Multi-scale reactor core thermal state flow distribution calculation method and system

Abstract

The invention relates to the technical field of nuclear reactor thermal hydraulic power, in particular to a multi-scale reactor core thermal state flow distribution calculation method and system, and the method or system provided by the invention comprises the following steps: classifying according to geometric characteristics related to a reactor core, and calculating the thermal state flow distribution of the reactor core by changing the system pressure, the inlet flow and the total power of components. Obtaining a component fluid-solid coupling calculation result, and establishing an overall performance matrix of the component; according to the method, the internal rule of multi-scale coupling of the flow distribution of the reactor core is accurately grasped, and key links influencing the calculation speed of the flow distribution of the reactor core are grasped, so that a quick calculation scheme of the multi-scale flow distribution of the reactor core is provided. According to the method, the link with the maximum calculation time is independent, and corresponding calculation is carried out in advance through a problem decomposition scheme, so that a pre-calculation result can be called during engineering design calculation, and the design calculation speed is greatly improved.

Description

Technical Field

[0001] The present invention relates to the field of nuclear reactor thermal hydraulic technology, and in particular to a multi-scale core hot flow distribution calculation method and system. Background Art

[0002] like Figure 3 As shown in the figure, the tube-type fuel assembly and the flat-plate fuel assembly are used in some advanced research reactors at home and abroad due to their compact structure and high power density. This type of core is a typical multi-scale structure, namely, the core-assembly-subassembly-water gap / fuel plate hierarchical structure.

[0003] The core coolant distribution characteristics are the basis for heat transfer calculation and safety analysis, and are the key link affecting the economy and safety of core design. Due to the large number of water gaps inside special fuel assemblies, the number of parallel flow channels in the core is as high as several thousand. Due to the different shapes, the hydraulic characteristics of the flow channels in different components in the reactor are often very different. Even for the same component, due to the different heat sources at different positions in the reactor, its thermal hydraulic characteristics are also different. In addition, the shapes and heat sources of the gap flow channels between components of various shapes are also very different.

[0004] In the core engineering design, the calculation accuracy and speed must be considered at the same time, which increases the difficulty of the flow distribution calculation of the whole core. Moreover, with different operating tasks, the loading of each furnace varies greatly. These will affect the distribution of the flow field of the whole core, and then affect the temperature field. If you want to obtain the flow field and temperature field of each flow channel, you must couple all parallel flow channels for calculation. However, due to the large number of channels and large differences in channels, it is difficult to directly solve the whole core.

[0005] The processing method in the prior art is to classify various flow channels and merge the same type of flow channels into one channel. However, this method is relatively simple and it is difficult to obtain the true results of all channels. Summary of the invention

[0006] The present invention proposes a multi-scale core hot flow distribution calculation method and system based on the structural characteristics of fuel assemblies and cores, which separates the fluid-solid coupling calculation at the assembly scale, thereby greatly accelerating the flow distribution calculation speed in all coolant channels of the entire core to solve the problems in the prior art.

[0007] The embodiments of the present invention are implemented by the following technical solutions:

[0008] In a first aspect, the present invention provides a multi-scale core hot flow distribution calculation method, comprising:

[0009] Step 1: Classify the fuel assemblies according to their geometric characteristics based on the core’s geometric characteristics, and perform fluid-solid coupling calculations on the assemblies with the core’s rated parameters as the center;

[0010] Step 2: By changing the system pressure, inlet flow rate and total power of the component, the fluid-solid coupling calculation results of the component under different types and different thermal parameter input conditions are obtained, and the overall performance matrix of the component is established based on the fluid-solid coupling calculation results of the component;

[0011] Step 3: Initialize the component flow, interpolate the overall performance matrix of the component to obtain the total pressure drop and average pressure drop of the component, and determine whether the core flow distribution has converged;

[0012] Step 4: If converged, the iteration of the flow distribution of the entire core is completed. If not converged, the inlet flow values ​​of each component are changed again and step 3 is repeated until convergence.

[0013] Preferably, the overall performance matrix of the building block comprises:

[0014] The mapping relationship between thermal parameters and total pressure drop of components includes:

[0015]

[0016] Where p is the system pressure, W is the component inlet flow, N e is the total power of the components, Δp C,i is the total pressure drop of C type components, and i is a natural number.

[0017] Preferably, the initializing the component traffic includes:

[0018]

[0019] Where W I is the flow rate of the first component, W T is the total flow of the entire core, M is the total number of components, and ζ is the core bypass flow.

[0020] Preferably, the interpolation calculation of the overall performance matrix of the component to obtain the total pressure drop and the average pressure drop of the component includes:

[0021]

[0022] In the formula, Δp i is the total pressure drop of the ith component, Δp l is the total pressure drop of the lth component, Δp i+1 is the total pressure drop of the i+1th component, Δp i-1 is the total pressure drop of the i-1th component, Δp AVE is the average pressure drop.

[0023] Preferably, the determining whether the core flow distribution is convergent includes:

[0024] |Δp i +Δp I,R -Δp AVE |≤ε p

[0025] In the formula, Δp I,R The correction introduced to take into account the uneven pressure distribution of the upper and lower heads is ε p is the error limit, and |Δp i +Δp I,R -Δp AVE Is the result of | less than or equal to ε? p , if it is less than , it is converged, if it is greater than , it is not converged.

[0026] Preferably, the changing of the system pressure, the inlet flow rate and the total power of the components comprises:

[0027] Set the upper limit value and use the single variable control method to change only one variable at a time, and the step size of the variable change should be such that the change in the total pressure drop of the component does not exceed the upper limit value.

[0028] In a second aspect, the present invention further provides a multi-scale core hot flow distribution calculation system, comprising:

[0029] A calculation module is configured to classify the fuel assemblies according to geometric characteristics related to the core, and perform fluid-structure coupling calculation of the assemblies centered on the rated parameters of the core;

[0030] A matrix module is configured to obtain the fluid-solid coupling calculation results of the components under different types and different thermal parameter input conditions by changing the system pressure, inlet flow rate and total power of the components, and to establish an overall performance matrix of the components based on the fluid-solid coupling calculation results of the components;

[0031] The convergence judgment module is configured to initialize the component flow, interpolate the overall performance matrix of the component to obtain the total pressure drop and average pressure drop of the component, and judge whether the core flow distribution is converged; if converged, the full core flow distribution iteration is completed; if not converged, the inlet flow values ​​of each component are changed again until convergence;

[0032] The main control module is connected with the calculation module, the matrix module and the convergence judgment module, and is used to execute the above-mentioned multi-scale core hot flow distribution calculation method.

[0033] In a third aspect, the present invention provides a computer-readable storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned multi-scale core thermal flow distribution calculation method.

[0034] The technical solution of the embodiment of the present invention has at least the following advantages and beneficial effects:

[0035] The method or system provided by the present invention includes classifying the fuel assemblies according to the geometric characteristics involved in the core, obtaining the fluid-solid coupling calculation results of the assemblies by changing the system pressure, inlet flow and total power of the assemblies, and establishing the overall performance matrix of the assemblies; interpolating the overall performance matrix of the assemblies to obtain the total pressure drop and average pressure drop of the assemblies, and judging whether the core flow distribution has converged. Through the above method, the present invention accurately grasps the inherent law of multi-scale coupling of this type of core flow distribution, grasps the key link that affects the calculation speed of the core flow distribution, and thus proposes a fast calculation scheme for multi-scale core flow distribution. The most time-consuming link is separated out, and the corresponding calculation is carried out in advance through the problem decomposition scheme, so that the pre-calculated results can be called during the engineering design calculation, thereby greatly improving the design calculation speed. This plays an important role in quickly and accurately obtaining the flow distribution results of the full-scale core in engineering design. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0037] Figure 1 It is a schematic diagram of the process of the present invention;

[0038] Figure 2 It is the multi-scale coupling process of the present invention;

[0039] Figure 3 It is a schematic diagram of the structure of the fuel assembly of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0041] The division of modules in this application is a logical division. There may be other division methods when implemented in actual applications. For example, multiple modules can be combined or integrated into another system, or some features can be ignored or not executed.

[0042] The modules or submodules described independently may be physically separated or not: they may be implemented by software or hardware, and some modules or submodules may be implemented by software, and the processor may call the software to implement the functions of these modules or submodules, and other modules or submodules may be implemented by hardware, such as by hardware circuits. In addition, some or all of the modules may be selected according to actual needs to achieve the purpose of the present application.

[0043] like Figure 2 As shown in FIG. 1 , the common feature of fuel assemblies is that they are closed flow channels. The fuel is in a shell, and the interior of the fuel assembly is divided into independent water gaps (smallest coolant channels) by fuel plates.

[0044] Therefore, the flow distribution process of the core can be regarded as a typical multi-scale coupling process: the flow at the core inlet is first distributed to each component; and then the secondary distribution is carried out inside each component, that is, the flow distribution between each water gap. On the other hand, these two processes are not independent of each other, but coupled, because the flow heat transfer inside the water gap will affect the flow distribution inside the component; and the flow heat transfer characteristics inside the component will affect the flow distribution between the components of the core.

[0045] In the above process, the most time-consuming calculation is the fluid-solid coupling calculation at the component scale. It is necessary to repeatedly iterate between the fluid and the solid, and the fluid calculation again involves the iteration of the flow distribution inside the component, so the amount of calculation is large and the calculation is the most time-consuming. For this reason, the present invention separates this link, calculates it separately and stores the pressure drop results. When carrying out the core scale calculation, the calculation results of the component scale are directly called, which greatly speeds up the calculation speed of the flow distribution and lays the foundation for the application of this method in engineering design.

[0046] Please refer to Figure 1 The present invention provides a multi-scale core hot flow distribution calculation method, comprising:

[0047] Step 1: Classify the fuel assemblies according to their geometric characteristics based on the core’s geometric characteristics, and perform fluid-solid coupling calculations on the assemblies with the core’s rated parameters as the center;

[0048] The calculation of the two scales of the core coupled to each other is decomposed, and the most time-consuming component fluid-solid coupling calculation is carried out in advance. The present invention is essentially a time separation solution.

[0049] Pre-calculation, i.e., calculation of fluid-solid coupling of components. For the core scale, the main factor affecting the flow distribution between components is the total pressure drop of the channel. Therefore, the purpose of pre-calculation is to construct the total pressure drop of components corresponding to different parameters in advance.

[0050] First, the fuel assemblies are classified according to the geometric characteristics of the core design, and the category is recorded as C; then, the core rated parameters are used as the center to change the system pressure, inlet flow, and total power of the assembly to carry out the assembly fluid-solid coupling calculation, and the results are stored. The single variable control method is adopted, and only one variable is changed at a time, and the step size of the variable change is limited to the total pressure drop of the assembly not exceeding ±10%.

[0051] About Components Fluid-Structure Interaction calculations involve generating computational meshes for the fluid and solid regions. The fluid region typically uses a structured or unstructured mesh, while the solid region may require a finer mesh to capture the stress distribution.

[0052] Define the material properties of fluids and solids, including density, elastic modulus, viscosity, etc., and use numerical methods (such as finite element method or finite volume method) to solve the Navier-Stokes equations and continuity equations to obtain flow field parameters (velocity field, pressure field). According to the force exerted by the fluid on the solid (such as the pressure transmitted by the boundary conditions), solve the equilibrium equations of the solid to obtain the displacement field and stress field. Alternately solve the fluid and solid equations in each time step, and update the boundary conditions until convergence. Coupling can use explicit or implicit methods. Analyze the calculation results, including the flow characteristics, stress distribution, deformation, etc. of the fluid and solid.

[0053]

[0054] Where v is the flow velocity, p is the pressure, f is the external force, ρ is the fluid viscosity, and u is the kinematic viscosity.

[0055] Step 2: By changing the system pressure, inlet flow rate and total power of the component, the fluid-solid coupling calculation results of the component under different types and different thermal parameter input conditions are obtained, and the overall performance matrix of the component is established based on the fluid-solid coupling calculation results of the component;

[0056] Step 3: Initialize the component flow, interpolate the overall performance matrix of the component to obtain the total pressure drop and average pressure drop of the component, and determine whether the core flow distribution has converged;

[0057] Step 4: If converged, the iteration of the flow distribution of the entire core is completed. If not converged, the inlet flow values ​​of each component are changed again and step 3 is repeated until convergence.

[0058] The method or system provided by the present invention includes classifying the fuel assemblies according to the geometric characteristics involved in the core, obtaining the fluid-solid coupling calculation results of the assemblies by changing the system pressure, inlet flow and total power of the assemblies, and establishing the overall performance matrix of the assemblies; interpolating the overall performance matrix of the assemblies to obtain the total pressure drop and average pressure drop of the assemblies, and judging whether the core flow distribution has converged. Through the above method, the present invention accurately grasps the inherent law of multi-scale coupling of this type of core flow distribution, grasps the key link that affects the calculation speed of the core flow distribution, and thus proposes a fast calculation scheme for multi-scale core flow distribution. The most time-consuming link is separated out, and the corresponding calculation is carried out in advance through the problem decomposition scheme, so that the pre-calculated results can be called during the engineering design calculation, thereby greatly improving the design calculation speed. This plays an important role in quickly and accurately obtaining the flow distribution results of the full-scale core in engineering design.

[0059] The core is to decompose the fluid-solid coupling heat transfer process at the component scale, which is the most time-consuming and difficult calculation link in the multi-scale coupling problem, and to carry out pre-calculation in advance and form a corresponding calculation result library for iterative calculation at the core scale. This is a space-for-time solution. Calculation speed and accuracy are the life of engineering design calculations. The present invention solves the feasibility problem of this engineering problem through spatial separation.

[0060] In addition, the single variable control method is adopted, and only one variable is changed at a time, and the step size of the variable change is limited to the voltage drop change amplitude of the component not exceeding ±10%. Since the influence of each variable on the voltage drop is not linear, this principle can select the change step size of the independent variable according to the actual influence degree of each independent variable on the basis of ensuring the subsequent interpolation accuracy, further saving the amount of calculation. (It is not a fixed step size, but a variable step size is selected according to the degree of influence on the voltage drop. The step size is increased for the variable interval with small influence, which reduces the amount of calculation, reduces the size of the result matrix, and saves storage space).

[0061] In an exemplary embodiment of the present invention, establishing an overall performance matrix of a component includes:

[0062] The mapping relationship between thermal parameters and total pressure drop of components includes:

[0063]

[0064] Where p is the system pressure, W is the inlet flow rate, N e is the total power of the components, Δp C,i Total pressure drop for Type C components.

[0065] In this embodiment, the independent variables only consider the key factors affecting the pressure drop of the assembly, which can save the workload of pre-calculation and reduce the dimension of the result matrix. The result variable is the pressure drop of the assembly, which is a key parameter affecting the flow distribution calculation of the core scale.

[0066] In an exemplary embodiment of the present invention, the difference in flow between components is mainly caused by power distribution. Therefore, at the beginning of iteration, it can be assumed that the inlet flow of each component is equal to each other. Therefore, initializing the component flow includes:

[0067]

[0068] Where W I is the flow rate of the first component, W T is the total flow rate of the whole core, M is the total number of components, is the core bypass leakage flow, the value of ζ is very small and can be determined by experiment, and is approximately a constant.

[0069] In an exemplary embodiment of the present invention, interpolating the overall performance matrix of the component to obtain the total pressure drop and the average pressure drop of the component includes:

[0070]

[0071] In the formula, Δp i is the total pressure drop of the ith component, Δp l is the total pressure drop of the first component, Δp i+1 is the total pressure drop of the i+1th component, Δp i-1 is the total pressure drop of the i-1th component, Δp AVE is the average pressure drop.

[0072] In an exemplary embodiment of the present invention, the determining whether the core flow distribution is convergent includes:

[0073] Generally, the above initial flow value cannot make the pressure drop of the channel meet the pre-given constraints, namely:

[0074] |Δp i -Δp AVE |≤ε p

[0075] In the formula, ε p is the error limit, and |Δp i -Δp AVE Is the result of | less than or equal to ε? p , if it is less than , it is converged, if it is greater than , it is not converged.

[0076] Because the pressure field of the upper and lower heads of the core may be unevenly distributed, the pressure drop of each component varies depending on its location. For this reason, the head pressure loss can be added:

[0077] |Δp i +Δp I,R -Δp AVE |≤ε p

[0078] Δp I,R The correction amount is introduced to take into account the uneven pressure distribution of the upper and lower heads. The criterion proposed by the present invention can accurately consider the impact of the uneven pressure field of the upper and lower heads. This value can be obtained through hydraulic experiments and numerical calculations.

[0079] Specifically, changes in system pressure, inlet flow, and total component power include:

[0080] An upper limit value is set, and a single variable control method is used to change only one variable at a time, and the step size of the variable change is such that the change amplitude of the total pressure drop of the component does not exceed the upper limit value. The upper limit value is 10% in this embodiment.

[0081] In addition, to obtain the internal parameters of the component, the component pressure drop obtained in step 2 is used as a pointer to search the result library with a similar pre-calculated pressure drop in step 1, and the detailed calculation results of the specified type of component can be obtained, including fluid parameters and fuel plate thermal conductivity results.

[0082] In a second aspect, the present invention further provides a multi-scale core hot flow distribution calculation system, comprising:

[0083] A calculation module is configured to classify the fuel assemblies according to geometric characteristics related to the core, and perform fluid-structure coupling calculation of the assemblies centered on the rated parameters of the core;

[0084] A matrix module is configured to obtain the fluid-solid coupling calculation results of the components under different types and different thermal parameter input conditions by changing the system pressure, inlet flow rate and total power of the components, and to establish an overall performance matrix of the components based on the fluid-solid coupling calculation results of the components;

[0085] The convergence judgment module is configured to initialize the component flow, interpolate the overall performance matrix of the component to obtain the total pressure drop and average pressure drop of the component, and judge whether the core flow distribution is converged; if converged, the full core flow distribution iteration is completed; if not converged, the inlet flow values ​​of each component are changed again until convergence;

[0086] The main control module is connected with the calculation module, the matrix module and the convergence judgment module, and is used to execute the above-mentioned multi-scale core hot flow distribution calculation method.

[0087] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0088] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. The computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A multi-scale core hot flow distribution calculation method, characterized in that: include: Step 1: Classify the fuel assemblies according to their geometric characteristics based on the core’s geometric characteristics, and perform fluid-solid coupling calculations on the assemblies with the core’s rated parameters as the center; Step 2: By changing the system pressure, inlet flow rate and total power of the component, the fluid-solid coupling calculation results of the component under different types and different thermal parameter input conditions are obtained, and the overall performance matrix of the component is established based on the fluid-solid coupling calculation results of the component; Step 3: Initialize the component flow, interpolate the overall performance matrix of the component to obtain the total pressure drop and average pressure drop of the component, and determine whether the core flow distribution has converged; Step 4: If converged, the iteration of the flow distribution of the entire core is completed. If not converged, the inlet flow values ​​of each component are changed again and step 3 is repeated until convergence.

2. A multi-scale core hot flow distribution calculation method according to claim 1, characterized in that: The overall performance matrix of the building components includes: The mapping relationship between thermal parameters and total pressure drop of components includes: Where p is the system pressure, W is the inlet flow rate, N e is the total power of the components, Δp 2,i is the total pressure drop of type C components.

3. A multi-scale core hot flow distribution calculation method according to claim 2, characterized in that: Initializing the component traffic includes: Where W I is the flow rate of the first component, W T is the total flow rate of the whole core, M is the total number of components, is the core bypass leakage flow.

4. A multi-scale core hot flow distribution calculation method according to claim 3, characterized in that: The interpolation calculation of the overall performance matrix of the component to obtain the total pressure drop and the average pressure drop of the component includes: In the formula, Δp i is the total pressure drop of the ith component, Δp l is the total pressure drop of the lth component, Δp i+1 is the total pressure drop of the i+1th component, Δp i-1 is the total pressure drop of the i-1th component, Δp AVE is the average pressure drop.

5. A multi-scale core hot flow distribution calculation method according to claim 4, characterized in that: The determining whether the core flow distribution is convergent comprises: |Δp i +Δp I,R -Δp AVE |≤ε p In the formula, Δp I,R The correction introduced to take into account the uneven pressure distribution of the upper and lower heads is ε p is the error limit, and |Δp i +Δp I,R -Δp AVE Is the result of | less than or equal to ε? p , if it is less than , it is converged, if it is greater than , it is not converged.

6. A multi-scale core hot flow distribution calculation method according to claim 4, characterized in that: The changes in system pressure, inlet flow and total component power include: Set the upper limit value and use the single variable control method to change only one variable at a time. The step size of the variable change is based on the fact that the change in the total voltage drop of the component does not exceed the upper limit value.

7. A multi-scale core hot flow distribution calculation system, characterized in that: include: A calculation module is configured to classify the fuel assemblies according to geometric characteristics related to the core, and perform fluid-structure coupling calculation of the assemblies centered on the rated parameters of the core; A matrix module is configured to obtain the fluid-solid coupling calculation results of the components under different types and different thermal parameter input conditions by changing the system pressure, inlet flow rate and total power of the components, and to establish an overall performance matrix of the components based on the fluid-solid coupling calculation results of the components; The convergence judgment module is configured to initialize the component flow, interpolate the overall performance matrix of the component to obtain the total pressure drop and average pressure drop of the component, and judge whether the core flow distribution is converged; if converged, the full core flow distribution iteration is completed; if not converged, the inlet flow values ​​of each component are changed again, and step three is repeated until convergence; A main control module is connected to the calculation module, the matrix module and the convergence judgment module, and is used to execute a multi-scale core hot flow distribution calculation method as described in any one of claims 1-6.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the computer program implements a multi-scale core hot flow distribution calculation method according to any one of claims 1 to 6.

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