Evaluation method of lunar soil microwave heating effect

Abstract

The invention relates to a lunar soil microwave heating effect evaluation method. The method comprises the following steps: establishing a microwave cavity model enclosed by a metal boundary; calculating electric field distribution of the lunar soil according to the magnetic conductivity and the complex dielectric constant of the lunar soil; a plurality of sampling bodies are arranged in the target area, and microwave energy absorbed by each sampling body is calculated according to electric field distribution of lunar soil; determining the specific heat capacity of the lunar soil along with the temperature change, and calculating the temperature change rate in each sampling body according to the microwave energy; calculating the standard deviation and the average value of the temperature change rates of all the sampling bodies, and obtaining a variable coefficient along with the temperature change; and when the temperature of the lunar soil is balanced, judging the microwave heating uniformity of the lunar soil according to the variable coefficient. In the process of analyzing the lunar soil microwave heating effect, starting from the first principle, the characteristic that the specific heat capacity of the lunar soil changes along with the temperature is considered, the physical reality that the lunar soil absorption energy changes along with the temperature in the process of converting the lunar soil absorption energy into the temperature is fitted, and the accuracy of lunar soil microwave heating effect analysis is improved.

Description

Technical Field

[0001] This application relates to the field of lunar in-situ resource utilization technology, specifically to a method for evaluating the effect of lunar soil microwave heating. Background Technology

[0002] The microwave-heated lunar regolith unit's main task is to generate continuous-wave microwave power and effectively heat the lunar regolith. It can independently sinter regularly shaped lunar regolith bricks and also provide auxiliary heating for the fabrication of concentrated-wave printed lunar regolith bricks. Microwave heating of lunar regolith fully utilizes the loss characteristics of microwave dielectrics, exhibiting bulk heating properties. Heating uniformity is a crucial parameter for heating effectiveness, significantly impacting whether the lunar regolith bricks can be regularly shaped and the heating efficiency.

[0003] Current research focuses on in-situ resource utilization of lunar regolith and the uniformity of microwave heating. Existing technologies quantitatively assess the electric field uniformity of microwave cavities with mode stirrs, but do not discuss the energy absorption and temperature uniformity of the heated body, nor do they consider the impact of changes in the physical properties of the heated body with varying states. Furthermore, while artificial magnetic conductors are used to improve electromagnetic field uniformity, they require precise design and control, have low fault tolerance, and their reliability in the high vacuum and large temperature difference environment of the lunar surface is unknown. Existing studies on lunar regolith microwave heating often use the difference in macroscopic shrinkage after sintering or the surface temperature non-uniformity coefficient as uniformity criteria, failing to reveal the true nature of electromagnetic field heating. Summary of the Invention

[0004] In order to overcome at least one deficiency in the prior art, this application provides a method for evaluating the effect of lunar soil microwave heating.

[0005] Firstly, a method for evaluating the effect of microwave heating of lunar soil is provided, including: A microwave cavity model enclosed by a metal boundary is established, and lunar soil is placed inside the microwave cavity model; the target area of ​​the lunar soil is heated by microwaves through the input port of the microwave cavity model. Calculate the electric field distribution of lunar soil based on its magnetic permeability and complex permittivity. Multiple sampling bodies were set up in the target area of ​​lunar soil, and the microwave energy absorbed by each sampling body was calculated based on the electric field distribution of lunar soil. The specific heat capacity of lunar soil under temperature variation was determined, and the rate of temperature change within each sample was calculated based on microwave energy. Based on the temperature change rate within each sample, calculate the standard deviation and average of the temperature change rates of all sample samples, and obtain the coefficient of variation with temperature based on the standard deviation and average. When the lunar soil temperature reaches equilibrium, the uniformity of microwave heating of the lunar soil is determined based on the coefficient of variation.

[0006] In one embodiment, the electric field distribution of lunar soil is calculated based on its magnetic permeability and complex permittivity using the following formula:

[0007] in, For the Laplace operator, The magnetic permeability of lunar soil, The electric field distribution of the lunar soil. The microwave angular frequency, is the complex permittivity of lunar soil.

[0008] In one embodiment, the microwave energy absorbed by each sample volume is calculated based on the electric field distribution of the lunar soil using the following formula:

[0009] in, Microwave energy, It is the microwave angular frequency. This represents the imaginary part of the complex permittivity of lunar soil. The volume of the sample. This represents the electric field distribution of the lunar soil.

[0010] In one embodiment, the sampling volume is a cube with a side length of [missing information]. , This refers to the microwave wavelength.

[0011] In one embodiment, the rate of temperature change within each sample cell is:

[0012]

[0013] in, The rate of temperature change within the sampled body. Microwave energy, The specific heat capacity of lunar soil as a function of temperature. For time t The temperature at that time.

[0014] In one embodiment, the coefficient of variation with temperature is:

[0015] in, The coefficient of variation is given by temperature. The standard deviation of the rate of temperature change for all sampled bodies. This is the average of the temperature change rates of all sampled bodies.

[0016] In one embodiment, when the lunar soil temperature reaches equilibrium, determining the uniformity of microwave heating of the lunar soil based on the coefficient of variation includes: Determine the coefficient of variation when the lunar soil temperature reaches equilibrium. If the coefficient of variation is less than a set threshold, the lunar soil is judged to be uniformly heated by microwave; otherwise, the lunar soil is judged to be unevenly heated by microwave.

[0017] Compared with the prior art, this application has the following beneficial effects: 1. This application is applicable to the uniformity judgment of lunar soil under microwave heating. It can effectively analyze the overall heating effect and uniformity of lunar soil under microwave heating conditions. The analysis results are sensitive to the parameters of the heated object. The analysis process can obtain details that are difficult to capture in experiments, and provide targeted optimization strategies for obtaining regularly shaped lunar soil bricks.

[0018] 2. Since lunar soil sintering experiments must be carried out in a vacuum, the experimental cycle is long and the cost is high. This application provides an effective analytical method for improving the lunar soil brick preparation process, which can shorten the design cycle and reduce the research and development cost.

[0019] 3. In analyzing the microwave heating effect of lunar soil, this application starts from first principles and considers the characteristics of the specific heat capacity of lunar soil changing with temperature. This is consistent with the physical reality of the process of lunar soil absorbing energy and converting it into temperature, thus improving the accuracy of the analysis of the microwave heating effect of lunar soil. Attached Figure Description

[0020] This application can be better understood by referring to the description given below in conjunction with the accompanying drawings, which, together with the detailed description below, are incorporated in and form part of this specification. In the drawings: Figure 1 A flowchart of the evaluation method for the effect of lunar soil microwave heating is shown; Figure 2 The structure of microwave-heated lunar soil and the sample body are shown. Detailed Implementation

[0021] Exemplary embodiments of the present application will be described below with reference to the accompanying drawings. For clarity and brevity, not all features of the actual embodiments are described in the specification. However, it should be understood that many embodiment-specific decisions can be made in the development of any such actual embodiment to achieve the developer’s specific objectives, and these decisions may vary as the embodiments differ.

[0022] It should also be noted that, in order to avoid obscuring this application with unnecessary details, only the device structure closely related to the solution of this application is shown in the accompanying drawings, while other details that are not closely related to this application are omitted.

[0023] It should be understood that this application is not limited to the described embodiments by virtue of the following description with reference to the accompanying drawings. In this document, embodiments may be combined with each other, features may be substituted or borrowed between different embodiments, and one or more features may be omitted in one embodiment, where feasible.

[0024] This application provides a method for evaluating the effect of microwave heating of lunar soil. Figure 1 A flowchart illustrating the evaluation method for the effect of lunar soil microwave heating is shown; see [link / reference]. Figure 1 The method mainly includes the following steps: Step S1: Establish a microwave cavity model enclosed by a metal boundary, and place lunar soil inside the microwave cavity model; heat the target area of ​​the lunar soil with microwaves through the input port of the microwave cavity model.

[0025] Here, lunar regolith is an artificially created concept based on the actual composition of lunar regolith. First, the magnetic permeability of the lunar regolith is determined. Complex permittivity and determine the microwave frequency. .

[0026] Step S2: Calculate the electric field distribution of the lunar soil based on its magnetic permeability and complex permittivity.

[0027] Specifically, the electric field distribution of lunar soil is calculated using the following formula:

[0028] in, For the Laplace operator, The magnetic permeability of lunar soil, The electric field distribution of the lunar soil. It is the microwave angular frequency. , For microwave frequencies, The complex permittivity of lunar soil is . ,in, The dielectric constant of lunar soil is . The electrical conductivity of lunar soil.

[0029] Step S3: Set up multiple sampling bodies in the target area of ​​lunar soil, and calculate the microwave energy absorbed by each sampling body based on the electric field distribution of lunar soil.

[0030] Here, the sampling volume is a cube with a side length of . , Given the microwave wavelength, the volume of the sample volume can be obtained based on the side length. .

[0031] The microwave energy absorbed by each sampler is calculated using the following formula:

[0032] in, Microwave energy, It is the microwave angular frequency. This represents the imaginary part of the complex permittivity of lunar soil. The volume of the sample. This represents the electric field distribution of the lunar soil.

[0033] Step S3: Determine the specific heat capacity of lunar soil under temperature changes, and calculate the temperature change rate within each sample body based on microwave energy.

[0034] Considering that the specific heat capacity of lunar soil and other media materials changes continuously with temperature, the fitted expression for the specific heat capacity of lunar soil with temperature variation is obtained based on experimental results as follows: ,in For time t Temperature at time, in units of K Then the rate of temperature change within each sample cell is obtained. , where is the rate of temperature change with temperature variation.

[0035] Step S4: Calculate the standard deviation and average value of the temperature change rate of all samples based on the temperature change rate of each sample, and obtain the coefficient of variation with temperature change based on the standard deviation and average value.

[0036] For N sample bodies, based on the temperature change rate within each sample body, calculate the standard deviation and mean of the temperature change rates for all sample bodies. Here, the standard deviation of the temperature change rates for all sample bodies is the standard deviation under temperature variation, and similarly, the mean is the average under temperature variation. The coefficient of variation under temperature variation can be obtained from the standard deviation and mean.

[0037]

[0038] in, The coefficient of variation is given by temperature. The standard deviation of the rate of temperature change for all sampled bodies. This is the average of the temperature change rates of all sampled bodies. For the first i Temperature change rate within each sample body.

[0039] Step S5: When the lunar soil temperature reaches equilibrium, the uniformity of microwave heating of the lunar soil is determined based on the coefficient of variation.

[0040] Here, the coefficient of variation corresponding to the point where the lunar soil temperature reaches equilibrium is first determined. If the coefficient of variation is less than a set threshold, the lunar soil is judged to be uniformly heated by microwave; otherwise, the lunar soil is judged to be unevenly heated by microwave. The set threshold varies depending on the system and is not specifically defined here; it is an empirical value.

[0041] To further verify the effectiveness of the method in this application, the following experimental analysis was conducted.

[0042] Microwave input was 6.2 GHz, the dielectric constant of lunar soil was 3.2, and the microwave cavity was made of 310 stainless steel. Due to the symmetry of microwave propagation along the direction within a regular metal cavity, sampling bodies were placed only in half of the lunar soil region. Figure 2 The structure and sampling volume of microwave-heated lunar regolith are shown. The small red cube is the sampling volume, with a side length of 3 mm. Two heating states are set up; state 1 shows a total lunar regolith volume of 216... cm 3 State 2 has a total lunar soil volume of 259.2 cubic meters. cm 3 The uniformity of microwave-heated lunar soil under the two conditions was analyzed, as shown in Table 1. Table 1 shows that the uniformity of microwave-heated lunar soil under condition 1 is better than that under condition 2.

[0043] Table 1. Results of homogeneity analysis of microwave-heated lunar soil under two conditions.

[0044] In summary, this application has the following technical effects: 1. This application is applicable to the uniformity judgment of lunar soil under microwave heating. It can effectively analyze the overall heating effect and uniformity of lunar soil under microwave heating conditions. The analysis results are sensitive to the parameters of the heated object. The analysis process can obtain details that are difficult to capture in experiments, and provide targeted optimization strategies for obtaining regularly shaped lunar soil bricks.

[0045] 2. Since lunar soil sintering experiments must be carried out in a vacuum, the experimental cycle is long and the cost is high. This application provides an effective analytical method for improving the lunar soil brick preparation process, which can shorten the design cycle and reduce the research and development cost.

[0046] 3. In analyzing the microwave heating effect of lunar soil, this application starts from first principles and considers the characteristics of the specific heat capacity of lunar soil changing with temperature. This is consistent with the physical reality of the process of lunar soil absorbing energy and converting it into temperature, thus improving the accuracy of the analysis of the microwave heating effect of lunar soil.

[0047] The above descriptions are merely various embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for evaluating the effect of microwave heating of lunar soil, characterized in that, include: A microwave cavity model enclosed by a metal boundary is established, and lunar soil is placed inside the microwave cavity model; Microwave heating of the target area of ​​lunar soil is performed through the input port of the microwave cavity model; Calculate the electric field distribution of lunar soil based on its magnetic permeability and complex permittivity. Multiple sampling bodies are set up in the target area of ​​lunar soil, and the microwave energy absorbed by each sampling body is calculated based on the electric field distribution of the lunar soil. The specific heat capacity of lunar soil under temperature variation was determined, and the rate of temperature change within each sample was calculated based on the microwave energy. Based on the temperature change rate within each sample body, calculate the standard deviation and average value of the temperature change rates of all sample bodies, and obtain the coefficient of variation with temperature change based on the standard deviation and the average value. When the lunar soil temperature reaches equilibrium, the uniformity of microwave heating of the lunar soil is determined based on the coefficient of variation.

2. The method as described in claim 1, characterized in that, in, The electric field distribution of lunar regolith is calculated using the following formula based on its magnetic permeability and complex permittivity: in, For the Laplace operator, The magnetic permeability of lunar soil, The electric field distribution of the lunar soil. It is the microwave angular frequency. is the complex permittivity of lunar soil.

3. The method as described in claim 1, characterized in that, in, The microwave energy absorbed by each sample body is calculated based on the electric field distribution of the lunar soil using the following formula: in, Microwave energy, It is the microwave angular frequency. This represents the imaginary part of the complex permittivity of lunar soil. The volume of the sample. This represents the electric field distribution of the lunar soil.

4. The method as described in claim 3, characterized in that, The sampling body is a cube with a side length of [missing information]. , This refers to the microwave wavelength.

5. The method as described in claim 1, characterized in that, The temperature change rate within each sample cell is: in, The rate of temperature change within the sampled body. Microwave energy, The specific heat capacity of lunar soil varies with temperature. For time t The temperature at that time.

6. The method as described in claim 1, characterized in that, The coefficient of variation with temperature is: in, The coefficient of variation is given by temperature. The standard deviation of the rate of temperature change for all sampled bodies. This is the average of the temperature change rates of all sampled bodies.

7. The method as described in claim 1, characterized in that, When the lunar soil temperature reaches equilibrium, the uniformity of microwave heating of the lunar soil is determined based on the coefficient of variation, including: Determine the coefficient of variation when the lunar soil temperature reaches equilibrium. If the coefficient of variation is less than a set threshold, the lunar soil is judged to be uniformly heated by microwave; otherwise, the lunar soil is judged to be unevenly heated by microwave.

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