Microwave coaxial resonant cavity sensor and method for measuring primary air dust concentration

Abstract

The present application relates to the technical field of coal powder concentration measurement, and specifically to a microwave coaxial resonant cavity sensor and a method for measuring the concentration of coal powder in primary air. The sensor includes: an outer conductor, which is a hollow cylindrical shape with both ends open, and the inner cavity of the outer conductor is cylindrical; an inner conductor, which is cylindrical and arranged in the inner cavity of the outer conductor, the inner conductor and the inner cavity of the outer conductor are coaxial, and a resonant cavity is formed between the inner conductor and the outer conductor; a connecting conductor, which is used to connect the end of the inner conductor to the inner wall of the outer conductor so that the inner conductor and the outer conductor are short-circuited; a coupling excitation port, which is provided on the side wall of the outer conductor, and is used to connect the resonant cavity with an external circuit. The sensor provided by the present application has a simple structure and is easy to manufacture. When it is applied to the measurement of coal powder in primary air, it can continuously sense the changes in the concentration of coal powder in primary air online with high precision, and is not affected by the temperature changes of the measured air-powder two-phase flow.

Description

Technical Field

[0001] The present application relates to the technical field of coal powder concentration measurement, and in particular to a microwave coaxial resonant cavity sensor, a method for measuring the concentration of coal powder in primary air, a processor, and a machine-readable storage medium. Background Art

[0002] The pulverized coal concentration in the primary air duct is an important flow parameter in the pulverized coal boiler of a power plant. It will directly affect the combustion effect of the boiler and plays a primary and key role in the safe production and energy conservation and emission reduction of thermal power plants.

[0003] To date, both internationally and domestically, extensive experimental research has been conducted on the measurement of parameters such as pulverized coal concentration, and numerous measurement schemes have been proposed. Existing gas-solid two-phase flow detection technologies primarily include capacitance, optical, ultrasonic, thermal, and various electromagnetic and electrostatic techniques. The main limitations to the development of online pulverized coal concentration detection technology are as follows: 1. The flow patterns of air-powder flows are extremely complex, making various flow patterns difficult to control. During motion, the spatial distribution of the gas-solid mixture is uneven and varies over time, making mathematical modeling difficult. Therefore, it is difficult to identify its flow patterns, making real-time measurement of pulverized coal parameters challenging. 2. Solid particles cause high-speed erosion and abrasion on invasive sensors based on contact measurement methods, limiting their application. 3. The uneven distribution of spatial sensitivity at different locations in the pipe reduces the measurement accuracy of non-invasive sensors. 4. The harsh on-site environment imposes certain limitations on many measurement methods. Consequently, research on online pulverized coal concentration measurement devices for industrial use has not made significant progress over the years. Summary of the Invention

[0004] The purpose of the embodiments of the present application is to provide a microwave coaxial resonant cavity sensor and a method for measuring the concentration of primary air dust, so as to realize online measurement of industrial coal dust concentration.

[0005] In order to achieve the above-mentioned objectives, the first aspect of the present application provides a microwave coaxial resonant cavity sensor, which includes: an outer conductor, which is a hollow cylindrical shape with two ends open, and the inner cavity of the outer conductor is cylindrical; an inner conductor, which is cylindrical and arranged in the inner cavity of the outer conductor, the inner conductor and the inner cavity of the outer conductor are coaxial, and a resonant cavity is formed between the inner conductor and the outer conductor; a connecting conductor, which is used to connect the end of the inner conductor and the inner wall of the outer conductor to short-circuit the inner conductor and the outer conductor; and a coupling excitation port, which is provided on the side wall of the outer conductor and is used to connect the resonant cavity with an external circuit.

[0006] Based on the first aspect, in some embodiments of the present application, the connecting conductor evenly divides the inlet / outlet of the resonant cavity.

[0007] Based on the first aspect, in some embodiments of the present application, the sensor further includes: a cone head, the cone head is in the shape of a cone, the circular end of the cone head is of the same diameter as the inner conductor, and the circular end of the cone head is coaxially connected to the end of the inner conductor.

[0008] Based on the first aspect, in some embodiments of the present application, the coupling excitation port includes a probe arranged in the resonant cavity; the sensor also includes: wear-resistant ceramics, which are covered on the inner wall of the outer conductor, the outer surface of the inner conductor, the outer surface of the connecting conductor, and the outer surface of the probe.

[0009] Based on the first aspect, in some embodiments of the present application, the ratio of the inner diameter D of the outer conductor to the diameter d of the inner conductor is: 2≤(D / d)≤6.

[0010] In the second aspect, the present application provides a method for measuring the concentration of primary air powder using the above-mentioned microwave coaxial resonant cavity sensor, wherein the sensor is connected in series to the primary air powder pipeline through a connector, so that the air powder in the primary air powder pipeline can freely pass through the sensor; the method is characterized in that the method includes: obtaining the resonant frequency in the resonant cavity; combining the first mapping relationship and the second mapping relationship to obtain the air powder concentration in the resonant cavity; wherein, under the premise that the size structure of the sensor is known, there is a first mapping relationship between the resonant frequency and the dielectric constant of the air powder, and there is a second mapping relationship between the dielectric constant of the air powder and the air powder concentration; before obtaining the resonant frequency, the method also includes: inputting a preselected microwave into the resonant cavity, and the preselected microwave is reflected at the head and tail ends of the resonant cavity to form a pure standing wave.

[0011] Based on the second aspect, in some embodiments of the present application, the method for obtaining the preselected microwaves includes: inputting a series of microwaves with the same amplitude and power but different frequencies into the resonant cavity; if the microwaves at a certain frequency can be reflected at the head and tail ends of the resonant cavity to form a pure standing wave, then the microwaves at this frequency are the preselected microwaves.

[0012] Based on the second aspect, in some embodiments of the present application, the expression of the first mapping relationship is as follows:

[0013] (1)

[0014] In formula (1), Indicates the dielectric constant of the wind powder to be measured; represents the resonant frequency; represents the speed of light; represents the resonant wavelength;

[0015] In formula (1), (2), where Represents the cavity length of the resonant cavity.

[0016] Based on the second aspect, in some embodiments of the present application, the expression of the second mapping relationship is as follows:

[0017] (3)

[0018] In formula (3), represents the complex dielectric constant of wind powder; represents the complex permittivity of air, and , 、 Respectively The real and imaginary parts of ≈1, ≈0; represents the complex dielectric constant of the discrete phase pulverized coal particles; Indicates the concentration of wind powder;

[0019] The above formula (3) can be written as:

[0020] (4)

[0021] In formula (4), 、 Respectively The real and imaginary parts of 、 Respectively The real and imaginary parts of = .

[0022] In a third aspect, the present application provides a processor configured to execute the above-mentioned method for measuring the concentration of primary air dust.

[0023] In a fourth aspect, the present application provides a machine-readable storage medium having instructions stored thereon, which, when executed by a processor, configure the processor to execute the above-mentioned method for measuring the concentration of primary air dust.

[0024] The sensor provided in this application has a simple structure and is easy to manufacture. When used in primary air-powder measurement, it can continuously sense the changes in the primary air-powder concentration online with high precision, and is not affected by the temperature changes of the measured air-powder two-phase flow. The air-powder can flow evenly into the annular resonant cavity to reduce sampling errors.

[0025] Other features and advantages of the embodiments of the present application will be described in detail in the subsequent detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings are used to provide a further understanding of the embodiments of the present application and constitute a part of the specification. Together with the following detailed description, they are used to explain the embodiments of the present application but do not constitute a limitation on the embodiments of the present application. In the accompanying drawings:

[0027] Figure 1 The overall structure of the microwave coaxial resonant cavity sensor in the embodiment of the present application is schematically shown;

[0028] Figure 2 The schematic diagram of the structure of the inner conductor and the connecting conductor of the embodiment of the present application is shown schematically;

[0029] Figure 3 The internal structure diagram of a computer device according to an embodiment of the present application is schematically shown.

[0030] Description of Reference Numerals

[0031] 1-outer conductor; 2-inner conductor; 3-connecting conductor; 4-coupling excitation port; 5-cone head. DETAILED DESCRIPTION

[0032] To make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. It should be understood that the specific implementation methods described herein are only used to illustrate and explain the embodiments of the present application and are not used to limit the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0033] It should be noted that if the embodiments of the present application involve directional indications (such as up, down, left, right, front, back, etc.), such directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0034] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the fact that they can be implemented by ordinary technicians in this field. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0035] Example 1

[0036] This embodiment provides a microwave coaxial resonant cavity sensor, such as Figure 1 and Figure 2 As shown, the sensor includes:

[0037] The outer conductor 1 is illustratively a hollow cylindrical body with open ends, and the inner cavity of the outer conductor 1 is cylindrical. The inner conductor 2 is illustratively a cylindrical body disposed within the inner cavity of the outer conductor 1. The inner conductor 2 is coaxial with the inner cavity of the outer conductor 1, forming a resonant cavity between the inner conductor 2 and the outer conductor 1. The inner conductor 2 can be hollow or solid, but if hollow, both ends should be closed. Specifically, the outer conductor 1 and the inner conductor 2 are both made of a metal with good electrical conductivity.

[0038] The connecting conductor 3 is used to connect the end of the inner conductor 2 with the inner wall of the outer conductor 1 so that the inner conductor 2 and the outer conductor 1 form a short circuit; since the coaxial resonant cavity is regarded as a coaxial line with short circuits at both ends, the connecting conductor 3 used to connect the end of the inner conductor 2 with the inner wall of the outer conductor 1 is indispensable, and in order to ensure that the inner conductor 2 is always coaxial with the inner cavity of the outer conductor 1, a support is also required, so the existence of the connecting conductor 3 has the following functions: 1) connecting the end of the inner conductor 2 with the inner wall of the outer conductor 1 to form a short circuit; 2) supporting the inner conductor 2. In addition, illustratively, the microwave coaxial resonant cavity sensor provided in this embodiment can be used to measure the concentration of primary air dust, and when measuring the concentration of air dust, the sensor needs to be connected in series to the pipeline of the primary air dust (the flow direction of the air dust is consistent with the axial direction of the inner conductor 2). Therefore, during the measurement process, it is also necessary to ensure that the air dust can freely pass through the sensor (resonant cavity), so too much resistance should not be set at both ends of the resonant cavity to avoid affecting the shuttling of the air dust. The preferred structure of the connecting conductor 3 can be adopted as follows Figure 2 In the illustrated structure, connecting conductor 3 can be cylindrical and evenly divide the resonant cavity's (wind and powder) inlet and outlet. This ensures a certain degree of uniformity in wind and powder entering the resonant cavity. Furthermore, to avoid affecting wind and powder transport, its length should be minimized. Therefore, in this embodiment, the length L of connecting conductor 3 is calculated as follows: the inner radius R of outer conductor 1 minus the radius r of inner conductor 2. The ends of connecting conductor 3 are perpendicular to the inner wall (curved surface) of outer conductor 1 and the outer wall (curved surface) of inner conductor 2, respectively.

[0039] In addition, the principle of using a coaxial resonant cavity to measure air-dust concentration in this embodiment is that a change in the air-dust concentration within the resonant cavity indicates a change in the wave propagation medium, which in turn causes a change in the wave's resonant frequency. Therefore, by obtaining the resonant frequency of microwaves in the resonant cavity, the dielectric constant of the air-dust within the resonant cavity can be indirectly measured, thereby reflecting the air-dust concentration. However, obtaining the resonant frequency requires inputting an excitation signal (microwave) into the resonant cavity and generating stable oscillations before acquisition can proceed. Therefore, the sensor also includes a coupling excitation port 4, which can be located on the sidewall of the outer conductor 1 and is used to connect the resonant cavity to an external circuit to accommodate microwave signal input and output, where the external circuit includes an excitation signal generating circuit (device) and a resonant signal acquisition circuit. Exemplarily, the coupling excitation port 4 can be an SMA RF coupling port, operating in TEM mode.

[0040] Furthermore, in order to prevent the accumulation of wind powder at the end of the inner conductor 2 (the inner and outer diameters of the outer conductor 1 are equal to the inner and outer diameters of the wind powder tube, and therefore can be tightly connected through a flange), a cone head 5 is also (integrally) connected to the end of both ends of the inner conductor 2. The cone head 5 is in the shape of a cone, and the circular end of the cone head 5 is equal to the diameter of the inner conductor 2. The circular end of the cone head 5 is coaxially connected to the end of the inner conductor 2 (the tips of the two cone heads 5 are far away from each other).

[0041] Furthermore, the coupling excitation port 4 includes a probe disposed within the resonant cavity. Therefore, as wind dust passes through the sensor, the probe, the inner wall of the outer conductor 1, the outer surface of the inner conductor 2, the outer surface of the connecting conductor 3, and the aforementioned cone head 5 all come into direct contact with the wind dust, inevitably causing wear and tear on these parts. Therefore, in this embodiment, to extend the service life of the sensor, wear-resistant ceramics are embedded, applied, or sheathed on the surfaces of these parts to prevent direct contact with wind dust.

[0042] Furthermore, for a coaxial resonant cavity, its quality factor is primarily related to the ratio (D / d) of the inner diameter length D of the outer conductor 1 to the diameter length d of the inner conductor 2. The magnitude of the quality factor reflects the selectivity of the resonator and the magnitude of the energy loss. When 2≤(D / d)≤6, the quality factor is at a relatively high value. Of course, in practical applications, such as measuring the concentration of air dust, since the inner diameter (2D) and outer diameter of the outer conductor 1 are usually fixed (usually consistent with the inner and outer diameters of the primary air dust tube), (D / d) can only be adjusted by changing the diameter length d of the inner conductor 2. However, if the diameter length d of the inner conductor 2 is too large, it may affect the free flow of air dust. Therefore, the determination of the d value requires comprehensive confirmation by considering multiple influencing factors.

[0043] Example 2

[0044] This embodiment provides a method for measuring the concentration of primary air dust. Specifically, the microwave coaxial resonant cavity sensor described in Example 1 is used. Specifically, the sensor is connected in series to the primary air dust pipe using a connector, so that dust in the primary air dust pipe can freely pass through the sensor.

[0045] Measuring the air dust concentration in the resonant cavity comprises the following steps:

[0046] S1. Under the premise of knowing the size and structure of the sensor, obtain a first mapping relationship between the resonant frequency and the dielectric constant of the wind powder;

[0047] When the size and structure of the sensor are determined, the resonant frequency is only related to the dielectric constant of the air-powder (air + coal powder). The expression of the first mapping relationship is as follows:

[0048] (1)

[0049] In the above formula, Indicates the dielectric constant of the wind powder to be measured; represents the resonant frequency; represents the speed of light; represents the resonant wavelength;

[0050] Before obtaining the resonant frequency, it is necessary to input preselected microwaves into the resonant cavity. When the preselected microwaves are input into the coaxial resonant cavity, pure standing waves need to be formed on the front and rear end surfaces of the cavity, that is, the preselected microwaves are confined in the resonant cavity and will not disappear after multiple reflections. Only in this way can the resonant frequency be collected. After many experiments, it has been shown that the cavity length of the resonant cavity when resonance occurs is l is equal to an integer multiple of 1 / 2 the resonant wavelength λ0, that is, in the above formula (1), (2), where Represents the cavity length of the resonant cavity.

[0051] S2. Obtaining a second mapping relationship between the dielectric constant of the wind powder and the wind powder concentration;

[0052] Specifically, the complex dielectric constant of the wind-powder mixture is ε m * It can be given by the Maxwell-Wagner inhomogeneous dielectric equation:

[0053]

[0054] In the formula, o represents air, α represents the discrete phase coal powder particles, and m represents the mixed medium. φ is the volume fraction (concentration) of pulverized coal, therefore, represents the complex dielectric constant of air, Represents the complex dielectric constant of discrete phase pulverized coal particles.

[0055] Solving this equation, we can obtain the equivalent complex dielectric constant of the air-powder mixed medium m:

[0056] (3)

[0057] The complex dielectric constant can be written as ε * = ε ′- jε '' plural form, respectively ε α * and ε o * The real and imaginary parts of are written into the above formula (3), where, ε ' o ≈1, ε '' o ≈0, then the equivalent complex dielectric constant of the air-powder mixture m can be simplified to:

[0058] (4)

[0059] In formula (4), 、 Respectively The real and imaginary parts of 、 Respectively The real and imaginary parts of = .

[0060] According to the classical dielectric theory, the real and imaginary parts of the complex dielectric constant of the air-powder mixed medium m are calculated by the following formula:

[0061] , (5)

[0062] Where, ε s is the static dielectric constant of the medium; ε ∞ is the high-frequency dielectric constant of the medium; ω is the angular frequency of the alternating electromagnetic field; τ is the dielectric relaxation time of the medium, is the medium temperature t function.

[0063] S3. Obtain the resonant frequency in the resonant cavity, and obtain the air-dust concentration in the resonant cavity by combining the first mapping relationship and the second mapping relationship;

[0064] Specifically, the complex dielectric constant of the air-powder mixture derived from equations (2) and (4) is The real part of Substitute into (1) (that is, = ), the theoretical relationship for measuring coal powder concentration using a coaxial resonant cavity can be obtained:

[0065] ( p =1,2,3…)(6)

[0066] Based on the above formula (6), the coal powder concentration in the resonance cavity can be obtained.

[0067] Furthermore, the above-mentioned preselected microwaves are obtained by inputting a series of microwaves with the same amplitude and power but different frequencies into the resonant cavity. If the microwaves at a certain frequency can be reflected at the head and tail ends of the resonant cavity to form a pure standing wave, then the microwaves at this frequency are the preselected microwaves.

[0068] Example 3

[0069] This embodiment provides a computer device, which may be a server, and its internal structure diagram may be as follows: Figure 3 As shown. The computer device includes a processor A01, a network interface A02, a memory (not shown in the figure) and a database (not shown in the figure) connected via a system bus. Among them, the processor A01 of the computer device is used to provide computing and control capabilities. The memory of the computer device includes an internal memory A03 and a non-volatile storage medium A04. The non-volatile storage medium A04 stores an operating system B01, a computer program B02 and a database (not shown in the figure). The internal memory A03 provides an environment for the operation of the operating system B01 and the computer program B02 in the non-volatile storage medium A04. The database of the computer device is used to store data for measuring the concentration of primary air dust. The network interface A02 of the computer device is used to communicate with an external terminal through a network connection. When the computer program B02 is executed by the processor A01, a method for measuring the concentration of primary air dust is implemented.

[0070] Those skilled in the art will understand that Figure 3 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0071] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present application may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0072] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0073] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0074] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0075] In a typical configuration, a computing device includes one or more processors (CPUs), input / output interfaces, network interfaces, and memory.

[0076] The memory may include non-permanent memory in a computer-readable medium, random access memory (RAM) and / or non-volatile memory in the form of read-only memory (ROM) or flash RAM. The memory is an example of a computer-readable medium.

[0077] Computer-readable media includes both permanent and non-permanent, removable and non-removable media, and can be implemented using any method or technology for information storage. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change RAM (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, compact disc read-only memory (CD-ROM), digital versatile disc (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission media that can be used to store information that can be accessed by a computing device. As defined herein, computer-readable media does not include transitory computer-readable media, such as modulated data signals and carrier waves.

[0078] It should also be noted that the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, commodity, or apparatus that includes a series of elements includes not only those elements but also other elements not explicitly listed, or includes elements inherent to such process, method, commodity, or apparatus. In the absence of further limitations, an element defined by the phrase "comprises a ..." does not exclude the presence of other identical elements in the process, method, commodity, or apparatus that includes the element.

[0079] The above are merely embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various changes and variations. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should all be included within the scope of the claims of the present application.

Claims

1. A method for measuring the concentration of primary air dust using a microwave coaxial resonant cavity sensor, wherein the sensor is connected in series to the primary air dust pipe via a connector, allowing dust in the primary air dust pipe to freely pass through the sensor, characterized in that: The sensor comprises: an outer conductor, which is a hollow cylindrical shape with two ends open, and the inner cavity of the outer conductor is cylindrical; an inner conductor, which is cylindrical and arranged in the inner cavity of the outer conductor, the inner conductor and the inner cavity of the outer conductor are coaxial, and a resonant cavity is formed between the inner conductor and the outer conductor; a connecting conductor, which is used to connect the end of the inner conductor to the inner wall of the outer conductor to form a short circuit between the inner conductor and the outer conductor; a coupling excitation port, which is provided on the side wall of the outer conductor and is used to connect the resonant cavity with an external circuit; a cone head, which is a cone, the circular end of the cone head has the same diameter as the inner conductor, and the circular end of the cone head is coaxially connected to the end of the inner conductor; the coupling excitation port comprises a probe arranged in the resonant cavity; wear-resistant ceramics, which are coated on the inner wall of the outer conductor, the outer surface of the inner conductor, the outer surface of the connecting conductor, and the outer surface of the probe; the method comprises: Inputting preselected microwaves into the resonant cavity, the preselected microwaves are reflected at both ends of the resonant cavity to form pure standing waves; Obtaining the resonant frequency in the resonant cavity; The wind powder concentration in the resonant cavity is obtained by combining the first mapping relationship and the second mapping relationship; wherein, under the premise that the size structure of the sensor is known, there is a first mapping relationship between the resonant frequency and the dielectric constant of the wind powder, and there is a second mapping relationship between the dielectric constant of the wind powder and the wind powder concentration.

2. The method for measuring the concentration of dust in primary air using a microwave coaxial resonant cavity sensor according to claim 1, characterized in that: The ratio of the inner diameter D of the outer conductor to the diameter d of the inner conductor is: 2≤D / d≤6.

3. The method for measuring the concentration of dust in primary air using a microwave coaxial resonant cavity sensor according to claim 1, characterized in that: The method for obtaining the preselected microwaves comprises: A series of microwaves with the same amplitude and power but different frequencies are input into the resonant cavity. If the microwaves at a certain frequency can be reflected at both ends of the resonant cavity to form a pure standing wave, the microwaves at this frequency are preselected microwaves.

4. The method for measuring the concentration of dust in primary air using a microwave coaxial resonant cavity sensor according to claim 1, characterized in that: The expression of the first mapping relationship is as follows: （1） In formula (1), Indicates the dielectric constant of the wind powder to be measured; represents the resonant frequency; represents the speed of light; represents the resonant wavelength; In formula (1), (2), where , Represents the cavity length of the resonant cavity.

5. The method for measuring the concentration of dust in primary air using a microwave coaxial resonant cavity sensor according to claim 4, characterized in that: The expression of the second mapping relationship is as follows: （3） In formula (3), represents the complex dielectric constant of wind powder; represents the complex permittivity of air, and , 、 Respectively The real and imaginary parts of ≈1, ≈0; represents the complex dielectric constant of the discrete phase pulverized coal particles; Indicates the concentration of wind powder; The above formula (3) can be written as: （4） In formula (4), 、 Respectively The real and imaginary parts of 、 Respectively The real and imaginary parts of = .

6. A processor, characterized in that: The device is configured to perform the method for measuring the concentration of dust in primary air by using a microwave coaxial resonant cavity sensor according to any one of claims 1 to 5.

7. A machine-readable storage medium having instructions stored thereon, characterized in that: When the instruction is executed by a processor, the processor is configured to execute the method for measuring the concentration of dust in primary air by using a microwave coaxial resonant cavity sensor according to any one of claims 1 to 5.

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