JPH1026013A - Sound absorbing duct - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of exhaust noise of a high temperature gas flow. SOLUTION: A plurality of heat resisting sound absorbing materials 6 are layered in parallel to a perforated plate-form part 3 at the interior of a holder 1, formed of a ceramics composite material, provided with an extension parts 4 and 5 protruded in the same direction approximately at right angles with the plate-form part 3 from the two ends of the porous plate-form part 3 in which a number of holes 2 are formed. A number of sound absorbing material aggregate 10 having the heat resisting sound absorbing materials 6 being pressed toward the porous plate-form part 3 by a press means 9 are provided. The sound absorbing material aggregate 10 is mounted on the whole surface of the inner side part of the duct body 12 such that the plate-form parts 3 are pointed to the interior of the duct body 12. This constitution reduces the generation of exhaust gas noise of a high temperature gas flow flowing through the duct body 12 by using the heat resisting sound absorbing material 6 having size available.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sound absorbing duct.

[0002]

2. Description of the Related Art In recent years, as a propulsion device for a supersonic aircraft,
Research and development of an air turbo ramjet engine is underway.

[0003] In an air turbo ram jet engine, in a low speed range (during takeoff and landing), a turbine is rotated by a high-temperature and high-pressure combustible gas flow supplied from a gas generator of a one-liquid system, a two-liquid system, a solid system or the like. The compressor drives the compressor, and the compressor sucks and compresses the air in front of the engine to burn a mixed gas of the air flow obtained by rotating the turbine and the combustible gas flow. To generate thrust.

In a high-speed region (during cruising flight), air flowing into the engine is compressed by the compressor due to ram pressure (pressure of air flowing into the engine from the front) during high-speed flight.

In putting such an air turbo ramjet engine suitable for supersonic flight to practical use, it is an important research topic to reduce the exhaust noise of the combustion gas flow.

[0006]

However, exhaust noise suppressing means for a high-temperature gas flow having a temperature of about 800 ° C. to 900 ° C., such as a combustion gas flow ejected from an air turbo ramjet engine, has not yet been developed. Not technically established.

On the other hand, the heat-resistant sound-absorbing material constituting the exhaust noise suppressing means for a high-temperature gas flow includes a heat-resistant metal cloth formed of stainless steel-based metal fibers in a cloth shape or a stainless steel-based metal porous body. It is considered that a heat-resistant porous plate formed in a shape should be applied. However, the dimensions of a heat-resistant metal cloth and a heat-resistant porous plate which are currently available have a thickness of 30 m.
m, since the planar shape is limited to about 300 mm × 400 mm, simply applying these heat-resistant sound-absorbing materials to the exhaust noise reduction means of an air turbo ramjet engine would result in:
Exhaust noise cannot be effectively suppressed due to a shortage of member dimensions.

The present invention has been made in view of the above circumstances, and has as its object to provide a sound-absorbing duct capable of effectively suppressing exhaust noise of a high-temperature gas flow.

[0009]

In order to achieve the above object, in the sound-absorbing duct according to the first aspect of the present invention, a multi-hole perforated plate is provided at both ends of the perforated plate. A plurality of heat-resistant sound-absorbing materials are laminated inside a holder made of a ceramic-based composite material provided with an overhang protruding substantially perpendicularly and in the same direction so as to be positioned parallel to the perforated plate-like portion,
The heat-resistant sound-absorbing material has a large number of sound-absorbing material aggregates pressed toward the perforated plate-like portion by pressing means provided on the overhang portion,
A sound-absorbing material assembly is attached to the entire inner surface of the duct body such that the perforated plate-shaped portion faces inward of the duct body.

In the sound absorbing duct according to the second aspect of the present invention, in addition to the above-described structure of the sound absorbing duct according to the first aspect of the present invention, the duct main body is located downstream of the high-temperature gas flow generating source in the gas flow direction. The high temperature gas flow source is disposed at a distance from the high temperature gas flow source, the front end of a cylindrical mixer is connected to the downstream end of the high temperature gas flow source in the gas flow direction, and the rear end of the mixer is connected to the duct body. The outside air inlet is inserted between the outside of the mixer and the sound absorbing material assembly inside the front end.

In any one of the sound absorbing ducts according to the first and second aspects of the present invention, a plurality of heat-resistant sound absorbing materials laminated inside the holder are pressed by the pressing means to obtain a sound absorbing material assembly. A body is formed, and exhaust noise of a high-temperature gas flow flowing through a duct body in which the sound absorbing material assembly is attached to the entire inner surface is reduced.

In the sound-absorbing duct according to a second aspect of the present invention, the mixer inside the front end of the duct body is formed by an ejector effect of the high-temperature gas flow flowing from the high-temperature gas flow source through the mixer into the inside of the duct body. External air is drawn into the inside of the duct main body from the gap between the outside of the duct and the sound absorbing material assembly to reduce the flow velocity of the high-temperature gas flow, thereby reducing exhaust noise of the high-temperature gas flow flowing through the duct main body.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 1, 2 and 5 to 10 show an embodiment of a sound absorbing duct according to the present invention. The sound absorbing duct comprises a holder 1, a plurality of heat-resistant sound absorbing materials 6, a pressing means. 9, a plurality of sound absorbing material assemblies 10, a duct main body 12, and a mixer 13.

The holder 1 is provided with a rectangular perforated plate portion 3 having a large number of holes 2 formed therein, and projecting portions 4 and 5 projecting from both ends of the perforated plate portion 3 at right angles in the same direction. These perforated plate portions 3 and overhang portions 4 and 5 are fiber reinforced using carbon fiber or silicon carbide as a reinforcing material and ceramics such as silicon carbide as a matrix by a chemical vapor deposition method. It is formed of a ceramic-based composite material (CMC / ceramics matrix composites) such as ceramics.

Inside the holder 1 is a heat-resistant metal cloth formed of stainless steel-based metal fibers in a cloth shape, or a plate-shaped heat-resistant porous plate formed of a stainless steel-based metal porous body in a plate shape. A plurality of heat-resistant sound-absorbing materials 6 are laminated so as to be positioned in parallel with the perforated plate-shaped portion 3.

The distal ends of the overhang portions 4 and 5 are bent in a flange shape, and pressing means 9 formed by sandwiching a wave-like spring material 7 between two straps 8 and 8 has an appropriate number of overhang portions 4 and 5. 5 and the pressing means 9 is used to hold the holder 1.
The heat-resistant sound-absorbing material 6 laminated in the inside is pressed by the perforated plate-shaped portion 3.

The pressing means 9 may have a structure as shown in FIGS.

The pressing means 9 in FIG. 3 and FIG. 4 is a spring member 7 which is bent in a pleated shape and arranged along a flange-shaped bent portion at the tip of the overhanging portion 4, 5 of the holder 1.
And a metal band 8 interposed between the spring material 7 and the heat-resistant sound-absorbing material 6
It is composed of

The duct body 12 is disposed behind the hot gas flow source (air turbo ram jet engine) 11 so as to be coaxial with the hot gas flow source 11 at an interval.

The duct body 12 is formed by assembling into a rectangular tube shape by bolting a number of metal panels provided with connection flanges on four sides, and has a rectangular cross section as shown in FIGS. As shown in FIG. 5, the opening area of the hollow portion increases near the front end, and the opening area is constant from the portion near the front end to the rear end.

On the inner side of the duct body 12, the above-described sound absorbing material assembly 10 including the holder 1, the heat-resistant sound absorbing material 6, and the pressing means 9 is provided. The perforated plate-shaped portion 3 faces the inside of the duct body 12. In this way, they are mounted side by side on the entire top, bottom, left and right without gaps.

The mixer 13 is formed in a cylindrical shape, and has a front end connected to the downstream end of the high-temperature gas flow generation source 11 in the gas flow direction, and a rear end inserted into the front end of the duct body 12.

The cross-sectional shape of the mixer 13 is such that the front end corresponds to the rear end of the hot gas flow source 11 in FIG.
7, the intermediate portion corresponding to the front end of the duct body 12 has a square hollow structure as shown in FIG. 7, and further, the rear end has an upper side as shown in FIGS. 8 and 9. It has a fold-like bent portion 14 in the portion and the lower portion, and is formed in a cross section in which the opening area near the center decreases as approaching the rear end.

As shown in FIG. 5, an outside air inlet 15 is provided between the outer surface of the portion near the rear end of the mixer 13 and the inner surface of the front portion of the duct body 12.
Is open to the atmosphere.

Next, the operation of the sound absorbing duct shown in FIGS. 1 to 10 will be described.

The combustion gas flow 16 after rotating the turbine of the high-temperature gas flow generation source (air turbo ram jet engine) 11, the air flow 17 from the compressor, and the mixed gas flow 18 resulting from the combustion of the mixed gas are mixed into the mixer 13. After being stirred by the shape of the duct body 12, the exhaust noise when flowing through the inside of the duct body 12 is absorbed by the heat-resistant sound-absorbing material 6 of the sound-absorbing material assembly 10 which is attached to the entire inner surface of the duct body 12 without gaps. As a result, exhaust noise is reduced.

As described above, the mixed gas stream 18 is supplied to the mixer 1
When the air flows into the inside of the duct body 12 from the outside 3, the air outside the mixer 13 flows into the inside of the duct body 12 from the outside air inlet 15 as a suction airflow 19 due to an ejector effect.

Then, the suction air flow 19 flowing into the inside of the duct main body 12 reduces the flow velocity of the mixed gas flow 18,
Exhaust noise is more effectively reduced, and an increase in the internal temperature of the duct body 12 is suppressed.

The sound-absorbing duct of the present invention is not limited to the above-described embodiment, and the present invention is applied to a means for reducing exhaust noise of a high-temperature gas flow source other than an air turbo ramjet engine. It goes without saying that various changes can be made without departing from the spirit of the present invention.

[0031]

As described above, according to the sound absorbing duct of the present invention, the following various excellent effects can be obtained.

(1) In any of the sound-absorbing ducts according to the first and second aspects of the present invention, a plurality of heat-resistant sound-absorbing materials laminated inside the holder are pressed by pressing means to form a sound-absorbing material assembly. However, since the sound absorbing material assembly is attached to the entire inner surface of the duct main body, it is possible to reduce exhaust noise of a high-temperature gas flow flowing through the duct main body by using a heat-resistant sound absorbing material of an available size.

(2) In the sound-absorbing duct according to the second aspect of the present invention, the ejector effect of the high-temperature gas flowing from the high-temperature gas flow source through the mixer into the inside of the duct main body causes the inside of the front end of the duct main body. Since the outside air is drawn into the inside of the duct main body from the gap between the outside portion of the mixer and the sound absorbing material assembly, the flow velocity of the high-temperature gas flow flowing inside the duct main body is reduced, and the high-temperature gas flow flowing through the duct main body is reduced. Exhaust noise can be more effectively reduced.

[Brief description of the drawings]

FIG. 1 is a partial perspective view showing an example of an embodiment of a sound absorbing duct of the present invention.

FIG. 2 is a partial cross-sectional view showing one example of an embodiment of a sound absorbing duct of the present invention.

FIG. 3 is a partial perspective view showing another example of the embodiment of the sound absorbing duct of the present invention.

FIG. 4 is a partial sectional view showing another example of the embodiment of the sound absorbing duct of the present invention.

FIG. 5 is an overall view showing an example of an embodiment of a sound absorbing duct of the present invention.

FIG. 6 is a sectional view taken along line VI-VI of FIG. 5;

FIG. 7 is a sectional view taken along line VII-VII of FIG. 5;

8 is a sectional view taken along line VIII-VIII of FIG.

FIG. 9 is a sectional view taken along line IX-IX of FIG. 5;

FIG. 10 is a sectional view taken along line XX of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Holder 2 Hole 3 Perforated plate part 4 Projection part 5 Projection part 6 Heat-resistant sound-absorbing material 9 Pressing means 10 Sound-absorbing material assembly 11 High-temperature gas flow source 12 Duct body 13 Mixer 15 Outside air intake

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location G10K 11/16 B

Claims (2)

[Claims] 1. A holder made of a ceramic composite material provided with projecting portions that are provided at both ends of a perforated plate-like portion having a large number of holes formed thereon and project at substantially right angles to the perforated plate-like portion in the same direction. Inside, a plurality of heat-absorbing sound-absorbing materials are laminated so as to be positioned parallel to the perforated plate-like portion, and a sound-absorbing material assembly in which these heat-resistant sound-absorbing materials are pressed toward the perforated plate-like portion by pressing means provided on the overhang portion. And a sound absorbing material assembly is mounted on the entire surface of the inside of the duct body such that the perforated plate-shaped portion faces inward of the duct body. 2. A duct body is disposed downstream of the hot gas flow generation source in the gas flow direction at a distance from the hot gas flow generation source, and a cylinder is provided at a downstream end of the hot gas flow generation source in the gas flow direction. 2. The mixer according to claim 1, wherein a front end of the mixer is connected, and a rear end of the mixer is inserted into a front end of the duct body so that an outside air intake is formed between an outer portion of the mixer and the sound absorbing material assembly. Sound absorbing duct.