JP5447920B2 - Aircraft exhaust nozzle - Google Patents

Description

  The present invention relates to an aircraft exhaust nozzle, particularly an aircraft exhaust capable of preventing an increase in engine air resistance during high subsonic cruising while reducing exhaust jet noise during takeoff without increasing the size of the apparatus. This relates to the nozzle.

The exhaust noise of an aero engine is a sound wave emitted to the surroundings from a so-called shear layer, which is a large velocity difference generated when a high-speed air current is blown into still air. It is known that the strength of sound depends on the strength and length of the shear layer (see, for example, Non-Patent Document 1).
Therefore, to reduce the exhaust noise, the most direct and effective approach is to keep the exhaust speed itself low. For this reason, the concept of a bypass engine has been introduced from early on in aircraft jet engines and has achieved significant noise reduction. 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 sound is more susceptible to air attenuation and is effective in dealing with noise problems that propagate over long distances (see, for example, Patent Document 1 and Patent Document 2).
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 Co-authored by Keiichi Igarashi (and 1 other), “Noise Engineering”, Corona Publishing, 1989

Among the high bypass ratio turbofan jet engines that are currently the mainstream as aero engines, engines with a large bypass ratio have been put into practical use from the viewpoint of jet noise reduction during takeoff and fuel consumption rate reduction. There are also engines that exceed.
However, in the case of such a high bypass ratio engine, the thrust difference between takeoff and high subsonic cruise is large, increasing the pressure ratio of the compressor, increasing the nitrogen oxide emission due to the increase in combustion temperature, and the heat resistant material Life is shortened.
In addition, in a turbofan jet engine with a small bypass ratio, a lobe mixer such as a petal is added to the exhaust nozzle duct to reduce jet noise during takeoff, and the fan exhaust is introduced into the core exhaust and mixed. Although the above-mentioned silencer for reducing the exhaust jet speed and reducing the exhaust jet noise has been put into practical use, it has not yet reached a technical level to obtain a silencing performance sufficient to satisfy the current noise regulations.
In addition, the above-mentioned silencer, which incorporates a sound absorbing mechanism on the duct surface, or provides an unevenness called a tab or chevron at the rear end of the exhaust nozzle to mute the sound, is also extremely limited and has a technical level to obtain a sound deadening performance. It has not reached. Also, thrust loss is inevitable.
In addition, it is possible to easily reduce the noise by introducing a duct to the outside of the exhaust nozzle outlet and introducing external air due to the ejector effect, but the weight increase is significant and the resulting noise reduction effect is small. There's a problem.
Aircraft engine noise regulations are becoming stricter year by year. When the above conventional methods are applied, the size of the equipment becomes large, increasing the emission of nitrogen oxides, reducing the life of heat-resistant materials, increasing the weight, or thrust loss. Absent.
Therefore, the present invention was devised in view of the above circumstances, and its purpose is to reduce the exhaust jet noise during take-off without increasing the size of the device, and to reduce the air resistance of the engine during high subsonic cruises. It is an object to provide an aircraft exhaust nozzle capable of preventing an increase in the amount of air.

In order to achieve the above object, an aircraft exhaust nozzle according to claim 1, wherein an impeller that rotates in response to an air current is connected to both the inside and the outside that have a relatively high flow velocity with respect to the exhaust nozzle or fan duct. It arrange | positions in the form which opposes the air current of 2 and receives both air currents alternately .
In the above-described aircraft exhaust nozzle, with the above-described configuration, the air flow of both the exhaust jet ejected from the inside of the exhaust nozzle and the external flow having a relatively small flow velocity and the external flow having a relatively small flow velocity outside the exhaust nozzle hits the impeller. , Flows backward while rotating the impeller. At that time, an impeller facing the exhaust jet flow having a relatively high flow velocity inside the exhaust nozzle (hereinafter referred to as “high-speed side impeller”) functions and rotates as a turbine, and the flow velocity outside the exhaust nozzle is relatively high. An impeller that faces a small external flow (hereinafter referred to as “low-speed impeller”) functions and rotates as a fan. The low speed side impeller accelerates and discharges the low speed external flow backward while receiving work from the high speed side impeller. As a result, at the time of takeoff, the speed difference between the exhaust jet flow and the external flow is reduced downstream of the impeller, and the exhaust jet noise is suitably reduced. At the same time, the effective bypass ratio is increased by the fan function of the impeller, so that thrust is increased and fuel efficiency is improved.
On the other hand, during high subsonic cruising, in the aircraft exhaust nozzle, the airflow outside the exhaust nozzle increases in speed and passes through the impeller at high speed. Similarly, the airflow inside the exhaust nozzle also passes through the impeller. As a result, the impeller is idling. Then, since the high speed side impeller does not absorb work from the exhaust gas, the effective bypass ratio becomes small and the thrust is not insufficient.
In addition, the aircraft exhaust nozzle is a very simple mechanism in which an impeller is added to a conventional exhaust nozzle or fan duct, so that it is possible to suitably reduce exhaust jet noise while suppressing increase in size and weight of the device. It becomes possible.

The aircraft exhaust nozzle according to claim 2 is characterized in that the impeller can be rotated by receiving power from other than the airflow.
As described above, since the high-speed impeller functions and rotates as a turbine by the high-speed exhaust jet flow, the turbine efficiency depends on the rotational speed. Therefore, when the high-speed impeller is operating in a range lower than the optimum rotational speed range, the work as a fan is reduced because work is not absorbed from the exhaust jet flow, and as a result, the exhaust jet noise is reduced. The reduction effect is also reduced.
In such a case, the aircraft exhaust nozzle can supply power from the outside to compensate for the shortage of power. As a result, the high-speed impeller can always be operated within the optimum rotational speed range, the turbine efficiency can be prevented from being lowered, and the exhaust jet noise can be suitably reduced.

The aircraft exhaust nozzle according to claim 3, wherein a plurality of impellers having the same size or different sizes are arranged so as to overlap or not overlap on a cross section orthogonal to the axial direction of the exhaust nozzle. It was decided.
With the above-described configuration, the aircraft exhaust nozzle can be optimized to reduce exhaust jet noise during takeoff and to reduce engine air resistance during high subsonic cruise.

The aircraft exhaust nozzle according to claim 4 is characterized in that the impeller can be braked, fixed, or retracted.
In the aircraft exhaust nozzle, by adopting the above-described configuration, the life of the impeller is extended and the air resistance of the engine is prevented from increasing.

The aircraft exhaust nozzle according to claim 5 is characterized in that the rotation shaft of the impeller can be offset from the exhaust nozzle wall surface in a direction intersecting therewith.
In the aircraft exhaust nozzle, the ratio of the turbine operation and the fan operation of the impeller can be adjusted by adopting the above configuration.

The aircraft exhaust nozzle according to claim 6 is characterized in that the offset amount of the rotating shaft of the impeller is variable.
In the aircraft exhaust nozzle, with the above-described configuration, it is possible to obtain an optimum ratio of turbine operation and fan operation in accordance with the flight state.

The aircraft exhaust nozzle according to claim 7 is characterized in that a cover is installed on the entire circumference or part of the outside of the impeller.
In the aircraft exhaust nozzle, the above-described configuration increases the fan efficiency and suppresses noise emission to the outside.

Since the aircraft exhaust nozzle of the present invention is configured as described above, it has the following effects.
(1) First, at the time of takeoff, the high-speed impeller that faces the exhaust jet flow inside the exhaust nozzle functions and rotates as a turbine by the exhaust jet flow inside. On the other hand, the low-speed impeller facing the external airflow outside the exhaust nozzle functions and rotates as a fan by the high-speed impeller, sucks air, and discharges it backward. As a result, the speed difference between the exhaust jet flow and the surrounding external airflow is reduced downstream of the impeller, and the exhaust jet noise is suitably reduced. In addition, since the effective bypass ratio is increased by the fan function of the low-speed impeller, it is expected that the thrust during takeoff increases and the fuel consumption is improved.
(2) Next, during subsonic cruising, when the aircraft enters a high-speed flight state, the airflow speed outside the exhaust nozzle rises and passes through the impeller at high speed. Similarly, the exhaust jet flow inside the exhaust nozzle Passing through the vehicle at high speed, the impeller is idled as a result. Then, since the impeller does not absorb work from the exhaust gas, the effective bypass ratio is reduced and the thrust is not insufficient.
(3) Further, since the aircraft exhaust nozzle is a very simple mechanism in which the impeller is added to a conventional exhaust nozzle or fan duct, the exhaust jet noise is suitably suppressed while suppressing the increase in size and weight of the device. It becomes possible to reduce.
The above also applies to the fan duct arranged in such a manner that the impeller straddles the bypass flow inside the fan duct and the external airflow outside the fan duct.

  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 low noise exhaust nozzle 100 of the present invention.
The low-noise exhaust nozzle 100 is arranged along the circumferential direction of the rear end of the core nozzle 1 in such a manner that it alternately receives both the inner high-speed exhaust jet flow and the outer low-speed bypass flow with respect to the core nozzle (exhaust nozzle) 1. Are arranged along the circumferential direction of the rear end of the fan duct 2 in such a manner that the air flow of both the inner bypass flow and the outer external air flow are alternately received with respect to the plurality of impellers 10 and the fan duct 2. It is comprised from the several impeller 20 made.

The details will be described later with reference to FIG. 2-4. By arranging the impellers 10 and 20 at the rear end of the core nozzle 1 and the rear end of the fan duct 2, the inner high speed flow is opposed at takeoff. The high-speed impeller that functions and rotates as a turbine, and the low-speed impeller that faces the low-speed flow outside thereof functions and rotates as a fan by the high-speed impeller. As a result, the speed difference between the inner airflow and the outer airflow is reduced downstream of each impeller, and the exhaust noise is suitably reduced. In addition, since the effective bypass ratio increases, the thrust during takeoff increases and fuel efficiency is improved.
On the other hand, at the time of subsonic cruise, each air velocity increases so that each air flow passes through the impeller at high speed, and the impeller enters an idle state. Then, since the impellers 10 and 20 do not absorb work from each high-speed flow, the effective bypass ratio is reduced and the thrust is not insufficient.

  The impellers 10 and 20 are known rotary machines that rotate by the energy of fluid, and are configured to be able to rotate by receiving external power from a power source such as an electric motor in addition to the airflow. Moreover, it is comprised so that it can displace to the direction which cross | intersects a core nozzle wall surface or a fan duct wall surface. Thereby, in the impellers 10 and 20, it becomes possible to adjust the efficiency (rotational speed control) at the time of turbine operation, and the ratio of turbine operation and fan operation.

  In addition, the impellers 10 and 20 include a brake mechanism that suppresses rotation in order to stop the turbine operation and the fan operation.

  In addition to the rear end, the impellers 10 and 20 may be arranged at other positions, for example, at an intermediate position between the core nozzle 1 or the fan duct 2.

FIG. 2 is an explanatory view showing an impeller 10 according to the present invention. The configuration of the impeller 20 is exactly the same.
The impeller 10 includes a rotor blade 11 that receives airflow to work, a rotor portion 12 to which the rotor blades 11 are attached at equal intervals, a rotating shaft 13 that inputs and outputs rotational power, and bearing portions 14 and 14 thereof. A motor 15 and its bearings 16 and 16 as an external power source when the rotational speed of the rotor unit 12 decreases, and a clutch mechanism 17 for intermittently (ON / OFF) the rotational power of the motor 15 transmitted to the rotor unit 12 And vertical position variable mechanisms 18, 18, 18, 18 for changing the position of the rotary blade 11 in the vertical direction. The “vertical direction” here means a direction perpendicular to the wall surface of the core nozzle. In addition, the mechanisms other than the rotary blade 11 are housed inside the core nozzle wall so that they do not resist the exhaust jet flow and the bypass flow (external flow).

  The number of blades of the rotary blade 11 is eight in this embodiment, but is not limited to this number. The mounting angle of the rotor blade 11 is determined by the turbofan engine as a base.

  All the bearings 14 and 16 are supported by, for example, a vertical position variable mechanism 18. Further, all the bearings 14 and 16 are bearings having a small rotational resistance, and are constituted by, for example, ball bearings.

  When the rotational speed of the rotor unit 12 decreases, the motor 15 supplies rotational power to the impeller 10 via the clutch mechanism 17 to rotate the rotor unit 12 at a predetermined rotational frequency. Further, when it is not desired to operate the impeller, the impeller 10 is stopped by the braking torque of the motor 15 by connecting the clutch mechanism 17. That is, when the rotational power of the impeller is transmitted to the motor 15, a counter electromotive force is generated in the motor 15 in a direction to cancel the rotation of the impeller, and an induced current flows. As a result, a braking torque that cancels the rotation is generated by the induced current, and the impeller 10 coupled to the motor 15 is stopped by the braking torque. Alternatively, a brake mechanism may be attached to the end of the rotating shaft 13 without using the braking torque of the motor 15. Alternatively, when the impeller 10 has a small diameter, the entire impeller is accommodated in a case, an opening / closing mechanism is provided at the opening of the case, and when the impeller 10 is not desired to be operated, the opening / closing mechanism is closed and the inside and outside Therefore, the impeller 10 can be stopped from operating. In addition, the case suppresses noise emission to the outside during the operation of the impeller 10.

  The clutch mechanism 17 is, for example, a hydraulic clutch. When the clutch is connected, the clutch disk is pressed against the flywheel by a hydraulic control circuit (not shown), and the rotational power of the motor 15 is transmitted to the rotor unit 12. As a result, the rotational speed of the impeller can be controlled within a predetermined range, and as described above, the efficiency of the impeller 10 as a turbine can be controlled within the predetermined range. The clutch mechanism can employ an electromagnetic clutch or a fluid clutch in addition to the hydraulic clutch.

  The vertical position variable mechanism 18 can be configured by, for example, a hydraulic cylinder or a linear motor. Thereby, the rotary blade 11 can be displaced in the vertical direction, and as described above, the ratio of the turbine operation and the fan operation can be controlled to a predetermined ratio.

FIG. 3 is an explanatory view showing an example of drawing the impeller 10 into the cowl space.
As shown in FIG. 3 (a), the impeller 10 is coupled with an expansion / contraction mechanism 30 that expands / contracts the impeller 10 in the axial direction, and a rotation mechanism 40 that rotates the expansion / contraction mechanism 30 at an end of the expansion / contraction mechanism 30. Are combined. Accordingly, in order to store the impeller 10 in the cowl space, first, as shown in FIG. 3B, the rotating mechanism 40 rotates the impeller 10 and the telescopic mechanism 30 to stand upright on the core nozzle wall surface. At that time, a slit opening / closing mechanism (not shown) that allows the impeller 10 to pass through the cowl 3 opens, so that the impeller 10 and the telescopic mechanism 30 stand upright without interfering with the cowl 3. Then, as shown in FIG. 3 (c), the telescopic mechanism 30 is contracted in the axial direction, and then, as shown in FIG. 3 (d), the rotating mechanism 40 is displaced inside the core nozzle by the slide mechanism (not shown). The slit opening / closing mechanism of the cowl 3 is closed, and the drawing of the impeller 10 into the cowl space is completed.

As another example of retracting the impeller 10, a method of retracting the impeller 10 into a space inside the main wing can be considered as shown in FIG.
In this manner, by combining the impeller 10 with the expansion / contraction mechanism and the rotation mechanism, the impeller 10 can be housed in the form of drawing in or near the engine.

FIG. 5 is an explanatory diagram showing an example of the arrangement of the impellers 10 and 20 according to the present invention.
This is because the impeller 10 is disposed at equal intervals of 90 ° along the outer periphery of the rear end of the core nozzle 1, and the impeller 20 is disposed at the rear end of the fan duct 2 with a phase difference of 45 ° with respect to the impeller 10. This is an example in which they are arranged at equal intervals of 90 ° along the outer periphery. The phase difference is arbitrary. Further, the impeller may be placed alone, or may be placed so as to overlap with other impellers in the projected cross section. Further, the size of each impeller may not be uniform (not all impellers having the same diameter). Moreover, the number of each impeller may not be uniform.

  Further, as shown in FIG. 6, a configuration in which two impellers 10 and 10 ′ having different rotation directions are overlapped and arranged on the outer periphery of the core nozzle 1 or the fan duct 2 may be employed.

Here, as a reference, the impeller performance estimation model will be briefly described.
As shown in FIG. 7, it is assumed that a cylinder with an inner diameter D is divided into two equal parts. The respective regions are H and L, and the total pressure is P _tH and P _tL . However, P _tH > P _tL . A rotating blade row is placed at the end of this cylinder. Then, depending on the twisting state of the blade row and the velocity of the gas flowing through both flow paths, the blade row performs work or is worked.
The aerodynamic characteristics of the impeller is represented by its blade element in the average diameter r _m to be estimated the overall operation.
The speed triangle is defined as shown in FIG.
γ is the stagger angle, and the camber angle θ of the blade is 0 for now.
It is assumed that the flow is two-dimensional, and the flow surface is a cylindrical surface.
That is, U ₁ = U ₂ and ρ ₁ V _1a = ρ ₂ V _2a hold.
Set the deviation to 0. Therefore, the flow flows out in the direction of the exit angle of the flat blade element.
(Relative energy perspective)
For blades that rotate regularly,
When DI / Dt = T · (Ds / Dt) + W · F, F = 0 due to inviscidity and Ds / Dt = 0 due to adiabatic flow, the rotary rupee I is preserved before and after the blade.
Since it defined as Rotarupi I = H-Ω · r · V θ, the total enthalpy H = h + V ^2/2
I ＝ h ₁ + (1/2) ・ (W ₁ ² −U ₁ ² ) ＝ h ₂ + (1/2) ・ (W ₂ ² −U ₂ ² )
Is established before and after the blade row.
Now assuming a cylindrical surface, r ₁ = r ₂ = r _m ,
h ₂ −h ₁ = (1/2) ・ (W ₁ ² −W ₂ ² )
It becomes.
H ₂ −H ₁ = C _p・ (T _t2 −T _t1 ) = U (V ₁ sinα ₁ −V ₂ sinα ₂ )
If the flow is in the axial direction upstream of the blade row and flows out in the blade row direction, α ₁ = 0, β ₂ = γ,
H ₂ −H ₁ = C _p・ (T _t2 −T _t1 ) = − UV ₂ sinα ₂
When the outflow angle at the cascade outlet viewed from the stationary system is in the same direction as the rotation, the compressor will increase the total enthalpy H, and in the reverse direction, the turbine will decrease the total enthalpy H. When α ₂ = 0, the flow is not changed by the moving blade, and it is in a windmill state. Further, if U = 0, that is, if the moving blade is stopped, the total enthalpy H does not increase and represents the state of the stationary blade.
In general, when the impeller is in steady rotation, the external force is zero, so in this impeller, in order to balance in the total cross-sectional area,
∫ _s (ρ ₂ H ₂ V _a2 −ρ ₁ H ₁ V _a1 ) = 0.
In the case of the figure, Σ _{i = H, L} [ρ ₂ H ₂ V _a2 −ρ ₁ H ₁ V _a1 ] _i = 0 holds when the upper and lower passages are combined, and the compressor work and the turbine work are balanced.
[ρ ₂ H ₂ V _a2 −ρ ₁ H ₁ V _a1 ] _H = − [ρ ₂ H ₂ V _a2 −ρ ₁ H ₁ V _a1 ] _L
ΡV _a is constant before and after the cascade
(ρV _a ) _H (H ₂ −H ₁ ) _H = − (ρV _a ) _L (H ₂ −H ₁ ) _L
(ρV _a ) _H C _p U (−V ₂ sinα ₂ ) _H = − (ρV _a ) _L C _p U (−V ₂ sinα ₂ ) _L
ρV _a = PM _a (κ / RT) ^1/2 = P _t (M _a / A) (κ / RT _t ) ^1/2 , provided that A = {1+ (1/2) (κ−1) M ² } ^{(1/2) (κ + 1) / (κ−1)}
V ₂ = M ₂ [κRT _t2 / {1+ (1/2) (κ−1) M ₂ ² }] ^1/2
Therefore, depending on the conditions on the H side and the L side, the exit speed triangle on the H side and the L side is ρV ₂ , which is almost the inverse ratio of P _t , steady at the rotational speed U that gives the circumferential speeds in opposite directions. It will work.

Exit condition is
T _t2 = T _t1 −UV ₂ sinα ₂ / C _p
Since isentropic flow is assumed,
P _t2 ＝ P _t1 (T _t2 / T _t1 ) ^{κ / (κ−1)} ＝ P _t1 [1-UV ₂ sinα ₂ / (C _p T _t1 )] ^{κ / (κ−1)}
The Mach number at the exit is
M ₂ = [2 / (κ−1) {(P _t2 / P _∞ ) ^{(κ−1) / κ} −1}] ^1/2
The speed at the exit is
V ₂ = M ₂ [κRT _t2 / {1+ (1/2) (κ−1) M ₂ ² }] ^1/2
This is obtained by repeated calculation.
The relationship between the cross-sectional area of the isentropic flow and the Mach number is
A / A ^* = (1 / M) [{(κ−1) M ² +2} / (κ + 1)] ^{(1/2) (κ + 1) / (κ−1)}
It is. Where A ^* is the choke area.
A ^* = 1 / (ρ ^* a ^* ) = {1+ (κ−1) / 2} ^{1 / (κ−1)} / {P _t / (RT _t )} · [1 / {2κRT _t / (κ +1)} ^1/2 ] = {RT _t (κ + 1) / (2κ)} ^1/2 / P _t · {1+ (κ−1) / 2} ^{1 / (κ−1)}
Under the condition of M ₂ > 1, the flow is choked at the cascade. The choking flow expands to ambient pressure, but assuming a cylindrical flow, it can be accelerated only in the axial direction and the flow angle is small.
As a typical example, consider a high bypass ratio turbofan. If the bypass ratio is 6 and the fan pressure ratio is 1.5 in a stationary state on the ground, the fan outlet temperature is 1.14 times 328K.
Turbine work when an impeller with a rotating blade mounting angle of 10 to 80 degrees is rotated under fan outlet air conditions, and fan work that the same impeller sucks static air and pressurizes, and the rotational speed of the impeller is a parameter Is plotted as shown in FIG.
The point at which the work curves of the turbine and the fan having the same blade attachment angle intersect with each other is a condition for steady rotation of H and L. This point is represented by an asterisk (☆).
The theoretical value of sound power in Lighthill's subsonic jet theory is the quadrupole noise.
P _j = 2πρ ₀ u _e ⁸ D ² / a ₀ ⁵
And is proportional to the eighth power of the exhaust velocity u _e .
From Table 1, the degree of noise is reduced for the exhaust jet that blows into the static atmosphere at 269m / s.

FIG. 11 is an explanatory diagram illustrating the low noise exhaust nozzle 200 according to the first embodiment.
The low noise nozzle 200 reduces exhaust jet noise by combining the impeller 10 and the lobe mixer 30. When one or a plurality of impellers are arranged coaxially with the exhaust nozzle (core nozzle 1) in this way, by arranging them downstream of the lobe mixer 30 that mixes the core flow and the bypass flow or the core flow and the external flow, Since different flows of energy are alternately applied to the impeller, the exhaust jet noise is suitably reduced by the turbine operation and fan operation of the impeller 10 as described above. That is, in the low noise exhaust nozzle 100, the impeller is arranged in a form straddling both airflows in the vertical direction. However, in the low noise exhaust nozzle 200, the impellers straddle both airflows alternately along the circumferential direction. It is arranged in the form. In this case, even if the cowling 40 is omitted from the low noise exhaust nozzle 200, the exhaust jet noise can be suitably reduced. In this embodiment, the outer diameter of the impeller 10 is larger than the outer diameter of the lobe mixer 30, but the present invention is not limited to this, and the exhaust jet noise can be suitably reduced even when the impeller 10 is small.

  As described above, according to the present invention, the impeller that faces the inner airflow having a relatively large flow velocity functions and rotates as a turbine by arranging the impeller across the two airflows having different flow velocities. Then, the impeller facing the air flow having a small flow velocity outside is functioned and rotated as a fan. Thereby, at the time of takeoff, the speed difference between the inner exhaust jet flow and the outer external air flow is reduced downstream of the impeller, and exhaust jet noise can be reduced. Further, since the effective bypass ratio increases downstream of the impeller, thrust is increased and fuel efficiency is improved. On the other hand, during subsonic cruising, the airflow speed outside the engine increases and passes through the impeller at high speed. Similarly, the exhaust jet flow inside the engine also passes through the impeller at high speed. It will be idle. As a result, since the impeller does not absorb work from the exhaust jet flow, the effective bypass ratio is reduced and the thrust is not insufficient.

  The aircraft exhaust nozzle of the present invention is applicable to internal combustion engines and compressors that inject exhaust gas such as gas turbines.

It is explanatory drawing which shows the low noise exhaust nozzle of this invention. It is explanatory drawing which shows the impeller which concerns on this invention. It is explanatory drawing which shows the example of drawing in the cowl space of an impeller. It is explanatory drawing which shows the example of drawing in to the wing | blade internal space of an impeller. It is explanatory drawing which shows an example of arrangement | positioning of the impeller which concerns on this invention. It is explanatory drawing which shows an example of arrangement | positioning of the impeller which concerns on this invention. It is explanatory drawing which shows the rotary blade spanning two flows. It is explanatory drawing which shows the change of the flow by a rotary blade. It is explanatory drawing which shows the state of the flow before and behind a rotary blade. It is a graph which shows the work of the impeller which concerns on this invention. It is explanatory drawing which shows the low noise exhaust nozzle which concerns on Example 1. FIG.

DESCRIPTION OF SYMBOLS 1 Core nozzle 2 Fan duct 3 Cowl 10,20 Impeller 11 Rotating blade 12 Rotor part 13 Rotating shaft 14,16 Bearing 15 Motor 17 Clutch mechanism 18 Vertical position variable mechanism 100,200 Low noise exhaust nozzle

Claims (7)

The impeller that rotates in response to the airflow is arranged in a form that faces both the inner airflow and the outer airflow that have a relatively high flow velocity with respect to the exhaust nozzle or the fan duct and alternately receives both airflows. Aircraft exhaust nozzle.   The aircraft exhaust nozzle according to claim 1, wherein the impeller is rotatable by receiving power from other than the airflow.   3. The aircraft exhaust nozzle according to claim 1, wherein a plurality of impellers having the same size or different sizes are arranged so as to overlap or not overlap each other on a cross section orthogonal to an axial direction of the exhaust nozzle. .   The exhaust nozzle for an aircraft according to any one of claims 1 to 3, wherein the impeller can be braked, fixed, or retracted.   2. The aircraft exhaust nozzle according to claim 1, wherein the rotation shaft of the impeller can be offset from the exhaust nozzle wall in a direction intersecting with the exhaust nozzle wall.   The aircraft exhaust nozzle according to claim 5, wherein an offset amount of the rotation shaft of the impeller is variable.   The aircraft exhaust nozzle according to any one of claims 1 to 6, wherein a cover is installed on the entire circumference or part of the outside of the impeller.

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