A microwave cavity high-efficiency heating device and a heating method thereof

Abstract

The present application relates to the technical fields of microwave heating, and particularly relates to a microwave cavity high-efficiency heating device and a heating method thereof. The microwave cavity high-efficiency heating device comprises a heating cavity, a straight-wall waveguide with asymmetric transmission function in communication with the heating cavity, and at least one set of unidirectional waveguide structure, the unidirectional waveguide structure is attached to the inner side wall of the straight-wall waveguide; the unidirectional waveguide structure comprises a first dielectric segment and a second dielectric segment arranged in sequence along the microwave transmission direction, the dielectric constant of the first dielectric segment gradually increases along the microwave transmission direction and the maximum value is ε max , the dielectric constant of the second dielectric segment is a stable value ε0, and ε max = ε0. The microwave cavity high-efficiency heating device has simple structure, can improve the microwave energy utilization rate in different states, effectively solve the microwave reflection problem, prolong the service life of the microwave source, reduce the use of circulator and other protection devices, reduce the equipment cost, and improve the safety of microwave heating.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microwave heating technology, and in particular to a high-efficiency heating device in a microwave cavity and a heating method thereof. BACKGROUND

[0002] As a new type of clean energy, microwave energy has the characteristics of high efficiency, energy saving, selective heating, and clean and pollution-free, and is widely used in food processing, chemical industry, medicine and other fields. Especially in the two high-energy-consuming industries of chemical industry and metallurgy, the application of microwaves has shown obvious advantages in energy saving and emission reduction. Compared with traditional heat sources, microwave heating has the characteristics of high efficiency, large power, good controllability, and selective heating. Microwave multi-mode cavities are widely used, and have the advantages of large capacity and good heating uniformity compared with microwave single-mode heating cavities. However, due to the different shapes, volumes and dielectric constants of the heated objects, the efficiency of microwave heating is also different, and the existing microwave multi-mode heating cavities are difficult to adapt to the high-efficiency heating of various loads.

[0003] At the same time, in the heating process of the microwave multi-mode cavity, the microwave cannot be matched for transmission, resulting in that the energy output by the microwave source cannot be fully absorbed by the load, causing energy waste. In addition, in the high-power industrial application of microwave energy, industrial materials as high-power microwave loads are typical complex time-varying non-uniform media, and their absorption / reflection ability of microwaves will change dramatically with time and temperature. Intense microwave reflection is disastrous to high-power systems, not only wasting a lot of energy, but also easily burning out microwave devices, so the efficient use of microwave power in different states and the prevention of microwave source damage by reflected power are the prerequisites for the efficient and stable application of high-power microwave heating systems.

[0004] In view of the low heating efficiency and the existence of microwave reflection in the microwave heating process, the existing technology generally uses a circulator and a water load to absorb the reflected microwaves to prevent the reflected microwave energy from damaging the microwave source. For example, a microwave reaction device with reflection protection disclosed in Chinese Patent Publication No. CN112569885B can efficiently absorb reflected microwaves, protect the microwave source, make the use safer, and prolong the service life of the equipment. However, the above-mentioned microwave reaction device also has certain defects. For example, the circulator is a ferrite device, which introduces additional insertion loss to the system during use. When the device works in a high-power continuous wave state, the power consumed will continuously convert into heat, causing the temperature of the device to rise, and even completely losing the isolation effect. Therefore, the performance of such a device is subject to the working temperature and power, and the reflected power is absorbed by the water load, causing serious energy waste. At the same time, the existing technology also uses a three-pin tuner to improve the heating efficiency of microwaves, but using a three-pin to enhance efficiency requires real-time adjustment of the pin during the entire heating process, and the three-pin tuner has a matching blind area and is expensive. Some three-pin microwave heating devices with intelligent tuning function also have certain deficiencies, such as: (1) the reflection power easily increases during the tuning process, and the tuning time is too long, which easily causes damage to the microwave source; (2) the three-pin tuning has a matching blind area; (3) the automatic tuning of the three-pin requires additional introduction of a series of modules such as a complex reflection coefficient measuring device, an operation circuit, a stepping motor, which is expensive and reduces the stability of the system.

[0005] However, the above technical solutions do not actually and perfectly solve the problems of low heating efficiency and microwave reflection in the microwave heating process. Therefore, large-scale application of microwave energy urgently needs a device that is more convenient and can improve the utilization rate of microwave energy in different states. SUMMARY

[0006] To solve the above technical problems, the purpose of the present application is to provide a microwave cavity high-efficiency heating device and a heating method thereof. The microwave cavity high-efficiency heating device has a simple structure, can improve the utilization rate of microwave energy in different states, effectively solve the problem of microwave reflection, prolong the service life of the microwave source, reduce the use of protection devices such as circulators, reduce the cost of equipment, and improve the safety of microwave heating.

[0007] To achieve the above technical effects, the present application adopts the following technical solutions:

[0008] The application discloses a microwave cavity high-efficiency heating device, which comprises a heating cavity, a straight-wall waveguide with an asymmetric transmission function and at least one set of unidirectional waveguide structures. max max

[0009] Further, the unidirectional waveguide structure is provided with two sets and is arranged on two opposite inner side walls of the straight-wall waveguide, preferably, the electromagnetic wave transmitted by the straight-wall waveguide is a TE wave.

[0010] Further, the unidirectional waveguide structure is provided with one set and is fixedly arranged on any one inner side wall of the straight-wall waveguide.

[0011] Further, the unidirectional waveguide structure is provided with four sets and is arranged on four inner side walls of the straight-wall waveguide.

[0012] Further, the unidirectional waveguide structure can be adhered or embedded on the inner side wall of the straight-wall waveguide.

[0013] Further, the cross section of the straight-wall waveguide is in a rectangular structure.

[0014] Further, the first end of the second dielectric segment is tightly connected with the tail end of the first dielectric segment, or the second dielectric segment and the first dielectric segment are in an integrated structure.

[0015] Further, the tail end of the second dielectric segment protrudes from the straight-wall waveguide and partially extends into the interior of the heating cavity.

[0016] Further, the tail end of the second dielectric segment partially extends into the interior of the heating cavity, and the length of the second dielectric segment extending into the heating cavity is less than 1 / 2 of the length of the heating cavity, preferably 1 / 10-2 / 5 of the length of the heating cavity.

[0017] Further, the height of the unidirectional waveguide structure is greater than or equal to 2 / 3 of the height of the inner wall of the straight-wall waveguide to which the unidirectional waveguide structure is attached, and the maximum height of the unidirectional waveguide structure is equal to the height of the inner wall of the straight-wall waveguide.

[0018] Further, the thickness of the second dielectric segment is equal to the maximum thickness of the first dielectric segment.

[0019] ​​Further, one side outer surface of the first medium section is provided with a groove group, the groove group comprises a plurality of longitudinal grooves arranged in parallel from the head end to the tail end of the first medium section, and the depth of the longitudinal grooves gradually decreases from the head end to the tail end of the first medium section, preferably, the cross section of the longitudinal grooves is rectangular.

[0020] Further, the thickness of the first medium section gradually increases from the head end to the tail end of the first medium section.

[0021] Further, the inside of the first medium section is provided with a medium hole group, the medium hole group comprises a plurality of longitudinal medium holes arranged in sequence from the head end to the tail end of the first medium section, the inside of the medium hole is provided with a filling medium, the cross section of the medium hole is circular, and the hole diameter of the medium hole gradually increases or decreases from the head end to the tail end of the first medium section, specifically, the filling medium can be air or other material with dielectric constant greater than or less than air.

[0022] Further, the heating cavity is also provided with a tray for placing the object to be heated.

[0023] In the second aspect, the application further provides a microwave cavity high-efficiency heating method, which heats the object to be heated by using the microwave cavity high-efficiency heating device.

[0024] Compared with the prior art, the application has the following beneficial effects:

[0025] The microwave cavity high-efficiency heating device and the heating method provided by the application can realize high-efficiency heating of the object to be heated in the heating cavity by arranging at least one group of unidirectional waveguide structures on the inner side wall of the straight-wall waveguide for transmitting electromagnetic waves, converting electromagnetic waves into surface waves by the unidirectional waveguide structures and transmitting the surface waves unidirectionally into the heating cavity, thereby effectively solving the problems of microwave reflection and low heating efficiency, improving the microwave heating efficiency and safety. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 The application provides a microwave cavity high-efficiency heating device and a heating method thereof.

[0027] Figure 2A longitudinal cross-sectional view of a high-efficiency microwave cavity heating device provided in Embodiment 1 of the present invention;

[0028] Figure 3 This is a schematic diagram of a configuration of the first dielectric section of a microwave cavity high-efficiency heating device according to Embodiment 1 of the present invention.

[0029] Figure 4 This is a schematic diagram of a second configuration of the first dielectric section of a microwave cavity high-efficiency heating device according to Embodiment 1 of the present invention.

[0030] Figure 5 This is a schematic diagram of a third configuration of the first dielectric section of a microwave cavity high-efficiency heating device according to Embodiment 1 of the present invention;

[0031] Figure 6 A longitudinal cross-sectional view of a high-efficiency microwave cavity heating device provided in Embodiment 2 of the present invention;

[0032] Figure 7 Simulation test results of a microwave cavity high-efficiency heating device and heating method provided in Embodiment 3 of the present invention;

[0033] The attached figures are labeled as follows: 10, heating cavity; 20, straight-walled waveguide; 30, unidirectional waveguide structure; 31, first dielectric section; 32, second dielectric section; 40, tray; 41, object to be heated; 51, longitudinal groove; 52, dielectric hole. Detailed Implementation

[0034] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention.

[0035] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," "x-direction," "y-direction," and "z-direction" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0036] It should be particularly pointed out that the terms "head end" and "tail end" in the present application are both referenced to the microwave transmission direction, and the "head end" refers to the direction close to the microwave transmission direction, while the "tail end" refers to the direction to which the microwave is transmitted.

[0037] Embodiment 1

[0038] As Figures 1-2 shown, the present embodiment is the first embodiment of the present application, and the present embodiment provides a microwave cavity high-efficiency heating device, which comprises a heating cavity 10, a straight-wall waveguide 20 with asymmetric transmission function in communication with the heating cavity 10, and two groups of unidirectional waveguide structures 30. Specifically, the straight-wall waveguide 20 is used for transmitting TE waves, and the cross section of the straight-wall waveguide 20 is in a rectangular structure, and the two groups of unidirectional waveguide structures 30 are respectively arranged on two opposite inner side walls of the straight-wall waveguide 20, and each group of unidirectional waveguide structures 30 comprises a first dielectric segment 31 and a second dielectric segment 32 arranged in sequence along the microwave transmission direction, the dielectric constant of the first dielectric segment 31 gradually increases along the microwave transmission direction and the maximum value is ε max , the second dielectric segment 32 has a stable dielectric constant ε max 0, and ε max 0.

[0039] In the present embodiment, the unidirectional waveguide structure 30 can be bonded or embedded on the inner side wall of the straight-wall waveguide 20, so that the unidirectional waveguide structure 30 is attached to the inner side wall of the straight-wall waveguide 20, and the first dielectric segment 31 and the second dielectric segment 32 are both in a plate or sheet structure, and at the same time, the head end of the second dielectric segment 32 is in close contact with the tail end of the first dielectric segment 31, and the thickness of the second dielectric segment 32 is equal to the maximum thickness of the first dielectric segment 31. In addition, the end of the second dielectric segment 32 protrudes from the straight-wall waveguide 20 and extends into the interior of the heating cavity 10, and the end portion of the second dielectric segment 32 extends into the interior of the heating cavity 10, and the length of the portion of the second dielectric segment 32 extending into the heating cavity 10 is 1 / 3 of the length of the heating cavity 10, and the height of the unidirectional waveguide structure 30 is equal to the height of the inner wall of the straight-wall waveguide 20.

[0040] In the present embodiment, in order to realize the gradual change of the dielectric constant of the first dielectric segment 31, the first dielectric segment 31 can be designed and constructed by any one of the following modes, specifically including:

[0041] Mode one:

[0042] As shown in the accompanying Figure 3As shown, the outer surface of one side of the first dielectric segment 31 is provided with a groove group, which includes a plurality of longitudinal grooves 51 arranged in parallel from the head end to the tail end of the first dielectric segment 31, and the longitudinal grooves 51 are equidistantly arranged, and the depth of the longitudinal grooves 51 gradually decreases from the head end to the tail end of the first dielectric segment 31, and the cross section of the longitudinal grooves 51 is all rectangular.

[0043] Mode two:

[0044] As shown in the accompanying drawings Figure 4 As shown, the thickness of the first dielectric segment 31 gradually increases from the head end to the tail end of the first dielectric segment 31, so that the dielectric constant of the first dielectric segment 31 gradually changes, and the dielectric constant of the first dielectric segment 31 gradually increases from the head end to the tail end of the first dielectric segment 31.

[0045] Mode three:

[0046] As shown in the accompanying drawings Figure 5 As shown, the inside of the first dielectric segment 31 is provided with a dielectric hole group, which includes a plurality of longitudinal dielectric holes 52 arranged in sequence from the head end to the tail end of the first dielectric segment 31, the dielectric hole 52 penetrates the first dielectric segment 31 in the longitudinal direction, and the inside of the dielectric hole 52 is filled with a filling medium. Specifically, in order to realize that the dielectric constant of the first dielectric segment 31 gradually increases from the head end to the tail end of the first dielectric plate, the cross section of the dielectric hole 52 is circular, and the aperture of the dielectric hole 52 gradually increases from the head end to the tail end of the first dielectric segment 31, and the dielectric constant of the filling medium filled in the dielectric hole 52 is greater than the dielectric constant of the material of the first dielectric segment 31, so that the dielectric constant of the first dielectric segment 31 gradually increases from the head end to the tail end of the first dielectric segment 31, and in order to make ε0=ε max , the first dielectric segment 31 and the second dielectric segment 32 can be made of different materials. Conversely, when the dielectric constant of the filling medium filled in the dielectric hole 52 is less than the dielectric constant of the material of the first dielectric segment 31, the diameter of the dielectric hole 52 constituting the dielectric hole group gradually decreases from the head end to the tail end of the first dielectric segment 31, thereby realizing that the dielectric constant of the first dielectric segment 31 gradually increases from the head end to the tail end of the first dielectric plate, at this time, the first dielectric segment 31 and the second dielectric segment 32 can be made of the same or different materials, and make ε0=ε max .

[0047] In addition, the microwave cavity high-efficiency heating device provided by the embodiment is provided with a tray 40 for placing the object to be heated 41 in the heating cavity 10, and the tray 40 is movably or fixedly connected with the heating cavity 10, so as to facilitate the adjustment of the position of the object to be heated 41, thereby realizing the high-efficiency heating of the object to be heated 41.

[0048] In this embodiment, by attaching a first dielectric segment 31 and a second dielectric segment 32 to the two opposing inner walls of the straight-walled waveguide 20, the electromagnetic wave experiences a phase abrupt change when encountering the first dielectric segment 31. This abrupt phase change is continuous in the interface direction. The electromagnetic wave gradually transforms into a surface wave after passing through this meta-interface material multiple times, thus achieving unidirectional propagation of the electromagnetic wave and effectively solving the problem of electromagnetic wave reflection. Simultaneously, addressing the issue of surface waves being difficult to radiate into the air from the first dielectric segment 31, this invention further designs a second dielectric segment 32. This second dielectric segment 32 serves as a radiating antenna, radiating microwave energy into the heating cavity 10, thereby achieving efficient microwave heating of the object 41 to be heated within the heating cavity 10.

[0049] Example 2

[0050] like Figure 6 As shown, this embodiment is the second embodiment of the present invention. This embodiment provides a high-efficiency microwave cavity heating device, including a heating cavity 10, a straight-walled waveguide 20 with one end connected to the heating cavity 10, and two sets of unidirectional waveguide structures 30. The difference between this embodiment and embodiment 1 is that the second dielectric segment 32 and the first dielectric segment 31 are an integral structure and made of the same material. The dielectric constant of the first dielectric segment 31 gradually increases along the microwave transmission direction and has a maximum value of ε. max The second dielectric segment 32 has a stable dielectric constant ε0, and ε max =ε0.

[0051] Example 3

[0052] This embodiment is the third embodiment of the present invention, and is an application embodiment of the present invention, as detailed below:

[0053] In this embodiment, the heating effect of the microwave cavity high-efficiency heating device provided in Embodiment 1 on the object to be heated 41 was tested by simulation. The real part of the dielectric constant of the object to be heated 41 is 20 to 100, the step size interval is 10, and the loss angle is 0.2 and remains unchanged. The object to be heated is a tall cylinder with a height of 50 mm and radii of 20 mm, 25 mm and 30 mm, and a cuboid with a height of 50 mm and base areas of 30 mm*30 mm, 40 mm*40 mm and 50 mm*50 mm, respectively.

[0054] The experimental results used S11 to evaluate the microwave heating efficiency. The simulation test results are shown in Table 1 and Appendix. Figure 7 As shown.

[0055] Table 1 shows the simulation test results of a high-efficiency microwave cavity heating device provided in Example 1.

[0056]

[0057] In the table 1, S11(1) represents the heating effect of the heating device without the first medium section 31 and the second medium section 32, S11(2) represents the heating effect of the heating device with only the first medium section 31 without the second medium section 32, and S11(3) represents the heating effect of the heating device with both the first medium section 31 and the second medium section 32.

[0058] Embodiment 4

[0059] The present embodiment is a fourth embodiment of the present application, and provides a microwave cavity high-efficiency heating device, which is different from the embodiment 1 in that:

[0060] In the present embodiment, the unidirectional waveguide structure 30 is provided with only one group, and the structure of the unidirectional waveguide structure 30 is the same as that of the embodiment 1 (the first medium section 31 is provided in the third mode), and the unidirectional waveguide structure 30 is fixedly installed on any one of the inner side walls of the straight-wall waveguide 20.

[0061] Embodiment 5

[0062] The present embodiment is a fifth embodiment of the present application, and is an application embodiment of the present application, which is specifically as follows:

[0063] In the present embodiment, the heating effect of the microwave cavity high-efficiency heating device provided in the embodiment 4 on the object to be heated 41 is tested by simulation, which is specifically as follows:

[0064] Test 1

[0065] The volume of the object to be heated 41 is 40*40*25mm, the loss angle is 0.1-1, the real part of the dielectric constant of the object to be heated 41 is 20-100, S11 is used as the evaluation index of the heating effect, and the test result is shown in Table 2:

[0066] Table 2 Simulation test result of the microwave cavity high-efficiency heating device provided in the embodiment 4

[0067]

[0068] Table 3 is the test result of heating the object to be heated 41 by using a conventional microwave heating mechanism, which is different from the microwave cavity high-efficiency heating device provided in the embodiment 4 in that the conventional microwave heating mechanism is not provided with the unidirectional waveguide structure 30, and the simulation test result is shown in Table 3:

[0069] Table 3 Simulation test result of the heating effect of the conventional microwave heating mechanism

[0070]

[0071] Test 2:

[0072] The dielectric constant (dielectric constant is 50) of the object to be heated 41 is kept unchanged, the volume of the object to be heated 41 is changed, and the heating effect of the microwave cavity high-efficiency heating device provided in Example 4 is evaluated by S11 when heating the object to be heated 41. The simulation test results are shown in Table 4:

[0073] Table 4 Simulation test results of the microwave cavity high-efficiency heating device provided in Example 4

[0074]

[0075] Table 5 is the test result of the conventional microwave heating mechanism for heating the object to be heated 41. The dielectric constant (dielectric constant is 50) of the object to be heated 41 is kept unchanged, the volume of the object to be heated 41 is changed, and the simulation test results are shown in Table 5:

[0076] Table 5 Simulation test results of the heating effect of the conventional microwave heating mechanism

[0077]

[0078] The above examples are only used to illustrate the technical solutions of the present application and are not limited. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the present application, and they should be covered in the scope of the claims of the present application. The technical, shape and structure parts not described in detail in the present application are well-known technologies.

Claims

1. A high-efficiency heating device in a microwave cavity, comprising a heating cavity (10) and a straight-wall waveguide (20) with asymmetric transmission function, one end of which communicates with the heating cavity (10), characterized in that, Also comprising: at least one set of unidirectional waveguide structure (30) attached to the inner side wall of the straight-wall waveguide (20); the unidirectional waveguide structure (30) comprises a first dielectric segment (31) and a second dielectric segment (32) arranged in sequence along the microwave transmission direction, the dielectric constant of the first dielectric segment (31) gradually increases along the microwave transmission direction and the maximum value is ε max , the dielectric constant of the second dielectric segment (32) is stable and ε max = ε0; the end of the second dielectric segment (32) protrudes from the straight-wall waveguide (20) and partially extends to the inside of the heating cavity (10).

2. A high efficiency heating device in a microwave cavity as claimed in claim 1, characterized in that: The first end of the second medium section (32) is tightly connected with the tail end of the first medium section (31), or the second medium section (32) is integrally formed with the first medium section (31).

3. A high efficiency heating device in a microwave cavity as claimed in claim 1, wherein: The thickness of the second medium section (32) is equal to the maximum thickness of the first medium section (31).

4. A high efficiency heating device in a microwave cavity as claimed in claim 1, wherein: The height of the one-way waveguide structure (30) is greater than or equal to 2 / 3 of the height of the inner wall of the straight-wall waveguide (20) to which the one-way waveguide structure (30) is attached.

5. A high efficiency heating device in a microwave cavity as claimed in claim 1, wherein: The outer surface of one side of the first medium section (31) is provided with a groove group, which includes a plurality of longitudinal grooves (51) arranged in parallel from the first end to the tail end of the first medium section (31), and the depth of the longitudinal grooves (51) gradually decreases from the first end to the tail end of the first medium section (31).

6. A high efficiency heating device in a microwave cavity as claimed in claim 1, wherein: The thickness of the first medium section (31) gradually increases from the first end to the tail end of the first medium section (31).

7. A high efficiency heating device in a microwave cavity as claimed in claim 1, wherein: The inside of the first medium section (31) is provided with a medium hole group, which includes a plurality of longitudinal medium holes (52) arranged in sequence from the first end to the tail end of the first medium section (31), the inside of each medium hole (52) is filled with a medium, the cross section of each medium hole (52) is circular, and the diameter of the medium hole (52) gradually increases or decreases from the first end to the tail end of the first medium section (31).

8. A high efficiency heating device in a microwave cavity as claimed in claim 1, wherein: A tray (40) is further arranged in the heating cavity (10) for placing an object (41) to be heated.

9. A method of efficient heating in a microwave cavity, characterized by The microwave cavity high-efficiency heating device of any one of claims 1-8 is used to heat an object (41) to be heated, and the object (41) to be heated is placed in the heating cavity (10) statically or actively.

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