DEVICE FOR GUIDING A MAIN AIR FLOW TO AN AIRCRAFT TURBINE ENGINE

Description

Technical field of the invention

[0001] The present invention relates to a device for driving a main airflow by a secondary airflow, this device being intended to equip an aircraft turbomachine. Technical background

[0002] The technical background includes, in particular, documents FR-A1-3 006 998, US-A-3,694,107, FR-A1-2 541 390, US-A-4,928,480 and US-A1-2021 / 003 095.

[0003] It is known to drive a main airflow by means of a secondary airflow that is more energetic than the main airflow. A main airflow driving device of this type typically comprises a main airflow duct and secondary airflow ejectors located inside the duct and configured to eject the secondary airflow, which will force the main airflow through viscous entrainment in the duct.

[0004] Ejectors, also called jet nozzles, are supplied with high-pressure and / or high-temperature air. The difference in momentum between the two flows generates a viscous entrainment of the lower-pressure main airflow, thus drawing it into the duct. The following prior art documents describe several applications of this type of device: WO-A1-2014 / 060656, FR-A1-3 011 583, FR-A1-3 022 588, and FR-A1-3 087 239.

[0005] One of the challenges with this type of system is controlling turbulence and pressure losses at the ejector outlets, which reduce the system's performance and may necessitate oversizing for a given application. This, in turn, affects the pressure balance between the upstream primary flow, the secondary flow, and the downstream exhaust of the system.

[0006] When the pressure upstream of the device decreases and / or the pressure losses and turbulence at the ejector outlets become too high, the generated suction effect loses its effectiveness. At a certain pressure loss threshold upstream of the system, generated by the intake device, the main airflow reverses and the secondary airflow is drawn back upstream, which can damage the parts in that area.

[0007] The invention proposes an improvement to this technology through the exhaust of the system which has the effect of better channeling the jets of the ejectors allowing to reduce turbulence and pressure losses at the outlet of the latter, thus making it more robust to pressure losses upstream of the system. Summary of the invention

[0008] The invention relates to a device for driving a main airflow for an aircraft turbomachine, this device comprising: a first main airflow duct, this first duct having a main axis, a plurality of secondary airflow ejectors located inside the first duct and configured to eject a secondary airflow and force the main airflow into this first duct, said ejectors being distributed around said main axis on a tubular wall at one end of the first duct, and a second exhaust duct located at the outlet of the ejectors and having an end which is connected to the end of the first duct and which directly receives said secondary flow to force the main airflow from the first duct to the second duct, characterized in that the end of the second pipe is engaged in the end of the first pipe and includes a restriction which is at least partly located in that end of the first pipe.

[0009] The inventors have demonstrated that the center of the exhaust pipe is conducive to aerodynamic recirculations and fluid re-aspirations leading, after a certain pressure loss threshold upstream of the system, to a reversal of flows.

[0010] Rather than filling the center of this pipe, the inventors propose forcing the primary and secondary flows to the center of the pipe. To achieve this, the exhaust pipe includes a constriction.

[0011] In this application, "constriction" refers to a transverse narrowing of the second pipe that reduces its cross-sectional area. A constriction is therefore characterized by a narrowing of the pipe and is uniform around its entire circumference. The aim is to channel the primary and secondary flows through a restricted section, thereby limiting the risk of turbulence and recirculation in that area.

[0012] The device according to the invention may comprise one or more of the following features, taken individually or in combination with each other: -- the ejectors are at least three in number and preferably at least five; said restriction represents a reduction of the passage section of between 10 and 90%, preferably between 30 and 70%, and more preferably of the order of 50%;said restriction comprises: -- an intermediate section having a cross-section Smin, -- an upstream section having at an upstream end a cross-section Smax or Smax1 substantially identical to the cross-section of the first pipe, and at a downstream end a cross-section Smin which is less than Smax, and -- a downstream section located between the intermediate section and the rest of the second pipe, this downstream section having at an upstream end a cross-section Smin, and at a downstream end a cross-section Smax substantially identical to the cross-section of the first pipe or a cross-section Smax2 between Smin and Smax1, and in which the upstream section has a length L1 or axial dimension less than or equal to a length L2 or axial dimension of the downstream section; L2 = K.L1 with K between 1 and 10, and preferably between 3 and 5;The end of the second conduit includes a peripheral edge that is flush with the tubular wall of the first conduit; the end of the second conduit includes a peripheral edge that extends in a plane perpendicular to said principal axis, said plane passing through or upstream of ejector outlets; said plane passes upstream of these outlets and said peripheral edge includes notches configured to receive each of the bases of one of said ejectors; said second conduit has a generally straight or angled shape; said second conduit has a generally non-circular cross-section; alternatively, this cross-section may be circular; said second conduit is formed of a single piece, preferably of metal.

[0013] The invention further relates to a turbomachine, in particular for aircraft, comprising a device as described above.

[0014] The invention further relates to a helicopter comprising a device or turbomachine as described above.

[0015] Advantageously, the turbomachine comprises, from upstream to downstream, in the direction of gas flow in the turbomachine, an air inlet, at least one compressor, a combustion chamber, at least one turbine and an exhaust, said air inlet being equipped with a particle trap which is connected to said device. Brief description of the figures

[0016] Other features and advantages will become apparent from the following description of a non-limiting embodiment of the invention with reference to the accompanying drawings in which: [ Fig.1 ] there figure 1 is a very schematic view of a main airflow drive device for an aircraft turbomachine; Fig. 2 ] there figure 2is a schematic axial cross-sectional view of an aircraft turbomachine equipped with a device of the type of that of the figure 1 ; Fig.3 ] there figure 3 is a schematic perspective and axial cross-sectional view of a main airflow drive device, according to the prior art to the present invention; [ Fig. 4 ] there figure 4 is a schematic perspective view of a main airflow drive device, according to an embodiment of the invention; [ Fig. 5 ] there figure 5 is a larger-scale view of part of the device of the figure 4 ; And [ Fig. 6 ] there figure 6 is a cross-sectional view along line VI-VI of the figure 4 . Detailed description of the invention

[0017] There figure 1 is a very schematic representation of a device 10 for driving a main airflow F1 by a secondary airflow F2 for an aircraft turbomachine.

[0018] Device 10 includes: a first main airflow duct 12 F1, this first duct having a main axis A, a plurality of secondary airflow ejectors 14 F2, which are located inside the first duct 12 and configured to eject the secondary airflow F2 and force the main airflow F1 into the first duct 12, and a second exhaust duct 16 located at the outlet of the ejectors 14 and connected to the first duct 12.

[0019] The device 10 is generally connected upstream (with reference to the flow of the F1, F2 streams in the device 10) to an enclosure 18, such as a purge enclosure or an enclosure forming a particle trap, of the aircraft turbomachine.

[0020] Device 10 is generally connected downstream to the outside 20 of the turbomachine.

[0021] The first pipe 12 has a generally elongated and straight shape, although this is not a limiting factor. Similarly, the second pipe 16 has a generally elongated and straight shape but can be bent as an alternative.

[0022] The ejectors 14 are connected to a high-pressure and / or high-temperature air supply source and generate a secondary airflow F2 in the first pipe 12 which, by viscous friction, causes a flow of the main flow F1 in the pipe 12. The flows F1, F2 then flow into the second pipe 16 to the outside 20 of the turbomachine.

[0023] The technology of this type of ejector or jet horn is well known to those skilled in the art and therefore does not need to be detailed.

[0024] There figure 2 illustrates an example of the implantation of a device 10 in a turbomachine 22 here of a helicopter-type aircraft.

[0025] The turbomachine 22 conventionally comprises, from upstream to downstream, an air inlet 24, at least one compressor 26, a combustion chamber 28, at least one turbine 30 and an exhaust 31.

[0026] The air inlet 24 has an annular shape and comprises an upstream portion 24a of frustoconical shape which flares downstream, and a downstream portion 24b of frustoconical shape which, conversely, flares upstream. In other words, the air inlet 24 has a maximum diameter at the junction between these portions 24a, 24b.

[0027] The airflow F0 entering the air inlet 24 therefore flows first radially from the inside to the outside in the first portion 24a of the air inlet 24, then radially from the outside to the inside in the second portion 24b and to the compressor 26. During the flow of the airflow F0 in the first portion 24a, the particles potentially present in this airflow are carried by inertia into the enclosure 18 which is connected to the external periphery of the air inlet 24.

[0028] The device 10 extends along and to one side of the turbomachine 22. In the example shown, the first conduit 12 extends from the housing 18 and the air inlet 24 to the exhaust 31. The ejectors 14 are mounted in the first conduit 12 at the turbine 30 and are supplied with pressurized and / or temperature-controlled air drawn directly from the turbine 30 by suitable sampling means 32. The second conduit 16 extends downstream of the first conduit 12 and the turbine 30, for example, to an exhaust 31, for example, in the form of an exhaust gas outlet nozzle.

[0029] Device 10 of the figure 2 is therefore associated with an enclosure 18 and an air inlet 24a forming a particle trap at the inlet of the turbomachine 22.

[0030] There figure 3Figure 10 illustrates a device based on the prior art. It can be seen that the second conduit 16 is formed by a tubular wall with a constant cross-section over its entire axial length. Furthermore, the ejectors 14 are distributed around the axis A of the first conduit 12. This technology is unsatisfactory due to the turbulence and pressure losses that occur during operation at the ejector outlets, as mentioned above, making it highly sensitive to pressure losses upstream of the system, leading to a re-aspiration of the primary and secondary flows.

[0031] The present invention proposes a solution to this problem with a device 110, one embodiment of which is shown in the figures. figures 4 has 6 .

[0032] Device 110 includes: a first main airflow duct 112 F1, this first duct 112 having a main axis A, a plurality of secondary airflow ejectors 114 F2, which are located inside the first duct 112 and configured to eject the secondary airflow F2 and force the main airflow F1 into the first duct 112, and a second exhaust duct 116 located at the outlet of the ejectors 114 and connected to the first duct 112.

[0033] The first conduit 112 has a general tubular shape and can be straight or angled. It includes a longitudinal end 112a in which the ejectors 114 are located and which includes a free peripheral edge 112b.

[0034] The ejectors 114 are located in the first conduit 112, near this peripheral edge 112b, and each has a generally angled shape in the example shown. Each ejector 114 is tubular and comprises an end 114a connected to an orifice (not visible) through the conduit 112, and an opposite end 114b which is narrowed to form a nozzle and which is oriented in a direction parallel to the axis A and towards the peripheral edge 112b ( figure 6 ).

[0035] The ends 114a of the ejectors 114 are connected via the aforementioned orifices of the conduit 112 to an annular collector 136 which is mounted around the conduit 112 and which is connected to sampling means 132 ( figure 6 ) comparable to the aforementioned sampling methods 32.

[0036] The second pipe 116 has an end 116a which is connected to the end 112a of the first pipe 112 and which directly receives the secondary flow F2 to force the flow of the main air flow F1 from the first pipe 112 to the second pipe 116.

[0037] According to the invention, the end 116a of the second conduit 116 includes a restriction 134, i.e., a reduction in its cross-sectional area. The restriction 134 effectively channels the flow of the primary flow F1 and secondary flow F2, thus eliminating the risk of turbulence and recirculation in this area.

[0038] The reduction in passage through the 134 restriction is on the order of 10 and 90%, preferably between 30 and 70%, and more preferably on the order of 50%. In the example shown ( figure 6 ), the restriction 134 comprises three parts or sections, namely: an intermediate section 134b comprising a passage section Smin, an upstream section 134a situated between the intermediate section 134b and the ejectors 114, this upstream section 134a comprising at an upstream end 134aa a passage section Smax substantially identical to the passage section of the first conduit 112, and at a downstream end 134ab a passage section Smin which is less than Smax, and a downstream section 134c situated between the intermediate section 134b and the remainder of the second conduit 116, this downstream section 134c comprising at an upstream end 134ca a passage section Smin, and at a downstream end 134cb a passage section Smax substantially identical to the passage section of the first conduit 112.

[0039] The upstream section 134a has a length L1 or axial dimension less than a length L2 or axial dimension of the downstream section 134c. L2 = K.L1 with K between 1 and 10, and preferably between 3 and 5.

[0040] In the example shown, the end 116a of the second pipe 116 is engaged in the end 112a of the first pipe 112. The engagement length is greater than L1 here. The end 112a surrounds sections 134a, 134b and even part of section 134c.

[0041] The peripheral edge 112b of the first pipe 112 is located in a plane P1 which is perpendicular to the axis A and passes substantially through the downstream section 134c.

[0042] The end 116a of the second conduit 116 includes a peripheral edge 116b which extends in a plane P2 which is perpendicular to the axis A and passes substantially through the ends 114b or outlets of the ejectors 114 or upstream of these outlets ( figure 6 ).

[0043] The second conduit 116 is preferably made from a single piece, for example by additive manufacturing. The conduit 116 is, for example, made of metal. It has a generally straight shape in the example shown and a generally non-circular cross-section. This cross-section is flattened and, for example, oval or elliptical.

[0044] THE figures 7 and 8 illustrate a variant embodiment of device 110 according to the invention.

[0045] Device 210 figures 7 and 8 present many similarities to device 110 of the figures 4 to 6 .

[0046] The preceding description made in relation to device 110 therefore applies to device 210, insofar as it is not contrary to and does not contradict what follows.

[0047] The conduit 112 and the ejectors 116 associated with the device 210 are similar to those described above.

[0048] The second pipe 116 has a generally angled shape in the example shown and a passage section of generally non-circular shape. This shape is flattened and, for example, oval or elliptical.

[0049] The restriction 134 comprises three parts or sections, namely: an intermediate section 134b comprising a passage section Smin, an upstream section 134a situated between the intermediate section 134b and the ejectors 114, this upstream section 134a comprising at an upstream end 134aa a passage section Smax1 substantially identical to the passage section of the first conduit 112, and at a downstream end 134ab a passage section Smin which is less than Smax, and a downstream section 134c situated between the intermediate section 134b and the rest of the second conduit 116, this downstream section 134b comprising at an upstream end 134ba a passage section Smin, and at a downstream end 134bb a passage section Smax2 between Smin and Smax1. The end 116a of the second conduit 116, which is engaged in the end 112a of the first conduit 112, includes a peripheral edge 116b which extends in a plane P2 which is perpendicular to the axis A and passes upstream of the ends 114b or outlets of the ejectors 114 ( figure 8 ).

[0050] This peripheral edge 116b or the upstream section 134a includes notches 138, here in the shape of C or U, which are distributed around the axis A. The number of notches 138 is equal to the number of ejectors 114 and are positioned around the axis A according to the position of the ejectors 114 around the axis A so that the bases of the ejectors 114, i.e. their ends 114a, are at least partly embedded or engaged in these notches 138.

[0051] The invention thus proposes a device 110, 210 for driving a main airflow for an aircraft turbomachine, in which the exhaust duct 116 includes a restriction 134 at the outlets of the ejectors of a secondary airflow.

Claims

1. A device (110, 210) for guiding a main air flow (F1) for an aircraft turbine engine (22), this device comprising: - a first pipe (112) for the flow of a main air flow (F1), this first pipe having a main axis (A), - a plurality of ejectors (114) of a secondary air flow (F2) located inside the first pipe (112) and configured to eject a secondary air flow (F2) and force the flow of the main air flow (F1) in this first pipe (112), said ejectors (114) being distributed around said main axis (A) on a tubular wall of one end (112a) of the first pipe (112), and - a second exhaust pipe (116) located at the outlet of the ejectors (114) and comprising an end (116a) which is connected to the end (112a) of the first pipe (112) and which directly receives said secondary flow (F2) to force the flow of the main air flow (F1) from the first pipe (112) to the second pipe (116), characterised in that the end of the second pipe (116) is engaged in the end (112a) of the first pipe (112) and comprises a constriction (134) which is at least partly located in this end (112a) of the first pipe (112).

2. The device (110, 210) according to claim 1, wherein said constriction (134) represents a reduction in the passage cross-section of between 10 and 90%, preferably between 30 and 70%, and more preferably of the order of 50%.

3. The device (110, 210) according to claim 1 or 2, wherein said constriction (134) comprises: - an intermediate section (134b) comprising a passage cross-section Smin, - an upstream section (134a) located between the intermediate section and the ejectors (114), this upstream section (134a) comprising at an upstream end (134aa) a passage cross-section Smax or Smax1 substantially identical to the passage cross-section of the first pipe, and at a downstream end (134ab) a passage cross-section Smin which is smaller than Smax, and - a downstream section (134c) located between the intermediate section (134b) and the rest of the second pipe, this downstream section (134c) comprising, at an upstream end (134ca), a passage cross-section Smin and, at a downstream end (134cb), a passage cross-section Smax substantially identical to the passage cross-section of the first pipe (112) or a passage cross-section Smax2 between Smin and Smax1, and wherein the upstream section (134a) has a length L1 or axial dimension less than or equal to a length L2 or axial dimension of the downstream section (134c).

4. The device (110, 210) according to the preceding claim, wherein L2 = K.L1 with K between 1 and 10, and preferably between 3 and 5.

5. The device (110, 210) according to claim 3 or 4, wherein the intermediate section (134b) is located in the end (112a) of the first pipe (112).

6. The device (110, 210) according to one of the preceding claims, wherein the end (116a) of the second pipe (116) comprises a peripheral edge (116b) which is flush with the tubular wall of the end (112a) of the first pipe (112).

7. The device (110, 210) according to one of the preceding claims, wherein the end (116a) of the second pipe (116) comprises a peripheral edge (116b) which extends in a plane perpendicular to said main axis (A), said plane passing through outlets of the ejectors (114) or upstream of these outlets.

8. The device (210) according to the preceding claim, wherein said plane passes upstream of these outlets and said peripheral edge (116b) comprises notches (138) configured to each receive a base of one of said ejectors (114).

9. The device (110, 210) according to one of the preceding claims, wherein said second pipe (116) has a generally straight or bent shape.

10. The device (110, 210) according to one of the preceding claims, wherein said second pipe (116) has a generally non-circular passage cross-section.

11. The device (110, 210) according to one of the preceding claims, wherein said second pipe (116) is integrally formed, preferably of metal.

12. A turbine engine (22), in particular for an aircraft, comprising a device (110, 210) according to one of the preceding claims.

13. The turbine engine (22) according to claim 12, wherein it comprises, from upstream to downstream, in the orientation of the gas flow in the turbine engine, an air inlet (24), at least one compressor (26), a combustion chamber (28), at least one turbine (30) and an exhaust (31), said air inlet (24) being equipped with a particulate trap which is connected to said device (110, 210).