CN114880969A - In-stack flow field flow characteristic and fluid excitation simulation method based on data driving - Google Patents
In-stack flow field flow characteristic and fluid excitation simulation method based on data driving Download PDFInfo
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Abstract
The invention discloses a data-driven in-pile flow field flow characteristic and fluid excitation simulation method, which comprises the following steps: establishing a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel between structural design parameters and flow velocity distribution; establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel; establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model; and (4) performing transient CFD simulation according to the combined fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
Description
Technical Field
The invention relates to the technical field of nuclear reactor engineering, in particular to a data-driven in-reactor flow field flow characteristic and fluid excitation simulation method.
Background
The large pressurized water reactor core is composed of tens of thousands of fuel rods, the fuel rods are supported by a plurality of layers of grillworks which are fully distributed with fins, and the lower reactor internals such as a flow distribution device and the like are added, so that the flow field in the reactor is extremely complex, and the flow characteristics and the fluid excitation at each position in the flow field are difficult to accurately obtain. Experimental studies and CFD simulations are two main means of acquiring in-pile flow data. High-precision flow data can be obtained through experiments, but the experiment cost is high, and the number and the positions of measuring points are limited. Parallel and supercomputing techniques make CFD simulation available for large-scale flow field analysis, but their computational cost is still not suitable for real-time health monitoring oriented to digital twins.
Disclosure of Invention
In order to solve the problems of the defects and shortcomings of the prior art, the invention provides a data-driven in-pile flow field flow characteristic and fluid excitation simulation method.
In order to achieve the purpose of the invention, the technical scheme is as follows:
a simulation method based on flow characteristics and fluid excitation of a data-driven in-stack flow field comprises the following steps:
s1: establishing a static reduced-order model of a flow field of a lower end socket of the pressure vessel between the structural design parameters and the flow velocity distribution so as to realize the output of the inlet flow velocity distribution characteristics of the reactor core under any given structural design parameters;
s2: establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel;
s3: establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model;
s4: and (4) performing transient CFD simulation according to the combination of the fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
Preferably, the establishment of the static reduced-order model of the flow field of the lower head of the pressure vessel comprises the following steps:
s101: first, a set of orthonormal bases in the space Ψ spanned by the snapshots is found
Make the collection
The projection of the element(s) on this set of basis is maximal, and the mathematical formula is:
where phi is the base vector, U (i) Taking a snapshot, k is a count, and the number of i vectors;
s102, aiming at CFD calculation results under different structural design parameters, extracting a flow main mode by adopting intrinsic orthogonal decomposition and spectrum intrinsic orthogonal decomposition and combining the formula (1);
s103, calibrating the simulation data by adopting a data fusion method according to the existing engineering experiment data as a reference, and correcting the flowing main mode;
s104, performing secondary decomposition on the main flow modes under different parameters by adopting intrinsic orthogonal decomposition and spectral intrinsic orthogonal decomposition, and calculating the weight corresponding to each main mode;
s105: aiming at the reactor core inlet flow velocity under different structural design parameters, acquiring the flow velocity index of the reactor core inlet by adopting statistical analysis;
s106: and constructing a static reduced-order model of the flow field of the lower end enclosure of the pressure vessel between the structural design parameters and the flow rate indexes based on a system identification method, and realizing the flow rate distribution of the inlet of the reactor core under any given design parameter.
Further, when a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel is established, a calculation domain comprises a water inlet pipe, a descending cavity and a reactor core; a reactor core porous medium model is adopted to simulate a downstream lower head flow field;
and (3) connecting the upstream reactor core porous medium model and the pressure vessel lower head flow field static reduced model in series to form an integral in-reactor flow field analysis model.
Preferably, the sample library of the fuel assembly passage reduced-order model is derived from CFD simulation calculation and visualization experiments.
Further, the visual experiment adopts an experiment body to carry out the experiment, and the experiment body comprises an inlet section, an experiment section and an outlet section;
a grid plate is arranged in the inlet section to reduce the flow interference at the upstream of the experiment body;
an experimental part is arranged in the experimental section, the experimental part comprises 1 row of 3 small assemblies, and each small assembly is a 4 x 4 rod bundle; the rod bundle consists of a plurality of fuel rods which are arranged at equal intervals; the middle of the rod bundle is provided with a positioning grid support with stirring wings.
Still further, the structural features within the sub-passageways include the number of grids, the location, and the size, shape and inclination of the agitating vanes.
And further, when the fuel assembly sub-channel flow field reduced model is established, a sample library of the fuel assembly sub-channel flow field reduced model is derived from transient CFD simulation calculation results, sub-channel level flow field observation results of a fusion SPIV experiment, and existing experimental data and empirical data of fluid force acting on the fuel rod.
Further, the specific steps of establishing the fuel assembly sub-channel flow field reduced model are as follows:
s301: based on a finite propagation model, carrying out transient CFD calculation of 3 multiplied by 3 sub-channels in a single group of 4 multiplied by 4 rod bundles according to an experiment body of a visual experiment, verifying finite propagation in the rod bundle structure, determining a turbulent flow pulsation propagation distance, and minimizing the number of the sub-channels according to the calculated turbulent flow pulsation propagation distance;
s302: dividing the sub-channel into a middle sub-channel and a component peripheral sub-channel according to the position of the sub-channel and the flow channel, and correspondingly calculating turbulence force and fluid elasticity through transient CFD (computational fluid dynamics) simulation aiming at the sub-channels of different types;
s303: acquiring time-average distribution, pulsation amplitude distribution and pulsation frequency band distribution of turbulent force by adopting statistical analysis and a frequency domain method aiming at inlet flow velocity distribution of different sub-channels;
s304: a fuel assembly sub-channel flow field reduced-order model is constructed based on a system identification method so as to output turbulent flow force characteristics of flow velocity of any given stator channel inlet.
Still further, for the intermediate sub-channel, the turbulence force is calculated by transient CFD simulation, as follows:
setting the interface of the fuel rod and the flow field as a fixed boundary, and carrying out transient flow field simulation by adopting an LES model; the calculation time step length is set to be 1 ms; in the simulation process, Euler measuring points are arranged in the middle sub-channel, a flow snapshot is extracted, and typical working conditions are selected to be compared with visual experiment result data;
and a plurality of turbulence pulsating pressure monitoring points are arranged on the wall surfaces of the fuel rods and the guide pipe in the middle sub-channel to obtain the distribution rule of the turbulence force in the axial direction of the assembly, so that transient CFD (computational fluid dynamics) simulation calculation of the turbulence force is completed.
Still further, for the component peripheral sub-channel, the flow elasticity is calculated through transient CFD simulation, specifically as follows:
characterizing the fluid-solid coupling effect according to two regions, namely a first inter-component flow channel approximately for inter-plate flow and a second inter-component flow channel for inter-rod bundle flow;
when the flow elasticity is calculated through transient CFD simulation, the movement displacement and the speed of a structural interface in a peripheral sub-channel of the assembly are given, the flow elasticity is calculated by adopting a moving grid technology and is converted into three fluid-solid coupling effects of additional rigidity, additional damping and additional mass; and determining the fluid-solid coupling effect through transient CFD simulation calculation, and verifying through the experimental results of the vibration characteristics of the rod bundle measured in air, still water and moving water.
The invention has the following beneficial effects:
the invention provides a method for researching flow characteristics and fluid excitation of a flow field in a reactor based on data driving, which is characterized by constructing a static reduced-order model of the flow field of a lower end socket of a pressure container based on CFD simulation data and visual experimental data, sequentially establishing a fuel assembly channel reduced-order model and a fuel assembly sub-channel flow field reduced-order model through the static reduced-order model of the flow field of the lower end socket of the pressure container, and calculating turbulent force and fluid elasticity by transient CFD simulation according to the reduced-order model of the flow field of the fuel assembly sub-channel, thereby greatly reducing the calculation cost of complex flow fields in the reactor and solving the problem that the flow characteristics and the fluid excitation characteristics of complex flow fields are difficult to describe.
Drawings
Fig. 1 is a schematic diagram of a data-driven in-stack flow field reduced-order model according to an embodiment of the present invention.
Fig. 2 is a schematic diagram of SPIV optical imaging provided by an embodiment of the present invention.
FIG. 3 is a schematic diagram of an experimental body provided by an embodiment of the present invention.
FIG. 4 is a schematic view of a 4X 4 rod cluster trial provided by an embodiment of the present invention.
FIG. 5 is a top view of a 4X 4 rod cluster trial provided by an embodiment of the present invention.
Figure 6 is a top view of a grid provided by an embodiment of the present invention.
Fig. 7 is a schematic view of a calculation of a flow field of a sub-channel provided in an embodiment of the present invention.
Fig. 8 is a partial enlarged view at C in fig. 7.
Fig. 9 is a schematic view of a flow path between adjacent modules according to an embodiment of the present invention.
Fig. 10 is a partial enlarged view at a in fig. 9.
Fig. 11 is a partial enlarged view at B in fig. 9.
Detailed Description
The invention is described in detail below with reference to the drawings and the detailed description.
Example 1
As shown in fig. 1, a data-driven in-stack flow field flow characterization and fluid excitation simulation method includes the following steps:
s1: establishing a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel between the structural design parameters and the flow velocity distribution so as to realize the output of the flow velocity distribution characteristics of the inlet of the reactor core under any given structural design parameters;
s2: establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel;
s3: establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model;
s4: and (4) performing transient CFD simulation according to the combination of the fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
Example 2
As shown in fig. 1, a data-driven in-stack flow field flow characterization and fluid excitation simulation method includes the following steps:
s1: establishing a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel between the structural design parameters and the flow velocity distribution so as to realize the output of the flow velocity distribution characteristics of the inlet of the reactor core under any given structural design parameters;
s2: establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel;
s3: establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model;
s4: and (4) performing transient CFD simulation according to the combination of the fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
In a specific embodiment, the establishment of the static reduced-order model of the flow field of the lower head of the pressure vessel comprises the following steps:
s101: first, a set of orthonormal bases in the space Ψ spanned by the snapshot is found
Make the collection
The projection of the element in (b) on the group of basis is maximum, and the mathematical formula is
Where phi is the base vector, U (i) Taking a snapshot, k is a count, and the number of i vectors;
s102, extracting a main flow mode by combining an intrinsic orthogonal decomposition and a spectrum intrinsic orthogonal decomposition with a formula (1) according to CFD calculation results under different structural design parameters; according to the CFD simulation data, selecting the working condition with the maximum flow to compare with the existing engineering experiment result data, and repeatedly performing iterative calculation to obtain high-precision flow field calculation data;
s103, calibrating CFD simulation data by using a data fusion method according to the existing engineering experiment data as a reference, and correcting the flowing main mode;
s104, performing secondary decomposition on the main flow modes under different parameters by adopting intrinsic orthogonal decomposition and spectral intrinsic orthogonal decomposition to obtain more uniform flow modes, and calculating the weight corresponding to each main mode; the weight refers to the proportion of a single main mode in the total mode.
S105: aiming at the reactor core inlet flow velocity under different structural design parameters, acquiring the flow velocity index of the reactor core inlet by adopting statistical analysis; representative flow rate indicators include time-averaged flow rate distribution, flow rate, and flow rate.
S106: and constructing a static reduced-order model of the flow field of the lower end enclosure of the pressure vessel between the structural design parameters and the flow rate indexes based on a system identification method, and realizing the flow rate distribution of the inlet of the reactor core under any given design parameter.
Further, when a static reduced-order model of a flow field of a lower head of the pressure vessel is established, in order to ensure that the internal flow of the lower head has accurate upstream and downstream boundary conditions, a calculation domain comprises a water inlet pipe, a descending cavity and a reactor core; the reactor core flow field is very complex, and the research of the non-lower head flow field reduced model is focused, and a reactor core porous medium model is adopted to simulate the downstream lower head flow field;
and (3) connecting the upstream reactor core porous medium model and the pressure vessel lower head flow field static reduced model in series to form an integral in-reactor flow field analysis model.
In the embodiment, an upstream reactor core porous medium model and a pressure vessel lower head flow field static order-reducing model are connected in series, and the output of the reactor core porous medium model is used as the input of the pressure vessel lower head flow field static order-reducing model to be combined together to form an integral in-reactor flow field analysis model.
Example 3
As shown in fig. 1, a data-driven in-stack flow field flow characterization and fluid excitation simulation method includes the following steps:
s1: establishing a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel between the structural design parameters and the flow velocity distribution so as to realize the output of the flow velocity distribution characteristics of the inlet of the reactor core under any given structural design parameters;
s2: establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel;
s3: establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model;
s4: and (4) performing transient CFD simulation according to the combination of the fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
See example 2 for a detailed description of step S1, this example will explain step S2:
the sample library of the fuel assembly passage reduced-order model is derived from CFD simulation calculation and visualization experiment (SPIV).
In a specific embodiment, as shown in fig. 2, a visualization experiment SPIV is used to measure the flow field in a row of 3 groups of rod bundle channels, the visualization experiment is performed by using an experiment body, and the experiment body comprises an inlet section, an experiment section and an outlet section; as shown in fig. 3, 4, 5, 6.
A grid plate is arranged in the inlet section to reduce the flow interference at the upstream of the experiment body;
an experimental part is arranged in the experimental section, the experimental part comprises 1 row of 3 small assemblies, and each small assembly is a 4 x 4 rod bundle; the rod bundle consists of a plurality of fuel rods which are arranged at equal intervals; the middle of the rod bundle is provided with a positioning grid support with stirring wings. The height of the bundle is 1100mm, with 520mm upstream of the grid and 540mm downstream of the grid, the height of the grid being 40 mm. The upper part of the rod bundle adopts perfluoroethylene propylene copolymer (FEP) as a pipe wall material, and water is filled in the pipe. The problems of rod bundle and water refractive index difference and rod bundle scale effect are solved by a refractive index compensation technology. The influence of structural motion on the flow field is not considered in the visualization experiment, the actuator connected with the middle rod bundle grid frame in the experiment body does not act, and the effect of fixing the grid frame is achieved, so that the stability of the flow channel boundary in the experiment process is kept as much as possible. In one embodiment, the structural features within the sub-passageways include the number of grids, the location, and the size, shape and inclination of the agitating vanes.
Example 4
As shown in fig. 1, a data-driven in-stack flow field flow characterization and fluid excitation simulation method includes the following steps:
s1: establishing a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel between the structural design parameters and the flow velocity distribution so as to realize the output of the flow velocity distribution characteristics of the inlet of the reactor core under any given structural design parameters;
s2: establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel;
s3: establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model;
s4: and (4) performing transient CFD simulation according to the combination of the fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
The step S1 is specifically described in example 2, the step S2 is specifically described in example 3, and this example specifically describes the step S2:
when the fuel assembly sub-channel flow field reduced model is established, a sample library of the fuel assembly sub-channel flow field reduced model is derived from transient CFD simulation calculation results, sub-channel level flow field observation results of fusion SPIV experiments, and existing experimental data and empirical data of fluid force acting on fuel rods.
In one specific embodiment, as shown in fig. 7, 8, 9, 10, and 11, the specific steps for establishing the fuel assembly sub-channel flow field reduced-order model are as follows:
s301: based on a limited propagation model and according to an experiment body of a visual experiment, carrying out transient CFD calculation on 3 multiplied by 3 sub-channels in a single group of 4 multiplied by 4 rod bundles, verifying limited propagation in the rod bundle structure, determining a turbulent flow pulse propagation distance, and minimizing the number of the sub-channels according to the calculated turbulent flow pulse propagation distance;
s302: dividing the sub-channel into a middle sub-channel and a component peripheral sub-channel according to the position of the sub-channel and the flow channel, and correspondingly calculating turbulence force and fluid elasticity through transient CFD simulation aiming at the sub-channels of different types; through trial calculation and combination of the existing experimental actual measurement data and turbulent force engineering empirical data, the turbulent force obtained by calculating the mean flow rate at the reactor core inlet is considered and further corrected.
S303: acquiring time-average distribution, pulsation amplitude distribution and pulsation frequency band distribution of turbulent force by adopting statistical analysis and a frequency domain method aiming at inlet flow velocity distribution of different sub-channels;
s304: a fuel assembly sub-channel flow field reduced-order model is constructed based on a system identification method so as to achieve turbulent force characteristics of flow velocity output to any given stator channel inlet. The transient CFD simulation calculation result of the turbulence force is fused with the SPIV experiment sub-channel level observation data, and the PSD of the turbulence force of the fuel rod in the engineering project is used as data supplement.
In a specific embodiment, turbulence forces are calculated by transient CFD simulation for the intermediate sub-channel as follows:
setting the interface of the fuel rod and the flow field as a fixed boundary, and carrying out transient flow field simulation by adopting an LES model; the calculation time step length is set to be 1 ms; in the simulation process, Euler measuring points are arranged in the middle sub-channel, a flow snapshot is extracted, and typical working conditions are selected to be compared with visual experiment result data so as to obtain high-precision flow data;
and a plurality of turbulence pulsating pressure monitoring points are arranged on the wall surfaces of the fuel rods and the guide pipe in the middle sub-channel to obtain the distribution rule of turbulence force in the axial direction of the assembly. Thereby completing transient CFD simulation to calculate turbulence force.
In a specific embodiment, the flow elasticity is calculated by transient CFD simulation for the component peripheral sub-channel as follows:
characterizing the fluid-solid coupling effect according to two regions, namely a first inter-component flow channel approximately for inter-plate flow and a second inter-component flow channel for inter-rod bundle flow;
when the flow elasticity is calculated through transient CFD simulation, the movement displacement and the speed of a structural interface in a peripheral sub-channel of the assembly are given, the flow elasticity is calculated by adopting a moving grid technology and is converted into three fluid-solid coupling effects of additional rigidity, additional damping and additional mass; and determining the fluid-solid coupling effect through transient CFD simulation calculation, and verifying through the experimental results of the vibration characteristics of the rod bundle measured in air, still water and moving water.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (10)
1. A simulation method of flow characteristics and fluid excitation of an in-stack flow field based on data driving is characterized in that: the method comprises the following steps:
s1: establishing a static reduced-order model of a flow field of a lower end enclosure of the pressure vessel between the structural design parameters and the flow velocity distribution so as to realize the output of the flow velocity distribution characteristics of the inlet of the reactor core under any given structural design parameters;
s2: establishing a fuel assembly channel reduced model for predicting flow field distribution in the fuel assembly, wherein the input of the fuel assembly channel reduced model comprises flow velocity distribution characteristics on the fluid boundary of the fuel assembly channel and structural characteristics in a flow channel, and the output of the fuel assembly channel reduced model is the flow velocity distribution characteristics of each sub-channel in the assembly channel;
s3: establishing a fuel assembly sub-channel flow field reduced model with the input of flow velocity distribution characteristics of one sub-channel and structural characteristics in one sub-channel and the output of turbulent force and fluid elasticity distribution characteristics acting on the boundary of one sub-channel, wherein the fuel assembly sub-channel flow field reduced models of different sub-channels in the fuel assembly are connected in parallel to form the fuel assembly channel reduced model;
s4: and (4) performing transient CFD simulation according to the combination of the fuel assembly sub-channel flow field reduced model to calculate turbulent force and flow elasticity.
2. The data-driven in-stack flow field flow characterization and fluid excitation-based simulation method of claim 1, wherein: the method for establishing the static reduced-order model of the flow field of the lower end socket of the pressure vessel comprises the following steps:
s101: first, a set of orthonormal bases in the space Ψ spanned by the snapshot is found
Make the collection
The projection of the element(s) on this set of basis is maximal, and the mathematical formula is:
where phi is the base vector, U (i) Taking a snapshot, k is a count, and the number of vectors i;
s102, extracting a main flow mode by combining an intrinsic orthogonal decomposition and a spectrum intrinsic orthogonal decomposition with a formula (1) according to CFD calculation results under different structural design parameters;
s103, calibrating the simulation data by adopting a data fusion method according to the existing engineering experiment data as a reference, and correcting the flowing main mode;
s104, carrying out secondary decomposition on the main flow modes under different parameters by adopting intrinsic orthogonal decomposition and spectral intrinsic orthogonal decomposition, and calculating the weight corresponding to each main mode;
s105: aiming at the reactor core inlet flow velocity under different structural design parameters, acquiring the flow velocity index of the reactor core inlet by adopting statistical analysis;
s106: and constructing a static reduced-order model of the flow field of the lower end enclosure of the pressure vessel between the structural design parameters and the flow rate indexes based on a system identification method, and realizing the flow rate distribution of the inlet of the reactor core under any given design parameter.
3. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 2, wherein: when a static reduced-order model of a flow field of a lower end socket of the pressure vessel is established, a calculation domain comprises a water inlet pipe, a descending cavity and a reactor core; a reactor core porous medium model is adopted to simulate a downstream lower head flow field;
and (3) connecting the upstream reactor core porous medium model and the pressure vessel lower head flow field static reduced model in series to form an integral in-reactor flow field analysis model.
4. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 1, wherein: the sample library of the fuel assembly passage reduced-order model is derived from CFD simulation calculation and visualization experiments.
5. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 4, wherein: the visual experiment adopts an experiment body to carry out experiment, and the experiment body comprises an inlet section, an experiment section and an outlet section;
a grid plate is arranged in the inlet section to reduce the flow interference at the upstream of the experiment body;
an experimental part is arranged in the experimental section, the experimental part comprises 1 row of 3 small assemblies, and each small assembly is a 4 x 4 rod bundle; the rod bundle consists of a plurality of fuel rods which are arranged at equal intervals; the middle of the rod bundle is provided with a positioning grid support with stirring wings.
6. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 5, wherein: the structural features in the sub-channels include the number and location of the grids, and the size, shape and inclination of the agitating vanes.
7. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 6, wherein: when the fuel assembly sub-channel flow field reduced model is established, a sample library of the fuel assembly sub-channel flow field reduced model is derived from transient CFD simulation calculation results, sub-channel level flow field observation results of fusion SPIV experiments, and existing experimental data and empirical data of fluid force acting on fuel rods.
8. The data-driven in-stack flow field flow characterization and fluid stimulation simulation-based method of claim 7, wherein: the specific steps of establishing the fuel assembly sub-channel flow field reduced model are as follows:
s301: based on a finite propagation model, carrying out transient CFD calculation of 3 multiplied by 3 sub-channels in a single group of 4 multiplied by 4 rod bundles according to an experiment body of a visual experiment, verifying finite propagation in the rod bundle structure, determining a turbulent flow pulsation propagation distance, and minimizing the number of the sub-channels according to the calculated turbulent flow pulsation propagation distance;
s302: dividing the sub-channel into a middle sub-channel and a component peripheral sub-channel according to the position of the sub-channel and the flow channel, and correspondingly calculating turbulence force and fluid elasticity through transient CFD simulation aiming at the sub-channels of different types;
s303: acquiring time-average distribution, pulsation amplitude distribution and pulsation frequency band distribution of turbulent force by adopting statistical analysis and a frequency domain method aiming at inlet flow velocity distribution of different sub-channels;
s304: a fuel assembly sub-channel flow field reduced-order model is constructed based on a system identification method so as to achieve turbulent force characteristics of flow velocity output to any given stator channel inlet.
9. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 8, wherein: calculating turbulence force by transient CFD simulation aiming at the middle sub-channel, wherein the turbulence force is specifically as follows:
setting the interface of the fuel rod and the flow field as a fixed boundary, and carrying out transient flow field simulation by adopting an LES model; the calculation time step length is set to be 1 ms; in the simulation process, Euler measuring points are arranged in the middle sub-channel, a flow snapshot is extracted, and typical working conditions are selected to be compared with visual experiment result data;
arranging a plurality of turbulent pulsating pressure monitoring points on the wall surfaces of the fuel rods and the guide pipe in the middle sub-channel to obtain the distribution rule of turbulent force in the axial direction of the assembly; thereby completing transient CFD simulation to calculate turbulence force.
10. The data-driven in-stack flow field flow characterization and fluid stimulation simulation method of claim 8, wherein: aiming at the peripheral sub-channel of the component, the flow elasticity is calculated through transient CFD simulation, and the method specifically comprises the following steps:
characterizing the fluid-solid coupling effect according to two regions, namely a first inter-component flow channel approximately for inter-plate flow and a second inter-component flow channel for inter-rod bundle flow;
when the flow elasticity is calculated through transient CFD simulation, the movement displacement and the speed of a structural interface in a peripheral sub-channel of the assembly are given, the flow elasticity is calculated by adopting a moving grid technology and is converted into three fluid-solid coupling effects of additional rigidity, additional damping and additional mass; and determining the fluid-solid coupling effect through transient CFD simulation calculation, and verifying through the experimental results of the vibration characteristics of the rod bundle measured in air, still water and moving water.
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| CN115659875B (en) * | 2022-12-26 | 2023-10-17 | 成都航空职业技术学院 | Rod bundle fuel assembly test device and test parameter acquisition method thereof |
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