CN112502853A

CN112502853A - Nozzle, jet engine and jet aircraft equipped with same

Info

Publication number: CN112502853A
Application number: CN202011362510.5A
Authority: CN
Inventors: 王磊; 刘凯礼; 管健; 钟园; 杨柳; 邵庆龄
Original assignee: Comac Shanghai Aircraft Design & Research Institute; Commercial Aircraft Corp of China Ltd
Current assignee: Comac Shanghai Aircraft Design & Research Institute; Commercial Aircraft Corp of China Ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-03-16
Anticipated expiration: 2040-11-27
Also published as: CN112502853B

Abstract

The invention relates to a nozzle (2) for a jet aircraft engine. The nozzle wall (20) of the nozzle (2) is formed with at least one slit (24), the slit (24) extending towards the nozzle outlet (23) of the nozzle (2) and terminating in a nozzle trailing edge (25) of the nozzle (2). The width of the slit (24) increases monotonically in the direction of flow (21, 22) of the air flow inside and outside the nozzle. The jet pipe can reduce exhaust noise and does not cause obvious adverse effect on performances of a jet engine such as thrust and the like. The invention also relates to a jet engine and a jet aircraft equipped with the jet pipe.

Description

Nozzle, jet engine and jet aircraft equipped with same

Technical Field

The present invention relates to a nozzle tube for reducing exhaust noise, and more particularly to a nozzle tube for a jet aircraft engine, which is constructed to reduce exhaust noise. The invention also relates to a jet engine and a jet aircraft equipped with the jet pipe.

Background

A jet aircraft is an aircraft that uses jet engines as a source of propulsive force. Jet engines used in jet aircraft utilize the recoil effect of high velocity backward jets of gases produced during fuel combustion, causing the aircraft to fly forward. Compared with other types of aircrafts, the jet engine can enable the aircraft to obtain larger thrust and have higher flying speed.

With faster flight speeds, a tremendous amount of noise is generated. Jet engine nozzle exhaust is one of the major noise sources for jet aircraft. To reduce the noise generated by nozzle exhausts, various methods of reducing exhaust noise have been employed, one of which is to enhance the mixing between the different velocity streams. Specifically, a lobe mixer may be installed at the trailing edge of the engine nozzle, or the trailing edge of the engine nozzle may be formed as a tab or serration, or the like, or a jet may be added at the trailing edge of the engine nozzle, or the like. By the aid of the method, mixing of air flows with different speeds can be enhanced, and accordingly exhaust noise of the spray pipe is reduced.

For example, in U.S. patent 6,360,528B1 issued by general electric company on 3/26 2002, a V-shaped exhaust nozzle for a gas turbine engine is disclosed. The gas turbine engine exhaust nozzle includes an exhaust pipe for directing a jet of gas. A plurality of adjacent chevrons are provided at the rear end of the exhaust pipe to define an exhaust outlet. Each chevron has a triangular configuration with a base, an apex, side trailing edges converging therebetween and defining boundaries on diametrically opposed first and second surfaces. The chevrons have concave and convex profiles in the axial direction of the exhaust pipe to promote jet mixing through the exhaust pipe.

However, the above design has disadvantages. For example, because the chevrons have a triangular configuration and project rearwardly from the trailing edge of the prior nozzle and inwardly toward the central axis of the nozzle, significant thrust losses may result in practical applications affecting the flight performance of the jet. Similarly, tabs and serrations formed at the trailing edge of the nozzle also present similar problems.

As for the other means mentioned above, there are problems that the lobe mixer is complicated in process, is not easy to manufacture, or the equipment for providing the jet flow costs extra cost. Therefore, these noise reduction means are difficult to put into practical use due to poor economy.

Therefore, there is a need to develop a technical means for effectively reducing the exhaust noise of the nozzle at low cost.

Disclosure of Invention

The object of the present invention is to provide a nozzle tube for a jet aircraft engine, which nozzle tube can reduce its exhaust noise efficiently at low cost.

Other objects of the invention are to provide a jet engine and a jet aircraft equipped with the above-mentioned nozzle.

According to a first aspect of the invention, there is provided a nozzle for a jet aircraft engine, wherein the nozzle wall of the nozzle is formed with at least one slot extending towards the nozzle outlet of the nozzle and terminating at the nozzle trailing edge of the nozzle, wherein the width of the slot increases monotonically in the direction of flow of the air stream inside and outside the nozzle.

In a preferred embodiment, twelve slots may be formed in the wall of the nozzle, the slots being evenly distributed around the circumference of the nozzle outlet.

In another preferred embodiment, the slots may be divided into a slot first region, a slot second region, and a slot third region in order from the slot leading edge toward the nozzle outlet of the nozzle, wherein the widths of the slot first region, the slot second region, and the slot third region monotonically increase along the airflow flow direction inside and outside the nozzle.

Preferably, the width of the slot front can be designed to be about 1% of the diameter of the nozzle outlet.

Preferably, the width of the slot ending at the nozzle trailing edge of the nozzle can be designed to be about 12% of the diameter of the nozzle outlet.

Preferably, the length of the slot may be designed to be about 60% of the diameter of the spout outlet.

In still another preferred embodiment, the rate of increase in the width of the second region of the slit may be higher than the rate of increase in the width of the first region of the slit and the third region of the slit.

Furthermore, the nozzle can be used as a bypass nozzle or bypass nozzle for a turbofan engine.

A second aspect according to the invention relates to a jet engine equipped with a nozzle according to the first aspect of the invention.

A third aspect according to the invention relates to a jet aircraft equipped with a jet engine according to the second aspect of the invention.

The nozzle tube for a jet aircraft engine according to the invention has the following advantages:

the slit with the shape can enhance the mixing of air flows at the inner side and the outer side of the spray pipe, and the exhaust noise of the spray pipe is effectively reduced by utilizing the flow direction vortex formed by the front edge of the slit. By selecting better design parameters, the exhaust noise of the spray pipe can be reduced, and meanwhile, obvious adverse effects on performances such as thrust of the jet engine are not caused.

Drawings

In order to further illustrate the structure of the nozzle for a jet aircraft engine according to the invention and its technical effects, the invention will be explained in detail below with reference to the accompanying drawings and specific embodiments, in which:

FIG. 1A is a schematic side view of a conventional spout having a circular outlet;

FIG. 1B is a schematic rear view of a conventional nozzle having a circular outlet;

FIG. 2A is a schematic side view of a nozzle according to the present invention with a plurality of slots uniformly distributed at the trailing edge of the nozzle;

FIG. 2B is a schematic rear view of a nozzle according to the present invention with a plurality of slots uniformly distributed about the trailing edge of the nozzle;

FIG. 3 is a schematic view of one of the slits of FIGS. 2A and 2B showing in greater detail the shape of the leading edge and the side edges of the slit;

FIG. 4A is a graph illustrating a measurement of the noise generated by the nozzle of FIGS. 1A and 1B;

FIG. 4B is a graph illustrating a measurement of the noise generated by the nozzle of FIGS. 2A and 2B;

fig. 5 is a schematic view of the application of a nozzle according to the invention in a turbofan engine.

Reference numerals

1 conventional nozzle

10 wall of a conventional nozzle

11 flow direction of air flow inside conventional nozzle

12 flow direction of air flow outside traditional spray pipe

13 conventional nozzle outlet

15 conventional nozzle trailing edge

2 spray pipe

20 nozzle wall

21 direction of flow of the gas stream inside the nozzle

22 direction of flow of the air stream outside the nozzle

23 spout outlet

24 slit

241 slit leading edge

242 slit side edges

243 slit both sides air flow direction

244 slit viewing direction

25 trailing edge of nozzle

I slit first section

II second section of slit

III slit third section

Detailed Description

The structure of the nozzle for a jet aircraft engine according to the invention and its technical effects with respect to conventional nozzles are explained below with reference to the accompanying drawings, in which like parts are indicated by like reference numerals.

It should be understood that the embodiments described herein cover only a portion of the embodiments of the invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive step based on the embodiments described in the description, are within the scope of protection of the present invention.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "comprising" and "having," and any variations thereof, in the description and claims of the present invention and the description of the above figures are intended to cover non-exclusive inclusions. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

It is to be understood that in describing the present invention, the terms "center," "length," "width," "thickness," "upper," "lower," "front," "rear," "top," "bottom," "inner," "outer," and the like are used in the orientation or positional relationship indicated in the drawings to facilitate the description of the invention and to simplify the description, and are not intended to indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Fig. 1A and 1B are schematic side and rear views of a conventional spout 1. It can be seen that a conventional nozzle 1 for a jet aircraft engine is formed by a conventional nozzle wall 10 in the shape of a hollow cylinder. The end of the conventional nozzle 1 communicating with the jet engine (not shown in the figures) can be defined as the proximal end, which is intended to receive the products of combustion of the fuel in the jet aircraft engine, such as carbon dioxide, sulphur dioxide, carbon monoxide, nitrogen oxides, small hydrocarbons which are not completely combusted, etc. The opposite end of the conventional nozzle 1 from the proximal end is defined as the distal end which extends outwardly along the length of the conventional nozzle 1 and begins to converge slightly at a location proximate the trailing edge 15 of the conventional nozzle to increase the exit velocity of the exhaust gases at the conventional nozzle exit 13.

It can be seen that the diameter of the conventional nozzle 1 remains substantially constant along its length, but that the conventional nozzle trailing edge 15 of the conventional nozzle 1 has a diameter that decreases in the circumferential direction towards the central axis of the conventional nozzle 1 in the vicinity of the conventional nozzle trailing edge 15. Referring to fig. 1B, two concentric circles are depicted, representing the proximal and distal ends of the conventional nozzle 1, respectively.

As shown in fig. 1A, the dotted arrow 11 indicates the flow direction of the air flow inside the conventional nozzle 1, and the solid arrow 12 indicates the flow direction of the air flow outside the conventional nozzle 1. It will be apparent that the direction of flow 11 of the gas stream inside the conventional lance 1 and the direction of flow 12 of the gas stream outside the conventional lance 1 are substantially parallel to the length of the conventional lance 1 and that the direction of flow 11 of the gas stream inside the conventional lance 1 and the direction of flow 12 of the gas stream outside the conventional lance 1 are in the same direction, i.e. from the proximal end of the lance 1 to the distal end of the lance 1.

The air flow inside the conventional nozzle 1 and the air flow outside the conventional nozzle 1 meet at the nozzle outlet 13, and the shearing action between the two air flows results in the formation of noise. Fig. 4A plots decibel values for noise at each frequency band obtained at the outlet side of the conventional nozzle 1 spaced approximately twenty times the diameter of the nozzle outlet 13. It can be seen that the value at which the sound pressure level peak of the noise occurs is high when the frequency of the noise is in the range of 0 to 2 KHz; when the frequency of the noise is in the range of 2 to 4KHz, the absolute value of the sound pressure level value and the fluctuation rate of the noise are substantially maintained at a high level although they are lowered.

Fig. 2A and 2B are schematic side and rear views of a spout 2 according to the present invention. Likewise, the lance 2 according to the invention is formed by a lance wall 20 in the shape of a hollow cylinder. The proximal end of the lance 2 receives the products of the combustion of fuel in a jet aircraft engine and the distal end of the lance 2 extends outwardly along the length of the lance 2 and begins to converge slightly at a location near the trailing edge 25 of the lance to increase the velocity of the exhaust gases exiting at the lance outlet 23. The dashed arrows 21 indicate the direction of flow of the gas stream inside the lance 2, while the solid arrows 22 indicate the direction of flow of the gas stream outside the lance 2.

Unlike the conventional lance 1, the lance wall 20 of the lance 2 according to the present invention is formed with at least one slot 24. In a preferred embodiment, twelve slots 24 are formed in the nozzle wall 20, each slot 24 being uniformly distributed along the circumference of the nozzle outlet 23. Of course, it will be readily understood by those skilled in the art that the number of slots 24 may be varied, for example, eight or sixteen slots 24 or another number of slots 24 may be formed in the nozzle wall 20, or the slots 24 may be non-uniformly distributed about the nozzle outlet 23 in the circumferential direction of the nozzle outlet 23, and such variations are within the scope of the present invention.

The "circumferential direction" of the nozzle outlet 23 is based on the fact that the nozzle wall surface 20 of the nozzle 2 is a hollow cylinder. When the nozzle wall 20 of the nozzle 2 has a non-hollow cylindrical shape, the slits 24 may be distributed uniformly or non-uniformly in the circumferential direction or circumference of the nozzle outlet 23.

As shown in fig. 2A, a plurality of slits 24 extend towards the nozzle outlet 23 of the nozzle 2 and terminate at a nozzle trailing edge 25 of the nozzle 2, wherein the width of the slits 24 increases monotonically in the airflow flow directions 21, 22 inside and outside the nozzle 2. In comparison to the conventional nozzle 1, since the plurality of slits 24 are added to the nozzle wall surface 20 of the nozzle 2 according to the present invention, a plurality of cutaway portions are formed in fig. 2B on a circle having a smaller diameter in a concentric circle than in fig. 1B.

The arrow 244 in fig. 2B is perpendicular to one of the above-mentioned cutaway portions and points to the center point of the nozzle outlet 23, and fig. 3 is an enlarged schematic view of one of the slits 24 as viewed in the direction of the arrow 244. It can be seen that the slot 24 is divided into a slot first region I, a slot second region II and a slot third region III (shown in dashed lines in fig. 3) in that order from the slot leading edge 241 towards the nozzle outlet 23 of the nozzle 2. The widths of the first, second and third slit regions I, II, III increase monotonically in the airflow direction 21, 22 inside and outside the nozzle.

Note that the arrows 243 in fig. 3 show the airflow flowing directions on both sides of the slit 24, and it can be seen that the slit 24 has an axisymmetric shape whose axis of symmetry is substantially parallel to the airflow flowing directions 243 on both sides of the slit 24.

The term "slit width" refers to the dimension of the slit 24 in a direction perpendicular to its axis of symmetry or the airflow direction 243 on either side of the slit 24. As shown in fig. 3, the leading edge 241 of the slit 24 is located on the left side in the drawing. Starting from the slot leading edge 241, the slot width gradually increases and reaches a width maximum at the trailing edge of the slot 24, i.e. the nozzle trailing edge 25.

The term "monotonically increasing" refers to a state in which the width of the slit 24 is constantly increasing from the slit leading edge 241 in the airflow flow directions 21, 22 inside and outside the nozzle tube. That is, the shape of the slot side edges 242 of the slot 24 is always diverging relative to the axis of symmetry of the slot 24 in the direction of airflow flow 21, 22 inside and outside the nozzle.

As can be seen, the slit width at any of the slit second regions II of the slit 24 is larger than the slit width at any of the slit first regions I of the slit 24, and the slit width at any of the slit third regions III of the slit 24 is larger than the slit width at any of the slit second regions II of the slit 24. Of course, the width of the slit 24 in the slit first region I, the slit second region II, and the slit third region III is also monotonically increased.

In a preferred embodiment, the width of slot leading edge 241 is about 1% of the diameter of nozzle exit 23. That is, the diameter of the nozzle outlet 23 is approximately one hundred times the width of the slot leading edge 241. The width of the slot 24 terminating at the nozzle trailing edge 25 of the nozzle 2 is about 12% of the diameter of the nozzle outlet 23. That is, the width of the slot 24 terminating at the nozzle trailing edge 25 of the nozzle 2 is approximately twelve times the width of the slot leading edge 241. In addition, the length of the slit 24 is about 60% of the diameter of the spout outlet 23.

Here, the term "slit length" means the dimension of the slit 24 from the slit leading edge 241 to the nozzle trailing edge 25, which should be parallel to the symmetry axis of the slit 24 or the airflow flow direction 243 on both sides of the slit 24.

Of course, one of ordinary skill in the art can also vary at least one of the width of the slot leading edge 241, the width of the slot 24 terminating at the nozzle trailing edge 25 of the nozzle 2, and the length of the slot 24 in the preferred embodiment described above. Such variations are intended to fall within the scope of the present invention.

Since the shape of the slit side edge 242 of the slit 24 is expanded at all times with respect to the symmetry axis of the slit 24 in the airflow flowing directions 21 and 22 inside and outside the nozzle, it can be considered that the width increase rates of the slit first region I, the slit second region II, and the slit third region III are all larger than zero.

Here, the term "width increase rate" refers to a ratio of a width of a subsequent unit length to a width of a previous unit length in the unit length. When the width increase rate is greater than zero, the width is indicated to be increasing; when the width increase rate is less than zero, the width is reduced; when the width increase rate is equal to zero, it indicates that the width has not changed. The larger the absolute value of the width increase rate is, the larger the rate of width increase is.

In another preferred embodiment, the width increase rate of the slit second region II is higher than the width increase rate of the slit first region I and the slit third region III. That is, the slit side edges 242 of the slit 24 are shaped to expand slowly with respect to the symmetry axis of the slit 24 in the slit first region I, to expand rapidly with respect to the symmetry axis of the slit 24 in the slit second region II, and to expand slowly with respect to the symmetry axis of the slit 24 in the slit third region III.

Such a slit shape is generally used in other fields such as an intake duct, and can reduce the resistance of the intake duct and improve the intake efficiency of the intake duct as compared with other shapes such as a rectangular shape. The inventors of the present application have found that the use of this shape for the slot 24 is effective in improving nozzle thrust loss, thereby achieving unexpected technical results. In addition, the slot structure of the present invention differs in at least the following ways, as compared to structures such as chevrons, tabs, serrations on existing exhaust nozzles:

(1) the construction mode is different: in the invention, a plurality of slits 24 are cut in front of the nozzle outlet 23, while in the prior art, various structures extend behind the traditional nozzle outlet 13;

(2) the trailing edge shape is different: the present invention forms a narrow slot 24 at the nozzle trailing edge 25, with slot side edges 242 shaped to expand slowly at the front, expand rapidly at the middle, and expand slowly at the rear, as opposed to the prior art where a generally triangular or saw-tooth shaped protrusion is formed at the conventional nozzle trailing edge 15;

(3) the effect principle is different: the principle of noise reduction of the present invention mainly lies in the flow direction vortex generated by the slit leading edge 241, thereby also reducing the thrust loss of the nozzle, while the prior art mainly lies in the effect that the sharp corner at the traditional nozzle trailing edge 15 extends into the jet flow, and the thrust loss of the nozzle is obviously greater than that of the present invention through simulation calculation.

Fig. 4B plots decibels of noise for each frequency band obtained at the outlet side of the nozzle 2 according to the present invention spaced approximately twenty times the diameter of the nozzle outlet 23. It was found that when the noise frequency is in the range of 0 to 2KHz, the sound pressure level of the noise is significantly reduced from the peak value of fig. 4A by about 20 dB; the absolute value of the sound pressure level value of the noise also drops slightly when the noise frequency is in the range of 2 to 4 KHz. It follows that the nozzle according to the invention is effective in reducing exhaust noise compared to the conventional nozzle 1. This is because: the nozzle interior and nozzle exterior airflows will first meet at the slot leading edge 241 and slot side edges 242 of the slot 24 before the nozzle outlet 23 meets. The shape of the slot leading edge 241 and slot side edges 242 of the slot 24 results in the formation of streamwise vortices in the airflow, the effect of which can reduce the shear strength of the nozzle interior and nozzle exterior airflow as they meet at the nozzle outlet 23, thereby reducing noise.

Fig. 5 is a schematic view of the application of a nozzle according to the invention in a turbofan engine. It will be seen that the nozzle according to the invention can be used both as a connotation nozzle of a turbofan engine and as a bypass nozzle of a turbofan engine, or as both. In the case of simultaneous use as both, the inner and outer culvert pipes of the turbofan engine can be designed with different embodiments, without being limited to pipes having the same structure.

The invention also relates to a jet engine equipped with a jet pipe 2 as described above. The invention also relates to a jet aircraft equipped with a jet engine as described above.

While the nozzle, jet engine and jet aircraft incorporating the nozzle of the present invention have been described above in connection with preferred embodiments, those of ordinary skill in the art will recognize that the foregoing examples are intended to be illustrative only and are not intended to be limiting. Therefore, modifications and variations of the present invention may be made within the true spirit and scope of the claims, and these modifications and variations are intended to fall within the scope of the claims of the present invention.

Claims

1. A nozzle (2) for a jet aircraft engine, characterized in that a nozzle wall (20) of the nozzle (2) is formed with at least one slit (24), which slit (24) extends towards a nozzle outlet (23) of the nozzle (2) and terminates in a nozzle trailing edge (25) of the nozzle (2), wherein the width of the slit (24) increases monotonically in the direction of flow (21, 22) of the air flow inside and outside the nozzle.

2. A nozzle (2) according to claim 1, wherein twelve slits (24) are formed in the nozzle wall (20), the slits (24) being evenly distributed in the circumferential direction of the nozzle outlet (23).

3. A nozzle (2) according to claim 1, wherein the slot (24) is divided in the order of a slot first region (I), a slot second region (II) and a slot third region (III) from a slot front edge (241) towards a nozzle outlet (23) of the nozzle (2), wherein the width of the slot first region (I), the slot second region (II) and the slot third region (III) increases monotonically in the direction of flow (21, 22) of the gas stream inside and outside the nozzle.

4. A lance (2) according to claim 3, wherein the width of the slot leading edge (241) is about 1% of the diameter of the lance outlet (23).

5. A nozzle (2) according to claim 3, wherein the width of the slot (24) terminating at the nozzle trailing edge (25) of the nozzle (2) is about 12% of the diameter of the nozzle outlet (23).

6. A lance (2) according to claim 3, wherein the length of the slot (24) is about 60% of the diameter of the lance outlet (23).

7. A nozzle (2) according to claim 3, wherein the slit second region (II) has a higher rate of increase of width than the slit first region (I) and the slit third region (III).

8. The lance (2) as claimed in claim 1, wherein the lance is used as a culvert lance or a culvert lance for a turbofan engine.

9. A jet engine equipped with a nozzle (2) according to any one of claims 1 to 8.

10. A jet aircraft provided with a jet engine as claimed in claim 9.