FR3039220A1 - POSTCOMBUSTION DIPOSITIVE FOR TURBOREACTOR - Google Patents

Abstract

The invention relates to the field of afterburner devices, and particularly to a turbojet afterburner device (2) comprising an afterburner chamber (20) open downstream, a fuel injection ramp (15) located in said turbojet engine afterburner chamber (20). afterburner (20), adapted to be connected to a fuel source, and having a plurality of fuel injection ports, and a spark plug (17) at least one end of which is located in a region of said chamber post-combustion (20). The device (2) further comprises at least one nozzle (14) connected to the fuel injection ramp (15), and configured to inject fuel, in a plurality of directions each having at least one axial component, a radial component and a tangential component with respect to a central axis (X) of said nozzle, towards the region of the afterburner chamber in which is located the end of the spark plug (17).

Description

Background of the invention

The present invention relates to the field of afterburner devices for turbojet engines.

In the technical field of aeronautical propulsion, the term "turbojet engine" comprises a gas generating group and a nozzle for producing a thrust in response to the acceleration, in this nozzle, of high enthalpy combustion gas generated by the gas generating group. By "gas generator group" is meant, in this context, an assembly comprising at least one compressor for compressing a primary flow of atmospheric air, a combustion chamber for burning a fuel in this primary flow after passing through the compressor of to generate, in this primary flow, high enthalpy combustion gases, and at least a first turbine, coupled to the compressor, wherein this primary flow comprising high enthalpy combustion gases is partially expanded to generate energy mechanical mechanism for operating the compressor. In the following description, the terms "upstream" and "downstream" are defined relative to the direction of normal circulation of the air through the turbojet engine.

Among the turbojet engines, it is also possible to include so-called "double-flow" turbojets, also comprising a fan, coupled to a second turbine of the gas generator unit for its actuation, and an annular casing separating the primary flow passing through the gas generating group. a secondary air flow accelerated by the blower and bypassing the gas generating group. Compared to single-flow turbojets, in which all the air passes through the gas generating group, the turbofan engines generally make it possible to obtain a higher thrust with a lower fuel consumption. The turbofan engines can be characterized in particular by their "dilution ratio", that is to say by the ratio between the mass flow rate of the secondary flow and that of the primary flow. In some turbofan engines with relatively low dilution rates, especially for military use, the primary and secondary streams can mix downstream of the gas generator before relaxing together in a common nozzle.

In some applications, including military, the possibility of temporarily obtaining a boost supplement may be desired, even at the cost of a momentary significant increase in fuel consumption. For this, the single or double flow turbojets may include afterburner devices. The principle of afterburner, in the field of turbojets, is based on the injection and combustion of a fuel supplement, in the primary flow and / or in the secondary flow, directly upstream of the nozzle of the turbojet engine. The additional enthalpy of the gases before their expansion in the nozzle makes it possible to obtain a considerable increase of thrust.

However, ignition of the fuel injected into the afterburner can sometimes be difficult. Such delays or ignition failures can be particularly undesirable precisely in flight situations in which the pilot may wish to activate the afterburner, especially in combat. To counter this problem, it has been proposed in particular in the European patent application EP 1621817 A1, an afterburner comprising a downstream afterburner chamber, a fuel injection ramp, a spark plug, and an aeromechanical ignition nozzle connected to specific means of supplying fuel and located in the afterburner chamber, facing the spark plug. Although effective, this solution may be difficult to integrate into an existing turbojet, since the aeromechanical ignition nozzle has a certain size and requires specific means of fuel supply. Moreover, this solution also introduces a heterogeneity in the fuel distribution, and therefore in the combustion thereof, in the afterburner after ignition. This heterogeneity, which can cause local temperature peaks in the combustion chamber, is generally not desirable.

Object and summary of the invention

The present disclosure aims to remedy these drawbacks, by proposing a turbojet afterburner comprising a downstream post-combustion chamber, a fuel injection ramp, located in said afterburner chamber, capable of being connected to a source of fuel. fuel, and having a plurality of fuel injection orifices, and a spark plug having at least one end located in a region of said afterburner chamber, which allows a rapid and certain ignition of the fuel in the fuel chamber. afterburner, while allowing its integration easier in a turbojet engine.

This object is achieved by the fact that the device further comprises at least one nozzle connected to the fuel injection ramp, and configured to inject fuel, in a plurality of directions each having at least one axial component, a radial component and a component tangential to a central axis of said nozzle, to the region of the afterburner in which is located the end of the spark plug.

Thanks to these arrangements, a good spray of fuel is obtained near the spark plug, which facilitates its ignition, with a jet with a relatively small footprint and powered by the same fuel source as the ramp, which facilitates its integration into a turbojet, and in particular an existing turbojet engine. Moreover, this configuration makes it possible to maintain greater homogeneity in the combustion of the fuel in the afterburner chamber.

To simplify the supply of the nozzle and the ramp, the afterburner may include a fuel supply conduit directly connected to said nozzle, and the fuel injection ramp to be connected to said fuel supply conduit through at least one lateral connection of the nozzle.

In order to protect the ramp against heating, in particular to avoid boiling the fuel inside the ramp, the device may comprise a heat shield around the fuel injection ramp, with openings facing the orifices. fuel injection.

To achieve an even more even distribution of fuel in the afterburner, the afterburner can contain a plurality of nozzles for injecting fuel to the region of the afterburner in which the end of the spark plug is located. .

The afterburner chamber may especially be annular, and more specifically be delimited by a flame holder ring. The afterburner may then also include a plurality of flame-holder arms extending radially inwardly relative to the flame-holder ring, to extend the afterburner into the primary flow of a turbofan engine. .

The present disclosure also relates to a turbofan engine comprising at least one gas generating group, a fan, a nozzle, an annular casing for separating a primary flow passing through the gas generating group from a secondary flow, accelerated by the fan, and which bypasses the gas generating group, and a reheat device as above, located on a downstream end of said annular casing, upstream of the nozzle. The gas generating unit comprises at least one compressor, a combustion chamber, a first turbine coupled to the compressor, and a second turbine to which the fan is coupled.

In order to allow a postcombustion powered by the fresh air of the secondary flow, said afterburner chamber may be located radially outwardly with respect to said annular housing. However, it is also possible to situate it radially inward with respect to said annular housing.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and its advantages will appear better on reading the detailed description which follows, of embodiments shown by way of non-limiting examples. The description refers to the accompanying drawings in which: - Figure 1 is a schematic longitudinal sectional view of a turbofan engine with an afterburner according to a first embodiment; FIG. 2A is a detailed view of the turbojet engine of FIG. 1; FIG. 2B is a detailed view of a turbojet according to an alternative embodiment; FIG. 3A is a partial view, on a transverse plane, of the afterburner device of FIGS. 1 and 2A; FIG. 3B illustrates an afterburner device according to another alternative embodiment; FIG. 3C illustrates yet another alternative embodiment; and FIG. 4 is a partial perspective view of the afterburner of FIGS. 1 and 2A.

Detailed description of the invention

A turbojet engine 1 with double flow, equipped with an afterburner device 2, is illustrated schematically in FIG. 1. Successively in the direction of flow through the turbojet engine 1, this turbojet engine 1 comprises a fan 3, a first compressor 4, a second compressor 5, a combustion chamber 6, a first turbine 7, a second turbine 8, and a nozzle 9.

In the illustrated example, the first turbine 7 is coupled to the second compressor 5 through a first rotary shaft, and the second turbine 8 is coupled to the fan 3 through a second rotary shaft. These two rotary shafts are coaxial.

Downstream of the first compressor 4, the turbojet engine 1 has a bypass through which a secondary air flow can bypass the second compressor 5, the combustion chamber 6, and the first and second turbines 7,8, which together form a generator group gas. An annular casing 10 separates this secondary flow F2 from a primary flow Fl passing through the gas generating group downstream thereof.

Thus, in operation, air admitted upstream of the blower is first accelerated by it, to be subsequently compressed by the first compressor, downstream of which it is divided into a primary flow and a secondary flow. The primary flow air F1 is then compressed again in the second compressor 5, before reaching the combustion chamber 6, in which fuel is injected and burned in this primary flow F1 to generate enthalpy combustion gases. high.

The primary flow Fl then comprising these high enthalpy combustion gases then arrives at the first and second turbines 7,8, in which it is the subject of successive partial relaxation, by which it actuates, through these turbines 7,8 and the corresponding rotary shafts, the compressors 4, 5 and the blower 3.

Downstream of the second turbine 8, the secondary flow F2 is reincorporated to the primary flow Fl, whose enthalpy remains high despite the partial relaxation in the turbines 7,8. Thus, the relaxation and acceleration of the two flows in the nozzle 9 can produce a large reaction thrust.

Although, in the illustrated example, the bypass of the secondary flow is done downstream of a first compressor, it is also possible to make this bypass directly downstream of the fan. Moreover, even if, in the illustrated example, the primary and secondary flows are expelled through the same nozzle, it would also be possible to expel them by separate nozzles.

In some cases, however, one may wish for a temporary boost supplement, even at the cost of significantly higher fuel consumption. For this, the turbojet engine 1 has the afterburner device 2 which is located, in the embodiment of the invention illustrated, on a downstream end of the annular casing 10, upstream of the nozzle 9.

This afterburner device 2 is illustrated in greater detail in FIGS. 2A, 3A and 4. It comprises a supply duct 11, a flame holder ring 12 delimiting an afterburner chamber 20 located, in the illustrated embodiment, in the secondary flow F2, radially outwardly relative to the annular housing 10, radially inwardly extending radial arms 13, into the primary flow Fl, from the flame holder ring 12, a nozzle 14, located in the afterburner chamber 20, and connected directly to the supply duct 11, two fuel injection ramps 15, also located in the afterburner chamber 20, and connected to side connectors on both sides the nozzle 14, so as to be supplied with fuel through the supply duct 11 through the nozzle 14, two heat shields 16, shaped ducts protecting respective fuel injection ramps 14, and a spark plug 17, passing through a wall of the flame holder ring 12 through an orifice 18, so that one end of this spark plug 17 is located in the afterburner chamber 20.

Although in the embodiment illustrated in FIG. 2A, the afterburner chamber 20 is situated radially outside the annular casing 10, so as to initiate the afterburner in the secondary flow F2, which is richer in oxygen than the primary flow, but also colder, it is also conceivable to situate the post-combustion chamber 20 radially inwardly relative to said annular casing 10, as illustrated in Figure 2B so as to initiate the afterburner in the primary flow Fl. flame 12 has a section C, such that the afterburner chamber 20 is open downstream. The wall of the flame holder ring 12 furthermore has air inlet orifices on the upstream side.

Each injection ramp 15 has fuel injection orifices (not shown), distributed around the central axis of the turbojet engine 1, and oriented downstream. In the illustrated illustration mode, these orifices are oblique with respect to the downstream direction. To let the fuel jets injected into the afterburner chamber 20 through these injection ports, the heat shields 16 have wider openings 19 opposite these injection ports.

The nozzle 14 is shaped to inject fuel into the afterburner chamber 20 in a plurality of directions each having an axial component, along a central axis X of the nozzle 14, which in the illustrated embodiment is substantially parallel to the central axis of the turbojet engine 1, but also the radial and tangential components in a plane perpendicular to this central axis X of the nozzle 14. For this, the nozzle 14 comprises ducts twisted about its central axis X for the passage of fuel. By effectively spraying the fuel through the nozzle 14, the ignition when conducting an electrical discharge between the electrodes of the spark plug 17 inside the afterburner chamber 20 is thus facilitated.

Furthermore, the nozzle 14 is located near the spark plug 17, upstream thereof, so as to inject the fuel into the region of the afterburner chamber 20 in which the spark plug 17 is located . The nozzle 14 may be slightly offset laterally with respect to the spark plug 17, as illustrated in Figures 3A and 4, or aligned therewith, as shown in Figure 3B. Moreover, although in these two embodiments the afterburner device has only one nozzle, it is also conceivable to have a plurality of nozzles for injecting fuel to the region of the afterburner chamber in which is located at the end of the spark plug, as in the embodiment illustrated in Figure 3C with two nozzles 14 located on one side and the other side of the spark plug 17.

Although the present invention has been described with reference to specific exemplary embodiments, it is obvious that various modifications and changes can be made to these examples without departing from the general scope of the invention as defined by the claims. In particular, the individual features of these embodiments can be combined without departing from the general scope of the invention. The invention is also in no way limited in its application to turbofan engines only, but would also be applicable to single-flow turbojets. Therefore, the description and drawings should be considered in an illustrative rather than restrictive sense.

Claims (10)

A turbojet afterburner (2) comprising: an afterburner chamber (20) open downstream, a fuel injection ramp (15) located in said afterburner chamber (20), capable of being connected to a fuel source, and having a plurality of fuel injection ports, and a spark plug (17) at least one end of which is located in a region of said afterburner (20), characterized in that the device (2) further comprises at least one nozzle (14) connected to the fuel injection ramp (15), and configured to inject fuel, in a plurality of directions each having at least one axial component, a radial component and a tangential component with respect to a central axis (X) of said nozzle, towards the region of the afterburner chamber in which is located the end of the spark plug (17). An afterburner (2) according to claim 1, comprising a fuel supply conduit (11) directly connected to said nozzle (14), the fuel injection ramp (15) being connected to said fuel pipe (11). fuel supply through at least one side connection of the nozzle (14). 3. Afterburner device (2) according to any one of the preceding claims, comprising a heat shield (16) around the fuel injection ramp (15), with openings (19) facing the injection orifices. fuel. An afterburner (2) according to any one of the preceding claims comprising a plurality of nozzles (14) for injecting fuel to the region of the afterburner chamber (20) in which the end of the candle is located ignition (17). The afterburner (2) according to any one of the preceding claims, wherein the afterburner (20) is annular. The afterburner (2) according to claim 5, wherein said afterburner (20) is defined by a flame holder ring (12). The afterburner (2) of claim 6, further comprising a plurality of flame holder arms (13) extending radially inwardly relative to the flame holder ring (12). 8. Turbojet engine (1) comprising at least: a gas generator group with at least one compressor (5), a combustion chamber (6), a first turbine (7) coupled to the compressor (5), and a second turbine (8); a blower (3) coupled to the second turbine (8); a nozzle (9); an annular casing (10) for separating a primary flow (F1) passing through the gas generating group from a secondary flow (F2), accelerated by the blower (3), and which bypasses the gas generating group; and an afterburner (2) according to any one of the preceding claims, located on a downstream end of said annular casing (10), upstream of the nozzle (9). 9. Turbojet engine (1) according to claim 8, wherein said afterburner (20) is located radially outwardly relative to said annular housing (10). 10. Turbojet engine (1) according to claim 8, wherein said afterburner (20) is located radially inwardly relative to said annular housing (10).