Modeling Method of Gas-Supercritical CO2 Thermal Cycle Based on the Correlation between Steady State and Transient State

Abstract

The present invention relates to the technical field of gas - supercritical CO2 power generation peak shaving, and particularly to a modeling method for gas - supercritical CO2 thermal cycle based on the correlation between steady state and transient state. First, the gas - liquid - supercritical multiphase heterogeneous energy flow process is divided into the smallest units, and the convective - conductive coupled heat transfer process is quantitatively constructed and described. The supercritical process is corrected through the correlation formula of dimensionless parameters, the inertia order and time delay characteristics of each link in the cycle transient process are evaluated, the energy storage space characteristics and dynamic correlation mechanism of the four - fold time scale of the cycle components are explored, and the joint derivation of the steady - state process and transient - state process quantitative construction description models is carried out, and a steady - state and transient quantitative correlation modeling method for gas - supercritical CO2 thermal cycle is proposed. This method can be used for the simulation of the rapid load - change process of gas - supercritical CO2 thermal cycle under different working conditions, and reveal the transient process performance of the multiphase heterogeneous energy flow process under wide load.

Description

Technical Field

[0001] The present invention relates to the technical field of gas-supercritical CO2 power generation peak shaving, and particularly to a modeling method for gas-supercritical CO2 thermal cycle based on the correlation between steady state and transient state. Background Art

[0002] With the gradual increase in the grid connection scale of renewable energy sources such as wind power and photovoltaic power, the instability and intermittency characteristics of wind and photovoltaic power also enter the power grid. The power consumption power source must meet the requirements of flexibility and rapidity. However, the rapid load change ability of coal-fired units is limited, and there are bottlenecks in consuming intermittent and fluctuating renewable energy.

[0003] Gas turbines not only have the advantages of clean and efficient operation and rapid load change, but also can well suppress the minute-level intermittent power fluctuations of renewable energy through "gas-electricity peak shaving". The supercritical CO2 thermal cycle can match the load regulation requirements of intermittent fluctuations. Therefore, the gas-supercritical CO2 thermal cycle can effectively relieve the peak shaving pressure of coal-fired generating units in the power grid and quickly consume the electric energy of renewable energy. However, the cycle process has the characteristics of multiphase coupling, pseudo-critical non-linearity and intermittent fluctuations, which will make it difficult to coordinate and control the rapid load change process. Therefore, studying the coordinated operation mechanism of the rapid load change of the gas-supercritical CO2 thermal cycle is the mechanistic premise for maximizing its dual efficiency of efficient supply and rapid consumption in the environment of grid connection of intermittent renewable energy. Summary of the Invention

[0004] The object of the present invention is to solve the problems existing in the background art, and propose a modeling method for gas-supercritical CO2 thermal cycle based on the correlation between steady state and transient state, which solves the problem of difficult regulation of the non-linear behavior of the transient process of multiphase heterogeneous energy flow in the cycle.

[0005] The technical solution of the present invention, a modeling method for gas-supercritical CO2 thermal cycle based on the correlation between steady state and transient state, includes:

[0006] 1. Steady-state process modeling

[0007] Step 1: Divide the thermal cycle into three independent sub-modules according to the difference in heat flux density, namely the gas phase process, the liquid phase process and the supercritical process.

[0008] Step 2: Quantitatively describe the convective-conductive coupled heat transfer process in the thermal cycle with the comprehensive heat transfer coefficient.

[0009] Step 3: Then correct the supercritical process through the dimensionless correlation formula, and finally preliminarily construct a convective-conductive coupled heat transfer process model.

[0010] Step 4: Use the flow transport equation for verification and correction to establish a quantitative construction description model for the steady-state process of heterogeneous energy flow.

[0011] 2. Transient Process Modeling

[0012] Step 1: Taking the physical boundary of the device as the criterion, obtain the minimum unit for transient process modeling.

[0013] Step 2: Determine the interface specifications between unit models and reasonably connect each unit model of the gas - supercritical CO2 thermodynamic cycle.

[0014] Step 3: According to the size parameters and physical structure attributes of the unit equipment, preliminarily evaluate the inertia order and time - delay characteristics of each link in the cycle transient process, divide the time scales to which each process belongs, and determine the coupling and correlation mechanisms between models of different time scales.

[0015] Step 4: Construct a calculation model for the real - gas properties of carbon dioxide based on the GERG - 2008 equation of state, and use the dimensionless Helmholtz free - energy equation to accurately calculate the thermal properties of carbon dioxide in the pseudo - critical region. Adopt the time - varying thermodynamic equation and flow transport equation to jointly deduce the heat - taking - heat - transfer - flow process of the multi - phase heterogeneous energy flow in the carbon dioxide pseudo - critical region, and establish a quantitative description method for the coupled non - linear partial differential equation of its transient process.

[0016] 3. Correlation Model

[0017] Jointly deduce the quantitative description method of the coupled non - linear partial differential equation of the transient process and the quantitative construction description model of the steady - state process to obtain a cycle quantitative correlation model based on the steady - state and transient processes.

[0018] 4. Construct a Cycle Characteristic Condition Database Based on Simulation Data

[0019] Use the face - centered cubic design method to select the parameters to be optimized as independent variables. Under the condition of satisfying the constraints of variable - operating - condition conditions, conduct single - factor experiments on each independent variable to obtain the change range and characteristics of the independent variables during the variable - load process. Divide the results of the single - factor analysis into three levels: maximum value, minimum value, and the arithmetic mean of the two according to the requirements of the face - centered cubic design. Conduct simulation experiments according to different combination methods of the independent - variable levels of the face - centered cubic design to obtain the samples required for constructing the neural - network model. Construct a cycle characteristic condition database based on simulation data by training the time - series neural - network model of the cycle transient characteristics.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] According to the small-time-scale transient response law of the gas waste heat flow and the supercritical CO2 working medium flow, the large-time-scale transient response characteristics of the intermediate medium flow and the transcritical CO2 phase change process are explored, and then the dynamic correlation mechanism of the multiphase heterogeneous energy flow is clarified. The simulation speed of the cycle transient process is improved. Using the simulation results under different working conditions, a simulation data working condition library for the cycle transient process is constructed, and the data modeling method is used to correct the cycle quantitative correlation model, and the transient characteristics of the gas-liquid-supercritical multiphase heterogeneous energy flow coupling cycle process under wide load are explained. Finally, the coordinated control ability of the gas-supercritical CO2 thermal cycle rapid load change process is improved. Brief Description of the Drawings

[0022] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. Detailed Description of the Invention

[0023] Embodiment 1

[0024] As Figure 1 shown, the gas-supercritical CO2 thermal cycle is divided into a steady-state process and a transient process for modeling respectively.

[0025] In the steady-state process modeling, the thermal cycle is divided into independent sub-modules according to the difference in heat flux density. Using the energy balance equation, the inlet and outlet parameters of the gas-phase gas flow, the liquid-phase intermediate medium flow, and the supercritical CO2 working medium flow are obtained respectively. The convective-conductive coupled heat transfer process is quantitatively described by the comprehensive heat transfer coefficient, and the supercritical process is corrected by the dimensionless parameter correlation formula, and a convective-conductive coupled heat transfer process model is initially constructed. The flow transport equation is used for verification and correction to establish a quantitative construction description model for the heterogeneous energy flow steady-state process.

[0026] In the transient process modeling, it is divided according to the physical boundaries of the equipment to obtain the minimum unit for transient process modeling: gas turbine, heat exchanger, turbine, compressor and pump. According to the unit model interface specification, physical structure attributes and dimensional parameters, the inertia order and time delay characteristics of the unit link are determined. The coupling and correlation mechanism between the time scale models is established through the quantitative description of the nonlinear partial differential equation of the transient process in the pseudo-critical region of carbon dioxide.

[0027] The quantitative construction description model of the heterogeneous energy flow steady-state process in the steady-state process and the coupling and correlation mechanism between the time scale models in the transient process are jointly deduced to obtain a cycle quantitative correlation model based on the steady-state and transient processes.

[0028] In summary, the introduction of the gas-supercritical CO2 thermal cycle modeling method based on steady-state and transient correlation is completed.

[0029] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited thereto, and various changes can be made without departing from the spirit of the present invention within the scope of knowledge possessed by those skilled in the art.

Claims

1. A modeling method for a gas-supercritical CO2 power cycle based on the correlation between steady state and transient state, characterized in that, It includes the following specific steps: S1. Model the steady-state process; S11. Divide the thermodynamic cycle into three independent sub-modules according to the difference in heat flux density, namely the gas-phase process, the liquid-phase process, and the supercritical process; S12. Use the overall heat transfer coefficient to quantitatively describe the convective-conductive coupled heat transfer process in the thermodynamic cycle; S13. Modify the supercritical process through the dimensionless correlation formula to construct a convective-conductive coupled heat transfer process model; S14. Use the flow transport equation for verification and correction to establish a quantitative construction description model for the heterogeneous energy flow steady-state process; S2. Model the transient process; S21. Take the physical boundary of the equipment as the boundary to obtain the minimum unit for transient process modeling; S22. Determine the interface specification between unit models and connect each unit model of the gas-supercritical CO2 thermodynamic cycle; S23. Construct a calculation model for the real gas properties of carbon dioxide based on the GERG-2008 equation of state, and use the dimensionless Helmholtz free energy equation to accurately calculate the thermal properties of carbon dioxide in the pseudo-critical region; S24. Use the time-varying thermodynamic equation and the flow transport equation to jointly derive the heat extraction-heat transfer-flow process of the multi-phase heterogeneous energy flow in the carbon dioxide pseudo-critical region, and establish a quantitative description method for the coupled non-linear partial differential equation of its transient process; S3. Establish a correlation model; S31. Jointly derive the quantitative description method of the coupled non-linear partial differential equation of the transient process and the quantitative construction description model of the steady-state process to obtain a cycle quantitative correlation model based on the steady-state and transient processes.

2. The gas-supercritical CO2 thermodynamic cycle modeling method based on the correlation between steady state and transient state according to claim 1, wherein, In S11, the energy balance equation is used to obtain the inlet and outlet parameters of the gas-phase gas flow, the liquid-phase intermediate medium flow, and the supercritical CO2 working medium flow respectively.

3. The gas-supercritical CO2 thermodynamic cycle modeling method based on the correlation between steady state and transient state according to claim 1, wherein S2 also includes constructing a simulation data working condition library for the cycle transient process; using the data fusion modeling method to correct the cycle quantitative correlation model.

4. The gas-supercritical CO2 thermodynamic cycle modeling method based on the correlation between steady state and transient state according to claim 1, characterized in that, The minimum unit in S21 includes a gas turbine, a heat exchanger, a turbine, a compressor, and a pump.

5. The gas-supercritical CO2 thermodynamic cycle modeling method based on the correlation between steady state and transient state according to claim 1, characterized in that, In S21, according to the size parameters and physical structure attributes of each unit device, evaluate the inertia order and time delay characteristics of each link of the cycle transient process, divide the time scales to which each process belongs, and determine the coupling and correlation mechanism between models of different time scales.

6. The gas-supercritical CO2 thermal cycle modeling method based on the association between steady state and transient state according to claim 5, characterized in that Establish the coupling and correlation mechanism between models of different time scales through the quantitative description of the non-linear partial differential equation of the transient process in the carbon dioxide pseudo-critical region.

7. An electronic device, characterized in that, It includes a memory and a processor, and a program running on the processor is stored on the memory; When the processor runs the program, it executes the steps of the gas-supercritical CO2 thermodynamic cycle modeling method based on steady-state and transient correlation described in any one of claims 1-6.

8. A computer-readable storage medium having computer instructions stored thereon, characterized in that, When the computer instruction runs, it executes the steps of the gas-supercritical CO2 thermodynamic cycle modeling method based on steady-state and transient correlation described in any one of claims 1-6.

Images