A device for testing the thick-wall stress and temperature of an energy storage cylinder for compressed air

Abstract

The present invention relates to the technical field of stress and temperature testing devices, specifically: a stress and temperature testing device for the thick wall of a compressed air energy storage cylinder, including an air tank, a support frame, and a control system. The output of the air tank is connected to a first pipeline, and a second pipeline is arranged outside the support frame. A gas pressure pump is arranged between the first pipeline and the second pipeline. The input end of the gas pressure pump is fixedly connected to the first pipeline, and the output end of the gas pressure pump is fixedly connected to the second pipeline. One end of the second pipeline is fixedly connected to a sealing cover, and a plurality of connecting bolts are arranged through the sealing cover. A thick wall cylinder is arranged on the support frame, and a plurality of strain gauges and thermocouples are installed at the end of the thick wall cylinder. Stress and temperature are detected through the strain gauges and thermocouples. Through the setting of the control system, stress and inflation flow can be simultaneously monitored and controlled in a coordinated manner. Through the coordinated monitoring and control.

Description

Technical Field

[0001] The present invention relates to the technical field of stress and temperature testing devices, and in particular to a thick-wall stress and temperature testing device for a compressed air energy storage cylinder. Background Art

[0002] A thick-wall stress and temperature testing device for a compressed air energy storage cylinder is a key device for monitoring the performance of a compressed air energy storage cylinder. Structurally, it is equipped with a variety of high-precision sensors. Stress sensors are installed at various parts of the thick wall of the cylinder. Based on the principle of resistance strain, they can capture in real time the stress changes suffered by the thick wall of the cylinder during the charging and discharging of compressed air, and convert mechanical strain into an electrical signal for output. Temperature sensors use thermocouples or thermal resistors, etc., to accurately measure the temperature of the cylinder wall and the internal air. Functionally, by continuously monitoring stress and temperature, the safety and reliability of the cylinder under different working conditions can be evaluated.

[0003] In the prior art, however, the thick-wall stress and temperature testing device for the energy storage cylinder used cannot co-monitor and control stress and inflation flow rate, and the two are carried out separately. During the compressed air energy storage process, the thick wall of the cylinder will bear different degrees of stress due to the change of inflation pressure. If the stress exceeds the bearing limit of the material, it may cause serious consequences such as cracks, deformation, or even rupture of the cylinder. Summary of the Invention

[0004] Aiming at the technical problem that the thick-wall stress and temperature testing device for the energy storage cylinder used in the prior art cannot co-monitor and control stress and inflation flow rate, the present invention provides a thick-wall stress and temperature testing device for a compressed air energy storage cylinder.

[0005] The technical solution adopted by the present invention is: a thick-wall stress and temperature testing device for a compressed air energy storage cylinder, including an air tank, a support frame, and a control system. The output of the air tank is connected to a first pipeline, and a second pipeline is arranged outside the support frame. A gas pressure pump is arranged between the first pipeline and the second pipeline. The input end of the gas pressure pump is fixedly connected to the first pipeline, and the output end of the gas pressure pump is fixedly connected to the second pipeline. One end of the second pipeline is fixedly connected to a sealing cover, and a plurality of connecting bolts penetrate through the sealing cover. A thick-wall cylinder is arranged on the support frame, and a plurality of strain gauges and thermocouples are installed at the end of the thick-wall cylinder. The group of strain gauges and thermocouples are electrically coupled to the control system.

[0006] In one embodiment, a first valve is installed in the first pipeline, a second valve and a pressure gauge are installed in the second pipeline, and a pressure relief valve is also installed in the second pipeline.

[0007] In one embodiment, an annular frame is fixedly connected to the outside of the support frame, a plurality of groups of air bags are fixedly connected to the outside of the annular frame, a third pipe is fixedly connected to the outside of the second pipe, a third valve is fixedly connected in the third pipe, one end of the third pipe is fixedly connected to a fourth pipe, and the fourth pipe is fixedly connected to the air bag.

[0008] In one embodiment, a connecting frame is fixedly connected to the outside of the annular frame, a plurality of groups of fixing blocks are fixedly connected to the outside of the connecting frame, a piston groove is provided in the fixing block, a piston block is slidably connected in the piston groove, a spring is connected between the piston block and the piston groove, a limiting rod is fixedly connected to the bottom of the piston block, a sixth pipe is fixedly connected between two adjacent fixing blocks, the sixth pipe communicates with the piston groove, a fifth pipe is fixedly connected to the outside of the third pipe, and one end of the fifth pipe is fixedly connected to one of the fixing blocks.

[0009] In one embodiment, the control system includes a data acquisition unit, an inflation flow control unit, an early warning unit, and a control unit.

[0010] In one embodiment, the data acquisition unit includes a thick-walled cylinder stress analysis module and a stress and strain monitoring sub-module;

[0011] Among them, according to the theory of elasticity, the stress distribution of the thick-walled cylinder under internal pressure follows the Lame formula:

[0012] ;

[0013] ;

[0014] Among them: the radial stress is , is the internal pressure of the thick-walled cylinder, is the external pressure of the thick-walled cylinder, is the inner radius of the thick-walled cylinder, is the outer radius of the thick-walled cylinder;

[0015] When considering the influence of the temperature gradient, a thermal stress correction term is introduced:

[0016] ;

[0017] In the formula: is the thermal stress generated by the temperature change, is the linear expansion coefficient of the material, which reflects the expansion or contraction characteristics of the material when the temperature changes; is the elastic modulus of the material, indicating the ability of the material to resist elastic deformation; is the Poisson's ratio of the material, which describes the relationship between the transverse strain and the longitudinal strain of the material when it is stressed; is the temperature change;

[0018] The stress-strain monitoring sub-module includes collecting the output voltage of the strain gauge, and its calculation formula is:

[0019] ;

[0020] Among them, is the output voltage when the calculation strain gauge adopts a four-arm full-bridge circuit, is the sensitivity coefficient of the strain gauge, which reflects the sensitivity of the strain gauge to strain; is the relative change in the resistance of the strain gauge, which is proportional to the strain of the measured object; is the excitation voltage, that is, the voltage applied to the strain gauge bridge.

[0021] In one embodiment, the inflation flow control unit includes a thermodynamic coupling model, a pneumatic execution module, and a pressure closed-loop control module;

[0022] The thermodynamic coupling model is used to calculate the change rate of the internal energy of the air in the thick-walled cylinder, and the specific formula is as follows:

[0023] ;

[0024] Among them, represents the mass of the air m in the thick-walled cylinder multiplied by the specific heat capacity at constant volume and then multiplied by the change rate of temperature with time , that is, the change rate of the internal energy of the air in the thick-walled cylinder; represents the convective heat transfer between the inlet air and the air in the thick-walled cylinder, is the convective heat transfer coefficient, is the heat transfer area, is the inlet air temperature, is the air temperature in the thick-walled cylinder; represents the heat loss rate of the thick-walled cylinder to the outside;

[0025] Combined with the ideal gas state equation: ;

[0026] Among them is the gas pressure, is the gas volume, is the gas mass, is the gas constant, is the gas temperature;

[0027] The pneumatic execution module calculates the inflation flow using the proportional valve flow characteristic equation, and the characteristic equation is as follows:

[0028] ;

[0029] Among them, is the flow rate through the first valve, is the flow coefficient of the first valve, reflecting the flow capacity of the first valve; is the pressure difference before and after the first valve, is the density of air;

[0030] The pressure closed-loop control module estimates the state of the system based on the robust control algorithm formula of the state observer:

[0031] ;

[0032] ;

[0033] Wherein is the derivative of the state estimate value, is the state matrix of the system, is the input matrix, is the control input, is the observer gain matrix, is the actual output of the system, is the estimated value of the system output.

[0034] In one embodiment, the warning unit includes a reliability evaluation module and a threshold warning module;

[0035] The reliability evaluation module uses the fault tree analysis method, and the top event probability is calculated as follows:

[0036] ;

[0037] is to calculate the top event probability of the fault tree, where is the bottom event 's occurrence probability, is the number of bottom events; this formula assumes that the bottom events are independent of each other;

[0038] The threshold warning module uses the stress safety threshold calculation formula

[0039] ;

[0040] is the stress safety threshold, where is the strength of the material, that is, the maximum stress that the material can withstand; is the safety factor.

[0041] In one of the embodiments, the control method of the control unit is as follows:

[0042] First, for the predictive control based on a deep neural network (DNN-MPC), its objective function is:

[0043] ;

[0044] where is the predicted stress value at the th moment, is the reference value of the stress; is the prediction time domain; is the change in the control input at the th moment, is the control time domain; is the weighting coefficient, used to balance the weights of the output error and the change in the control input;

[0045] Meanwhile, the output of the controller in the control unit is calculated through the fuzzy adaptive PID control algorithm formula;

[0046] ;

[0047] where is the output of the controller, is the proportional coefficient, is the integral coefficient, is the differential coefficient; is the error at the th moment, that is, the difference between the set value and the actual value; is the integral of the error, reflecting the cumulative effect of the error; is the differential of the error;

[0048] Secondly, based on the digital twin system, the stress and temperature control equations are established;

[0049] ;

[0050] ;

[0051] where is the stress diffusion tensor, represents the diffusion term of the stress, and f is the source term of the stress; is the thermal diffusion coefficient, is the Laplacian operator of the temperature, representing the diffusion of the temperature, is the heat source term;

[0052] Subsequently, the error is calculated based on the error correction equation;

[0053] ;

[0054] For physical experiment data and virtual model simulation data the error between denotes the 2-norm, i.e., the square root of the sum of the squares of the vector elements;

[0055] Next, based on the safety threshold dynamic adjustment formula, dynamically adjust the safety threshold ;

[0056] ;

[0057] wherein is the safety threshold at the th moment, is the learning rate, used to control the step size of the safety threshold adjustment; is the reward function, which gives corresponding reward values according to the state of the system;

[0058] Finally, according to the actual stress and the safety threshold through the reward function formula, give the reward value;

[0059] ;

[0060] When the actual stress is less than the safety threshold, the reward value is +1, indicating that the system is in a safe state; when the actual stress is greater than or equal to the safety threshold, the reward value is -1, indicating that the system is in a dangerous state.

[0061] The beneficial effects of the present invention are:

[0062] First, compared with the prior art, in the present invention, the thick-walled cylinder is placed on the support frame. Subsequently, one end of the second pipe is inserted into the thick-walled cylinder, and through the connection of the connecting bolts with the thick-walled cylinder, the sealing cover is firmly installed on the thick-walled cylinder. After the gas is pressurized by the gas pressure pump, it is transported into the thick-walled cylinder. Finally, stress and temperature are detected through the strain gauge and the thermocouple. Through the setting of the control system, it is possible to simultaneously monitor and control the stress and the inflation flow rate. Through the collaborative monitoring and control, when it is detected that the stress approaches or reaches the safety threshold, the inflation flow rate can be adjusted in time to reduce the pressure change rate, thereby reducing stress concentration and avoiding damage to the equipment caused by excessive stress, and prolonging the service life of the equipment.

[0063] Second, compared with the prior art, in the present invention, the stress distribution of a thick-walled cylinder can be analyzed based on Lame's formula of elasticity mechanics, and a thermal stress correction term is introduced considering the influence of temperature gradient; a thermodynamic coupling model of the inflation process is constructed by combining the thermodynamic energy conservation equation and the ideal gas state equation; the fuzzy adaptive PID control algorithm is adopted, which can dynamically adjust the control parameters according to the error and the rate of change of the error. The stress-strain and temperature field data are collected by a strain gauge and a distributed optical fiber temperature measurement system respectively. The data can be preprocessed by a signal conditioning circuit and analog-to-digital conversion, and the temperature data is discretized for the heat conduction equation. Through the predictive control of a deep neural network (DNN-MPC), the future state can be predicted by the DNN model trained offline, the control input sequence can be optimized by rolling, and multi-parameter coordinated control can be realized. By constructing a two-way mapping of real-time data between the virtual model and the physical experiment, the accuracy of the model can be improved by using an error correction equation, and the safety threshold can be dynamically adjusted by reinforcement learning. Rewards or punishments can be given according to whether the stress exceeds the safety range. Experimental tests can be carried out within a specific internal pressure and temperature range. In the prior art, there may only be monitoring or control for a single physical quantity, while this system can simultaneously monitor and control the stress and inflation flow rate of the thick wall of a compressed air energy storage cylinder. Through a multi-parameter coupling control algorithm, the mutual influence between stress and flow rate is comprehensively considered to achieve more accurate control of the experimental process and improve the reliability and accuracy of experimental results.

[0064] Third, compared with the prior art, in the present invention, the predictive control (DNN-MPC) algorithm based on a deep neural network can more accurately predict the future state of the system, adjust the control strategy in advance, thereby significantly improving the control accuracy and response speed. By introducing the digital twin technology, a two-way mapping and error correction of real-time data between the virtual model and the physical experiment are realized, which enables the experimental process to be rehearsed and optimized in a virtual environment, timely discover potential problems and make adjustments, greatly shortening the experimental period and cost. Traditional safety monitoring usually uses a fixed threshold for early warning, which is difficult to adapt to the dynamic changes during the experimental process. Through the adaptive safety boundary mechanism of reinforcement learning, the safety threshold can be dynamically adjusted according to the real-time experimental data, and potential safety risks can be discovered and processed in a timely manner, providing more reliable safety protection for experimental personnel and equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 is a schematic structural diagram of the present invention;

[0066] Figure 2 is a schematic structural diagram during the test of the thick-walled cylinder in the present invention;

[0067] Figure 3 is a schematic structural diagram of another perspective during the test of the thick-walled cylinder in the present invention;

[0068] Figure 4 It is a schematic structural diagram of the support frame in the present invention;

[0069] Figure 5 is Figure 4 an enlarged structural diagram of area A in

[0070] Figure 6 a schematic cross-sectional structure diagram of the fixing block in the present invention.

[0071] The markings in the figure are:

[0072] 1. Gas cylinder; 2. First valve; 3. First pipeline; 4. Gas booster pump; 5. Second pipeline; 6. Pressure gauge; 7. Second valve; 8. Pressure relief valve; 9. Third pipeline; 10. Third valve; 11. Fourth pipeline; 12. Fifth pipeline; 13. Airbag; 14. Sealing cover; 15. Connecting bolt; 16. Support frame; 17. Strain gauge; 18. Thermocouple; 19. Ring-shaped frame; 20. Connecting frame; 21. Fixing block; 22. Sixth pipeline; 23. Piston groove; 24. Spring; 25. Piston block; 26. Limiting rod; 27. Thick-walled cylinder. Detailed implementation manners

[0073] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by terms such as "front", "upper", "lower", "left", "right", "vertical", "horizontal", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, so it cannot be understood as a limitation to the present invention.

[0074] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0075] The following is a further description of the present invention in combination with the attached Figures 1-6 drawings.

[0076] Embodiment 1:

[0077] To solve the problems existing in the background art, the present application proposes the following technical solution: A device for testing the thick-wall stress and temperature of a compressed air energy storage cylinder, including an air tank 1, a support frame 16 and a control system. The output of the air tank 1 is connected to a first pipeline 3. A second pipeline 5 is provided outside the support frame 16. A gas pressurizing pump 4 is provided between the first pipeline 3 and the second pipeline 5. The input end of the gas pressurizing pump 4 is fixedly connected to the first pipeline 3, and the output end of the gas pressurizing pump 4 is fixedly connected to the second pipeline 5. After the gas is pressurized by the gas pressurizing pump 4 to reach the set pressure, it is transported into the thick-wall cylinder 27.

[0078] In a further design, one end of the second pipeline 5 is fixedly connected to a sealing cover 14. A pressure sensor is also fixedly connected to one end of the second pipeline 5 for measuring the pressure inside the thick-wall cylinder 27. A plurality of connecting bolts 15 are provided through the sealing cover 14. One end of the second pipeline 5 is inserted into the thick-wall cylinder 27. Through the connection between the connecting bolts 15 and the thick-wall cylinder 27, the sealing cover 14 is firmly installed outside the thick-wall cylinder 27.

[0079] Among them, a thick-wall cylinder 27 is provided on the support frame 16. A plurality of strain gauges 17 and thermocouples 18 are installed at the end of the thick-wall cylinder 27. The group of strain gauges 17 and thermocouples 18 are electrically coupled to the controller in the control system. Stress and temperature detection are carried out through the strain gauges 17 and thermocouples 18.

[0080] In a further design, a first valve 2 is installed in the first pipeline 3, a second valve 7 and a pressure gauge 6 are installed in the second pipeline 5, a pressure relief valve 8 is also installed in the second pipeline 5. An annular frame 19 is fixedly connected to the outside of the support frame 16. A plurality of air bags 13 are fixedly connected to the outside of the annular frame 19. A third pipeline 9 is fixedly connected to the outside of the second pipeline 5. A third valve 10 is fixedly connected in the third pipeline 9. One end of the third pipeline 9 is fixedly connected to a fourth pipeline 11. The fourth pipeline 11 is fixedly connected to the air bag 13. The gas will also enter the fourth pipeline 11 through the third pipeline 9 and finally enter the air bag 13, inflating the air bag 13. The thick-wall cylinder 27 on the support frame 16 is resisted and limited by the air bag 13.

[0081] In a further design, a connecting frame 20 is fixedly connected to the outside of the annular frame 19. A plurality of fixed blocks 21 are fixedly connected to the outside of the connecting frame 20. A piston groove 23 is provided in the fixed block 21. A piston block 25 is slidably connected in the piston groove 23. A spring 24 is connected between the piston block 25 and the piston groove 23. A limiting rod 26 is fixedly connected to the bottom of the piston block 25. A sixth pipeline 22 is fixedly connected between two adjacent fixed blocks 21. The sixth pipeline 22 communicates with the piston groove 23. A fifth pipeline 12 is fixedly connected to the outside of the third pipeline 9. One end of the fifth pipeline 12 is fixedly connected to one of the fixed blocks 21. The gas is transported into the piston groove 23 through the fifth pipeline 12, and the piston block 25 in the piston groove 23 is extruded, so that the piston block 25 drives the limiting rod 26 to move downward, and the end of the thick-walled cylinder 27 is abutted by the limiting rod 26 to ensure the stability of the thick-walled cylinder 27 during measurement.

[0082] The usage method of this embodiment is as follows: Place the thick-walled cylinder 27 on the support frame 16. Subsequently, insert one end of the second pipeline 5 into the thick-walled cylinder 27, and through the connection of the connecting bolt 15 with the thick-walled cylinder 27, fixedly install the sealing cover 14 on the thick-walled cylinder 27.

[0083] Open all valves. After the gas is pressurized by the gas pressure pump 4, it is transported into the thick-walled cylinder 27. At the same time, the gas will also enter the fourth pipeline 11 through the third pipeline 9 and finally enter the airbag 13, inflating the airbag 13. The thick-walled cylinder 27 on the support frame 16 is abutted and limited by the airbag 13. At the same time, the gas in the second pipeline 5 will also enter the fifth pipeline 12, and the gas is transported into the piston groove 23 through the fifth pipeline 12, and the piston block 25 in the piston groove 23 is extruded, so that the piston block 25 drives the limiting rod 26 to move downward, and the end of the thick-walled cylinder 27 is abutted by the limiting rod 26 to ensure the stability of the thick-walled cylinder 27 during measurement; finally, stress and temperature detection can be carried out through the strain gauge 17 and the thermocouple 18.

[0084] Embodiment 2:

[0085] The control system includes a data acquisition unit, an inflation flow control unit, an early warning unit, and a control unit.

[0086] The data acquisition unit includes a stress analysis module for the thick-walled cylinder 27 and a stress and strain monitoring sub-module;

[0087] Among them, according to the theory of elasticity, the stress distribution of the thick-walled cylinder 27 under internal pressure follows the Lame formula in the stress analysis module of the thick-walled cylinder 27:

[0088] ;

[0089] ;

[0090] Where: The radial stress is , is the pressure inside the thick-walled cylinder 27, is the external pressure of the thick-walled cylinder 27, is the inner radius of the thick-walled cylinder 27, is the outer radius of the thick-walled cylinder 27;

[0091] Among them, this formula can be used to accurately calculate the radial stress distribution at different positions inside the thick-walled cylinder 27, providing an important basis for the strength design and material selection of the thick-walled cylinder 27. In the design of the thick-walled cylinder 27, understanding the radial stress distribution helps to determine the wall thickness of the thick-walled cylinder 27 to ensure that it will not rupture or other dangerous situations when subjected to internal pressure.

[0092] When considering the influence of temperature gradient, a thermal stress correction term is introduced:

[0093] ;

[0094] Where: is the thermal stress caused by temperature change, is the linear expansion coefficient of the material, which reflects the expansion or contraction characteristics of the material when the temperature changes; is the elastic modulus of the material, which indicates the material's ability to resist elastic deformation; is the Poisson's ratio of the material, which describes the relationship between the lateral strain and the longitudinal strain of the material when it is subjected to stress; is the temperature change, and the temperature is measured by the thermocouple 18;

[0095] Among them, during the compressed air energy storage process, the air pressure and temperature in the thick-walled cylinder 27 will change, and the temperature change will cause thermal stress in the thick-walled cylinder 27. The thermal stress may be superimposed on the mechanical stress, thereby affecting the strength and life of the thick-walled cylinder 27. By calculating the thermal stress through this formula, the influence of thermal stress can be considered in the design, and corresponding measures can be taken to reduce the harm of thermal stress to the cylinder, such as selecting appropriate materials, optimizing structural design, etc.

[0096] The stress strain monitoring submodule includes collecting the output voltage of the strain gauge 17, and the calculation formula is:

[0097] ;

[0098] Analog-to-digital conversion: 24-bit Δ-Σ ADC, sampling rate 10kHz;

[0099] The "Δ-Σ" is an analog-to-digital conversion technology, namely delta-sigma (delta-sigma) modulation technology, which converts the input analog signal into a digital signal through oversampling and noise shaping.

[0100] "ADC" is the abbreviation of Analog-to-Digital Converter, which means analog-to-digital converter and is used to convert continuous analog signals into discrete digital signals for convenient processing by digital devices such as computers. 24-bit indicates that the resolution of this analog-to-digital converter is 24 bits, meaning it can divide the analog signal into 2 to the 24th power (16,777,216) different quantization levels.

[0101] Among them, is the output voltage when the strain gauge 17 adopts a four-arm full-bridge circuit, is the sensitivity coefficient of the strain gauge 17, which reflects the sensitivity of the strain gauge 17 to strain; is the relative change in the resistance of the strain gauge 17, which is proportional to the strain of the measured object; is the excitation voltage, that is, the voltage applied to the bridge of the strain gauge 17.

[0102] Among them, in the stress and strain monitoring sub-module, the strain gauge 17 is the key component for measuring stress and strain. Through this formula, the change in the resistance of the strain gauge 17 can be converted into a voltage signal for subsequent signal conditioning and analog-to-digital conversion. According to the magnitude of the output voltage, the strain value of the measured object can be calculated, and then the stress value can be obtained, providing data support for monitoring the stress state of the thick-walled cylinder 27;

[0103] The inflation flow control unit includes a thermodynamic coupling model, a pneumatic execution module, and a pressure closed-loop control module;

[0104] The thermodynamic coupling model is used to calculate the change rate of the internal energy of the air in the thick-walled cylinder 27, specifically as follows:

[0105] ;

[0106] Among them, represents the mass m of the air in the thick-walled cylinder 27 multiplied by the specific heat capacity at constant volume and then multiplied by the change rate of temperature with time , that is, the change rate of the internal energy of the air in the thick-walled cylinder 27; represents the convective heat transfer between the intake air and the air in the thick-walled cylinder 27, is the convective heat transfer coefficient, is the heat transfer area, is the intake air temperature, is the air temperature in the thick-walled cylinder 27; represents the heat loss rate of the thick-walled cylinder 27 to the outside.

[0107] Among them, through this equation, the variation law of the air temperature in the cylinder with time can be analyzed, and the energy transfer situation during the air charging process can be understood. In the design and operation of a compressed air energy storage system, mastering the temperature variation law is crucial for optimizing the system efficiency and ensuring system safety. For example, the air charging speed can be adjusted according to the temperature variation to avoid system failures caused by excessive temperature.

[0108] Combined with the ideal gas state equation:

[0109] where is the gas pressure, is the gas volume, is the gas mass, is the gas constant, is the gas temperature;

[0110] Among them, in a compressed air energy storage system, air can be approximately regarded as an ideal gas. Through this equation, the third parameter can be calculated based on any two of the known pressure, volume, and temperature parameters. In the control and management system of the experimental device, this method can be used in combination with the energy conservation equation to accurately simulate and control the air charging process. For example, the air charging flow rate can be adjusted according to the changes in pressure and temperature.

[0111] The pneumatic execution module calculates the air charging flow rate using the proportional valve flow characteristic equation, and the characteristic equation is as follows:

[0112] ;

[0113] where is the flow rate through the first valve 2, is the flow coefficient of the first valve 2, which reflects the flow capacity of the first valve 2; is the pressure difference across the first valve 2, is the density of air;

[0114] Function: In the air charging flow control system, the first valve 2 is the key execution element for controlling the air charging flow rate. Through this equation, the flow rate through the regulating valve can be calculated based on the pressure difference across the first valve 2 and the air density. During the control process, the flow coefficient can be changed by adjusting the opening degree of the first valve 2 so as to achieve accurate control of the air charging flow rate.

[0115] The pressure closed-loop control module estimates the state of the system based on the robust control algorithm formula of the state observer:

[0116] ;

[0117] ;

[0118] where is the derivative of the state estimate value, is the state matrix of the system, is the input matrix, is the control input, is the observer gain matrix, is the actual output of the system, is the estimated value of the system output. The second equation is the control law, and the control input is calculated according to the state estimate value , where is the feedback gain matrix.

[0119] Function: In the inflation flow control system, due to the uncertainties and disturbances existing in the system, traditional control methods may not be able to ensure the stability and control accuracy of the system. The robust control algorithm based on the state observer estimates the state of the system through the state observer and performs feedback control according to the estimated state, which can effectively suppress the uncertainties and disturbances of the system and improve the robustness and control performance of the system.

[0120] The warning unit includes a reliability evaluation module and a threshold warning module;

[0121] The reliability evaluation module adopts the fault tree analysis method, and the top event probability is calculated as follows:

[0122] ;

[0123] is to calculate the top event probability of the fault tree, where is the occurrence probability of the bottom event , is the number of bottom events. This formula assumes that the bottom events are independent of each other;

[0124] In the safety monitoring and warning module, the fault tree analysis method is a commonly used reliability evaluation method. By constructing a fault tree, decomposing the faults (top events) of the system into multiple basic faults (bottom events), and calculating the occurrence probabilities of the bottom events, the occurrence probability of the top event can be obtained. This helps to evaluate the reliability and safety of the system, find out the weak links of the system, and provide a basis for formulating safety measures and maintenance plans.

[0125] The threshold warning module adopts the stress safety threshold calculation formula

[0126] ;

[0127] is the stress safety threshold, where is the strength of the material, that is, the maximum stress that the material can withstand; is the safety factor, usually taking values between 1.5 and 2.0, which is used to consider factors such as the uncertainty of material properties and the fluctuation of loads.

[0128] Function: In the safety monitoring and early warning module, the stress safety threshold is an important basis for judging whether the system is safe. The stress safety threshold is calculated by this formula, and the actually measured stress value is compared with the safety threshold. When the actual stress value exceeds the safety threshold, the system issues a warning signal to remind the operator to take corresponding measures to avoid safety accidents.

[0129] The control method of the control unit is as follows:

[0130] First, a deep neural network-based predictive control DNN-MPC is proposed, and its objective function is:

[0131] ;

[0132] where, is the predicted stress value at the th moment, is the reference value of the stress; is the prediction horizon; is the change amount of the control input at the th moment, is the control horizon; is the weighting coefficient, which is used to balance the weights of the output error and the change of the control input;

[0133] Function: In the thick-walled stress and temperature test experimental device of compressed air energy storage cylinders, the system has the characteristic of multi-parameter coupling, and it is difficult for traditional control methods to achieve precise control. The deep neural network predictive control algorithm predicts the future state of the system through an offline-trained deep neural network model and rolls up and optimizes the control input sequence according to the objective function, which can effectively handle the nonlinearity and multi-parameter coupling problems of the system and improve the control accuracy and stability of the system. `

[0134] At the same time, the output of the controller in the control unit is calculated through the fuzzy adaptive PID control algorithm formula;

[0135] ;

[0136] where, is the output of the controller, is the proportional coefficient, is the integral coefficient, is the differential coefficient; is the error at the th moment, that is, the difference between the set value and the actual value; is the integral of the error, which reflects the cumulative effect of the error; is the differential of the error, reflecting the changing trend of the error

[0137] The PID control algorithm is a widely used control algorithm. By adjusting the proportional, integral, and differential coefficients, precise control of the system can be achieved. In the control management system of the compressed air energy storage cylinder thick-wall stress and temperature test experimental device, the PID control algorithm can be used to control parameters such as inflation flow rate and pressure, enabling the output of the system to quickly and accurately track the set value. Fuzzy adaptive PID control is based on traditional PID control and dynamically adjusts and through fuzzy rules to adapt to the nonlinearity and uncertainty of the system and improve the control effect.

[0138] Secondly, based on the digital twin system, establish the stress and temperature control equations;

[0139] ;

[0140] ;

[0141] Meaning: The first equation is the stress control equation, describing the stress changing law over time. Among them is the stress diffusion tensor, represents the diffusion term of the stress, and f is the source term of the stress. The second equation is the temperature control equation, describing the temperature changing law over time. Among them is the thermal diffusion coefficient, is the Laplace operator of the temperature, representing the diffusion of the temperature, is the heat source term.

[0142] Function: In the digital twin system, these two equations are used to construct a virtual model to simulate the stress and temperature distribution of the compressed air energy storage cylinder thick-wall. By performing two-way mapping between the virtual model and the real-time data of the physical experiment, real-time monitoring and prediction of the physical system can be achieved. When the state of the physical system changes, the virtual model can promptly reflect this change and make corresponding adjustments, providing support for system optimization and decision-making.

[0143] Subsequently, calculate the error based on the error correction equation;

[0144] ;

[0145] is the physical experiment data and the virtual model simulation data the error between them, represents the 2-norm, that is, the square root of the sum of the squares of the vector elements.

[0146] Function: In the digital twin system, the error correction equation is used to evaluate the consistency between the virtual model and the physical system. By calculating the error, problems existing in the virtual model can be detected in a timely manner, and the model can be corrected and optimized to improve the accuracy and reliability of the virtual model.

[0147] Next, based on the safety threshold dynamic adjustment formula, the safety threshold is dynamically adjusted ;

[0148] ;

[0149] where is the safety threshold at the th moment, is the learning rate, which is used to control the step size of the safety threshold adjustment; is the reward function, which gives corresponding reward values according to the state of the system.

[0150] Function: In the thick-walled stress and temperature test experimental device of the compressed air energy storage cylinder, the operating conditions of the system may change, and the traditional fixed safety threshold may not be able to adapt to this change. The adaptive safety boundary mechanism dynamically adjusts the safety threshold according to the real-time state of the system through the method of reinforcement learning, which can better ensure the safety and reliability of the system.

[0151] Finally, through the reward function formula, the reward value is given according to the size relationship between the actual stress and the safety threshold ;

[0152] ;

[0153] When the actual stress is less than the safety threshold, the reward value is +1, indicating that the system is in a safe state; when the actual stress is greater than or equal to the safety threshold, the reward value is -1, indicating that the system is in a dangerous state.

[0154] In summary, in the present invention, the stress distribution of the thick-walled cylinder 27 can be analyzed based on the Lame formula of elasticity mechanics, and the thermal stress correction term is introduced considering the influence of the temperature gradient; the thermodynamic coupling model of the charging process is constructed by combining the thermodynamic energy conservation equation and the ideal gas state equation; the fuzzy adaptive PID control algorithm is adopted, which can dynamically adjust the control parameters according to the error and the error change rate.

[0155] In the present invention, the stress-strain and temperature field data are respectively collected through the strain gauge 17 and the distributed optical fiber temperature measurement system, and the data can be preprocessed by using the signal conditioning circuit and the analog-to-digital conversion, and the temperature data is discretized for the heat conduction equation.

[0156] In the present invention, the fault tree analysis method is used for reliability assessment, and the stress safety threshold can be set according to the tensile strength of the material and the safety factor to achieve threshold warning.

[0157] In the present invention, a predictive control DNN-MPC based on a deep neural network is proposed, which can predict the future state through an offline-trained DNN model, roll-optimize the control input sequence, and achieve multi-parameter collaborative control.

[0158] In the present invention, a two-way mapping between the virtual model and the real-time data of physical experiments is constructed, and the accuracy of the model can be improved by using an error correction equation.

[0159] In the present invention, the safety threshold is dynamically adjusted based on reinforcement learning, and rewards or punishments can be given according to whether the stress exceeds the safety range. The performance of the system in terms of stress control accuracy of ±2.5%FS, temperature control accuracy of ±1.0°C, and flow regulation response time <500 ms has been verified through experimental tests within a specific internal pressure and temperature range.

[0160] In summary, in the prior art, there may only be monitoring or control for a single physical quantity, while the present system can simultaneously perform collaborative monitoring and control on the stress and inflation flow rate of the thick wall of the compressed air energy storage cylinder. Through a multi-parameter coupling control algorithm, the mutual influence between stress and flow rate is comprehensively considered to achieve more precise control of the experimental process and improve the reliability and accuracy of experimental results.

[0161] The predictive control DNN-MPC algorithm based on a deep neural network in the present invention can more accurately predict the future state of the system and adjust the control strategy in advance, thus significantly improving the control accuracy and response speed. The digital twin technology is introduced in the present invention to achieve two-way mapping and error correction of real-time data between the virtual model and physical experiments, which enables the experimental process to be rehearsed and optimized in a virtual environment, timely discover potential problems and make adjustments, greatly shortening the experimental cycle and cost. Traditional safety monitoring usually uses fixed threshold warning and is difficult to adapt to the dynamic changes in the experimental process. The adaptive safety boundary mechanism based on reinforcement learning in the present invention can dynamically adjust the safety threshold according to the real-time data of the experiment, timely discover and handle potential safety risks, and provide more reliable safety protection for experimental personnel and equipment.

[0162] The standard parts used in the present invention can all be purchased from the market. The special-shaped parts can be customized according to the description in the specification and the drawings. The specific connection methods of each part all adopt conventional means such as bolts, rivets, and welding that are mature in the prior art. The machines, parts, and equipment all adopt conventional models in the prior art, and the circuit connection adopts the conventional connection method in the prior art, which will not be elaborated here. The content not described in detail in this specification belongs to the prior art well-known to those skilled in the art.

[0163] Although embodiments of the present invention have been shown and described, the scope of the present invention is defined by the appended claims and their equivalents for those of ordinary skill in the art.

Claims

1. A device for testing the thick-wall stress and temperature of an energy storage cylinder for compressed air, characterized in that, It includes a gas tank (1), a support frame (16) and a control system. The output of the gas tank (1) is connected to a first pipeline (3). A second pipeline (5) is provided outside the support frame (16). A gas booster pump (4) is provided between the first pipeline (3) and the second pipeline (5). The input end of the gas booster pump (4) is fixedly connected to the first pipeline (3), and the output end of the gas booster pump (4) is fixedly connected to the second pipeline (5). One end of the second pipeline (5) is fixedly connected to a sealing cover (14). Multiple groups of connecting bolts (15) penetrate through the sealing cover (14). A thick-walled cylinder (27) is provided on the support frame (16). Multiple groups of strain gauges (17) and thermocouples (18) are installed at the end of the thick-walled cylinder (27). The group of strain gauges (17) and thermocouples (18) are both electrically coupled to the control system. The control system includes a data acquisition unit. The data acquisition unit includes a stress and strain monitoring sub-module. In the stress and strain monitoring sub-module, the change in the resistance of the strain gauge (17) is converted into a voltage signal. According to the magnitude of the output voltage, the strain value of the measured object is calculated, and then the stress value is obtained to realize the monitoring of the stress of the thick-walled cylinder (27); among them, after the gas is pressurized by the gas booster pump (4) to reach the set pressure, it is transported into the thick-walled cylinder (27). The control system analyzes the stress distribution of the thick-walled cylinder (27) based on Lame's formula of elasticity mechanics, introduces a thermal stress correction term considering the influence of the temperature gradient, constructs a thermodynamic coupling model of the inflation process by combining the thermodynamic energy conservation equation and the ideal gas state equation, and adopts a fuzzy adaptive PID control algorithm to dynamically adjust the control parameters according to the error and the error change rate.

2. The stress and temperature testing device for the thick wall of an energy storage cylinder for compressed air according to claim 1, characterized in that, A first valve (2) is installed in the first pipeline (3). A second valve (7) and a pressure gauge (6) are installed in the second pipeline (5). A pressure relief valve (8) is also installed in the second pipeline (5).

3. The stress and temperature testing device for the thick wall of an energy storage cylinder for compressed air according to claim 2, characterized in that, An annular frame (19) is fixedly connected to the outside of the support frame (16). Multiple groups of air bags (13) are fixedly connected to the outside of the annular frame (19). A third pipeline (9) is fixedly connected to the outside of the second pipeline (5). A third valve (10) is fixedly connected in the third pipeline (9). One end of the third pipeline (9) is fixedly connected to a fourth pipeline (11). The fourth pipeline (11) is fixedly connected to the air bag (13).

4. A device for testing the thick-wall stress and temperature of an energy storage cylinder for compressed air according to claim 3, characterized in that, An external connection of the annular frame (19) is fixedly connected with a connecting frame (20). An external connection of the connecting frame (20) is fixedly connected with multiple fixing blocks (21). A piston groove (23) is arranged in the fixing block (21). A piston block (25) is slidably connected in the piston groove (23). A spring (24) is connected between the piston block (25) and the piston groove (23). A limiting rod (26) is fixedly connected to the bottom of the piston block (25). A sixth pipeline (22) is fixedly connected between two adjacent fixing blocks (21). The sixth pipeline (22) is communicated with the piston groove (23). An external connection of the third pipeline (9) is fixedly connected with a fifth pipeline (12). One end of the fifth pipeline (12) is fixedly connected inside one of the fixing blocks (21).

5. The stress and temperature testing device for the thick wall of an energy storage cylinder for compressed air according to claim 4, characterized in that, The control system further includes an air inflation flow control unit, a warning unit, and a control unit.

6. The stress and temperature testing device for the thick wall of an energy storage cylinder for compressed air according to claim 5, wherein The data acquisition unit further includes a stress analysis module for the thick-walled cylinder (27); Among them, according to the theory of elasticity, the stress distribution of the thick-walled cylinder (27) under internal pressure follows the Lame formula in the stress analysis module of the thick-walled cylinder (27): ； ； Among them: the radial stress is , representing the stress along the radius direction of the cylinder, and the circumferential stress is , representing the stress along the circumferential direction of the cylinder is the internal pressure of the thick-walled cylinder (27), is the external pressure of the thick-walled cylinder (27), is the inner radius of the thick-walled cylinder (27), is the outer radius of the thick-walled cylinder (27); When considering the influence of temperature gradient, a thermal stress correction term is introduced: ； Where: is the thermal stress caused by temperature change, is the linear expansion coefficient of the material, which reflects the expansion or contraction characteristics of the material when the temperature changes; is the elastic modulus of the material, which indicates the material's ability to resist elastic deformation; is the Poisson's ratio of the material, which describes the relationship between the lateral strain and the longitudinal strain of the material when it is subjected to stress; is the temperature change; The stress and strain monitoring sub-module includes collecting the output voltage of the strain gauge (17), and its calculation formula is: ； Among them, To calculate the output voltage when the strain gauge (17) adopts a four-arm full-bridge circuit, is the sensitivity coefficient of the strain gauge (17), which reflects the sensitivity of the strain gauge (17) to strain; is the relative change in the resistance of the strain gauge (17), which is proportional to the strain of the object under test; is the excitation voltage, that is, the voltage applied to the bridge of the strain gauge (17).

7. A thick-walled stress and temperature test device for an energy storage cylinder for compressed air according to claim 6, characterized in that The air inflation flow control unit includes a thermodynamic coupling model, a pneumatic execution module, and a pressure closed-loop control module; The thermodynamic coupling model is used to calculate the change rate of the internal energy of the air in the thick-walled cylinder (27), and the specific formula is as follows: ； Among them, represents the product of the air mass m in the thick-walled cylinder (27) and the specific heat capacity at constant volume multiplied by the rate of change of temperature with time , that is, the rate of change of the internal energy of the air in the thick-walled cylinder (27); represents the convective heat transfer between the intake air and the air in the thick-walled cylinder (27), is the convective heat transfer coefficient, is the heat transfer area, is the intake air temperature, is the air temperature in the thick-walled cylinder (27); represents the heat loss rate of the thick-walled cylinder (27) to the outside; Combined with the ideal gas state equation: ; wherein is the gas pressure, is the gas volume, is the gas mass, is the gas constant, is the gas temperature; The pneumatic execution module calculates the air inflation flow using the proportional valve flow characteristic equation, and the characteristic equation is as follows: ； Among them, is the flow rate through the first valve (2), is the flow coefficient of the first valve (2), reflecting the flow capacity of the first valve (2); is the pressure difference before and after the first valve (2), is the density of air; The pressure closed-loop control module estimates the state of the system based on the robust control algorithm formula of the state observer: ； ； where is the derivative of the state estimate value, is the state matrix of the system, is the input matrix, is the control input, is the observer gain matrix, is the actual output of the system, is the estimated value of the system output.

8. A stress and temperature testing device for the thick wall of an energy storage cylinder for compressed air according to claim 5, characterized in that, The warning unit includes a reliability evaluation module and a threshold warning module; The reliability evaluation module uses the fault tree analysis method, and the probability of the top event is calculated by the following formula: ； To calculate the probability of the top event of a fault tree, where is the occurrence probability of the basic event , and is the number of basic events; This formula assumes that the bottom events are independent of each other; The threshold warning module uses the stress safety threshold calculation formula ； is the stress safety threshold, where is the strength of the material, that is, the maximum stress that the material can withstand; is the safety factor.

9. A device for testing the thick-wall stress and temperature of an energy storage cylinder for compressed air according to claim 5, characterized in that The control method of the control unit is as follows: First, based on the deep neural network-based predictive control (DNN-MPC), its objective function is: ； Among them, is the predicted stress value at the moment, is the reference value of the stress; is the prediction time domain; is the change amount of the control input at the moment, is the control time domain; is the weighting coefficient, which is used to balance the weights of the output error and the change of the control input; At the same time, the output of the controller in the control unit is calculated by the fuzzy adaptive PID control algorithm formula; ； Among them, is the output of the controller, is the proportional coefficient, is the integral coefficient, is the differential coefficient; is the error at the th moment, that is, the difference between the set value and the actual value; is the integral of the error, reflecting the cumulative effect of the error; is the differential of the error; Second, based on the digital twin system, stress and temperature control equations are established; ； ； where is the stress diffusion tensor, represents the diffusion term of stress, and f is the source term of stress; is the thermal diffusion coefficient, is the Laplacian operator of temperature, representing the diffusion of temperature, is the heat source term; Subsequently, the error is calculated based on the error correction equation; ； For physical experiment data and virtual model simulation data the error between represents the 2-norm, which is the square root of the sum of the squares of the vector elements; Next, based on the safety threshold dynamic adjustment formula, the safety threshold is dynamically adjusted ; ； Among them, is the safety threshold at the th moment, is the learning rate, which is used to control the step size of the safety threshold adjustment; is the reward function, which gives corresponding reward values according to the state of the system; Finally, a reward value is given according to the magnitude relationship between the actual stress and the safety threshold through the reward function formula; ； When the actual stress is less than the safety threshold, the reward value is +1, indicating that the system is in a safe state; when the actual stress is greater than or equal to the safety threshold, the reward value is -1, indicating that the system is in a dangerous state.

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