Environment-friendly mixed insulating gas liquefaction temperature prediction method based on mean square displacement and conformation analysis

Abstract

The invention discloses an environment-friendly mixed insulating gas liquefaction temperature prediction method based on mean square displacement MSD and conformational analysis. The method comprises the following steps that 1, a system model of environment-friendly insulating gas and a gas mixture of the environment-friendly insulating gas is established; step 2, utilizing Materials Studio simulation software to simulate the molecular dynamics process of the environment-friendly mixed insulating gas at different temperatures based on an NPT ensemble; 3, analyzing mean square displacement MSD of the environment-friendly mixed insulating gas based on a molecular dynamics simulation result, and calculating average mean square displacement; 4, analyzing the conformational change of the environment-friendly mixed insulating gas based on a molecular dynamics simulation result; and 5, predicting the liquefaction temperature of the environment-friendly mixed insulating gas by integrating the mean square displacement and the conformation analysis result. Based on the density functional theory, the liquefaction temperature of the environment-friendly mixed insulating gas is conveniently and quickly predicted through molecular dynamics simulation.

Description

Technical Field

[0001] The present invention relates to the technical field of gas insulation, and more specifically, to a method for predicting the liquefaction temperature of an environmentally friendly mixed insulating gas based on mean square displacement and conformational analysis. Background Art

[0002] In recent years, with the increasing global emphasis on the concept of green environmental protection, the power field has paid extensive attention to the development and application of environmentally friendly insulating gases. Among them, C4F7N, CF3I, perfluorocarbons PFCs (such as c-C4F8, C2F6, C3F8, etc.), and perfluoroketones (C n F 2n O) gases, as potential substitutes for sulfur hexafluoride (SF6), have become research hotspots due to their excellent environmental protection performance and good insulation characteristics. Although the insulation performance and environmental protection performance of these environmentally friendly insulating gases are acceptable, most of them have the problem of relatively high liquefaction temperature. For example, PMVE (perfluoromethyl vinyl ether), as a new type of environmentally friendly insulating gas, has received extensive attention. This gas has weak toxicity, low GWP and ODP, but has the problem of high liquefaction temperature. To overcome this shortcoming, it is often necessary to mix with buffer gases such as CO2 and N2.

[0003] However, there is a blind spot in the research on the influence of the presence of buffer gases on the liquefaction temperature of environmentally friendly insulating gases. For the liquefaction temperature of mixed gases with different proportions, the law is not clear. This research gap has had an adverse impact on the engineering application process of new environmentally friendly insulating gases and restricted their promotion in actual power equipment. Therefore, there is an urgent need to develop a time-saving, labor-saving and accurate analysis method to systematically study the liquefaction temperature characteristics of environmentally friendly insulating gases under different mixing ratios, so as to fill the existing research gap and promote their engineering application. Summary of the Invention

[0004] To solve the above technical problems, the present invention proposes a method for predicting the liquefaction temperature of an environmentally friendly mixed insulating gas based on mean square displacement and conformational analysis, and predicts the liquefaction temperature by drawing a scatter plot of the average mean square displacement.

[0005] To achieve the above object, a method for predicting the liquefaction temperature of an environmentally friendly mixed insulating gas based on mean square displacement and conformational analysis includes the following steps:

[0006] Step 1, establish a system model of an environmentally friendly insulating gas and its gas mixture;

[0007] Step 2, use Materials Studio simulation software to simulate the molecular dynamics process of the environmentally friendly mixed insulating gas at different temperatures based on the NPT ensemble;

[0008] Step 3: Analyze the mean squared displacement (MSD) of the environmentally friendly mixed insulating gas based on the molecular dynamics simulation results, and calculate the average mean squared displacement.

[0009] Step 4: Analyze the conformational changes of the environmentally friendly mixed insulating gas based on the molecular dynamics simulation results.

[0010] Step 5: Predict the liquefaction temperature of the environmentally friendly mixed insulating gas by synthesizing the results of mean squared displacement and conformational analysis.

[0011] Preferably, Step 1 includes: establishing molecular models of the environmentally friendly insulating gas and the buffer gas respectively in the Materials Studio simulation software, and optimizing their geometric structures; mixing the optimized environmentally friendly insulating gas and buffer gas molecules in a predetermined ratio to construct a gas mixture box model; performing relaxation and equilibrium optimization on the box model to obtain a kinetic model for molecular dynamics simulation.

[0012] Preferably, in Step 2, the molecular dynamics process is carried out in the Materials Studio software; under different temperature and mixing ratio conditions, the gas mixture box model is subjected to 1000 ps of molecular dynamics simulation in the NPT ensemble, the simulation step size is set to 1 fs, and a total of 1000 frames are collected for subsequent analysis.

[0013] Preferably, in Step 3, the mean squared displacement (MSD) is calculated based on the NPT simulation results; in the Forcite module of the Materials Studio software, by selecting the Analysis function, the MSD curve of the gas mixture box model is plotted, and the MSD data at different times are obtained, and then the change process of MSD in 1000 ps is analyzed.

[0014] Preferably, in Step 4, the conformational changes are obtained based on the molecular motion trajectory file generated by the NPT simulation; by observing the aggregation process of gas molecules, the conformational change characteristics are analyzed.

[0015] Preferably, in Step 5, the method for predicting the liquefaction temperature of the environmentally friendly mixed insulating gas is as follows: plot the average MSD scatter plot, and take the temperature at which the conformation of the mixed gas agglomerates as the research object; on this scatter plot, near the temperature at which the conformation of the mixed gas agglomerates, select a certain determined temperature as the reference point, fit two linear functions with different slopes to make them as close as possible to all scatter points, and the temperature corresponding to the intersection of the linear functions is the predicted liquefaction temperature.

[0016] Further preferably, the method for plotting the average MSD scatter plot is as follows: sum up the MSD data obtained at a determined temperature and calculate the average value to obtain the average MSD at this temperature; plot the average MSD data at all temperatures as a scatter plot.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention provides an environmentally friendly mixed insulating gas liquefaction temperature prediction method based on mean square displacement and conformational analysis, studies the mean square displacement change and conformational difference of the environmentally friendly mixed insulating gas under different mixing ratios based on the molecular dynamics theory. Based on the scatter plot of conformational change and average mean square displacement, the liquefaction temperature of the environmentally friendly mixed insulating gas is predicted. The present invention provides an implementable and fast prediction method for the liquefaction temperature of the environmentally friendly mixed insulating gas; meanwhile, it also provides a theoretical support for subsequent exploration of the optimal mixing ratio of the environmentally friendly insulating gas and the inert gas. At the same time, it can also provide a reference for exploring the phase change process of other types of molecules. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the box model of the PMVE / CO2 mixed gas. (a) is the box model obtained by mixing PMVE and CO2 at a molar ratio of 5:5; (b) is the box model obtained by mixing PMVE and CO2 at a molar ratio of 7:3.

[0020] Figure 2 is the conformational change of the PMVE / CO2 mixed gas with a mixing ratio of 7:3 at the end of molecular dynamics. (a) is the conformation at a temperature of 183K; (b) is the conformation at a temperature of 163K; (c) is the conformation at a temperature of 143K

[0021] Figure 3 is the scatter plot of the change of the average MSD with temperature, and the temperature corresponding to the intersection point of the linear function is the predicted liquefaction temperature.

[0022] Figure 4 is the flow chart for predicting the liquefaction temperature of the environmentally friendly mixed insulating gas. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following clearly and completely describes the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0024] The present invention proposes an environmentally friendly mixed insulating gas liquefaction temperature prediction method based on mean square displacement and conformational analysis, including the following steps:

[0025] Step 1, establish a system model of environmentally friendly insulating gases and their gas mixtures;

[0026] Step 2, use Materials Studio simulation software to simulate the molecular dynamics process of environmentally friendly mixed insulating gases at different temperatures based on the NPT ensemble;

[0027] Step 3, analyze the mean square displacement (MSD) of the environmentally friendly mixed insulating gas based on the molecular dynamics simulation results and calculate the average mean square displacement;

[0028] Step 4, analyze the conformational changes of the environmentally friendly mixed insulating gas based on the molecular dynamics simulation results;

[0029] Step 5, comprehensively consider the results of mean square displacement and conformational analysis to predict the liquefaction temperature of the environmentally friendly mixed insulating gas.

[0030] Example 1

[0031] Establish a system model of environmentally friendly insulating gases and their gas mixtures.

[0032] Specifically, construct the molecular structure models of PMVE (polymethyl vinyl ether) and CO2 in Materials Studio molecular simulation software. Based on the Forcite module, use the Steepest Descent optimization algorithm, select Fine for quality calculation and COMPASS Ⅱ for force field, and optimize the molecular configurations of PMVE and CO2. After optimization, use the Amorphous Cell module to mix the optimized PMVE molecules and CO2 molecules to generate box models of mixed gases with two CO2 contents of 30% and 50%, as Figure 1 shown. Subsequently, perform relaxation and structural optimization on the box models to finally obtain a stable PMVE / CO2 gas mixture model.

[0033] Example 2

[0034] Use Materials Studio simulation software to simulate the molecular dynamics process of environmentally friendly mixed insulating gases at different temperatures based on the NPT ensemble.

[0035] In specific implementation, under the Forcite module, select the Dynamics task, select Fine for the task quality, and select COMPASSⅡ for the force field. First, perform NPT calculations for 1000 ps on the kinetic models with different mixing ratios at a temperature of 303 K, with a calculation step size of 1 fs, and output 200 frames for subsequent analysis. Subsequently, with a temperature gradient of 10 K, set 20 simulated temperature points to simulate the kinetic models with 3 mixing ratios respectively. During the simulation process, ensure that the motion states of the molecules in the system are the same at the last frame of the previous temperature and the first frame of the next temperature to guarantee the continuity between different temperatures.

[0036] Example 3

[0037] Analyze the mean square displacement (MSD) of the environmentally friendly mixed insulating gas based on the results of molecular dynamics simulation, and calculate the average mean square displacement.

[0038] In specific implementation, use the Analysis function in the Forcite module of Materials Studio software to analyze the mean square displacement (MSD) of the environmentally friendly mixed insulating gas. Sum the MSD data obtained at a determined temperature and calculate the average value to obtain the average MSD at this temperature.

[0039] Example 4

[0040] Analyze the conformational changes of the environmentally friendly mixed insulating gas based on the results of molecular dynamics simulation.

[0041] In specific implementation, observe the xtd file of the molecular dynamics simulation under the NPT ensemble, play the xtd animation to observe the molecular motion trajectory, as Figure 2 shown. At the starting stage of the kinetic process, the conformation of the mixed insulating gas should be that each molecule maintains a distance due to the existence of intermolecular forces until molecular aggregation occurs during the kinetic process at a certain determined temperature, indicating that the conformation of the molecules has changed. This determined temperature is the temperature at which the conformation of the mixed gas undergoes aggregation behavior.

[0042] Example 5

[0043] Based on the comprehensive analysis results of the mean square displacement and conformation, predict the liquefaction temperature of the environmentally friendly mixed insulating gas.

[0044] In specific implementation, plot a scatter diagram of the average mean square displacement (MSD) at each temperature from 303 K to 103 K. Near the temperature at which the conformation of the mixed gas changes, fit two linear functions with different slopes to make them as close as possible to all the scatter points. The intersection point of these two linear functions is the predicted liquefaction temperature, as Figure 3 shown.

[0045] The above content is only an explanation of the structure of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific structure. As long as it does not deviate from the structure of the invention or exceed the scope defined by this claims, it shall fall within the protection scope of the present invention.

Claims

1. A method for predicting the liquefaction temperature of an environmentally friendly hybrid insulating gas based on mean square displacement and conformation analysis, characterized in that: The following steps are involved: Step 1, establishing a system model of environmentally friendly insulating gas and its gas mixture; Step 2, using Materials Studio simulation software to simulate the molecular dynamics process of the environmentally friendly mixed insulating gas at different temperatures based on the NPT ensemble; Step 3, analyzing the mean square displacement (MSD) of the environmentally friendly mixed insulating gas based on the molecular dynamics simulation results, and calculating the average mean square displacement; Step 4, analyzing the conformational changes of the environmentally friendly mixed insulating gas based on the molecular dynamics simulation results; Step 5, combining the mean square displacement and conformation analysis results to predict the liquefaction temperature of the environmentally friendly mixed insulating gas.

2. The method for predicting the liquefaction temperature of an environmentally friendly hybrid insulating gas according to claim 1, characterized in that: The step 1 comprises: establishing molecular models of an environmentally friendly insulating gas and a buffer gas respectively in the Materials Studio simulation software, and optimizing their geometric structures; mixing the optimized environmentally friendly insulating gas and buffer gas molecules in a predetermined proportion to construct a gas mixture box model; and performing relaxation and equilibrium optimization on the box model to obtain a kinetic model that can be used for molecular dynamics simulation.

3. The method for predicting the liquefaction temperature of an environmentally friendly hybrid insulating gas according to claim 1, characterized in that: In step 2, the molecular dynamics process is carried out in Materials Studio software; under different temperature and mixing ratio conditions, the gas mixture box model is subjected to 1000ps molecular dynamics simulation in the NPT ensemble, the simulation step is set to 1fs, and a total of 1000 frames are collected for subsequent analysis.

4. The method for predicting the liquefaction temperature of an environmentally friendly hybrid insulating gas according to claim 1, characterized in that: In step 3, the mean square displacement (MSD) is calculated based on the NPT simulation results. In the Forcite module of the Materials Studio software, by selecting the Analysis function, the MSD curve of the gas mixture box model is drawn, and the MSD data at different times are obtained, and then the change process of the MSD at 1000ps is analyzed.

5. The method for predicting the liquefaction temperature of an environmentally friendly hybrid insulating gas according to claim 1, characterized in that: In step 4, the conformational change is obtained based on the molecular motion trajectory file generated by NPT simulation; and the conformational change characteristics are analyzed by observing the agglomeration process of gas molecules.

6. The method for predicting the liquefaction temperature of an environmentally friendly hybrid insulating gas according to claim 1, characterized in that: In step 5, the method for predicting the liquefaction temperature of the environmentally friendly mixed insulating gas is: draw an average MSD scatter plot, and take the temperature at which the mixed gas conformation agglomerates as the research object; on the scatter plot, select a certain temperature as a reference point near the temperature at which the mixed gas conformation agglomerates, and draw two linear functions with different slopes respectively. If the two linear functions can cover all the scatter points, the temperature corresponding to the intersection of the linear functions is the predicted liquefaction temperature.

7. The method according to claim 6, characterized in that: The method for drawing the average MSD scatter plot is: summing up the MSD data obtained at a certain temperature and calculating the average value to obtain the average MSD at the temperature; and drawing the average MSD data at all temperatures as a scatter plot.

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