Gas pipeline leakage heat radiation prediction method based on terrain and temperature correction

Abstract

The invention relates to a gas pipeline safety protection problem, in particular to a gas pipeline leakage heat radiation prediction method based on terrain and temperature correction. The method comprises the following steps: acquiring pipeline design parameters and surrounding environment data, calculating a gas leakage flow rate Q according to the pipeline design parameters and the surrounding environment data, and calculating a heat release rate Q'according to the gas leakage flow rate Q; constructing a landform correction factor calculation model according to absorption, heat conduction and reflection characteristics of a surface material around the pipeline; importing the landform correction factor calculation model into the basic multi-point source model for iteration until convergence, and obtaining the total radiation intensity obtained by convergence; and correcting the total radiation intensity obtained by convergence based on the difference value between the actual temperature and the standard environment temperature to obtain the final total radiation intensity. The method can accurately predict the thermal radiation intensity distribution of the gas pipeline under the conditions of complex terrains and different environment temperatures, and further accurately assesses the damage range and the influence area of thermal radiation in a fire blast accident.

Description

Technical Field

[0001] The invention relates to the problem of safety protection of gas pipelines, and in particular to a method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction. Background Art

[0002] Gas (hydrogen, natural gas, etc.) is highly explosive and rapidly diffuses. Leakage or rupture of gas pipelines may cause serious fires and explosions. Leakage easily forms explosive mixed gases, causing large-scale thermal radiation hazards. Therefore, establishing an accurate prediction model for the thermal radiation intensity of gas pipelines is of great guiding significance for assessing the scope of explosion hazards and setting safe distances.

[0003] Topography and ambient temperature are key environmental factors that affect the heat radiation hazards of gas pipeline explosions. Topography (such as mountains, river valleys, etc.) will change the propagation path of thermal radiation, and the reflection, absorption and thermal conductivity characteristics of different landforms significantly affect the distribution of thermal radiation, making its attenuation characteristics more uncertain under complex terrain conditions. Changes in ambient temperature will also affect the combustion intensity and radiation calorific value. High temperature conditions will increase the radiation intensity and expand the scope of harm.

[0004] However, current research on the effects of terrain and temperature on thermal radiation is still insufficient. Traditional models are based on the assumption of idealized and uniform topography, and only consider the temperature changes of the flame itself, ignoring the influence of ambient temperature. It is difficult to accurately describe the thermal radiation characteristics under complex terrain and changing environments, resulting in deviations in prediction results in practical applications.

[0005] Therefore, a gas pipeline thermal radiation prediction method based on terrain and temperature correction is urgently needed to improve the accuracy and applicability of the prediction and provide a scientific basis for the safety protection of gas pipelines. Summary of the invention

[0006] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction, which can accurately predict the distribution of thermal radiation intensity of gas pipelines under complex terrain and different ambient temperature conditions, and then accurately evaluate the hazard range and impact area of ​​thermal radiation in combustion and explosion accidents.

[0007] In order to solve the above technical problems, the technical solution of the present invention is: a method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction, comprising:

[0008] Obtain pipeline design parameters and surrounding environment data, calculate the gas leakage flow rate Q according to the pipeline design parameters and surrounding environment data, and calculate the heat release rate Q' according to the gas leakage flow rate Q;

[0009] According to the absorption, thermal conductivity and reflection characteristics of the surface materials around the pipeline, a calculation model for the topography correction factor is constructed;

[0010] The topography correction factor calculation model is imported into the basic multi-point source model for iteration until convergence, and the converged total radiation intensity is obtained;

[0011] The converged total radiation intensity is corrected based on the difference between the actual temperature and the standard ambient temperature to obtain the final total radiation intensity.

[0012] Furthermore, a topography correction factor calculation model is constructed based on the absorption, thermal conductivity and reflection characteristics of the surface materials around the pipeline; specifically:

[0013] According to the area where the pipeline is located, determine the surrounding surface materials with a percentage exceeding the threshold through geographic information system or on-site survey;

[0014] Determine the comprehensive characteristic parameters of the surface materials whose proportion exceeds the threshold; wherein the comprehensive characteristic parameters include absorption coefficient α, thermal conductivity λ and reflection coefficient ρ;

[0015] Combining the acquired comprehensive characteristic parameters with the viewing angle factors in the basic multi-point source model, a landform correction factor calculation model is constructed.

[0016] Furthermore, the calculation model of the landform correction factor is:

[0017]

[0018] In the formula, f j,terrain is the topographic correction factor of the jth point source, α is the absorption coefficient of the material; F is the viewing factor; λ is the thermal conductivity of the surface material; q j Represents the thermal radiation intensity of the jth point source, in KW / m 2 ; ρ is the reflection coefficient of the material.

[0019] Furthermore, the topography correction factor calculation model is imported into the basic multi-point source model for iteration. The iteration formula is:

[0020]

[0021] In the formula, is the i-th calculation result of the topographic correction factor of the j-th point source, q (i-1) ,q (i) are the thermal radiation intensities calculated for the j-th point source for the i-1th and i-th times respectively.

[0022] Furthermore, the basic multi-point source model is:

[0023]

[0024] Among them, q0 is the total thermal radiation intensity of the basic model q0; w j is the weight of the jth point source, N is the total number of point sources; τ j is the atmospheric transmittance; is the radiation fraction; Q' is the heat release rate; is the distance between the jth point and the target point, cosθ T,j is the cosine value of the angle between the line connecting each two points and the external normal of the target object, that is, the viewing angle factor; N is the number of point sources; n is the total number of point sources of multiple point sources, and the calculation formula for the initial radiation intensity of the jth point source is

[0025] Furthermore, the converged total radiation intensity is corrected based on the difference between the actual temperature and the standard ambient temperature; the specific formula is:

[0026]

[0027] Among them, q final is the final total radiation intensity, q (K) is the converged total radiation intensity, T0 is the standard ambient temperature; ΔT is the difference between the actual ambient temperature and the standard ambient temperature T0.

[0028] The present invention also provides a method for predicting the damage range of gas pipeline leakage based on terrain and temperature correction, and adopts a method for predicting the thermal radiation of gas pipeline leakage based on terrain and temperature correction to predict the final total radiation intensity received by each target point;

[0029] Based on the final total radiation intensity, the damage range and safety distance are predicted; specifically:

[0030] E final =q final ·A

[0031]

[0032] E final is the total radiation per unit time of the improved radiation source; A is the area of ​​the radiation source (pipeline leakage jet fire); q final is the final total radiation intensity; R final is the distance from the center of the radiation source to the target point, that is, the safety distance radius; τ j is the atmospheric transmittance, I(r) is the thermal radiation intensity at a certain point in space, that is, the thermal radiation value threshold.

[0033] After adopting the above technical solution, the present invention introduces terrain correction factor and temperature correction when calculating the thermal radiation intensity, comprehensively considering the attenuation effect of terrain on the thermal radiation propagation path and intensity, and the amplification effect of ambient temperature on combustion intensity and radiation intensity, thereby significantly improving the accuracy of thermal radiation intensity prediction. This method improves the accuracy of prediction, helps to more effectively evaluate the scope of thermal radiation hazards in gas pipeline explosion accidents, and provides a scientific basis for formulating safety distances and protective measures. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of the method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction of the present invention;

[0035] Figure 2 It is a comparison diagram of the radiation intensity calculation results of the embodiment of the present invention, the comparative example and the actual accident report data;

[0036] Figure 3 Comparison chart of thermal radiation intensity data between basic model, improved model and actual accident;

[0037] Figure 4 This is a comparison chart of the errors between the model and the actual data before and after improvement. DETAILED DESCRIPTION

[0038] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments in conjunction with the accompanying drawings.

[0039] like Figure 1 As shown, a method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction includes:

[0040] Step S1, obtaining pipeline design parameters and surrounding environment data, calculating the gas leakage flow rate Q according to the pipeline design parameters and the surrounding environment data, and calculating the heat release rate Q' according to the gas leakage flow rate Q;

[0041] In this step, the gas leakage flow rate Q is calculated according to the pipeline design parameters and the surrounding environment data, which is the prior art. For details, see the Chinese patent with application number 201910830368.3, and the patent name is a method for predicting the range of jet flames in a gas pipeline; the heat release rate Q' is calculated according to the gas leakage flow rate Q, which is also the prior art. For details, see "A consideration of methods of determining the radiative characteristics of jet fires" by HANKINSON G.

[0042] Step S2, constructing a topography correction factor calculation model based on the absorption, thermal conductivity and reflection characteristics of the surface materials around the pipeline; specifically:

[0043] Step S21, according to the region where the pipeline is located, determine the surrounding surface materials with a proportion exceeding a threshold through a geographic information system (GIS) or on-site survey, that is, the main material types of the surrounding surface, such as rock, soil, vegetation, water, etc.;

[0044] Step S22, determine the comprehensive characteristic parameters of the main materials of the surrounding surface. When the proportion of the surrounding surface materials is more than one, calculate the comprehensive characteristic parameters based on the area ratio of each material (weighted average method) to determine the final landform correction factor. For details, refer to the reports on the thermal properties of soil and natural materials issued by the United States Geological Survey (USGS), NASA, the European Space Agency (ESA), etc., as well as the Chinese Soil Society, the Civil Engineering Manual, etc. Among them, the comprehensive characteristic parameters include the absorption coefficient α, the thermal conductivity coefficient λ and the reflection coefficient ρ;

[0045] When there is more than one type of surrounding surface material, the proportional weighted method is used to calculate the comprehensive characteristic parameters. The specific calculation formula is as follows:

[0046]

[0047] in:

[0048] P 综合 , comprehensive characteristic parameters, such as absorption coefficient, thermal conductivity or reflection coefficient;

[0049] P t , characteristic parameters of the tth material;

[0050] W t , the area proportion of the tth material satisfies

[0051] In practical applications, the area ratio data of each material can be obtained through geographic information system (GIS) or on-site survey, and the comprehensive characteristic parameters can be calculated based on the thermal properties of the material (such as absorption, thermal conductivity and reflection coefficient). This method can better reflect the overall response of the multi-material mixed area to thermal radiation.

[0052] Step S23, combining the acquired comprehensive characteristic parameters with the viewing angle factor in the basic multi-point source model to construct a terrain correction factor calculation model.

[0053] In this step, according to the physical principles of absorption, reflection and heat conduction, a topography correction factor calculation model is constructed, including absorption term, thermal conduction term and reflection term, which respectively correspond to the thermal response characteristics of the material in different aspects.

[0054] The absorption term describes the material's ability to absorb incident thermal radiation and is related to the material's absorption coefficient α and view factor F. The absorption coefficient α represents the material's absorption capacity, and different materials (such as soil and rock) have different absorption coefficients. The view factor F reflects the geometric relationship between the heat source and the material surface, and determines the effective visibility of the material surface to the heat source.

[0055] The thermal conductivity term describes the ability of a material to conduct heat to the inside after absorbing it. Materials with higher thermal conductivity will conduct the absorbed heat to the inside faster, resulting in a lower surface temperature rise, which leads to a decrease in the efficiency of absorbing radiation energy. The higher the thermal conductivity, the slower the surface temperature rises after the material absorbs heat, showing the so-called "thermal inertia". In order to describe the relationship between the decreasing efficiency of the material absorbing heat and the increase of thermal conductivity λ, the ln function is used to express this decreasing trend, and the thermal conductivity response term is:

[0056]

[0057] Where λ is the thermal conductivity of the material on the surface, W / (m·K); q is the incident radiation intensity, KW / ㎡; and F is the viewing factor. When λ or I is small, the material absorbs more heat and responds faster. When λ or I is large, the thermal response of the material tends to saturation, and the surface temperature rises slowly, thereby reducing the actual absorption of radiation.

[0058] The reflection term describes the material's ability to reflect thermal radiation, and is related to the material's reflection coefficient ρ and the viewing angle factor (1-F). The reflection coefficient ρ represents the material's ability to reflect radiation, and satisfies α+ρ=1 with the absorption coefficient. The viewing angle factor correction term (1-F) is used to correct the reflection ratio of the material under different geometric conditions. When the viewing angle is small, the reflection increases. The reflection term can be expressed as:

[0059] ρ·(1-F)

[0060] Among them, ρ is the reflection coefficient of the material and F is the viewing factor.

[0061] In practical applications, the absorption behavior and thermal conductivity behavior of materials are interdependent. Therefore, multiplying the absorption term by the thermal conductivity response term can more accurately describe the absorption effect of the material under different thermal conductivity conditions. If the thermal conductivity is low, the heat absorbed by the material will accumulate on the surface, and the absorption effect will be stronger; if the thermal conductivity is high, the heat will be conducted to the inside faster, resulting in a weakened surface absorption effect. At the same time, in order to express the complementary relationship between absorption and reflection in physics, subtracting the reflection term can ensure that the structure of the entire formula conforms to the principle of conservation of energy, that is, the total amount of thermal radiation received by the material is either absorbed or reflected, ensuring the accuracy of the material's response to thermal radiation.

[0062] In summary, the calculation model of the topography correction factor of a single point source (the jth point source) is:

[0063]

[0064] Among them, f j,terrain is the topographic correction factor of a single point source, α is the absorption coefficient of the material; F is the viewing factor; λ is the thermal conductivity of the surface material, W / (m·K); q j is the thermal radiation intensity of the jth point source, KW / ㎡; ρ is the reflection coefficient of the material;

[0065] Step S3, importing the topography correction factor calculation model into the basic multi-point source model for iteration until convergence, and obtaining the converged total radiation intensity;

[0066] Among them, the basic multi-point source model is:

[0067]

[0068] Among them, q0 is the total thermal radiation intensity of the basic model, KW / ㎡; w j is the weight of the jth point source, N is the total number of point sources; τ j is the atmospheric transmittance, which is generally taken as 1; is the radiation fraction, which is determined according to the fuel type. Natural gas is generally taken as 0.2, and hydrogen is generally taken as 0.05; Q' is the heat release rate, kw; is the distance between the jth point and the target point, m, cosθ T,j is the cosine value of the angle between the line connecting each two points and the external normal of the target object, that is, the viewing angle factor; N is the number of point sources; n is the total number of point sources of multiple point sources.

[0069] Take q0 as the initial iteration value of thermal radiation q (0) , the topography correction factor is introduced into the multi-point source model, and the total thermal radiation intensity is iterated until convergence: the calculation formula of the initial radiation intensity of the j-th point source is

[0070] The following is the iterative process. In the first iteration, the initial thermal radiation intensity of each point source is calculated.

[0071]

[0072] q0 is the thermal radiation intensity calculated in the first iteration, indicating the initial total thermal radiation intensity; w j is the weight of the jth point source; T j is the temperature of the jth point source; X is the atmospheric transmittance, which is generally taken as 1; Q′ is the heat release rate, which indicates the heat release rate of each point source; cosθ j is the viewing angle factor between the j-th point source and the target point, which represents the angle between the line from the target point to the j-th point source and the external normal of the target point; Rj is the distance from the jth point source to the target point; N is the total number of point sources;

[0073] The total thermal radiation intensity is obtained by superposition:

[0074]

[0075] Then calculate the topographic correction factor for each point source:

[0076]

[0077] is the topographic correction factor of the first iteration of the j-th point source; α is the absorption coefficient; F is the viewing factor; is the initial radiation intensity of the jth point source, and the calculation formula is ρ is the reflection coefficient; λ is the thermal conductivity of the surface material;

[0078] The radiation intensity of each point source is then corrected using the topographic correction factor of each point source:

[0079]

[0080] Finally, all corrected point source radiation intensities are accumulated to obtain the total radiation intensity:

[0081]

[0082] Second iteration, first calculate the topographic correction factor of each point source For each point source j, the radiation intensity obtained in the first iteration is

[0083]

[0084] The initial radiation intensity of the j-th point source is The corresponding terrain correction factor Multiply them together to get the updated radiation intensity:

[0085]

[0086] The radiation intensity of all point sources Adding them up, we get the total radiation intensity for the second iteration:

[0087]

[0088] Iterate for i times until convergence, first use the radiation intensity obtained by i-1 iterations Based on, calculate the terrain correction factor of the i-th iteration:

[0089]

[0090] The radiation intensity of the j-th point source in the i-1th iteration The corresponding terrain correction factor Multiply them together to get the updated radiation intensity:

[0091]

[0092] The radiation intensity of all point sources Accumulate and get the total radiation intensity of the i-th iteration:

[0093]

[0094] Among them, q (i) is the total thermal radiation intensity obtained in the i-th iteration, i=1,2,3...,KW / ㎡; is the topographic factor obtained in the i-th iteration, i = 1, 2, 3...K, K is the number of iterations until convergence; w j is the weight of the j-th point source; τ j is the atmospheric transmittance, usually 1, x r is the radiation fraction, which is determined according to the fuel type. Natural gas is generally taken as 0.2, and hydrogen is generally taken as 0.05; Q' is the heat release rate, kw; is the distance between the jth point and the target point, m, cosθ T,j is the cosine value of the angle between the line connecting each two points and the external normal of the target object, that is, the viewing factor; N is the number of point sources; n is the total number of point sources of multiple point sources; α is the absorption coefficient of the material; cosθ T,j is the cosine value of the angle between the line connecting each two points and the external normal of the target object, that is, the viewing factor; ρ is the reflection coefficient of the material.

[0095] Step S4, correcting the converged total radiation intensity based on the difference between the actual temperature and the standard ambient temperature to obtain a final total radiation intensity.

[0096] Where the actual ambient temperature is T, the standard ambient temperature T0 = 298K, then the temperature difference ΔT = (T-298). According to the Stefan-Boltzmann law, the radiation intensity E is proportional to the fourth power of the temperature T:

[0097] E=σT 4

[0098] At the standard ambient temperature T0, the radiation intensity is E0; in actual applications, the ambient temperature will change, especially high temperature will enhance the thermal radiation intensity. If the temperature changes to T = T0 + ΔT, the radiation intensity will become:

[0099] E=σ(T0+ΔT) 4

[0100] (T0+ΔT) 4 Perform Taylor expansion and retain the first-order term to approximate:

[0101]

[0102] The final ambient temperature correction formula is:

[0103]

[0104] Among them, q final is the final total thermal radiation intensity, q (K) is the total thermal radiation intensity obtained after the Kth iteration until convergence; T0 is the standard ambient temperature, which is 298K; ΔT is the difference between the actual ambient temperature and the standard ambient temperature T0 (298K), k.

[0105] A method for predicting the damage range of gas pipeline leakage based on terrain and temperature correction, comprising:

[0106] The final total radiation intensity received by each target point is predicted by using the gas pipeline leakage thermal radiation prediction method based on terrain and temperature correction in the above embodiment;

[0107] Based on the final total radiation intensity, the damage range and safety distance are predicted; specifically:

[0108] Among them, the basic calorific value distance formula is:

[0109] E=Q·H c

[0110]

[0111] Where: E is the total radiation of the radiation source per unit time, kW; Q is the gas leakage rate, kg / s; H c is the combustion heat of the fuel, kJ / kg; R is the distance from the leakage point to the target point, m; I(r) is the thermal radiation intensity of a certain spatial point, KW / m 2 ; τ j is the atmospheric transmittance, which is generally taken as 1;

[0112] The improved distance formula is:

[0113] E final =q final ·A

[0114]

[0115] E final is the total radiation per unit time of the improved radiation source, kW; q finalis the final total radiation intensity, kW / m 2 ; A is the area of ​​the radiation source (pipeline leakage jet fire), m2; R final is the distance from the center point of the improved radiation source to the target point, m; I(r) is the thermal radiation intensity of a certain spatial point, that is, the thermal radiation value threshold, KW / m 2 .

[0116] It should be noted that the calculation method of parameter A and R final The calculation method of the geometric center point of the radiation source in (the distance from the center point of the improved radiation source, i.e. the center of the jet fire, to the target point) is an existing technology, see "Research on the Hazard Model of Jet Fire in Natural Gas Pipeline Failure", which will not be introduced in detail here. The reason for writing the center point of the radiation source instead of the pipeline leakage point is that when calculating the safety distance in the international standard, the impact of the jet fire volume is usually considered, and the geometric center point of the pipeline leakage jet fire is used as the standard instead of directly using the pipeline leakage point.

[0117] The solutions involved in the above embodiments are described in detail below in conjunction with specific embodiments.

[0118] Example:

[0119] like Figure 1 As shown, a method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction includes:

[0120] Step S1, collecting pipeline design parameters and surrounding environment data, calculating the gas leakage flow rate Q according to the pipeline design parameters and the surrounding environment data, and calculating the heat release rate Q' according to the gas leakage flow rate Q;

[0121] The embodiment is: at 9:00 am on July 30, 2004, a high-pressure gas pipeline (transmitting hydrogen) in an industrial area 40 km south of Brussels, the capital of Belgium, exploded. The pipeline had a diameter of 1000 mm, a material of X70, a wall thickness of 10 mm, a normal transmission pressure of 8 MPa, and a pipeline pressure of 7.3 MPa at the time of the accident. The range of minor injuries after the explosion was 1000 m.

[0122] According to the heat flux criteria for personal injury and equipment damage under thermal radiation, as shown in Table 1, the thermal radiation threshold for minor injury in the accident is determined to be 2kW / m 2 .

[0123] Table 1 Heat value injury threshold table

[0124]

[0125]

[0126] The calculated jet velocity is the speed of sound, the local speed of sound is 349 m / s, the leakage flow Q is 2940.7271 kg / s, and the heat release rate Q' is 4.9447 × 10 7 kw.

[0127] S2, the specific parameters of different surface materials are shown in Table 2:

[0128] Table 2 Specific parameters of different surface materials

[0129]

[0130] In the accident analysis, since the accident occurred in an industrial area, the surface materials are mostly hard materials (concrete or asphalt). These materials usually have medium to high thermal conductivity and absorption coefficient, and low reflectivity. Based on this, the material parameters of concrete and asphalt are comprehensively selected, the absorption coefficient α is 0.175, the thermal conductivity λ is 1.125W / (m·K), and the absorption coefficient ρ is 0.825. The calculation model of the topographic correction factor of the point source is:

[0131]

[0132] S3, import the terrain correction factor calculation model into the multi-point source model for iteration until convergence to obtain the corrected total radiation intensity:

[0133] The multi-point source model based on geomorphic factors was discretized by data processing software. The total number of point sources was taken as 260, and q0 was obtained as 12650323.27W / ㎡. is 0.9335, the fourth iteration converges, q (4) 6,603,741W / ㎡

[0134] S4, at 9:00 am on July 30, 2004, the temperature in the area south of Brussels, the capital of Belgium, was 30°C, ΔT was calculated to be 30k, and q was calculated to be final 9245238.53W / m 2 .

[0135] S5, predicts the damage range and safety distance based on the final total thermal radiation intensity.

[0136] The thermal radiation threshold is 2kW / m 2 , that is, I(r) is 2kW / m 2 , substituting into the distance formula, the light injury range is calculated to be 952.5m, which is 4.75% more than the actual injury range.

[0137] Comparative Example:

[0138] Using the basic model before correction, q0 is 34905.25W / ㎡, and the range of minor injuries is 898.114m, with an error of 10.19%.

[0139] Comparing the data of the embodiment and the comparative example, the error of the model calculation result of the embodiment (after correction) decreased by 5.44%. Figure 2 shown.

[0140] In addition, accident data under various combinations of conditions including typical slope angles (15°, 30°, 45°), height differences (5 meters, 10 meters, 20 meters), and wind speeds (2m / s, 5m / s, 10m / s) are also summarized. Through data comparison and analysis, the error of the model before improvement (comparative example) under various complex conditions increases with the complexity of the conditions. Compared with the basic model, the improved model (implementation example) of the present invention has higher accuracy in predicting radiation intensity. The improved model is more consistent with the accident data and can significantly reduce the error of radiation assessment under complex terrain. Comparison of radiation intensity of the basic model, improved model and actual accident data Figure 3 As shown in the figure, the error comparison between the model and the actual data before and after improvement is as follows Figure 4 shown.

[0141] The model formula constructed by the method of the present invention, on the basis of preliminary consideration of factors such as terrain and wind speed, further takes into account various complex conditions such as the geomorphic characteristics of the terrain and temperature. The model fully reflects the complex situation that is closer to reality through a concise formula form, and the various correction factors are well coupled, which promotes the accuracy of the setting of the safety protection distance of the gas pipeline.

[0142] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction, characterized in that: include: Obtain pipeline design parameters and surrounding environment data, calculate the gas leakage flow rate Q according to the pipeline design parameters and surrounding environment data, and calculate the heat release rate Q' according to the gas leakage flow rate Q; According to the absorption, thermal conductivity and reflection characteristics of the surface materials around the pipeline, a calculation model for the topography correction factor is constructed; The topography correction factor calculation model is imported into the basic multi-point source model for iteration until convergence, and the converged total radiation intensity is obtained; The converged total radiation intensity is corrected based on the difference between the actual temperature and the standard ambient temperature to obtain the final total radiation intensity.

2. The method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction according to claim 1 is characterized in that: According to the absorption, thermal conductivity and reflection characteristics of the surface materials around the pipeline, a calculation model for the topography correction factor is constructed; specifically: According to the area where the pipeline is located, determine the surrounding surface materials with a percentage exceeding the threshold through geographic information system or on-site survey; Determine the comprehensive characteristic parameters of the surface materials whose proportion exceeds the threshold; wherein the comprehensive characteristic parameters include absorption coefficient α, thermal conductivity λ and reflection coefficient ρ; Combining the acquired comprehensive characteristic parameters with the viewing angle factors in the basic multi-point source model, a landform correction factor calculation model is constructed.

3. The method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction according to claim 2 is characterized in that: The calculation model of the topographic correction factor of a single point source is: In the formula, f terrain is the topographic correction factor of the jth point source, α is the absorption coefficient of the material; F is the viewing factor; λ is the thermal conductivity of the surface material; q j represents the thermal radiation intensity of the jth point source; ρ is the reflection coefficient of the material.

4. The method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction according to claim 3 is characterized in that: The terrain correction factor calculation model is imported into the basic multi-point source model for iteration. The iteration formula is: In the formula, is the i-th calculation result of the topographic correction factor of the j-th point source, q (i-1) ,q (i) are the thermal radiation intensities calculated for the j-th point source for the i-1th and i-th times respectively.

5. The method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction according to claim 1 is characterized in that: The basic multi-point source model is: In j =jw1; Among them, q0 is the total thermal radiation intensity of the basic model q0; w j is the weight of the jth point source, N is the total number of point sources; τ j is the atmospheric transmittance; is the radiation fraction; Q' is the heat release rate; is the distance between the jth point and the target point, cosθ T,j is the cosine value of the angle between the line connecting each two points and the external normal of the target object, that is, the viewing angle factor; N is the number of point sources; n is the total number of point sources of multiple point sources, and the calculation formula for the initial radiation intensity of the jth point source is 6. The method for predicting thermal radiation of gas pipeline leakage based on terrain and temperature correction according to claim 1 is characterized in that: The converged total radiation intensity is corrected based on the difference between the actual temperature and the standard ambient temperature; the specific formula is: Among them, q final is the improved total radiation intensity, q (K) is the converged total radiation intensity, T0 is the standard ambient temperature; ΔT is the difference between the actual ambient temperature and the standard ambient temperature T0.

7. A method for predicting the damage range of gas pipeline leakage based on terrain and temperature correction, characterized in that: The final total radiation intensity received by each target point is predicted by using the gas pipeline leakage thermal radiation prediction method based on terrain and temperature correction as described in any one of claims 1 to 6; Based on the final total radiation intensity, predict the damage range and safety distance.

8. The method for predicting the damage range of gas pipeline leakage based on terrain and temperature correction according to claim 7 is characterized in that: Based on the final total radiation intensity, the damage range and safety distance are predicted; specifically: E final =q final ·A E final is the total radiation per unit time of the improved radiation source; A is the area of ​​the radiation source; q final is the final total radiation intensity; R final is the distance from the center of the radiation source to the target point, that is, the safety distance radius; τ j is the atmospheric transmittance, and I(r) is the thermal radiation value threshold.

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