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Acoustically treated turbomachine multi-duct exhaust device

Imported: 24 Feb '17 | Published: 06 Jan '04

Benoit Denis Rene Gadefait, Hubert Hippolyte Vignau, Marie-Laure Olga Simone Ortiz

USPTO - Utility Patents

Abstract

A multi-duct diffusion exhaust device for a turbomachine. The exhaust device including an annular inlet, an outer casing shaped symmetrically overall with respect to an axis, one or more internal partitions defining several roughly concentric ducts for an exhaust stream to flow through, and an absorbent coating capable of absorbing some of the acoustic energy generated by the flow. The absorbent coating being provided on at least one of a surface of one internal partition and an interior surface of the outer casing. The absorbent coating having a thickness that is tailored along a length of the exhaust device to optimize the flow in the ducts by maintaining progressive diffusion and avoiding detachment near stationary surfaces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from studying a few particular embodiments which are taken by way of entirely non-limiting examples and which are illustrated by the appended drawings, in which:

FIG. 1 is a diagrammatic view in section along the flow axis, of one embodiment of a turbomachine exhaust device according to the invention;

FIG. 2 is a view in section with cutaway showing, on a larger scale, a first alternative form of absorbent coating installed in the embodiment illustrated in FIG. 1;

FIG. 3 is a view in section with cutaway similar to FIG. 2, of an alternative form of absorbent coating;

FIG. 4 is a view similar to FIGS. 2 and 3, showing another alternative form of absorbent coating;

FIG. 5 is a view in section on V—V of FIG. 4;

FIG. 6 is a view in partial section with cutaway of a modification to the alternative form illustrated in FIG. 4;

FIG. 7 is a diagrammatic sectional view similar to FIG. 1 of another embodiment of the invention; and

FIG. 8 is a diagram illustrating the aerodynamic performance of an exhaust device.

Claims

1. A multi-duct diffusion exhaust device for an exhaust gas stream at an outlet of a turbomachine, comprising an annular inlet, an outer casing shaped symmetrically overall with respect to an axis, and at least one internal partition defining roughly concentric passages for the exhaust gas stream to flow through,

2. A turbomachine exhaust device according to claim 1, wherein the absorbent coating of said at least one internal partition and the absorbent coating of said interior surface exhibit absorption characteristics which differ according to a nature of the flow past a surface thereof.

3. A turbomachine exhaust device according to claim 1, wherein the passages have an area that varies along a length of the axis so as simultaneously to optimize a flow speed and the thickness of the absorbent coating of said at least one internal partition and the thickness of the absorbent coating of said interior surface.

4. A turbomachine exhaust device according to claim 1, wherein the absorbent coating of at least one of said at least one internal partition and said interior surface is arranged on a surface thereof facing the flow.

5. A turbomachine exhaust device according to claim 1, wherein the absorbent coating of said at least one internal partition and the absorbent coating of said interior surface comprise at least one of a porous acoustic material and a resonator acoustic material.

6. A turbomachine exhaust device according to claim 5, wherein the acoustic material is a fibrous material selected from the group of glasswool, rockwool, and ceramic fibres.

7. A turbomachine exhaust device according to claim 5, wherein the acoustic material comprises a number of hollow microspheres arranged in one or more layers or loosely.

8. A turbomachine exhaust device according to one of claim 6 or 7, wherein the absorbent coating of said at least one internal partition and the absorbent coating of said interior surface comprise an acoustically transparent wall capable of retaining the acoustic material.

9. A turbomachine exhaust device according to claim 5, wherein the absorbent coating of said at least one internal partition and the absorbent coating of said interior surface comprise the resonator acoustic material with an open-cell structure associated with an acoustically resistive porous wall and closed on the other side by a rigid base wall.

10. A turbomachine exhaust device according to claim 9, wherein the resonator acoustic material comprises several superimposed layers of resonators having at least one of different thicknesses and equal thicknesses, a porous wall being inserted between two adjacent layers.

11. A turbomachine exhaust device according to claim 1, further comprising a central body along the axis of the device over most of its length, the central body having a surface with an absorbent coating.

12. A turbomachine exhaust device according to claim 1, wherein the exhaust gas stream is let out through a deflecting part which deflects the stream with respect to an inlet axis, said deflecting part having an internal surface coated by an absorbent coating.

13. A turbomachine exhaust device according to claim 9, wherein the open-cell structure has cells with axes substantially perpendicular to the porous wall.

14. A multi-duct diffusion exhaust device for a turbomachine, the exhaust device comprising:

15. A turbomachine exhaust device according to claim 14, wherein at least one of the at least two ducts has a cross-sectional area that varies along the length of the exhaust device so as to simultaneously optimize a flow speed of the exhaust stream and the thickness of the absorbent coating.

16. A turbomachine exhaust device according to claim 14, wherein the absorbent coating comprises at least one of a porous acoustic material and a resonator acoustic material.

17. A turbomachine exhaust device according to claim 14, wherein the absorbent coating comprises an acoustic material and an acoustically transparent wall configured to retain the acoustic material.

18. A turbomachine exhaust device according to claim 17, wherein the acoustic material comprises at least two superimposed layers of acoustically absorbing material and a porous wall positioned between adjacent layers of the at least two superimposed layers.

19. A turbomachine exhaust device according to claim 14, wherein the absorbent coating comprises:

20. A turbomachine exhaust device according to claim 1, wherein an overall passage area of said ducts continuously increase from the annular inlet to an outlet of the exhaust device.

21. A turbomachine exhaust device according to claim 1, wherein the one or more internal partitions has a geometrical shape that is tailored to the thickness of the absorbent coating so that the passage area of the ducts allows greater recuperation of the energy while keeping pressure low at intake.

22. A turbomachine exhaust device according to claim 14, wherein an overall passage area of said ducts continuously increase from the inlet to the outlet.

23. A turbomachine exhaust device according to claim 14, wherein the at least one partition has a geometrical shape that is tailored to the thickness of the absorbent coating so that a passage area of the ducts allows greater recuperation of energy generated by the flow while keeping pressure low at intake.