CN116205013A - Natural gas diffusion amount and diffusion time calculation method and device - Google Patents
Natural gas diffusion amount and diffusion time calculation method and device Download PDFInfo
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Abstract
The invention provides a natural gas dispersion amount and a natural gas dispersion time calculation method and a natural gas dispersion time calculation device. The method comprises the following steps: establishing a natural gas emission amount calculation model based on an actual gas state equation under a standard state; calculating natural gas release quantity according to the model; dividing the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and respectively establishing a diffusing time calculation model in the critical state and the subcritical state based on an energy conservation law and a gas equation; and calculating the diffusing time under the critical state and the subcritical state respectively by utilizing the model, and summing to obtain the natural gas diffusing time. According to the invention, the natural gas emission calculation model is established by adopting the actual gas state equation, so that the method can be more in line with the actual environment, and the calculation result is more accurate; the invention divides the gas flow of the whole natural gas pipeline into a critical state and a subcritical state, simplifies the complex bleeding time calculation process, and simultaneously ensures that the accuracy of the calculation result can meet the engineering requirements.
Description
Technical Field
The invention belongs to the technical field of natural gas emission amount calculation, and particularly relates to a natural gas emission amount and emission time calculation method and device.
Background
The world's natural gas industry has rapidly evolved since the 21 st century, and the natural gas industry has become increasingly full of life, and natural gas pipelines have also been unprecedented. The pipeline transportation which is one of the large transportation methods of railways, highways, aviation, water transportation and pipelines 5 is an important component of the current natural gas transportation system, bears 98% of natural gas transportation tasks in China, and is characterized in that a natural gas transportation pipeline is connected with an upstream gas source and a downstream user like a life line, the happiness life of the national economy and people is related at any time, and the importance of the development of the natural gas industry and the flight of the national economy is self-evident.
In 1996, the overpressure sealing tank of the petrochemical complete petrochemical flare pipe network is blocked in 06 months, so that the discharged flare gas cannot be discharged in time, and the pressure in the tank exceeds the design pressure. Normal operation of the piping system is severely impaired. Tempering failure of 8-month Romen Hasi factory emptying system in 2000 causes explosion hot air to blow into a torch system, so that the temperature in the torch system rises to 300 ℃ instantaneously, negative pressure in the system is caused, and mixed gas burns vigorously. The water seal of the emptying system is destroyed, so that few people suffer from casualties. Venting system design and operation may result in different types of incidents that create serious safety concerns. Therefore, the relationship among the flow state, the pipeline pressure drop and the relief quantity of the safety relief device in the natural gas pipeline emptying process is studied in depth, and the method has important practical significance for judging whether the design of the emptying torch system is reasonable. Meanwhile, the field emptying data only has emptying time, and no specific emptying flow process and all flow parameter changes of the emptying process exist; in addition, the current site emptying is only to continuously adjust the opening of the valve, and no fixed emptying operation step exists. Therefore, a natural gas pipeline diffusing model is constructed, the natural gas diffusing rule is mastered, the operation accident rate of the natural gas pipeline can be reduced, the loss caused by natural gas leakage is reduced, and the safety operation capability of the natural gas pipeline is improved.
Because the natural gas emission amount is relatively complex, the existing natural gas emission amount calculation method generally adopts an estimation method in engineering, and the calculation is simple, but the accuracy of the result calculated by the common quality level estimation method is not high. When the error is large, the influence on the construction time and the follow-up progress of the engineering is large, and particularly when natural gas leakage occurs, the accuracy of the calculation result is important for weakening, blocking and eliminating risks. The existing natural gas diffusion time calculation model is generally based on a continuity equation, a momentum equation and an energy equation, a nonlinear partial differential equation set is established, and then solution is carried out through a drawing method, an analysis method, a numerical method and the like, so that the complexity of the whole calculation process is high, the accuracy is high, and the method is only suitable for theoretical simulation research and is difficult to meet actual engineering requirements.
Disclosure of Invention
In order to solve the problems in the prior art, the invention provides a natural gas dispersion amount and dispersion time calculation method and device.
In order to achieve the above object, the present invention adopts the following technical scheme.
In a first aspect, the present invention provides a method for calculating natural gas dispersion and dispersion time, comprising the steps of:
establishing a natural gas emission amount calculation model based on an actual gas state equation under a standard state;
calculating natural gas dispersion according to the natural gas dispersion calculation model;
dividing the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and respectively establishing a diffusing time calculation model in the critical state and the subcritical state based on an energy conservation law and a gas equation;
and calculating the diffusing time under the critical state and the subcritical state respectively by utilizing the model, and summing to obtain the natural gas diffusing time.
Further, the building of the natural gas emission calculation model based on the actual gas state equation under the standard state includes:
the actual gas state equation under the standard state is:
wherein p is 0 =0.101325 MPa, absolute pressure in standard state; t (T) 0 =293.15K, which is the temperature in the standard state; p is p ap Mean absolute pressure of gas in the pipeline; t (T) at The average temperature of the gas in the pipeline; z is Z 0 Is the compression factor in the standard state; z is Z 1 Is the compression factor in the actual environment; D. l is the diameter and length of the pipeline respectively;
the dispersion amount is obtained by the formula (1):
further, the calculating the natural gas emission amount according to the natural gas emission amount calculation model includes:
calculating the average absolute pressure of the gas in the pipeline:
wherein p is 1 、p 2 The gas pressures are respectively the starting point and the ending point of the pressure pipeline; p is p x Is the gas pressure at x from the start of the pipe;
calculating the average temperature of the gas in the pipeline:
wherein T is 1 、T 2 The gas temperatures at the start point and the end point of the pressure pipeline respectively;
calculating compression factors in the actual environment:
wherein Δ is the relative density of the gas;
substituting the formulas (4), (5) and (6) into the formula (3) to obtain the natural gas emission.
Further, the method for establishing the bleeding time calculation model comprises the following steps:
according to the law of conservation of mass:
Vdρ＝-v m dt (7)
wherein V is the volume of the pipeline; ρ is the natural gas density; v m Is mass flow; t is the bleeding time; r is the gas constant of natural gas;
according to the ambient pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Dividing the whole gas flow process in the pipeline into two states: p is p a /p ap When alpha is less than or equal to alpha, the critical state is p a /p ap >Alpha is subcritical state, and alpha is critical pressure ratio;
calculating the mass flow v in the critical state and the subcritical state respectively m1 、v m2 ：
Wherein mu is the opening degree of the diffusing pipeline; d is the inner diameter of the diffusing pipeline; k is the adiabatic index, p c Is the critical pressure;
substituting the formulas (9) and (10) into the formula (7) respectively, and integrating to obtain the diffusion time t of the critical state and the subcritical state 1 And t 2 ：
Wherein p is f To diffuse the absolute pressure of the gas before p b Is the absolute pressure of the diffused gas;
the total release time was calculated: t=t 1 +t 2 。
Still further, α=0.55.
In a second aspect, the present invention provides a natural gas dispersion amount and dispersion time calculation device, including:
the first modeling module is used for establishing a natural gas emission amount calculation model based on an actual gas state equation under a standard state;
the first calculation module is used for calculating natural gas emission according to the natural gas emission calculation model;
the second modeling module is used for dividing the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and respectively establishing a diffusing time calculation model in the critical state and the subcritical state based on an energy conservation law and a gas equation;
and the second calculation module is used for calculating and summing the diffusing time under the critical state and the subcritical state respectively by utilizing the model to obtain the natural gas diffusing time.
Further, the building of the natural gas emission calculation model based on the actual gas state equation under the standard state includes:
the actual gas state equation under the standard state is:
wherein p is 0 =0.101325 MPa, absolute pressure in standard state; t (T) 0 =293.15K, which is the temperature in the standard state; p is p ap Mean absolute pressure of gas in the pipeline; t (T) at The average temperature of the gas in the pipeline; z is Z 0 Is the compression factor in the standard state; z is Z 1 Is the compression factor in the actual environment; D. l is the diameter and length of the pipeline respectively;
the dispersion amount is obtained by the formula (1):
further, the calculating the natural gas emission amount according to the natural gas emission amount calculation model includes:
calculating the average absolute pressure of the gas in the pipeline:
wherein p is 1 、p 2 The gas pressures are respectively the starting point and the ending point of the pressure pipeline; p is p x Is the gas pressure at x from the start of the pipe;
calculating the average temperature of the gas in the pipeline:
wherein T is 1 、T 2 The gas temperatures at the start point and the end point of the pressure pipeline respectively;
calculating compression factors in the actual environment:
wherein Δ is the relative density of the gas;
substituting the formulas (4), (5) and (6) into the formula (3) to obtain the natural gas emission.
Further, the method for establishing the bleeding time calculation model comprises the following steps:
according to the law of conservation of mass:
Vdρ＝-v m dt (7)
wherein V is the volume of the pipeline; ρ is the natural gas density; v m Is mass flow; t is the bleeding time; r is the gas constant of natural gas;
according to the ambient pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Is of a size to complete the pipeThe gas flow process is divided into two states: p is p a /p ap When alpha is less than or equal to alpha, the critical state is p a /p ap >Alpha is subcritical state, and alpha is critical pressure ratio;
calculating the mass flow v in the critical state and the subcritical state respectively m1 、v m2 ：
Wherein mu is the opening degree of the diffusing pipeline; d is the inner diameter of the diffusing pipeline; k is the adiabatic index, p c Is the critical pressure;
substituting the formulas (9) and (10) into the formula (7) respectively, and integrating to obtain the diffusion time t of the critical state and the subcritical state 1 And t 2 ：
Wherein p is f To diffuse the absolute pressure of the gas before p b Is the absolute pressure of the diffused gas;
the total release time was calculated: t=t 1 +t 2 。
Still further, α=0.55.
Compared with the prior art, the invention has the following beneficial effects.
(1) Because the gas state equation ignores the size of gas molecules and the interaction force between molecules in the ideal state, the gas state equation does not accord with the actual engineering condition. According to the invention, the natural gas emission calculation model is established by adopting the actual gas state equation, so that the method can be more in line with the actual environment, and the calculation result is more accurate;
(2) Because the pressure in the pipeline continuously decreases along with the diffusing time in the natural gas diffusing process, and the law is complex, the gas property of the natural gas continuously changes along with the time, and the diffusing time is difficult to accurately calculate. The invention divides the gas flow of the whole natural gas pipeline into a critical state and a subcritical state, does not consider the friction force of the diffusing pipe, simplifies the complex diffusing time calculation process, and can meet the engineering requirement in terms of the accuracy of the calculation result.
Drawings
Fig. 1 is a flowchart of a natural gas dispersion amount and dispersion time calculation method according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of natural gas pipeline bleed amount and bleed time calculation.
Fig. 3 is a schematic diagram of natural gas pipeline average pressure calculation.
Fig. 4 is a block diagram of a natural gas dispersion and dispersion time calculation device according to an embodiment of the present invention.
Detailed Description
The present invention will be further described with reference to the drawings and the detailed description below, in order to make the objects, technical solutions and advantages of the present invention more apparent. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Fig. 1 is a flowchart of a natural gas dispersion amount and dispersion time calculation method according to an embodiment of the present invention, including the following steps:
102, calculating natural gas emission according to the natural gas emission calculation model;
and 104, calculating and summing the diffusion time under the critical state and the subcritical state respectively by utilizing the model to obtain the natural gas diffusion time.
In this embodiment, step 101 is mainly used for building a natural gas emission calculation model. According to the natural gas emission calculation method, the natural gas emission calculation model is built based on the actual gas state equation under the standard state, the natural gas emission can be obtained conveniently and accurately, and meanwhile the actual engineering requirements are met. The following examples will give a specific computational model.
In this embodiment, step 102 is mainly used to calculate the natural gas emission. The natural gas emission amount can be obtained by substituting the related constants, pipeline parameters and measured variable values contained in the model into the model by using the built emission amount calculation model. The relevant constants comprise air pressure, temperature, compression factor and the like in a standard state, the pipeline parameters comprise pipeline diameter, length and the like, and the measured variable values comprise air pressure, temperature and the like at the starting point and the end point of the pipeline.
In this embodiment, step 103 is mainly used for establishing a bleeding time calculation model. In order to simplify the calculation, the embodiment divides the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and establishes a diffusing time calculation model of the critical state and a diffusing time calculation model of the subcritical state based on an energy conservation law and a gas equation respectively. And summing the two models to obtain a total release time calculation model.
In this embodiment, step 104 is mainly used to calculate the natural gas diffusion time. In the embodiment, the built bleeding time calculation model is utilized, the related parameter variable values contained in the model are substituted into the model, the bleeding time in the critical state and the bleeding time in the subcritical state are calculated respectively, and the total bleeding time of the natural gas is obtained after summation.
As an alternative embodiment, the building a natural gas emission amount calculation model based on the actual gas state equation under the standard state includes:
the actual gas state equation under the standard state is:
wherein p is 0 =0.101325 MPa, absolute pressure in standard state; t (T) 0 =293.15K, which is the temperature in the standard state; p is p ap Mean absolute pressure of gas in the pipeline; t (T) at The average temperature of the gas in the pipeline; z is Z 0 Is the compression factor in the standard state; z is Z 1 Is the compression factor in the actual environment; D. l is the diameter and length of the pipeline respectively;
the dispersion amount is obtained by the formula (1):
the embodiment provides a technical scheme for establishing a natural gas emission calculation model. The actual gas state equation under the standard state is listed first, as in equation (1). (1) The left side corresponds to the gas state to be diffused, the embodiment is set to be in a standard state, (1) the right side corresponds to the gas state in the pipeline, and the average absolute pressure p is required because the gas state in the pipeline is diffused in actual conditions and the pressure difference and the temperature difference between the starting point and the end point are large ap And an average temperature T at As shown in fig. 2. Then, the dispersion V is obtained from the formula (1) 1 The expression of (3) is obtained.
As an alternative embodiment, the calculating the natural gas emission according to the natural gas emission calculation model includes:
calculating the average absolute pressure of the gas in the pipeline:
wherein p is 1 、p 2 The gas pressures are respectively the starting point and the ending point of the pressure pipeline; p is p x Is the gas pressure at x from the start of the pipe;
calculating the average temperature of the gas in the pipeline:
wherein T is 1 、T 2 The gas temperatures at the start point and the end point of the pressure pipeline respectively;
calculating compression factors in the actual environment:
wherein Δ is the relative density of the gas;
substituting the formulas (4), (5) and (6) into the formula (3) to obtain the natural gas emission.
The embodiment provides a technical scheme for calculating the natural gas emission according to the natural gas emission calculation model. A dispersion amount calculation model is shown as formula (3), wherein p ap 、T at 、Z 1 For unknown quantity, the unknown quantity is substituted into the formula (3) after being solved one by one.
When the gas pipeline stops conveying, a pressure balance phenomenon can occur, and the pressure in the gas pipeline does not disappear immediately like the pressure in the gas pipeline, but is still in a pressure state, and the gas at the high pressure end gradually flows to the low pressure end. Thus, the starting point pressure p 1 Gradually descend; the low pressure end is provided with high pressure gas inflow, and the end pressure p 2 Gradually rising, and finally, the pressure at the two ends reaches a certain average value, namely the average pressure, and the average pressure calculation model of the natural gas pipeline is shown in fig. 3. Average pressure p of pipeline ap Can pass throughThe pressure drop function is integrated according to the total length of the pipeline, as shown in the formula (4). Further, the average air temperature T is obtained at Formula (5).
Compression factor Z in practical environment 1 The embodiment adopts a formula of the American California Natural Gas Association (CNGA), is suitable for natural gas with the relative density of 0.55-0.70, the gas pressure of 0-6.89MPa and the gas temperature of 272.2-333.3K, and accords with the actual condition of a gas pipeline in China. Specifically as shown in formula (6).
As an alternative embodiment, the method for establishing the bleeding time calculation model includes:
according to the law of conservation of mass:
Vdρ＝-v m dt (7)
wherein V is the volume of the pipeline; ρ is the natural gas density; v m Is mass flow; t is the bleeding time; r is the gas constant of natural gas;
according to the ambient pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Dividing the whole gas flow process in the pipeline into two states: p is p a /p ap When alpha is less than or equal to alpha, the critical state is p a /p ap >Alpha is subcritical state, and alpha is critical pressure ratio;
calculating the mass flow v in the critical state and the subcritical state respectively m1 、v m2 ：
Wherein mu is the opening degree of the diffusing pipeline; d is the inner diameter of the diffusing pipeline; k is the adiabatic index, p c Is the critical pressure;
substituting the formulas (9) and (10) into the formula (7) respectively, and integrating to obtain the diffusion time t of the critical state and the subcritical state 1 And t 2 ：
Wherein p is f To diffuse the absolute pressure of the gas before p b Is the absolute pressure of the diffused gas;
the total release time was calculated: t=t 1 +t 2 。
The embodiment provides a technical scheme for establishing a bleeding time calculation model. Firstly, listing differential equations shown in the formula (7) according to the law of conservation of mass; then according to the ambient air pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Whether the critical pressure ratio alpha is exceeded or not, dividing the whole gas flow process in the pipeline into a critical state and a subcritical state, and respectively calculating the mass flow v under the critical state and the subcritical state m1 、v m2 Formula (9), (10); further calculating the release time t in critical state and subcritical state 1 、t 2 As shown in formulas (12) and (13). (13) The integral calculation of the formula is complex, and the calculation and the solution can be carried out in a python programming mode, so that the subcritical state natural gas diffusion time t is obtained 2 The method comprises the steps of carrying out a first treatment on the surface of the Final summation t=t 1 +t 2 And obtaining a total bleeding time calculation model.
As an alternative embodiment, α=0.55.
This embodiment gives a specific value of the critical pressure ratio α. The critical pressure ratio is a function of the adiabatic index K, as in equation (11). The adiabatic index K is a function of temperature, and K can be approximated as a constant value at normal temperature, and generally K is 1.3 for a gas such as natural gas composed of polyatomic molecules. Substituting k=1.3 into the formula (11) yields α=0.55.
The following gives 2 examples of the calculation of the amount of dispersion and the time of dispersion using the embodiment of the present invention.
Example 1
The pipeline and the gas parameters are as follows:
the length of the pipeline is L=30 km, the inner diameter of the pipeline is D=0.411 m, the inner diameter of the diffusing pipe is d=0.098 m, the opening degree of the diffusing pipe is mu=1, the average pressure of the initial diffusing pipe is 4MPa, the average pressure of the end diffusing pipe is 0MPa, and the average gas temperature is 200C.
The calculation result is as follows:
actual dispersion amount: 169563m 3 Calculating the dispersion amount: 172000m 3 ；
Actual release time 137 minutes: calculating the bleeding time: 140 minutes.
Example 2
The pipeline and the gas parameters are as follows:
the length of the pipeline is L=10 km, the inner diameter of the pipeline is D=0.4 m, the inner diameter of the diffusing pipe is d=0.1 m, the opening degree of the diffusing pipe is mu=0.8, the average pressure of the initial pipe of the diffusing pipe is 2.5MPa, the average pressure of the end pipe of the diffusing pipe is 0MPa, and the average gas temperature is 200C.
The calculation result is as follows:
actual dispersion amount: 32421m 3 Calculating the dispersion amount: 32769m 3 ；
The actual release time is 48 minutes: calculating the bleeding time: 49 minutes.
The results of 2 calculation examples show that the calculation results are very close to the actual data.
Fig. 4 is a schematic diagram of a natural gas emission and emission time calculation device according to an embodiment of the present invention, where the device includes:
the first modeling module 11 is used for establishing a natural gas emission amount calculation model based on an actual gas state equation under a standard state;
a first calculation module 12 for calculating a natural gas emission amount according to the natural gas emission amount calculation model;
the second modeling module 13 is configured to divide the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and respectively establish a diffusing time calculation model in the critical state and the subcritical state based on the law of conservation of energy and a gas equation;
the second calculation module 14 calculates and sums the natural gas blow-off times in the critical state and the subcritical state, respectively, by using the model.
The device of this embodiment may be used to implement the technical solution of the method embodiment shown in fig. 1, and its implementation principle and technical effects are similar, and are not described here again. As well as the latter embodiments, will not be explained again.
As an alternative embodiment, the building a natural gas emission amount calculation model based on the actual gas state equation under the standard state includes:
the actual gas state equation under the standard state is:
wherein p is 0 =0.101325 MPa, absolute pressure in standard state; t (T) 0 =293.15K, which is the temperature in the standard state; p is p ap Mean absolute pressure of gas in the pipeline; t (T) at The average temperature of the gas in the pipeline; z is Z 0 Is the compression factor in the standard state; z is Z 1 Is the compression factor in the actual environment; D. l is the diameter and length of the pipeline respectively;
the dispersion amount is obtained by the formula (1):
as an alternative embodiment, the calculating the natural gas emission according to the natural gas emission calculation model includes:
calculating the average absolute pressure of the gas in the pipeline:
wherein p is 1 、p 2 The gas pressures are respectively the starting point and the ending point of the pressure pipeline; p is p x Is the gas pressure at x from the start of the pipe;
calculating the average temperature of the gas in the pipeline:
wherein T is 1 、T 2 The gas temperatures at the start point and the end point of the pressure pipeline respectively;
calculating compression factors in the actual environment:
wherein Δ is the relative density of the gas;
substituting the formulas (4), (5) and (6) into the formula (3) to obtain the natural gas emission.
As an alternative embodiment, the method for establishing the bleeding time calculation model includes:
according to the law of conservation of mass:
Vdρ＝-v m dt (7)
wherein V is the volume of the pipeline; ρ is the natural gas density; v m Is mass flow; t is the bleeding time; r is the gas constant of natural gas;
depending on the circumstancesAir pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Dividing the whole gas flow process in the pipeline into two states: p is p a /p ap When alpha is less than or equal to alpha, the critical state is p a /p ap >Alpha is subcritical state, and alpha is critical pressure ratio;
calculating the mass flow v in the critical state and the subcritical state respectively m1 、v m2 ：
Wherein mu is the opening degree of the diffusing pipeline; d is the inner diameter of the diffusing pipeline; k is the adiabatic index, p c Is the critical pressure;
substituting the formulas (9) and (10) into the formula (7) respectively, and integrating to obtain the diffusion time t of the critical state and the subcritical state 1 And t 2 ：
Wherein p is f To diffuse the absolute pressure of the gas before p b Is the absolute pressure of the diffused gas;
the total release time was calculated: t=t 1 +t 2 。
As an alternative embodiment, α=0.55.
The foregoing is merely illustrative of the present invention, and the present invention is not limited thereto, and any changes or substitutions easily contemplated by those skilled in the art within the scope of the present invention should be included in the present invention. Therefore, the protection scope of the invention is subject to the protection scope of the claims.
Claims (10)
1. The natural gas dispersion amount and dispersion time calculation method is characterized by comprising the following steps of:
establishing a natural gas emission amount calculation model based on an actual gas state equation under a standard state;
calculating natural gas dispersion according to the natural gas dispersion calculation model;
dividing the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and respectively establishing a diffusing time calculation model in the critical state and the subcritical state based on an energy conservation law and a gas equation;
and calculating the diffusing time under the critical state and the subcritical state respectively by utilizing the model, and summing to obtain the natural gas diffusing time.
2. The method for calculating the natural gas diffusion amount and the diffusion time according to claim 1, wherein the building of the natural gas diffusion amount calculation model based on the actual gas state equation under the standard state comprises:
the actual gas state equation under the standard state is:
wherein p is 0 =0.101325 MPa, absolute pressure in standard state; t (T) 0 =293.15K, which is the temperature in the standard state; p is p ap Mean absolute pressure of gas in the pipeline; t (T) at The average temperature of the gas in the pipeline; z is Z 0 Is the compression factor in the standard state; z is Z 1 Is the compression factor in the actual environment; D. l is the diameter and length of the pipeline respectively;
the dispersion amount is obtained by the formula (1):
3. the natural gas dispersion and dispersion time calculation method according to claim 2, wherein the calculating the natural gas dispersion according to the natural gas dispersion calculation model includes:
calculating the average absolute pressure of the gas in the pipeline:
wherein p is 1 、p 2 The gas pressures are respectively the starting point and the ending point of the pressure pipeline; p is p x Is the gas pressure at x from the start of the pipe;
calculating the average temperature of the gas in the pipeline:
wherein T is 1 、T 2 The gas temperatures at the start point and the end point of the pressure pipeline respectively;
calculating compression factors in the actual environment:
wherein Δ is the relative density of the gas;
substituting the formulas (4), (5) and (6) into the formula (3) to obtain the natural gas emission.
4. A natural gas diffusion amount and diffusion time calculation method according to claim 3, wherein the method for establishing the diffusion time calculation model comprises:
according to the law of conservation of mass:
Vdρ＝-v m dt (7)
wherein V is the volume of the pipeline; ρ is the natural gas density; v m Is mass flow; t is the bleeding time; r is the gas constant of natural gas;
according to the ambient pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Dividing the whole gas flow process in the pipeline into two states: p is p a /p ap When alpha is less than or equal to alpha, the critical state is p a /p ap >Alpha is subcritical state, and alpha is critical pressure ratio;
calculating the mass flow v in the critical state and the subcritical state respectively m1 、v m2 ：
Wherein mu is the opening degree of the diffusing pipeline; d is the inner diameter of the diffusing pipeline; k is the adiabatic index, p c Is the critical pressure;
substituting the formulas (9) and (10) into the formula (7) respectively, and integrating to obtain the diffusion time t of the critical state and the subcritical state 1 And t 2 ：
Wherein p is f To diffuse the absolute pressure of the gas before p b Is the absolute pressure of the diffused gas;
the total release time was calculated: t=t 1 +t 2 。
5. The method for calculating the natural gas diffusion amount and diffusion time according to claim 4, wherein α=0.55.
6. A natural gas dispersion and time calculation device, comprising:
the first modeling module is used for establishing a natural gas emission amount calculation model based on an actual gas state equation under a standard state;
the first calculation module is used for calculating natural gas emission according to the natural gas emission calculation model;
the second modeling module is used for dividing the gas flow in the natural gas pipeline diffusing process into a critical state and a subcritical state, and respectively establishing a diffusing time calculation model in the critical state and the subcritical state based on an energy conservation law and a gas equation;
and the second calculation module is used for calculating and summing the diffusing time under the critical state and the subcritical state respectively by utilizing the model to obtain the natural gas diffusing time.
7. The natural gas bleeding amount and bleeding time calculation apparatus according to claim 6, wherein the building of the natural gas bleeding amount calculation model based on the actual gas state equation in the standard state includes:
the actual gas state equation under the standard state is:
wherein p is 0 =0.101325 MPa, absolute pressure in standard state; t (T) 0 =293.15K, which is the temperature in the standard state; p is p ap Mean absolute pressure of gas in the pipeline; t (T) at The average temperature of the gas in the pipeline; z is Z 0 Is the compression factor in the standard state; z is Z 1 Is the compression factor in the actual environment; D. l is the diameter and length of the pipeline respectively;
the dispersion amount is obtained by the formula (1):
8. the natural gas dispersion and time calculation device according to claim 7, wherein the calculating the natural gas dispersion from the natural gas dispersion calculation model includes:
calculating the average absolute pressure of the gas in the pipeline:
wherein p is 1 、p 2 The gas pressures are respectively the starting point and the ending point of the pressure pipeline; p is p x For gas pressure at x from the start of the pipeForce;
calculating the average temperature of the gas in the pipeline:
wherein T is 1 、T 2 The gas temperatures at the start point and the end point of the pressure pipeline respectively;
calculating compression factors in the actual environment:
wherein Δ is the relative density of the gas;
substituting the formulas (4), (5) and (6) into the formula (3) to obtain the natural gas emission.
9. The natural gas diffusion amount and diffusion time calculation device according to claim 8, wherein the method for establishing the diffusion time calculation model comprises the steps of:
according to the law of conservation of mass:
Vdρ＝-v m dt (7)
wherein V is the volume of the pipeline; ρ is the natural gas density; v m Is mass flow; t is the bleeding time; r is the gas constant of natural gas;
according to the ambient pressure p a Average pressure p with gas in pipeline ap Ratio p of (2) a /p ap Dividing the whole gas flow process in the pipeline into two states: p is p a /p ap When alpha is less than or equal to alpha, the critical state is p a /p ap >Alpha is subcritical state, and alpha is critical pressure ratio;
calculating the mass flow v in the critical state and the subcritical state respectively m1 、v m2 ：
Wherein mu is the opening degree of the diffusing pipeline; d is the inner diameter of the diffusing pipeline; k is the adiabatic index, p c Is the critical pressure;
substituting the formulas (9) and (10) into the formula (7) respectively, and integrating to obtain the diffusion time t of the critical state and the subcritical state 1 And t 2 ：
Wherein p is f To diffuse the absolute pressure of the gas before p b Is the absolute pressure of the diffused gas;
the total release time was calculated: t=t 1 +t 2 。
10. The natural gas diffusion amount and diffusion time calculating apparatus according to claim 9, wherein α=0.55.
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