CN116367404A

CN116367404A - Large-scale plasma jet generation device and method

Info

Publication number: CN116367404A
Application number: CN202310479541.6A
Authority: CN
Inventors: 张若兵; 崔伟胜; 柴立
Original assignee: Shenzhen International Graduate School of Tsinghua University
Current assignee: Shenzhen International Graduate School of Tsinghua University
Priority date: 2023-04-28
Filing date: 2023-04-28
Publication date: 2023-06-30

Abstract

The device comprises a jet pipe and a jet cavity, wherein an outlet of the jet pipe is positioned in the jet cavity, the jet cavity is provided with an exhaust structure and an ambient gas inlet structure, the ambient gas inlet structure is used for introducing ambient gas into the jet cavity, working gas sprayed out of the jet pipe forms a circulation flow flowing towards the outlet of the jet pipe in the jet cavity, the ambient gas flows towards the outlet of the jet pipe under the action of the circulation flow after flowing into the jet cavity, and the gas components and flow field distribution near the outlet of the jet pipe are changed, so that a large-scale plasma jet is formed. According to the invention, the jet cavity is arranged, and the air inlet structure of the environmental gas is added in the jet cavity, so that the gas circulation is formed, the gas components near the outlet of the jet pipe are changed, and the large-scale plasma jet is formed, so that the treatment area of the plasma on the object to be treated is increased, and the application cost is reduced.

Description

Large-scale plasma jet generation device and method

Technical Field

The invention relates to the technical field of plasma jet generation, in particular to a large-scale plasma jet generation device and method.

Background

In recent years, atmospheric pressure plasma jet has become an important technology in the field of low temperature plasma applications. By placing a metal rod in the hollow glass tube as a high-voltage electrode, arranging annular metal or not (directly taking the far end as a ground electrode), and applying alternating current or pulse high voltage, a section of room-temperature plasma jet which develops outwards can be generated under the condition that working gas is rare gas. The jet realizes the spatial separation of the discharge area and the plasma treatment area in the dielectric barrier discharge (dielectric barrier discharge, DBD), directly transmits the active substances to the surface of the treated object, and is suitable for objects with various sizes and shapes. The plasma jet has the advantages of low temperature, no pollution, high efficiency, controllability and the like, and can be used for various applications such as cleaning, activating, coating, etching, functionalization and the like of the material surface. Although the plasma jet is widely focused and has achieved many results in mechanism research and application advancement, the plasma has a shrinkage tendency after being ejected from the jet pipe, and large-area uniform treatment is difficult to realize, so that the plasma is limited in practical industrial application.

The students at home and abroad have conducted related researches on a method for improving the plasma treatment area. The currently adopted method for improving the plasma treatment area mainly comprises the following aspects:

(1) And optimizing the structure of the discharge electrode. By varying the electrode shape, spacing, angle, number, etc., the distribution and direction of the plasma jet can be adjusted, thereby increasing the treatment area. For example, multiple plasma jets may be generated using a multi-needle or multi-aperture electrode, and fan-shaped or circular plasma jets may be generated using a curved or sloped electrode.

(2) And adjusting the discharge parameters. By varying the discharge voltage, frequency, duty cycle, pulse width, etc., the intensity and stability of the plasma jet and thus the treatment area can be influenced. For example, the momentum and penetration of the plasma jet may be enhanced using a high voltage or high frequency discharge, and the instability and decay of the plasma jet may be reduced using a pulsed or modulated discharge.

(3) The discharge parameters and gas composition were varied. By adjusting parameters such as discharge voltage, current, frequency, duty ratio, pulse width and the like and changing conditions such as gas types, mixing proportion, flow and the like, the characteristics such as temperature, density, active particle concentration and the like of the plasma jet can be influenced, so that the diffusion range and treatment effect of the plasma jet are changed. In general, increasing discharge energy and gas flow, and using helium or a mixture thereof, can increase the treatment area of the plasma jet.

(4) In combination with other technical means. The plasma jet treatment area can be further increased by combining with other technical means such as plasma arrays, mechanical scanning, magnetic field control, etc. For example, a plasma array can directly increase the treatment area of a plasma jet, scanning treatment of a large area of material can be achieved using mechanical scanning, and changing the shape of the plasma jet can be achieved using magnetic field control to increase the treatment area.

However, the current research still has the following defects: (1) The generation of the medium plasma jet flow needs special design, has no universality and has limited effect of improving the plasma treatment area; (2) The medium discharge parameters have larger influence on the chemical activity of the plasmas, but have limited direct effect on the plasma jet treatment area; (3) The plasma treatment area can be increased by increasing the flow of He helium, but the application cost of the plasma jet can be greatly increased; (4) The plasma array can also increase the consumption of working gas, a three-dimensional moving system is required to be added in a mechanical scanning method, and a magnetic field control method is complex in design.

There is currently no simple and reliable method of increasing the treatment area of a single plasma jet.

Disclosure of Invention

In order to solve the problem that a method for simply and reliably improving the treatment area of a single plasma jet is not available in the prior art, the invention provides a large-scale plasma jet generation device and a method.

The technical problems of the invention are solved by the following technical scheme:

the large-scale plasma jet flow generating device is characterized by comprising a jet pipe and a jet flow chamber, wherein an outlet of the jet pipe is positioned in the jet flow chamber, the jet flow chamber is provided with an exhaust structure and an ambient gas inlet structure, the ambient gas inlet structure is used for introducing ambient gas into the jet flow chamber, working gas sprayed out of the jet pipe forms a circular flow flowing towards the outlet of the jet pipe in the jet flow chamber, the ambient gas flows towards the outlet of the jet pipe under the action of the circular flow after flowing into the jet flow chamber, and the distribution of gas components and flow fields near the outlet of the jet pipe is changed, so that large-scale plasma jet flow is formed.

In some embodiments, the topography of the jet may be adjusted by varying any one or more of the following factors: the number, shape, form and location of the ambient gas inlet structures; the kind, proportion and flow rate of the ambient gas.

In some embodiments, the topography of the jet may be adjusted by varying any one or more of the following factors: a discharge electrode structure; the number, shape, form, and location of the exhaust structures; the discharge power supply outputs the rising edge, the falling edge, the pulse width and the frequency of the pulse voltage waveform; the type, proportion and flow rate of the working gas.

In some embodiments, the ambient gas may be directed from the ambient gas inlet structure to any location of the jet chamber.

In some embodiments, the ambient air intake structure may be an intake aperture or an intake tube.

In some embodiments, the venting structure communicates the interior of the jet chamber with ambient atmospheric pressure.

In some embodiments, the device further comprises a gas buffer chamber, wherein the gas buffer chamber is arranged at the inlet of the jet pipe or is connected with the inlet of the jet pipe through a gas channel, and the gas buffer chamber is provided with a rare gas inlet and a doping gas inlet; or omitting the gas buffer chamber, arranging a gas mixing pipeline long enough to be connected with the inlet of the jet pipe, and uniformly mixing rare gas and doping gas in the gas mixing pipeline and then entering the jet pipe.

In some embodiments, the dopant gas introduced into the gas buffer chamber is a single gas or a mixed gas in which gas molecules can be ionized by metastable atoms of the introduced noble gas.

In some embodiments, the volume percentage of the doping gas introduced into the gas buffer chamber is 0.1-99%; pulse voltage waveforms with rising edges and/or falling edges in micro nanosecond level are applied between electrodes of the jet pipe.

The invention also provides a large-scale plasma jet generation method, which uses the large-scale plasma jet generation device to generate large-scale plasma jet.

Compared with the prior art, the invention has the beneficial effects that:

the invention starts from a basic mechanism of plasma jet generation, on one hand, by arranging the outlet of the jet pipe in a jet cavity with an exhaust structure, a similar closed environment is formed outside the outlet of the jet pipe instead of an open jet environment, so that working gas sprayed out of the outlet of the jet pipe forms a loop air flow flowing to the outlet of the jet pipe in the closed discharge environment of the jet cavity, the concentration distribution of the working gas near the outlet of the jet pipe is changed, the problem of shrinkage of the traditional plasma jet is solved, and a dispersive plasma jet is generated; on the basis, the invention further introduces an adjusting mechanism of the components of the environmental gas, and the environmental gas is introduced into the jet flow chamber by adding the air inlet structure of the environmental gas into the jet flow chamber, and flows towards the outlet of the jet flow pipe after flowing into the jet flow chamber, so that the gas circulation is formed, the components of the gas near the outlet of the jet flow pipe are changed, a large-scale plasma jet is formed, the treatment area of the plasma when acting on an object to be treated is improved, the application cost is reduced, and the original traditional jet flow form can be maintained at the central position. The method starts from a basic mechanism of plasma jet generation, directly regulates and controls the flow field through the two aspects, and regulates the flow field surface, the diffusion trend and the gas component proportion change of the gas flowing out of the jet orifice, thereby changing the shape of the plasma jet, and improving the single plasma jet treatment area. Moreover, the invention can solve the defects of other methods for increasing the plasma treatment area (such as jet arrays), avoid using the plasma jet arrays or reduce the number of jet pipes of the plasma jet arrays, reduce the consumption of rare gas and lower the application cost. In a word, the large-scale plasma jet generating device and the large-scale plasma jet generating method provided by the invention can effectively solve the problems of small radial area and inconvenient industrial application of the existing plasma jet, and can be applied to most of application fields of traditional plasma jet, such as material surface modification, medical disinfection and sterilization, pollution treatment and the like.

Other advantages of embodiments of the present invention are further described below.

Drawings

FIG. 1 is a schematic diagram of a large scale plasma jet generation device in an embodiment of the invention;

FIG. 2 is a schematic diagram of a prior art plasma jet;

FIG. 3 is a schematic view of a plasma jet in an embodiment of the invention;

the reference numerals are as follows:

the device comprises a 1-jet pipe, a 11-ground electrode, a 12-high-voltage electrode, a 2-jet cavity, a 3-gas buffer cavity, a 4-gas inlet and a 5-gas outlet.

Detailed Description

The invention will be further described with reference to the following drawings in conjunction with the preferred embodiments. It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other.

It should be noted that, in this embodiment, the terms of left, right, upper, lower, top, bottom, etc. are merely relative terms, or refer to the normal use state of the product, and should not be considered as limiting.

The morphology of the plasma jet has a great relationship with the propagation of the ionised wave, which in turn is affected by the gas composition and charge density distribution. The traditional plasma jet is generated in an open atmosphere environment, the radial component of the gas after the gas is sprayed out of the jet pipe is very small, and a boundary line where the gas component changes sharply exists in the radial direction, and the sprayed gas flow field is difficult to effectively regulate. The method for enhancing the plasma jet flow in the prior art is to optimize the structure of the jet pipe and the like by improving the discharge voltage, and as shown in fig. 2, the effect of effectively improving the radial area of the plasma jet flow cannot be achieved by only changing the length, the strength, the shape and the like of the plasma jet flow in the axial direction.

Before the invention provides the solution to the technical problem that the radial area of the plasma jet is too small, the solution provided by the invention comprises the following steps: increasing the applied voltage of the plasma jet, increasing the jet gas flow rate, increasing the jet pipe diameter, adopting a jet pipe array and the like. However, these methods cannot essentially solve the problem because the formation mechanism of the plasma jet is not changed, and bring about many other disadvantages, which are specifically analyzed as follows:

(1) Increasing the applied voltage of the plasma jet can enhance the formation effect of the plasma jet, but because the plasma jet is still the plasma jet in the traditional form, the effect of the plasma jet is enhanced in the axial direction, and the effect of the radial plasma jet is improved only to a limited extent. In addition, increasing the voltage causes an increase in discharge power, thereby increasing power loss and decreasing efficiency.

(2) Increasing the jet gas flow rate within a certain range can enhance the plasma jet effect, however, the method is just like (1) and only enhances the axial plasma jet effect, and the radial lifting effect is limited. Furthermore, increasing the jet gas flow rate increases the noble gas consumption rate, thereby greatly increasing the application cost of the plasma jet.

(3) Increasing the plasma jet effect by increasing the jet tube diameter requires a higher applied voltage and a larger gas consumption, thereby bringing about the disadvantages of the first two methods (1) and (2).

(4) Increasing the treatment area of the plasma jet by means of the jet array also increases the loss rate of rare gas and increases the application cost of the plasma jet. In addition, the problems of discharge coupling, rejection and the like existing between jet array units of the plasma jet are also required to be solved.

In order to solve the problems of smaller radial area of the existing plasma jet and inconvenient industrial application, the invention provides a large-area plasma jet generating device and method which utilize environmental gas modulation in a closed space; the embodiment of the device is shown in fig. 1, and comprises a jet pipe 1 and a jet flow chamber 2, wherein an outlet of the jet pipe 1 is positioned in the jet flow chamber 2, the jet flow chamber 2 is provided with an exhaust structure and an ambient gas inlet structure, the ambient gas inlet structure is used for introducing ambient gas into the jet flow chamber 2, working gas sprayed by the jet pipe 1 forms a circular flow flowing towards the outlet of the jet pipe 1 in the jet flow chamber 2, and the ambient gas flows towards the outlet of the jet pipe 1 under the action of the circular flow after flowing into the jet flow chamber 2, so that the distribution of gas components and flow fields near the outlet of the jet pipe 1 is changed, and a large-scale plasma jet is formed.

According to the invention, the environment gas is additionally introduced into the jet cavity enclosed space, so that the radial propagation component of the ionization wave is increased by changing the gas flow field distribution, the working gas diffusion trend, the gas component proportion change and the like in the enclosed space, and the radial area of the plasma jet is effectively increased on the premise of not increasing the working gas loss. The device and the method can greatly improve the radial treatment area of a single plasma jet, and have important significance for future industrialized application of the plasma jet.

In addition, the invention can solve the defect of the method for increasing the plasma treatment area in the prior art (such as adopting a jet array in the prior art), and can avoid using the plasma jet array or reduce the number of jet pipes of the plasma jet array, thereby reducing rare gas loss and reducing the application cost of the plasma jet.

Compared with the prior art, the invention has the outstanding advantages that single-tube large-area plasma jet can be realized through flow field modulation under the conditions of not increasing the electrode applied voltage, not increasing the gas flow rate, not increasing the jet pipe diameter and not adopting the jet pipe array. Therefore, the defects of application and popularization of the other modes are avoided, the industrial application of the plasma jet is facilitated, and the electrode structure can be implemented in any traditional electrode structure capable of generating the plasma jet.

As shown in fig. 1, in a specific embodiment, the large-scale plasma jet generating device comprises a jet chamber 2 and a gas buffer chamber 3, which are communicated through a jet pipe 1. The gas buffer chamber 3 is located at the inlet of the jet pipe 1, or the gas buffer chamber 3 is connected with the inlet of the jet pipe 1 through a gas channel. The gas buffer chamber 3 is provided with two gas inlets 4, a noble gas inlet and a dopant gas inlet, respectively. The rare gas introduced into the gas buffer chamber 3 is helium, the doping gas introduced into the gas buffer chamber 3 can be any other gas which can be ionized by metastable helium atoms of the introduced rare gas except helium, such as air, nitrogen, oxygen and the like, and the gas types and the proportion are not limited; the mixed gas of the rare gas and the dopant gas is a working gas. The gas buffer chamber 3 is used to provide a buffer space for the working gas so that the rare gas is sufficiently mixed with the dopant gas. In addition, the gas buffer chamber can also be connected with the inlet of the jet pipe 1 through a gas channel instead of being directly arranged at the inlet of the jet pipe 1, or the gas buffer chamber can also be omitted, a gas mixing pipeline with enough length is arranged to be connected with the inlet of the jet pipe, and rare gas and doping gas enter the jet pipe 1 after being uniformly mixed in the gas mixing pipeline.

The outlet of the jet pipe 1 is positioned in the approximately closed jet cavity 2, a circular ring type exhaust port 5 is arranged on the side wall of the jet cavity 2 opposite to the jet pipe 1, and the center of the circular ring type exhaust port 5 is positioned on the axis of the jet pipe 1. The exhaust port 5 communicates the interior of the jet chamber 2 with the external atmosphere for gas evacuation and maintains the gas pressure in the jet chamber 2 at atmospheric pressure.

The side wall of the jet flow chamber 2 at the rear side of the jet pipe 1 is provided with an air inlet 4 of ambient gas, and the air inlet 4 of the ambient gas can be in the form of an air inlet hole or an air inlet pipe and is used for adjusting the ambient gas components in the jet flow chamber 2 so as to adjust the formation morphology of the plasma jet flow. As shown in fig. 1, the dashed line at the outlet of the inlet 4 for ambient gas is the flow field distribution of the ambient gas.

Wherein the volume percentage of the doping gas introduced into the gas buffer chamber 3 is 0.1-99%, and the flow rate of the ambient gas is less than or equal to the flow rate of the working gas. The ambient gas inlet rate is not limited, any change of the flow field at the outlet end of the jet pipe caused by increasing or reducing the flow velocity of the ambient gas is achieved, a pulse voltage (or other pulse voltage waveforms with rising edges, falling edges, pulse widths, frequency and the like in the micro-nanosecond level) in the micro-nanosecond level is applied between the ground electrode 11 and the high-voltage electrode 12 of the jet pipe, when the breakdown voltage is reached, a large-area plasma jet can be formed at the outlet of the jet pipe 1, and a dotted line at the outlet of the jet pipe 1 is the flow field distribution of the working gas as shown in fig. 1.

The principle of large area plasma jet generation is as follows:

when the working gas is ejected from the jet pipe 1 to the jet cavity 2, the jet cavity 2 is an approximately closed environment, and the ejected working gas forms a gas loop in the closed space, which is shown by a dotted line at the outlet of the jet pipe 1 in fig. 1. The working gas ejected from the jet pipe 1 has a radial propagation component in addition to the axial propagation, and generates a dispersed plasma jet. Meanwhile, the air inlet 4 of the ambient air introduces the ambient air into the jet flow chamber 2, and the ambient air flows into the jet flow chamber 2 and then flows towards the outlet of the jet flow pipe due to the fact that the flow speed is high and the pressure is low at the outlet of the jet flow pipe 1. In the vicinity of the outlet of the jet pipe 1, since the sprayed working gas is affected by dilution of the ambient gas, there is a tendency that the helium component decreases in the radial direction, and there is no sharp change in the boundary. The gas component in the closed space is simultaneously influenced by the comprehensive influence of the working gas and the environmental gas sprayed by the jet pipe, so that the original traditional jet flow form can be maintained at the central position while a dispersive plasma jet flow is formed, the regulation of the generation form of the plasma jet flow is realized, and conditions are provided for large-area plasma generation.

In addition, the exhaust port 5 can be used for exhausting redundant gas in the discharge cavity, so that helium component in the ambient gas in the jet cavity is always smaller than that in the working gas, and dynamic balance is maintained.

The embodiment of the invention also provides a large-scale plasma jet generation method, which can realize large-area uniform treatment on the premise of not increasing the consumption cost of working gas and the power of a power supply and has important value in future industrial large-scale application.

The embodiment of the invention starts from a basic mechanism of plasma jet generation, and adjusts the flow field distribution, diffusion trend and gas component proportion change at the outlet of the gas outflow jet pipe by directly adjusting and controlling the flow field, thereby changing the shape of the plasma jet in the radial direction. According to the embodiment of the invention, on the basis of generating the dispersive plasma jet by utilizing the jet cavity enclosed space, an adjusting mechanism of the ambient gas component is introduced, and the generated large-scale plasma jet is shown in fig. 3, so that the original traditional jet form can be maintained at the central position while the dispersive plasma jet is formed, and the large-scale plasma jet generating method has the effect of effectively improving the plasma treatment area.

In various embodiments, the flow field distribution and morphology of the plasma jet may be adjusted by varying any one or more of the following factors: the number, shape, form, and location of the inlets for introducing ambient gas into the jet chamber; the number of the air inlets can be changed from 1 to N, and the upper limit of the number is not set; the structure of the air inlet can adopt an air inlet, and the shape of the air inlet can be changed from a ring shape to any shape such as a round shape, a square shape, a porous shape and the like; the air inlet can be changed into any tubular air inlet pipe which extends into any position in the closed cavity, so that the air flow field outside the outlet of the jet pipe can be flexibly adjusted; the air inlet hole can be transferred to any position of the closed jet cavity from the side wall of the jet cavity which is right opposite to the jet pipe, so that the flow field distribution of working gas flowing out of the jet pipe orifice is directly changed. The types, flow rates and the like of the introduced ambient gas are not limited, and any gas flow field and gas components in the closed cavity are changed through the ambient gas through an additional air inlet except the working gas, so that the shape of the plasma jet flow is adjusted.

Based on the modulation of the environmental gas, the shape of the plasma jet can be regulated by the parameters such as the rising edge, the falling edge, the pulse width, the frequency and the like of the pulse voltage waveform output by the discharge power supply, and the parameters of the discharge power supply are not limited.

The method for generating the large-area passive plasma jet by adjusting the flow field and the components in the closed space through the environmental gas provided by the embodiment of the invention does not limit the shape of the jet chamber and the gas buffer chamber and the electrode structure of the jet pipe, and only the change of the flow field and the components in the closed space to the shape of the plasma jet through the environmental gas is within the scope of the protection of the embodiment of the invention.

Compared with the prior art, the invention starts from a basic mechanism of plasma jet generation, on one hand, the outlet of the jet pipe is arranged in the jet cavity with the exhaust structure, and an approximately closed environment rather than an open jet environment is formed outside the outlet of the jet pipe, so that working gas sprayed out of the outlet of the jet pipe forms a loop air flow flowing to the outlet of the jet pipe in the closed discharge environment of the jet cavity, the concentration distribution of the working gas near the outlet of the jet pipe is changed, the problem of shrinkage of the traditional plasma jet is solved, and a dispersive plasma jet is generated; on the basis, the invention further introduces an adjusting mechanism of the components of the environmental gas, and the environmental gas is introduced into the jet flow chamber by adding the air inlet structure of the environmental gas into the jet flow chamber, and flows towards the outlet of the jet flow pipe after flowing into the jet flow chamber, so that the gas circulation is formed, the components of the gas near the outlet of the jet flow pipe are changed, a large-scale plasma jet is formed, the treatment area of the plasma when acting on an object to be treated is improved, the application cost is reduced, and the original traditional jet flow form can be maintained at the central position. The method starts from a basic mechanism of plasma jet generation, directly regulates and controls the flow field through the two aspects, and regulates the flow field surface, the diffusion trend and the gas component proportion change of the gas flowing out of the jet orifice, thereby changing the shape of the plasma jet, and improving the single plasma treatment area. Moreover, the invention can solve the defects of other methods for increasing the plasma treatment area (such as jet arrays), avoid using the plasma jet arrays or reduce the number of jet pipes of the plasma jet arrays, reduce the consumption of rare gas and lower the application cost. In a word, the large-scale plasma jet generating device and the large-scale plasma jet generating method provided by the invention can effectively solve the problems of small radial area and inconvenient industrial application of the existing plasma jet, and can be applied to most of application fields of traditional plasma jet, such as material surface modification, medical disinfection and sterilization, pollution treatment and the like.

The foregoing is a further detailed description of the invention in connection with specific/preferred embodiments, and it is not intended that the invention be limited to such description. It will be apparent to those skilled in the art that several alternatives or modifications can be made to the described embodiments without departing from the spirit of the invention, and these alternatives or modifications should be considered to be within the scope of the invention. In the description of the present specification, reference to the terms "one embodiment," "some embodiments," "preferred embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Those skilled in the art may combine and combine the features of the different embodiments or examples described in this specification and of the different embodiments or examples without contradiction. Although embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the scope of the invention as defined by the appended claims.

Claims

1. The large-scale plasma jet flow generating device is characterized by comprising a jet pipe and a jet flow chamber, wherein an outlet of the jet pipe is positioned in the jet flow chamber, the jet flow chamber is provided with an exhaust structure and an ambient gas inlet structure, the ambient gas inlet structure is used for introducing ambient gas into the jet flow chamber, working gas sprayed out of the jet pipe forms a circular flow flowing towards the outlet of the jet pipe in the jet flow chamber, the ambient gas flows towards the outlet of the jet pipe under the action of the circular flow after flowing into the jet flow chamber, and the distribution of gas components and flow fields near the outlet of the jet pipe is changed, so that large-scale plasma jet flow is formed.

2. A large scale plasma jet generating device according to claim 1, wherein the morphology of the jet is adjustable by varying any one or more of the following factors: the number, shape, form and location of the ambient gas inlet structures; the kind, proportion and flow rate of the ambient gas.

3. A large scale plasma jet generating device according to claim 1, wherein the morphology of the jet is adjustable by varying any one or more of the following factors: a discharge electrode structure; the number, shape, form, and location of the exhaust structures; the discharge power supply outputs the rising edge, the falling edge, the pulse width and the frequency of the pulse voltage waveform; the type, proportion and flow rate of the working gas.

4. The large scale plasma jet generating apparatus of claim 1, wherein the ambient gas may be introduced from the ambient gas inlet structure to any location of the jet chamber.

5. The large scale plasma jet generating apparatus of claim 1, wherein the ambient gas inlet structure may be an inlet aperture or an inlet duct.

6. The large scale plasma jet generating apparatus of claim 1, wherein the exhaust structure communicates the jet chamber interior with ambient atmospheric pressure.

7. The large scale plasma jet generating apparatus of claim 1, further comprising a gas buffer chamber disposed at or connected to the inlet of the jet pipe by a gas channel, the gas buffer chamber being provided with a noble gas inlet and a dopant gas inlet; or omitting the gas buffer chamber, arranging a gas mixing pipeline long enough to be connected with the inlet of the jet pipe, and uniformly mixing rare gas and doping gas in the gas mixing pipeline and then entering the jet pipe.

8. The large scale plasma jet generating apparatus of claim 7, wherein the dopant gas introduced into the gas buffer chamber is a single gas or a mixed gas of which gas molecules can be ionized by metastable atoms of the introduced noble gas.

9. The large-scale plasma jet generating device according to claim 1, wherein the volume percentage of the doping gas introduced into the gas buffer chamber is 0.1-99%; pulse voltage waveforms with rising edges and/or falling edges in micro nanosecond level are applied between electrodes of the jet pipe.

10. A method of generating a large-scale plasma jet, characterized in that a large-scale plasma jet is generated using a large-scale plasma jet generating device as claimed in any one of claims 1 to 9.