CN104405530B - Separately gas-discharging type turbofan engine exhausting and denoising system - Google Patents

Abstract

The invention relates to a separate exhaust type turbofan engine exhaust noise reduction system, which belongs to the technical field of aeroengine exhaust system design and exhaust noise reduction. It is characterized in that: the exhaust noise reduction system consists of the outer wall of the outer culvert (1), the outer wall of the outer culvert (2), the inner wall of the outer culvert (3), the inner swirler (4), and the exhaust rectification inner cone (5 ), the exhaust inlet of the outer culvert (6), the exhaust inlet of the inner culvert (7), the exhaust outlet of the outer culvert (8), the exhaust outlet of the inner culvert (9), and the outer wall of the inner culvert (10). The invention has simple structure and little influence on engine exhaust performance.

Description

Separate exhaust turbofan engine exhaust noise reduction system

technical field

The invention relates to a separate exhaust type turbofan engine exhaust noise reduction system, which belongs to the technical field of aeroengine exhaust system design and acoustic noise reduction.

Background technique

Under the circumstance that people have increasingly urgent requirements for environmental protection, the International Civil Aviation Organization and governments of various countries have paid more and more attention to the control of civil aircraft noise. Aircraft engine noise is one of the main components of aircraft noise, and jet flow noise is an important component of engine noise, especially in the take-off state. For the aero-engine exhaust system, the active jet noise suppression technology is an important issue in the field of aeroacoustics and aero-engine research. Nozzle jet noise reduction and other aspects have important application background.

Specifically, the aerodynamic noise of a civil turbofan engine with a large bypass ratio split exhaust mainly comes from the fan, turbine and jet. Among them, the jet flow noise is formed when the high-temperature and high-speed exhaust gas is mixed with the surrounding atmosphere, and a part of the energy is radiated in the form of sound energy due to the strong turbulence caused by the large speed difference. The sound power is almost proportional to the 8th power of the jet velocity. In direct proportion, the spectrum of the noise power is closely related to the structure of the jet, which has obvious directivity, and the noise intensity is difficult to attenuate by acoustic treatment.

In order to suppress the exhaust jet noise, the patents (US4372110, US4720901, US4909346, US5060471, US5722233, US5755092) mentioned that the lobe mixer is used to strengthen the mixing of the internal and external duct airflow of the turbofan engine, or introduce the external environment gas into the engine exhaust The nozzle is mixed with the exhaust to reduce the exhaust velocity and suppress the exhaust noise. These technical measures are suitable for the exhaust noise reduction of the exhaust system of the hybrid exhaust turbofan engine. The patent (US5761900) mentions the exhaust noise reduction technology of the two-pole injection hybrid structure, but it increases the length of the engine exhaust nozzle, and is not suitable for a separate exhaust turbofan engine. Patents (US6360528B1, US6487848B2) proposed adding a sawtooth crown structure at the end of the engine exhaust nozzle to strengthen the mixing of the engine jet flow and the external environment airflow, so as to attenuate the exhaust velocity and reduce the exhaust noise. Compared with the lobe mixer , the flow direction vortex strength produced by the sawtooth structure is much weaker, so the effect of strengthening mixing is poorer. The patent (US6571549B1) conceives a pulse jet generator arranged circumferentially outside the outlet of the nozzle. The generated pulse jet stimulates the engine exhaust jet, attenuates the engine exhaust speed, and achieves the purpose of noise reduction. However, this device increases engine complexity.

The invention provides a turbofan engine exhaust noise reduction structure with simple structure and little negative impact on engine exhaust performance.

Contents of the invention

The object of the present invention is to provide a separate exhaust type turbofan engine exhaust noise reduction system with simple structure and little influence on engine exhaust performance.

The exhaust noise reduction system includes the outer culvert exhaust channel, the inner exhaust channel, and the exhaust rectification inner cone from the outside to the inside; the outer culvert exhaust channel is composed of the outer wall surface of the outer culvert and the inner wall surface of the outer culvert, and the inner exhaust channel It is composed of the outer wall surface of the inner culvert and the inner cone of exhaust rectification; it is characterized in that: the outer culvert swirler is installed in the exhaust passage of the outer culvert; in the radial direction, the outer culvert swirler is installed on the outer wall of the outer culvert and inside the outer culvert Between the walls; in the circumferential direction, the outer culvert swirlers are evenly arranged, and there are more than four swirl blades; in the axial direction, the outer culvert swirlers are located at the end of the outer culvert exhaust passage, and the outer culvert swirlers The central axis of the engine has a certain installation angle, and the angle is between 10-30 degrees; the internal swirl is installed in the above-mentioned internal exhaust passage; in the radial direction, the internal swirl is installed on the exhaust rectification inner cone and the internal outer Between the walls; in the circumferential direction, the internal swirlers are evenly arranged, and there are more than four swirl blades; in the axial direction, the internal swirlers are located at the end of the internal exhaust passage, and the internal swirlers have a certain distance from the central axis of the engine. The installation angle, the angle is between 10-30 degrees; the installation angle of the above-mentioned external swirler and internal swirler is opposite to the central axis of the engine, that is, the direction of rotation is opposite.

It can be seen from this patent that the direction of rotation of the external cyclone and the internal cyclone is opposite. Therefore, compared with the inner and outer exhaust without rotation, the counterclockwise outer exhaust and the clockwise inner exhaust under the action of rotation strengthen the mixing between the inner and outer exhaust, thus reducing the exhaust speed to achieve the purpose of reducing exhaust noise.

The invention has the following advantages: the structure of the inner and outer cyclones is simple, and the manufacturing and installation costs are low. The inner and outer swirlers will not change the original structure of the separate exhaust turbofan exhaust system. The number of swirlers and the deflection angle can be selected according to the compromise between exhaust noise reduction level and exhaust loss. Compared with the exhaust noise reduction measures of other structures, the swirler noise reduction measures cause less loss to the engine exhaust and have better noise reduction effects.

The swirler is an important component in the present invention, and the installation angle of the swirler has an influence on the engine exhaust performance and exhaust noise suppression effect. Generally, the larger the installation angle, the greater the exhaust aerodynamic loss and the better the noise reduction effect. In addition, the installation angle should be adjusted accordingly with the size of the exhaust system of the split-exhaust turbofan engine. The specific angle value should be based on the overall aerodynamic and noise design requirements of the engine, and an optimized and compromised result should be obtained through numerical simulation and experiments, basically within the range of 10-30 degrees.

Similarly, the number of swirl blades of the swirler is also a quantity that requires specific analysis of specific problems. Generally, the more the number, the greater the exhaust aerodynamic loss and the better the noise reduction effect. Generally, more than four are recommended.

Description of drawings

Attached drawing 1 is a schematic diagram of a turbofan engine exhaust noise reduction system (any angle of view);

Attached drawing 2 is a schematic diagram (side view) of the turbofan engine exhaust noise reduction system;

Attached drawing 3 is a schematic diagram of a turbofan engine exhaust noise reduction system (two-dimensional symmetrical section);

Attached drawing 4 is a schematic diagram of the exhaust inner cone plus inner swirler (any angle of view);

Attached drawing 5 is a schematic diagram of the exhaust inner cone plus inner swirler (side view);

Attached drawing 6 is a schematic diagram of the exhaust inner cone plus inner swirler (rear view);

Attached drawing 7 is a schematic diagram of the inner wall of the outer culvert plus the outer culvert cyclone (any angle of view);

Attached drawing 8 is a schematic diagram of the inner wall of the outer culvert plus the outer culvert cyclone (side view)

Attached Figure 9 is a schematic diagram of the inner wall of the outer culvert plus the outer culvert cyclone (rear view);

Label names in the figure: 1. Outer wall of outer culvert, 2. Cyclone of outer culvert, 3. Inner wall of outer culvert, 4. Inner cyclone of inner culvert, 5. Inner cone of exhaust rectification, 6. Exhaust inlet of outer culvert, 7. Connotation exhaust inlet, 8. Extent exhaust outlet, 9. Connotation exhaust outlet, 10. Connotation outer wall.

detailed description

FIG. 1 , FIG. 2 and FIG. 3 are the overall structure of exhaust noise reduction of the separated exhaust turbofan engine proposed by the present invention. The connotation outer wall surface 10 and the wall surface of the exhaust rectifying inner cone 5 form a connotation exhaust passage, and the connotation exhaust inlet 7 is connected with the engine turbine outlet. Connotation cyclone4. Figure 4, Figure 5 and Figure 6 show the structure of the exhaust rectifying inner cone 5 and the connotation swirler 4, the connotation swirler (4) at the end of the connotation channel has a certain angle θ with the central axis of the engine, and the connotation exhaust is in the connotation Under the action of the swirler 4, clockwise or counterclockwise rotation occurs relative to the central axis of the engine (clockwise and counterclockwise here are related to the position of the observer. For the accompanying drawing 6 of this patent, looking forward from the rear of the engine, The rotation direction of the internal cyclone is clockwise.

The outer wall surface 1 of the outer culvert and the inner wall surface 3 of the outer culvert constitute the exhaust channel of the outer culvert, and the exhaust inlet 6 of the outer culvert is connected with the outlet of the fan of the outer culvert; The structure of the outer and inner cyclone 2 is designed. Fig. 7, Fig. 8 and Fig. 9 are based on Fig. 4, Fig. 5 and Fig. 6 and show the structure of the inner wall surface 3 of the exoculum and the structure of the cyclone 2 of the exoculum. The outer culvert swirler 2 located at the end of the outer culvert channel also has a certain angle θ with the central axis of the engine. Under the action of the outer culvert swirler 2, the outer culvert exhaust rotates clockwise or counterclockwise relative to the central axis of the engine ( Clockwise and counterclockwise here are related to the position of the observer. For the accompanying drawing 9 of this patent, when viewed from the rear of the engine, the rotation direction of the external swirler is counterclockwise.

As shown in Figures 1, 2, and 3, the specific method for reducing exhaust noise in the invention is as follows: the outer culvert air compressed by the outer culvert fan of the engine enters the outer culvert exhaust passage from the outer culvert exhaust inlet 6, and the outer culvert exhaust passage is formed by The part of the outer wall surface 1 of the outer culvert and the inner wall surface 3 of the outer culvert, the air of the outer culvert accelerates in the outer culvert channel to the end of the outer culvert channel, and under the diversion action of the outer culvert swirler 2, the velocity component of the circumferential motion is formed , when the outer culvert exhaust leaves the outer culvert exhaust outlet 8, it forms a counterclockwise rotation movement. Viewed from the tail of the engine, the outer culvert exhaust with counterclockwise rotation moves downstream while rotating;

The internal gas at the outlet of the engine turbine enters the internal exhaust passage through the internal exhaust inlet 7, and the internal exhaust passage is composed of the external wall surface 10 of the internal body and the part of the exhaust rectification inner cone 5, and the internal gas accelerates in the internal channel to the end of the internal channel , under the diversion action of the internal swirler 4, the speed component of the circumferential motion is formed, and when the internal exhaust leaves the internal exhaust outlet 9, it forms a clockwise rotating motion. Viewed from the tail of the engine, it has a clockwise The Connotation of Rotation The exhaust moves downstream while rotating.

When the counterclockwise-rotating outer exhaust moves to the downstream and contacts the clockwise inner exhaust, under the action of the opposite velocity gradient and gas viscosity, strong shear first occurs on the contact surface of the inner and outer exhaust. Cut and mix, and gradually spread to the inside and outside of the exhaust. Because the inner and outer exhausts have opposite rotations as a whole, this mixing not only works on the contact surface of the inner and outer exhausts, but also penetrates into the core of the inner and outer exhausts. Therefore, the velocity of the inner and outer contained gases attenuates quickly, and the effect of reducing exhaust noise is good. The enhanced mixing of internal and external gases occurs outside the exhaust system, and the viscous loss due to the mixing has little effect on the exhaust aerodynamic performance of the engine.

According to CFD (computationalfluiddynamics) and CAA (computationaeroacoustic) numerical simulations, when the swirler installation angle θ is 20° and the number of swirler blades reaches more than 4, the exhaust noise of the engine is reduced by more than 2dB, and the exhaust loss is less than 0.1%. .

Claims (1)

1. separate a gas-discharging type turbofan engine exhausting and denoising system,

Exhausting and denoising system comprises outer culvert exhaust passage, intension exhaust passage, exhaust rectification inner cone (5) from outside to inside successively; Its China and foreign countries contain exhaust passage and are made up of outer culvert outer wall (1) and outer culvert internal face (3), and intension exhaust passage is made up of intension outer wall (10) and exhaust rectification inner cone (5);

It is characterized in that:

In above-mentioned outer culvert exhaust passage, outer culvert cyclone separator (2) is installed; Diametrically, outer culvert cyclone separator (2) is installed between outer culvert outer wall (1) and outer culvert internal face (3); In circumference, outer culvert cyclone separator (2) is evenly arranged, the swirl vane of cyclone separator more than four; Axially, outer culvert cyclone separator (2) is positioned at outer culvert exhaust passage end, and contains cyclone separator (2) and engine center axis outward and have certain setting angle, and this angle is between 10-30 degree;

Intension cyclone separator (4) is installed in above-mentioned intension exhaust passage; Diametrically, intension cyclone separator (4) is installed between exhaust rectification inner cone (5) and intension outer wall (10); In circumference, intension cyclone separator (4) is evenly arranged, the swirl vane of cyclone separator more than four; Axially, intension cyclone separator (4) is positioned at intension exhaust passage end, and intension cyclone separator (4) and engine center axis have certain setting angle, and this angle is between 10-30 degree;

Above-mentioned outer culvert cyclone separator (2), intension cyclone separator (4) are contrary with the setting angle of engine center axis, and namely rotation direction is contrary.