Fault prediction method for solid oxide fuel cell combined heat and power system

Abstract

The invention discloses a fault prediction method for a combined heat and power system of a solid oxide fuel cell, and belongs to the technical field of solid oxide fuel cells. The method comprises the steps that finite element sub-models of all components are established according to the structural composition of the solid fuel cell combined heat and power system, the solid fuel cell combined heat and power system is formed through integration, and the system is simulated according to the normal operation working condition to obtain output parameters under the normal working condition; then a fault model is established, output parameters of the system under different faults are obtained after simulation, the output parameters under the normal working condition are compared with the output parameters under different fault working conditions, and changes generated by the system after faults occur are analyzed; and finally, predicting whether the system has a fault or not and the fault type according to the output parameters of the actual system. According to the method, related characteristics of the SOFC system after different faults occur are simulated by utilizing an analogue simulation method, and whether the faults occur or not and fault types can be predicted according to output parameters of an actual system.

Description

Technical Field

[0001] The present invention relates to the technical field of solid oxide fuel cells, and in particular to a fault prediction method for a solid oxide fuel cell cogeneration system. Background Art

[0002] Solid Oxide Fuel Cell (SOFC) is an electrochemical power generation device that directly converts the chemical energy in fossil fuels into electrical energy under medium and high temperature conditions. Compared with traditional combustion-based power generation methods, SOFC power generation technology omits the combustion process, is not restricted by the Carnot cycle, and has no mechanical movement, thereby greatly reducing noise pollution and environmental pollution, and improving the utilization efficiency of fossil fuels, which can achieve a fuel utilization efficiency of more than 80%.

[0003] Solid oxide fuel cells have a large structure and complex performance. There are multiple coupling factors in the working process, and the coupling mechanism is complex. In addition, the SOFC development cycle is long and the stack cost is high, which affects the performance research of the solid oxide fuel cell cogeneration system. During the use of the SOFC system, frequent startup and shutdown, multiple hot and cold cycles, and mechanical and chemical compatibility inside the SOFC stack under high temperature environment make the system inevitably produce failure and degradation trends over time, reducing the reliability and durability of the system and hindering the commercialization of the SOFC system. During the operation of the SOFC system, faults can occur at any time at any position in the system, but can be generally divided into two categories: system peripheral equipment failure and stack internal failure, namely, pipeline failure, heat exchanger failure, reformer failure, electrode stratification failure and external load failure. By predicting the fault of the SOFC system, its health status can be understood in time. At present, the fault detection method of the SOFC system is usually to use machine learning methods to learn the collected historical data, build a fault prediction model, and then use the model to analyze the real-time collected status data for fault prediction. This method relies on a large amount of historical data, which takes a long time to obtain. In addition, these historical data cannot cover all possible fault types. The data is not comprehensive, which leads to the failure prediction model established not being able to predict all possible fault types. Based on this, a fault prediction method for solid oxide fuel cell cogeneration system is proposed. The simulation method is used to simulate the relevant characteristics of the SOFC system after different faults occur, saving time and economic costs for SOFC system research. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a fault prediction method for a solid oxide fuel cell cogeneration system.

[0005] The present invention specifically adopts the following technical solutions: A method for predicting a fault in a solid oxide fuel cell cogeneration system comprises the following steps: (1) According to the structural composition of the fuel cell cogeneration system, finite element sub-models of the heat exchanger components, reformer components, combustion chamber components, SOFC stack components, and external load components are established respectively; (2) According to the process flow of the fuel cell cogeneration system, the finite element sub-models of the components in step (1) are used as different nodes to build a finite element model of the fuel cell cogeneration system, and the model is debugged and corrected so that the difference between the output parameters of each node of the model under normal operating conditions and the output parameters of each node under actual normal operating conditions is within a preset range; (3) Analyze the main fault types existing in the fuel cell cogeneration system and establish corresponding fault models; (4) Using the finite element model of the fuel cell cogeneration system corrected in step (2), respectively running one of the fault models in step (3) to obtain output parameters of each node under different fault types, and comparing them with the output parameters of each node under actual operating conditions to analyze the impact of different fault types on the system operating state; (5) Based on the output parameters under normal operating conditions and when different fault types occur, the output parameters of the fuel cell cogeneration system under a certain actual operating condition are analyzed and compared to determine whether the system has a fault under the actual operating condition and the corresponding fault type.

[0006] Furthermore, the main fault types existing in the fuel cell cogeneration system in step (3) include: feed pipeline leakage fault, heat exchanger pipeline rupture fault, reformer carbon deposition fault, stack electrode stratification fault, and external load fault.

[0007] Furthermore, the feed pipeline leakage fault model established in step (3) is: ; When simulating the air side pipe leakage fault, set: , ; When simulating the fuel side pipeline leakage fault, set: , ; When simulating the simultaneous leakage of fuel and air side pipelines, set: , ; In the formula, is the gas flow rate at the air side pipeline outlet, is the gas flow rate at the air side pipeline inlet, is the gas flow rate at the outlet of the fuel side pipeline, is the gas flow rate at the fuel side pipeline inlet, is the gas leakage flow rate in the air side pipeline, is the gas leakage flow rate of the fuel side pipeline.

[0008] Furthermore, the heat exchanger pipe rupture fault model established in step (3) is: ; In the formula, is the flow rate of the fluid at the heat exchanger outlet, is the flow rate of the fluid at the heat exchanger inlet, is the pressure at the heat exchanger outlet, is the pressure at the heat exchanger inlet, is the failure coefficient of heat exchanger rupture failure, and .

[0009] Furthermore, when establishing the reformer fault model in step (3), the model is established by reducing the reforming efficiency of the reformer.

[0010] Furthermore, when establishing the reformer fault model in step (3), the reforming efficiency of the reformer is reduced by reducing the reaction area of ​​the reforming catalyst inside the reformer.

[0011] Furthermore, when establishing the stack electrode delamination fault model in step (3), the model is built by reducing the effective reaction area parameter between two adjacent layers.

[0012] Furthermore, when establishing the external load fault model in step (3), the model is established by reducing the input current of the external load.

[0013] Furthermore, the output parameters in steps (2), (3) and (5) include temperature and / or pressure and / or flow.

[0014] Furthermore, in step (4), when a feed pipeline leakage fault occurs, if the fuel side pipeline leaks, the temperature of the SOFC stack, the reformer, and the combustion chamber decreases, and the output voltage of the SOFC stack decreases; if the air side pipeline leaks, the temperature of the SOFC stack, the combustion chamber, and the reformer increases, and the output voltage of the SOFC stack increases; if the fuel side and air side pipelines leak at the same time, according to the leakage degree of the fuel side and air side pipelines, if the leakage degree of the fuel side and air side pipelines is the same, the SOFC stack will first decrease and then increase, the overall temperature will decrease, the reformer temperature will increase, the SOFC stack output voltage will first decrease and then increase, and the overall output voltage will decrease; When a heat exchanger pipe rupture occurs, if the heat exchanger hot gas pipe ruptures, the SOFC stack temperature drops and the SOFC stack output voltage decreases; if the heat exchanger cold gas pipe ruptures, the SOFC stack temperature continues to rise and the SOFC stack output voltage increases; if the heat exchanger hot gas and cold gas pipes rupture at the same time, the heat exchanger will produce local overcooling or overheating conditions; When a reformer carbon deposition failure occurs, the SOFC stack output voltage decreases, the internal pressure of the reformer increases, and the local temperature of the reformer increases; When an electrode stratification failure occurs, the SOFC stack output voltage decreases, and the SOFC stack temperature and reformer temperature fluctuate; When an external load fault occurs, the input current is 0, the output voltage of the SOFC stack will quickly rise to the open circuit voltage, the temperature of the SOFC stack will drop, and the temperature of the reformer will rise.

[0015] The present invention has the following beneficial effects: (1) The present invention provides a fault prediction method for a solid oxide fuel cell cogeneration system, which uses a simulation method to simulate the relevant characteristics of the SOFC system after different faults occur, saving time and economic costs for studying the SOFC system. In addition, based on this method, it is possible to predict whether a fault will occur and the type of fault based on the output parameters of the actual system, without the need to inspect and repair each component of the entire system; (2) When establishing the finite element model of the cogeneration system, the present invention first establishes finite element sub-models of each component such as the heat exchanger, reformer, combustion chamber, SOFC stack, external load, etc., and then integrates the finite element sub-models of each component according to the process flow to form a finite element model of the fuel cell cogeneration system. The present invention adopts a modular modeling method to establish the cogeneration system model. Each sub-model is independent of each other, which is not only convenient for arbitrarily adding or reducing sub-models and modifying the system model structure, but also the dynamic characteristics of the fluid can be observed at the inlet and outlet of each sub-model. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a flow chart of the present invention; Figure 2 A schematic diagram of the structure of the solid oxide fuel cell cogeneration system established by the present invention; Figure 3 The figure is a comparison diagram of the simulation results of the temperature of the stack and the reformer when the air side pipeline failure occurs in the solid oxide fuel cell cogeneration system of the present invention at the 100th minute and the actual test results, wherein (a) is a comparison diagram of the simulation results of the temperature of the stack and the actual test results, and (b) is a comparison diagram of the simulation results of the temperature of the reformer and the experimental test results; Figure 4The present invention is a comparison diagram of simulation results of the stack temperature, reformer temperature and stack output voltage and actual test results when the external load fails and the input current becomes 0 at the 626th minute of the solid oxide fuel cell cogeneration system of the present invention, wherein (a) is a comparison diagram of the simulation results of the stack temperature and the actual test results, (b) is a comparison diagram of the simulation results of the reformer temperature and the actual test results, and (c) is a comparison diagram of the simulation results of the stack output voltage and the actual test results; Figure 5 The simulation results of the fuel cell stack and the reformer when the fuel side pipeline leaks in the present invention, wherein (a) is the simulation result of the fuel cell stack and the reformer temperature, and (b) is the simulation result of the fuel cell stack output voltage; Figure 6 The simulation results of the fuel stack and the reformer when the fuel side pipeline and the air side pipeline leak at the same time according to the present invention, (a) is the simulation result of the temperature of the fuel stack and the reformer, and (b) is the simulation result of the output voltage of the fuel stack; Figure 7 The simulation results of the fuel cell stack when the heat pipe failure of the heat exchanger occurs in the present invention, (a) is the simulation result of the fuel cell stack temperature and the air temperature at the cathode inlet of the fuel cell stack, and (b) is the simulation result of the fuel cell stack output voltage; Figure 8 The simulation results of the fuel cell stack when a heat exchanger cold pipe failure occurs in the present invention, (a) is the simulation result of the fuel cell stack temperature and the fuel cell stack cathode inlet air temperature, (b) is the simulation result of the fuel cell stack output voltage; Fig. 9 The simulation results of the reformer and the stack when the reformer carbon deposition failure occurs in the present invention, (a) is the simulation result of the internal pressure of the reformer, and (b) is the simulation result of the output voltage of the stack; Fig.10 These are the simulation results of the fuel cell stack and the reformer when an electrode stratification failure occurs in the present invention. (a) is the simulation result of the fuel cell stack and the reformer temperature, and (b) is the simulation result of the fuel cell stack output voltage. DETAILED DESCRIPTION

[0017] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and specific examples.

[0018] Reference Figure 1 This embodiment provides a solid oxide fuel cell cogeneration system fault prediction method, comprising the following steps: (1) According to the structural composition of the fuel cell cogeneration system, finite element sub-models of the heat exchanger, reformer, combustion chamber, SOFC stack, external load and other components are established; (2) According to the process flow of the fuel cell cogeneration system, the finite element sub-models of the components in step (1) are used as different nodes to build a finite element model of the fuel cell cogeneration system, and the model is debugged and corrected so that the difference between the output parameters of each node of the model and the output parameters of each node in the actual operating conditions is within a preset range, and the output parameters include temperature, pressure, flow rate, and gas composition; (3) Analyze the main fault types existing in the fuel cell cogeneration system and establish corresponding fault models; (4) using the fuel cell cogeneration system finite element model corrected in step (2), respectively running at least one fault model in step (3) to obtain output parameters of each node under different fault types, and comparing them with the output parameters of each node under actual operating conditions to analyze the impact of different fault types on the system operating state; (5) Based on the output parameters under normal operating conditions and when different fault types occur, the output parameters of the fuel cell cogeneration system under a certain actual operating condition are analyzed and compared to determine whether the system has a fault under the actual operating condition and the corresponding fault type.

[0019] Specifically, the process of establishing the finite element sub-model of each component in the above step (1) is as follows: (11) Establish the geometric model of each component according to the specific structure of each component in the fuel cell cogeneration system; (12) Analyze the mass and energy changes of the fluid before and after it flows through each component, and establish the fluid control unit and solid control unit of each component; the fluid control unit mainly involves the dynamic changes of the flow rate, mole fraction and temperature of the fluid, and the solid control unit mainly involves the dynamic changes of the temperature of the solid material; (13) Integrate the fluid control unit and solid control unit of each component into the corresponding geometric model to construct a finite element sub-model of each component.

[0020] Specifically, the main fault types existing in the fuel cell cogeneration system in the above step (3) include: feed pipeline leakage fault, heat exchanger pipeline rupture fault, reformer carbon deposition fault, stack electrode stratification fault, external load fault, and the fault models corresponding to different fault types are as follows.

[0021] For the feed pipeline leakage fault, the established feed pipeline leakage fault model is: ; In the formula, is the gas flow rate at the air side pipeline outlet, is the gas flow rate at the air side pipeline inlet, is the gas flow rate at the outlet of the fuel side pipeline, is the gas flow rate at the fuel side pipeline inlet, is the gas leakage flow rate in the air side pipeline, is the gas leakage flow rate of the fuel side pipeline, and the reduced gas flow rates at the air side and fuel side pipeline outlets during the simulation are equal to the gas leakage flow rate at the air side , Fuel side gas leakage flow .

[0022] Specifically, during the simulation of the feed pipeline leakage fault, the simulation is performed by reducing the gas flow at the outlet of the air side and fuel side pipelines, that is: When simulating the air side pipe leakage fault, set: , ; When simulating the fuel side pipeline leakage fault, set: , ; When simulating the simultaneous leakage of fuel and air side pipelines, set: , .

[0023] For the heat exchanger pipe rupture failure, since the heat exchanger mainly uses the high-temperature exhaust gas discharged from the combustion chamber for heat exchange, the heat exchanger simulation model adopts a multi-layer sleeve spiral structure design, including a cold air pipe and a hot air pipe, and the cold and hot fluids flow in reverse. The cold air pipe is connected to the air side pipe, and the hot air pipe is connected to the high-temperature exhaust gas pipe. The high-temperature exhaust gas in the hot gas pipe exchanges heat with the air in the cold air pipe. The heat exchanger failure model is divided into a cold air pipe rupture model and a hot air pipe rupture model. When the heat exchanger ruptures, the gas leaks, and not only the gas flow rate and flow rate change, but also the pressure changes. Therefore, when establishing the heat exchanger pipe rupture failure model, the gas flow rate and pressure are considered, and the failure is simulated by applying a failure coefficient to the flow rate of the heat exchanger inlet fluid and the inlet pressure. The failure coefficient is the percentage of the fluid leakage to the total amount of the heat exchanger inlet fluid. The established heat exchanger pipe rupture failure model is: ; In the formula, is the flow rate of the fluid at the heat exchanger outlet, is the flow rate of the fluid at the heat exchanger inlet, is the pressure at the heat exchanger outlet, is the pressure at the heat exchanger inlet, is the failure coefficient of heat exchanger rupture failure, and .

[0024] Specifically, when simulating a heat exchanger pipe rupture failure, the heat exchanger rupture failure coefficient is adjusted to reduce the flow rate of the heat exchanger outlet fluid for simulation; specifically, if the cold air pipe rupture is simulated, the flow rate of the cold air pipe outlet fluid is adjusted; if the hot air pipe rupture is simulated, the flow rate of the hot air pipe outlet fluid is adjusted; if the cold air pipe and the hot air pipe are simulated to be ruptured at the same time, the flow rates of the cold air pipe and the hot air pipe outlet fluids are adjusted at the same time.

[0025] For reformer failure, the performance degradation of the reformer is mainly due to the reduction of the reaction area of ​​the internal reforming catalyst, which causes incomplete reforming reaction, resulting in the normal reforming reaction in the reformer to produce CO and H 2 In addition, it will also cause carbon deposits, that is, ; For reformer failure, simulation is performed by reducing the reforming efficiency of the reformer, specifically by reducing the reaction area of ​​the reforming catalyst inside the reformer.

[0026] For stack electrode delamination failure, it will lead to increased stack activation loss and ohmic loss. Electrodes are usually divided into anode layer, electrolyte layer, and cathode layer. When stack electrode delamination failure occurs, the anode layer or cathode layer of the electrode is separated from the electrolyte layer, resulting in a reduction in the effective conductive area. Therefore, modeling is performed by reducing the effective reaction area parameter between two adjacent layers, that is, reducing the effective reaction area parameter between the anode layer and the electrolyte layer or between the cathode layer and the electrolyte layer for simulation.

[0027] For external load fault, the input current of the external load is reduced to simulate.

[0028] By simulating each model, we get: When a feed pipeline leak occurs, if the fuel side pipeline leaks, the temperature of the SOFC stack, reformer, and combustion chamber will drop, and the output voltage of the SOFC stack will decrease; if the air side pipeline leaks, the temperature of the SOFC stack, combustion chamber, and reformer will rise, and the output voltage of the SOFC stack will increase; if the fuel side and air side pipelines leak at the same time, the impact will be different depending on the leakage degree (leakage rate) of the fuel side and air side pipelines. If the leakage degree of the fuel side and air side pipelines is the same, the temperature of the SOFC stack will increase first. The temperature of the SOFC stack decreases and then increases, the overall temperature decreases, the reformer temperature increases, the SOFC stack output voltage decreases first and then increases, and the overall output voltage decreases; if the air leakage is larger than the fuel side, the temperature of the SOFC stack, reformer, and combustion chamber decreases, and the SOFC stack output voltage decreases; conversely, the temperature of the SOFC stack, combustion chamber, and reformer increases, and the SOFC stack output voltage increases. However, in these two cases, the leakage on the air side and the fuel side is not large and the leakage degree is not much different. If the leakage of the two is too large or the leakage degree is too different, an obvious abnormality will occur; When a heat exchanger pipe rupture occurs, the SOFC stack temperature drops and the output voltage decreases if the heat exchanger hot air pipe ruptures. This is because the cathode air heating is insufficient and the system energy utilization rate is reduced if the heat exchanger hot air pipe ruptures. The cathode air intake is reduced, the stack temperature continues to rise, and the output voltage increases. If the duration is long, the stack performance will degrade and the output voltage will be unstable. If the heat exchanger hot air and cold air pipes rupture at the same time, the SOFC system temperature control will fail completely, the performance will drop sharply, and the heat exchanger will be partially overcooled or overheated. When a reformer carbon deposition failure occurs, the reforming efficiency is reduced, resulting in insufficient hydrogen supply, affecting the electrochemical reaction of the fuel cell stack, reducing the output voltage, and blocking the reformer flow channel, causing excessive pressure inside the reformer and excessive local temperature. When electrode stratification failure occurs, the performance of the SOFC stack is reduced, the output voltage is reduced, and the temperature of the SOFC stack and the reformer fluctuate; When an external load fault occurs, the input current is 0, the output voltage of the fuel cell stack will quickly rise to the open circuit voltage, the temperature of the fuel cell stack will drop, and the temperature of the reformer will rise.

[0029] Reference Figure 2 This embodiment constructs a typical solid oxide fuel cell cogeneration system, which includes: a heat exchanger, a reformer, a combustion chamber, a SOFC stack, and an external load connected to the power output end of the SOFC. The fuel side pipeline and the deionized water pipeline are connected to the fuel inlet and the steam inlet of the reformer respectively, and the fuel and deionized water are preheated by a heater before entering the reformer. The mixed steam of the fuel and the deionized water undergoes a reforming reaction in the reformer to generate a reformed gas H 2 and CO 2 The reformed gas outlet of the reformer is connected to the anode gas inlet of the SOFC stack, and the air side pipeline is connected to the cathode gas inlet of the SOFC stack after passing through the heat exchanger. In the SOFC stack, the anode gas and the cathode gas react to output electrical energy, while the unreacted gas (H 2 and CO 2 ) as exhaust gas emission; the exhaust gas outlet of the SOFC stack is connected to the combustion chamber and burns in the combustion chamber to produce high-temperature flue gas. A part of the high-temperature flue gas discharged from the combustion chamber is connected to the heat exchanger through a pipeline and is used to preheat the air transported by the air duct, and the other part of the high-temperature flue gas is connected to the reformer through a pipeline and is used to provide heat for the reforming reaction of the reformer, and can also provide heat for heating fuel and deionized water.

[0030] Based on the above solid oxide fuel cell cogeneration system, this embodiment first establishes a finite element model of the SOFC system under normal operating conditions and verifies its accuracy, specifically:

[0031] Finite element sub-models of heat exchanger, reformer, combustion chamber, SOFC stack, external load and other components are established in MATLAB / Simulink. According to the process flow of fuel cell cogeneration system, the finite element sub-models of each component are used as different nodes to build a finite element model of fuel cell cogeneration system. Then, the input parameter data under normal operating conditions are imported into the finite element model of the system, that is, the input natural gas flow rate is 8.2L / min, the cathode air flow rate is 115L / min, and the deionized water flow rate is 25L / min. The actual output data under normal operating conditions are: SOFC stack temperature is about 750℃, reformer temperature is 820~860℃ ℃ (the temperature of the reformer fluctuates greatly during actual operation, and the temperature is set to 850℃ in this embodiment and simulated at this temperature), the actual output voltage at a constant output current of 25A is 60.4V, and the air intake amount of the SOFC cathode, the fuel intake amount and the exhaust rate of each component are adjusted on the basis of the imported input parameter data so that the error between the simulated output data and the actual output data of the finite element model of the system is within a preset range, that is, the error range of the temperature of each component, especially the SOFC stack temperature and the reformer temperature is ensured to be within ±5℃, more preferably ±2℃, and the error of the output voltage of the SOFC stack is within 0.5%. At this time, it is considered that the established model is reasonably accurate.

[0032] In the above-mentioned process of establishing the finite element sub-model of each component, the finite element sub-model of each component is also dynamically simulated according to the normal operating conditions of the system, and the accuracy of the model of each component is verified, that is, to ensure that the error between the simulation results of the finite element sub-model of each component and the output data of each component under the actual operating conditions is within a preset range, especially the error range of the SOFC stack temperature and the reformer temperature is ±5°C, more preferably ±2°C, and the error of the output voltage of the SOFC stack is within 0.5%. If the output results of the model of each component have a large error with the actual when the accuracy of each component is verified, the sub-model structure of the corresponding component needs to be adjusted; after the finite element sub-model of each component is accurately verified, the finite element sub-model of each component is constructed as different nodes according to the process flow of the fuel cell cogeneration system to form a finite element model of the fuel cell cogeneration system under normal operating conditions.

[0033] In addition, in the above-mentioned finite element sub-model of the SOFC stack, the edge effect of the SOFC stack is ignored, all single cells have exactly the same dynamic behavior, there is no influence between the single cells, the output voltage of each single cell is accumulated as the total output voltage of the stack, the SOFC stack model is equivalent to the single cell model, and the electrical characteristic relationship of each node of the stack (i.e., the stack inlet, stack outlet, and stack interior) adopts a quasi-static electrochemical model; at the same time, the voltage of each node of the stack is set to be equal, and the working voltage of the single cell is calculated using the Nernst equation, that is: ; in, is the output voltage of the SOFC stack, is the Nernst voltage, , and They are ohmic loss, activation loss and concentration loss respectively. By comparing and debugging with actual data, the output value error between them and the actual cogeneration system is within the set value.

[0034] In this embodiment, the natural gas flow rate is adjusted to 8.5 L / min, the cathode air flow rate is 115 L / min, the deionized water flow rate is 24.8 L / min, and the current setting value is 25 A. The SOFC system finite element model constructed is operated, and the output parameters under normal conditions are basically consistent with the actual system output parameters, the output voltage is 60.40 V, the stack temperature is 749.80°C, and the reformer temperature is 852.20°C, indicating that the established SOFC system finite element model can accurately simulate the actual operating state. On this basis, according to the established fault models, the output parameters of each node of the system when different faults occur are simulated, and then the output parameters under normal conditions and when each fault occurs are combined with the actual operating results to quickly predict the faults generated by the actual system.

[0035] In addition, when simulating actual system failures, since the output parameters of each node in different systems are also different during actual operation, the model needs to be adjusted according to the actual operating conditions of the system to better simulate the failure situation.

[0036] Take the actual air side pipeline failure of a system as an example. At the 100th minute, the air side pipeline failure occurred. Before the failure, the air flow rate of the air side pipeline was 119L / min. At the 100th minute, the air flow rate dropped to 113L / min, and the air leakage was 6L / min. After the leakage was discovered, it was handled in time without causing a major impact. For this failure, when simulating on the Matlab / Simulink platform, the air flow rate was adjusted from 119L / min to 113L / min for simulation. Figure 3The figure shows the comparison between the simulation results and the actual test results of the SOFC stack temperature and reformer temperature when the air side pipeline failure occurs in the solid oxide fuel cell cogeneration system at the 100th minute. Figure 3 It can be seen that when an air-side pipeline failure occurs, the temperature of the stack and the reformer temperature rise, and the change trend of the simulation results is basically consistent with the actual results. In addition, for the simulation of air-side pipeline failure leakage, the air leakage can be increased arbitrarily during the actual simulation process, and even leaked completely, but when the leakage reaches a certain level, the system cannot operate normally. When the air flow rate is reduced to 100L / min during the simulation process, the temperature of the stack has reached about 850℃ after stabilization, which is 100℃ higher than the normal operating temperature. However, when the system is actually running, it will not wait until the temperature of the stack rises to 850℃ before discovering the problem and performing maintenance.

[0037] Taking an actual external load failure in a system as an example, the input current of the external load suddenly changes to 0A at the 626th minute and recovers to 25A at the 643rd minute. Figure 4 The figure shows the comparison between the simulation results and the actual test results of the stack temperature, reformer temperature and stack output voltage of the solid oxide fuel cell cogeneration system when the external load fails and the input current becomes 0 at the 626th minute. Figure 4 It can be seen that when the external load fails, the temperature of the SOFC stack drops, the temperature of the reformer rises, and the output voltage of the SOFC stack quickly rises to the open circuit voltage, and the change trend of the simulation results is basically consistent with the actual results.

[0038] The above comparison shows that when an air duct failure or an external load failure occurs during the operation of the solid oxide fuel cell cogeneration system, the system reformer temperature, stack temperature or output voltage will change abnormally. The simulation results of the constructed solid oxide fuel cell cogeneration system fault model are basically consistent with the experimental data, which also shows that the constructed solid oxide fuel cell cogeneration system fault model can accurately simulate various faults.

[0039] On this basis, other fault types are simulated, and the output parameter changes of each node are analyzed and summarized. Specifically, for the fuel side pipeline leakage, this embodiment adjusts the fuel flow rate of 8.2L / min during normal operation to 7.3L / min during simulation, and obtains the following Figure 5 The simulation results shown are Figure 5 The simulation results of the fuel stack and reformer when the fuel side pipeline leaks are shown in Figure 2. Figure 5It can be seen that when a fuel side pipeline leak occurs, the stack temperature and reformer temperature drop, and the stack output voltage drops; similar to the air side pipeline leak, in the actual simulation process, the fuel leakage can be increased arbitrarily, or even completely leaked, but when the leakage reaches a certain level, the system cannot operate normally. In the simulation process, when the fuel volume is reduced to 6.3L / min, the reformer temperature has dropped to about 780℃, but in actual operation, the system will not wait until the reformer temperature drops to 780℃ before discovering the problem and performing maintenance; When the fuel side pipeline and the air side pipeline leak at the same time, this embodiment sets the leakage amount of the fuel side pipeline and the air side pipeline to 10% of the normal amount during simulation, and obtains the following Figure 6 The simulation results shown are Figure 6 This is the simulation result of the stack and reformer when the fuel side pipeline and the air side pipeline leak at the same time. Figure 6 It can be seen from the figure that when simultaneous leakage occurs, the temperature of the SOFC stack will first decrease and then increase, but the overall temperature decreases, while the reformer temperature increases, and the output voltage of the SOFC stack will first decrease and then increase, but the overall output voltage decreases; For the heat exchanger rupture failure, this embodiment performs simulation by adjusting the failure coefficient of the heat exchanger failure, and the failure coefficient can take values ​​between 0 and 1. However, in the actual simulation process, for the heat exchanger heat pipe failure, when the failure coefficient is 0.3, the output voltage of the SOFC stack has dropped to about 20V, and the system can no longer work normally; for the heat exchanger cold pipe failure, when the failure coefficient is 0.35, the temperature of the SOFC stack has exceeded 1000°C, and the system can no longer work normally; therefore, during the simulation process, the failure coefficient of the heat exchanger failure is preferably set within the range of 0-0.3. This embodiment sets the failure coefficient when a heat exchanger heat pipe failure occurs to 0.15, and the failure coefficient when a heat exchanger cold pipe failure occurs to 0.2, and obtains the following respectively. Figure 7 , Figure 8 The simulation results are shown. Figure 7 This is the simulation result of the stack when the heat pipe of the heat exchanger fails. Figure 7 It can be seen that the stack temperature and the stack cathode inlet air temperature both decrease, and the stack output voltage decreases; Figure 8 This is the simulation result of the stack when the heat exchanger cold pipe fails. Figure 8 It can be seen that the stack temperature and the stack cathode inlet air temperature both increase, and the stack output voltage increases; As for the reformer carbon deposition fault, it was found in the simulation process that the reformer carbon deposition fault occurs slowly and gradually occurs as the system operation time increases. In actual operation, it may take hundreds or even thousands of hours for carbon deposition to appear. In order to study the reaction of the system after carbon deposition, this embodiment speeds up the reformer carbon deposition speed during the simulation. At the 2000th second of the simulation, the reforming catalyst reaction area is reduced by 20%, resulting in carbon deposition in the reformer. The simulation results show that Fig. 9 The simulation results are shown. Fig. 9 The simulation results of the reformer and stack when the reformer carbon deposition failure occurs are shown in Figure 2. Fig. 9 It can be seen that: the gas pressure at the reformer outlet increases, and the stack output voltage decreases; For the stack electrode delamination failure, this embodiment simulates by reducing the effective reaction area between the anode layer and the electrolyte layer or the cathode layer and the electrolyte layer by 10%, and obtains the following Fig.10 The simulation results are shown. Fig.10 The simulation results of the stack and reformer when the electrode stratification failure occurs are shown in Figure 2. Fig.10 It can be seen from the figure that when electrode stratification failure occurs, the stack temperature and the reformer temperature fluctuate, the stack temperature drops, the reformer temperature rises, and the stack output voltage decreases.

[0040] By simulating different fault types, we can summarize the change rules of the output parameters of each component when different fault types occur. During the actual operation of the solid oxide fuel cell cogeneration system, its actual output parameters can be compared with the output parameters under normal operating conditions and different faults to determine whether the actual solid oxide fuel cell cogeneration system has a fault and the type of fault that has occurred.

[0041] It should be noted that the parts not described in this embodiment are obtained by using existing technologies.

[0042] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for predicting faults in a solid oxide fuel cell cogeneration system, characterized in that: Includes steps: (1) According to the structural composition of the fuel cell cogeneration system, finite element sub-models of the heat exchanger components, reformer components, combustion chamber components, SOFC stack components, and external load components are established respectively; (2) According to the process flow of the fuel cell cogeneration system, the finite element sub-models of the components in step (1) are used as different nodes to build a finite element model of the fuel cell cogeneration system, and the model is debugged and corrected so that the difference between the output parameters of each node of the model under normal operating conditions and the output parameters of each node under actual normal operating conditions is within a preset range; (3) Analyze the main fault types existing in the fuel cell cogeneration system and establish corresponding fault models; (4) Using the finite element model of the fuel cell cogeneration system corrected in step (2), respectively running one of the fault models in step (3) to obtain output parameters of each node under different fault types, and comparing them with the output parameters of each node under actual operating conditions to analyze the impact of different fault types on the system operating state; (5) Based on the output parameters under normal operating conditions and when different fault types occur, the output parameters of the fuel cell cogeneration system under a certain actual operating condition are analyzed and compared to determine whether the system has a fault under the actual operating condition and the corresponding fault type.

2. A method for predicting faults in a solid oxide fuel cell cogeneration system according to claim 1, characterized in that: The main types of faults in the fuel cell cogeneration system in step (3) include: feed pipe leakage fault, heat exchanger pipe rupture fault, reformer carbon deposition fault, stack electrode stratification fault, and external load fault.

3. A method for predicting faults in a solid oxide fuel cell cogeneration system according to claim 2, characterized in that: The feed pipeline leakage fault model established in step (3) is: ； When simulating the air side pipe leakage fault, set: , ; When simulating the fuel side pipeline leakage fault, set: , ; When simulating the simultaneous leakage of fuel and air side pipelines, set: , ; In the formula, is the gas flow rate at the air side pipeline outlet, is the gas flow rate at the air side pipe inlet, is the gas flow rate at the outlet of the fuel side pipeline, is the gas flow rate at the fuel side pipeline inlet, is the gas leakage flow rate in the air side pipeline, is the gas leakage flow rate of the fuel side pipeline.

4. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 2, characterized in that: The heat exchanger pipe rupture fault model established in step (3) is: ； In the formula, is the flow rate of the fluid at the heat exchanger outlet, is the flow rate of the fluid at the heat exchanger inlet, is the pressure at the heat exchanger outlet, is the pressure at the heat exchanger inlet, is the failure coefficient of heat exchanger rupture failure, and .

5. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 2, characterized in that: When establishing the reformer fault model in step (3), the model is built by reducing the reforming efficiency of the reformer.

6. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 5, characterized in that: When establishing the reformer fault model in step (3), the reforming efficiency of the reformer is reduced by reducing the reaction area of ​​the reforming catalyst inside the reformer.

7. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 2, characterized in that: When establishing the stack electrode delamination failure model in step (3), the model is built by reducing the effective reaction area parameter between two adjacent layers.

8. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 2, characterized in that: When establishing the external load fault model in step (3), the model is built by reducing the input current of the external load.

9. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 1, characterized in that: The output parameters in steps (2), (3) and (5) include temperature and / or pressure and / or flow.

10. A method for predicting faults in a solid oxide fuel cell combined heat and power system according to claim 2, characterized in that: In the step (4), when a feed pipeline leakage fault occurs, if the fuel side pipeline leaks, the temperature of the SOFC stack, the reformer, and the combustion chamber decreases, and the output voltage of the SOFC stack decreases; if the air side pipeline leaks, the temperature of the SOFC stack, the combustion chamber, and the reformer increases, and the output voltage of the SOFC stack increases; if the fuel side and air side pipelines leak at the same time, according to the leakage degree of the fuel side and air side pipelines, if the leakage degree of the fuel side and air side pipelines is the same, the SOFC stack will first decrease and then increase, the overall temperature will decrease, the reformer temperature will increase, the SOFC stack output voltage will first decrease and then increase, and the overall output voltage will decrease; When a heat exchanger pipe rupture occurs, if the heat exchanger hot gas pipe ruptures, the SOFC stack temperature drops and the SOFC stack output voltage decreases; if the heat exchanger cold gas pipe ruptures, the SOFC stack temperature continues to rise and the SOFC stack output voltage increases; if the heat exchanger hot gas and cold gas pipes rupture at the same time, the heat exchanger will produce local overcooling or overheating conditions; When a reformer carbon deposition failure occurs, the SOFC stack output voltage decreases, the internal pressure of the reformer increases, and the local temperature of the reformer increases; When a stack electrode stratification failure occurs, the SOFC stack output voltage decreases, and the SOFC stack temperature and reformer temperature fluctuate; When an external load fault occurs, the input current is 0, the output voltage of the SOFC stack will quickly rise to the open circuit voltage, the temperature of the SOFC stack will drop, and the temperature of the reformer will rise.

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