JP2012154176A - Aerodynamic noise reducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aerodynamic noise reducing device suitably reducing high frequency noise to be generated during jet ejection and suitably suppressing a thrust loss of a jet engine.SOLUTION: A plurality of sharp mixer members each having a V-shaped cross section that is orthogonal to a longitudinal center axis, the cross section being continuously reduced along the longitudinal center axis, are disposed along a nozzle outlet end, in such a manner that the sectional V-shape intrudes into a jet flow toward a center of the jet flow, at an intrusion angle δ in a position separated from a confluent position of the jet flow and an ambient air flow to a downstream side by a distance d.

Description

  The present invention adds an aerodynamic noise reduction device for aircraft and high-speed vehicles, particularly a simple structure member, and suppresses the disadvantages of increased thrust loss and high-frequency noise generation while appropriately mixing the jet and ambient air. The present invention relates to an aerodynamic noise reduction device that controls to reduce mixed noise.

Where fluids with different speeds merge, vortices are generated by fluid shear. Although the initial vortex is small, the scale of the vortex can be increased while moving downstream with the fluid flow. Since vortices affect sound propagation in the far field, mechanical devices with flow generate noise. Hereinafter, the exhaust noise of a jet engine for a passenger aircraft will be described as an example.
In a passenger jet engine, a high-speed jet discharged from a core nozzle generates a large-scale structural vortex downstream of the nozzle as a result of a large shear between the surrounding fan flow or the surrounding air, and becomes a jet noise source. In addition, there is a box for storing landing gears at the lower part of the aircraft. When the box is opened, the surface of the fuselage is uneven, and vortex shedding occurs based on the speed difference between the aircraft surface and the box. Since the vortex interferes with the downstream end of the box and generates a sound wave and returns to the vortex shedding at the upstream end, it becomes a noise generation source in the far field.
Conventionally, several countermeasures have been taken against noise caused by such air movement. For example, for a jet engine, there is a device called a so-called lobe mixer (see, for example, Patent Document 1 and FIG. 16 of the present application). This device prevents the generation of large jet noise by preventing the generation of large-scale structural vortices by promoting flow mixing. Specifically, the nozzle end is deformed inward, and external air is introduced inward to reduce the average speed of the high-speed flow. Since it is theoretically known that the total acoustic power of mixed noise is expressed by a similarity law, it is proportional to the eighth power of the average velocity of the exhaust flow. Therefore, the decrease in the average velocity by the lobe mixer directly leads to the reduction of the jet noise. .
However, it is known that a mixing-enhancement device having a large deformation amount, such as a lobe mixer, causes several secondary problems. One is the thrust loss of the engine while cruising. The decrease in average speed leads to thrust loss as derived from momentum conservation. Not only the thrust loss at the time of takeoff rise, but also the thrust loss of the engine during cruising will increase the operating cost.
Another problem is an increase in high frequency noise. Forcing the lobe mixer to promote mixing by its shape means that, from another point of view, it increases shear and creates a high frequency sound source. The high frequency sound source immediately after the nozzle contributes to the nozzle side surface direction.
17 and 18 illustrate the noise reduction effect of the lobe mixer by the model test. 17 and 18 show that the nozzle diameter is 22 mm and the Mach number of the air to be ejected (the fluid ejection speed divided by the sound speed) is 0.9 and 30 degrees and 60 degrees from the exhaust axis direction. The result of noise reduction of the lobe mixer at is shown. For comparison, the noise reduction effect of a nozzle having a circular nozzle cross section (conical) is also shown. In the figure, the horizontal axis represents frequency, and the vertical axis represents sound pressure level (SPL: Sound Pressure Level, unit is dB).
As is apparent from the figure, in the direction 30 ° from the exhaust shaft direction, wideband noise is reduced by the lobe mixer, but the noise level in the high frequency band is increased. In particular, in the direction of 60 ° from the exhaust axis direction approaching the side surface direction, the noise increase in the high frequency range is significant.
By the way, in order to solve the problem of thrust loss of the aircraft engine, a technique for suppressing the amount of flow blocking at the nozzle end called a tab (see, for example, Patent Document 2) and a triangular notch called serration are inserted. A technique (see, for example, Patent Document 3) has been proposed. In the former, as represented by a tab, a protrusion having a flow shielding rate (ratio of the shielding area of the tab to the nozzle cross-sectional area) of about several percent is provided at the nozzle end. Downstream of the protrusions, mixing is promoted compared to the case without protrusions, but the thrust loss is not as high as that of the lobe mixer. Examples of the cross-sectional area of the protrusion include a rectangle and a triangle. The latter, for example, commonly known as Chevron, has a notch in the valley, but has an end shape that is slightly inclined to the mainstream, and a vertical vortex on the line connecting the mountain and the valley. To control the development of the shear layer.
For the tab, the two-dimensional projected area is limited to save the shielding rate that affects the thrust performance. As a result, mixing acceleration cannot be expected as much as a lobe mixer. One reason why the mixing promotion effect is insufficient is that the removal effect by the tab is limited to the nozzle end. On the other hand, the chevron can cause vortex excitation along the side from the valley to the peak. However, the demerit of generating high-frequency noise according to the amount of intrusion in the mountain is great, and there remains room for adjustment including thrust loss. A mechanism to adjust the amount of chevron penetration to reduce thrust loss during cruising is also being studied, but there are challenges to overcome such as additional dimensions, increased gravity, required power, and failure risk. In addition to the problem of machining accuracy due to the complex shape of the chevron, there are also problems such as the throat position by cutting and the stabilization of thrust performance.

JP 2002-317698 A JP 2000-145475 A JP 2003-90300 A

As described above, the lobe mixer is excellent in terms of the effect of promoting the mixing of the high-speed jet flow and the ambient air flow, but has the problem of causing high-frequency noise while causing thrust loss of the engine.
The tab does not cause thrust loss as much as the lobe mixer, but the effect of promoting the mixing of the high speed jet flow and the ambient air flow is insufficient, and the noise reduction effect of the high speed jet including the high frequency range is relatively small. Has a problem.
Therefore, the present invention has been made in view of the problems of the prior art. The purpose of the jet noise is to add thrust loss and high frequency noise by adding a simple structure member. It is to provide an aerodynamic noise reduction device that reduces mixing noise by appropriately controlling mixing of a jet and ambient air while suppressing noise.
Another object of the present invention is to provide an aerodynamic noise reduction apparatus that promotes boundary layer separation control and mixing of different fluids by adding a simple structure member to aerodynamic noise such as leg noise.

In order to achieve the above object, the aerodynamic noise reduction device according to claim 1, wherein a secondary flow having different flow characteristics is mixed with a main flow to reduce aerodynamic noise caused by shearing of the main flow and the sub flow. A device,
The aerodynamic noise reduction device includes a plurality of sharp mixer members whose cross-sectional shape perpendicular to the longitudinal central axis is a projecting shape and whose cross-sectional shape continuously decreases along the longitudinal central axis. In the downstream position including the merging position, the protruding shape enters the main flow obliquely in a form toward the center side of the main flow, and the surface layer of the main flow is partially divided.
As described above, lobe mixers, tubs, etc. are mechanisms that prevent the generation of large-scale structural vortices by forcibly promoting the mixing of the jet flow and the ambient air flow. The side effect of the increase is the problem.
Although the details will be described later, the inventor of the present application has made a detailed analysis of the exhaust pressure field (total pressure) behind the nozzle when each nozzle ejects a jet flow in a nozzle with a lobe mixer and a circular nozzle without it. As a result, in a nozzle equipped with a lobe mixer, the flow in the main flow (jet flow) surface layer is divided into several small flows (corresponding to the number of lobes) completely separated from the main flow, and the flow field of the main flow is By reducing the scale, we found that the mainstream exhaust pressure (total pressure) decreased, which caused engine thrust loss, and that a small flow split from the mainstream was the source of high-frequency noise. .
From this analysis result, the inventor of the present application has made the mixer member that promotes the mixing of the main flow and the ambient air flow into a shape that partially cuts the main flow surface layer (forms a cut in the main flow surface layer), thereby removing the main flow from the main flow. The small flow is no longer divided, thereby suppressing the thrust loss of the engine and at the same time suppressing the generation of high-frequency noise, leading to the invention. In addition, the inventor of the present application confirmed that the above-described shape of the mixer member is effective for suppressing the thrust loss of the engine and the generation of high-frequency noise, as will be described later, through a demonstration test using a model. In addition, the side flow here means a flow field adjacent to the main flow and having different flow characteristics. For example, when the main flow is a jet flow or a fan flow, the side flow is a fan flow or ambient air, respectively. Means.

The aerodynamic noise reduction device according to claim 2, wherein the sharp mixer member has a representative dimension that is 1/10 or less of a representative dimension of a cross section of the member on a surface that partially divides the mainstream surface layer. A plurality of grooves, depressions or protrusions were provided.
In the aerodynamic noise reduction device, by providing the groove or the like on the surface of the sharp mixer member that contacts the main flow (on the surface toward the main flow center), a protrusion shape including the groove or the like in the shear layer of the main flow and the surrounding air flow Preferably divides the mainstream surface layer, thereby promoting the mixing of the mainstream with the ambient airflow.

The aerodynamic noise reduction device according to claim 3, wherein the sharp mixer member has a shape in which an angle formed between a longitudinal central axis of the member and a central direction of the main flow decreases or increases along the downstream of the main flow. It was.
In the above-described aerodynamic noise reduction apparatus, by setting the longitudinal central axis of the sharp mixer member to the above-described configuration, the sharp mixer member that has entered the main flow does not become resistant to the main flow, and promotes mixing of the main flow and the ambient air flow. Act on.

5. The aerodynamic noise reduction device according to claim 4, wherein a plurality of the sharp mixer members are disposed at a merging position of the main flow and the substream, and any one of the disposed position and an intrusion angle and / or an intrusion amount with respect to the main flow. This is variable.
In the aerodynamic noise reduction device, the main flow and the ambient air flow are not affected by the main flow with various flow characteristics by making the number of mixer members, the position of the mixer, the penetration angle or the penetration amount relative to the main flow variable. In the fault, the shape of the member projections suitably divides the mainstream surface layer, thereby promoting the mixing of the mainstream and the surrounding airflow, which, in the case of an engine, favorably reduces thrust loss, and also reduces high-frequency noise. Generation | occurrence | production can be suppressed suitably. In addition, this means that the mixing form of the mixer member with respect to the main flow (number of members, arrangement position, intrusion angle or intrusion amount with respect to the main flow) is a control amount (operation amount or adjustment amount), and engine thrust loss and noise acoustics This suggests that the characteristics can be actively controlled.

6. The aerodynamic noise reduction device according to claim 5, wherein the sharp mixer member is provided with a closed flow path or an open flow path on a surface opposite to the center of the main flow, and an air supply is provided upstream of the flow path. It communicated with the means or the substream, and the downstream communicated with the mainstream.
In the aerodynamic noise reduction device, the main flow and the ambient air are formed in the shear layer of the main flow and the ambient air flow by providing a closed flow path or an open flow path in the mixer member or on the surface opposite to the center of the main flow. The mixing state (mixing degree) with the flow can be changed.

In the aerodynamic noise reduction device according to claim 6, the sharp mixer member includes a communication hole for communicating the flow path and the main flow in addition to the tip of the member.
In the aerodynamic noise reduction device, by providing a communication hole that communicates the flow path and the main flow in addition to the tip of the mixer member, the degree of mixing of the main flow and the surrounding air flow is wider in the shear layer of the main flow and the surrounding air flow. It becomes possible to suitably change over the range.

In the aerodynamic noise reduction device according to claim 7, a secondary fluid having physical properties different from those of the main flow and the secondary flow is caused to flow through the flow path.
In the aerodynamic noise reduction device, the secondary fluid is mixed into the shear layer of the main flow and the ambient air flow by flowing secondary fluids (for example, water, water vapor, etc.) having different physical properties through the internal flow path of the mixer member. As a result, the mixing degree of the main flow and the ambient air flow can be suitably changed over a wider range.

In the aerodynamic noise reduction device according to the eighth aspect, a pressure or flow rate adjusting mechanism for changing the pressure or flow rate of the secondary fluid is provided.
In the aerodynamic noise reduction device, a pressure or flow rate adjusting mechanism that changes the pressure or flow rate of the secondary fluid, for example, regularly or periodically (for example, a pressure comprising a pressure regulating valve or a flow rate regulating valve, a controller of the valve, and a pressure or flow rate sensor) In addition, the degree of mixing of the main flow and the ambient air flow can be suitably changed by providing the flow rate adjusting mechanism or the like. This also suggests that the degree of mixing of the main flow and the ambient air flow can be actively controlled by using the flow rate of the secondary fluid as a control amount (operation amount or adjustment amount). Is a control amount (operation amount or adjustment amount), suggesting that the thrust loss of the engine can be suppressed and the acoustic characteristics of noise can be actively controlled.

The aerodynamic noise reduction device according to claim 9 is provided with a storage mechanism that stores the sharp mixer member.
In the aerodynamic noise reduction device, by providing a storage mechanism for storing the mixer member, the mixer member does not become an air resistance during cruise, for example.

In the aerodynamic noise reduction device according to claim 10, the sharp mixer member is applied to any one of a core nozzle, a fan duct, and a pylon of an aero engine.
In the aerodynamic noise reduction device, by providing the mixer member in the above-described form with respect to the portion of the aircraft engine, for example, in the shear layer of the jet flow (as the main flow) and the fan flow (as the sub flow) Generation of high-frequency noise due to shear between jet and fan flow, while the shape suitably divides the surface layer of jet flow, promotes mixing of jet flow and fan flow, and favorably suppresses engine thrust loss Can be suitably suppressed.

The aerodynamic noise reduction device according to claim 11, wherein the sharp mixer member is formed on a wing leading edge, a wing trailing edge or a wing surface of an aircraft, a leg storage portion or a pedestal of a fuselage, or an uneven surface on a vehicle body surface of a vehicle. It was decided to apply to either.
In the aerodynamic noise reduction device, for example, a blade surface flow (as a mainstream) and a blade (as a substream) are provided by providing the sharp mixer member in the above-described form for each part of an aircraft wing and fuselage or vehicle. In the shear layer of the crevice flow between the leading edge and the slat, the surface layer of the wing surface flow is suitably divided to promote mixing of the wing surface flow and the crevice flow, and to shear the blade surface flow and the crevice flow. It is possible to suitably suppress the occurrence of the high frequency noise caused.

According to the aerodynamic noise reduction device of the present invention, the mixer member divides a plurality of small flow fields from the main flow as in the prior art such as a lobe mixer, and mixes the plurality of small flow fields with the surrounding side flow. Rather than reducing the noise level associated with the shear between the main flow and the side flow, the mixer member divides the main flow surface into a V shape in the shear layer between the main flow and the surrounding side flow (cutting into the main flow surface layer). The feature is that the mixing of the main flow and the surrounding substream is promoted based on the divided part, and the noise level related to the shearing of the main flow and the subflow is reduced. That is, in the prior art, the size of the main flow field is reduced because the mixer member divides a plurality of small flow fields from the main flow, and when the main flow is a jet flow, the thrust loss of the engine is caused and the flow field is divided. As a result, high frequency noise is increased. On the other hand, in the present invention, the mixer member only divides the mainstream surface layer into a V shape, and the scale of the mainstream flow field is hardly reduced. As a result, the thrust loss of the engine is much smaller than that of the prior art. At the same time, high-frequency noise can be significantly suppressed as compared with the prior art.
Further, the mixer member according to the present invention is a simple mechanism in which the cross-sectional shape perpendicular to the longitudinal central axis is a projecting shape and the cross-sectional shape continuously decreases along the longitudinal central axis. Therefore, in the shear layers of various mainstreams and sidestreams of aircraft and high-speed vehicles, the mixing of the mainstream and sidestreams is promoted by allowing the mixer member to enter the mainstream from the sidestream side obliquely in a predetermined form. And it becomes possible to suppress suitably the noise resulting from the shear of a mainstream and a substream.
Furthermore, when the mixer member according to the present invention includes an internal flow path that communicates with the fluid supply source at the upstream and communicates with the main flow at the downstream, by changing the flow rate of the fluid flowing through the flow path, It becomes possible to control the degree of mixing. As a result, the aerodynamic noise reduction device of the present invention can change the acoustic characteristics (frequency characteristics, directivity) in the shear layer of the main flow and the subflow to desired characteristics.
In addition, the following effects can be expected for jet noise reduction as compared to the prior art.
(1) Compared to a structure in which a flow of several percent is shielded at the nozzle end such as a tab, the fluid mixing promoting effect and the noise reducing effect are large.
(2) Compared to a structure in which a nozzle such as a chevron is provided with a cut, the thrust loss of the engine is small and the increase in the weight of the engine is small.

It is explanatory drawing which shows the fluid mixing promotion apparatus of this invention. It is AA sectional drawing and BB sectional drawing of FIG. It is explanatory drawing which shows the modification of the cross-sectional shape of the fluid mixing member which concerns on this invention. It is explanatory drawing which shows the modification of the cross-sectional shape of the fluid mixing member which concerns on this invention. It is explanatory drawing which shows the modification of the cross-sectional shape of the fluid mixing member which concerns on this invention. It is explanatory drawing which shows the nozzle for a demonstration test produced for the demonstration test which confirms the noise reduction effect of this invention. It is explanatory drawing which shows the test equipment used for the verification test. It is each explanatory drawing which shows the noise reduction effect (noise frequency characteristic) of this invention in a 30 degree direction from a jet flow center. It is each explanatory drawing which shows the noise reduction effect (noise frequency characteristic) of this invention in a 60 degree direction from the jet flow center. It is explanatory drawing which shows the noise reduction effect (directivity characteristic of a noise) of this invention in a 20 degree-90 degree direction from a jet flow center. It is explanatory drawing which shows the measurement result of the exhaust pressure field of the jet flow ejected from each nozzle. It is explanatory drawing which shows the Example which applied the nail mixer which concerns on this invention to the fan nozzle and pylon of an aircraft. It is explanatory drawing which shows the Example which applied the nail mixer which concerns on this invention to the leg for aircrafts. It is explanatory drawing which shows the Example which applied the nail mixer which concerns on this invention to the leg storage part of the aircraft fuselage. It is explanatory drawing which shows the Example which applied the nail mixer which concerns on this invention to the wing leading edge and wing trailing edge of an aircraft. It is explanatory drawing which shows the lobe mixer of a prior art. It is each explanatory drawing which shows the noise reduction effect (noise frequency characteristic) of the prior art in a 30 degree direction from the jet flow center. It is each explanatory drawing which shows the noise reduction effect (noise frequency characteristic) of the prior art in a 60 degree direction from a jet flow center. It is explanatory drawing which shows the noise reduction effect (directivity characteristic of a noise) of the prior art in a 20 degree-90 degree direction from a jet flow center.

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings.

1-2 is explanatory drawing which shows the fluid mixing promotion apparatus 100 of this invention. 2A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line BB in FIG.
This fluid mixing promoting device 100 promotes mixing of a main flow (jet flow) and a substream (ambient air flow) having different flow field characteristics such as speed, temperature, pressure, direction, etc., so that a high-speed and high-temperature jet flow is achieved. Is an aerodynamic noise reduction device that reduces aerodynamic noise caused by shearing between a low-speed and low-temperature ambient air stream. In the configuration, a plurality of fluid mixing members 10 (sharp mixer members) according to the present invention are provided in a predetermined intrusion form along a core nozzle opening that ejects a high-speed and high-temperature jet flow.

  The fluid mixing member 10 enters obliquely at an entry angle δ and an entry amount L with respect to the jet stream at a point separated by a fixed distance d from the junction point of the jet stream and the ambient air stream downstream. In addition, the fluid mixing member 10 is disposed by a known expansion / contraction mechanism, rotation mechanism, link mechanism, hydraulic mechanism, and the like (not shown), an intrusion position (distance d), an intrusion angle δ, and / or an intrusion amount L. However, according to each flow characteristic of the main flow and the substream, it is comprised so that it can change suitably.

  The fluid mixing member 10 is a so-called mixer member that mixes a high-speed and high-temperature jet flow and a low-speed and low-temperature ambient air flow. However, the flow of the jet flow like a conventional lobe mixer is completely separated from the core main flow and the core main flow. It is not a mixer member that divides into several small flows, but a mixer member that partially divides only the surface layer of the jet stream (forms a cut in the surface layer of the jet stream). Details thereof will be described later with reference to FIG. Therefore, the fluid mixing promoting device 100 including the fluid mixing member 10 has a great advantage that it does not cause the thrust loss of an engine such as a lobe mixer and the generation of high frequency noise.

As shown in FIG. 2, the fluid mixing member 10 has the following characteristics in a cross-sectional shape perpendicular to the member central axis in order to partially divide only the surface layer of the jet flow.
B) The cross-sectional shape on the side facing the main flow (side facing the jet flow center) forms a protruding shape, and the surface layer portion of the jet flow into which it is inserted is divided into two or more,
B) The cross-sectional area gradually decreases (decreases) toward the tip of the member, that is, downstream of the jet flow.
In the embodiment of FIG. 2, the cross-sectional shape of the side facing the jet flow center and the side facing the jet flow center are both V-shaped, and the outer peripheral surface on the side not facing the jet flow center is an open flow path through which the ambient air flow flows. Is made. In addition, this open flow path may be complete | finished at the penetration | invasion point of jet flow. Further, the cross-sectional area of the portion that has entered the jet flow gradually decreases in a state where the opening angle φ is kept constant toward the member central axis or downstream of the jet flow. As shown in FIG. 2B, the fluid mixing member 10 finally completely enters the jet stream.

  Moreover, as shown in FIG. 3, the cross-sectional shape of the fluid mixing member 10 may be such that the opening angle φ decreases with the cross-sectional area toward the member central axis or downstream of the jet flow.

FIG. 4 is an explanatory view showing a modification of the cross-sectional shape of the fluid mixing member according to the present invention.
The cross-sectional shape of the fluid mixing member in FIG. 4A is such that the height h of the V-shaped member cross section is linear along the member central axis (longitudinal central axis) with the opening angle φ kept constant. To decrease. The penetration angle δ with respect to the jet flow takes a constant value. It corresponds to the fluid mixing member of FIG.

  In the cross-sectional shape of the fluid mixing member in FIG. 4B, since the opening angle φ decreases along the member central axis, the height h of the V-shaped member cross-section is nonlinear along the member central axis. To decrease. The penetration angle δ with respect to the jet flow takes a constant value. This corresponds to the fluid mixing member in FIG.

  The cross-sectional shape of the fluid mixing member in FIG. 4C is a so-called curved curve in which the member central axis is not a straight line, and the angle formed by the member central axis and the jet flow center decreases along the downstream of the jet flow. . Accordingly, in this case, the penetration angle δ2 with respect to the jet flow center at the end of the member is smaller than the penetration angle δ1 with respect to the jet flow center at the first penetration point with the jet flow of the member. Further, the opening angle φ can take a form that is constant along the member central axis or a form that decreases along the member central axis.

  The cross-sectional shape of the fluid mixing member in FIG. 4 (d) is opposite to that in FIG. 4 (c), and the member central axis is such that the angle formed by the member central axis and the jet flow center increases along the downstream of the jet flow. It is a curved curve. Accordingly, in this case, the penetration angle δ2 with respect to the jet flow center at the end of the member is larger than the penetration angle δ1 with respect to the jet flow center at the first penetration point with the jet flow of the member.

  In addition, as a cross-sectional shape of the fluid mixing member that partially divides only the surface layer of the jet flow, the cross-sectional shape shown in FIG. In particular, the fluid mixing member having a cross-sectional shape shown in FIG. 5 (c) has grooves (depressions and recesses) formed on the side facing the jet flow center in order to suitably divide the surface layer portion of the jet flow. The size of the groove is such that the representative dimension D ′ of the sectional shape C1-C2-C3 of the groove is 1/10 × D or less, where D is the representative dimension of the sectional shape C1-C2-C3-C4-C5. Set to. Here, the representative dimension is the diameter of the circle when each cross-sectional area is approximated by a corresponding circle. Other representative dimensions can be the height or width of the cross section.

  Further, in the fluid mixing member having a cross-sectional shape shown in FIG. 5 (d), a flow path through which air or other fluid (secondary fluid) flows is formed inside the member. This is to adjust the mixing degree of the jet flow and the ambient air flow by flowing the secondary fluid. In addition, when a communicating hole communicating with the jet flow is provided on the side surface other than the end of the member, the adjustment range of the mixing degree becomes wider. It can be seen that any cross-sectional shape is a shape (V, Y, U, T) protruding from the mainstream jet flow.

  The fluid mixing member 10 according to the present invention is supported by a known fixing device (not shown) outside the core nozzle and upstream of the jet flow. Further, when it is not necessary to actively mix the jet flow and the ambient air flow during cruise flight, the fluid mixing member 10 is pulled from the jet flow by a known link mechanism and hydraulic mechanism (not shown). It can also be configured to be pulled out and stored in a storage chamber (not shown). In this case, the fluid mixing member 10 does not become the air resistance of the aircraft.

  FIG. 6 is an explanatory view showing a verification test nozzle manufactured for a verification test for confirming the noise reduction effect of the present invention. In the fluid mixing member 10 according to the present invention, the cross-sectional area reaching the tip of the fluid mixing member 10 is gradually reduced, and the cross-sectional shape on the side in contact with the main flow is a shape that divides only the surface layer of the main flow. Or it has a dent. Therefore, since it is possible to recall a long nail having a small curvature, the fluid mixing member according to the present invention will be referred to as a nail-shaped mixer for convenience.

  As shown in FIG. 6B, eight nail mixers 10 are provided at equal intervals along the outer periphery of the opening of a nozzle having a diameter of 40 mm. The cross-sectional shape of the nail mixer 10 was V-shaped in FIG. 5B, and the penetration angle δ with respect to the jet flow center was 35 °. Further, the penetration amount L with respect to the jet flow is set to 0.19 times and 0.40 times the nozzle diameter, and the nail mixers corresponding to the penetration amounts L are denoted as a nail mixer 11 and a nail mixer 12, respectively. .

FIG. 7 is an explanatory diagram showing test equipment used in the verification test.
The air ejected from the nozzle is supplied from an air compressor and ejected vertically upward via an air storage tank. The jet velocity was set to a high subsonic Mach number M = 0.9. The air is not heated, and the air ejected from the nozzle is a so-called cold jet.

  Noise measurement is performed on a circular arc with a radius of 1.5m from the nozzle center (37.5 times the nozzle diameter of 40mm) and 90 ° from the nozzle exhaust axis (jet flow center) in the counterclockwise direction of 20 ° every 10 °. Using a 1/4 inch condenser microphone at 8 points to the direction. A 1/3 octave band analysis was performed on the time-series noise signals received by each microphone.

8 and 9 are explanatory diagrams showing the noise reduction effect (noise frequency characteristics) of the present invention in directions of 30 ° and 60 ° from the jet flow center.
As a comparative example, the noise frequency characteristics of a circular nozzle which is the base shape of the present invention are also shown.

As shown in FIG. 8, it can be seen that the nozzle provided with the nail mixer 11 appropriately suppresses the generation of broadband noise ranging from a low frequency to a high frequency in a 30 ° direction counterclockwise from the jet flow center. On the other hand, although the nozzle provided with the nail mixer 12 suppresses generation | occurrence | production of low frequency noise suitably compared with the nozzle provided with the nail mixer 11, it turns out that generation | occurrence | production of high frequency noise is not suppressed so much.
However, from another viewpoint, when the penetration angle δ = 35 ° with respect to the center of the jet flow of the nail mixer is set, the penetration amount with respect to the jet flow is set to L = 0.40 × D. The fluid mixing promoting device 100 of the present invention is adapted to suitably suppress the generation of noise by specializing in the low frequency range, while the intrusion amount with respect to the jet flow is set to L = 0.19 × D. This fluid mixing promoting device 100 suitably suppresses the generation of broadband noise from low to high frequencies. That is, it is shown that the acoustic characteristic (frequency characteristic) of noise caused by shearing between the jet flow and the ambient air flow can be controlled using the amount of penetration L with respect to the jet flow of the nail mixer as the control amount (operation amount or adjustment amount). .

  Similarly, as shown in FIG. 9, the nozzle provided with the nail mixer 11 similarly suppresses the generation of broadband noise ranging from a low frequency to a high frequency even in a 60 ° counterclockwise direction from the jet flow center. I understand that. On the other hand, although the nozzle provided with the nail mixer 12 suppresses generation | occurrence | production of low frequency noise suitably compared with the nozzle provided with the nail mixer 11, it turns out that generation | occurrence | production of high frequency number noise is not suppressed so much.

FIG. 10 is an explanatory diagram showing the noise reduction effect (noise directivity) of the present invention in the direction of 20 ° to 90 ° from the jet flow center.
This figure shows the overall sound pressure level obtained by integrating the sound pressure levels of all frequencies in each direction from 20 ° to 90 °.
It can be seen that each nozzle provided with the nail mixer 11 and the nail mixer 12 suitably reduces noise in each direction. In addition, the noise reduction effect of the nozzle provided with the nail mixer 11 and the nozzle provided with the nail mixer 12 is reversed at a boundary of about 50 °. That is, in the range of 20 ° to 50 °, the nozzle provided with the nail mixer 12 reduces noise more suitably than the nozzle provided with the nail mixer 11, but in the range of 50 ° to 90 °, the nozzle provided with the nail mixer 11 is provided. The nozzle reduces noise more suitably than the nozzle provided with the nail mixer 12. For reference, in the nozzle provided with the lobe mixer, the noise is remarkably reduced in the range of 20 ° to 40 °, but not so much in the range of 40 ° to 90 ° (see FIG. 19).

  From another point of view, the noise directivity characteristic due to the shear between the jet flow and the ambient air flow is defined as a control amount (operation amount or adjustment amount). It shows that it can be controlled.

  FIG. 11 is an explanatory diagram showing the measurement result of the exhaust pressure field of the jet flow ejected from each nozzle. In the measurement, a pressure measurement rake composed of a plurality of pressure holes was arranged downstream of the nozzle, and a time series pressure signal at each hole position was time-averaged to obtain the pressure distribution of the flow field downstream of the nozzle. The jet flow ejected from each nozzle is a high subsonic flow having a Mach number of 0.9, and the pressure distribution of the flow field downstream of each nozzle with respect to the circular nozzle (mixed state of jet flow and ambient air flow) Compared. The nail mixer 12 was used as the nail mixer according to the present invention.

  The figure is shown in matrix form. The measurement results of the exhaust pressure field of each nozzle having a circular nozzle with a representative diameter of 22 mm in the first row and a lobe mixer with a representative diameter of 22 mm in the second row are shown in the third row. The measurement result of the exhaust pressure field of each of the circular nozzle having a representative diameter of 40 mm and the nozzle provided with the nail mixer 12 having a representative diameter of 40 mm in the fourth row is shown. Each row in the figure shows each distance from each nozzle outlet end as non-dimensionalized by each representative diameter.

  From the measurement result of the exhaust pressure field, it can be seen that the nail mixer 12 according to the present invention does not completely divide the flow field of the core, unlike the conventional lobe mixer. For example, when compared at the point downstream of the nozzle x / D = 1.0, it is apparent that the lobe mixer tends to split the core flow into one in the center and eight in the surrounding by eight lobes. The surrounding eight streams develop outside the core flow and rapidly decay as a result of mixing with ambient air. That is, the momentum of the core flow is reduced, which leads to engine thrust loss. On the other hand, being completely divided into individual small flows means that there is a large shear, and it is estimated that the high frequency sound source shown in FIGS. 17 and 18 is generated.

On the other hand, the nail mixer 12 according to the present invention does not divide the flow only by cutting the core flow, but tends to cause deformation in the shear layer between the core flow and the ambient air, for example, x / D. = 1.0 is clear from the total pressure distribution downstream. The point where the notched portion stays within the range of the original core flow is also a point different from the lobe mixer.
As described above, the flow field provided by the nail mixer 12 according to the present invention has a crucial difference from the flow field provided by the lobe mixer in terms of shear caused by noise generation. It is presumed that this is also reflected in the difference in effect.

FIG. 12 is an explanatory view showing an embodiment in which the nail mixer 10 according to the present invention is applied to a fan nozzle and a pylon of an aircraft.
The nail mixer 10 of the present invention was applied to a fan nozzle that is a downstream end of a device called a nacelle that encloses an engine, and a pylon that connects the entire engine to a main wing or a fuselage.
The fan flow (main flow) is discharged from the fan nozzle at the downstream end via the fan duct and mixed with the air around the nacelle (secondary flow). Therefore, the nail mixer 10 of the present invention is protruded in the downstream direction while being inclined inward from the fan nozzle outlet end (in a form of entering the fan flow). As a result, the nail mixer 10 of the present invention divides the surface layer of the fan flow in a certain range downstream of the nozzle, takes in the low-speed ambient air, and suppresses both large local shears between the fan flow and the ambient air. Mixes the flow and suppresses the generation of high-frequency noise due to the shear between the fan flow and the ambient air flow. If the nail mixer 10 is cruised with the fan nozzle or the nacelle installed outside, the nail mixer 10 itself can become air resistance. Therefore, the engine has a storage mechanism for storing the nail mixer 10 in the nacelle during the cruise. Preferably it is.

  Further, by installing the nail mixer 10 of the present invention so as to incline and invade into the fan flow side on the wake side of the pylon, the low-speed pylon wake is taken in while dividing the surface layer of the fan flow. It is also possible to suppress the generation of high-frequency noise by mixing and promoting both flows while suppressing local shearing between the flow and the wake behind the pylon. The airframe is preferably provided with a storage mechanism such as folding the nail mixer 10 along the pylon or inserting it into the pylon when not in use.

FIG. 13 is an explanatory view showing an embodiment in which the nail mixer 10 according to the present invention is applied to an aircraft leg. FIG. 13 (a) is a front view, and FIG. 13 (b) is an AA sectional view.
When landing on an aircraft, the pedestal (cross-sectional shape is a cylinder, elliptical column, etc.) is deployed in the mainstream. A rod-like structure called a side brace that supports the legs is also placed in the mainstream. These structures become vortex generation sources from the side to the rear, and generate aerodynamic noise. Therefore, one or a plurality of nail mixers 10 according to the present invention are installed so that the front ends of the nail mixer 10 are inclined from the side surface to the rear edge of the pedestal, and the rear edge of the side brace is inclined to the mainstream side. . This separates the surface layer of the surrounding air flow (main flow) and mixes and promotes both flows while taking in low-speed vortex flow (side flow) and suppressing local shear between the surrounding air flow and vortex flow. Generation of frequency noise is suppressed.

FIG. 14 is an explanatory view showing an embodiment in which the nail mixer 10 according to the present invention is applied to a leg storage section of an aircraft fuselage.
As shown in FIG. 14B, in the state where the leg door is opened and the leg comes out, shear is generated in the front edge of the leg storage chamber, and the vortex can be excited. Therefore, as shown in FIGS. 14 (c) and 14 (d), the nail mixer 10 of the present invention is attached to the front edge of the leg storage chamber at one or a plurality of locations, and the tip thereof is inclined to enter the mainstream side. . This is expected to weaken the shear due to the speed difference from the mainstream. As a result, vortex excitation at the front edge of the leg storage chamber can be suppressed or delayed, and interference between the vortex and the rear edge of the leg storage chamber or other structures can be weakened to suppress noise generation. For storing the nail mixer 10 of the present invention, for example, it is preferable to provide a mechanism that expands in conjunction with opening and closing of the leg door and is stored inside the leg storage chamber during cruising.

Moreover, since the leg storage chamber in which the legs are deployed at the time of landing is placed in the mainstream, the rear edge becomes a vortex generating source. Therefore, if one or a plurality of nail mixers 10 of the present invention are attached to the rear edge of the leg storage chamber, it is expected to suppress or delay the generation of vortices.
The application to the leg storage part includes application to the uneven part of the trunk and the vehicle body. If the surface of the vehicle body of the high-speed vehicle is uneven, it becomes a source of aerodynamic noise as in the case of the leg storage unit. In order to suppress this, it is possible to suppress or delay the vortex shedding by installing the mixer of the present invention at the leading edge of the recess with the same idea as FIG.

FIG. 15 is an explanatory diagram showing an embodiment in which the nail mixer 10 according to the present invention is applied to a wing leading edge and a wing trailing edge of an aircraft.
At the time of landing invasion of an aircraft, a high lift generator called a slat operates at the leading edge of the wing, but as shown in FIG. 15 (a), the slat generates a gap flow between the main wing. This shear flow between the gap flow and the main flow can be a source of high-frequency noise. Accordingly, as shown in FIG. 15 (b), by arranging the nail mixer 10 of the present invention at the blade leading edge in a form that invades from the oblique direction with respect to the main flow, the mixing of the gap flow and the main flow is promoted, High frequency noise generated in the vicinity of the slat can be suitably suppressed.

  As for the blade trailing edge, when a high lift generating device called a flap is activated, a vortex is excited at the blade trailing edge. Accordingly, as shown in FIGS. 15B and 15C, the nail mixer 10 of the present invention is disposed in the vicinity of the trailing edge flap so as to incline obliquely with respect to the main flow, whereby the gap flow and the main flow are reduced. Mixing is promoted, and excitation of vortices generated in the vicinity of the trailing edge of the blade is suitably suppressed. As a result, high frequency noise can be suitably suppressed.

  Further, a conduit (flow path) is provided inside the nail mixer 10 of the present invention, a secondary fluid is supplied to the conduit from the outside, and is discharged into the main stream from the tip portion of the mixer or other portions other than the tip. Also good. As for the supply method, if the secondary fluid is air, the secondary fluid is supplied to the conduit from the engine (compressor) bleed air or the high-pressure reservoir through the pressure regulating valve. The pressure regulating valve is provided with a controller, and the controller takes in a detection signal from the pressure sensor and controls the pressure regulating valve so that the supply pressure becomes a target value. The target value of the supply pressure is, for example, the same as or equal to the mainstream potential energy based on the penetration angle δ, the penetration amount L, the mainstream velocity, the mainstream shear layer, or a combination thereof with respect to the mainstream of the nail mixer 10 of the present invention. Set the pressure above.

  On the other hand, when the secondary fluid is water, the supply method is such that the secondary fluid is supplied to the conduit from the storage tank via a flow rate adjusting valve by a pumping means such as an external power device such as a pump or potential energy such as high-pressure gas. Supply fluid. The flow rate adjusting valve includes a controller, and the controller takes in a detection signal from the flow rate sensor and controls the flow rate adjusting valve so that the flow rate becomes a target value. As a target value of the flow rate, for example, based on the penetration angle δ, the penetration amount L, the main flow velocity, the main flow shear layer, or a combination thereof with respect to the main flow of the nail mixer 10 of the present invention, it is 5% or less of the main flow mass flow rate. Set.

  In either case, the secondary fluid is allowed to flow through the internal flow path only when noise reduction is necessary (in the case of an aircraft, a fixed time for takeoff). Further, as the secondary fluid other than the above, for example, a gas, a mixed gas, a liquid, or a gas-liquid mixed fluid having physical properties different from those of the main flow and the side flow such as water vapor, carbon dioxide, nitrogen, and oil can be considered.

  The aerodynamic noise reduction device of the present invention is applied to an aircraft engine core nozzle, fan duct or pylon, or aircraft wing leading edge, wing trailing edge or wing surface, fuselage leg housing or pedestal, or high-speed vehicle body surface. It can be suitably applied to the uneven surface.

10 Fluid mixing member (nail mixer)
11 L = 7.6 mm Nail Mixer 12 L = 16 mm Nail Mixer 100 Fluid Mixing Promoter

Claims (11)

An aerodynamic noise reduction device that mixes substreams having different flow characteristics with a mainstream to reduce aerodynamic noise caused by shearing of the mainstream and the substream,
The aerodynamic noise reduction device includes a plurality of sharp mixer members whose cross-sectional shape perpendicular to the longitudinal central axis is a projecting shape and whose cross-sectional shape continuously decreases along the longitudinal central axis. An aerodynamic noise reduction device characterized in that, at a downstream position including a merging position, the protruding shape enters the main flow obliquely in a form toward the center of the main flow, and partially divides the surface layer of the main flow.   2. The sharp mixer member includes one or more grooves, depressions, or protrusions having a representative dimension of 1/10 or less of a representative dimension of a cross section of the member on a surface that partially divides the mainstream surface layer. The aerodynamic noise reduction device described in 1.   The aerodynamic noise reduction device according to claim 1 or 2, wherein the sharp mixer member has a shape in which an angle formed between a longitudinal central axis of the member and a central direction of the main flow decreases or increases along the downstream of the main flow.   4. The sharp mixer member is provided in plural at the merging position of the main flow and the substream, and any of the arrangement position and the invasion angle and / or the amount of invasion with respect to the main flow is variable. The aerodynamic noise reduction device according to crab.   The sharp mixer member has a closed flow path or an open flow path on the surface opposite to the center of the main flow inside, the upstream of the flow path communicates with the air supply means or the substream, and the downstream is the The aerodynamic noise reduction device according to any one of claims 1 to 4, which communicates with a mainstream.   6. The aerodynamic noise reduction device according to claim 1, wherein the sharp mixer member includes a communication hole that communicates the flow path and the main flow in addition to a tip of the member.   The aerodynamic noise reduction device according to claim 5 or 6, wherein a secondary fluid having physical properties different from those of the main flow and the sub-flow are supplied to the flow path.   The aerodynamic noise reduction device according to claim 7, further comprising a pressure or flow rate adjusting mechanism that changes a pressure or flow rate of the secondary fluid.   The aerodynamic noise reduction device according to claim 1, further comprising a storage mechanism that stores the sharp mixer member.   The aerodynamic noise reduction device according to claim 1, wherein the sharp mixer member is applied to any one of a core nozzle, a fan duct, and a pylon of an aircraft engine.   10. The sharp mixer member is applied to a wing leading edge, a wing trailing edge or a wing surface of an aircraft, or a leg storage portion or a pillar of a fuselage, or an uneven surface on a vehicle body surface of a vehicle. The aerodynamic noise reduction device according to crab.