Direct current steam generator modeling method, device and equipment based on successive iteration method

Abstract

The application discloses a direct-current steam generator modeling method and device based on a successive iteration method, and relates to the technical field of power plant thermal hydraulic simulation, and the method comprises the following steps: obtaining the primary side working medium properties of the direct-current steam generator, ignoring the influence of pressure drop on the primary side working medium properties, and establishing the primary and secondary side field equations of the direct-current steam generator; performing discrete processing on the primary and secondary side field equations, setting the geometric parameters of the direct-current steam generator and the number of control body divisions, and performing geometric calculation processing; setting boundary conditions, performing steady-state calculation to obtain initial values, setting convergence conditions and transient working conditions, and performing transient calculation based on a successive iteration solving mode. The application has strong universality.

Description

Technical Field

[0001] This application relates to the field of thermal-hydraulic simulation technology for power plants, specifically to a modeling method, apparatus, and equipment for DC steam generators based on a successive iteration method. Background Technology

[0002] Steam generators are one of the important pieces of equipment in power plants. Due to their small size and high heat exchange efficiency, direct-current steam generators are widely used in high-temperature gas-cooled reactors, lead-bismuth fast reactors, and modular small and medium-sized power plants.

[0003] Existing simulation models of DC steam generators developed independently mostly adopt homogeneous flow models for the secondary side, while drift flow and split-phase flow models are less common. For different primary side working fluids (such as high-pressure water and liquid metal), researchers have developed corresponding DC steam generator simulation models, but these models are not very universal and are difficult to replace each other.

[0004] The mathematical models of commercial steam generators are typically solved using large coefficient matrices. This approach places high demands on the solver, is a core component of commercial software, and offers limited autonomy. This solution method is difficult to implement, lacks flexibility, and subsequent modifications to the packaged steam generator model are costly. Furthermore, when loosely coupled with other modules, it fails to fully leverage the time advantage of coefficient matrix solving. With the continuous development of power plants, developing a more universal transient simulation model for DC steam generators is a pressing issue that needs to be addressed. Summary of the Invention

[0005] This application provides a modeling method, apparatus, and equipment for DC steam generators based on the successive iteration method, which has strong versatility.

[0006] In a first aspect, embodiments of this application provide a DC steam generator modeling method based on a successive iteration method, the DC steam generator modeling method based on a successive iteration method comprising:

[0007] The primary working fluid properties of the DC steam generator are obtained, and the influence of pressure drop on the primary working fluid properties is ignored. The primary and secondary side field equations of the DC steam generator are established.

[0008] Discretize the first and second quadratic side field equations, set the geometric parameters of the DC steam generator and the number of control volume divisions, and perform geometric calculations.

[0009] Boundary conditions are set, steady-state calculations are performed to obtain initial values, and convergence conditions and transient conditions are set. Transient calculations are performed based on a successive iterative solution method.

[0010] In conjunction with the first aspect, in one implementation, the setting of convergence conditions and transient operating conditions, and the transient calculation based on a successive iterative solution method, specifically includes:

[0011] The temperature of each control element on the primary side is set at a set time, and the heat transfer power of each control element on the primary side is calculated based on the primary side energy equation.

[0012] Set the secondary side pressure drop at a set time, calculate the secondary side feedwater inlet pressure, and transfer the secondary side boundary conditions to the secondary side inlet.

[0013] Starting from the secondary side inlet, the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time are calculated.

[0014] The pressure drop on the secondary side at a set time is obtained based on the difference between the secondary side outlet pressure and the secondary side feedwater inlet pressure.

[0015] Based on the obtained secondary side pressure drop at the set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the heat transfer coefficient and the tube wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation.

[0016] Based on the heat exchange power of each control body at the updated set time, the temperature of each control body on the primary side at the set time is calculated using the primary side energy equation.

[0017] Determine whether the maximum temperature deviation between the calculated temperature of each control body on the primary side at the set time and the set temperature of each control body on the primary side at the set time is less than the set temperature deviation:

[0018] If not, the relaxation iteration method is used to update the temperature of each control body on the primary side at the set time, and then the temperature of each control body on the primary side at the set time is calculated again. This process is repeated until the maximum temperature deviation is less than the set temperature deviation.

[0019] If so, determine whether the simulation time has been reached:

[0020] -If the simulation time has not been reached, the time step of the set time is increased, and the temperature of each control body on the primary side at the set time is calculated again. The maximum temperature deviation is checked to see if it is less than the set temperature deviation and whether the simulation time has been reached, until the simulation time is reached.

[0021] - If the simulation time is reached, the simulation will end.

[0022] In conjunction with the first aspect, in one implementation method,

[0023] The calculation of the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time, starting from the secondary side inlet, specifically includes a first execution step and a second execution step.

[0024] The first execution step is as follows:

[0025] The density of the node at the set time of the single-phase region on the secondary side is set, and the mass conservation equation, momentum conservation equation and energy conservation equation on the secondary side are solved to obtain the velocity, pressure and enthalpy of the node at the set time of the single-phase region on the secondary side. The density of the node at the set time of the single-phase region on the secondary side is obtained again based on the pressure and enthalpy.

[0026] Determine whether the density deviation between the newly obtained density of the set node at the set time of the secondary side single-phase area and the density of the set node at the set time of the secondary side single-phase area is less than the set density deviation:

[0027] If not, the density of the set node at the set time of the secondary side single-phase area is updated using the Steffen iteration method, and then the density of the set node at the set time of the secondary side single-phase area is obtained again. This process is repeated until the density deviation is less than the set density deviation.

[0028] If so, determine whether the secondary side outlet has been calculated:

[0029] - If the secondary side outlet has not been calculated, the set node will be updated to the next node after the current set node. Then, the density of the set node at the set time of the secondary side single-phase area will be obtained again to determine whether the density deviation is less than the set density deviation and whether the secondary side outlet has been calculated. This process will be repeated until the secondary side outlet is calculated.

[0030] - The calculation ends when the secondary outlet is reached.

[0031] In conjunction with the first aspect, in one implementation method, the second execution step specifically includes:

[0032] The pressure and cavitation ratio at the set time and node of the secondary two-phase region are set, and the mass conservation equation, momentum conservation equation, energy conservation equation, and gas phase mass conservation equation of the secondary mixture are solved to obtain the pressure and cavitation ratio at the set time and node of the secondary two-phase region.

[0033] Determine whether the pressure deviation between the newly obtained pressure at the set node of the secondary two-phase region at the set time is less than the set pressure deviation, and whether the cavitation fraction deviation between the newly obtained cavitation fraction at the set node of the secondary two-phase region at the set time is less than the set cavitation fraction deviation.

[0034] If not all are true, then the pressure and cavitation fraction of the set node at the set time of the secondary two-phase region are updated using the quasi-Newton method. Then the pressure and cavitation fraction of the set node at the set time of the secondary two-phase region are obtained again. This cycle continues until the pressure deviation is less than the set pressure deviation and the cavitation fraction deviation is less than the set cavitation fraction deviation.

[0035] If all are yes, then determine whether the calculation has been performed up to the secondary side outlet:

[0036] - If the calculation has not reached the secondary side outlet, the set node will be updated to the next node after the current set node. Then, the pressure and cavitation fraction of the set node at the set time of the secondary side two-phase zone will be obtained again. The pressure deviation will be judged as less than the set pressure deviation, the cavitation fraction deviation as less than the set cavitation fraction deviation, and whether the calculation has reached the secondary side outlet. This process will be repeated until the calculation reaches the secondary side outlet.

[0037] - The calculation ends when the secondary outlet is reached.

[0038] In conjunction with the first aspect, in one implementation, based on the obtained secondary side pressure drop at a set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the flow heat transfer coefficient and the tube wall thermal conductivity are calculated based on the calculated temperature, pressure, and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through coupling equations, specifically as follows:

[0039] Determine whether the secondary voltage drop at the set time is less than the set voltage drop value:

[0040] If not, the Steffen iteration method is used to update the set secondary voltage drop at the set time, and then the set secondary voltage drop at the set time is obtained again. This process is repeated until the obtained set secondary voltage drop at the set time is less than the set voltage drop value.

[0041] If so, the heat transfer coefficient and pipe wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation.

[0042] In conjunction with the first aspect, in one implementation method,

[0043] The primary and secondary side field equations include the primary side energy equation, the secondary side homogeneous flow field equation in the single-phase region, the secondary side drift flow field equation in the two-phase region, and the coupling equation.

[0044] The primary working fluid properties include high-pressure water, lead, lead-bismuth, and sodium.

[0045] In conjunction with the first aspect, in one implementation method,

[0046] The geometric parameters include the number of heat transfer tubes, the inner diameter of the heat transfer tubes, the outer diameter of the heat transfer tubes, the height of the steam generator, and the diameter of the steam generator.

[0047] The geometric calculations include the calculation of hydraulic equivalent diameter, heat exchange equivalent diameter, primary side flow area, secondary side flow area, equivalent length of primary side of control body, equivalent length of secondary side of control body, and heat exchange area of ​​control body.

[0048] The boundary conditions include primary side inlet temperature, primary side mass flow rate, secondary side inlet temperature, secondary side feedwater mass flow rate, and secondary side steam pressure.

[0049] In conjunction with the first aspect, in one embodiment, the DC steam generator is arranged vertically or horizontally, and the heat transfer tubes of the DC steam generator are spiral tubes or straight tubes, with the secondary side outlet gas in a superheated state.

[0050] Secondly, embodiments of this application provide a DC steam generator modeling device based on a successive iteration method, the device comprising:

[0051] A module is established to obtain the primary-side working fluid properties of the DC steam generator, and the influence of pressure drop on the primary-side working fluid properties is ignored. The primary and secondary side field equations of the DC steam generator are then established.

[0052] The calculation module is used to discretize the first and second quadratic side field equations, set the geometric parameters of the DC steam generator and the number of control volume divisions, and perform geometric calculations.

[0053] The execution module is used to set boundary conditions, perform steady-state calculations to obtain initial values, and set convergence conditions and transient conditions, and perform transient calculations based on a successive iterative solution method.

[0054] Thirdly, embodiments of this application provide a DC steam generator modeling device based on a successive iteration method. The DC steam generator modeling device based on a successive iteration method includes a processor, a memory, and a DC steam generator modeling program based on a successive iteration method stored in the memory and executable by the processor. When the DC steam generator modeling program based on a successive iteration method is executed by the processor, it implements the steps of the DC steam generator modeling method based on a successive iteration method described above.

[0055] The beneficial effects of the technical solutions provided in this application include:

[0056] (1) Compared with the traditional DC steam generator model which is only applicable to one of the primary working medium being water or liquid metal, the DC steam generator model established in this application is applicable to both high-pressure water and liquid metal as the primary working medium, and has strong versatility. Furthermore, the distributed parameter model with fixed boundary and the drift flow model adopted in this application can simulate the characteristics of the primary and secondary sides of the DC steam generator more precisely, and can realize the coupled calculation of the primary and secondary sides.

[0057] (2) The solution process of the conservation equations all adopts the iterative method, and the iterative process is transformed into the solution of nonlinear equations or nonlinear equation systems. The Steffen iteration method is used in the single-phase region of the secondary side, and the quasi-Newton method is used in the two-phase region of the secondary side. No special solver is required, which greatly reduces the difficulty of solving the mathematical model of the steam generator and makes it easy to program.

[0058] (3) When coupling the primary and secondary sides, considering the characteristic that the temperature of the primary side changes approximately linearly along the axial direction, the temperature of each control body on the primary side is used as the iteration variable; and the power of each control body is used as the intermediate variable to calculate the secondary side and back-calculate the primary side. This enables the calculation of heat transfer and resistance empirical relationships when solving the conservation equations without performing the calculation of the heat transfer and resistance empirical relationships; the pressure drop of the secondary side is used instead of the inlet pressure as the iteration variable, and all boundary conditions are transformed to the secondary side inlet, thus effectively solving the problem that traditional iterative algorithms are not easy to converge.

[0059] (4) This application can replace the algorithm as needed, increase or decrease the heat exchange area, and after encapsulation, it can be coupled with other modules in each time step as an independent module, and follow the changes in boundary conditions, which has more flexible and universal characteristics. Attached Figure Description

[0060] Figure 1 This is a flowchart of a DC steam generator modeling method based on the successive iteration method proposed in this application;

[0061] Figure 2 This is a schematic diagram of the control volume division;

[0062] Figure 3 This is a flowchart illustrating the transient calculation based on a successive iterative solution method.

[0063] Figure 4 This is a schematic diagram of the DC steam generator modeling device based on the successive iteration method of this application.

[0064] Figure 5 This is a schematic diagram of the hardware structure of the DC steam generator modeling device based on the successive iteration method in this application. Detailed Implementation

[0065] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0066] To make the objectives, technical solutions, and advantages of this application clearer, the embodiments of this application will be described in further detail below with reference to the accompanying drawings.

[0067] Firstly, this application provides a modeling method for DC steam generators based on successive iterations. The established model is highly versatile and applicable to DC steam generators with high-pressure water and liquid metal on the primary side. It can accurately simulate the characteristics of the primary and secondary sides of the DC steam generator and can realize coupled calculations of the primary and secondary sides. Moreover, the solution process of the conservation equations all adopts the iterative method, which does not require a dedicated solver, greatly reducing the difficulty of solving the mathematical model of the steam generator and making it easy to program. At the same time, this application improves the iterative algorithm, solves the problem that traditional iterative algorithms are not easy to converge, and has the characteristics of being more flexible and versatile.

[0068] In one embodiment, reference is made to Figure 1 , Figure 1 This is a flowchart illustrating the DC steam generator modeling method based on the successive iteration method proposed in this application. Figure 1 As shown, the DC steam generator modeling method based on the successive iteration method includes:

[0069] S1: Obtain the primary side working fluid properties of the DC steam generator, and ignore the influence of pressure drop on the primary side working fluid properties to establish the primary and secondary side field equations of the DC steam generator;

[0070] It should be noted that in this application, the physical properties of the primary working fluid include high-pressure water, lead, lead-bismuth, and sodium, and the pressure drop on the primary side has little effect on the physical properties of the primary working fluid. The primary and secondary side field equations include the primary side energy equation, the homogeneous flow field equation in the single-phase region of the secondary side, the drift flow field equation in the two-phase region of the secondary side, and the coupling equation.

[0071] In this application, the DC steam generator is arranged vertically or horizontally, and the heat transfer tubes of the DC steam generator are spiral tubes or straight tubes, and the gas at the secondary side outlet is in a superheated state.

[0072] S2: Discretize the first and second quadratic side field equations, set the geometric parameters of the DC steam generator and the number of control volume divisions, and perform geometric calculations.

[0073] Specifically, the first-order side energy equation is discretized at the node center using a fully implicit finite difference method, while the second-order side field equation is discretized using a fully implicit, first-order upwind scheme, staggered grid, and finite difference method.

[0074] It should be noted that the geometric parameters include the number of heat transfer tubes, the inner diameter of the heat transfer tubes, the outer diameter of the heat transfer tubes, the height of the steam generator, and the diameter of the steam generator; and when the heat transfer tubes are spiral tubes, the geometric parameters also include the spiral tube coil diameter and the spiral tube pitch.

[0075] Geometric calculations include the calculation of hydraulic equivalent diameter, heat transfer equivalent diameter, primary side flow area, secondary side flow area, equivalent length of primary side of control volume, equivalent length of secondary side of control volume, and heat transfer area of ​​control volume.

[0076] When dividing the control volumes, there is one control volume at each end of the primary and secondary sides, used to represent the primary and secondary side inlets and outlets. These control volumes do not participate in heat exchange and hydraulic calculations. A schematic diagram of the control volume division is shown below. Figure 2 As shown.

[0077] S3: Set boundary conditions, perform steady-state calculations to obtain initial values, and set convergence conditions and transient conditions. Perform transient calculations based on successive iterative solution methods.

[0078] It should be noted that the boundary conditions include primary side inlet temperature, primary side mass flow rate, secondary side inlet temperature, secondary side feedwater mass flow rate, and secondary side steam pressure. To simulate the transient process of a DC steam generator, a resistance element with an adjustable resistance coefficient is installed at the secondary side outlet.

[0079] Furthermore, in one embodiment, convergence conditions and transient operating conditions are set, and transient calculations are performed based on a successive iterative solution method, specifically as follows:

[0080] S301: Set the temperature of each control body on the primary side at a set time, and calculate the heat exchange power of each control body on the primary side according to the primary side energy equation;

[0081] S302: Set the secondary side pressure drop at a set time, calculate the secondary side feedwater inlet pressure, and convert the secondary side boundary conditions to the secondary side inlet.

[0082] S303: Starting from the secondary side inlet, calculate the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time.

[0083] S304: The secondary side pressure drop at a set time is obtained based on the difference between the secondary side outlet pressure and the secondary side feedwater inlet pressure;

[0084] S305: Based on the obtained secondary side pressure drop at the set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the heat transfer coefficient and the tube wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation.

[0085] S306: Based on the heat exchange power of each control body at the updated set time, the temperature of each control body on the primary side at the set time is calculated using the primary side energy equation;

[0086] S307: Determine whether the maximum temperature deviation between the calculated temperature of each control body on the primary side at the set time and the set temperature of each control body on the primary side at the set time is less than the set temperature deviation.

[0087] If not, the relaxation iteration method is used to update the temperature of each control body on the primary side at the set time, and then the temperature of each control body on the primary side at the set time is calculated again. This process is repeated until the maximum temperature deviation is less than the set temperature deviation.

[0088] If so, determine whether the simulation time has been reached:

[0089] -If the simulation time has not been reached, the time step of the set time is increased, and the temperature of each control body on the primary side at the set time is calculated again. The maximum temperature deviation is checked to see if it is less than the set temperature deviation and whether the simulation time has been reached, until the simulation time is reached.

[0090] - If the simulation time is reached, the simulation will end.

[0091] Furthermore, in one embodiment, starting from the secondary side inlet, the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time are calculated, specifically including a first execution step and a second execution step.

[0092] Specifically, the first execution step is as follows:

[0093] S3031: Set the density of the node at the set time of the secondary side single-phase region, solve the secondary side mass conservation equation, momentum conservation equation and energy conservation equation, obtain the velocity, pressure and enthalpy of the node at the set time of the secondary side single-phase region, and obtain the density of the node at the set time of the secondary side single-phase region based on the pressure and enthalpy.

[0094] S3032: Determine whether the density deviation between the newly obtained density of the set node at the set time of the secondary side single-phase area and the density of the set node at the set time of the secondary side single-phase area is less than the set density deviation.

[0095] If not, the density of the set node at the set time of the secondary side single-phase area is updated using the Steffen iteration method, and then the density of the set node at the set time of the secondary side single-phase area is obtained again. This process is repeated until the density deviation is less than the set density deviation.

[0096] If so, determine whether the secondary side outlet has been calculated:

[0097] - If the secondary side outlet has not been calculated, the set node will be updated to the next node after the current set node. Then, the density of the set node at the set time of the secondary side single-phase area will be obtained again to determine whether the density deviation is less than the set density deviation and whether the secondary side outlet has been calculated. This process will be repeated until the secondary side outlet is calculated.

[0098] - The calculation ends when the secondary outlet is reached.

[0099] Specifically, the second execution step is as follows:

[0100] S3038: Set the pressure and cavitation ratio at the set time and node of the secondary two-phase region, solve the mass conservation equation, momentum conservation equation, energy conservation equation, and gas phase mass conservation equation of the secondary mixture, and obtain the pressure and cavitation ratio at the set time and node of the secondary two-phase region again.

[0101] S3039: Determine whether the pressure deviation between the re-acquired pressure at the set node of the secondary two-phase region at the set time is less than the set pressure deviation, and whether the cavitation fraction deviation between the re-acquired cavitation fraction at the set node of the secondary two-phase region at the set time is less than the set cavitation fraction deviation.

[0102] If not all are true, then the pressure and cavitation fraction of the set node at the set time of the secondary two-phase region are updated using the quasi-Newton method. Then the pressure and cavitation fraction of the set node at the set time of the secondary two-phase region are obtained again. This cycle continues until the pressure deviation is less than the set pressure deviation and the cavitation fraction deviation is less than the set cavitation fraction deviation.

[0103] If all are yes, then determine whether the calculation has been performed up to the secondary side outlet:

[0104] - If the calculation has not reached the secondary side outlet, the set node will be updated to the next node after the current set node. Then, the pressure and cavitation fraction of the set node at the set time of the secondary side two-phase zone will be obtained again. The pressure deviation will be judged as less than the set pressure deviation, the cavitation fraction deviation as less than the set cavitation fraction deviation, and whether the calculation has reached the secondary side outlet. This process will be repeated until the calculation reaches the secondary side outlet.

[0105] - The calculation ends when the secondary outlet is reached.

[0106] Furthermore, in one embodiment, based on the obtained secondary side pressure drop at a set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the heat transfer coefficient and the tube wall thermal conductivity are calculated based on the calculated temperature, pressure, and velocity of each control body on the secondary side at the set time. The heat transfer power of each control body at the set time is then updated through a coupling equation, specifically:

[0107] Determine whether the secondary voltage drop at the set time is less than the set voltage drop value:

[0108] If not, the Steffen iteration method is used to update the set secondary voltage drop at the set time, and then the set secondary voltage drop at the set time is obtained again. This process is repeated until the obtained set secondary voltage drop at the set time is less than the set voltage drop value.

[0109] If so, the heat transfer coefficient and pipe wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation.

[0110] The following combination Figure 3 This paper describes in detail the process of setting convergence conditions and transient conditions in this application, and performing transient calculations based on a successive iterative solution method.

[0111] A: Set the temperature of each control body on the primary side at time j+1, calculate the heat transfer power of each control body on the primary side according to the primary side energy equation, and then proceed to B;

[0112] B: Set the secondary side pressure drop at time j+1, calculate the secondary side feedwater inlet pressure, and convert the secondary side boundary conditions to the secondary side inlet. For single-phase regions, switch to C; for two-phase regions, switch to D.

[0113] C: Set the density of node i+1 at time j+1 in the secondary side single-phase region, then go to E;

[0114] E: Solve the mass conservation equation, momentum conservation equation, and energy conservation equation for the secondary side. Based on the obtained pressure and enthalpy values, re-obtain the density of node i+1 at time j+1 in the single-phase region of the secondary side, and then proceed to F.

[0115] F: Determine whether the density deviation between the re-acquired density of node i+1 at time j+1 in the secondary side single-phase region and the set density of node i+1 at time j+1 in the secondary side single-phase region is less than the set density deviation. If not, go to G; if yes, go to K.

[0116] G: Update the density of node i+1 at time j+1 in the set secondary side single-phase region using the Steffen iteration method, and go to C;

[0117] D: Set the pressure and cavitation fraction of node i+1 at time j+1 in the secondary two-phase region, then switch to H;

[0118] H: Solve the mass conservation equation, momentum conservation equation, energy conservation equation, and gas phase mass conservation equation for the secondary side mixture to obtain the pressure and cavitation fraction at node i+1 at time j+1 in the secondary side two-phase region, and then proceed to I;

[0119] I: Determine whether the pressure deviation between the pressure of the newly obtained secondary two-phase zone setting node at the set time and the pressure of the set secondary two-phase zone setting node at the set time is less than the set pressure deviation, and whether the cavitation fraction deviation between the newly obtained secondary two-phase zone setting node at the set time and the cavitation fraction of the set secondary two-phase zone setting node at the set time is less than the set cavitation fraction deviation. If both are yes, proceed to J; if both are yes, proceed to K.

[0120] J: Update the pressure and cavitation fraction of node i+1 at time j+1 in the secondary two-phase region using the quasi-Newton method, and then proceed to D;

[0121] K: Determine if the secondary outlet has been calculated. If not, proceed to L; if yes, proceed to M.

[0122] L: Update i to i+1, then proceed to C and D accordingly;

[0123] M: Based on the difference between the secondary side outlet pressure and the secondary side feedwater inlet pressure, obtain the secondary side pressure drop at time j+1, then proceed to N;

[0124] N: Determine whether the secondary side pressure drop at time j+1 is less than the set pressure drop value. If not, go to O; if yes, go to P.

[0125] O: Update the set secondary side pressure drop at time j+1 using the Steffen iterative method, then proceed to B;

[0126] P: Based on the calculated temperature, pressure and velocity of each control body on the secondary side at time j+1, the heat transfer coefficient and the thermal conductivity of the pipe wall are calculated, and the heat transfer power of each control body at time j+1 is updated through the coupling equation, and then transferred to Q;

[0127] Q: Based on the updated heat transfer power of each control body at time j+1, calculate the temperature of each primary control body at time j+1 using the primary side energy equation, and then transfer to R;

[0128] R: Determine whether the maximum temperature deviation between the calculated temperature of each control body on the primary side at time j+1 and the set temperature of each control body on the primary side at time j+1 is less than the set temperature deviation. If not, go to S; if yes, go to T.

[0129] S: Update the set temperature of each control body at time j+1 using the relaxation iteration method, then switch to A;

[0130] T: Determine if the simulation time has been reached. If not, proceed to U; if yes, proceed to V.

[0131] U: Increase the time step at time j+1, that is, update j to j+1 and go to A;

[0132] V: End.

[0133] It should be further noted that the heat exchange regions of the DC steam generator in this application include the subcooled region, the saturated boiling region, the film boiling region, and the superheated region, and different heat transfer models and resistance models are selected for different heat exchange regions.

[0134] Secondly, embodiments of this application also provide a DC steam generator modeling device based on a successive iteration method.

[0135] In one embodiment, reference is made to Figure 4 , Figure 4 This is a schematic diagram of the functional modules of the DC steam generator modeling device based on the successive iterative method of this application. Figure 4 As shown, the DC steam generator modeling device based on the successive iteration method includes a modeling module, a calculation module, and an execution module.

[0136] The module establishes the primary-side working fluid properties of the DC steam generator, ignoring the influence of pressure drop on these properties, and establishes the primary and secondary side-field equations of the DC steam generator. The calculation module discretizes the primary and secondary side-field equations, sets the geometric parameters and the number of control volume divisions of the DC steam generator, and performs geometric calculations. The execution module sets boundary conditions, performs steady-state calculations to obtain initial values, sets convergence conditions and transient operating conditions, and performs transient calculations based on a successive iterative solution method.

[0137] Thirdly, this application provides a DC steam generator modeling device based on the successive iteration method. The DC steam generator modeling device based on the successive iteration method can be a personal computer (PC), laptop computer, server, or other device with data processing capabilities.

[0138] Reference Figure 5 , Figure 5 This is a schematic diagram of the hardware structure of a DC steam generator modeling device based on the successive iteration method involved in the embodiments of this application. In the embodiments of this application, the DC steam generator modeling device based on the successive iteration method may include a processor, a memory, a communication interface, and a communication bus.

[0139] The communication bus can be of any type and is used to interconnect the processor, memory, and communication interface.

[0140] The communication interface includes input / output (I / O) interfaces, physical interfaces, and logical interfaces. These interfaces enable interconnection of devices within the DC steam generator modeling equipment based on the successive iteration method, and also enable interconnection between the DC steam generator modeling equipment and other devices (such as other computing devices or user equipment). Physical interfaces can be Ethernet interfaces, fiber optic interfaces, ATM interfaces, etc.; user equipment can be displays, keyboards, etc.

[0141] Memory can be various types of storage media, such as random access memory (RAM), read-only memory (ROM), non-volatile RAM (NVRAM), flash memory, optical storage, hard disk, programmable ROM (PROM), erasable PROM (EPROM), electrically erasable PROM (EEPROM), etc.

[0142] The processor can be a general-purpose processor, which can call a DC steam generator modeling program based on the successive iteration method stored in memory and execute the DC steam generator modeling method based on the successive iteration method provided in the embodiments of this application. For example, the general-purpose processor can be a central processing unit (CPU). The method executed when the DC steam generator modeling program based on the successive iteration method is called can refer to the various embodiments of the DC steam generator modeling method based on the successive iteration method of this application, and will not be repeated here.

[0143] Those skilled in the art will understand that Figure 5 The hardware structure shown does not constitute a limitation of this application and may include more or fewer components than shown, or combine certain components, or have different component arrangements.

[0144] The terms "comprising" and "having," and any variations thereof, in the specification, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus. The terms "first," "second," and "third," etc., are used to distinguish different objects, etc., and do not indicate a sequence, nor do they limit "first," "second," and "third" to different types.

[0145] In the description of the embodiments of this application, terms such as "exemplary," "for example," or "for instance" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as "exemplary," "for example," or "for instance" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary," "for example," or "for instance" is intended to present the relevant concepts in a concrete manner.

[0146] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more.

[0147] In some processes described in the embodiments of this application, multiple operations or steps are included in a specific order. However, it should be understood that these operations or steps may not be executed in the order they appear in the embodiments of this application, or they may be executed in parallel. The sequence number of the operation is only used to distinguish different operations, and the sequence number itself does not represent any execution order. In addition, these processes may include more or fewer operations, and these operations or steps may be executed sequentially or in parallel, and these operations or steps may be combined.

[0148] Through the above description of the embodiments, those skilled in the art can clearly understand that the methods of the above embodiments can be implemented by means of software plus necessary general-purpose hardware platforms. Of course, they can also be implemented by hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product is stored in a storage medium (such as ROM / RAM, magnetic disk, optical disk) as described above, and includes several instructions to cause a terminal device to execute the methods described in the various embodiments of this application.

[0149] The above are merely preferred embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A method for modeling a DC steam generator based on a successive iteration method, characterized in that, The DC steam generator modeling method based on successive iterations includes: The primary working fluid properties of the DC steam generator are obtained, and the influence of pressure drop on the primary working fluid properties is ignored. The primary and secondary side field equations of the DC steam generator are established. Discretize the first and second quadratic side field equations, set the geometric parameters of the DC steam generator and the number of control volume divisions, and perform geometric calculations. Set boundary conditions, perform steady-state calculations to obtain initial values, and set convergence conditions and transient conditions. Perform transient calculations based on a successive iterative solution method. Specifically, the setting of convergence conditions and transient conditions is based on a successive iterative solution method for transient calculation, as follows: The temperature of each control element on the primary side is set at a set time, and the heat transfer power of each control element on the primary side is calculated based on the primary side energy equation. Set the secondary side pressure drop at a set time, calculate the secondary side feedwater inlet pressure, and transfer the secondary side boundary conditions to the secondary side inlet. Starting from the secondary side inlet, the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time are calculated. The pressure drop on the secondary side at a set time is obtained based on the difference between the secondary side outlet pressure and the secondary side feedwater inlet pressure. Based on the obtained secondary side pressure drop at the set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the heat transfer coefficient and the tube wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation. Based on the heat exchange power of each control body at the updated set time, the temperature of each control body on the primary side at the set time is calculated using the primary side energy equation. Determine whether the maximum temperature deviation between the calculated temperature of each control body on the primary side at the set time and the set temperature of each control body on the primary side at the set time is less than the set temperature deviation: If not, the relaxation iteration method is used to update the temperature of each control body on the primary side at the set time, and then the temperature of each control body on the primary side at the set time is calculated again. This process is repeated until the maximum temperature deviation is less than the set temperature deviation. If so, determine whether the simulation time has been reached: -If the simulation time has not been reached, the time step of the set time is increased, and the temperature of each control body on the primary side at the set time is calculated again. The maximum temperature deviation is checked to see if it is less than the set temperature deviation and whether the simulation time has been reached, until the simulation time is reached. - If the simulation time is reached, the simulation will end.

2. The DC steam generator modeling method based on successive iterations as described in claim 1, characterized in that: The calculation of the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time, starting from the secondary side inlet, specifically includes a first execution step and a second execution step. The first execution step is as follows: The density of the node at the set time of the single-phase region on the secondary side is set, and the mass conservation equation, momentum conservation equation and energy conservation equation on the secondary side are solved to obtain the velocity, pressure and enthalpy of the node at the set time of the single-phase region on the secondary side. The density of the node at the set time of the single-phase region on the secondary side is obtained again based on the pressure and enthalpy. Determine whether the density deviation between the newly obtained density of the set node at the set time of the secondary side single-phase area and the density of the set node at the set time of the secondary side single-phase area is less than the set density deviation: If not, the density of the set node at the set time of the secondary side single-phase area is updated using the Steffen iteration method, and then the density of the set node at the set time of the secondary side single-phase area is obtained again. This process is repeated until the density deviation is less than the set density deviation. If so, determine whether the secondary side outlet has been calculated: - If the secondary side outlet has not been calculated, the set node will be updated to the next node after the current set node. Then, the density of the set node at the set time of the secondary side single-phase area will be obtained again to determine whether the density deviation is less than the set density deviation and whether the secondary side outlet has been calculated. This process will be repeated until the secondary side outlet is calculated. - The calculation ends when the secondary outlet is reached.

3. The DC steam generator modeling method based on successive iterations as described in claim 2, characterized in that, The second execution step is as follows: The pressure and cavitation ratio at the set time and node of the secondary two-phase region are set, and the mass conservation equation, momentum conservation equation, energy conservation equation, and gas phase mass conservation equation of the secondary mixture are solved to obtain the pressure and cavitation ratio at the set time and node of the secondary two-phase region. Determine whether the pressure deviation between the newly obtained pressure at the set node of the secondary two-phase region at the set time is less than the set pressure deviation, and whether the cavitation fraction deviation between the newly obtained cavitation fraction at the set node of the secondary two-phase region at the set time is less than the set cavitation fraction deviation. If not all are true, then the pressure and cavitation fraction of the set node at the set time of the secondary two-phase region are updated using the quasi-Newton method. Then the pressure and cavitation fraction of the set node at the set time of the secondary two-phase region are obtained again. This cycle continues until the pressure deviation is less than the set pressure deviation and the cavitation fraction deviation is less than the set cavitation fraction deviation. If all are yes, then determine whether the calculation has been performed up to the secondary side outlet: - If the calculation has not reached the secondary side outlet, the set node will be updated to the next node after the current set node. Then, the pressure and cavitation fraction of the set node at the set time of the secondary side two-phase zone will be obtained again. The pressure deviation will be judged as less than the set pressure deviation, the cavitation fraction deviation as less than the set cavitation fraction deviation, and whether the calculation has reached the secondary side outlet. This process will be repeated until the calculation reaches the secondary side outlet. - The calculation ends when the secondary outlet is reached.

4. The DC steam generator modeling method based on successive iterations as described in claim 1, characterized in that, Based on the obtained secondary side pressure drop at a set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the flow heat transfer coefficient and pipe wall thermal conductivity are calculated based on the calculated temperature, pressure, and velocity of each control body on the secondary side at the set time. The heat transfer power of each control body at the set time is then updated through coupling equations. Specifically: Determine whether the secondary voltage drop at the set time is less than the set voltage drop value: If not, the Steffen iteration method is used to update the set secondary voltage drop at the set time, and then the set secondary voltage drop at the set time is obtained again. This process is repeated until the obtained set secondary voltage drop at the set time is less than the set voltage drop value. If so, the heat transfer coefficient and pipe wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation.

5. The DC steam generator modeling method based on successive iterations as described in claim 1, characterized in that: The primary and secondary side field equations include the primary side energy equation, the secondary side homogeneous flow field equation in the single-phase region, the secondary side drift flow field equation in the two-phase region, and the coupling equation. The primary working fluid properties include high-pressure water, lead, lead-bismuth, and sodium.

6. The DC steam generator modeling method based on successive iterations as described in claim 1, characterized in that: The geometric parameters include the number of heat transfer tubes, the inner diameter of the heat transfer tubes, the outer diameter of the heat transfer tubes, the height of the steam generator, and the diameter of the steam generator. The geometric calculations include the calculation of hydraulic equivalent diameter, heat exchange equivalent diameter, primary side flow area, secondary side flow area, equivalent length of primary side of control body, equivalent length of secondary side of control body, and heat exchange area of ​​control body. The boundary conditions include primary side inlet temperature, primary side mass flow rate, secondary side inlet temperature, secondary side feedwater mass flow rate, and secondary side steam pressure.

7. The DC steam generator modeling method based on successive iterations as described in claim 1, characterized in that: The DC steam generator is arranged vertically or horizontally, and the heat transfer tubes of the DC steam generator are spiral tubes or straight tubes, with the secondary side outlet gas in a superheated state.

8. A modeling device for a DC steam generator based on a successive iteration method, characterized in that, The device includes: A module is established to obtain the primary-side working fluid properties of the DC steam generator, and the influence of pressure drop on the primary-side working fluid properties is ignored. The primary and secondary side field equations of the DC steam generator are then established. The calculation module is used to discretize the first and second quadratic side field equations, set the geometric parameters of the DC steam generator and the number of control volume divisions, and perform geometric calculations. The execution module is used to set boundary conditions, perform steady-state calculations to obtain initial values, and set convergence conditions and transient conditions, and perform transient calculations based on a successive iterative solution method. Specifically, the setting of convergence conditions and transient conditions is based on a successive iterative solution method for transient calculation, as follows: The temperature of each control element on the primary side is set at a set time, and the heat transfer power of each control element on the primary side is calculated based on the primary side energy equation. Set the secondary side pressure drop at a set time, calculate the secondary side feedwater inlet pressure, and transfer the secondary side boundary conditions to the secondary side inlet. Starting from the secondary side inlet, the temperature, pressure, velocity, and cavitation fraction of each control body on the secondary side at a set time are calculated. The pressure drop on the secondary side at a set time is obtained based on the difference between the secondary side outlet pressure and the secondary side feedwater inlet pressure. Based on the obtained secondary side pressure drop at the set time, and when the secondary side pressure drop at the set time is less than the set pressure drop value, the heat transfer coefficient and the tube wall thermal conductivity are calculated based on the temperature, pressure and velocity of each control body on the secondary side at the set time, and the heat transfer power of each control body at the set time is updated through the coupling equation. Based on the heat exchange power of each control body at the updated set time, the temperature of each control body on the primary side at the set time is calculated using the primary side energy equation. Determine whether the maximum temperature deviation between the calculated temperature of each control body on the primary side at the set time and the set temperature of each control body on the primary side at the set time is less than the set temperature deviation: If not, the relaxation iteration method is used to update the temperature of each control body on the primary side at the set time, and then the temperature of each control body on the primary side at the set time is calculated again. This process is repeated until the maximum temperature deviation is less than the set temperature deviation. If so, determine whether the simulation time has been reached: -If the simulation time has not been reached, the time step of the set time is increased, and the temperature of each control body on the primary side at the set time is calculated again. The maximum temperature deviation is checked to see if it is less than the set temperature deviation and whether the simulation time has been reached, until the simulation time is reached. - If the simulation time is reached, the simulation will end.

9. A DC steam generator modeling device based on a successive iteration method, characterized in that, The DC steam generator modeling device based on the successive iteration method includes a processor, a memory, and a DC steam generator modeling program based on the successive iteration method stored in the memory and executable by the processor. When the DC steam generator modeling program based on the successive iteration method is executed by the processor, it implements the steps of the DC steam generator modeling method based on the successive iteration method as described in any one of claims 1 to 7.

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