Assembly for injecting an air-and-fuel mixture into the combustion chamber of an aircraft turbine engine

Abstract

The invention relates to an assembly (31) for injecting an air-and-fuel mixture into a combustion chamber (8) of an aircraft turbine engine, the assembly comprising: - a first entity (31a) comprising a bowl (40) for diffusing an air-and-fuel mixture, the bowl being intended to be attached to a chamber bottom (18) of the combustion chamber, the first entity (31a) also comprising a first annular swirler (64) for directing air toward the bowl (40); - a second entity (31b) comprising a fuel injector head (21) and a guiding device (87) for guiding the injector head, this second entity comprising a second annular swirler (74) for directing air. According to the invention, the first and second entities (31a, 31b) are mounted one on top of the other by means of a mounting system (95) that allows radial sliding between the first and second entities.

Description

[0001] DESCRIPTION

[0002] Title: Enhanced performance assembly for injecting an air-fuel mixture into the combustion chamber of an aircraft turbomachine

[0003] TECHNICAL FIELD

[0004] The present invention relates to the field of combustion chambers for aircraft turbomachinery, preferably for turbojet engines.

[0005] It relates more specifically to assemblies for injecting a mixture of air and fuel into the combustion chamber, this type of assembly generally including a fuel injector, as well as an injection system receiving this injector.

[0006] STATE OF PRIOR ART

[0007] Such systems for injecting an air-fuel mixture have already been the subject of numerous developments. Their design is constantly being optimized to improve their performance, for example, in ground ignition, high-altitude reignition, and fire suppression. Efforts are also being made to minimize pollution, which is closely linked to the injection system's ability to atomize and mix the injected fuel with air. Such injection systems are described in documents FR 2 875 585 Al, FR 2 685452 Al, FR 2832493 Al, and FR 3 043 173 Al.

[0008] Typically, such an assembly includes an injector, working with an injection system that mixes air with the fuel sprayed by the injector. The injection system is then mounted on the bottom of the combustion chamber, which it passes through.

[0009] Each assembly typically includes two air intake swirls, known as "swirlers." In the first type of assembly, called an aerodynamic injector, one swirl is located on the injection system, and the other on the injector head. In the second type, called an aeromechanical injector, both swirls are located on the injection system that receives the injector. In all cases, the number of swirls on the injection system can be greater than one. Each swirl injects air with a circumferential component, creating a rotating airflow that promotes fuel mixing and atomization. This, in particular, increases the residence time of the hot gases, thus improving mixing.

[0010] Ideally, the fuel injector, the injection system, and the associated combustion chamber bottom port should be perfectly aligned and securely fastened to one another. However, achieving this is extremely difficult, and mounting systems are usually designed to provide one or more degrees of freedom of movement between the aforementioned components. In particular, a floating mounting of the injection system on the combustion chamber bottom is often used, allowing radial sliding between these two elements. This type of mounting provides a radial sliding plane between the injection system and the combustion chamber bottom, which not only accommodates mounting clearances but also manages differential thermal expansion between these parts subjected to very different temperatures, and absorbs vibrations.In this regard, it is noted that the fuel injector is usually mounted via a mast on the turbomachine housing, which is subject to much lower temperatures than the combustion chamber.

[0011] This degree of freedom of movement, while useful for the reasons outlined above, has nevertheless been identified as a source of performance losses. In particular, it is likely to increase pollutant emissions, reduce combustion stability and reignition capability, and finally, affect the lifespan of a deflector integrated into the injection system and forming a thermal shield located downstream of the combustion chamber bottom. Regarding this last point, it has been noted that radial movement of the deflector relative to the combustion chamber bottom can lead to deflector eccentricity, with a portion of its inner periphery no longer, or less, exposed to the cooling provided by dedicated vents through the chamber bottom. This loss of cooling exposes the affected portion of the deflector to higher temperatures, thus impacting its lifespan. DESCRIPTION OF THE INVENTION

[0012] To address at least partially the aforementioned drawbacks relating to prior art achievements, the invention first of all relates to an assembly for injecting a mixture of air and fuel into a combustion chamber of an aircraft turbomachine, the assembly having the characteristics of claim 1.

[0013] The invention thus differs from prior solutions by providing a degree of radial freedom of movement in a sliding plane arranged between the two air intake spirals, belonging respectively to the two aforementioned entities of the assembly. This particular design offers significant performance gains, notably by reducing pollutant emissions and increasing combustion stability as well as reignition capability.

[0014] Indeed, this design allows the first component, including the diffuser bowl, to be fixed to the bottom of the combustion chamber. The absence of any degree of freedom of movement between these two elements, especially radially, ensures that the bowl remains centered relative to the associated opening in the bottom of the combustion chamber, and therefore guarantees a perfectly axisymmetric injection of the air-fuel mixture into the chamber.

[0015] Furthermore, the design also maintains the centering of the second air inlet spiral relative to the injector head, as both elements are integrated into the same second unit of the assembly according to the invention. Thus, the fuel spray remains perfectly centered in the central recirculation zone supplied with air by the first spiral, and the mixed flow exiting the diffuser bowl is also perfectly centered relative to the bottom chamber opening to which this bowl is attached.

[0016] This results in improved aerodynamic performance, as well as an axisymmetric and homogeneous fuel distribution, despite any radial movement between the two entities of the assembly according to the invention.

[0017] Finally, if a deflector is present on the first component intended to be fixed to the combustion chamber floor, the cooling of this deflector by the chamber floor is not affected in any way by any radial relative movements between the two components of the assembly. Furthermore, thanks to the flange projecting radially outwards, axially opposite an inner portion of the deflector, the cooling air introduced into the space between this flange and the deflector is better channeled. Moreover, in the case of the invention concerning an aeromechanical injector, the second part of the injection system includes, downstream of the first, an annular body forming an internal venturi. With this design, the injector nozzle remains centered relative to the venturi despite relative movements between the parts of the injection system, which can provide increased performance of the injection system.

[0018] The invention preferably has at least one of the following optional features, taken individually or in combination.

[0019] According to the invention, the first entity comprises an annular deflector for thermal protection of the chamber bottom, this deflector preferably being made in one piece with the diffusion bowl. A separate solution for this deflector is also conceivable, for example by creating a welded assembly.

[0020] Preferably, each of the first and second air introduction twists is a radial twist, or axial twist, or a twist with axial and radial components.

[0021] Preferably, the first air inlet screw is located radially outwards relative to the second air inlet screw, and preferably downstream of the latter.

[0022] The invention also relates to a combustion module for an aircraft turbomachine, comprising a combustion chamber equipped with a chamber bottom, the module further comprising several assemblies such as that described above, these assemblies being circumferentially spaced from each other, and each passing through the chamber bottom by being fixed to it.

[0023] Finally, the invention relates to an aircraft turbomachine, comprising such a combustion module, the turbomachine preferably being a turbojet or a turboprop.

[0024] Other advantages and features of the invention will become apparent in the detailed, non-limiting description below. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] This description will be made with reference to the attached drawings, among which are;

[0026] [Fig. 1] is a schematic longitudinal cross-sectional view of a turbojet engine according to the invention;

[0027] [Fig. 2] represents a longitudinal half-section view of a combustion module of the turbojet engine shown in the previous figure;

[0028] [Fig. 3] is a more detailed view in longitudinal half-section of one of the injection assemblies of the combustion module, according to a first embodiment not covered by the invention;

[0029] [Fig. 4] is a view similar to that of the previous figure, with the injection assembly presented as an alternative;

[0030] [Fig. 4A] is a view similar to that of the previous figure, showing the cooling of the deflector;

[0031] [Fig. 5] is a longitudinal cross-sectional view of one of the injection assemblies of the combustion module, according to a second preferred embodiment of the invention;

[0032] [Fig. 6] is a longitudinal sectional view similar to the previous one, according to an alternative.

[0033] DETAILED EXPLANATION OF PREFERRED METHODS OF IMPLEMENTATION

[0034] With reference first to Figure 1, an aircraft turbomachine 1, according to the invention, is shown. This is a twin-spool, turbofan engine. However, it could be a turbomachine of another type, for example a turboprop, without departing from the scope of the invention.

[0035] The turbomachine 1 has a longitudinal axis 3 around which its various components extend. From upstream to downstream along the main direction of gas flow through the turbomachine, it comprises a fan 2, a low-pressure compressor 4, a high-pressure compressor 6, a combustion chamber 8 integrated into a combustion module 9, a high-pressure turbine 10, and a low-pressure turbine 12. Conventionally, this turbomachine 1 is controlled by a control unit 13, shown schematically only. This unit 13 allows, in particular, the control of the various operating points of the turbomachine. A portion of the combustion module 9 is shown in more detail in Figure 2.Its combustion chamber 8 has, in particular, an outer ring 14 centered on axis 3, an inner ring 16 also centered on this same axis, and a chamber bottom 18 connecting the two rings at their upstream end. This chamber bottom is annular and centered on axis 3. Fuel injectors 20 are regularly distributed on the chamber bottom in a circumferential direction (only one injector is visible in Figure 2). Each of these injectors has an injector nozzle 21, also called an injector head, centered on a central injection axis 22 slightly inclined with respect to axis 3. In this regard, it is noted that this injection axis 22 is parallel or substantially parallel to the main flow direction of the stream 24 through the chamber. In the remainder of this description, unless otherwise indicated, the terms "upstream" and "downstream" will be used in relation to this main flow direction 24.

[0036] Each injector 20 is associated with an injection system 30, shown schematically in Figure 2. Together they form an assembly 31 to inject a mixture of air and fuel into the combustion chamber, several preferred embodiments of which will be described later.

[0037] The injection system 30 cooperates upstream with the injector head 21, while downstream it opens into the combustion chamber 8, passing through an opening 32 through the bottom of the chamber 18. Thus, on this chamber, several openings 32 are provided, spaced circumferentially from each other with respect to the axis 3, and each associated with an injection system 30, itself belonging to an assembly 31 specific to the present invention.

[0038] The combustion chamber 8, and each injection system 30, are supplied with pressurized air in the direction of arrow 48 via a passage 46 shown in Figure 2. This passage allows the pressurized air to enter from the high-pressure compressor located further upstream within the turbomachine. This pressurized air is used for combustion and cooling of the combustion chamber 8. Some of this air is introduced into the combustion chamber 8 through the central opening of a cowling 50, through which the injector 20 passes. Another portion of the air flows towards the airflow passages 51 and 53, respectively in directions 54 and 56, and then in direction 60. The airflow, schematically represented by arrows 60, then enters the combustion chamber 8 through primary orifices, dilution orifices, and cooling elements (multi-perforations, cooling films, etc.).

[0039] Part of the air from the flow along the arrows 52 feeds each injection assembly 31, one of which will now be described in more detail with reference to Figure 3, representing a first embodiment, not covered by the invention, but some parts of which can be integrated into it, as will be detailed below.

[0040] It is noted that several of the 31 assemblies of the combustion module 9 may have an identical design, or even all of them.

[0041] In this first mode, injector 20 is of the aerodynamic type, one of whose specific features is to integrate an air introduction spiral, as will be detailed below. The injection system 30 first includes a body 62 equipped with a first air inlet auger 64, supplied with air by a portion 52' of the flow 52. It is also called the external air auger, in that it has a larger diameter than the air auger integrated into the injector 20. This auger 64 is axial, so that the air enters axially at the inlet of the auger, and it also exits axially with a circumferential component, applied by the twisting of the vanes that make up this auger 64. Alternatively, it could be a radial auger or a auger with two axial and radial components, always in addition to the circumferential component at the outlet of this auger.

[0042] The first air introduction spiral 64 is centered on a central axis 22' of the injection device 30, this axis 22' being coincident or substantially coincident with the central axis 22 of the injector 20. It is noted that due to the radial movement capability between the injector head 21 and the injection system 30, small offsets remain possible between these axes 22, 22', which preferentially remain parallel or substantially parallel.

[0043] The first air spiral 64 opens into an annular channel 66, delimited externally by a conical wall 67 converging downstream of the body 62, and internally by another conical wall 69 also converging downstream of the body 62, and called a tab, or section control tab. This tab 69 remains optional.

[0044] The downstream end of this channel 66 opens into a diffusion bowl 40 extending from the conical wall 67, designed for the diffusion of an air-fuel mixture into the chamber. The diffusion bowl 40 has a diverging shape downstream and is also centered on the axis 22'. At its downstream end, it is equipped with an annular row of holes 71, dedicated to introducing air into the combustion chamber of the chamber 8. Near these holes 71, the bowl 40 has a downstream end in the form of a collar 73, projecting radially outwards. As is known, this is part of the injection system 30 to which the flame, inside the chamber 8, adheres.

[0045] This collar 73 is positioned downstream and axially opposite an inner portion of an annular deflector 75, thermally protecting the bottom of the chamber 18 by covering it downstream. Cooling holes 79 are preferably made through the bottom of the chamber 18, so that a cooling airflow 81 passes through them and then impacts the upstream surface of the deflector 75.

[0046] A mounting flange 68 extends substantially axially upstream from the downstream end of the bowl 40. At one downstream end of this flange 68, another annular row of holes 71 is made, so that a cooling airflow 83 opens between the collar 73 and the deflector 75, in order to cool the downstream surface of this deflector.

[0047] The upstream end of the flange 68 is fixed to the bottom of the chamber 18, passing, for example, through the opening 32. This opening is centered on a central axis 22", coinciding with the axis 22' of the first helix 64. The fixing is such that it preferentially prevents any movement between the bottom opening of the chamber 32 and the injection system 30, and in particular radial movement between these parts. Consequently, regardless of the mounting clearances of the parts of the assembly 31 and the differential thermal expansions during operation, the two central axes 22', 22" remain preferentially aligned.

[0048] The injection system 30 can be made entirely or partially from a single piece, i.e., as a single unit. The elements that can be integrated within this single piece, for example obtained by molding, correspond to several or all of the following elements: the auger 64, the walls 67, 69, the bowl 40 and its collar 73, the deflector 75, and the fixing flange 68.

[0049] Upstream, the injection system 30 terminates with a mounting flange 85, used for the radially floating mounting of a guide device 87 for the injector head 21. To this end, at its upstream end, the mounting flange 85 forms an annular groove 89 centered on the axis 22', opening radially inward relative to this same axis 22'. All or part of this flange 85 can be made from the aforementioned single piece, forming the remainder of the injection system. To simplify the mounting of the guide device 87, the groove 89 can be formed by two flange pieces mounted one on top of the other, for example by screwing, in a manner identical or similar to that shown in the second embodiment.

[0050] The groove 89 receives a radial flange 91 of the guide device 87, this upstream flange 91 projecting radially outwards from a guide body of the device 87, the latter also being called a sliding cross-section. Indeed, the injector head 21 can move freely relative to the sliding cross-section 87, along the direction of the central axis 22''' of this cross-section. A pivoting movement of this head 21 is also possible within the sliding cross-section 87. However, since the sliding cross-section 87 is attached to the injector head 21, the assembly is not free to float in the plane orthogonal to the central axis 22''", so it is considered that the sliding cross-section 87 and the injector head 21 move as a unit in the radial direction, relative to the axis 22''' of the cross-section. The central axis 2" of the sliding cross member 87 is coincident or substantially coincident with the central axis 22 of the injector head.

[0051] The flange 85 forming the groove 89, together with the radial collar 91 of the sliding cross member 87, form a mounting system 95 allowing radial sliding between the cross member 87 and the injection system 30. This is therefore a radially floating mounting in a plane orthogonal to the axes 22', 22'", which are either coincident or parallel in the event of movement of the collar 91 within the groove 89. The mounting system 95 is configured to allow only this relative movement between these two parts 85. More generally, the mounting system 95 allows such radial sliding between a first entity 31a and a second entity 31b of the injection assembly 31. In this first preferred embodiment of the invention, the first entity 31a is formed by the entire injection system 30, fixed in the opening 32 of the bottom of the chamber 18.The second entity 31b is formed by the sliding cross member 87 and the injector head 21, or even by the entire injector 20.

[0052] Regarding this injector 20, its head 21 comprises a body 70 defining a first cylindrical space 72, centered on the axis 22. This first space 72 is dedicated to the circulation of air from the flow 52. To this end, the body 70 includes a second air inlet spiral 74, also called an internal spiral, in that it is located radially inward relative to the first spiral 64 of the injection system 30. It is also arranged upstream of the first spiral 64, and as can be seen from the above, this second spiral 74 of the injector head 21 is an integral part of the second entity 31b of the assembly 31. The vanes that form the second spiral 74 are distributed circumferentially around the axis 22. Another portion 52' of the air flow 52 passes through these vanes 76 oriented generally radially, to give rise to an airflow 77 traveling within the first space 72.The blades are also inclined circumferentially, so as to create a rotation of the airflow 77 around axis 22, that is to say, a swirling airflow 77. The second twist 74 could alternatively be axial, or have axial and radial components, always in addition to the circumferential component at the exit of this twist.

[0053] The first space 72 is delimited by an upstream end 78 and remains open downstream. The lateral wall forming space 72 has an upstream portion at which the auger blades 74 open, while its downstream portion consists of an annular wall 80 centered on axis 22. This annular wall 80 is preferably cylindrical, with a circular cross-section. It therefore internally delimits a downstream portion of the first space 72 and externally delimits a second annular space 82 centered on axis 22. This second annular space 82 is an integral part of a fuel circuit and is jointly delimited with a downstream end element 84 attached to the body 70. The second space 82 is thus situated around the first space 72.The first and second spaces 72, 82 are delimited downstream by the downstream end of the annular wall 80, from which these two spaces 72, 82 open into a third space 86 for the air-fuel mixture. This third space 86 extends to the curved upstream end of the bowl 40, and to the downstream end of the tab 69.

[0054] The fuel circuit also includes fuel supply means located upstream of the annular space 82. These means include, in particular, fuel channels 93 running through the injector body 70, spaced circumferentially from one another. They extend around the first space 72 and pass through solid portions of the second spiral 74. The downstream end of these channels 93 supplies fuel to the second space 82. Although not shown, the fuel circuit may also include a central fuel injection into the first space 72 from the bottom 78.

[0055] With this design, the mixed flow 77 of air and fuel which is ejected from the third space 86 is once again atomized in the bowl 40, by the air coming from the first spin 64.

[0056] Figure 4 represents an alternative, in which the first air inlet screw 64 is of two-component design, axial and radial, always in relation to the central axis 22' on which this screw 64 is centered. In this alternative, a circlip 97 is also shown for fixing the flange 68 to the bottom of the chamber 18, this circlip being preferably provided upstream of the bottom of the chamber, and the flange 68 passing through the opening 32 provided on this bottom of the chamber.

[0057] Figure 4A shows the possibility of cooling the deflector 75, preferably by impact, using cooling air passing through orifices 94 made through the bottom of chamber 18. Pins 98, spaced circumferentially from each other and projecting axially upstream from the deflector 75, bear against the downstream surface of the bottom of chamber 18.

[0058] Figure 5 shows an injection assembly 31 according to a second embodiment specific to the invention. In this second embodiment, the injector 20 is of the aeromechanical type, and its injector head 21 is therefore housed in a sliding passage 87 belonging to the injection system 30, the latter incorporating the two air inlet spirals 64, 74. In this second embodiment, one of the principles of the invention already described in the first embodiment is implemented, namely that the mounting system 95 allows radial sliding between the first and second entities 31a, 31b. However, the embodiment of the injection system 30 and of the entities 31a, 31b differs from that of the first embodiment described above, as will be described below.

[0059] Indeed, the mounting system 95, offering the desired degree of freedom of movement in the radial direction, is here integrated within the injection system 30 itself, made in two parts which are therefore floating relative to each other in a plane orthogonal to the central axis 22' of the first spiral 64.

[0060] The first part 30a of the injection system 30 consists of elements identical or similar to all the constituent elements of the injection system 30 of the first embodiment described previously. This first part 30a of the injection system 30 forms the first entity 31a of the injection assembly 31 of the second embodiment.

[0061] The second part 30b of the injection system, which is preferably also made of a single piece, has an upstream end formed by the sliding passage 87, which receives the injector head 21. At the downstream exit of this passage 87, the second part 30b has the second air introduction spiral 74, which is located upstream of the first spiral 64, and radially inwards with respect to the latter. The second spiral 74, also radial, is extended downstream by an annular body 99, forming internally a venturi which opens into the inside of the bowl 40. The flared downstream part of the venturi is surrounded by the tab 69 of the first part 30a of the injection system 30. Moreover, an air circulation can be provided in the annular space defined between these two elements 69, 99, for the purpose of thermal protection, and of limiting the risks of fuel rising and stagnation in this space.

[0062] Finally, the second part of the injection system 30b comprises the radial flange 91, forming part of the floating mounting system 95. This flange 91 is preferably located downstream of the second helix 74, and preferably made in one piece with the other constituent elements of this second part of the injection system 30b. As mentioned in the first embodiment, Figure 5 shows that the groove 89 of the mounting system 95 is partially delimited by a portion screwed onto the mounting flange 68 of the first part of the injection system 30a.

[0063] In this second preferred embodiment, the two air spirals 64, 74 are radial, but they could alternatively be of a different design, without departing from the scope of the invention.

[0064] The second entity 31b, which is therefore floating relative to the first entity 31a in the radial direction relative to the axis 22' of the first spiral 64, is here formed by the second part of the injection system 30b, and by the injector head 21 received non-floating radially in the sliding cross 87.

[0065] In this second embodiment specific to the invention, the deflector 75 can be implemented within the first part of the injection system 30a, in a manner identical or similar to that described in the first embodiment of the invention. More precisely, the first entity 31a is arranged to include the annular deflector 75, for the thermal protection of the bottom of the chamber 18. This deflector is preferably made in one piece with the diffusion bowl 40. Furthermore, the bowl 40 has its downstream end 73 in the form of a collar projecting radially outwards, axially opposite the inner part of the deflector 75.Furthermore, at a downstream end of the flange 68 which extends axially or substantially axially upstream from the downstream end of the bowl 40, there is provided the annular row of holes 71 through this flange 68, so that a cooling airflow 83 may open between the collar 73 and the deflector 75, in order to cool the downstream surface of this deflector.

[0066] Conventionally, in the case of an air-injector, the fuel jet introduced by this injector 20 into the injection system 30 is first atomized by air from the second auger 74, and then by air from the first auger 64. The principle specific to the invention therefore consists of providing a degree of radial freedom of movement in a sliding plane arranged between the two air-induction augers 64 and 74, belonging respectively to the two entities 31a and 31b of the air-injector assembly 31. This design increases performance, notably by reducing pollutant emissions, and by enhancing combustion stability as well as the reignition capability of the combustion chamber.

[0067] Indeed, this design allows the first entity 31a, including the air-fuel mixture diffusion bowl 40, to be fixed to the bottom of the chamber 18. The absence of degrees of freedom of movement between these two elements 18, 40, especially radially with respect to the axis 22" of the opening 32 through this bottom of the chamber, makes it possible to maintain the permanent centering of the bowl 40 with respect to this opening 32 of the bottom of the combustion chamber 18. This guarantees a perfectly axisymmetric injection of the mixed air-fuel flow into the combustion chamber 8.

[0068] In addition, the design also allows for the permanent centering of the second air inlet spiral 74 belonging to the second entity 31b, relative to the injector head 21. Indeed, these two elements are integrated into the same second entity 31b of the injection assembly 31, an entity within which there is also no radially floating mounting between the parts that compose it.

[0069] Thus, the fuel spray remains perfectly centered in the central recirculation zone, formed by the first space 72 within the injector head in the first mode, and by the interior of the venturi 99 of the injection system 30 in the second mode. Furthermore, the mixed flow injected from the bowl 40 into the chamber 8 also remains perfectly centered with respect to the bottom opening of the chamber 32.

[0070] In an alternative shown in Figure 6, an annular space 100, radially delimited between the venturi 99 and the concentric conical wall 69, is supplied with air by an annular row of purge holes 101. These holes 101 are made in the material of the second part 30a of the injection system, upstream of the space 100, and opening through or near the radial collar 91. The purge holes 101 thus allow the space 100 forming a "dead" cavity between the two spirals to be supplied with air, for the purpose of thermal protection and to prevent any rising and stagnation of fuel in it.

[0071] Of course, various modifications can be made by a person skilled in the art to the invention just described, by way of non-limiting examples only. In particular, the elements of the different preferred embodiments and their alternatives are combinable and interchangeable, and in this regard, it is noted that in the figures, elements bearing the same numerical references correspond to identical or similar elements.

Claims

DEMANDS 1. Assembly (31) for injecting a mixture of air and fuel into a combustion chamber (8) of an aircraft turbomachine, the assembly comprising: - a first entity (31a) comprising a bowl (40) for diffusing an air-fuel mixture, the bowl being intended to be fixed on a bottom of chamber (18) of the combustion chamber, the first entity (31a) also comprising a first annular screw (64) for introducing air towards the bowl (40); - a second entity (31b) comprising a fuel injector head (21), a guide device (87) for the injector head, this second entity comprising a second annular air inlet auger (74), characterized in that the first and second entities (31a, 31b) are mounted one on top of the other using a mounting system (95) allowing radial sliding between these first and second entities, the first entity (31a) comprising an annular deflector (75) for thermal protection of the bottom of the chamber (18), preferably made in one piece with the diffusion bowl (40), the bowl (40) having a downstream end (73) in the form of a collar projecting radially outwards, axially opposite an inner part of the deflector (75), the assembly comprising a two-part injection system (30), comprising: - a first part of the injection system (30a), forming said first entity (31a); - a second part of the injection system (30b), comprising the injector head guide device (87) of said second entity (31b), as well as the second annular air inlet screw (74), and the second part (30b) of the injection system comprising, downstream of the latter, an annular body (99) forming internally a venturi.

2. Assembly according to claim 1, characterized in that each of the first and second air introduction spirals (64, 74) is a radial spiral, or axial spiral, or a spiral with axial and radial components.

3. Assembly according to any one of the preceding claims, characterized in that the first air inlet screw (64) is located radially outwards with respect to the second air inlet screw (74), and preferably downstream of the latter.

4. Combustion module (9) for aircraft turbomachine, comprising a combustion chamber (8) equipped with a chamber bottom (18), the module further comprising several assemblies (31) according to any one of the preceding claims, circumferentially spaced from each other, and each passing through the chamber bottom (18) by being fixed thereto.

5. Aircraft turbomachine (1), comprising a combustion module (9) according to claim 4.

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