CN116528417A

CN116528417A - Microwave heating device with higher order mode suppression

Info

Publication number: CN116528417A
Application number: CN202310328007.5A
Authority: CN
Inventors: 田艳艳
Original assignee: Greater Bay Area University In Preparation
Current assignee: Greater Bay Area University In Preparation
Priority date: 2023-03-29
Filing date: 2023-03-29
Publication date: 2023-08-01

Abstract

The invention discloses a microwave heating device with high-order mode inhibition, which belongs to the technical field of microwave heating and comprises the following components: the heater comprises a rectangular waveguide and metal ridges, wherein the rectangular waveguide is provided with a microwave cavity extending leftwards and rightwards, the two metal ridges are symmetrically arranged in the microwave cavity front and back, the two metal ridges are provided with front and back intervals and are provided with material passing holes extending forwards and back; the high-order mold suppressors are provided with two material cavities which are used for the passage of the to-be-heated piece and extend back and forth along the front and back sides and are communicated with the material passing holes. The microwave heating device has the characteristics of compact structure, high electric field intensity, quick and uniform heating, high-frequency radiation prevention and the like, can avoid operators from being damaged due to space radiation of microwaves, and ensures the use safety of the microwave heating device.

Description

Microwave heating device with higher order mode suppression

Technical Field

The invention belongs to the technical field of microwave heating, and particularly relates to a microwave heating device with high-order mode inhibition.

Background

Microwaves are electromagnetic waves having frequencies in the range of 300 megahertz to 300 gigahertz. Polar molecules exist in the heated medium material, and under the action of a rapidly-changing high-frequency electromagnetic field, the polar orientation of the polar molecules changes along with the change of an external electric field, so that the movement and mutual friction effect of the molecules are caused. At this time, the field energy of the microwave field is converted into heat energy in the medium, so that the temperature of the material is increased, a series of physical and chemical processes of thermalization and puffing are generated, and the purpose of microwave heating and drying is achieved.

Microwave heating has the following advantages: (1) the heating speed is high; the microwave heating mode is completely different from the traditional heating mode, and the microwave heating mode makes the heated material become a heating body without a heat conduction process. Therefore, the heating temperature can be reached in an extremely short time despite the material having poor heat conductivity. (2) energy conservation and high efficiency; since the substance containing moisture easily absorbs microwaves to generate heat, there is little transmission loss and little loss, and therefore, the heat efficiency is high and the energy is saved. (3) heating uniformly; regardless of the shape of each part of the object, the microwave heating can enable the surface and the inner side of the object to uniformly penetrate electromagnetic waves to generate heat energy, so that the heating uniformity is good, and the phenomena of external focus and internal generation can not occur. (4) mildew prevention, sterilization and fresh-keeping. And (5) the process is advanced and easy to control. And (6) small occupied area, safety and innocuity. Therefore, microwave heating is widely used.

However, microwave heating often encounters severe limitations when the material being processed is lost too much or too little, because: when the losses are too large, the power dissipation in the heating channel is too high in order to distribute the energy evenly across the width of the sheet material. In the case of low losses, however, an increase in the heating channels is required in order to absorb the useful power reasonably. In addition, since it is affected by electromagnetic radiation, the exposure of workers to electromagnetic radiation environment for a long time is liable to affect the health. It can be seen that the existing microwave heating apparatus is to be further improved.

Disclosure of Invention

The invention aims to provide a microwave heating device with high-order mode inhibition, which has the advantages of miniaturization of the whole structure, high electric field intensity, quick and uniform heating, high-frequency radiation prevention and the like, can be applied to sheet materials with too large or too small loss, can avoid the influence of the physical health of operators due to the space radiation of microwaves, and ensures the use safety.

The technical scheme adopted for solving the technical problems is as follows:

the invention discloses a microwave heating device with higher order mode inhibition, which comprises:

the heater comprises a rectangular waveguide and metal ridges, wherein the rectangular waveguide is provided with a microwave cavity extending leftwards and rightwards, the two metal ridges are symmetrically arranged in the microwave cavity front and back, the two metal ridges are provided with front and back intervals and are provided with material passing holes extending forwards and backwards;

the high-order mold suppressors are provided with two material cavities for the to-be-heated piece to pass through, extend along the front and back directions and are communicated with the material passing holes, and the front end and the back end of the heater are respectively provided with the high-order mold suppressors.

The invention has at least the following beneficial effects: when the sheet material enters the material passing hole of the heater along the front-back direction, the microwave cavity of the rectangular waveguide is provided with two metal ridges which are symmetrical front and back, so that the electric field distribution can be improved, a strong and uniform electric field is formed between the ridges of the two metal ridges, the coupling between the microwave and the sheet material with low loss can be increased, the sheet material positioned between the two metal ridges can absorb microwave energy more quickly and more uniformly, the effects of quick heating and uniform heating are achieved, and a heating channel and dissipation power in the heating channel do not need to be increased; and the front side and the rear side of the heater are provided with the high-order mode suppressors, so that the energy of the feeding position and the discharging position of the heater is limited, the leakage of high-frequency radiation is prevented, the human body is protected from being exposed to an electromagnetic environment, and the use safety of the microwave heating device is promoted to be improved.

As a further improvement of the technical scheme, the high-order mode suppressor comprises a shell, a metal cylinder and an electromagnetic wave absorber, wherein the shell is connected with the rectangular waveguide, the shell is provided with a material cavity, the metal cylinder and the electromagnetic wave absorber are both arranged on the inner upper wall surface and the inner lower wall surface of the material cavity, and the metal cylinder extends up and down along the upper and lower sides and is positioned between the electromagnetic wave absorber and the heater.

When the microwaves leak from the heater to the high-order mode suppressor, the leaked microwave power is seriously mismatched by utilizing the metal cylinder with the anti-electric property, and is reflected and returned into the heater, one part of the reflected microwave power is absorbed by the sheet material, and the other part of the reflected microwave power is dissipated on the inner wall surface of the heater, so that the utilization rate of the microwave power is improved; then, the electromagnetic wave absorber is utilized to absorb the microwave power which is not reflected by the metal cylinder, so that the microwave power leakage is avoided to the maximum extent; moreover, the metal cylinder and the electromagnetic wave absorber are arranged up and down in the shell, so that the effect on blocking the higher order mode of TE mode is good, and the impedance bandwidth is wider.

As a further improvement of the above technical solution, the electromagnetic wave absorbing member is a silicon carbide block. The silicon carbide block with strong wave absorbing capability is adopted, so that the thickness of the electromagnetic wave absorbing piece can be designed to be smaller, and electromagnetic waves can be absorbed as much as possible, thereby preventing the human body from being influenced by more electromagnetic waves.

As a further improvement of the above technical solution, the higher order mode suppressor further includes a cooling assembly for cooling the electromagnetic wave absorber. By the arrangement, the electromagnetic wave absorber can be cooled by the cooling component, and the working effect of the electromagnetic wave absorber is prevented from being influenced due to overheat of the electromagnetic wave absorber during working.

As a further improvement of the technical scheme, the metal cylinders are arranged in a plurality of ways and are arranged at intervals left and right, the metal cylinders are arranged in a group, and the shell is provided with a plurality of groups of metal cylinders which are arranged at intervals front and back. By arranging the metal cylinders in the front-back direction and the left-right direction, the reflection inhibition effect of the high-order mode inhibitor on the microwave power is enhanced, so that the microwave power is reflected back to the heater as much as possible, and the microwave power leakage is avoided.

As a further improvement of the technical scheme, a plurality of groups of metal cylinders are arranged in an array or staggered mode. By the arrangement, the surface impedance of the high-order mode suppressor can be increased, the suppression effect of the high-order mode suppressor is improved, the high-order mode is enabled to attenuate faster, and the influence of leaked microwave power on people is avoided.

As a further improvement of the above technical solution, the metal cylinder is a screw. By setting the arrangement, the reactance of the high-order mode suppressor can be adjusted by adjusting the insertion depth of the screw.

As a further improvement of the above technical solution, the electromagnetic wave absorbing members on the upper and lower sides are symmetrically arranged with respect to the material passing hole, and the metal cylinders on the upper and lower sides are symmetrically arranged with respect to the material passing hole. By the arrangement, the microwave power leaking from the material passing hole can be well inhibited, and the human health is prevented from being damaged due to the microwave power leakage.

As a further improvement of the technical scheme, the metal ridge is high at the middle part and low at the two sides in the top view, and the material passing hole is formed in the middle part of the metal ridge. The arrangement ensures that the electric field intensity at the material passing hole is increased, the electric field becomes more uniform, the coupling between the material passing hole and the low-loss sheet material is promoted, and the temperature rise of the sheet material is faster and the heating is more uniform.

As a further improvement of the above technical solution, a front-rear distance between two metal ridges is set as a, an up-down dimension of the passing hole is set as b, and a satisfies the following condition: 1.5b < a < 2b. The setting can avoid the too little condition that takes place to strike sparks and break down in clearance between two metal ridges, guarantees microwave heating device safe in utilization, moreover, can also prevent that the clearance between two metal ridges from being too big and influencing electric field coupling to improve microwave heating device and to sheet material's heating effect under the condition of guaranteeing safe handling.

Drawings

The invention is further described below with reference to the drawings and examples;

fig. 1 is a structural perspective view of a microwave heating device with higher order mode suppression according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of an internal structure of a microwave heating device with higher order mode suppression according to an embodiment of the present invention;

FIG. 3 is a perspective view of a microwave heating device with higher order mode suppression according to an embodiment of the present invention in heating sheet material;

FIG. 4 is a cross-sectional view of the microwave heating device with higher order mode suppression provided in FIG. 3 in the XZ plane;

FIG. 5 is a schematic view showing an internal structure of a heater according to an embodiment of the present invention;

FIG. 6 is a cross-sectional view of the microwave heating device with higher order mode suppression provided in FIG. 3 in the XY plane;

FIG. 7 is a graph of electrical performance of a microwave heating device with higher order mode suppression provided by an embodiment of the invention;

FIG. 8 is a graph showing the electric field intensity distribution of a microwave heating device with higher order mode suppression according to an embodiment of the present invention;

FIG. 9 is a graph showing the temperature profile of a sheet material in the case of simulation using the microwave heating apparatus with higher order mode suppression provided by the embodiment of the present invention;

fig. 10 is a graph of temperature rise of a sheet material in the case of simulation using the microwave heating apparatus with higher order mode suppression provided by the embodiment of the present invention.

The figures are marked as follows: 100. a heater; 101. a microwave cavity; 102. a material passing hole; 110. a rectangular waveguide; 120. a metal ridge; 200. a higher order mode suppressor; 201. a material cavity; 210. a housing; 220. a silicon carbide block; 230. a metal cylinder; 300. sheet material.

Detailed Description

Reference will now be made in detail to the present embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein the accompanying drawings are used to supplement the description of the written description so that one can intuitively and intuitively understand each technical feature and overall technical scheme of the present invention, but not to limit the scope of the present invention.

In the description of the present invention, it should be understood that references to orientation descriptions such as upper, lower, front, rear, left, right, etc. are based on the orientation or positional relationship shown in the drawings, are merely for convenience of description of the present invention and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present invention.

In the drawing, the X-direction is directed from the rear side to the front side of the microwave heating device with higher order mode suppression, the Y-direction is directed from the left side to the right side of the microwave heating device with higher order mode suppression, and the Z-direction is directed from the lower side to the upper side of the microwave heating device with higher order mode suppression.

In the description of the present invention, if there is a word description such as "a plurality" or the like, the meaning of the plurality is one or more, the meaning of the plurality is two or more, and greater than, less than, exceeding, etc. are understood to exclude the present number, and above, below, within, etc. are understood to include the present number. The description of first, second, and third is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of technical features indicated.

In the description of the present invention, unless explicitly defined otherwise, terms such as arrangement, installation, connection, etc. should be construed broadly and the specific meaning of the terms in the present invention can be reasonably determined by a person skilled in the art in combination with the specific contents of the technical scheme.

Referring to fig. 1 to 10, several embodiments of the microwave heating apparatus with higher order mode suppression according to the present invention are described below.

As shown in fig. 1 to 10, a first embodiment of the present invention provides a microwave heating device with higher order mode suppression, which is capable of microwave heating of a sheet material with high loss or low loss. The microwave heating device with high order mode suppression includes a heater 100 and a high order mode suppressor 200.

Wherein the heater 100 includes a rectangular waveguide 110 and a metal ridge 120.

The rectangular waveguide 110 has a microwave cavity 101, and the microwave cavity 101 is provided to extend in the left-right direction, so that microwaves in the microwave cavity 101 propagate in the left-right direction. The microwave cavity 101 penetrates the left and right sides of the rectangular waveguide 110, respectively, that is, the rectangular waveguide 110 has left and right openings. In this embodiment, the right opening of the rectangular waveguide 110 is a microwave inlet, the left opening of the rectangular waveguide 110 is a microwave outlet, the long edge of the rectangular waveguide 110 extends in the up-down direction, and the wide edge of the rectangular waveguide 110 extends in the front-back direction. It will be appreciated that a regular metal waveguide made of a metal material (copper, aluminum, etc.) having a rectangular cross section and filled with an air medium is referred to as a rectangular waveguide 110.

The number of the metal ridges 120 is two, and the two metal ridges 120 are arranged in the microwave cavity 101 and are symmetrically arranged front and back. Specifically, one of the metal ridges 120 is connected to the inner front wall surface of the microwave cavity 101, and the other metal ridge 120 is connected to the inner rear wall surface of the microwave cavity 101. The metal ridge 120 and the rectangular waveguide 110 may be connected by welding or an integral molding process. The metal ridge 120 and the rectangular waveguide 110 may be made of 6061 aluminum alloy material.

The two metal ridges 120 have a certain front-to-back spacing therebetween, that is, the two metal ridges 120 do not contact each other. Moreover, each metal ridge 120 is provided with a feed hole 102, the feed holes 102 are arranged to extend in the front-rear direction, the feed holes 102 are communicated with the microwave cavity 101, and the central axes of the feed holes 102 of the two metal ridges 120 coincide, one feed hole 102 penetrates through the front side surface of the rectangular waveguide 110, and the other feed hole 102 penetrates through the rear side surface of the rectangular waveguide 110.

The blanking aperture 102 may be located at a middle position of the metal ridge 120 from a front view, and the blanking aperture 102 has a square shape. The clearance hole 102 allows the sheet material 300 to pass therethrough. The metal ridge 120 exhibits a middle portion that is higher and lower on both sides in a top view. In some embodiments, the shape of the metal ridge 120 is an isosceles trapezoid from a top view. In other embodiments, the metal ridge 120 is T-shaped. In a top view, the material passing hole 102 is disposed in the middle of the metal ridge 120, so that the electric field strength at the material passing hole 102 is increased, the electric field becomes more uniform, the coupling with the low-loss sheet material 300 is promoted, and the temperature rise and the heating of the sheet material 300 are faster and more uniform. In this embodiment, the central axis of the clearance hole 102 coincides with the central axis of the metal ridge 120.

In some embodiments, as shown in fig. 4 and 5, the front-rear spacing between the two metal ridges 120 is set to a, and the upper-lower dimension of the through-hole 102 is set to b, a satisfying the following condition: 1.5b < a < 2b. The metal ridge 120 and the material passing hole 102 are arranged in such a way, so that the problem that the use safety of the microwave heating device is affected due to the fact that the gap between the two metal ridge 120 is designed to be too small to cause ignition breakdown can be avoided; further, it is possible to prevent the electric field coupling from being affected by the excessively large gap between the two metal ridges 120, thereby ensuring high use safety of the microwave heating device and improving the heating effect of the microwave heating device on the sheet material 300.

The number of the high-order mode suppressors 200 is two, and the two high-order mode suppressors 200 are disposed at intervals in the front-rear direction, wherein one high-order mode suppressor 200 is disposed at the front end of the heater 100 and the other high-order mode suppressor 200 is disposed at the rear end of the heater 100. In the present embodiment, the two higher order mode suppressors 200 are front-to-back symmetric about the heater 100. The higher order mode suppressor 200 and the heater 100 may be connected and fixed by welding.

Each of the higher-order mold suppressors 200 is provided with a cavity 201 extending in the front-rear direction and penetrating the front side and the rear side of the higher-order mold suppressor 200, respectively, the cavity 201 being for passing a member to be heated such as a sheet material 300, the sheet material 300 being moved in the front-rear direction with respect to the microwave heating device. After the higher order mode suppressor 200 is connected to the rectangular waveguide 110, the feed cavity 201 communicates with the feed through 102.

In the present embodiment, the higher order mode suppressor 200 located at the front side of the heater 100 is the inlet higher order mode suppressor 200, the higher order mode suppressor 200 located at the rear side of the heater 100 is the outlet higher order mode suppressor 200, the region between the two metal ridges 120 is the heating zone, and the heating zone has microwave power transmission, so that the sheet material 300 passes through the inlet higher order mode suppressor 200, the heater 100 and the outlet higher order mode suppressor 200 in this order from the front to the rear, and absorbs enough heat while the heating zone stays, and exits from the heating zone when the temperature of the sheet material 300 reaches a predetermined value, thereby achieving the heating temperature raising process of the sheet material 300 in the heater 100.

It will be appreciated that in the process of using the microwave heating device to heat the sheet material 300, when the sheet material 300 moves in the front-rear direction and moves to a position between the two metal ridges 120 in the heater 100, since the two metal ridges 120 symmetrical in front-rear are provided in the rectangular waveguide 110, the electric field distribution can be improved, a strong and uniform electric field can be formed between the ridges of the two metal ridges 120, the coupling between the two metal ridges can be increased, the sheet material 300 located between the two metal ridges 120 can absorb microwave energy more quickly and more uniformly, the purposes of quick heating and uniform heating of the sheet material 300 can be achieved, and compared with the prior art, the heating channel and the dissipation power in the heating channel do not need to be increased.

Since the damage caused by radio frequency and microwaves is largely classified into thermal effects and non-thermal effects, human tissues are extremely vulnerable to microwave radiation, and thus, the human body must be protected from exposure to electromagnetic environments. In order to solve the problem, the high-order mode suppressors 200 are provided at both front and rear ends of the heater 100 to limit the energy of the feeding and discharging portions of the heater 100 and prevent the leakage of high-frequency radiation, thereby avoiding the influence on the health of the human body due to the exposure of the workers to the electromagnetic environment and being beneficial to improving the safety performance of the use of the microwave heating device.

In some embodiments, as shown in fig. 1 to 4 and 6, the structure of the high-order mode suppressor 200 includes a housing 210, a metal cylinder 230, and an electromagnetic wave absorber.

In this embodiment, the housing 210 is square from a front view, and the housing 210 may have a rectangular waveguide 110 structure. The long side of the housing 210 extends in the left-right direction, and the wide side of the housing 210 extends in the up-down direction. The shell 210 is provided with a material cavity 201 penetrating the front and the rear, and the shell 210 is fixedly connected with the rectangular waveguide 110. The housing 210 may be made of 6061 aluminum alloy. A metal cylinder 230 and an electromagnetic wave absorber are disposed in the material chamber 201 of the housing 210. The metal cylinder 230 and the electromagnetic wave absorber are located at the wide side of the housing 210 from a front view.

Specifically, the two sets of metal cylinders 230 are disposed at a vertical interval, so that the two sets of metal cylinders 230 have a vertical interval therebetween, allowing the sheet material 300 to pass therethrough. One group of metal cylinders 230 is connected with the inner upper wall surface of the material cavity 201, and the other group of metal cylinders 230 is connected with the inner lower wall surface of the material cavity 201. It is understood that each group of metal cylinders 230 includes a plurality of metal cylinders 230, and both ends of the metal cylinders 230 extend in the up-down direction.

In the present embodiment, each group of metal cylinders 230 includes a plurality of metal cylinders 230 arranged at intervals in the left-right direction, and a plurality of groups of metal cylinders 230 are provided at intervals in the front-rear direction of the housing 210, and the plurality of groups of metal cylinders 230 are arranged in an array. It can be appreciated that the plurality of metal cylinders 230 are disposed in the front-rear direction and the left-right direction of the material cavity 201, so that the surface impedance of the high-order mode suppressor 200 can be increased, and the reflection and suppression effects of the high-order mode suppressor 200 on the microwave power are enhanced, so that the microwave power is reflected into the heater 100 as much as possible, the high-order mode is attenuated more quickly, and the leakage of the microwave power is avoided.

In other embodiments, multiple sets of metal cylinders 230 are staggered.

The metal cylinder 230 may be a pin or screw. In this embodiment, a screw is used, and the housing 210 is provided with a screw hole to which the screw can be connected. Then, the reactance of the higher order mode suppressor 200 can be adjusted by adjusting the insertion depth of the screw so that the susceptance is continuously changed from capacitive to inductive.

In other embodiments, the use of baffles, diaphragms, instead of metal cylinders 230 is not precluded. However, the surface resistance created by the metal cylinder 230 is better.

The electromagnetic wave absorbing parts are provided with two groups which are arranged in an up-down interval way, and a certain up-down interval exists between the two groups of electromagnetic wave absorbing parts. One group of electromagnetic wave absorbing members are fixedly connected with the inner upper wall surface of the material cavity 201, and the other group of electromagnetic wave absorbing members are fixedly connected with the inner lower wall surface of the material cavity 201. The electromagnetic wave absorber is located at one end of the housing 210 away from the passing hole 102, and the metal cylinder 230 is located between the electromagnetic wave absorber and the heater 100. It is understood that each set of electromagnetic wave absorbers may include one, two or more electromagnetic wave absorbers.

In some embodiments, the electromagnetic wave absorber is made of a wave absorbing material such as graphite, ferrite, or the like. In the present embodiment, the electromagnetic wave absorber is a silicon carbide block 220, and the silicon carbide block 220 is fixed in the housing 210 by a silicone rubber adhesive.

It will be appreciated that the microwaves in the heater 100 inevitably leak to the higher-order mode suppressor 200 during the transmission process, and at this time, the metal cylinder 230 in the housing 210 may be utilized, and the metal cylinder 230 has reactance property, so that the leaked microwave power may generate serious mismatch and be reflected into the heater 100, and a part of the reflected microwave power may be effectively absorbed by the sheet material 300, and another part may be dissipated at the inner wall surface of the heater 100, so that the leakage of the microwave power can be avoided, and the utilization rate of the microwave power is improved. In addition, the electromagnetic wave absorber can absorb the microwave power (i.e., the remaining microwave power) which is not reflected by the metal cylinder 230, so that the leakage of the microwave power can be prevented to the maximum extent.

Moreover, the metal cylinder 230 and the electromagnetic wave absorber are installed up and down in the housing 210, so that the effect on blocking the higher order modes of the TE mode is good, and the impedance bandwidth is wider.

To prevent the silicon carbide block 220 from heating during operation, the structure of the higher order mode suppressor 200 also includes a cooling assembly. The cooling component can cool the electromagnetic wave absorbing piece. In this embodiment, the cooling assembly may include a cooling water pipe, and use water to absorb heat generated by the silicon carbide block 220, so as to avoid overheating of the electromagnetic wave absorber during operation and influence on the operation effect of the electromagnetic wave absorber. The cooling water pipes can be arranged in the silicon carbide block 220 in a serpentine manner or on one side of the silicon carbide block 220.

In other embodiments, the cooling assembly cools the silicon carbide block 220 using air cooling.

In this embodiment, the electromagnetic wave absorbing members on the upper and lower sides are symmetrically arranged about the passing hole 102, and the metal cylinders 230 on the upper and lower sides are symmetrically arranged about the passing hole 102, so that the microwave power leaked from the passing hole 102 can be better inhibited, and the threat of human health caused by the leakage of the microwave power is prevented, thereby ensuring the safety of staff.

The microwave heating device of this embodiment adopts the following structural arrangement: two front-back symmetrical metal ridges 120 are arranged in the rectangular waveguide 110, the metal ridges 120 are high in middle and low in two sides, the relation between the front-back distance a of the two metal ridges 120 and the upper and lower dimension b of the material passing hole 102 is 1.5b < a < 2b, the high-order mode suppressors 200 are symmetrically arranged at the front end and the rear end of the rectangular waveguide 110, the high-order mode suppressors 200 are composed of silicon carbide blocks 220 and screws, and the silicon carbide blocks 220 and the screws are vertically symmetrically arranged relative to the material passing hole 102.

As shown in fig. 7, the microwave heating device using the above structure was simulated in the microwave frequency range of 2.3GHz to 2.6GHz, and as a result, it was found that: the minimum value of the input reflection coefficient S11 (also called input return loss) is-50.79636 dB, and the value of the forward transmission coefficient S21 (also called insertion loss) is-0.61069179 dB.

It will be appreciated that the smaller the value of S11, the better, typically suggesting that S11<0.1, i.e., -20dB; the larger the value of S21, the better the ideal value is 1, i.e. 0dB, the higher the efficiency of the transmission of S21, the more S21 is generally recommended to be >0.7, i.e. -3dB. When the microwave frequency is near 2.45GHz, S11 is smaller than-50 dB, and S21 is up to-0.6 dB, so that the microwave heating device is small in input return loss and good in transmission effect, and the sheet material 300 can be heated rapidly and uniformly.

As shown in fig. 8, when the heater 100 employs microwave transmission with a microwave power of 2.45GHz, the electric field intensity at the middle position of the two metal ridges 120 is large and the electric field intensity distribution is uniform. As shown in fig. 9 and 10, the sheet material 300 located between the two metal ridges 120 is uniformly heated and the temperature rise speed is high, so that the microwave heating device can be applied to the sheet material 300 having too great or too small loss.

While the preferred embodiments of the present invention have been illustrated and described, the present invention is not limited to the embodiments, and various equivalent modifications and substitutions can be made by one skilled in the art without departing from the spirit of the present invention, and these are intended to be included in the scope of the present invention as defined in the appended claims.

Claims

1. A microwave heating device with higher order mode suppression, comprising:

2. The microwave heating device with higher order mode suppression according to claim 1, wherein the higher order mode suppressor comprises a housing, a metal cylinder and an electromagnetic wave absorber, the housing is connected with the rectangular waveguide, the housing is provided with the material cavity, the metal cylinder and the electromagnetic wave absorber are arranged on the inner upper wall surface and the inner lower wall surface of the material cavity, and the metal cylinder extends up and down and is located between the electromagnetic wave absorber and the heater.

3. The microwave heating device with higher order mode suppression of claim 2, wherein the electromagnetic wave absorber is a silicon carbide block.

4. A microwave heating apparatus with higher order mode suppression according to claim 3, wherein the higher order mode suppressor further comprises a cooling assembly for cooling the electromagnetic wave absorber.

5. The microwave heating device with higher order mode suppression according to claim 2, wherein a plurality of the metal cylinders are provided and are arranged at intervals in the left-right direction, a plurality of the metal cylinders are provided as a group, and the housing is provided with a plurality of the metal cylinders arranged at intervals in the front-rear direction.

6. The microwave heating device with higher order mode suppression of claim 5, wherein a plurality of groups of the metal cylinders are arranged in an array or staggered.

7. The microwave heating device with higher order mode suppression of claim 6, wherein the metal cylinder is a screw.

8. The microwave heating device with higher order mode suppression according to any one of claims 2 to 7, wherein the electromagnetic wave absorbing members on the upper and lower sides are symmetrically disposed with respect to the through-hole, and the metal cylinders on the upper and lower sides are symmetrically disposed with respect to the through-hole.

9. The microwave heating device with higher order die inhibition according to claim 1, wherein the metal ridge portion is higher on both sides than on the middle portion in a plan view, and the material passing hole is provided in the middle portion of the metal ridge portion.

10. The microwave heating device with higher order mode suppression according to claim 9, wherein a front-rear spacing between two of the metal ridges is set to a, an upper-lower dimension of the passing hole is set to b, and a satisfies the following condition: 1.5b < a < 2b.