A combustible working medium explosion characteristic evaluation index construction method and system

Abstract

The application discloses a combustible working medium combustion characteristic evaluation index construction method, takes combustion characteristic parameters of a typical combustible working medium as a benchmark, takes a ratio of combustion characteristic parameters of a combustible working medium to be evaluated to the combustion characteristic parameters of the typical combustible working medium as an evaluation index factor, and determines the evaluation index of the combustion characteristic of the combustible working medium to be evaluated. The application also provides a combustible working medium combustion characteristic evaluation index system, which inputs combustion characteristic parameters of CH4 and combustion characteristic parameters of the combustible working medium to be evaluated, and outputs the combustion characteristic evaluation index of the combustible working medium to be evaluated. The application is based on molecular microstructure characteristics, combines calculable combustion characteristic parameters such as combustion limit, combustion speed, minimum ignition energy and combustion heat, and proposes a scientific index for evaluating the combustion characteristic of the combustible working medium, which provides a reference basis for designing a working medium combustion experiment device, calculating working medium danger and other safety reliability evaluation parameters, and is convenient to popularize.

Description

Technical Field

[0001] This invention relates to the field of gas combustion and explosion safety technology, specifically to a method and system for constructing evaluation indicators of the combustion and explosion characteristics of combustible working fluids. Background Technology

[0002] Currently, the problem of climate change caused by global warming is becoming increasingly prominent, and reducing greenhouse gas emissions and mitigating the greenhouse effect have become urgent global issues. On October 15, 2016, nearly 200 countries worldwide signed the Kigali Amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer, which clearly outlines a timetable for countries to phase out HFCs. China strives to achieve carbon peaking before 2030 and carbon neutrality before 2060. Therefore, the world is actively seeking new-generation alternative working fluids with zero ozone depletion potential (ODP), low global warming potential (GWP), and good thermophysical properties.

[0003] However, most low-GWP working fluids are flammable, making the evaluation of their combustion characteristics crucial. In existing technologies, researchers typically use flammability limits as the primary evaluation criterion for flammability rating, supplementing it with combustion rate and heat of combustion. This approach fails to comprehensively evaluate the working fluid's combustion characteristics, thus presenting certain shortcomings. Therefore, a new evaluation index that comprehensively characterizes the combustion characteristics and safety of flammable working fluids is urgently needed. Summary of the Invention

[0004] This invention provides a method and system for constructing evaluation indicators of the combustion and explosion characteristics of combustible working fluids to solve the technical problems existing in the prior art.

[0005] The technical solution adopted by this invention to solve the technical problems existing in the prior art is: a method for constructing evaluation indexes of the combustion and explosion characteristics of combustible working fluids, which uses the combustion and explosion characteristic parameters of a typical combustible working fluid as a benchmark, and uses the ratio of the combustion and explosion characteristic parameters of the combustible working fluid to be evaluated to the combustion and explosion characteristic parameters of the typical combustible working fluid as an evaluation index factor to determine the evaluation indexes of the combustion and explosion characteristics of the combustible working fluid to be evaluated.

[0006] Furthermore, using the combustion and explosion characteristics parameters of CH4 as a benchmark, the combustion and explosion characteristics parameters of the combustible working medium to be evaluated are compared with the corresponding combustion and explosion characteristics parameters of CH4 to obtain a set of dimensionless parameters. This set of dimensionless parameters is used as evaluation index factors and calculated according to the following formula to obtain the evaluation index of the combustion and explosion characteristics of the combustible working medium to be evaluated:

[0007]

[0008] in:

[0009]

[0010]

[0011]

[0012] In the formula:

[0013] VEIN is an evaluation index for the combustion and explosion characteristics of combustible working fluids, also known as the velocity energy factor.

[0014] S u * This is the ratio of the combustion rate of the combustible working substance to be evaluated to the combustion rate of CH4;

[0015] MIE * This is the ratio of the minimum ignition energy of the combustible working fluid to be evaluated to the minimum ignition energy of CH4.

[0016] H C * The ratio of the heat of combustion of the combustible working substance to be evaluated to the heat of combustion of CH4;

[0017] S u R The combustion rate of the combustible working fluid to be evaluated;

[0018] The combustion rate of CH4;

[0019] MIE R The minimum ignition energy of the combustible working fluid to be evaluated;

[0020] This is the minimum ignition energy of CH4;

[0021] H C R The heat of combustion of the combustible working fluid to be evaluated;

[0022] The heat of combustion of CH4.

[0023] Furthermore, by combining the velocity energy factor of the combustible working substance to be evaluated with its lower ignition limit concentration characteristic parameter, the comprehensive evaluation index CEI of the combustion and explosion characteristics of the combustible working substance to be evaluated is obtained according to the following formula:

[0024] CEI = LFL * ln(1 + VEIN);

[0025] LFL is the lower ignition limit concentration characteristic parameter value of the combustible working substance to be evaluated;

[0026] CEI is a comprehensive evaluation index for the combustion and explosion characteristics of the combustible working medium to be evaluated.

[0027] Furthermore, assuming the VEIN value of CH4 is 1, the CEI of CH4 is calculated to be 0.69. Based on the CEI value, combustible working substances are divided into three categories: A, B, and C. Combustible working substances with CEI ≥ 5 are classified as category C; combustible working substances with 5 > CEI > 0.7 are classified as category B; and combustible working substances with CEI ≤ 0.7 are classified as category A.

[0028] Furthermore, the combustion rate can be predicted by the type and number of molecular groups.

[0029] Furthermore, the combustion rate is predicted using the following linear fitting formula:

[0030] S u，max =47.773-0.843R C-C +7.937R C＝C +4.386R ＝O +5.332R -O- -12.717R -NH2 -22.400R CF -44.937R CF2 -107.444R CF3

[0031] In the formula:

[0032] S u，max The maximum combustion rate of the combustible working fluid to be evaluated;

[0033] R C-C The number of carbon atoms in a single-bonded carbon molecule;

[0034] R C＝C The number of carbon atoms in a double-bonded carbon molecule;

[0035] R ＝O The number of double-bonded oxygen groups in the molecule;

[0036] R -O- The number of single-bonded oxygen groups in the molecule;

[0037] R -NH2 The number of nitrogen-containing groups in the molecule;

[0038] R CF The number of CF groups;

[0039] R CF2 The number of CF2 groups;

[0040] R CF3 This represents the number of CF3 groups.

[0041] Furthermore, a multiple linear regression algorithm was used to perform regression calculations on the minimum ignition energy data.

[0042] Furthermore, the minimum ignition energy is calculated using the following regression formula:

[0043] lg(MIE)=0.011+0.003MW+0.104DM-12.801ε HOMO -33.641ε LUMO -106.725ω+0.136SP+0.086n C +0.018n H -0.296n F ;

[0044] In the formula:

[0045] MIE stands for Minimum Ignition Energy;

[0046] MW is the molecular weight;

[0047] DM is a dipole moment;

[0048] SP represents the energy of a single molecular structure.

[0049] n C The number of carbon atoms;

[0050] n H The number of hydrogen atoms;

[0051] n F The number of fluorine atoms;

[0052] ε HOMO It is a HOMO energy level;

[0053] ε LUMO It is the LUMO energy level;

[0054] MW, DM, SP, n C n H Positively correlated with MIE value;

[0055] n F ε HOMO ε LUMO It is negatively correlated with the MIE value.

[0056] The present invention also provides a combustible working medium combustion and explosion characteristic evaluation index system. The system is constructed using the above-mentioned combustible working medium combustion and explosion characteristic evaluation index construction method. The system takes CH4 combustion and explosion characteristic parameters and the combustion and explosion characteristic parameters of the combustible working medium to be evaluated as inputs, and outputs the combustion and explosion characteristic evaluation index of the combustible working medium to be evaluated.

[0057] The advantages and positive effects of this invention are:

[0058] This invention provides a method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working substances. Based on molecular microstructure characteristics and combined with calculable combustion and explosion characteristic parameters such as combustion limit, combustion rate, minimum ignition energy, and heat of combustion, it proposes a scientific index for evaluating the combustion and explosion characteristics of combustible working substances. This invention features simple steps and a reasonable design. It provides accurate prediction results and serves as a reference for designing combustion and explosion experimental devices for working substances, calculating the hazard of working substances, and evaluating other safety and reliability parameters. Furthermore, it is easy to promote. Its specific features include:

[0059] (1) It can be used as an evaluation index to verify the flammability of the working medium and to comprehensively measure the strength of flammability.

[0060] (2) It can be used as a parameter for designing working fluid flammability test devices, calculating working fluid hazard, and other safety and reliability evaluation.

[0061] (3) It can be used in aviation, aerospace and other fields and is a new indicator for measuring thermal properties. Attached Figure Description

[0062] Figure 1 This is a schematic diagram of the workflow of the present invention.

[0063] Figure 2 This is a graph showing the relationship between CEI and combustion rate.

[0064] Figure 3 This is the CEI-Minimum Ignition Energy relationship diagram. Detailed Implementation

[0065] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0066] Please see Figures 1 to 3 A method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working substances is proposed. The method uses the combustion and explosion characteristic parameters of a typical combustible working substance as a benchmark, and uses the ratio of the combustion and explosion characteristic parameters of the combustible working substance to be evaluated to the combustion and explosion characteristic parameters of the typical combustible working substance as an evaluation index factor to determine the evaluation index for the combustion and explosion characteristics of the combustible working substance to be evaluated.

[0067] Since CH4 is currently the most thoroughly studied substance with relatively accurate parameters, it is used as the base. Taking the ratio of each working fluid to CH4 can offset the influence of units on the dimensionless parameter. Considering that the safety classification of combustible working fluids is primarily based on combustion limits, with combustion rate and heat of combustion as secondary factors, all three are included in the construction of the dimensionless parameter. Given that higher combustion rates and lower minimum ignition energies indicate lower safety for the working fluid, the minimum ignition energy can be placed in the numerator, and the combustion rate in the denominator, multiplied by the heat of combustion to obtain a dimensionless parameter.

[0068] Preferably, methane (CH4) can be used as a typical combustible working medium, and the combustion and explosion characteristic parameters of CH4 can be used as a benchmark. The combustion and explosion characteristic parameters of the combustible working medium to be evaluated can be compared with the corresponding combustion and explosion characteristic parameters of CH4 to obtain a set of dimensionless parameters. This set of dimensionless parameters can be used as evaluation index factors and calculated according to the following formula to obtain the evaluation index of the combustion and explosion characteristics of the combustible working medium to be evaluated:

[0069]

[0070] in:

[0071]

[0072]

[0073]

[0074] In the formula:

[0075] VEIN is an evaluation index for the combustion and explosion characteristics of combustible working fluids, also known as the velocity energy factor.

[0076] S u * This is the ratio of the combustion rate of the combustible working substance to be evaluated to the combustion rate of CH4;

[0077] MIE * This is the ratio of the minimum ignition energy of the combustible working fluid to be evaluated to the minimum ignition energy of CH4.

[0078] H C * The ratio of the heat of combustion of the combustible working substance to be evaluated to the heat of combustion of CH4;

[0079] S u R The combustion rate of the combustible working fluid to be evaluated;

[0080] The combustion rate of CH4;

[0081] MIE R The minimum ignition energy of the combustible working fluid to be evaluated;

[0082] This is the minimum ignition energy of CH4;

[0083] H C R The heat of combustion of the combustible working fluid to be evaluated;

[0084] The heat of combustion of CH4.

[0085] Preferably, the velocity energy factor of the combustible working substance to be evaluated can be combined with its lower ignition limit concentration characteristic parameter to obtain the comprehensive evaluation index (CEI) of the combustion and explosion characteristics of the combustible working substance to be evaluated according to the following formula:

[0086] CEI = LFL * ln(1 + VEIN);

[0087] LFL is the lower ignition limit concentration characteristic parameter value of the combustible working substance to be evaluated;

[0088] CEI is a comprehensive evaluation index for the combustion and explosion characteristics of the combustible working medium to be evaluated.

[0089] Based on the VEIN parameters mentioned above, and combined with the LFL-proposed comprehensive evaluation index (CEI), the evaluation capability of this combustion and explosion characteristic evaluation index can be better demonstrated.

[0090] Preferably, the VEIN value of CH4 is set to 1, and the CEI of CH4 is calculated to be 0.69. Combustible working substances can be divided into Class A, Class B, and Class C according to the CEI value; among them, combustible working substances with CEI≥5 are Class C; combustible working substances with 5>CEI>0.7 are Class B; and combustible working substances with CEI≤0.7 are Class A.

[0091] Preferably, the combustion rate can be predicted by the type and number of molecular groups.

[0092] Preferably, the combustion rate can be predicted using the following linear fitting formula:

[0093] S u，max =47.773-0.843R C-C +7.937R C＝C +4.386R ＝O +5.332R -O- -12.717R -NH2 -22.400R CF -44.937R CF2 -107.444R CF3

[0094] In the formula:

[0095] S u，max The maximum combustion rate of the combustible working fluid to be evaluated;

[0096] R C-C This represents the number of carbon atoms in a single-bonded carbon molecule.

[0097] R C＝C The number of carbon atoms in a double-bonded carbon molecule;

[0098] R ＝O The number of double-bonded oxygen groups in the molecule;

[0099] R -O- The number of single-bonded oxygen groups in the molecule;

[0100] R -NH2 The number of nitrogen-containing groups in the molecule;

[0101] R CF The number of CF groups;

[0102] R CF2 The number of CF2 groups;

[0103] R CF3 This represents the number of CF3 groups.

[0104] Preferably, a multiple linear regression algorithm can be used to perform regression calculations on the minimum ignition energy data.

[0105] Preferably, the minimum ignition energy can be calculated using the following formula:

[0106] lg(MIE)=0.011+0.003MW+0.104DM-12.801ε HOMO -33.641ε LUMO -106.725ω+0.136SP+0.086n C +0.018n H -0.296n F ;

[0107] In the formula:

[0108] MIE stands for Minimum Ignition Energy;

[0109] MW is the molecular weight;

[0110] DM stands for dipole moment; the dipole moment is the product of the distance between the centers of positive and negative charges and the charge on the center of charge. It is a vector, and its direction is defined as pointing from the center of positive charge to the center of negative charge. It is represented by the symbol μ and its unit is D (Debye).

[0111] SP represents the energy of a single molecular structure.

[0112] n C The number of carbon atoms;

[0113] n H The number of hydrogen atoms;

[0114] n F The number of fluorine atoms;

[0115] ε HOMO It is a HOMO energy level;

[0116] ε LUMO It is the LUMO energy level;

[0117] HOMO represents the highest occupied orbital of a molecule, while LUMO represents the lowest unoccupied orbital. The energy gap between them is denoted by Egap.

[0118] The HOMO level reflects the strength of a molecule's electron affinity. According to Koop Manns' theorem, a negative HOMO level represents the first ionization energy of the substance. The lower the ionization energy, the higher the HOMO level, and the easier it is for the substance to lose electrons. On the other hand, the LUMO level is numerically equivalent to the electron affinity of a molecule. The lower the LUMO level, the easier it is for the substance to gain electrons.

[0119] Among them, MW, DM, SP, n C n H Positively correlated with MIE value; n F ε HOMO ε LUMO It is negatively correlated with the MIE value.

[0120] The present invention also provides a combustible working medium combustion and explosion characteristic evaluation index system. The system is constructed using the above-mentioned combustible working medium combustion and explosion characteristic evaluation index construction method. The system takes CH4 combustion and explosion characteristic parameters and the combustion and explosion characteristic parameters of the combustible working medium to be evaluated as inputs, and outputs the combustion and explosion characteristic evaluation index of the combustible working medium to be evaluated.

[0121] The system uses a calculation module to perform the following formula to obtain the evaluation index of the combustion and explosion characteristics of the combustible working medium to be evaluated:

[0122]

[0123] in:

[0124]

[0125]

[0126]

[0127] In the formula:

[0128] VEIN is an evaluation index for the combustion and explosion characteristics of combustible working fluids, also known as the velocity factor.

[0129] S u * The ratio of the combustion rate of the combustible working substance to be evaluated to the combustion rate of CH4;

[0130] MIE * This is the ratio of the minimum ignition energy of the combustible working fluid to be evaluated to the minimum ignition energy of CH4.

[0131] H C *The ratio of the heat of combustion of the combustible working substance to be evaluated to the heat of combustion of CH4;

[0132] S u R The combustion rate of the combustible working fluid to be evaluated;

[0133] The combustion rate of CH4;

[0134] MIE R The minimum ignition energy of the combustible working fluid to be evaluated;

[0135] This is the minimum ignition energy of CH4;

[0136] H C R The heat of combustion of the combustible working fluid to be evaluated;

[0137] The heat of combustion of CH4.

[0138] This system combines the velocity energy factor of the combustible material to be evaluated with its lower ignition limit concentration characteristic parameter, and can obtain the comprehensive evaluation index (CEI) of the combustion and explosion characteristics of the combustible material to be evaluated according to the following formula:

[0139] CEI = LFL * ln(1 + VEIN);

[0140] LFL is the lower ignition limit concentration characteristic parameter value of the combustible working substance to be evaluated;

[0141] CEI is a comprehensive evaluation index for the combustion and explosion characteristics of the combustible working medium to be evaluated.

[0142] This system can predict the combustion rate by the type and number of molecular groups.

[0143] Preferably, the system can predict the combustion rate using the following linear fitting formula:

[0144] S u，max =47.773-0.843R C-C +7.937R C＝C +4.386R ＝O +5.332R -O- -12.717R -NH2 -22.400R CF -44.937R CF2 -107.444R CF3

[0145] In the formula:

[0146] S u，max The maximum combustion rate of the combustible working fluid to be evaluated;

[0147] R C-C This represents the number of carbon atoms in a single-bonded carbon molecule.

[0148] R C＝C The number of carbon atoms in a double-bonded carbon molecule;

[0149] R ＝O The number of double-bonded oxygen groups in the molecule;

[0150] R -O- The number of single-bonded oxygen groups in the molecule;

[0151] R -NH2 The number of nitrogen-containing groups in the molecule;

[0152] R CF The number of CF groups;

[0153] R CF2 The number of CF2 groups;

[0154] R CF3 This represents the number of CF3 groups.

[0155] Preferably, the system can use a multiple linear regression algorithm to perform regression calculations on the minimum ignition energy data.

[0156] Preferably, the system can calculate the minimum ignition energy according to the following formula:

[0157] lg(MIE)=0.011+0.003MW+0.104DM-12.801ε HOMO -33.641ε LUMO -106.725ω+0.136SP+0.086n C +0.018n H -0.296n F ;

[0158] In the formula:

[0159] MW is the molecular weight;

[0160] DM stands for dipole moment; the dipole moment is the product of the distance between the centers of positive and negative charges and the charge on the center of charge. It is a vector, and its direction is defined as pointing from the center of positive charge to the center of negative charge. It is represented by the symbol μ and its unit is D (Debye).

[0161] SP represents the energy of a single molecular structure.

[0162] n C The number of carbon atoms;

[0163] n H The number of hydrogen atoms;

[0164] n F The number of fluorine atoms;

[0165] ε HOMO It is a HOMO energy level;

[0166] ε LUMO It is the LUMO energy level;

[0167] HOMO represents the highest occupied orbital of a molecule, while LUMO represents the lowest unoccupied orbital. The energy gap between them is denoted by Egap.

[0168] The system can have a built-in calculation module, or it can use applicable calculation modules or functional modules in the existing technology to calculate the above formula; or it can use software in the existing technology, and write a program according to the software programming manual and using conventional technical means to calculate the above formula.

[0169] The working principle of the present invention will be further explained below with reference to a preferred embodiment:

[0170] like Figure 1 As shown, a method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working substances is proposed. The method uses the combustion and explosion characteristic parameters of a typical combustible working substance as a benchmark, and uses the ratio of the combustion and explosion characteristic parameters of the combustible working substance to be evaluated to the combustion and explosion characteristic parameters of the typical combustible working substance as an evaluation index factor to determine the evaluation index for the combustion and explosion characteristics of the combustible working substance to be evaluated.

[0171] Using the combustion and explosion characteristics of CH4 as a benchmark, the combustion and explosion characteristics of the combustible working medium to be evaluated are compared with the corresponding combustion and explosion characteristics of CH4 to obtain a set of dimensionless parameters. This set of dimensionless parameters is used as evaluation index factors and calculated according to the following formula to obtain the evaluation index of the combustion and explosion characteristics of the combustible working medium to be evaluated:

[0172]

[0173] in:

[0174]

[0175]

[0176]

[0177] In the formula:

[0178] VEIN is an evaluation index for the combustion and explosion characteristics of combustible working fluids, also known as the velocity factor.

[0179] S u * The ratio of the combustion rate of the combustible working substance to be evaluated to the combustion rate of CH4;

[0180] MIE * This is the ratio of the minimum ignition energy of the combustible working fluid to be evaluated to the minimum ignition energy of CH4.

[0181] H C * The ratio of the heat of combustion of the combustible working substance to be evaluated to the heat of combustion of CH4;

[0182] S u R The combustion rate of the combustible working fluid to be evaluated;

[0183] The combustion rate of CH4;

[0184] MIE R The minimum ignition energy of the combustible working fluid to be evaluated;

[0185] This is the minimum ignition energy of CH4;

[0186] H C R The heat of combustion of the combustible working fluid to be evaluated;

[0187] The heat of combustion of CH4.

[0188] VEIN is derived from three typical combustion and explosion parameters: minimum ignition energy, combustion rate, and heat of combustion. This parameter is obtained by averaging the rate of change of minimum ignition energy and combustion rate with respect to concentration, and then corrected for by heat of combustion to offset their relationship with concentration. This ensures that the VEIN index for different working fluids does not change with concentration or equivalence ratio. CEI, on the other hand, incorporates the LFL parameter, which does not change with concentration, making it even more representative. This invention collected 70 sets of data on minimum ignition energy, combustion rate, heat of combustion, and LFL of working fluids, and derived CEI values ​​using the above calculation method. Table 1 shows the CEI indexes of common combustible working fluids.

[0189] Table 1. Statistics of CEI parameters for common working fluids

[0190]

[0191]

[0192]

[0193] Based on the results above, a preliminary classification standard is established: using the product of CH4 as the base and taking its VEIN value as 1, the CEI is calculated to be 0.69. The working fluids of categories A, B, and C are distinguished based on the changes in CEI: The distinction between categories B and C is relatively simple, as a CEI of 5 is sufficient for differentiation, and their variation is significant. The variation between categories A and B is smaller, and the classification standard is set at CEI = 0.7. According to the ISO 817 classification standard, the essential difference between category A2 and category A3 working fluids is small, and the comparison of CEI data confirms this small difference, making them difficult to distinguish. In summary, category A consists of working fluids with CEI ≤ 0.7, category B consists of working fluids with 0.7 < CEI < 5, and category C consists of working fluids with CEI ≥ 5.

[0194] After the new working fluids are classified into three categories, combustion rate and minimum ignition energy have a significant impact on CEI. The main difference in minimum ignition energy is that it starts at around 1.0 mJ for R161 and CH4, gradually increasing to over 1 mJ for categories B and C, a difference of an order of magnitude, which has a significant impact on the overall CEI value. Therefore, setting CH4 and R152a as the boundary can fully demonstrate the difference between categories A and B. The table also indicates the original ISO 817-2014 standard's classification of the above working fluids. It can be seen that the CEI testing standard is basically consistent with the ISO classification, and the CEI considers combustion rate, ignition energy, and heat of combustion, which has higher accuracy and reliability compared to the original evaluation standard that mainly focused on LFL and heat of combustion.

[0195] Figure 2 and Figure 3 The diagram illustrates the relationship between the Comprehensive Evaluation Index (CEI) and combustion rate and minimum ignition energy. Two lines, CEI=0.7 and CEI=5, are highlighted, represented by solid and dashed lines respectively, serving as boundaries for different working fluid categories. The comparison reveals that, consistent with previous findings, CEI and combustion rate are approximately inversely proportional; a higher combustion rate results in a lower CEI and a lower safety factor. Conversely, CEI and minimum ignition energy are approximately directly proportional; a higher minimum ignition energy results in a higher CEI and a higher safety factor. The comparison of CEI and these two parameters also demonstrates that both are highly representative of combustion and explosion parameters, and together they can indicate the safety and hazard of combustible working fluids.

[0196] In summary, the introduction of VEIN and CEI parameters provides a novel perspective for determining and comparing the combustion and explosion parameters of working fluids, and from this perspective, it gives a classification of the combustion and explosion parameters of working fluids, providing a basis for studying the safety performance of working fluids.

[0197] The embodiments described above are only used to illustrate the technical ideas and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The patent scope of the present invention should not be limited by these embodiments. That is, any equivalent changes or modifications made in accordance with the spirit disclosed in the present invention still fall within the patent scope of the present invention.

Claims

1. A method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working fluids, characterized in that, The combustion and explosion characteristics of a typical combustible working medium are used as a benchmark, and the ratio of the combustion and explosion characteristics of the combustible working medium to be evaluated to the combustion and explosion characteristics of the typical combustible working medium is used as an evaluation index factor to determine the evaluation index of the combustion and explosion characteristics of the combustible working medium to be evaluated. Specific methods include: Using the combustion and explosion characteristics of CH4 as a benchmark, the combustion and explosion characteristics of the combustible working medium to be evaluated are compared with the corresponding combustion and explosion characteristics of CH4 to obtain a set of dimensionless parameters. This set of dimensionless parameters is used as evaluation index factors and calculated according to the following formula to obtain the evaluation index of the combustion and explosion characteristics of the combustible working medium to be evaluated: in: In the formula: VEIN is an evaluation index for the combustion and explosion characteristics of combustible working fluids, also known as the velocity energy factor. S u * This is the ratio of the combustion rate of the combustible working substance to be evaluated to the combustion rate of CH4; MIE * This is the ratio of the minimum ignition energy of the combustible working fluid to be evaluated to the minimum ignition energy of CH4. H C * The ratio of the heat of combustion of the combustible working substance to be evaluated to the heat of combustion of CH4; S u R The combustion rate of the combustible working fluid to be evaluated; The combustion rate of CH4; MIE R The minimum ignition energy of the combustible working fluid to be evaluated; This is the minimum ignition energy of CH4; H C R The heat of combustion of the combustible working fluid to be evaluated; The heat of combustion of CH4; By combining the velocity energy factor of the combustible working substance to be evaluated with its lower ignition limit concentration characteristic parameter, the comprehensive evaluation index (CEI) of the combustion and explosion characteristics of the combustible working substance to be evaluated is obtained according to the following formula: CEI = LFL * ln(1 + VEIN); LFL is the lower ignition limit concentration characteristic parameter value of the combustible working substance to be evaluated; CEI is a comprehensive evaluation index for the combustion and explosion characteristics of the combustible working medium to be evaluated. Assuming the VEIN value of CH4 is 1, the calculated CEI of CH4 is 0.

69. Based on the CEI value, combustible working substances are divided into three categories: A, B, and C. Combustible working substances with CEI ≥ 5 are classified as category C; combustible working substances with 5 > CEI > 0.7 are classified as category B; and combustible working substances with CEI ≤ 0.7 are classified as category A.

2. The method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working fluids according to claim 1, characterized in that, Combustion rate is predicted by the type and number of molecular groups.

3. The method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working fluids according to claim 2, characterized in that, Combustion rate is predicted using the following linear fitting formula: S u,max =47.773-0.843R C-C +7.937R C＝C +4.386R ＝O +5.332R -O- -12.717R -NH2 -22.400R CF -44.937R CF2 -107.444R CF3 In the formula: S u,max The maximum combustion rate of the combustible working fluid to be evaluated; R C-C The number of carbon atoms in a single-bonded carbon molecule; R C=C The number of carbon atoms in a double-bonded carbon molecule; R =O The number of double-bonded oxygen groups in the molecule; R -O- The number of single-bonded oxygen groups in the molecule; R -NH2 The number of nitrogen-containing groups in the molecule; R CF The number of CF groups; R CF2 The number of CF2 groups; R CF3 This represents the number of CF3 groups.

4. The method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working fluids according to claim 1, characterized in that, The minimum ignition energy data were regressed using a multiple linear regression algorithm.

5. The method for constructing evaluation indicators for the combustion and explosion characteristics of combustible working fluids according to claim 4, characterized in that, The minimum ignition energy is calculated using the following regression formula: lg(MIE)=0.011+0.003MW+0.104DM-12.801ε HOMO -33.641ε LUMO -106.725ω+0.136SP+0.086n C +0.018n H -0.296n F ; In the formula: MIE stands for Minimum Ignition Energy; MW is the molecular weight; DM is a dipole moment; ω It is the eccentricity factor; SP represents the energy of a single molecular structure. n C The number of carbon atoms; n H The number of hydrogen atoms; n F The number of fluorine atoms; ε HOMO It is a HOMO energy level; ε LUMO It is the LUMO energy level; MW, DM, SP n C , n H Positively correlated with MIE value; n F ε HOMO ε LUMO It is negatively correlated with the MIE value.

6. A system for evaluating the combustion and explosion characteristics of combustible working fluids, characterized in that, The system is constructed using the method for constructing evaluation indexes of combustible working medium combustion and explosion characteristics as described in any one of claims 1 to 5. The system takes into account the combustion and explosion characteristic parameters of CH4 and the combustion and explosion characteristic parameters of the combustible working medium to be evaluated, and outputs the evaluation indexes of the combustion and explosion characteristics of the combustible working medium to be evaluated.

Images