阅读说明：本技术 一种膨胀偏转喷管主动热防护结构 (Active heat protection structure of expansion deflection spray pipe ) 是由 杨正 谢侃 李想 李泓瑾 苗龙 王宁飞 于 2021-07-02 设计创作，主要内容包括：本发明公开一种膨胀偏转喷管主动热防护结构,包括燃烧室,燃烧室的一端固接有喷管,燃烧室与喷管连通,燃烧室内设置有空心圆柱体,空心圆柱体的一端与燃烧室固接,空心圆柱体另一端固接有导流器,空心圆柱体与导流器连通,导流器位于喷管内；导流器包括连通管和导流端面,连通管两端分别与空心圆柱体和导流端面固接,连通管与空心圆柱体连通。本发明能够实现通过喷注二次流在主流燃气与导流器之间形成的二次流剪切层,减少主流与导流器的直接接触,降低主流对导流器的高温烧蚀、冲击和工质的摩擦,提高导流器的工作寿命,进而提高膨胀偏转喷管工作可靠性。(The invention discloses an expansion deflection spray pipe active heat protection structure, which comprises a combustion chamber, wherein one end of the combustion chamber is fixedly connected with a spray pipe, the combustion chamber is communicated with the spray pipe, a hollow cylinder is arranged in the combustion chamber, one end of the hollow cylinder is fixedly connected with the combustion chamber, the other end of the hollow cylinder is fixedly connected with a fluid director, the hollow cylinder is communicated with the fluid director, and the fluid director is positioned in the spray pipe; the fluid director comprises a communicating pipe and a flow guiding end face, two ends of the communicating pipe are fixedly connected with the hollow cylinder and the flow guiding end face respectively, and the communicating pipe is communicated with the hollow cylinder. The invention can realize the secondary flow shear layer formed between the main flow gas and the fluid director by injecting the secondary flow, reduce the direct contact between the main flow and the fluid director, reduce the high-temperature ablation, impact and working medium friction of the main flow to the fluid director, prolong the service life of the fluid director and further improve the working reliability of the expansion deflection spray pipe.)

1. An expansion deflection spray pipe active thermal protection structure comprises a combustion chamber (1), wherein one end of the combustion chamber (1) is fixedly connected with a spray pipe (2), the combustion chamber (1) is communicated with the spray pipe (2),

a hollow cylinder (3) is arranged in the combustion chamber (1), one end of the hollow cylinder (3) is fixedly connected with the combustion chamber (1), the other end of the hollow cylinder (3) is fixedly connected with a fluid director, the hollow cylinder (3) is communicated with the fluid director, and the fluid director is positioned in the spray pipe (2);

the fluid director comprises a communicating pipe (4) and a flow guide end face (5), two ends of the communicating pipe (4) are fixedly connected with the hollow cylinder (3) and the flow guide end face (5) respectively, and the communicating pipe (4) is communicated with the hollow cylinder (3);

the nozzle is characterized in that injection holes (6) are circumferentially formed in the communicating pipe (4), the flow guide end face (5) and the injection holes (6) are located in the nozzle (2), and the communicating pipe (4) is communicated with the nozzle (2) through the injection holes (6).

2. The expansion deflection nozzle active thermal shield structure of claim 1, wherein: the hollow cylinder (3) comprises a cylinder outer wall (301) and a hollow cavity (302) for circulating the secondary flow (7), the communicating pipe (4) comprises a communicating pipe outer wall (401) and a communicating cavity (402), the hollow cavity (302) is communicated with the communicating cavity (402), the injection hole (6) is formed in the communicating pipe outer wall (401), and the cylinder outer wall (301) is fixedly connected with the communicating pipe outer wall (401) and the combustion chamber (1) respectively.

3. The expansion deflection nozzle active thermal shield structure of claim 2, wherein: the flow guide end face (5) comprises a concave table face (501) and a convex table face (502), and the air outlet end of the injection hole (6) is arranged corresponding to the concave table face (501).

4. The expansion deflection nozzle active thermal shield structure of claim 1, wherein: the number of the injection holes (6) is multiple, and the injection holes (6) are all obliquely arranged.

5. The expansion deflection nozzle active thermal shield structure of claim 2, wherein: the aperture of the injection hole (6) is not larger than that of the communication cavity (402).

6. The expansion deflection nozzle active thermal shield structure of claim 3, wherein: the combustor (1) comprises a combustor outer wall (101) and a combustor convergent section outer wall (102), a plurality of studs (103) are fixedly connected to the end face of the combustor convergent section outer wall (102), and the combustor convergent section outer wall (102) is fixedly connected with the spray pipe (2) through the studs (103).

7. The expansion deflection nozzle active thermal shield structure of claim 6, wherein: spray tube (2) including the spray tube convergent section outer wall (201), spray tube throat outer wall (202), spray tube expansion section outer wall (203) that connect gradually, a plurality of mounting holes (204) have been seted up on spray tube convergent section outer wall (201) terminal surface, mounting hole (204) with double-screw bolt (103) correspond the setting, concave mesa (501) with protruding mesa (502) all are located in spray tube expansion section outer wall (203).

8. The expansion deflection nozzle active thermal shield structure of claim 7, wherein: a throat (9) used for passing through the secondary flow (7) and the main flow fuel gas (8) is formed between the boss surface (502) and the outer wall (202) of the throat part of the spray pipe.

9. The expansion deflection nozzle active thermal shield structure of claim 2, wherein: the outer wall (301) of the cylinder and the outer wall (401) of the communicating pipe are of an integrally formed structure.

10. The expansion deflection nozzle active thermal shield structure of claim 3, wherein: the outer wall (301) of the cylinder, the outer wall (401) of the communicating pipe, the concave table surface (501) and the convex table surface (502) are made of high-temperature-resistant materials.

Technical Field

The invention relates to the technical field of engines, in particular to an active thermal protection structure of an expansion deflection spray pipe.

Background

The nozzle is a main component of the rocket engine and is a key factor for determining the performance of the rocket engine. The high-performance jet pipe is an important way for improving the performance index of the rocket engine. In order to perform flight missions efficiently, rocket engines must produce high specific impulses, i.e., high ratios of fuel weight to thrust consumed per unit time. This is most easily achieved when the engine has a high area ratio nozzle, the area ratio being the ratio of the nozzle exit area to the throat area. However, the conventional cone/bell nozzle has a fixed geometry, so that the nozzle area ratio is fixed, the optimal working performance can be obtained only at the design height, and large thrust loss exists in a large range of flying heights, so that the further improvement of the performance of the rocket engine is limited.

The expansion deflection nozzle is a nozzle with a height compensation effect. The expansion of the gas jet flow is limited by the fluid director at the throat part of the spray pipe, and the expansion jet flow induces the atmospheric environment to automatically adjust the profile, so as to adjust the area ratio of the spray pipe. Compared with the traditional spray pipe, the expansion deflection spray pipe has the advantages of wide working height range, short length, compact structure and light weight. When the two stages of the carrier are connected, an 'embedded' design can be adopted, namely, a front seal head of the lower stage is embedded into an expansion deflection spray pipe of the upper stage, the stage section is eliminated, and the length of the carrier and the space of launching equipment are greatly saved. Due to the advantages, the NASA and the Fa-Navigneau space and aviation administration of America have long proposed an integral-grade rocket engine concept based on an expansion deflection nozzle technology, serve as a storage technology of a new-generation engine, and complete ground principle prototype development and hot test demonstration verification.

However, the expansion deflection nozzle throat flow guider can bear great temperature gradient and thermal stress in the working process, the erosion of high-temperature and high-speed airflow is required to be resisted, and meanwhile, a complex flow field structure and a complex wave system also exist. For rocket engines with high combustion temperature and working for a long time, the ablation problem of the flow guider at the throat part of the spray pipe is particularly prominent, and the problems are represented by structural size change, rough and uneven surface, irregular molded surface and the like, so that the efficiency of the spray pipe is reduced, and the engine fails to work in severe cases. At present, ablation-resistant materials and a passive method for spraying a heat-insulating coating on the surface of a throat flow guider are mainly adopted, and ablation is resisted by the performance of the materials, but the problems of large structural mass, complex process, stable long-time working performance and the like exist in the solution.

Disclosure of Invention

The invention aims to provide an active heat protection structure of an expansion deflection spray pipe, which aims to solve the problems in the prior art, can realize a secondary flow shear layer formed between main flow gas and a fluid director by injecting secondary flow, reduces the direct contact between the main flow and the fluid director, reduces the high-temperature ablation, impact and working medium friction of the main flow on the fluid director, prolongs the service life of the fluid director, and further improves the working reliability of the expansion deflection spray pipe.

In order to achieve the purpose, the invention provides the following scheme: the invention provides an expansion deflection spray pipe active heat protection structure, which comprises a combustion chamber, wherein one end of the combustion chamber is fixedly connected with a spray pipe, the combustion chamber is communicated with the spray pipe,

a hollow cylinder is arranged in the combustion chamber, one end of the hollow cylinder is fixedly connected with the combustion chamber, the other end of the hollow cylinder is fixedly connected with a fluid director, the hollow cylinder is communicated with the fluid director, and the fluid director is positioned in the spray pipe;

the fluid director comprises a communicating pipe and a flow guiding end face, two ends of the communicating pipe are fixedly connected with the hollow cylinder and the flow guiding end face respectively, and the communicating pipe is communicated with the hollow cylinder;

the injection holes are circumferentially formed in the communicating pipe, the flow guide end face and the injection holes are located in the injection pipe, and the communicating pipe is communicated with the injection pipe through the injection holes.

Preferably, the hollow cylinder comprises a cylinder outer wall and a hollow cavity for circulating the secondary flow, the communicating pipe comprises a communicating pipe outer wall and a communicating cavity, the hollow cavity is communicated with the communicating cavity, the injection hole is formed in the communicating pipe outer wall, and the cylinder outer wall is fixedly connected with the communicating pipe outer wall and the combustion chamber respectively.

Preferably, the flow guide end surface comprises a concave table surface and a convex table surface, and the air outlet end of the injection hole is arranged corresponding to the concave table surface.

Preferably, the number of the injection holes is several, and the injection holes are all obliquely arranged.

Preferably, the diameter of the injection hole is not larger than that of the communicating cavity.

Preferably, the combustion chamber comprises a combustion chamber outer wall and a combustion chamber convergence section outer wall, a plurality of studs are fixedly connected to the end face of the combustion chamber convergence section outer wall, and the combustion chamber convergence section outer wall is fixedly connected with the spray pipe through the studs.

Preferably, the spray pipe comprises a spray pipe convergence section outer wall, a spray pipe throat outer wall and a spray pipe expansion section outer wall which are sequentially connected, a plurality of mounting holes are formed in the end face of the spray pipe convergence section outer wall, the mounting holes correspond to the studs, and the concave table top and the convex table top are located in the spray pipe expansion section outer wall.

A throat for passing the secondary flow and the main flow gas is formed between the convex table surface and the outer wall of the throat part of the spray pipe.

Preferably, the outer wall of the cylinder and the outer wall of the communicating pipe are of an integrally formed structure.

Preferably, the outer wall of the cylinder, the outer wall of the communicating pipe, the concave table surface and the convex table surface are made of high-temperature resistant materials.

The invention discloses the following technical effects:

1. according to the active heat protection structure of the expansion jet pipe, a secondary flow shear layer is formed between main flow gas and the fluid director through secondary flow injected through the injection holes during working, so that direct contact between the main flow and the fluid director can be reduced, high-temperature ablation, impact and working medium friction of the main flow on the fluid director are reduced, the working life of the fluid director is prolonged, and the working reliability of the expansion deflection jet pipe is further improved;

2. the fluid director provided by the invention has a special flow-guiding end surface, and is beneficial to improving the protection effect of secondary flow on the flow-guiding end surface of the fluid director;

3. the active heat protection structure of the expansion nozzle can actively adjust the state of a secondary flow working medium according to the difference of the temperature and the components of main flow gas, and further effectively control the ablation of the main flow to a fluid director;

4. according to the active heat protection structure of the expansion nozzle, the thrust of the engine can be adjusted by changing the state of the secondary flow working medium, so that the thrust of the engine can be controlled;

5. the flow guider, the hollow cylinder and the combustion chamber provided by the invention can adopt a split threaded connection structure, have simple structure, are convenient to disassemble and replace, and can improve the use and maintenance of the expansion deflection spray pipe.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic structural view of an active thermal shield structure of an expansion deflection nozzle;

FIG. 2 is a schematic view of a combustion chamber;

FIG. 3 is a schematic structural view of the nozzle;

FIG. 4 is a schematic structural view of a hollow cylinder;

FIG. 5 is a structural schematic of a flow director;

FIG. 6 is a state diagram of the inactive thermal protection mode;

FIG. 7 is a state diagram in the active thermal protection mode;

FIG. 8 is an enlarged view of a portion of FIG. 7 at A;

the method comprises the following steps of 1-a combustion chamber, 101-a combustion chamber outer wall, 102-a combustion chamber convergence section outer wall, 103-a stud, 2-a nozzle, 201-a nozzle convergence section outer wall, 202-a nozzle throat outer wall, 203-a nozzle expansion section outer wall, 204-a mounting hole, 3-a hollow cylinder, 301-a cylinder outer wall, 302-a hollow cavity, 4-a communicating pipe, 401-a communicating pipe outer wall, 402-a communicating cavity, 5-a flow guide end face, 501-a concave table face, 502-a convex table face, 6-an injection hole, 7-a secondary flow, 8-a main flow gas, 9-a throat and 10-a nut.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.

The invention provides an expansion deflection spray pipe active heat protection structure, which comprises a combustion chamber 1, wherein one end of the combustion chamber 1 is fixedly connected with a spray pipe 2, the combustion chamber 1 is communicated with the spray pipe 2, a hollow cylinder 3 is arranged in the combustion chamber 1, one end of the hollow cylinder 3 is fixedly connected with the combustion chamber 1, the other end of the hollow cylinder 3 is fixedly connected with a fluid director, the hollow cylinder 3 is communicated with the fluid director, and the fluid director is positioned in the spray pipe 2; the fluid director comprises a communicating pipe 4 and a fluid-directing end face 5, two ends of the communicating pipe 4 are respectively fixedly connected with the hollow cylinder 3 and the fluid-directing end face 5, and the communicating pipe 4 is communicated with the hollow cylinder 3; the injection holes 6 are circumferentially formed in the communicating pipe 4, the flow guide end face 5 and the injection holes 6 are both located in the spray pipe 2, and the communicating pipe 4 is communicated with the spray pipe 2 through the injection holes 6.

Mainstream gas 8 flows in the combustion chamber 1, when the combustor works, the mainstream gas 8 generally flows from left to right, as shown in fig. 6, the mainstream gas 8 flows in the combustion chamber 1 and then enters the spray pipe 2 under the condition that an active thermal protection mode is not adopted, and when the mainstream gas 8 enters the spray pipe 2, the mainstream gas 8 has obvious impact on the end face 5 of the fluid director and friction of working media.

As shown in fig. 7 to 8, in the active thermal protection mode, the secondary flow 7 flows in the hollow cylinder 3 and the communicating tube 4 and flows out of the injection hole 6. The secondary flow 7 of the injection forms a secondary flow shear layer between the main flow gas 8 and the flow guide end face 5, so that the direct contact between the main flow gas 8 and the flow guide end face 5 can be reduced, the high-temperature ablation, impact and working medium friction of the main flow gas 8 on the flow guide end face 5 can be reduced, the service life of the flow guider can be prolonged, and the working reliability of the expansion deflection spray pipe can be further improved. Meanwhile, according to the difference of the temperature and the components of the main stream gas 8, the state of the secondary stream 7 working medium can be actively adjusted, and further the ablation of the main stream gas 8 to the fluid director can be effectively controlled. The thrust of the engine can be adjusted by changing the state of the secondary flow 7 working medium, so that the thrust of the engine can be controlled.

According to the further optimization scheme, the hollow cylinder 3 comprises a cylinder outer wall 301 and a hollow cavity 302 for circulating the secondary flow 7, the communicating pipe 4 comprises a communicating pipe outer wall 401 and a communicating cavity 402, the hollow cavity 302 is communicated with the communicating cavity 402, the injection hole 6 is formed in the communicating pipe outer wall 401, and the cylinder outer wall 301 is fixedly connected with the communicating pipe outer wall 401 and the combustion chamber 1 respectively.

The hollow cavity 302 is used for circulating the secondary flow 7, and finally flows out of the injection hole 6 after passing through the communicating cavity 402, and one end of the cylinder outer wall 301, which is far away from the communicating pipe outer wall 401, can be fixed with the combustion chamber 1 in a welding or threaded connection mode, so that the cylinder outer wall 301 supports the communicating pipe outer wall 401 and finally supports the flow guide end face 5.

In a further optimized scheme, the flow guide end surface 5 comprises a concave table surface 501 and a convex table surface 502, and the air outlet end of the injection hole 6 is arranged corresponding to the concave table surface 501.

The height of the convex mesa 502 should be higher than that of the concave mesa 501, the concave mesa 501 is closer to the injection hole 6 than the convex mesa 502, the concave mesa 501 and the convex mesa 502 are in smooth transition, the secondary flow 7 injected from the injection hole 6 hits on the surface of the concave mesa 501 and then flows to the convex mesa 502 on the concave mesa 501, and the secondary flow 7 flows on the concave mesa 501 and the convex mesa 502 to form a secondary flow shear layer so as to protect the burning of the main flow gas 8 on the concave mesa 501 and the convex mesa 502.

According to the further optimization scheme, the plurality of injection holes 6 are arranged, and the plurality of injection holes 6 are all obliquely arranged. In order to improve the protection effect of the secondary flow 7 on the concave mesa 501 and the convex mesa 502, a plurality of injection holes 6 are arranged, the injection holes 6 are uniformly distributed, the injection holes 6 are positioned on the same vertical plane, under the active heat protection mode, the secondary flow 7 in the communicating cavity 402 is injected by the injection holes 6 and uniformly covers the concave mesa 501 and the convex mesa 502 to reduce the burning of the main flow gas 8 on the concave mesa 501 and the convex mesa 502, in addition, the injection holes 6 are obliquely arranged, so that the secondary flow 7 injected by the injection holes 6 can impact on the concave mesa 501, the obliquely injected secondary flow 7 cannot influence the normal movement of the main flow gas 8, and meanwhile, due to the existence of the main flow gas 8, when the main flow gas 8 normally moves, the secondary flow 7 can be assisted to flow on the concave mesa 501 and the convex mesa 502 to form a secondary flow shearing layer, the protection effect on the concave land 501 and the convex land 502 is improved.

In a further optimized scheme, the aperture of the injection hole 6 is not larger than that of the communication cavity 402. The aperture of the injection hole 6 should not be larger than that of the communication cavity 402, so that the flow rate of the secondary flow injected by the injection hole 6 is larger than that of the secondary flow in the communication cavity 402, thereby achieving the effect of flowing on the concave surface 501 and the convex surface 502 to form a secondary flow shear layer.

According to a further optimized scheme, the combustion chamber 1 comprises a combustion chamber outer wall 101 and a combustion chamber convergence section outer wall 102, a plurality of studs 103 are fixedly connected to the end face of the combustion chamber convergence section outer wall 102, and the combustion chamber convergence section outer wall 102 is fixedly connected with the spray pipe 2 through the studs 103. The outer wall 101 of the combustion chamber is fixedly connected with the outer wall 301 of the cylinder, fuel is combusted in the outer wall 101 of the combustion chamber to form main flow gas 8, and the main flow gas enters the outer wall 203 of the nozzle expansion section through the combustion chamber convergence section 102, the outer wall 201 of the nozzle convergence section and the outer wall 202 of the nozzle throat section, and due to the existence of the combustion chamber convergence section 102, the outer wall 201 of the nozzle convergence section and the outer wall 202 of the nozzle throat section, the flow area of the high-temperature and high-pressure main flow gas generated in the outer wall 101 of the combustion chamber is reduced, so that the power of an engine is improved. And a stud 103 is arranged on the outer wall 102 of the convergent section of the combustion chamber, so as to facilitate the installation of the nozzle 2.

Further optimization scheme, spray tube 2 has seted up a plurality of mounting holes 204 including spray tube convergent section outer wall 201, spray tube throat outer wall 202, the spray tube expansion section outer wall 203 that connects gradually on the spray tube convergent section outer wall 201 terminal surface, and mounting hole 204 corresponds the setting with double-screw bolt 103, and concave mesa 501 and protruding mesa 502 all are located spray tube expansion section outer wall 203. The mounting hole 204 passes through the stud 103 and is locked by the nut 10. The mounting holes 204 are uniformly distributed along the circumferential direction of the end face of the outer wall 201 of the convergent section of the nozzle, and the number of the mounting holes 204 is consistent with that of the studs 103.

In a further optimized scheme, a throat 9 for passing the secondary flow 7 and the main flow gas 8 is formed between the boss surface 502 and the outer wall 202 of the throat of the nozzle. The intersection of the outer wall 201 of the nozzle convergent section and the outer wall 203 of the nozzle divergent section is the outer wall 202 of the nozzle throat, the boss surface 502 and the outer wall 202 of the nozzle throat form a throat 9, and the main stream gas 8 and the secondary stream 7 enter the nozzle 2 through the throat 9 to complete the normal power supply effect.

Further optimize the scheme, cylinder outer wall 301 is the integrated into one piece structure with communicating pipe outer wall 401. Cylinder outer wall 301 and communicating pipe outer wall 401 can be structure as an organic whole to improve the preparation efficiency and the sealed effect of work piece, and for the convenience of transportation or installation, cylinder outer wall 301 and communicating pipe outer wall 401 also can be for the components of a whole that can function independently structure, and the mode through welding or threaded connection is fixed, and two kinds of connected modes are selected according to actual conditions, do not do too much here and describe repeatedly.

Further optimizing scheme, cylinder outer wall 301, communicating pipe outer wall 401, concave mesa 501, convex mesa 502 all adopt high temperature resistant material. In order to improve the burning resistance of the protective structure, the outer wall 301 of the cylinder, the outer wall 401 of the communicating pipe, the concave mesa 501 and the convex mesa 502 can be made of high-temperature resistant materials such as tungsten copper infiltrated and carbon-carbon. The outer wall 301 of the cylinder, the outer wall 401 of the communicating pipe, the concave surface 501 and the convex surface 502 can be made of the same material or different materials, and the materials are determined according to the use condition.

Working principle;

in the active thermal protection mode, fuel is combusted in the outer wall 101 of the combustion chamber to form high-temperature high-pressure gas, then the high-temperature high-pressure gas passes through the combustion chamber convergence section 102 and the nozzle convergence section outer wall 201, the nozzle throat outer wall 202 enters the nozzle expansion section outer wall 203, and at the moment, the secondary flow 7 flows in the hollow cylinder 3 and the communicating pipe 4 and flows out of the injection hole 6. The secondary flow 7 is injected onto the concave mesa 501, flows to the boss surface 502 under the action of the concave and convex surface 501 and then flows to the outer wall 203 of the expansion section of the nozzle, and the secondary flow 7 forms a secondary flow shear layer between the main flow gas 8 and the concave mesa 501 and the boss surface 502, so that the direct contact of the main flow gas 8 with the concave mesa 501 and the boss surface 502 can be reduced, the high-temperature ablation, impact and working medium friction of the main flow gas 8 on the concave mesa 501 and the boss surface 502 are reduced, the service life of the fluid director is prolonged, and the working reliability of the expansion deflection nozzle is further improved. Meanwhile, according to the difference of the temperature and the components of the main stream gas 8, the state of the secondary stream 7 working medium can be actively adjusted, and further the ablation of the main stream gas 8 to the fluid director can be effectively controlled. The thrust of the engine can be adjusted by changing the state of the secondary flow 7 working medium, so that the thrust of the engine can be controlled.

In the description of the present invention, it is to be understood that the terms "longitudinal", "lateral", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like, indicate orientations or positional relationships based on those shown in the drawings, are merely for convenience of description of the present invention, and do not indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and thus, are not to be construed as limiting the present invention.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.