ACOUSTICALLY OPTIMIZED DISCHARGE LINE GRID WITH CHANNELS

Abstract

Discharge grate intended to be mounted inside or at the outlet of a conduit of a discharge valve of a turbine engine of an aircraft, the discharge grate comprising an upstream face intended to receive a gas flow, a downstream face parallel to the upstream face and intended to deliver the gas flow received on the upstream face, and orifices passing through the perforated plate from the upstream face to the downstream face and intended to convey the gas flow through the perforated plate.

The discharge grate comprises for each orifice of the perforated plate a tubular channel, coaxial with the orifice with which it is associated, and projecting from the downstream face of the perforated plate.

Claims

1. A discharge grate intended to be mounted inside or at the outlet of a conduit of a discharge valve of a turbine engine of an aircraft, the discharge grate including a perforated plate comprising an upstream face intended to receive a gas flow, a downstream face intended to deliver the gas flow received on the upstream face, and orifices passing through the perforated plate from the upstream face to the downstream face and intended to convey the gas flow through the perforated plate, wherein the discharge grate comprises for each orifice of the perforated plate a tubular channel, coaxial with the orifice with which it is associated, and projecting from the downstream face of the perforated plate.

2. The discharge grate according to claim 1, wherein the channels form a honeycomb structure.

3. The discharge grate according to claim 1, wherein the channels comprise a passage section defined in a plane parallel to the downstream face of the perforated plate, the passage section of the channels having a greatest length in the plane of the section comprised between one and five times a characteristic diameter of the orifices.

4. The discharge grate according to claim 3, wherein the passage section of the channels has a greatest length in the plane of the section equal to twice the characteristic diameter of the orifices.

5. The discharge grate according to claim 1, wherein the channels extend between a first open end communicating with an orifice and a second open end over a length comprised between one time and one hundred times the characteristic diameter of the orifices.

6. The discharge grate according to claim 5, wherein the channels are all cylindrical, straight and all have the same length.

7. The discharge grate according to claim 5, wherein the channels are non-rectilinear channels to guide the flow in a direction distinct from the direction orthogonal to the plane in which the perforated plate extends.

8. A discharge valve for an aircraft turbojet engine comprising a conduit intended to convey a gas flow and at least one discharge grate according to claim 1 mounted inside the conduit or on an outlet of the conduit.

9. The discharge valve according to claim 8, wherein the discharge grate is mounted inside the conduit.

10. The discharge valve according to claim 8, wherein the discharge grate is mounted at the outlet of the conduit.

11. A turbojet engine comprising a nacelle, a coaxial intermediate casing and internal casing, and a discharge valve according to claim 8, the intermediate casing and the internal casing delimiting therebetween a primary flow path for a fluid flow, the nacelle and the intermediate casing delimiting therebetween a secondary flow path for a fluid flow, and the discharge valve being mounted between the primary flow path and the secondary flow path and configured to withdraw a portion of the air in the primary flow path and deliver it into the secondary flow path.

12. The turbojet engine comprising a nacelle, a coaxial intermediate casing and internal casing, and a discharge valve according to claim 8, the intermediate casing and the internal casing delimiting therebetween a primary flow path for a fluid flow in which a combustion chamber is mounted, the nacelle and the intermediate casing delimiting therebetween a secondary flow path for a fluid flow, and the discharge valve being configured to withdraw a portion of the air in the primary flow path upstream of the combustion chamber and deliver it into the primary flow path downstream of the combustion chamber.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1, already described, shows a sectional view in a longitudinal plane of a turbojet engine according to the prior art with a discharge valve with reinjection into the primary flow.

[0036] FIG. 2, already described, shows a sectional view in a longitudinal plane of a turbojet engine according to the prior art with a discharge valve with reinjection into the primary flow.

[0037] FIG. 3A schematically illustrates a sectional view of a discharge valve according to a first embodiment of the invention respectively with the grate disposed inside the conduit.

[0038] FIG. 3B schematically illustrates a sectional view of a discharge valve according to a first embodiment of the invention respectively with the grate mounted at the outlet of the conduit.

[0039] FIG. 4 schematically shows a sectional view of a grate of a discharge valve according to a second embodiment respectively with the grate disposed inside the conduit.

[0040] FIG. 5 schematically shows a sectional view of a portion of a grate of a discharge valve according to a third embodiment respectively with the grate disposed inside the conduit.

[0041] FIG. 6 schematically shows a sectional view of a portion of a grate of a discharge valve according to a fourth embodiment respectively with the grate disposed inside the conduit.

DESCRIPTION OF EMBODIMENTS

[0042] FIGS. 3A and 3B schematically illustrate two sectional views of a discharge valve according to a first embodiment of the invention respectively with the grate disposed inside the conduit and at the outlet of the conduit of the discharge valve.

[0043] The discharge valve 20 for an aircraft turbojet engine comprises a conduit 21 intended to convey a gas flow F and a grate 22. The grate 22 includes a plate 23 perforated with a multitude of orifices 230 and channels 26.

[0044] The perforated plate 23, through which the gas flow F passes, comprises a first face 24, or upstream face, facing the gas flow F, that is to say receiving the flow F, and a second face 25, or downstream face, through which the flow F escapes after having passed through the perforated plate 23 via the orifices 230. The second face 25 is opposite the first face 24 and parallel thereto. The orifices 230 thus pass through the plate 23 from the upstream face 24 to the downstream face 25.

[0045] The grate 22 comprises a channel 26 for each orifice 230 of the plate 23. Each channel 26 extends from the downstream face 25 of the plate 23 is coaxial with the associated orifice with which it is associated.

[0046] In the first embodiment illustrated in FIGS. 3A and 3B, each channel 26 forms a hollow cylinder with any base, and preferably with a circular or hexagonal base, the generatrices of which extend in a direction orthogonal to the plane in which extends the perforated plate 23. In other words, the channels 26 form rectilinear hollow cylinders of identical length L. And in case the cylinders are hexagonal based, together they form a honeycomb structure.

[0047] The channels 26 thus allow the development of the jets coming from the orifices 230 while delaying the interaction between the various jets as much as possible.

[0048] The grate 22 has an outer perimeter whose shape corresponds to the shape of the inner perimeter of the conduit 21. In FIG. 3A, the grate 22 is inserted inside the conduit 21 to partially block the conduit 21 on a section located between the inlet and the outlet of the conduit 21, while in FIG. 3B, the grate 22 is inserted at one end of the conduit 21 inside the conduit 21 to partially block the outlet of the conduit 21. In both cases, the conduit 21 is only partially blocked in that the flow F can flow through the channels of the grates 22, and only through these channels 23.

[0049] The plane in which the sectional views of FIGS. 3A and 3B are produced is a plane comprising the direction along which the conduit 21 extends, in other words an axial direction D.sub.A of the cylinder formed by the conduit 21 within the context of the example illustrated in FIGS. 3A and 3B, and a direction orthogonal to the axial direction D.sub.A and parallel to the plane in which the perforated plate 22 extends, that is to say a radial direction D.sub.R.

[0050] FIG. 4 schematically illustrates a schematic sectional view of a discharge valve according to a second embodiment of the invention respectively with the grate disposed inside the conduit and at the outlet of the conduit of the discharge valve.

[0051] The second embodiment differs from the first embodiment illustrated in FIGS. 3A and 3B in that the channels 26 are not rectilinear hollow cylinders but non-rectilinear tubes forming an angle of 90° to deflect the jets in a direction different from the direction of incidence of the gas flow F on the grate 22. The length L of the channel 26 corresponds in this embodiment to the length of the tube over its entire path.

[0052] In the two embodiments shown in FIGS. 3A, 3B and 4, the orifices 230 are circular orifices having a diameter D, and the channels have a length L comprised between one time the diameter D and one hundred times the diameter D, that is to say D<L<100D, while the base of the cylinders or the section of the tubes has a diameter Dc comprised between one time the diameter D and five times the diameter D, that is to say D<Dc<5Dc.

[0053] In the case where the orifices of the perforated plate are not circular but nevertheless of uniform shape and distribution on the perforated plate as shown in FIG. 5, the characteristic diameter corresponds to the diameter D.sub.0 of a circular section equivalent to the surface of an orifice.

[0054] In the case where the orifices of the perforated plate are neither circular nor of equivalent shape, but nevertheless of uniform distribution as illustrated in FIG. 6, the characteristic diameter corresponds to the average of the diameters D.sub.1 to D.sub.6 of the sections equivalent to the surface of each orifice.

[0055] A channel section that is too small, that is to say less than the characteristic diameter, would imply low dissipation of the isolated jet coming from each orifice of the perforated plate. On the contrary, a channel with a section that is too large, that is to say greater than five times the characteristic diameter, would not optimize the overall dimensions in the engine integration.

[0056] The discharge valves according to the first and second embodiments are intended to be mounted on turbojet engines such as those shown in FIGS. 1 and 2.

[0057] The invention thus allows to have a discharge valve equipped with an improved grate allowing to minimize the intensity of the aero-acoustic phenomena generated by the relief systems equipped with a perforated grate.