JP2022129373A - Supersonic aircraft and sonic boom and jet noise reduction method - Google Patents

Abstract

To achieve both a reduction in sonic boom and jet noise when a supersonic aircraft takes off and lands at an airport which are the main issues with environmental compatibility of the supersonic aircraft.SOLUTION: A supersonic aircraft comprises: a shielding body which reduces sonic boom, due to an engine exhaust stream discharged from a jet engine stored in an engine nacelle attached to a fuselage of an airframe, through shielding the engine exhaust stream; and an exhaust nozzle which is installed at an exhaust port of the engine nacelle, reduces a high-frequency content of jet noise through generating a sound source of the high-frequency content at a position where the shield body can shield the high-frequency content of the engine exhaust stream, and reduces a low-frequency content of the jet noise through enhancing mixing of the low-frequency content of the engine exhaust stream with an external air flow.SELECTED DRAWING: Figure 9

Description

The present invention relates to supersonic aircraft, such as supersonic airliners, and methods for reducing sonic booms and jet noise in such supersonic aircraft.

When a supersonic aircraft flies over the sky at supersonic speed, the shock waves generated from each part of the aircraft unite as they propagate over a long distance in the atmosphere, and on the ground, they are observed as an N-type pressure waveform that causes two sudden pressure fluctuations. , is heard by humans as a momentary explosion. This is what is commonly called a "sonic boom". The Concorde, which was retired in 2003 AD, was unable to fly at supersonic speeds on the ground due to its sonic boom, and was limited only to sea flights. there is

In addition to sonic booms, jet noise during airport takeoff and landing is also a major challenge in the environmental compatibility of supersonic aircraft. The International Civil Aviation Organization (ICAO) is currently discussing the establishment of standards for both, and low take-off and landing noise and a low sonic boom are essential for newly entering the commercial supersonic aircraft market. It is an element. Jet noise generated by engine exhaust is the main factor of supersonic aircraft jet noise during takeoff and landing at airports. It is known that suppression or shielding of the sound source is effective for this countermeasure.

As a technique for suppressing jet noise during take-off and landing at an airport, low-noise nozzles with improved exhaust nozzle outlet shapes have been proposed in Patent Document 1 and Non-Patent Document 2. Also, as a technique for shielding engine fan noise, there is known a technique for using the airframe as a shield by devising the arrangement of the engine, as in Patent Document 2. On the other hand, jet noise is found downstream from the engine exhaust port, so it is known that the shielding effect of the fuselage and tail can hardly be obtained. As a technique to improve the shielding performance of this jet noise, as in Non-Patent Document 1, a method of shielding the noise by changing the sound source distribution by changing the shape of the nozzle outlet and providing an airframe rear end plate (aft deck) is being researched. . As a method for reducing the sonic boom, a method using shielding fins arranged at the rear end of the fuselage has been proposed as in Patent Document 3 and Non-Patent Document 3.

Japanese Patent No. 6183837 JP 2012-106726 A JP 2019-182125 A

James Bridges, "Noise Measurements of a Low-Noise Top-Mounted Propulsion Installation for a supersonic airliner", [online], AIAA paper 2019-0253, AIAA SciTech 2019 Conference 7-11 January 2019, [Retrieved on January 26, 2021 ], Internet <https://arc.aiaa.org/doi/10.2514/6.2019-0253> Junichi Akatsuka and Tatsuya Ishii, "Experimental and Numerical Study of Jet Noise Reduction for Supersonic Aircraft Using Variable Folding Nozzle Concept", [online], AIAA paper 2018-3612, AIAA AVIATION Forum 25-29 June 2018, [January 26, 2021 day search], Internet <https://arc.aiaa.org/doi/abs/10.2514/6.2018-3612> Japan Aerospace Exploration Agency, "Supplementary material: Ex-post evaluation of research and development of quiet supersonic aircraft integrated design technology", [online], July 28, 2020, Ministry of Education, Culture, Sports, Science and Technology, Aeronautical Science and Technology Commission (66th meeting) Handout [searched January 26, 2021], Internet <https://www.mext.go.jp/b_menu/shingi/gijyutu/gijyutu2/004/shiryo/1422978_00003.htm>

The low-noise nozzles of Patent Literature 1 and Non-Patent Literature 2 are effective in reducing the low-frequency component of jet noise that has a sound source at a position away from the engine and propagates in the downstream direction. There are cases where the effect is weak for high-frequency components that have a sound source in and propagate to the side, or on the contrary, they increase noise. The noise shielding design by the fuselage of Patent Document 2 is effective for fan noise that has a sound source near the engine, but it is not effective for jet noise that disperses and generates sound sources at positions away from the engine. For this reason, a method of shielding the jet noise by the method of Non-Patent Document 1 has been studied, but there is a trade-off with a low sonic boom. On the other hand, the shielding fins of Patent Literature 3 and Non-Patent Literature 3 that reduce the sonic boom do not have the effect of shielding the jet noise. For this reason, technology to reduce jet noise during airport takeoff and landing and technology to lower the sonic boom during cruising are separately required.

In view of the circumstances as described above, it is an object of the present invention to solve both the reduction of sonic boom and the reduction of jet noise during takeoff and landing at airports, which are major issues in the environmental compatibility of supersonic aircraft.

A supersonic aircraft according to one aspect of the present invention includes:
a shield that reduces a sonic boom caused by an engine exhaust flow ejected from a jet engine housed in an engine nacelle attached to the fuselage of an aircraft by shielding the engine exhaust flow;
Reduce jet noise of high-frequency components by generating a sound source of high-frequency components at a position that is provided at the exhaust port of the engine nacelle and that allows the shield to block high-frequency components of the engine exhaust flow. and an exhaust nozzle for reducing jet noise of low frequency components by promoting mixing of the low frequency components of the engine exhaust flow with the outside air flow;
Equipped with

According to the present embodiment, by using both the shield that reduces the sonic boom and the exhaust nozzle that reduces the jet noise of the low frequency component, the high frequency component can be shielded at a position where the high frequency component can be shielded. Jet noise of high frequency components can be reduced by generating a sound source. It can solve both sonic boom reduction and airport noise reduction, which are major issues in the environmental compatibility of supersonic aircraft.

The exhaust nozzle is positioned to allow the shield to shield high frequency components of the engine exhaust flow by promoting mixing of the engine exhaust flow and ambient air flow near the exhaust port. sound source.

The exhaust nozzle promotes early (ie, upstream) mixing of the engine exhaust flow and the ambient air flow by turbulence in the airflow near the exhaust port. For this reason, in the upstream, relatively small-scale disturbances, which are sound sources of high-frequency components, are strengthened, and as a result, the position of the high-frequency sound sources can be generated on the upstream side.

In the polar angle range where the nose of the airframe is 0°, the exhaust port of the exhaust nozzle is 90°, and the aft of the airframe is 180°,
In the polar angle range of 110° or more and 140° or less, the amount of jet noise reduction when using the exhaust nozzle and the shield is the reduction in jet noise when the exhaust nozzle is used and the shield is not used. It can be larger than the quantity.

According to this embodiment, it is possible to obtain a high airport noise reduction effect that cannot be obtained by a combination of a shield and an exhaust nozzle different from the exhaust nozzle according to this embodiment.

In the polar angle range where the nose of the airframe is 0°, the exhaust port of the exhaust nozzle is 90°, and the aft of the airframe is 180°,
At a polar angle of 140°, the amount of jet noise reduction with the exhaust nozzle and the shield is the same as the amount of jet noise reduction with the exhaust nozzle without the shield, and the amount of jet noise reduction with the exhaust nozzle: may be greater than the sum of the amount of jet noise reduction when the shield is used without using the shield.

According to the present embodiment, it is possible to obtain a higher effect than simply expected from the combination of the shield and the exhaust nozzle different from the exhaust nozzle according to the present embodiment.

The exhaust nozzle may have a plurality of protrusions provided on the inner circumference.

According to the exhaust nozzle according to the present embodiment, jet noise during takeoff and landing can be prevented by protruding a part of the inside of the exhaust passage.

The plurality of protrusions may have the same shape and size, and may be provided at equal intervals in the circumferential direction of the exhaust nozzle.

According to this embodiment, the cross-sectional shape of the exhaust flow path can be changed uniformly over the entire circumference.

The number N of the plurality of protrusions may be N>4.

When the number of protrusions N≦4, the amount of increase in noise generated by the exhaust nozzle itself on the side (upstream side) of the rear part of the fuselage is large. Therefore, even if an exhaust nozzle and a shield are used together, an appropriate noise reduction effect cannot be obtained, and it cannot be said to be practical. On the other hand, when N>4, the exhaust nozzles reduce the jet noise from the side (upstream side) to the downstream side of the rear part of the fuselage. You can try to get the effect.

each of the plurality of projections includes two sides projecting in an inner peripheral direction of the exhaust nozzle when the exhaust nozzle is viewed in the axial direction, and the lengths of the two sides are the same;
When the number of the plurality of protrusions is N and the length of one side of the regular N-sided polygon is 1,
The length Rf of one side of the protrusion may be Rf>0.5.

Rf≦0.5 means that the amount of penetration of the projection into the exhaust flow path is small (nearly circular). If the amount of penetration of the projection into the exhaust flow path is small, the desired acoustic change cannot be obtained. Therefore, Rf≦0.5 does not make a clear difference with a circular exit. In other words, the amount of noise reduction when Rf>0.5 is relatively high (that is, compared to when Rf≦0.5), so it is preferable to set Rf>0.5.

The area of the exhaust port of the exhaust nozzle is the same regardless of the number N of the plurality of protrusions and the length Rf of one side of the protrusions.

By equalizing the areas of the exhaust ports of the exhaust nozzles, the values of N and Rf can be appropriately selected.

a sound pressure level of high frequency components of jet noise from the exhaust nozzle having the plurality of protrusions is higher than a sound pressure level of high frequency components of jet noise from the exhaust nozzle having no protrusions;
A sound pressure level of low frequency components of jet noise from the exhaust nozzle having the plurality of protrusions may be lower than a sound pressure level of low frequency components of jet noise from the exhaust nozzle without the plurality of protrusions.

Depending on the shape of the exhaust nozzle, the effect of reducing the jet noise of low frequency components is high, but the jet noise of high frequency components rather increases. However, in this embodiment, the exhaust nozzle is used to generate a source of high frequency content at a location where the shield can shield the high frequency content of the engine exhaust flow. As a result, the shield shields the high frequency components of the engine exhaust flow, thereby reducing the jet noise of the high frequency components. Therefore, although the exhaust nozzle increases the jet noise of high frequency components, the shield can shield the jet noise of high frequency components. For this reason, by using a specific shape of the exhaust nozzle (that is, the exhaust nozzle that is highly effective in reducing the jet noise of the low frequency component, but rather increases the jet noise of the high frequency component) and the shield, the jet noise can be reduced. can be reduced.

The shield reduces a sonic boom caused by the engine exhaust flow by suppressing the engine exhaust flow from flowing around the airframe downward.

According to the present invention, the shield suppresses the flow of the engine exhaust flow toward the lower part of the fuselage, thereby reducing the sonic boom caused by the engine exhaust flow.

The shields may include a pair of shields arranged on the fuselage so as to sandwich the engine exhaust flow.

According to the present invention, the pair of shields suppresses the flow of the engine exhaust flow toward the lower side of the fuselage, thereby reducing the sonic boom caused by the engine exhaust flow.

Having a horizontal stabilizer arranged behind the engine nacelle,
The pair of shields may be arranged on the horizontal stabilizer.

As a result, pressure shielding by the shield can be effectively performed, and sonic boom can be reduced.

The shield may further include the horizontal stabilizer.

The flat horizontal stabilizer effectively shields the pressure from the shield and reduces the sonic boom.

Each said pair of shields may be angled outwardly of said fuselage.

As a result, pressure shielding by the shield can be effectively performed, and sonic boom can be reduced.

Having a rear trunk lift surface provided behind the engine nacelle,
The pair of shields may be arranged on the rear fuselage lift surface and function as a V-tail.

The supersonic aircraft according to this embodiment can also reduce sonic booms by having a pair of shields.

The exhaust nozzle extends to the rear of the engine and forms an exhaust flow path,
The exhaust nozzle has a plurality of main nozzle pieces and one or more connecting nozzle pieces,
The main nozzle piece is provided so that the rear end side thereof can swing inward and outward directions of the exhaust flow path about an opening and closing bent portion formed at the rear end of the narrowed portion at the rear of the engine,
The connecting nozzle piece is arranged between the adjacent main nozzle pieces and is connected to the main nozzle pieces on both sides so as to be bendable, and the connecting nozzle piece bends with the main nozzle piece at the side bent portion. a central bent portion that is removably connected and capable of forming the plurality of protrusions inside the exhaust flow path in conjunction with movement of each of the main nozzle pieces;
When the main nozzle piece swings outward from the exhaust flow path, the connecting nozzle piece forms a flat surface without a protrusion in the exhaust flow path, and the cross-sectional area of the exhaust flow path is the open/close type. widening from the position of the bent portion toward the rear end portion side of the exhaust flow path,
In order to narrow the exhaust flow path, when the main nozzle piece swings inward of the exhaust flow path, the connecting nozzle piece forms a projecting portion along the exhaust flow path in the exhaust flow path. may be formed.

According to the present embodiment, a first state in which a part of the inner side of the exhaust flow path protrudes and a fold-like projection appears on the inner surface side, and a state in which the inner side of the exhaust flow path does not protrude and the above-described By changing between the second state in which the cross-sectional area of the exhaust passage becomes wider toward the rear end, the noise prevention effect during takeoff and landing in the first state and the efficiency during supersonic cruising in the second state. It is possible to achieve both improvement of In addition, between the first state and the second state, only the cross-sectional shape of the exhaust flow path changes and there is no change in the flow path, etc., and noise is reduced without complicating the structure and increasing the size of the exhaust nozzle. In addition, the efficiency during supersonic cruising can be further improved. Furthermore, according to the exhaust nozzle according to the present embodiment, only the opening/closing bent portion of the main nozzle piece is required to be actively movable, and the bent portion between the main nozzle piece and the connecting nozzle piece is moved by swinging of the main nozzle piece. It can be bent automatically to change the cross-sectional shape of the exhaust flow path, and the structure of the exhaust nozzle can be made lightweight and simple without complicating the structure and increasing the size.

The plurality of main nozzle pieces and connecting nozzle pieces may form an entire circumference of an exhaust passage behind the engine.

According to this embodiment, the plurality of main nozzle pieces and the connecting nozzle pieces form the entire circumference of the exhaust passage at the rear of the engine, so that the cross-sectional shape of the exhaust passage can be uniformly changed over the entire circumference. be able to.

When the supersonic aircraft is cruising at supersonic speed, the main nozzle piece swings outward from the exhaust passage,
During takeoff and landing of the supersonic aircraft, the main nozzle piece may swing inwardly of the exhaust passage.

According to the present embodiment, when the main nozzle piece swings inward of the exhaust passage, the cross-sectional area of the rear end of the exhaust passage is less than or equal to the cross-sectional area of the position of the opening/closing bending portion of the exhaust passage. As a result, noise is prevented by the fold-shaped protrusions on the inner surface of the connecting nozzle piece in the first state, and the propulsion efficiency at subsonic speeds such as during takeoff and landing is improved with a shape that tapers toward the rear end side. be able to.

A method for reducing sonic boom and jet noise according to one aspect of the present invention includes:
The shield reduces a sonic boom caused by the engine exhaust flow by shielding the engine exhaust flow ejected from a jet engine housed in an engine nacelle attached to the fuselage of the fuselage of the supersonic aircraft,
The exhaust nozzle provided at the exhaust port of the engine nacelle generates a sound source of the high frequency component at a position where the shield can shield the high frequency component of the engine exhaust flow, thereby suppressing the high frequency component. Jet noise is reduced and low frequency jet noise is reduced by promoting mixing of the low frequency components of the engine exhaust flow with the outside air flow.

According to the present invention, it is possible to solve both the problem of reducing the sonic boom of a supersonic aircraft and the problem of reducing jet noise during takeoff and landing at an airport.

Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

1 is a perspective view showing the appearance of a supersonic aircraft according to one embodiment of the present invention; FIG. FIG. 5 is a plan view showing the appearance of a supersonic aircraft according to another embodiment of the present invention; FIG. 3 is a side view showing the appearance of the supersonic aircraft shown in FIG. 2; FIG. 3 is a front view showing the appearance of the supersonic aircraft shown in FIG. 2; 5 is a graph showing sonic boom waveforms directly below the fuselage with and without fins for confirming the effect of the fins according to the embodiment of the present invention. FIG. 5 is a plan view showing the appearance of a supersonic aircraft according to another embodiment of the present invention; FIG. 7 is a side view showing the appearance of the supersonic aircraft shown in FIG. 6; FIG. 7 is a front view showing the appearance of the supersonic aircraft shown in FIG. 6; It is a figure for demonstrating the concept of this embodiment. FIG. 4 is an explanatory diagram of changes in the cross-sectional shape of an exhaust passage according to one embodiment of the present invention; 1 is a schematic perspective view of an exhaust nozzle in a first state according to one embodiment of the present invention; FIG. FIG. 12 is a front view from the exhaust side of FIG. 11; FIG. 4 is a schematic perspective view of an intermediate state between the first state and the second state of the exhaust nozzle according to one embodiment of the present invention; FIG. 14 is a front view from the exhaust side of FIG. 13; FIG. 4 is a schematic perspective view of an exhaust nozzle in a second state according to one embodiment of the present invention; FIG. 16 is a front view from the exhaust side of FIG. 15; 4 shows variations in the shape of the protrusion of the exhaust nozzle. 4 shows the distribution of sound pressure level versus dimensionless frequency for several different types of exhaust nozzles. 4 is a contour map showing the amount of noise reduction depending on the shape of the protrusion of the exhaust nozzle; It is a figure for demonstrating the method of a confirmation test. The results of confirmation tests for exhaust nozzle #4 are shown. The results of confirmation tests for exhaust nozzle #7 are shown. The results of confirmation tests for exhaust nozzle #1 are shown. FIG. 4 is a contour plot of turbulent kinetic energy (TKE) in the exhaust flow direction when using different exhaust nozzles; FIG. 4 is a contour plot of TKE near the outlet of an exhaust nozzle when using different exhaust nozzles. The amount of change in sound pressure level with respect to different polar angles is shown when the sound pressure level at a polar angle of 90° is used as a reference. FIG. 12 is a side view of a case (comparative example) in which a circular exit exhaust nozzle (Baseline) was used in the second confirmation test. FIG. 11 is a side view of a case where a petal-shaped exhaust nozzle is used (this embodiment) in a second verification test; It is a side cross-sectional view showing a second confirmatory test. It is a top view which shows a 2nd confirmatory test. It is the figure which looked at the 2nd confirmation test from the exhaust port side of the exhaust nozzle. It is a perspective view which shows a 2nd confirmatory test. 4 shows the results of a second confirmation test for exhaust nozzle #4. FIG. 10 shows the results of a second confirmation test for exhaust nozzle #7; FIG. Figure 2 shows the results of a second validation test for exhaust nozzle #1; Figure 3 shows the results of a second confirmation test for exhaust nozzle #5.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. Configuration of a supersonic aircraft

FIG. 1 is a perspective view showing the appearance of a supersonic aircraft according to one embodiment of the present invention.

As shown in FIG. 1, a supersonic aircraft according to an embodiment of the present invention includes a pair of engine nacelles 312R and 312L attached to a fuselage 311 of a fuselage 310, a pair of fins 313R and 313L, an engine nacelle 312R, It has a pair of horizontal stabilizers 314R and 314L arranged behind 312L.

The pair of fins 313R, 313L are arranged rearwardly and downwardly of the engine nacelles 312R, 312L. This pair of fins 313R and 313L functions as a shield. The shield (i.e., the pair of fins 313R, 313L) shields the engine exhaust flow ejected from the jet engine (not shown) housed in the engine nacelles 312R, 312L, thereby directing the engine exhaust flow downward to the fuselage 310. to suppress the wraparound, thereby reducing the sonic boom.

The right fin 313R includes a horizontal fin 313′R having the same shape as the horizontal stabilizer 314R, and a tip fin 313″R standing on the right end of the horizontal fin 313′R. "R" is provided on the horizontal fin 313'R so as to incline to the outside of the fuselage 310 (counterclockwise when viewed from the front side in the machine axis direction). The left fin 313L includes a horizontal fin 313′L having the same shape as the horizontal stabilizer 314L, and a tip fin 313″L erected on the left end of the horizontal fin 313′L. "L" is provided on the horizontal fin 313'L so as to incline to the outside of the fuselage 310 (clockwise when viewed from the front side in the machine axis direction). Sonic boom can be reduced by appropriately inclining the tip fins 313″R and 313″L.

A pair of horizontal fins 313′R, 313′L are positioned below the engine exhaust flow, and a pair of tip fins 313″R, 313″L are positioned to sandwich the engine exhaust flow. More specifically, the pair of horizontal fins 313′R, 313′L and the pair of wingtip fins 313″R, 313″L are each configured symmetrically with respect to a plane of symmetry that vertically crosses the axis of the fuselage 310. be done.

The supersonic aircraft according to this embodiment may have fins 313R, 313L to reduce the effect of engine exhaust flow on the sonic boom.

2 is a plan view showing the appearance of a supersonic aircraft according to another embodiment of the present invention, FIG. 3 is its side view, and FIG. 4 is its front view.

As shown in FIGS. 2 to 4, the supersonic aircraft according to this embodiment includes a pair of engine nacelles 12R and 12L attached to the fuselage 11 of the airframe 10, a pair of fins 13R and 13L, an engine nacelle 12R, It has a pair of horizontal stabilizers 14R and 14L arranged behind 12L.

A pair of fins 13R and 13L functions as a shield. Alternatively, the pair of fins 13R, 13L and the pair of horizontal stabilizers 14R, 14L function as shields. In other words, the shield includes a pair of fins 13R, 13L and may further include a pair of tailplanes 14R, 14L. The shield (that is, the pair of fins 13R, 13L, or the pair of fins 13R, 13L and the pair of tail planes 14R, 14L) is ejected from jet engines (not shown) accommodated in the engine nacelles 12R, 12L. By shielding the engine exhaust flow 15 from the fuselage 10, the engine exhaust flow 15 is restrained from going around to the lower side of the fuselage 10, thereby reducing the sonic boom.

The fins 13R, 13L are arranged on the fuselage 10, typically on the horizontal stabilizers 14R, 14L, respectively, so as to sandwich the engine exhaust flow 15 therebetween. More specifically, the pair of fins 13R, 13L and the pair of horizontal stabilizers 14R, 14L are arranged symmetrically with respect to the plane of symmetry that vertically crosses the axis of the fuselage 10, and the fins 13R are arranged on the horizontal stabilizer 14R. and the fin 13L is mounted on the horizontal stabilizer 14L.

As shown in FIG. 4 , the pair of fins 13R and 13L are each slanted to the outside of the fuselage 10. As shown in FIG. By properly inclining the fins 13R and 13L in this manner, the sonic boom can be reduced.

The supersonic aircraft according to this embodiment may have fins 13R, 13L to reduce the effect of the engine exhaust flow 15 on the sonic boom.

FIG. 5 is a graph showing sonic boom waveforms directly below the fuselage with the fins 13R and 13L (70d) and without the fins 13R and 13L (70e).

The calculation conditions are
Altitude: 14.4km
Mach number: 1.6
Angle of attack: 2.76 degrees 100% thrust.

From FIG. 5, the pressure is higher with the fins 13R and 13L. It can be seen from this that having the fins 13R, 13L reduces the effect of the engine exhaust flow 15 on the sonic boom.

6 is a plan view showing the appearance of a supersonic aircraft according to another embodiment of the present invention, FIG. 7 is its side view, and FIG. 8 is its front view.

As shown in FIGS. 6 to 8, a supersonic aircraft according to another embodiment of the present invention includes a pair of engine nacelles 212R, 212L attached to a fuselage 211 of a fuselage 210, and a pair of engine nacelles 212R, 212L. and a pair of shields 213R and 213L arranged in the same direction.

A pair of shields 213R and 213L are attached to a rear fuselage lift surface 214 provided behind the engine nacelles 212R and 212L so as to incline to the outside of the fuselage.

The pair of shields 213R and 213L shields the engine exhaust flow jetted from the jet engine (not shown) housed in the engine nacelles 212R and 212L, thereby suppressing the engine exhaust flow from entering the fuselage 211. This reduces the sonic boom. Also, the pair of shields 213R and 213L has a function as a V-tail.

The supersonic aircraft according to this embodiment can also reduce sonic booms by having a pair of shields 213R and 213L.

2. Concept of this embodiment

FIG. 9 is a diagram for explaining the concept of this embodiment.

The shield of each of the above embodiments (shield 13 in FIG. 9) reduces sonic boom during supersonic cruise as described above. However, the shield 13 is less effective in reducing jet noise during takeoff and landing at an airport. The principle will be described with reference to FIG. 9(A).

FIG. 9A schematically shows a comparative example. (A) of FIG. 9 shows the shield 13 provided in the fuselage of the supersonic aircraft, the exhaust nozzle 200 provided at the exhaust port of the engine nacelle, the engine exhaust flow 15 ejected from the exhaust nozzle 200, is schematically shown. The exhaust nozzle 200 of the comparative example is not a nozzle designed for low noise, but a nozzle having a circular exit without a protrusion.

The sources of jet noise generated by the engine exhaust flow 15 ejected from the exhaust nozzles 200 are dispersed away from the aft fuselage. On the other hand, the shield 13 is typically a fin attached to the horizontal stabilizer. In a positional relationship in which the shield 13 is provided on the horizontal stabilizer and the jet noise source is located away from the rear of the fuselage (that is, behind the horizontal stabilizer), the shield 13 cannot shield most of the jet noise.

The sound source distribution of the jet noise generated by the engine exhaust flow 15 has a sound source of high frequency components on the upstream side of the engine exhaust flow 15 (that is, on the side close to the aft part of the fuselage) and a sound source of low frequency components on the downstream side. The shield 13 cannot shield low-frequency components, and only shields part of high-frequency components near the airframe. Its contribution to overall jet noise is small and does not provide effective noise reduction.

As described above, the shield 13 provided on the horizontal stabilizer cannot reduce the jet noise during takeoff and landing at the airport.

On the other hand, in the present embodiment, the sonic boom during supersonic cruising is reduced by providing a shield 13 on the body of the supersonic aircraft, and furthermore, by using this shield 13, during takeoff and landing at the airport Aims to reduce jet noise. Therefore, in this embodiment, as shown in FIG. 9B, an exhaust nozzle 100 designed for low noise is used. Exhaust nozzle 100 is, for example, a chevron nozzle, a petal-shaped folding nozzle, or other low-noise nozzle that promotes mixing. In this embodiment, as the exhaust nozzle 100, a petal-shaped folding nozzle is employed.

FIG. 9B schematically shows this embodiment. FIG. 9B shows a shield 13 provided in the fuselage of the supersonic aircraft, an exhaust nozzle 100 provided at the exhaust port of the engine nacelle, an engine exhaust flow 15 ejected from the exhaust nozzle 100, is schematically shown.

The exhaust nozzle 100, which promotes mixing, such as a petal-shaped folding nozzle, is effective in reducing low-frequency component jet noise propagating in the downstream direction and having a sound source located downstream away from the rear of the fuselage. be. Specifically, the exhaust nozzle 100 reduces low frequency jet noise by promoting mixing of the low frequency components of the engine exhaust flow 15 at a downstream location away from the aft fuselage with the outside air flow ( arrow pointing down to indicate image).

On the other hand, the exhaust nozzle 100 that promotes mixing, such as a petal-shaped folding nozzle, is less effective in reducing noise of high-frequency components, and depending on the design, noise of high-frequency components may increase (the upward arrow indicates image). Therefore, in this embodiment, the shield 13 is used to reduce the sonic boom during supersonic cruising, thereby reducing jet noise of high frequency components. In other words, jet noise of low frequency components is reduced by enhanced mixing of the exhaust nozzle 100 , while jet noise of high and low frequency components is reduced using the shield 13 . This is the concept of this embodiment.

Since the purpose of the shield 13 is to reduce the sonic boom, the position of the shield 13 is predetermined as a position effective in reducing the sonic boom. Typically, the position of the shield 13 is the position of the horizontal stabilizer. Therefore, in this embodiment, the exhaust nozzle 100 is used to generate a sound source of high frequency components at a position where the shield 13 at this predetermined position can shield the high frequency components of the engine exhaust flow 15 .

FIG. 24 is a contour plot of TKE (Turbulent Kinetic Energy) in the exhaust flow direction when using different exhaust nozzles. FIG. 25 is a contour plot of the TKE near the outlet of the exhaust nozzle when using different exhaust nozzles.

Mixing-promoting exhaust nozzles 100, such as petal-shaped folded nozzles, may increase high-frequency noise, but also displace high-frequency sound sources. As shown in FIGS. 24 and 25, the petal-shaped exhaust nozzles #4 and #7 (the configuration of which will be described in more detail later), particularly the TKE near the exhaust port (x/D=0) of exhaust nozzle #4. is greater than that of TKE near the outlet of the circular exhaust nozzle (Baseline). This means that the petal-shaped exhaust nozzles #4 and #7, especially the exhaust nozzle #4, move the source of the high frequency components closer to the exhaust (further upstream). The reason why such a phenomenon occurs will be explained.

An exhaust nozzle 100 for promoting mixing, such as a petal-shaped fold-in nozzle, has a projecting portion penetrating into the exhaust flow path near the exhaust port. If the amount of penetration of the protrusion into the exhaust passage is large, the turbulence (TKE) in the vicinity of the protrusion (that is, in the vicinity of the exhaust port) increases. Airflow turbulence (TKE) near the lobes (ie, near the exhaust) promotes early (ie, upstream) mixing of the engine exhaust flow and the outside airflow. For this reason, relatively large-scale disturbances, which are sources of low-frequency components, are weakened downstream. On the other hand, upstream, relatively small-scale disturbances that act as sound sources for high-frequency components are intensified, and as a result, the position of the high-frequency sound source occurs on the upstream side.

In the present embodiment, by using such an exhaust nozzle 100, the position of the sound source of the high-frequency component is blocked by the shield 13 from a position that cannot be shielded by the shield 13 (see FIG. 9A). Move to a possible position (see FIG. 9B). Specifically, the sound source of the high frequency component is moved from a position further away from the rear part of the fuselage (see (A) in FIG. 9) to a position closer to the rear part of the fuselage (see (B) in FIG. 9). As a result, the shield 13 can shield the high frequency components of the engine exhaust flow 15, so that the jet noise of the high frequency components can be reduced.

FIG. 26 shows the amount of change ΔOASPL in the sound pressure level (OASPL) for different polar angles when the sound pressure level at the polar angle of 90° is used as a reference. Specifically, FIG. 26 shows (A) the amount of change in the sound pressure level (OASPL) of the jet noise, (B) the amount of change in the sound pressure level (OASPL) due to the propagation distance (diffusion attenuation), and (A + B) the observer indicates the amount of change in the sound pressure level (OASPL) of the sound reaching the . The vertical axis indicates that the larger the value on the negative side (that is, on the side of less than 0), the smaller the noise compared to the sound pressure level at a polar angle of 90°. Conversely, the larger the value on the positive side (that is, the side greater than 0), the louder the noise compared to the sound pressure level at the polar angle of 90°.

The polar angle is the range of angles with 0° at the nose of the fuselage, 90° at the outlet of the exhaust nozzle, and 180° at the aft of the fuselage. As shown in FIG. 26, the effect of polar angle is uneven when reducing jet noise for an aircraft flying level overhead. The jet noise of commercial supersonic aircraft, which is expected to enter service in the future, has a maximum distribution at a polar angle of 140° to 160°. In addition, noise decreases in inverse proportion to the square of the propagation distance due to diffusion attenuation, and is greatly attenuated when propagating in the downstream direction (160° or the like) where the distance to the observer is long. For this reason, the noise felt by the observer becomes maximum near the polar angle of 140° to 150° (see FIG. 26). In this embodiment, the combined use of the exhaust nozzle 100 and the shield 13 is intended to enhance the noise reduction effect particularly near the polar angle of 140°.

3. Exhaust nozzle configuration

FIG. 10 is an explanatory diagram of changes in the cross-sectional shape of the exhaust passage according to one embodiment of the present invention. FIG. 11 is a schematic perspective view of an exhaust nozzle in a first state according to one embodiment of the present invention; 12 is a front view from the exhaust side of FIG. 11. FIG. FIG. 13 is a schematic perspective view of an intermediate state between the first state and the second state of the exhaust nozzle according to one embodiment of the present invention. 14 is a front view from the exhaust side of FIG. 13. FIG. FIG. 15 is a schematic perspective view of an exhaust nozzle in a second state according to one embodiment of the present invention; 16 is a front view from the exhaust side of FIG. 15. FIG.

Exhaust nozzles 100 are provided at the exhaust ports of the engine nacelles 312R, 312L, 12R, 12L, 212R, and 212L in each of the above embodiments. The exhaust nozzle 100 according to one embodiment of the present invention is a foldable exhaust nozzle whose shape is variable between a petal-shaped first state and a circular second state, and is a low-noise nozzle that promotes mixing. is. A representative example of the configuration of the exhaust nozzle 100 will be described below.

As shown in FIGS. 10 to 16, the exhaust nozzle 100 according to one embodiment of the present invention can swing inward and outward directions of the exhaust flow path 101 on the rear end side centering on the opening and closing bent portion 111 at the rear of the jet engine. and a plurality of connecting nozzle pieces 120 arranged between adjacent main nozzle pieces 110, and the plurality of main nozzle pieces 110 and connecting nozzle pieces 120 are It constitutes the entire circumference of the exhaust passage 101 at the rear of the jet engine.

The main nozzle piece 110 is configured to be swingable by an actuator (not shown) about an opening/closing bent portion 111 at the rear end of the constricted portion 103. By swinging the main nozzle piece 110, the exhaust flow shown on the left side of FIG. Between the petal-shaped first state in which the rear end of the passage 101 has the narrowest cross-sectional area and the circular second state in which the rear end of the exhaust passage 101 has the widest cross-sectional area shown on the right side of FIG. In the petal-shaped first state, the connecting nozzle piece 120 bends and protrudes inward of the exhaust flow path 101, and in the circular second state, the connecting nozzle piece 120 extends inside the exhaust flow path 101. The cross-sectional area of the exhaust passage 101 becomes wider toward the rear end without protruding.

11 and 12 showing the petal-shaped first state of the exhaust nozzle 100 according to one embodiment of the present invention, and FIGS. 13 and 14 showing an intermediate state between the petal-shaped first state and the circular second state. , and FIG. 15 and FIG. 16 showing the circular second state.

11 to 16 omit the shape of the main nozzle piece 110 and the connecting nozzle piece 120 in the thickness direction, and show them as a uniform thin plate that defines only the inner surface side of the exhaust flow path 101 .

In this embodiment, the constricted portion 103 is formed in a truncated cone shape with the smallest cross-sectional area at the rear end. The opening/closing bent portion 111 is formed by hinge-connecting the constricted portion 103 and the main nozzle piece 110 .

The main nozzle piece 110 is formed so that the width in the circumferential direction becomes smaller from the opening/closing bent portion 111 toward the rear end. A possible connecting nozzle piece 120 is provided.

The connecting nozzle piece 120 is connected to the main nozzle pieces 110 on both sides so as to be bendable by the side bent portions 121, and has a central bent portion 122 forming a projecting portion in the center.

In this embodiment, the connecting nozzle piece 120 is composed of two members that are hinged at the central bent portion 122, and the side bent portions 121 are also hinged.

In the petal-shaped first state in which the main nozzle piece 110 is in the most swung position in the exhaust passage 101 and the cross-sectional area of the rear end of the exhaust passage 101 is the narrowest, FIGS. As shown, the rear end of the main nozzle piece 110 is located slightly inside the exhaust flow path 101 relative to the opening/closing bent portion 111 , and the connecting nozzle piece 120 is bent at the side when viewed from the outer circumference of the exhaust nozzle 100 . The portion 121 is largely mountain-folded, and the central bent portion 122 is largely valley-folded, and the portion of the central bent portion 122 forms a projecting portion 102 projecting inwardly of the exhaust flow path 101 .

When the actuator (not shown) swings the main nozzle piece 110 outward from the exhaust passage 101 from the above state, the rear end of the main nozzle piece 110 spreads outward as shown in FIGS. As the connecting nozzle piece 120 moves, the mountain-folded state of the side curved portion 121 and the valley-folded state of the central curved portion 122 of the connecting nozzle piece 120 gradually become smaller, and the portion of the central curved portion 122 moves toward the inside of the exhaust flow path 101. The protruding portion 102 protruding to the side is also reduced.

15 and 16 show the circular second state in which the main nozzle piece 110 is at the position where the main nozzle piece 110 is swung most outward from the exhaust passage 101 and the cross-sectional area of the rear end portion of the exhaust passage 101 is the widest. , the central bent portion 122 of the connecting nozzle piece 120 is no longer bent, there is no projecting portion 102 projecting inward of the exhaust passage 101, and the rear end portion of the main nozzle piece 110 is behind the opening/closing bent portion 111. With the connecting nozzle piece 120, the rear end has a shape similar to a truncated cone with the largest cross-sectional area.

From the above state, when the main nozzle piece 110 is swung inwardly of the exhaust flow path 101 by an actuator (not shown), the petal-shaped second nozzle shown in FIGS. 1 state.

The shapes and thicknesses of the constricted portion 103, the main nozzle piece 110, and the connecting nozzle piece 120 on the outer peripheral side may be appropriately designed in consideration of the aerodynamic characteristics during flight.

Further, as shown in FIG. 10, by making the shape of the outer peripheral side of the connecting nozzle piece 120 into a triangular pyramid shape, it is possible to define the bending limit of the central bent portion 122 and the side bent portions 121, and the above-mentioned petals. The first state of the shape and the second state of the circle can be reliably secured.

The cross-sectional area of the exhaust flow path 101 that varies depending on the exhaust nozzle 100 will be described. In the petal-shaped first state, the area behind the position of the opening/closing bent portion 111 has a tapered cross-sectional area suitable for takeoff and landing. In the circular second state, the area behind the position of the opening/closing bent portion 111 has a tapered diverging cross-sectional area suitable for supersonic cruising. 10 to 12, in the petal-shaped first state, the connecting nozzle piece 120 bends inwardly of the exhaust flow path 101 to form the projecting portion 102, so that the shape of the exhaust flow is changed. It bends like a fold. The Mach number distribution of the exhaust jet becomes a pleated distribution. This promotes mixing of the exhaust flow and the outside air flow, and can reduce jet noise during takeoff and landing at an airport.

Exhaust nozzle 100, among other things, reduces jet noise of low frequency components by promoting mixing of the low frequency components of the engine exhaust stream with the ambient air stream.

4. Variations in the shape of the protrusion of the exhaust nozzle

FIG. 17 shows variations in the shape of the protrusion of the exhaust nozzle.

Variations in the shape of the projecting portion 102 when the exhaust nozzle 100 is in the petal-shaped first state (corresponding to FIG. 12) will be described. The exhaust nozzle 100 has a plurality of (that is, N) protrusions 102 provided on the inner circumference of the exhaust nozzle 100 . The plurality of protrusions 102 have the same shape and size, and are provided at equal intervals in the circumferential direction of the exhaust nozzle 100 . Each of the plurality of protrusions 102 includes two sides protruding in the inner circumferential direction of the exhaust nozzle 100 when the exhaust nozzle 100 is viewed in the axial direction, and the two sides have the same length Rf, Rf. The length Rf of one side of the N protrusions 102 is defined as the length of one side of the regular N-sided polygon formed by the exhaust port of the exhaust nozzle 100, where the length of one side of the regular N-sided polygon formed by the exhaust port of the exhaust nozzle 100 is 1. means the length of the side folded inside the

The area of the exhaust port of the exhaust nozzle 100 is the same regardless of the number N of the plurality of projecting portions 102 and the length Rf of one side of the projecting portion. In other words, the exit cross-sectional areas of the exhaust ports of the five types of exhaust nozzles #1, #4, #5, #7, and #8 are all equal.

Exhaust nozzle #1 has N=4 protrusions. Assuming that the length of one side of the regular quadrangle formed by the exhaust port of the exhaust nozzle #1 is 1, the length of one side of the protrusion is Rf=0.59. In other words, the length Rf of one side of the projecting portion is 59% of the length of one side of the regular quadrangle formed by the exhaust port of the exhaust nozzle #1.

Exhaust nozzle #4 has N=8 protrusions as in FIG. Assuming that the length of one side of the regular octagon formed by the exhaust port of the exhaust nozzle #4 is 1, the length of one side of the protrusion is Rf=0.75. In other words, the length Rf of one side of the protrusion is 75% of the length of one side of the regular octagon formed by the exhaust port of the exhaust nozzle #4.

Exhaust nozzle #5 has N=12 protrusions. Assuming that the length of one side of the regular dodecagon formed by the exhaust port of the exhaust nozzle #5 is 1, the length of one side of the protrusion is Rf=0.62. In other words, the length Rf of one side of the protrusion is 62% of the length of one side of the regular dodecagon formed by the exhaust port of the exhaust nozzle #5.

Exhaust nozzle #7 has N=16 protrusions. Assuming that the length of one side of the regular hexagon formed by the exhaust port of the exhaust nozzle #7 is 1, the length of one side of the protrusion is Rf=0.77. In other words, the length Rf of one side of the protrusion is 77% of the length of one side of the regular hexagon formed by the exhaust port of the exhaust nozzle #7.

Exhaust nozzle #8 has N=16 protrusions. Assuming that the length of one side of the regular hexagon formed by the exhaust port of the exhaust nozzle #8 is 1, the length of one side of the projection is Rf=0.42. In other words, the length Rf of one side of the protrusion is 42% of the length of one side of the regular hexagon formed by the exhaust port of the exhaust nozzle #8.

5. Reduction effect of exhaust nozzle jet noise when no shield is provided

FIG. 18 shows the distribution of sound pressure level versus dimensionless frequency for several different types of exhaust nozzles.

FIG. 18 shows the sound pressure levels SPL of three types of exhaust nozzles #4, #7, #8 and an exhaust nozzle having no protrusion (reference value: Baseline) with respect to the dimensionless frequency St when the shield 13 is not provided. (Sound Pressure Level) distribution. (a) shows the distribution of the sound pressure level SPL at a polar angle of 90° and (b) at a polar angle of 160°. The polar angle is the range of angles with 0° at the nose of the fuselage, 90° at the outlet of the exhaust nozzle, and 180° at the aft of the fuselage. That is, (a) shows the distribution of the sound pressure level SPL on the side (upstream side) of the rear part of the fuselage, and (b) shows the distribution of the sound pressure level SPL on the downstream side.

The sound pressure levels of the low-frequency components of jet noise from exhaust nozzle #4 at both the side of the aft fuselage in (a) and the downstream side in (b) are lower than the sound pressure level of the low frequency components of Furthermore, the sound pressure level of the low-frequency component of the exhaust nozzle #4 is lower than that of the exhaust nozzles #7 and #8 both on the side of the rear part of the fuselage in (a) and on the downstream side in (b). In particular, the amount of reduction in the sound pressure level of the low-frequency component of the jet noise from the exhaust nozzle #4 relative to the baseline is greater on the side of the aft fuselage in (a) than on the downstream side in (b).

However, the sound pressure level of the high-frequency components of the jet noise from exhaust nozzle #4, both on the side of the aft fuselage in (a) and on the downstream side in (b), is higher than that of the exhaust nozzle without protrusions (Baseline). Higher than the sound pressure level of high frequency components of jet noise. In particular, the increase in the sound pressure level of the high-frequency component of the jet noise from the exhaust nozzle #4 relative to the baseline is greater on the side of the aft fuselage in (a) than on the downstream side in (b).

In other words, the exhaust nozzle #4 has the highest effect of reducing jet noise of low frequency components, but rather increases jet noise of high frequency components.

The sound pressure levels of all frequency components of the exhaust nozzle #7 are lower than the baseline both on the side of the aft fuselage in (a) and downstream in (b). That is, exhaust nozzle #7 reduces jet noise in a well-balanced manner. However, the sound pressure level of the low frequency components of the exhaust nozzle #7 is higher than that of the exhaust nozzle #4 both laterally and downstream of the aft portion of the fuselage. In other words, the effect of reducing the jet noise of the low frequency component is higher for the exhaust nozzle #4 than for the exhaust nozzle #7.

Exhaust nozzle #8 has sound pressure levels of all frequency components on the side of the rear part of the fuselage in (a) lower than Baseline, but never lower than exhaust nozzle #7. On the other hand, for the exhaust nozzle #8, the sound pressure levels of all frequency components are substantially equal to the baseline on the downstream side of (b). In other words, the exhaust nozzle #8 has a relatively low effect of reducing jet noise on the side of the rear part of the fuselage, and almost no effect of reducing jet noise on the downstream side.

FIG. 19 is a contour map showing the amount of noise reduction depending on the shape of the protrusion of the exhaust nozzle.

FIG. 19 shows the noise reduction amount ΔOASPL (=OASPL-OASPL Baseline) (dB) with respect to the noise level (OASPL Baseline) of an exhaust nozzle having no protrusion (reference value: Baseline) when the shield 13 is not provided. . FIG. 19 shows the noise reduction amount ΔOASPL of exhaust nozzles #1, #4, #7, #8 and exhaust nozzles #2, #3, #5, #6, #9, #10 having another variation of shape. indicates The exit cross-sectional areas of the exhaust ports of the exhaust nozzles #1 to #10 are all equal, and the number N of protrusions and the length Rf of one side of the protrusions are different. FIG. 19(a) shows the noise reduction amount ΔOASPL of the exhaust nozzles #1 to #10 with a polar angle of 90°, (b) with a polar angle of 120°, and (c) with a polar angle of 160°. On the scale in the figure below, the closer the ΔOASPL = -2.2 dB (negative side), the greater the noise reduction amount (left side of the scale), and conversely, the closer the ΔOASPL = 2.2 dB (positive side), the greater the noise increase amount. (right side of the scale) means

The XY coordinate system of the contour map indicates the shape of the exhaust nozzles #1 to #10. The X-axis indicates the number N of protrusions of the exhaust nozzles #1-#10. When the length of one side of the projecting portion Rf (that is, the length of one side of the regular N-polygon formed by the exhaust port of the exhaust nozzle) is 1, the Y-axis is the exhaust port with respect to one side of the regular N-polygon. length of the side to be folded inside). For example, the XY coordinates of the exhaust nozzle #4 mean that the number N of protrusions of the exhaust nozzle #4 is 8 and the length of one side of the protrusion is Rf=0.75.

At the polar angle of 90° in (a) and the polar angle of 120° in (b), the noise reduction amount of the exhaust nozzles #1 and #2 where N≦4 (specifically, N=4) is positive. value, which means that the amount of noise increase is large. On the other hand, the noise reduction amount of the exhaust nozzles #3 to #10 (N>4) is a negative value, and the noise is reduced. Therefore, N>4 (in other words, N≧5) is preferred.

Therefore, focusing on N>4, the noise reduction amount in the case of Rf≦0.5 at all polar angle positions (90°, 120°, 160°) is relatively (that is, Rf>0. 5) low. In particular, when the polar angle is 160° in (c) and Rf≦0.5, the range of N where the amount of noise reduction is small is wide. Rf≦0.5 means that the amount of penetration of the projection into the exhaust flow path is small (nearly circular). If the amount of penetration of the projection into the exhaust flow path is small, the desired acoustic change cannot be obtained. Therefore, Rf≦0.5 does not make a clear difference with a circular exit. In other words, the amount of noise reduction when Rf>0.5 is relatively high (that is, compared to when Rf≦0.5), so it is preferable to set Rf>0.5.

6. Confirmation test of noise reduction effect when exhaust nozzle and shield are used together: first confirmation test

A confirmation test was conducted to confirm the reduction in jet noise when the exhaust nozzle 100 and the shield 13 are used together.

FIG. 20 is a diagram for explaining the confirmation test method.

For each of the three types of exhaust nozzles #1, #4, and #7, (a) when exhaust nozzles #1, #4, and #7 are used and shield 13 is not used, (b) when shield 13 is used , when using an exhaust nozzle with a circular exit, and (c) when using exhaust nozzles #1, #4, #7 and shield 13 together. (c) Combined use of the exhaust nozzles #1, #4, #7 and the shield 13 is an example of this embodiment. On the other hand, (a) and (b) are comparative examples. I modeled the port nozzle and turned on the jet engine. A microphone was installed behind the port nozzle model in the exhaust direction, and the noise reduction (dB) was measured in the range of polar angles = 90° to 160°. The polar angle is the range of angles with 0° at the nose of the fuselage, 90° at the outlet of the exhaust nozzle, and 180° at the aft of the fuselage.

FIG. 21 shows the results of confirmation tests for exhaust nozzle #4.

FIG. 21 shows (a) the case where the exhaust nozzle #4 is used and the shield 13 is not used (comparative example), and (b) the case where the shield 13 is used and an exhaust nozzle with a circular exit is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #4 and shield 13 are used together (this embodiment). A larger value on the negative side (that is, less than 0) indicates a larger amount of noise reduction. Conversely, the larger the value on the positive side (that is, the side greater than 0), the larger the amount of increase in noise.

In the polar angle range of 110° or more and 140° or less, the amount of jet noise reduction when (c) the exhaust nozzle #4 and the shield 13 are used together (this embodiment) is as follows: is greater than the jet noise reduction amount when the shield 13 is not used (comparative example) (c>a).

On the other hand, in the polar angle range of greater than 140° and less than or equal to 160°, the amount of jet noise reduction in the case of (c) using both the exhaust nozzle #4 and the shield 13 (this embodiment) is almost unchanged. In other words, even in the polar angle range of greater than 140° and less than or equal to 160°, (c) when exhaust nozzle #4 and shield 13 are used together (this embodiment), the amount of jet noise reduction is sufficiently large.

Furthermore, in the polar angle range of 120° or more and 140° or less, the amount of jet noise reduction when (c) the exhaust nozzle #4 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle #4 is greater than the sum of the jet noise reduction amount when the shield 13 is not used (comparative example) and the jet noise reduction amount when (b) only the shield 13 is used (comparative example) ( c>a+b). In other words, (c) the combined use of the exhaust nozzle #4 and the shield 13 (this embodiment) provides a simply expected effect (total value of a+b) in the polar angle range of 120° or more and 140° or less. higher effect can be obtained.

As described with reference to FIG. 18, exhaust nozzle #4 has the highest effect of reducing jet noise of low frequency components, but rather increases jet noise of high frequency components. However, in this embodiment, as described with reference to FIG. , to generate a sound source with high frequency components. As a result, the shield 13 shields the high frequency components of the engine exhaust flow 15, thereby reducing the jet noise of the high frequency components. Therefore, although the exhaust nozzle #4 increases the jet noise of high frequency components (see FIG. 18), the shield 13 can shield the jet noise of high frequency components. Therefore, when (c) the exhaust nozzle #4 and the shield 13 are used together (this embodiment), compared to (a) when the exhaust nozzle #4 is used and the shield 13 is not used (comparative example), Jet noise can be significantly reduced.

FIG. 22 shows the results of confirmation tests for exhaust nozzle #7.

FIG. 22 shows (a) the case where the exhaust nozzle #7 is used and the shield 13 is not used (comparative example), (b) the case where the shield 13 is used and an exhaust nozzle with a circular exit is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #7 and shield 13 are used together (this embodiment).

In the polar angle range of 110° or more and 160° or less, the amount of jet noise reduction when (c) the exhaust nozzle #7 and the shield 13 are used together (this embodiment) is as follows: is greater than the jet noise reduction amount when the shield 13 is not used (comparative example) (c>a). As shown in FIG. 21, when the exhaust nozzle #4 and the shield 13 are used together, the amount of jet noise reduction is greater than that of the comparative example (a) in the polar angle range of 110° or more and 140° or less. Therefore, by using the exhaust nozzle #7 and the shield 13 together, the jet noise can be reduced in a wider range and in a well-balanced manner.

Furthermore, in the polar angle range of 140° or more and 160° or less, the amount of jet noise reduction when (c) the exhaust nozzle #7 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle #7 is greater than the sum of the jet noise reduction amount when the shield 13 is not used (comparative example) and the jet noise reduction amount when (b) only the shield 13 is used (comparative example) ( c>a+b). In other words, (c) the combined use of the exhaust nozzle #7 and the shield 13 (this embodiment) provides a simply expected effect (total value of a+b) in the polar angle range of 140° or more and 160° or less. higher effect can be obtained.

As described above, by using (c) the exhaust nozzle #4 or #7 and the shield 13 together (this embodiment), the (c) exhaust nozzle 100 and The reduction in jet noise with the shield 13 is greater than (a) the reduction in jet noise with the exhaust nozzle 100 without the shield 13, and furthermore, at a polar angle of 140°, a simple It is possible to obtain an effect higher than the expected effect (the sum of a+b).

The effect of polar angle is uneven when reducing jet noise for an aircraft flying level overhead. The jet noise of commercial supersonic aircraft, which is expected to enter service in the future, has a maximum distribution at a polar angle of 140° to 160°. In addition, noise decreases in inverse proportion to the square of the propagation distance due to diffusion attenuation, and is greatly attenuated when propagating in the downstream direction (160° or the like) where the distance to the observer is long. For this reason, the noise felt by the observer becomes maximum near the polar angle of 140° to 150° (see FIG. 26). In this embodiment, by using both the exhaust nozzle 100 and the shield 13, the noise reduction effect can be enhanced especially near the polar angle of 140°.

FIG. 23 shows the results of confirmation tests for exhaust nozzle #1.

FIG. 23 shows (a) the case where the exhaust nozzle #1 is used and the shield 13 is not used (comparative example), and (b) the case where the shield 13 is used and a circular exit exhaust nozzle is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #1 and shield 13 are used together (this embodiment).

In the polar angle range of 90° or more and 160° or less, the amount of jet noise reduction when (c) the exhaust nozzle #1 and the shield 13 are used together (this embodiment) is as follows: is greater than the jet noise reduction amount when the shield 13 is not used (comparative example) (c>a).

Furthermore, in the polar angle range of 90° or more and 160° or less, the jet noise reduction amount when (c) the exhaust nozzle #1 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle #1 is greater than the sum of the jet noise reduction amount when the shield 13 is not used (comparative example) and the jet noise reduction amount when (b) only the shield 13 is used (comparative example) ( c>a+b). In other words, (c) by using the exhaust nozzle #1 and the shield 13 together (this embodiment), it is possible to obtain an effect higher than the simply expected effect (the total value of a+b).

However, the value of ΔOASPL in the comparative example (a) on the positive side (that is, on the side greater than 0) is too high in the first place, that is, the amount of increase in noise is too large in the first place. This is as explained with reference to FIGS. 19(a) and 19(b) that the noise increase amount of the exhaust nozzle #1 is large (positive value) at the polar angles of 90° and 120°. Since the amount of increase in noise generated by the exhaust nozzle #1 itself is too large in the first place, even if the shield 13 is used together, the amount of increase in noise is still large. That is, even if the exhaust nozzle #1 and the shield 13 are used together, an appropriate noise reduction effect cannot be obtained, and it cannot be said to be practical.

7. Confirmation test of noise reduction effect when exhaust nozzle and shield are used together: second confirmation test

Next, still another confirmation test for confirming the reduction in jet noise when the exhaust nozzle 100 and the shield 13 are used together will be described.

27 to 32 are diagrams showing the state of the second confirmation test. FIG. 27 is a side view of a case (comparative example) in which the circular outlet exhaust nozzle 200 (Baseline) was used in the second confirmation test. FIG. 28 is a side view when the petal-shaped exhaust nozzle 100 is used (this embodiment) in the second confirmation test.

FIG. 29 is a side sectional view showing the second confirmatory test. FIG. 30 is a top view showing the second confirmatory test. FIG. 31 is a view of the second confirmation test viewed from the exhaust port side of the exhaust nozzles 100 and 200. FIG.

FIG. 32 is a perspective view showing a second confirmatory test. FIG. 32(a) shows a case where the exhaust nozzle 100 according to this embodiment is used and the shield 13 is not used (comparative example). FIG. 32(b) shows a case where a circular outlet exhaust nozzle 200 according to a comparative example is used and a shield 13 is used (comparative example). FIG. 32(c) shows a case where the exhaust nozzle 100 according to this embodiment and the shield 13 are used together (this embodiment).

As shown in FIGS. 27 and 28, in the second confirmation test, an exhaust nozzle 200 (model ), or a petal-shaped exhaust nozzle 100 (model) according to the present embodiment.

In the second confirmation test, four types of exhaust nozzles #1, #4, #5, and #7 were used as the petal-shaped exhaust nozzles 100 (see FIG. 17). Note that three types of exhaust nozzles #1, #4, and #7 were used in the above-described first verification test, and therefore, the exhaust nozzle #5 was added in the second verification test. .

In addition, the shield 13 (model) was used in the second confirmation test. The shield 13 is a plate-like member and is arranged parallel to the central axis direction of the engine nacelle 1 and the exhaust nozzles 100 and 200 .

As shown in FIG. 29, the shield 13 is arranged at a distance of 2D from the central axes of the engine nacelle 1 and the exhaust nozzles 100 and 200 (see dashed line). Note that the value of D means the diameter of the exhaust port of the exhaust nozzles 100 and 200 . In our example, the value of D was 28.8 mm.

Further, as shown in FIG. 30, the width of the shield 13 is 3D, and the center position of the width direction of the shield 13 is arranged so as to coincide with the positions of the central axes of the engine nacelle 1 and the exhaust nozzles 100 and 200. was done. Further, as shown in FIG. 30, the length of the shield 13 protruding rearward from the exhaust ports of the exhaust nozzles 100 and 200 is 3D.

The microphone was placed on the back side of the shield 13 (see FIG. 31), and the noise reduction amount (dB) was measured in the polar angle range of 90° to 160° (see FIG. 29). The Mach number Mj of the jet engine was set to 0.98.

Also, the noise recording was sampled at 204.8 kHz. In addition, the noise evaluation was performed in the range of 400 Hz (lower limit frequency of the anechoic chamber where confirmation test was performed) to 80 kHz (upper limit frequency of recording) at 1/3 octave band center frequency. Note that OASPL in FIGS. 33 to 36, which will be described later, is an integrated value in this frequency range, and the noise reduction amount ΔOASPL (dB) is each OASPL-OASPL (Baseline).

FIG. 33 shows the results of a second validation test for exhaust nozzle #4.

FIG. 33 shows (a) the case where the exhaust nozzle #4 is used and the shield 13 is not used (comparative example), and (b) the case where the shield 13 is used and an exhaust nozzle with a circular exit is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #4 and shield 13 are used together (this embodiment). A larger value on the negative side (that is, less than 0) indicates a larger amount of noise reduction. Conversely, the larger the value on the positive side (that is, the side greater than 0), the larger the amount of increase in noise.

In the polar angle range (whole range) of 90° or more and 160° or less, the jet noise reduction amount when (c) the exhaust nozzle #4 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle This is greater than the amount of reduction in jet noise when #4 is used and shield 13 is not used (comparative example) (c>a).

Furthermore, in the polar angle range of 90° or more and 140° or less, the amount of jet noise reduction when (c) the exhaust nozzle #4 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle #4 is greater than the sum of the jet noise reduction amount when the shield 13 is not used (comparative example) and the jet noise reduction amount when (b) only the shield 13 is used (comparative example) ( c>a+b). In other words, (c) the combined use of the exhaust nozzle #4 and the shield 13 (this embodiment) provides a simple expected effect (total value of a+b) in the polar angle range of 90° or more and 140° or less. higher effect can be obtained.

On the other hand, in the polar angle range of 150 to 160°, c>a+b does not hold. This is because the noise reduction effect of the single exhaust nozzle #4 is dominant. At this time, even if the shielding effect of the shield 13 is weak, a significant noise reduction effect is obtained by the effect of the exhaust nozzle #4 alone, and the degree thereof is sufficiently large.

FIG. 34 shows the results of a second confirmation test for exhaust nozzle #7.

FIG. 34 shows (a) the case where the exhaust nozzle #7 is used and the shield 13 is not used (comparative example), and (b) the case where the shield 13 is used and an exhaust nozzle with a circular exit is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #7 and shield 13 are used together (this embodiment).

In the polar angle range of 90° or more and 140° or less, the amount of jet noise reduction when (c) the exhaust nozzle #7 and the shield 13 are used together (this embodiment) is as follows: is greater than the jet noise reduction amount when the shield 13 is not used (comparative example) (c>a).

Further, in the polar angle range of 90° or more and 140° or less, the amount of jet noise reduction when (c) the exhaust nozzle #7 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle #7 is substantially equal to the total value of the jet noise reduction amount when the shield 13 is not used (comparative example) and the jet noise reduction amount when (b) only the shield 13 is used (comparative example). (c≈a+b). In other words, (c) when the exhaust nozzle #7 and the shield 13 are used together (this embodiment), the expected effect (the total value of a + b) is equivalent to effect can be obtained.

On the other hand, in the polar angle range of 150° or more and 160° or less, c becomes smaller than a+b. This is because the noise reduction effect of the single exhaust nozzle #7 is dominant. At this time, even if the shielding effect of the shield 13 is weak, a significant noise reduction effect is obtained by the effect of the exhaust nozzle #7 alone, but the degree is smaller than that of the exhaust nozzle #4.

FIG. 35 shows the results of a second confirmation test for exhaust nozzle #1.

FIG. 35 shows (a) the case where the exhaust nozzle #1 is used and the shield 13 is not used (comparative example), and (b) the case where the shield 13 is used and an exhaust nozzle with a circular exit is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #1 and shield 13 are used together (this embodiment).

In the polar angle range (whole range) of 90° or more and 160° or less, the jet noise reduction amount when (c) the exhaust nozzle #1 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle This is greater than the amount of reduction in jet noise when #1 is used and shield 13 is not used (comparative example) (c>a).

In addition, in the polar angle range (whole range) of 90° or more and 160° or less, the amount of jet noise reduction when (c) the exhaust nozzle #1 and the shield 13 are used together (this embodiment) is as follows: The sum of the amount of jet noise reduction when exhaust nozzle #1 is used without shield 13 (comparative example) and the amount of jet noise reduction when only shield 13 is used (comparative example). greater than (c>a+b). In other words, (c) the combined use of the exhaust nozzle #1 and the shield 13 (this embodiment) provides a simple expected effect (total value of a+b) in the polar angle range of 90° or more and 160° or less. higher effect can be obtained.

However, in FIG. 35, the noise reduction effect of the single exhaust nozzle #1 is too close to the direction of the polar angle of 160°. Even if the reduction effect is included, the noise increases (positive side).

FIG. 36 shows the results of a second validation test for exhaust nozzle #5.

FIG. 36 shows (a) when exhaust nozzle #5 is used and shield 13 is not used (comparative example), (b) when shield 13 is used and a circular exit exhaust nozzle is used (comparative example). , (c) shows the noise reduction amount ΔOASPL (dB) in the polar angle range of 90° to 160° when the exhaust nozzle #5 and shield 13 are used together (this embodiment). A larger value on the negative side (that is, less than 0) indicates a larger amount of noise reduction. Conversely, the larger the value on the positive side (that is, the side greater than 0), the larger the amount of increase in noise.

In the polar angle range (whole range) of 90° or more and 160° or less, the amount of jet noise reduction when (c) the exhaust nozzle #5 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle This is greater than the amount of jet noise reduction when #5 is used and the shield 13 is not used (comparative example) (c>a).

Furthermore, in the polar angle range of 90° or more and 130° or less, the amount of reduction in jet noise when (c) the exhaust nozzle #5 and the shield 13 are used together (this embodiment) is as follows: (a) the exhaust nozzle #5 is greater than the sum of the jet noise reduction amount when the shield 13 is not used (comparative example) and the jet noise reduction amount when (b) only the shield 13 is used (comparative example) ( c>a+b). In other words, (c) the combined use of the exhaust nozzle #5 and the shield 13 (this embodiment) provides a simply expected effect (total value of a+b) in the polar angle range of 90° or more and 130° or less. higher effect can be obtained.

On the other hand, in the polar angle range of 140° or more and 160° or less, c>a+b does not hold. , the noise reduction effect of the single exhaust nozzle #5 is dominant. At this time, even if the shielding effect of the shield 13 is weak, a significant noise reduction effect is obtained by the effect of the exhaust nozzle #5 alone, and the degree thereof is smaller than that of the exhaust nozzle #4 and larger than that of the exhaust nozzle #7.

When exhaust nozzle #5 and shield 13 are used together, intermediate features between exhaust nozzle #4 and shield 13 and exhaust nozzle #7 and shield 13 are shown.

In other words, the range of polar angles in which a higher effect (c>a+b) than is simply expected by the combined use of the exhaust nozzle and the shield 13 is exhaust nozzle #4, exhaust nozzle #5, and exhaust nozzle #7. It is expected that the noise reduction effect can be controlled by devising the nozzle shape. This suggests that it is possible to design a nozzle shape that enhances the airport noise reduction effect in accordance with the shield 13 installed for the purpose of reducing sonic booms.

8. Conclusion

As described above, according to the supersonic aircraft and the method for reducing sonic boom and jet noise according to the present embodiment, the shield 13 is housed in the engine nacelle attached to the fuselage of the fuselage of the supersonic aircraft. A sonic boom caused by the engine exhaust flow is reduced by shielding the engine exhaust flow ejected from the jet engine. The exhaust nozzle 100 provided at the exhaust port of the engine nacelle generates a high-frequency component jet noise at a position where the shield 13 can block the high-frequency component of the engine exhaust flow. and reduce low frequency jet noise by promoting mixing of the low frequency components of the engine exhaust flow with the ambient air flow.

Thus, according to this embodiment, the separate tasks of reducing sonic booms during supersonic cruise and airport noise reduction during takeoff are addressed by shielding 13 designed for low sonic booms and petal-shaped exhaust nozzles. By using 100 together, it is possible to obtain a high airport noise reduction effect that cannot be obtained by a simple combination of the shield 13 and the circular nozzle, and to reduce the sonic boom, which is a major issue in the environmental compatibility of supersonic aircraft. Both airport noise reduction can be solved.

International standards are being established and the market for supersonic aircraft is being developed, and noise reduction technology in this field is expected to be used in the manufacture of new aircraft in the future.

Although the embodiments and modifications of the present technology have been described above, the present technology is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present technology. Of course.

REFERENCE SIGNS LIST 10 Airframe 100 Exhaust Nozzle 101 Exhaust Channel 102 Projection 13 Shield 15 Engine Exhaust Stream

Claims (20)

a shield that reduces a sonic boom caused by an engine exhaust flow ejected from a jet engine housed in an engine nacelle attached to the fuselage of an aircraft by shielding the engine exhaust flow;
Reduce jet noise of high-frequency components by generating a sound source of high-frequency components at a position that is provided at the exhaust port of the engine nacelle and that allows the shield to block high-frequency components of the engine exhaust flow. and an exhaust nozzle for reducing jet noise of low frequency components by promoting mixing of the low frequency components of the engine exhaust flow with the outside air flow;
A supersonic aircraft comprising a A supersonic aircraft according to claim 1,
The exhaust nozzle is positioned to allow the shield to shield high frequency components of the engine exhaust flow by promoting mixing of the engine exhaust flow and ambient air flow near the exhaust port. A supersonic aircraft that produces a sound source of A supersonic aircraft according to claim 1 or 2,
In the polar angle range where the nose of the airframe is 0°, the exhaust port of the exhaust nozzle is 90°, and the aft of the airframe is 180°,
In the polar angle range of 110° or more and 140° or less, the amount of jet noise reduction when using the exhaust nozzle and the shield is the reduction in jet noise when the exhaust nozzle is used and the shield is not used. A supersonic aircraft greater than the amount. A supersonic aircraft according to any one of claims 1 to 3,
In the polar angle range where the nose of the airframe is 0°, the exhaust port of the exhaust nozzle is 90°, and the aft of the airframe is 180°,
At a polar angle of 140°, the amount of jet noise reduction with the exhaust nozzle and the shield is the same as the amount of jet noise reduction with the exhaust nozzle without the shield, and the amount of jet noise reduction with the exhaust nozzle: a supersonic aircraft that is greater than the sum of the amount of reduction in jet noise when using the shield without using the supersonic aircraft. A supersonic aircraft according to any one of claims 1 to 4,
The supersonic aircraft, wherein the exhaust nozzle has a plurality of protrusions provided on an inner circumference. A supersonic aircraft according to claim 5,
The plurality of protrusions have the same shape and the same size, and are provided at regular intervals in the circumferential direction of the exhaust nozzle. A supersonic aircraft according to claim 5 or 6,
A supersonic aircraft, wherein the number N of the plurality of protrusions is N>4. A supersonic aircraft according to any one of claims 5 to 7,
each of the plurality of projections includes two sides projecting in an inner peripheral direction of the exhaust nozzle when the exhaust nozzle is viewed in the axial direction, and the lengths of the two sides are the same;
When the number of the plurality of protrusions is N and the length of one side of the regular N-sided polygon is 1,
A supersonic aircraft, wherein a length Rf of one side of the protrusion is Rf>0.5. A supersonic aircraft according to claim 8,
A supersonic aircraft in which the area of the exhaust port of the exhaust nozzle is the same regardless of the number N of the plurality of protrusions and the length Rf of one side of the protrusions. A supersonic aircraft according to any one of claims 5 to 9,
a sound pressure level of high frequency components of jet noise from the exhaust nozzle having the plurality of protrusions is higher than a sound pressure level of high frequency components of jet noise from the exhaust nozzle having no protrusions;
A supersonic aircraft, wherein a sound pressure level of low frequency components of jet noise from the exhaust nozzle with the plurality of protrusions is lower than a sound pressure level of low frequency components of jet noise from the exhaust nozzle without the plurality of protrusions. A supersonic aircraft according to any one of claims 1 to 10,
The supersonic aircraft, wherein the shield reduces a sonic boom caused by the engine exhaust flow by suppressing the engine exhaust flow from going around the fuselage downward. A supersonic aircraft according to any one of claims 1 to 11,
The supersonic aircraft, wherein the shields include a pair of shields arranged on the fuselage so as to sandwich the engine exhaust flow. A supersonic aircraft according to claim 12,
Having a horizontal stabilizer arranged behind the engine nacelle,
A supersonic aircraft, wherein the pair of shields are arranged on the horizontal stabilizer. A supersonic aircraft according to claim 13,
The supersonic aircraft, wherein the shield further includes the horizontal stabilizer. A supersonic aircraft according to any one of claims 12-14,
Each said pair of shields slopes outwardly of said fuselage. A supersonic aircraft according to claim 12,
Having a rear trunk lift surface provided behind the engine nacelle,
A supersonic aircraft, wherein the pair of shields are arranged on the rear fuselage lift surface and function as a V-tail. A supersonic aircraft according to any one of claims 1 to 16,
The exhaust nozzle extends to the rear of the engine and constitutes an exhaust flow path,
The exhaust nozzle has a plurality of main nozzle pieces and one or more connecting nozzle pieces,
The main nozzle piece is provided so that the rear end side thereof can swing inward and outward directions of the exhaust flow path about an opening and closing bent portion formed at the rear end of the narrowed portion at the rear of the engine,
The connecting nozzle piece is arranged between the adjacent main nozzle pieces and is connected to the main nozzle pieces on both sides so as to be bendable, and the connecting nozzle piece bends with the main nozzle piece at the side bent portion. a central bent portion that is removably connected and capable of forming the plurality of protrusions inside the exhaust flow path in conjunction with movement of each of the main nozzle pieces;
When the main nozzle piece swings outward from the exhaust flow path, the connecting nozzle piece forms a flat surface without a protrusion in the exhaust flow path, and the cross-sectional area of the exhaust flow path is the open/close type. widening from the position of the bent portion toward the rear end side of the exhaust flow path,
In order to narrow the exhaust flow path, when the main nozzle piece swings inward of the exhaust flow path, the connecting nozzle piece forms a projecting portion along the exhaust flow path in the exhaust flow path. Form supersonic aircraft. A supersonic aircraft according to claim 17,
A supersonic aircraft, wherein the plurality of main nozzle pieces and connecting nozzle pieces form an entire circumference of an exhaust passage behind the engine. A supersonic aircraft according to claim 17 or 18,
When the supersonic aircraft is cruising at supersonic speed, the main nozzle piece swings outward from the exhaust passage,
A supersonic aircraft in which the main nozzle piece swings inwardly of the exhaust flow path during takeoff and landing of the supersonic aircraft. The shield reduces a sonic boom caused by the engine exhaust flow by shielding the engine exhaust flow ejected from a jet engine housed in an engine nacelle attached to the fuselage of the fuselage of the supersonic aircraft,
The exhaust nozzle provided at the exhaust port of the engine nacelle generates a sound source of the high frequency component at a position where the shield can shield the high frequency component of the engine exhaust flow, thereby suppressing the high frequency component. A sonic boom and a method for reducing jet noise, wherein jet noise is reduced and low frequency components of the jet noise are reduced by promoting mixing of the low frequency components of said engine exhaust flow with an outside air flow.

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