JP2007285245A - Noise suppressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noise suppressor simplifying a mixing device while carrying a base principal of suppressing jet noise by accelerating mixing, facilitating attachment and detachment for improving serviceability, enabling to adjust characteristics according to aged deterioration of an engine, having capability to adapt itself if possible and having a little harmful influence of pressure loss and weight increase. <P>SOLUTION: An outer tube 2 is arranged to form an annular channel 2a in an outside of an inner tube 1 in which core flow jetting out of an exhaust nozzle of the engine flows. The outer tube 2 is arranged to position a downstream end part of the inner tube 1 in an upstream side of a downstream end part of the outer tube 2. A core nozzle the tip of which is formed in a projection shape and which includes a projection fin 11 inclined inward in relation to an axial direction is detachably attached to the downstream end part of the inner tube 1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a noise suppression device, and more particularly, to a noise suppression device that achieves both suppression of jet noise and acceleration of cooling while suppressing influence on engine performance to a minimum.

When high-pressure fluid is discharged from the nozzle end or pipe end, high-speed fluid is formed at these ends. The high-speed fluid diffuses while mixing from the velocity gradient with the surrounding fluid, and noise is generated in the mixing process. This jet noise, which is typical in the exhaust part of a gas turbine engine, has high energy over a wide frequency band, with the surrounding residents in the case of model aircraft jet engines and the airport environment in the case of aircraft jet engines. And aircraft users suffer from unacceptable effects of noise exposure.
In order to suppress such noise, the concept of a bypass engine has been introduced from an early stage in an aircraft jet engine, and the noise has been greatly reduced. This is based on an empirical rule that the energy level of the jet noise is roughly proportional to the 6th to 8th power of the exhaust flow velocity, bypassing a part of the air that the engine inhales and forcing around the high speed flow It is a technology aimed at reducing the average speed of exhaust flow including low-speed flow by introducing it as a low-speed flow. The bypass engine has a normal jet engine (turbo jet engine) as a core engine, and has a low-pressure system outside the core engine. And it is the mechanism which drives the low-pressure system and large-diameter fan in front of the core engine with shaft power generated by a low-pressure turbine or the like. A part of the air flowing in at the front part of the engine passes through the large-diameter fan and is discharged from the rear part of the engine as a low-speed flow without flowing into the core engine. By increasing the ratio of the air flow rate that flows into the core engine and the air flow rate that is bypassed and introduced as a low-speed flow (bypass ratio), a further jet noise reduction effect can be obtained. In an aircraft, the main type of engine form is a bypass engine, and there is a tendency toward higher bypass ratio.
The concept of the bypass engine is based on the viewpoint of achieving noise reduction from the engine system. On the other hand, from the viewpoint of focusing on the local area, there is a technique related to a device that promotes mixing of high-speed flow and ambient air. For example, a lobe-shaped mixing device (lobe mixer) has a flow path for introducing a low-speed flow into the exhaust from the core engine (high-speed flow) and a flow path for introducing a high-speed flow to the low-speed flow side, and there is no device. Compared to the case, it has a structure that promotes mixing of high speed flow and low speed flow at a short distance. As a result of promoting the mixing, not only the noise energy level decreases due to the decrease in the average speed, but also the effect that the noise moves to the high frequency band due to the dispersion of the large-scale vortex is expected. This is because higher frequency sounds are more susceptible to air attenuation and are effective in dealing with noise problems that propagate over long distances.
By the way, a lobe mixer for a gas turbine that aims to improve the structural strength of the lobe mixer, the promotion of mixing, and the like is known (see, for example, Patent Document 1). This lobe mixer is obtained by adding a streamlined structural reinforcing material so that the flow path portion of the lobe mixer avoids deformation and resonance due to fluid force so as not to affect the flow. A lobe mixer is also known that mixes a gas flow while suppressing a decrease in thrust of the jet engine to reduce jet noise (see, for example, Patent Document 2). This lobe mixer aims to promote mixing and increase noise suppression by changing the gradient of adjacent enlarged diameter portions.
On the other hand, there is a technology that uses a tab as a mixing device. Since the tab is a projection that is sufficiently smaller than the nozzle diameter, the ratio of blocking high-speed flow (blockage factor) is small, which is advantageous in that the pressure loss and thrust loss can be suppressed sufficiently low. The tab forms a symmetrical vortex on both edges. This symmetric vortex carries high-speed flow to the surroundings and draws low-speed flow to the high-speed flow side, thereby activating exchange of momentum at the interface between high-speed flow and low-speed flow and macroscopically promoting the mixing. As such a tab mixer, a triangular pyramid formed at the nozzle end is known (see, for example, Patent Document 3). The triangular pyramid protrudes from the inside and outside of the nozzle and aims to suppress thrust loss due to pressure loss while promoting mixing of the flow inside and outside the nozzle. In addition, there is known a lobe mixer that is provided with a plurality of small tabs in the lobe portion and aims to promote mixing (see, for example, Patent Document 4).
In addition, a large and small twisted stirring body is provided inside the flow path, not at the rear end of the flow path, and the main flow is divided while swirling to divide the large-scale vortex and mix it with the flow from the adjacent flow path. Therefore, a noise reduction system aimed at noise suppression or the like is known (see, for example, Patent Document 5).

JP 2003-314368 A JP 2002-317698 A JP 2003-172205 A JP 2004-76596 A Patent No. 3673804

As for the bypass engine, a certain noise suppression effect can be expected by increasing the bypass ratio, but the adverse effect of increasing the size of the engine itself is unavoidable. As a result, the weight of the engine increases and the problem of increased resistance due to an increase in frontal area occurs. From the viewpoint of noise, the size of the fan for introducing low-speed air is increased, so that low frequency noise is relatively increased. The above is the case of an aircraft jet engine, but in the case of a model airplane jet engine, the turbojet engine is still dominant, and has not yet been in a state of benefiting from the bypass engine. In addition to jet engines, it is difficult to introduce the concept of a bypass engine as a general principle for devices that eject high-pressure fluid, and even if possible, significant modifications to existing devices are required. The impact on the future performance is inevitable and economically inconvenient.
The problem with mixing devices such as lobe mixers and tabs is in balancing with pressure loss. This results in an optimal design problem, but there is a problem that it is difficult to flexibly cope with the influence of the engine usage environment and individual differences. If it is a device that has a complicated shape and needs consideration for avoiding vibrations, such as a lobe mixer, it will be even more so that maintenance and modification will be time consuming and expensive.
From the above, while adhering to the basic policy of promoting mixing and suppressing jet noise, the mixing device is simplified, it is easy to attach and detach to improve maintainability, and the characteristics can be adjusted according to engine aging. Therefore, it is a problem to be solved by a noise suppression device that is adaptable if possible and has little adverse effects of pressure loss and weight increase.
Further, in a model airplane or a jet drone, if the engine exhaust is continuously exposed to the exhaust pipe for a long time, there is a risk that deterioration of adjacent parts is accelerated. By utilizing the secondary flow at an intermediate temperature between the engine exhaust and the ambient air to efficiently cool, the local heat load can be reduced and the life of the model or jet drone including parts can be extended. It is beneficial to. Therefore, cooling promotion compatible with noise suppression is also a problem to be solved.

In order to achieve the object, the noise suppression device according to claim 1 is a noise suppression device disposed downstream of an exhaust nozzle of a gas turbine, and the noise suppression device is exhausted from the gas turbine. A double pipe comprising an inner pipe having a core flow path through which a core flow flows, and an outer pipe having an annular flow path positioned outside the core flow path and through which a secondary flow slower than the core flow flows; and The outlet end of the inner tube is located upstream from the outlet end of the outer tube, and a core nozzle having a plurality of fins formed in a protruding shape in the axial direction at the end of the inner tube is removable. The cutout portion of the base portion of the fin is covered with the end portion of the outer tube.
In the above noise suppression device, the noise suppression device constitutes a double pipe composed of an inner tube and an outer tube, and the outlet end of the inner tube is located upstream from the outlet end of the outer tube. Due to the ejector effect of the core flow, or by extracting a high-pressure fluid from a compressor or the like, a secondary flow (medium-speed flow) that is faster than the surrounding air (low-speed flow) is generated or introduced in the annular flow path of the outer pipe, In addition, by reducing the opening area of the annular channel of the outer tube, a small amount of secondary fluid that does not significantly increase the shear with the core flow can be introduced. As a result, this small amount of secondary fluid is discharged from the annular flow path and comes into contact with the high-speed primary fluid, but mixing is started with less shearing force than when low-speed ambient air is in contact with the primary fluid. It becomes like this. Therefore, although the average speed by the final mixing of both fluids is larger than that in the case of mixing the primary fluid and the ambient air, both fluids reach a predetermined speed relatively quickly, and mixing is completed at an early stage. The mixed average flow also mixes with the ambient air and further reduces the average velocity. Compared to the case where secondary fluid does not exist in such so-called two-stage mixing, since individual mixing proceeds without large shear, the formation of large-scale vortices and accompanying low-frequency sounds should be suppressed. Become.
In addition, since the core nozzle is detachably attached to the end portion of the inner tube so that the notch portion of the base portion is covered with the end portion of the outer tube, the core flow and the fin flowing in the vicinity of the fin Due to this interference, a lateral vortex flow is excited with respect to the fin projection direction, and the vortex flow promotes mixing of the core flow and the secondary flow. In this way, by combining the mechanism for introducing the secondary fluid into the primary fluid and the mechanism for promoting the mixing of the primary fluid and the secondary fluid, the impact on the engine performance such as pressure loss and weight increase of the jet flow is minimized. It is possible to suitably suppress the jet noise while suppressing it to the limit.
Further, by making the core nozzle detachable, it is possible to adjust the mixing characteristics and noise characteristics according to the usage situation. Furthermore, the secondary fluid suitably cools the components in the vicinity of the exhaust nozzle such as the inner pipe exposed to the high-temperature and high-pressure combustion gas, so that it contributes to the improvement of the cooling promotion and the extension of the life of the present invention. To come.

The noise suppression device according to claim 2, wherein the fin is formed apart from or adjacent to the circumferential direction of the outlet end portion of the inner pipe, and the fin is inclined inward with respect to the axial direction. It was decided that it was configured.
In the above-described noise suppression device, the vortex is preferably excited from the core flow flowing in the vicinity of the fin, and the vortex becomes a symmetric vortex and exchanges momentum at the boundary surface between the primary fluid and the secondary fluid. The mixing of the two fluids is preferably facilitated.

In the noise suppression device according to the third aspect, the fin is configured by changing the inclination angle stepwise so that the inclination becomes steep as it goes to the tip.
In the above-described noise suppression device, the vortex is preferably excited from the core flow flowing in the vicinity of the fin, and the vortex becomes a symmetric vortex and exchanges momentum at the boundary surface between the primary fluid and the secondary fluid. The mixing of the two fluids is preferably facilitated.

In the noise suppression device according to claim 4, the secondary flow is configured to be generated by an ejector effect of the core flow flowing through the core flow path.
In the above noise suppression device, when the jet velocity is increased, the ejector effect is further enhanced, and the secondary flow velocity and flow rate are relatively increased, and as a result, according to the high velocity velocity. Thus, the mixing promotion effect can be obtained autonomously, and as a result, the noise reduction effect can also be obtained autonomously.

In the noise suppression device according to claim 5, the flow rate and the outflow direction of the secondary flow and the inclination angle of the fin are configured to be adjustable.
In the above-described noise suppression device, by adopting the above-described configuration, when priority is given to improvement in performance deterioration over jet noise reduction, such as during cruising, the flow rate of the secondary flow is reduced and the protrusion is returned to the horizontal to suppress thrust loss. Thus, it becomes possible to adaptively control the balance between noise reduction and performance degradation according to the use situation.

In the noise suppression device according to claim 6, the secondary flow fluid is different from the core flow.
With the above-described noise suppression device, it is possible to form a high-density fluid layer that covers the periphery of a high-temperature and high-pressure core flow. By forming a high-density fluid layer around the high-speed flow, the high-speed flow can be decelerated and propagation of high-frequency sound generated from the high-speed flow can be blocked. On the other hand, when smoke is used as the secondary fluid, visual information regarding the location of the aircraft can be given to the observer.

The noise suppression device according to claim 7, wherein the fin is configured to be provided with an additional mass at the tip of the protrusion, and to vibrate at a predetermined natural frequency when the tip of the protrusion is a cantilever. did.
In the above-described noise suppression device, by adopting the above-described configuration, the primary flow and the secondary flow are compared with the case where there is no vibration due to the projection portion sandwiched between the primary flow and the secondary flow vibrating at a predetermined natural frequency. To promote mixing with.

In the noise suppression device according to claim 8, the core nozzle is fixed only by a loose frictional force with the inner pipe and can be easily attached and detached, and the force pushed backward by a predetermined engine thrust or the natural frequency is reduced. When vibration is applied, it is configured to be automatically detached from the inner tube.
With the above-described noise suppression device, it is possible to suitably prevent thrust loss due to the core nozzle during cruise flight.

According to the noise suppression device of the present invention, it is considered that there are the following effects beyond individual effects by combining a mechanism for introducing a secondary fluid and a mechanism for promoting mixing of the primary fluid and the secondary fluid. .
(1) It is possible to control the state of the symmetric vortex excited from both sides of the notch of the protrusion. For example, by adjusting the vortex dimensions and vortex generation position, it affects the degree of mixing of the primary flow and the secondary flow, the degree of mixing of the secondary flow and ambient air, the noise frequency band, the partial mixing condition, and the frequency band. be able to.
(2) There is generally a slower flow outside the secondary flow. For example, the air flow around the engine nacelle, the air flow around the airframe, and the ambient air in a stationary field. By mixing the medium and high speed flow without directly mixing the high speed flow and the low speed flow, the generation of a sudden shear force is alleviated, and the average speed is reduced while suppressing the generation of large-scale vortices as much as possible. Is expected to decrease.
(3) While cruising in the high altitude, there is little impact of jet noise on the environment around the airport. Rather, it is necessary to maintain good engine performance. At this time, the presence of the secondary flow and the mixing device works in the direction of deteriorating the engine performance in terms of consuming the bleed flow rate or generating a thrust loss. By combining with an appropriate control mechanism, for example, the problem can be solved by turning on and off the bleed amount and the inclination of the projection portion related to the mixing device.
(4) The fluid force excited by the primary flow and the secondary flow causes elastic deformation in the protruding portion. If the entire protrusion has a natural frequency as a cantilever structure and is adjusted so that it resonates when a predetermined fluid force is applied, mixing of the plus alpha is caused by the vibration of the protrusion when a mixing acceleration effect is desired. Promoted.
(5) If the secondary flow (medium speed / medium temperature) is efficiently mixed with the primary flow (high speed / high temperature), it is possible to reduce the heat load of the exhaust pipe, the model machine connected to this, and the structure of the jet drone. .

  Hereinafter, the present invention will be described in more detail with reference to embodiments shown in the drawings. Note that the present invention is not limited thereby.

FIG. 1 is an explanatory view showing a noise suppression device 100 of the present invention.
This noise suppression device 100 includes an inner pipe 1 having a core flow path 1a through which a core flow (primary fluid) ejected from an exhaust nozzle EN of a jet engine flows, and an inner pipe 1 disposed outside the inner pipe 1 and having a lower speed than the core flow. An outer tube 2 having an annular flow path 2a through which a fast flow (secondary fluid) flows, and a removable core nozzle 10 having a plurality of protruding fins 11 attached to an end of the inner tube 1 are configured. .

  The inner outlet end 1b of the inner pipe 1 is disposed so as to be located upstream (engine side) of the outer outlet 2b of the outer pipe 2. Although it is a model airplane jet engine, to give a dimension example, when the inner diameter d of the core flow path 1a is 70 [mm] and the gap t of the annular flow path 2a is 5 [mm], the shift amount L to the upstream side = 10 [mm]. Although details will be described later with reference to FIGS. 2 to 3-3, a small amount of secondary fluid having a flow velocity higher than that of the surrounding air is introduced so as to surround the core flow. As a result, both fluids begin to mix with less shear. Therefore, although the average speed of the final mixing of both fluids is larger than that of the mixing of the primary fluid and the surrounding air, both fluids match the predetermined speed relatively quickly so that the mixing is completed early. become.

  The projecting fins 11 are acute-angled triangles in the present embodiment, but in general, the projecting fins 11 may be a convex polygon having a tip formed in a projecting shape. Further, the notch portion 11a, that is, the valley portion of the projecting fin 11 is covered by the vicinity of the end portion of the outer tube 2, and is further inclined inward with respect to the axial direction and is evenly arranged in the circumferential direction of the inner tube 1. . Although details will be described later with reference to FIG. 4, by arranging in this way, vortices are excited from the core flow in such a manner that the protruding fins 11 are sandwiched from both sides. Mixing with the next stream is promoted.

  Further, the protruding fin 11 has a predetermined natural frequency when a small additional mass is provided at the tip portion and the protruding fin 11 is a cantilever. Although details will be described later with reference to FIG. 6, by configuring in this manner, the protruding fins 11 vibrate and promote mixing of the primary fluid and the secondary fluid.

  For example, the core nozzle 10 is designed to have a predetermined natural frequency so as to resonate when the jet engine generates a predetermined thrust. Further, the mounting of the core nozzle 10 to the inner tube 1 is, for example, fixing by a frictional force with the inner tube 1. Therefore, when a force larger than the frictional force acts on the core nozzle 10, for example, shearing due to the core flow The core nozzle 10 is separated from the inner tube 1 when force, vibration at the time of resonance, or the like is applied. Thereby, for example, when the aircraft flies at the cruising speed and the core nozzle 10 becomes unnecessary, the fitting condition is appropriately set so that the magnitude of the frictional force is smaller than the force received from the core flow during cruising. The core nozzle 10 can be automatically separated from the inner tube 1, thereby preventing a reduction in thrust.

  Since the secondary flow flowing through the annular flow path 2a cools the inner tube 1, the thermal load due to the core flow of these components is reduced.

FIG. 2 is an explanatory diagram showing a mechanism for introducing a secondary fluid, which is one of the basic configurations of the present invention.
One feature is the introduction of a much smaller amount of secondary fluid than the concept of a bypass engine. The mechanism according to the present invention eliminates the need for a fan or the like that generates a fluid to be bypassed, so that the apparatus size can be suppressed and the influence on the apparatus performance can be minimized. Specifically, a thin annular flow path is provided on the outer periphery of the exhaust nozzle or the exhaust pipe, and the annular flow path (2a in FIG. 1) is faster than the low-speed surrounding fluid and slower than the primary fluid (referred to as medium speed). Uses a structure that allows a small amount of fluid to conduct.

FIG. 3A is an explanatory diagram showing an example in which the mechanism for introducing a secondary fluid according to the present invention is applied to a jet engine exhaust pipe for a model airplane.
The secondary fluid is driven by using a drawing effect (a so-called ejector effect) by a high-speed flow in the primary fluid discharge part or by using a part of the compressor bleed air. An annular pipe is provided so as to have a thin gap outside the exhaust pipe. The rear end of the annular pipe is adjusted to be behind the rear end of the exhaust pipe. The front end of the exhaust pipe is installed behind the engine nozzle, and the outer annular pipe is directly connected to a closed space that covers the entire engine. The air in the gap joined to the annular pipe covering the rear end of the exhaust pipe is pulled and discharged by the ejector effect of the high-speed flow discharged from the rear end of the exhaust pipe during engine operation.

  When this small amount of secondary fluid is discharged from the annular channel, it will come into contact with the high-speed primary fluid, but mixing will start with less shearing force than when the low-speed surrounding fluid is in contact with the primary fluid. To do. Therefore, although the final average speed is larger than that in the case of mixing with ambient air, both fluids reach a predetermined speed relatively quickly and mixing is completed at an early stage. The mixed average flow also mixes with the ambient air to further reduce the average velocity. Such apparent two-stage mixing can suppress the formation of large-scale vortices and the accompanying low-frequency sound because individual mixing proceeds without large shear as compared to the case where no secondary fluid is present.

  The annular flow path for conducting the secondary fluid also serves as a cooling effect for the exhaust nozzle or the exhaust pipe. In particular, in a model airplane, in the form in which the engine is included in the fuselage, it is essential to cool the exhaust pipe because the exhaust pipe at the rear is at a high temperature, which hinders structural safety. Due to the ejector effect at the end of the exhaust pipe, the air in the gap between the exhaust pipe and the annular pipe is sucked out, and the exhaust pipe outer surface directly connected to this and the engine are cooled (FIGS. 3-1 to 3-3). .

FIG. 4 is an explanatory view showing an attachment / detachment device that promotes mixing, which is one of the basic configurations of the present invention.
If the large-scale flow can be divided into smaller structures at the mixing stage, the corresponding frequency can be shifted to the higher side, and subsequent treatment such as air attenuation and sound absorbing material becomes easier. On the other hand, when using a mechanical mixing device such as the lobe mixer or tub, it is necessary to balance the problem of pressure loss as the price for mixing fluids having different speeds. However, this is based on the premise that fluids with a large speed difference are mixed. When mixing the medium-speed secondary flow and the high-speed flow, a certain effect can be achieved with a gentler mixing device. I can expect that. In the present invention, a plurality of arbitrarily-shaped cutouts (projection fins 11 in FIG. 1) are provided in the circumferential direction at the end of the nozzle or the exhaust pipe, and the root of the cutout is in front of the end of the annular pipe. A detachable device configured as described above is employed.

When the notch at the end of the exhaust pipe is slightly inclined toward the high-speed flow side, vortices are excited from both ends perpendicular to the high-speed flow of the notch to the medium-speed flow side. This vortex becomes a symmetric vortex and has a function of promoting exchange of momentum, ie, mixing, at the interface between the medium speed flow and the high speed flow. By providing a plurality of notches along the circumference of the rear end of the exhaust nozzle or the exhaust pipe, a large number of vortices are excited to promote mixing of the high speed flow and the low speed flow.
When the ejector effect of the exhaust pipe is required as the drive source of the secondary flow, if the root portion of the notch is inclined, the drive of the secondary flow is suppressed. After discharging the next flow, it is also conceivable to provide a device that is generally provided after the rear end of the annular pipe. For example, a notch having an arbitrary curvature or a notch having a slope only at a tip portion thereof can be considered.
It is effective to adjust the mixing characteristics and noise characteristics according to the use situation even if the same exhaust nozzle or exhaust pipe is provided with a detachable part having a notch. This is because the degree of mixing and loss characteristics are expected to vary depending on the shape of the notch.

FIG. 5 is an explanatory diagram illustrating an exhaust noise reduction device for a model airplane or a jet drone according to the first embodiment.
It consists of a double pipe structure connected to the space that covers the engine and a mixing promotion device that can be attached to and detached from the inner pipe and has a protrusion shape. As a result of the secondary flow discharge by the ejector effect at the end of the double pipe and the mixing promotion effect by the protrusion shape effect, noise Can be suppressed.
Model airplanes or jet drones have a long ground standby time, so considering the fact that there is a lot of noise exposure not only during flight but also when traveling on the ground, a mixing effect due to low-speed flow (flow around the aircraft) is expected. Therefore, it is important to suppress the noise by the secondary flow and the protruding mixing device based on the embodiment.
In addition, by making the mixing promotion device a detachable structure that uses only frictional holding, for example, if the mixing promotion device is adjusted so as to be released with takeoff by the thrust force during takeoff, a model machine or unmanned It can be avoided that the aircraft suffers thrust loss due to the mixing promoting device during flight.

FIG. 6 is an explanatory diagram of the smoke generator for a model airplane according to the second embodiment.
Since the mixing is performed gently, the smoke has the effect of extending sufficiently backward. Since the smoke flows so as to cover the core, the smoke flow rate can be suppressed, and the smoke for a long time and the mounted weight can be reduced.
In addition, when smoke is used as a means to visually identify the location of the jet drone during an emergency landing, a certain amount of smoke can be released for a long time, and the smoke can extend as long as possible along the flight path. It is desirable to be released. By applying the embodiment in response to such a request, it is possible to release smoke or the like that exhibits discriminating power over a wide range, and contribute to early detection of an unmanned aircraft or the like.

FIG. 7 is an explanatory diagram illustrating an aircraft jet engine noise suppression apparatus according to a third embodiment.
Although it is the same idea as Example 1, you may install a double pipe structure only in a nozzle part. The secondary flow may use bleed air such as a compressor, and by controlling the bleed flow rate with a flow rate adjustment valve or the like, the vortex shape formed in the protruding shape related to the mixing device is controlled, and the degree of mixing or It is conceivable to adaptively control the amount of noise generated.

  In addition, the secondary flow rate can be changed by controlling the extraction flow rate with a flow rate adjusting valve or the like. Furthermore, it is possible to change not only the inclination angle of the projection fin 11 but also the secondary flow outflow direction by an electric / hydraulic / pneumatic mechanism or by the action of the shape memory alloy.

  The secondary flow is not limited to air. For example, a specific liquid may be ejected in a ring shape at a high pressure or vapor. By forming a high-density fluid layer covering the periphery of the high-speed and high-temperature gas flow, the high-speed flow is decelerated and the effect of shielding the high-frequency sound generated from the high-speed flow is expected. In general, a liquid has a higher heat transfer coefficient than a gas, so that it also serves as a cooling effect for the protruding portion.

  The noise suppression device of the present invention can be applied to noise suppression of an aircraft jet engine and noise suppression of a jet drone or a model airplane, as well as extending the life of the engine and visual smoke.

It is composition explanatory drawing which shows the noise suppression apparatus of this invention. It is explanatory drawing which shows the mechanism which introduces the secondary fluid which is one of the fundamental structures of this invention. It is explanatory drawing which shows an example which applied the mechanism which introduces the secondary fluid which concerns on this invention to the jet engine exhaust pipe for model airplanes. It is explanatory drawing which shows the expansion of the exhaust rear part of FIGS. It is explanatory drawing which shows the mixing process of FIGS. 3-2. It is explanatory drawing which shows the attachment / detachment apparatus which accelerates | stimulates mixing which is one of the basic structures of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows the exhaust noise reduction apparatus for model airplanes or jet drones based on Example 1. FIG. It is explanatory drawing which shows the smoke production | generation apparatus for model airplanes which concerns on Example 2. FIG. It is explanatory drawing which shows the jet engine noise suppression apparatus for aircraft which concerns on Example 3. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inner pipe 1a Core flow path 2 Outer pipe 2a Annular flow path 10 Core nozzle 11 Protrusion fin 100 Noise suppression apparatus

Claims (8)

  A noise suppression device disposed downstream of an exhaust nozzle of a gas turbine, wherein the noise suppression device includes an inner pipe having a core flow path through which a core flow exhausted from the gas turbine flows, A double pipe composed of an outer pipe having an annular flow path located outside and having a secondary flow flow slower than the core flow, and the outlet end of the inner pipe is upstream of the outlet end of the outer pipe And a core nozzle having a plurality of fins formed in a projecting shape in the axial direction at the end of the inner tube is detachably mounted, and a notch at the base of the fin is formed on the outer tube. A noise suppression device that is covered with an end portion.   2. The fin according to claim 1, wherein the fins are spaced apart from or adjacent to each other along a circumferential direction of an outlet end portion of the inner pipe, and the fins are inclined inward with respect to an axial direction. Noise suppression device.   The noise suppression device according to claim 1, wherein the fin is configured by changing an inclination angle in a stepwise manner so that the inclination becomes steep as it goes to a tip.   The noise suppression device according to any one of claims 1 to 3, wherein the secondary flow is generated by an ejector effect of a core flow that flows through the core flow path.   The noise suppression device according to any one of claims 1 to 4, wherein the flow rate and outflow direction of the secondary flow and the inclination angle of the fin are adjustable.   The noise suppression device according to claim 1, wherein the secondary flow fluid is different from the core flow.   The noise suppression according to any one of claims 1 to 6, wherein the fin is configured such that an additional mass is provided at a tip of the protrusion, and the fin is vibrated at a predetermined natural frequency when the tip of the protrusion is a cantilever. apparatus.   The core nozzle is fixed only by a loose frictional force with the inner tube and can be easily attached and detached. When the force pushed backward by a predetermined engine thrust or the vibration of the natural frequency is applied, the core nozzle is automatically The noise suppression device according to any one of claims 1 to 7, wherein the noise suppression device is configured to be detached from the tube.

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