Numerical simulation method and device for hydrogen-doped natural gas pipeline conveying process

Abstract

The invention discloses a numerical simulation method and device for a hydrogen-doped natural gas pipeline conveying process. The method comprises the following steps: determining a first equation expression corresponding to a pipeline element in a hydrogen-doped natural gas pipeline network, determining a second equation expression corresponding to a non-pipeline element, and determining a third equation expression corresponding to a gas source and a fourth equation expression corresponding to an element connection point; aiming at a to-be-simulated moment, solving all the equation expressions to obtain hydraulic parameters and thermal parameters in the hydrogen-doped natural gas pipeline network at the to-be-simulated moment; during solving, a hydraulic equation set composed of the hydraulic equation expressions in all the equation expressions is solved, and then a thermal equation set composed of the thermal equation expressions in all the equation expressions is solved. According to the embodiment of the invention, all equations determined by the hydrogen-doped natural gas pipeline network can be decoupled, so that the numerical solution difficulty of a simulation process is reduced, and the calculation rate is improved.

Description

Technical Field

[0001] This article relates to pipeline transportation simulation technology, and in particular to a numerical simulation method and device for hydrogen-blended natural gas pipeline transportation process. Background Art

[0002] With the rapid development of the hydrogen energy industry, the safe and efficient transportation of hydrogen has become a key link in the hydrogen energy industry chain. In this link, numerical simulation can provide important technical support for the design and operation management of hydrogen-blended natural gas pipeline transportation process.

[0003] In the related art, the corresponding equation expressions are often determined for the components in the hydrogen-blended natural gas pipeline network, and then all the determined equations are solved together to obtain the pipeline transportation process parameters.

[0004] However, this method is difficult to solve and has low computational efficiency due to the coupling between the expressions of each equation. Summary of the invention

[0005] The present application provides a method and device for numerical simulation of a hydrogen-blended natural gas pipeline transportation process, which can decouple all equations determined by a hydrogen-blended natural gas pipeline network, thereby reducing the difficulty of solving the numerical values ​​of the simulated process and improving the calculation rate.

[0006] On the one hand, the present application provides a method for numerical simulation of hydrogen-blended natural gas pipeline transportation process, comprising:

[0007] Determine a first equation expression corresponding to a pipeline element in a hydrogen-blended natural gas pipeline network, determine a second equation expression corresponding to a non-pipeline element, and determine a third equation expression corresponding to a gas source and a fourth equation expression corresponding to an element connection point;

[0008] For the time to be simulated, the first equation expression, the second equation expression, the third equation expression and the fourth equation expression are solved to obtain the hydraulic parameters and thermal parameters in the hydrogen-blended natural gas pipeline network at the time to be simulated; when solving, the hydraulic equation group composed of the hydraulic equation expressions in all the equation expressions is first solved, and then the thermal equation group composed of the thermal equation expressions in all the equation expressions is solved.

[0009] On the other hand, the present application provides a numerical simulation device for hydrogen-blended natural gas pipeline transportation process, comprising: a memory and a processor, wherein the memory is used to store an executable program;

[0010] The processor is used to read and execute the executable program to implement the above-mentioned numerical simulation method for hydrogen-blended natural gas pipeline transportation process.

[0011] Compared with the related art, the present application includes determining the first equation expression corresponding to the pipeline element in the hydrogen-blended natural gas pipeline network, the second equation expression corresponding to the non-pipeline element, the third equation expression corresponding to the gas source, and the fourth equation expression corresponding to the element connection point; for the time to be simulated, all equation expressions are solved to obtain the hydraulic parameters and thermal parameters in the hydrogen-blended natural gas pipeline network at the time to be simulated; when solving, the hydraulic equation group composed of the hydraulic equation expressions in all equation expressions is first solved, and then the thermal equation group composed of the thermal equation expressions in all equation expressions is solved. Therefore, all the determined equations are decoupled to form different equation groups, and then the different equation groups are solved separately in sequence, thereby reducing the difficulty of solving the process values ​​of the simulation and improving the calculation rate.

[0012] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0014] Figure 1 A schematic diagram of a flow chart of a numerical simulation method for a hydrogen-blended natural gas pipeline transportation process provided in an embodiment of the present application;

[0015] Figure 2 A schematic diagram of gas transmission volume calculation results of a numerical simulation of a hydrogen-blended natural gas pipeline transportation process provided in an embodiment of the present application;

[0016] Figure 3 A schematic diagram of the calculation results of the outlet pressure of a numerical simulation of a hydrogen-blended natural gas pipeline transportation process provided in an embodiment of the present application;

[0017] Figure 4 A schematic diagram of pressure calculation results along the pipeline for numerical simulation of a hydrogen-blended natural gas pipeline transportation process provided in an embodiment of the present application;

[0018] Figure 5 A schematic diagram of temperature calculation results along the pipeline for numerical simulation of a hydrogen-blended natural gas pipeline transportation process provided in an embodiment of the present application;

[0019] Figure 6 A schematic diagram comparing the computational efficiency of different numerical simulation methods for hydrogen-blended natural gas pipeline transportation processes provided in the embodiments of the present application. DETAILED DESCRIPTION

[0020] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0021] The present application includes and contemplates combinations of features and elements known to those of ordinary skill in the art. The embodiments, features and elements disclosed in the present application may also be combined with any conventional features or elements to form a unique invention scheme defined by the claims. Any features or elements of any embodiment may also be combined with features or elements from other invention schemes to form another unique invention scheme defined by the claims. Therefore, it should be understood that any feature shown and / or discussed in the present application may be implemented individually or in any appropriate combination. Therefore, except for the limitations made according to the attached claims and their equivalents, the embodiments are not subject to other restrictions. In addition, various modifications and changes may be made within the scope of protection of the attached claims.

[0022] In addition, when describing representative embodiments, the specification may have presented the method and / or process as a specific sequence of steps. However, to the extent that the method or process does not rely on the specific order of the steps described herein, the method or process should not be limited to the steps of the specific order described. As will be understood by those of ordinary skill in the art, other sequences of steps are also possible. Therefore, the specific sequence of the steps set forth in the specification should not be interpreted as a limitation to the claims. In addition, the claims for the method and / or process should not be limited to the steps of performing them in the order written, and those skilled in the art can easily understand that these sequences can be changed and still remain within the spirit and scope of the embodiments of the present application.

[0023] The present application embodiment provides a method for numerical simulation of hydrogen-blended natural gas pipeline transportation process, such as Figure 1 As shown, including:

[0024] Step 101, determining a first equation expression corresponding to a pipeline component in a hydrogen-blended natural gas pipeline network, determining a second equation expression corresponding to a non-pipeline component, and determining a third equation expression corresponding to a gas source and a fourth equation expression corresponding to a component connection point;

[0025] Step 102: for the time to be simulated, the first equation expression, the second equation expression, the third equation expression and the fourth equation expression are solved to obtain hydraulic parameters and thermal parameters in the hydrogen-blended natural gas pipeline network at the time to be simulated; when solving, first solve the hydraulic equation group composed of the hydraulic equation expressions in all equation expressions, and then solve the thermal equation group composed of the thermal equation expressions in all equation expressions.

[0026] Exemplarily, for different simulation moments, the first equation expression, the second equation expression, the third equation expression and the fourth equation expression are repeatedly solved to obtain the results of the pressure, mass flow rate and temperature of the starting and end points of each element such as pipeline elements, non-pipeline elements such as valves and compressors, and gas sources changing with the simulation time. The changing rules of pressure, mass flow rate and temperature along the pipeline at different simulation moments can also be obtained.

[0027] Exemplarily, hydraulic parameters include: flow rate, mass flow, pressure, and thermal parameters include: temperature.

[0028] The numerical simulation method of the hydrogen-blended natural gas pipeline transportation process provided in the embodiment of the present application determines the first equation expression corresponding to the pipeline element in the hydrogen-blended natural gas pipeline network, the second equation expression corresponding to the non-pipeline element, the third equation expression corresponding to the gas source, and the fourth equation expression corresponding to the element connection point; for the time to be simulated, all equation expressions are solved to obtain the hydraulic parameters and thermal parameters in the hydrogen-blended natural gas pipeline network at the time to be simulated; when solving, the hydraulic equation group composed of the hydraulic equation expressions in all equation expressions is first solved, and then the thermal equation group composed of the thermal equation expressions in all equation expressions is solved. Therefore, all the determined equations are decoupled to form different equation groups, and then the different equation groups are solved separately in sequence, thereby reducing the difficulty of numerical solution of the simulation process and improving the calculation rate.

[0029] In an exemplary embodiment, the non-pipeline element includes: a compressor; when the non-pipeline element is the compressor, the equation expression corresponding to the non-pipeline element includes: an equation expression of the inlet pressure, the outlet pressure, and the flow rate obtained by converting the compressor performance curve under different hydrogen blending ratios using a first-class similarity conversion method.

[0030] Exemplarily, the first type similar conversion method refers to a first type similar conversion method commonly used by compressors.

[0031] The related art does not consider the influence of hydrogen addition on the performance curve of the compressor in the pipeline network, but the numerical simulation method of the hydrogen-added natural gas pipeline transportation process provided in the application embodiment considers the influence of hydrogen addition on the performance curve of the compressor in the pipeline network.

[0032] In an exemplary embodiment, the determining of the first equation expression corresponding to the pipeline element in the hydrogen-blended natural gas pipeline network includes:

[0033] First, determining the initial equation expression corresponding to the pipeline element;

[0034] Secondly, the Taylor expansion formula is used to linearize the initial equation expression corresponding to the pipeline element to obtain the intermediate equation expression;

[0035] Finally, the intermediate equation expression corresponding to the pipeline element is discretized using the finite difference method to obtain the first equation expression.

[0036] In an exemplary embodiment, the determining of the second equation expression corresponding to the non-pipeline element includes:

[0037] First, determining an initial equation expression corresponding to the non-pipeline element;

[0038] Secondly, the initial equation expression corresponding to the non-pipeline element is linearized using the Taylor expansion formula to obtain the second equation expression.

[0039] Exemplarily, the determined initial equation expressions corresponding to the pipeline elements in the hydrogen-blended natural gas pipeline network include:

[0040]

[0041]

[0042]

[0043] Among them, formula (1) is the continuity equation derived from the law of conservation of mass, formula (2) is the momentum equation derived from the law of conservation of momentum, and formula (3) is the energy equation derived from the law of conservation of energy. In the formula, t is the time, in seconds; x is the length of the pipeline, in meters; λ is the hydraulic friction coefficient, and A is the area of ​​the pipeline cross section, in meters. 2 ; ρ is the density of hydrogen-blended natural gas, in kg / m 3 ; w is the flow rate of hydrogen-blended natural gas, in m / s; d is the inner diameter of the pipeline, in m; θ is the inclination angle of the pipeline, in rad; g is the acceleration of gravity, in m / s 2 ; m is the mass flow rate of hydrogen-blended natural gas, in kg / s; p is the pressure, in Pa; c v is the specific heat capacity of hydrogen-blended natural gas at constant volume, in J / (kg·K); T is the temperature of hydrogen-blended natural gas, in K; K is the total heat transfer coefficient, in W / (m 2 ·K); T gis the temperature of the medium around the pipe, in K; D is the outer diameter of the pipe, in m.

[0044] In practical applications, pressure p, mass flow rate m, and temperature T in equations (1), (2), and (3) are variables to be solved, and the remaining variables are known values ​​at the current solution time (using the values ​​of the previous time).

[0045] Exemplarily, the determined initial equation expressions corresponding to the non-pipeline elements in the hydrogen-blended natural gas pipeline network include:

[0046] f p (p in ,m in ,p out ,m out )=0 (4)

[0047] f m (m in ,m out )=0 (5)

[0048] f T (T in ,T out )=0 (6)

[0049] Among them, formula (4) is the pressure equation, formula (5) is the mass flow equation, and formula (6) is the temperature equation. p, m, and T represent pressure, mass flow, and temperature respectively; subscripts in and out represent the inlet and outlet of non-pipeline components respectively.

[0050] Equations (4), (5), and (6) represent a functional relationship. In practical applications, when a specific non-pipeline component is given, such as a certain type of compressor or valve, equations (4), (5), and (6) will have a specific expression. There are hundreds of compressors and valves in practice, so the expression is determined by the specific situation.

[0051] Exemplarily, the third equation expression corresponding to the determined gas source includes:

[0052] p=p(t) (7)

[0053] m=m(t) (8)

[0054] T=T(t) (9)

[0055] Among them, formula (7) is the pressure equation, formula (8) is the mass flow equation, and formula (9) is the temperature equation. p, m, and T represent pressure, mass flow, and temperature respectively; subscripts in and out represent the inlet and outlet of the gas source respectively. The source of hydrogen-blended natural gas is divided into gas supply source and distribution station.

[0056] In practical applications, equations (7), (8), and (9) are boundary conditions that need to be given during calculation and will be given at the beginning of the calculation.

[0057] Exemplarily, the fourth equation expression corresponding to the determined element connection point includes:

[0058]

[0059]

[0060]

[0061] Among them, formula (10) is the pressure equation, formula (11) is the mass flow equation, and formula (12) is the temperature equation. p It represents the specific heat capacity at constant pressure of hydrogen-blended natural gas, with the unit of J / (kg·N), where N is the number of components and the subscripts in and out represent the inlet and outlet of the component connection point, respectively.

[0062] In order to mathematically process the initial equation expressions (1) to (3) corresponding to the determined hydrogen-blended natural gas pipeline components, Taylor expansion is used to linearize them. The linearized results can be uniformly written as the following expression:

[0063]

[0064] in, is the variable to be determined in the previous time layer, and the element of G matrix is ​​g i,j , The elements of the matrix are b i,j is an element in matrix B, f i is the i-th component of vector F, u i is the i-th component in vector U. For equations (1) and (2), the variables in equation (13) are,

[0065]

[0066]

[0067]

[0068] For equation (3), the variables in equation (13) are:

[0069] U=T (14-4)

[0070] G=0 (14-5)

[0071]

[0072] In order to mathematically process the initial equation expressions (4) to (6) corresponding to the determined non-pipeline components of hydrogen-blended natural gas, Taylor expansion is used to linearize them. The linearized results can be uniformly expressed as the following expression:

[0073]

[0074] Among them, F npc In equation (15), npc represents a column vector and the subscript npc represents a non-pipeline element. For equations (4) and (5), the variables in equation (15) are:

[0075]

[0076]

[0077]

[0078] For equation (6), the variables in equation (15) are,

[0079] X=T (16-4)

[0080] F npc =f T (16-5)

[0081]

[0082] For example, the pressure equation (4) and flow equation (5) of the compressor should be equation expressions after considering the influence of hydrogen addition on the working performance of the compressor. Since the influence of hydrogen addition on the adiabatic index of natural gas is small, the influence of hydrogen addition on the adiabatic index of natural gas can be approximately ignored when the hydrogen addition ratio is small. Therefore, the first-class similarity conversion method is used to convert the compressor performance curve under different hydrogen addition ratio conditions, thereby obtaining equations (4) and (5).

[0083] In an exemplary embodiment, the discretization of the intermediate equation expression corresponding to the pipeline element using the finite difference method includes:

[0084] Firstly, the non-steady-state terms of the continuity equation and the momentum equation in the intermediate equation expression are discretized by using the forward difference format, and the convection terms of the continuity equation and the momentum equation in the intermediate equation expression are discretized by using the central difference format;

[0085] Secondly, the non-steady-state term of the energy equation in the intermediate equation expression is discretized by using a forward difference format, and the convection term of the energy equation in the intermediate equation expression is discretized by using a first-order upwind format.

[0086] Exemplarily, the finite difference method is used to discretize equations (13) and (14) corresponding to the linearized hydrogen-blended natural gas pipeline components.

[0087] First, the continuity equation and momentum equation are discretized. The unsteady-state term is discretized using the forward difference format, and the convection term is discretized using the central difference format. The discretization results of equations (13), (14-1) to (14-3) are as follows:

[0088]

[0089] in,

[0090] I is the 2×2 identity matrix.

[0091] The energy equation is discretized again, where the non-steady-state term is discretized using the forward difference format and the convection term is discretized using the first-order upwind format. The discretization results of equations (13), (14-4) to (14-5) are as follows:

[0092]

[0093] in,

[0094] In an exemplary embodiment, solving the hydraulic equation group consisting of hydraulic equation expressions in all equation expressions includes:

[0095] First, the free variables are set as the starting pressure and the end mass flow of the pipeline, and the equation expressions of the pipeline elements in the hydraulic equations are pre-solved according to the thermodynamic parameters calculated last time and the pre-calculated physical properties of the hydrogen-blended natural gas, and the set free variables, so as to obtain the relationship between the hydraulic parameters of each node in the pipeline element and the free variables; wherein, when the hydraulic equations are solved for the first time, the thermodynamic parameters calculated last time are the pre-assumed thermodynamic parameters;

[0096] Secondly, the hydraulic parameters in the hydraulic equation group are solved using the relationship between the hydraulic parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the hydraulic equation group.

[0097] In an exemplary embodiment, the nodes include: boundary nodes and internal nodes, and the method of solving the hydraulic parameters in the hydraulic equation group by using the obtained relationship between the hydraulic parameters and free variables of each node in the pipeline element and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the hydraulic equation group includes:

[0098] Firstly, according to the obtained relationship between the hydraulic parameters of each node in the pipeline element and the free variables, the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the hydraulic equation group are combined to solve the hydraulic parameters of the boundary nodes in all pipeline elements and non-pipeline elements;

[0099] Secondly, the hydraulic parameters of the boundary nodes of all pipeline elements and non-pipeline elements are substituted as free variables into the relationship between the hydraulic parameters of the internal nodes in the pipeline elements and the free variables to obtain the hydraulic parameters of the internal nodes in the pipeline elements.

[0100] In an exemplary embodiment, solving the thermodynamic equation group consisting of thermodynamic equation expressions in all equation expressions includes:

[0101] First, the free variable is set as the temperature of the upstream boundary node, and the equation expression of the pipeline element in the thermal equation group is pre-solved according to the obtained hydraulic parameters and the set free variables to obtain the relationship between the thermal parameters of each node in the pipeline element and the free variables;

[0102] Secondly, the thermal parameters in the thermal equation group are solved using the relationship between the thermal parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the thermal equation group.

[0103] In an exemplary embodiment, solving the thermal parameters in the thermal equation group by using the obtained relationship between the thermal parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the thermal equation group includes:

[0104] Firstly, according to the obtained relationship between the thermodynamic parameters of each node in the pipeline element and the free variables, the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the thermodynamic equation group are combined to solve the thermodynamic parameters of the boundary nodes in all pipeline elements and non-pipeline elements;

[0105] Secondly, the obtained thermal parameters of the boundary nodes of all pipeline elements and non-pipeline elements are substituted as free variables into the relationship between the thermal parameters of the internal nodes in the pipeline elements and the free variables to obtain the thermal parameters of the internal nodes in the pipeline elements.

[0106] Exemplarily, the discrete algebraic equations that need to be solved for the numerical simulation of the hydrogen-blended natural gas pipeline transportation process are obtained, including the discrete equations (17) and (18) of pipeline components, the discrete equations (15) and (16) of non-pipeline components, the gas source equations (7) to (9), and the element connection point equations (10) to (12). Among them, the discrete equations (17), (15), (16-1) to (16-3), (7), (8), (10), and (11) are also called the hydraulic equations for the numerical simulation of the hydrogen-blended natural gas pipeline transportation process, and are recorded as the A equation group; the discrete equations (18), (15), (16-4) to (16-6), (9), and (12) are also called the thermal equations for the numerical simulation of the hydrogen-blended natural gas pipeline transportation process, and are recorded as the B equation group.

[0107] In order to improve the efficiency of numerical simulation of hydrogen-blended natural gas pipeline transportation process, the simulation process is decomposed into two parts: hydraulic simulation and thermal simulation. Then, the decoupling method of separate sequential solution is used for calculation, that is, the hydraulic equation group A of the hydrogen-blended natural gas pipeline network is solved first to obtain hydraulic parameters such as pressure and mass flow rate, and then the thermal equation group B of the hydrogen-blended natural gas pipeline network is solved according to the obtained hydraulic parameters to obtain temperature parameters. The decoupling method of separate sequential solution of hydraulic equations and thermal equations can reduce the influence of thermal parameters on hydraulic parameters under complex hydraulic conditions to a certain extent, improve the stability of the calculation process, and use two small equation groups, hydraulic equation group A and thermal equation group B, to replace the original large equation group in the solution process, which can improve the calculation speed to a certain extent.

[0108] In order to further improve the efficiency of numerical simulation, the idea of ​​“divide and conquer” is adopted to solve the hydraulic equation group A and the thermal equation group B.

[0109] The "divide and conquer" solution method for the hydraulic equation A system is as follows:

[0110] First, the discrete equation (17) of the pipeline in the A equation group is pre-solved to obtain the relationship between the hydraulic parameters of each node in the pipeline and the free variables. The free variables are the starting pressure and the end mass flow of the pipeline. Then, the hydraulic equations (15), (16-1) to (16-3) of the non-pipeline elements in the pipeline network, the hydraulic equations (7) and (8) of the gas source and the hydraulic equations (10) and (11) of the connection point are combined to solve the hydraulic parameters of all the boundary nodes of the elements at one time. Finally, the obtained free variables are back-substituted into the relationship between the internal nodes of the pipeline and the free variables to obtain the hydraulic parameters of the internal nodes of the pipeline, thereby completing the hydraulic calculation of the entire pipeline network.

[0111] The "divide and conquer" solution method for the thermodynamic equation B is as follows:

[0112] Since the thermal equations are discretized using the upwind format, only the upstream temperature affects the downstream temperature during the solution. Therefore, in the solution process of the "divide and conquer" idea, only the temperature of the upstream boundary node can be selected as the free variable. First, the discrete equation (18) of the pipeline in the B equation group is pre-solved to obtain the relationship between the thermal parameters of each node in the pipeline and the free variable. The free variable is the temperature of the upstream boundary node; then the thermal equations (15), (16-4) to (16-6) of the non-pipeline elements in the pipeline network, the thermal equation (9) of the gas source and the thermal equation (12) of the connection point are combined to solve the thermal parameters of all element boundary nodes at one time; finally, the obtained free variables are substituted back into the relationship between the internal nodes of the pipeline and the free variables to obtain the thermal parameters of the internal nodes of the pipeline, thereby completing the thermal calculation of the entire pipeline network.

[0113] In an exemplary embodiment, the physical properties of the hydrogen-blended natural gas are calculated using the Modified Benedict-Webb-Rubin-Starling (BWRS) equation of state.

[0114] For example, in the numerical simulation calculation of the hydrogen-blended natural gas pipeline transportation process, the BWRS state equation is used to calculate the physical properties of the hydrogen-blended natural gas. The specific expression is as follows:

[0115]

[0116] Where p is the pressure of hydrogen-doped natural gas, in kPa; T is the temperature of hydrogen-doped natural gas, in K; ρ is the density of hydrogen-doped natural gas, in kmol / m 3 ; R is the gas constant, R = 8.3143 kJ / kmol·K; A 0 , B 0 , C 0 , D 0 、E 0 , a, b, c, d, α and γ are the 11 parameters of the BWRS state equation.

[0117] The solutions of related technologies mostly use commercial software for natural gas pipeline transportation simulation, such as Stoner Pipeline Simulator (SPS), but the applicability of the numerical simulation methods in these software to the hydrogen-blended natural gas pipeline transportation process is unknown, and the specific technical details are unknown. The numerical simulation method for the hydrogen-blended natural gas pipeline transportation process provided in the embodiment of the present application solves this problem. The mathematical model therein adopts a basic solution variable combination based on mass flow, pressure and temperature. The solution method adopts "sequential decoupling" based on a direct solver and an efficient solution technology based on "divide and conquer". The gas state equation fully considers the impact of hydrogen blending on the natural gas pipeline transportation characteristics, and accurately converts the performance curve of the centrifugal compressor under hydrogen blending conditions. The numerical simulation method for the hydrogen-blended natural gas pipeline transportation process provided in the embodiment of the present application can realize accurate and efficient numerical simulation of the hydrogen-blended natural gas pipeline transportation process, and has the characteristics of high calculation accuracy and efficiency, stable calculation, strong applicability, good scalability, etc., which can provide technical support for the formulation of hydrogen-blended natural gas pipeline transportation process in actual engineering.

[0118] The numerical simulation method for hydrogen-blended natural gas pipeline transportation process provided in the embodiment of the present application is used for simulation, assuming that the input parameters are as shown in Table 1.

[0119] Table 1

[0120]

[0121] The simulation of hydrogen-blended natural gas pipelines with a hydrogen-blended ratio of 0-100% is carried out. When the energy flow rate and the terminal pressure are constant, the pipeline gas volume (volume flow rate) and the outlet pressure change with the hydrogen-blended ratio. The calculation results are shown in Figure 2 and Figure 3 In addition, the simulation results of the pressure and temperature changes along the hydrogen-blended natural gas pipeline with the pipeline mileage when the hydrogen blending ratio is 0%, 10%, 20%, 30%, 50%, 80%, and 100% respectively are shown in Figure 4 and Figure 5 .

[0122] Depend on Figure 2 to Figure 5 , when the hydrogen blending ratio increases from 0 to 100%, the gas transmission volume of the pipeline increases with the increase of the hydrogen blending ratio, and the outlet pressure of the pipeline gradually increases. In the case of pure hydrogen (hydrogen blending ratio of 100%), the outlet pressure decreases. The reason is that although the volume flow rate increases and the friction increases when transporting pure hydrogen, the relative density of pure hydrogen is much smaller than that of hydrogen-blended natural gas. The larger the hydrogen blending ratio, the higher the outlet pressure of the pipeline. The outlet pressure of pure hydrogen is slightly lower for the same reason as above. As the hydrogen blending ratio increases, the degree to which the temperature along the pipeline gradually decreases with the pipeline mileage slows down, that is, hydrogen blending can slow down the degree to which the temperature drop along the pipeline is slowed down.

[0123] Figure 6This is a comparison chart of the computational efficiency when the hydrogen blending ratio is 0 using the numerical simulation method for the hydrogen blending natural gas pipeline transportation process provided by the embodiment of the present application and the commercial software SPS simulation. Figure 6 It shows that the CPU calculation time required by the SPS software is greater than that of the numerical simulation method for the hydrogen-blended natural gas pipeline transportation process provided by the embodiment of the present application, and the calculation efficiency of the numerical simulation method for the hydrogen-blended natural gas pipeline transportation process provided by the embodiment of the present application is better than that of the SPS software.

[0124] The embodiment of the present application also provides a numerical simulation device for hydrogen-blended natural gas pipeline transportation process, comprising: a memory and a processor, wherein the memory is used to store an executable program;

[0125] The processor is used to read and execute the executable program to implement the numerical simulation method for hydrogen-blended natural gas pipeline transportation process described in any of the above embodiments.

[0126] The numerical simulation device for the hydrogen-blended natural gas pipeline transportation process provided in the embodiment of the present application determines the first equation expression corresponding to the pipeline element in the hydrogen-blended natural gas pipeline network, the second equation expression corresponding to the non-pipeline element, the third equation expression corresponding to the gas source, and the fourth equation expression corresponding to the element connection point; for the time to be simulated, all equation expressions are solved to obtain the hydraulic parameters and thermal parameters in the hydrogen-blended natural gas pipeline network at the time to be simulated; when solving, the hydraulic equation group composed of the hydraulic equation expressions in all equation expressions is first solved, and then the thermal equation group composed of the thermal equation expressions in all equation expressions is solved. Therefore, all the determined equations are decoupled to form different equation groups, and then the different equation groups are solved separately in sequence, thereby reducing the difficulty of solving the process numerical values ​​of the simulation and improving the calculation rate.

[0127] It will be appreciated by those skilled in the art that all or some of the steps, systems, and functional modules / units in the disclosed methods above may be implemented as software, firmware, hardware, and appropriate combinations thereof. In hardware implementations, the division between the functional modules / units mentioned in the above description does not necessarily correspond to the division of physical elements; for example, a physical element may have multiple functions, or a function or step may be performed by several physical elements in cooperation. Some or all elements may be implemented as software executed by a processor, such as a digital signal processor or a microprocessor, or implemented as hardware, or implemented as an integrated circuit, such as an application-specific integrated circuit. Such software may be distributed on a computer-readable medium, which may include a computer storage medium (or non-transitory medium) and a communication medium (or temporary medium). As known to those skilled in the art, the term computer storage medium includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, program modules, or other data). Computer storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer. In addition, it is well known to those of ordinary skill in the art that communication media typically contain computer-readable instructions, data structures, program modules, or other data in a modulated data signal such as a carrier wave or other transport mechanism, and may include any information delivery media.

Claims

1. A numerical simulation method for hydrogen-blended natural gas pipeline transportation process, characterized in that: include: Determine a first equation expression corresponding to a pipeline element in a hydrogen-blended natural gas pipeline network, determine a second equation expression corresponding to a non-pipeline element, and determine a third equation expression corresponding to a gas source and a fourth equation expression corresponding to an element connection point; For the time to be simulated, the first equation expression, the second equation expression, the third equation expression and the fourth equation expression are solved to obtain the hydraulic parameters and thermal parameters in the hydrogen-blended natural gas pipeline network at the time to be simulated; when solving, the hydraulic equation group composed of the hydraulic equation expressions in all the equation expressions is first solved, and then the thermal equation group composed of the thermal equation expressions in all the equation expressions is solved.

2. The method according to claim 1, characterized in that The non-pipeline element includes: a compressor; when the non-pipeline element is the compressor, the equation expression corresponding to the non-pipeline element includes: an equation expression of the inlet pressure, the outlet pressure, and the flow rate obtained by converting the compressor performance curve under different hydrogen blending ratios using the first type similarity conversion method.

3. The method according to claim 1, characterized in that The method of determining the first equation expression corresponding to the pipeline element in the hydrogen-blended natural gas pipeline network includes: Determine an initial equation expression corresponding to the pipeline element; The initial equation expression corresponding to the pipeline element is linearized by using a Taylor expansion formula to obtain an intermediate equation expression; Using a finite difference method to discretize the intermediate equation expression corresponding to the pipeline element to obtain the first equation expression; The determining of the second equation expression corresponding to the non-pipeline element includes: Determining an initial equation expression corresponding to the non-pipeline element; The initial equation expression corresponding to the non-pipeline element is linearized using a Taylor expansion formula to obtain the second equation expression.

4. The method according to claim 3, characterized in that: The method of using the finite difference method to discretize the intermediate equation expression corresponding to the pipeline element includes: The non-steady-state terms of the continuity equation and the momentum equation in the intermediate equation expression are discretized by using a forward difference format, and the convection terms of the continuity equation and the momentum equation in the intermediate equation expression are discretized by using a central difference format; The non-steady-state term of the energy equation in the intermediate equation expression is discretized by using a forward difference format, and the convection term of the energy equation in the intermediate equation expression is discretized by using a first-order upwind format.

5. The method according to claim 4, characterized in that The step of solving the hydraulic equation group composed of hydraulic equation expressions in all equation expressions includes: The free variables are set as the starting pressure and the end mass flow of the pipeline, and the equation expressions of the pipeline elements in the hydraulic equations are pre-solved according to the thermodynamic parameters calculated last time and the pre-calculated physical properties of the hydrogen-blended natural gas, and the set free variables, to obtain the relationship between the hydraulic parameters of each node in the pipeline element and the free variables; wherein, when the hydraulic equations are solved for the first time, the thermodynamic parameters calculated last time are the pre-assumed thermodynamic parameters; The hydraulic parameters in the hydraulic equation group are solved using the obtained relationship between the hydraulic parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the hydraulic equation group.

6. The method according to claim 5, characterized in that The nodes include: boundary nodes and internal nodes, and the hydraulic parameters in the hydraulic equation group are solved by using the obtained relationship between the hydraulic parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the hydraulic equation group, including: According to the obtained relationship between the hydraulic parameters of each node in the pipeline element and the free variables, the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the hydraulic equation group are combined to solve the hydraulic parameters of the boundary nodes in all pipeline elements and non-pipeline elements; The hydraulic parameters of the boundary nodes of all pipeline elements and non-pipeline elements are substituted as free variables into the relationship between the hydraulic parameters of the internal nodes in the pipeline elements and the free variables to obtain the hydraulic parameters of the internal nodes in the pipeline elements.

7. The method according to claim 4, characterized in that The step of solving the thermodynamic equation group composed of thermodynamic equation expressions in all equation expressions includes: The free variable is set as the temperature of the upstream boundary node, and the equation expression of the pipeline element in the thermal equation group is pre-solved according to the obtained hydraulic parameters and the set free variables to obtain the relationship between the thermal parameters of each node in the pipeline element and the free variables; The thermodynamic parameters in the thermodynamic equation group are solved by using the obtained relationship between the thermodynamic parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the thermodynamic equation group.

8. The method according to claim 7, characterized in that The method of solving the thermal parameters in the thermal equation group by using the obtained relationship between the thermal parameters of each node in the pipeline element and the free variables and the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the thermal equation group comprises: According to the obtained relationship between the thermodynamic parameters of each node in the pipeline element and the free variables, the equation expressions corresponding to the non-pipeline element, the gas source and the element connection point in the thermodynamic equation group are combined to solve the thermodynamic parameters of the boundary nodes in all pipeline elements and non-pipeline elements; The obtained thermal parameters of the boundary nodes of all pipeline elements and non-pipeline elements are substituted as free variables into the relationship between the thermal parameters of the internal nodes in the pipeline elements and the free variables to obtain the thermal parameters of the internal nodes in the pipeline elements.

9. The method according to claim 5, characterized in that The physical properties of the hydrogen-blended natural gas are calculated using the BWRS state equation.

10. A numerical simulation device for hydrogen-blended natural gas pipeline transportation process, characterized in that: include: A memory and a processor, wherein the memory is used to store an executable program; The processor is used to read and execute the executable program to implement the numerical simulation method for hydrogen-blended natural gas pipeline transportation process according to any one of claims 1 to 9.

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