use return means 44 such as for example a spring compressed between the second surface 40 of the support and an external face of the casing 26. In this way, the spring stresses the support so as to always force the support to be positioned in the second position (illustrated in [Fig.2]).

[0032] In operation, the jack 41 actuates the movement of the ring 28 which authorizes the rotation of the cams 32 by means of the connecting rods 30, the cams actuating the movement of the support 36 and consequently the movement of the rods 40a, 40b and therefore effects the opening / closing of the orifices 26a, 26b.

[0033] In another embodiment of the invention shown in [Fig.4], it would still be possible to control the movement of each closure member by means of a dedicated jack 41. It would also be possible to carry out this control by means of an electric motor.

Claims

Claims

1. Combustion chamber (18) for a turbomachine with a longitudinal axis (L) comprising an outer annular wall (24) and an inner annular wall connected by an annular chamber end wall, at least one of the inner and outer annular walls (24) comprising dilution orifices, said dilution orifices (26a, 26b) comprising at least a first series of orifices (26a) and a second series of orifices (26b) and means for opening / closing the orifices (26a, 26b) of said first and second series of orifices so as to selectively allow the passage of air into the orifices of only one of the first series of orifices (26a) and the second series of orifices (26b), the effective section of the orifices of the first series of orifices being equal to the effective section of the orifices of the second series of orifices.

2. The combustion chamber of claim 1, wherein said first series of orifices comprises a first annular row of upstream orifices and said second series of orifices comprises a second annular row of downstream orifices.

3. Combustion chamber according to claim 1 or 2, wherein the means for opening / closing said series of orifices comprise at least one ring (28) of longitudinal axis (L) connected to a plurality of connecting rods (28) each connected to a cam (32) whose periphery is in contact with an actuator (36) for simultaneous opening / closing of the orifices of the first series of orifices (26a) and of the orifices (26b) of the second series.

4. Combustion chamber according to claim 3, in which the actuator comprises a support (36) rotatably articulated between a first position in which the orifices of the first series of orifices (26a) are in the open state and the orifices (26b) of the second series of orifices are in the closed state and a second position in which the orifices of the first series of orifices are in the closed state and the orifices of the second series of orifices are in the open state.

5. Combustion chamber according to claim 4, in which return means make permanent contact of the support (36) with the cams (32).

6. Combustion chamber according to one of the preceding claims, in which the opening / closing of the orifices (26a, 26b) of the first series and of the second series are controlled by an electrical device.

7. Turbomachine comprising a combustion chamber according to one of the preceding claims.

8. Method of using the combustion chamber according to one of claims 1 to 6 or the turbomachine according to claim 7, comprising a step of selecting the opening of the orifices of one of the first and second series of orifices (26a, 26b) as a function of a thermodynamic parameter of the combustion chamber and / or a parameter of the turbomachine intended to comprise said combustion chamber.

Images