Failure simulation method for fuel cell system under aviation application

Abstract

The invention discloses a failure simulation method of a proton exchange membrane fuel cell system under aviation application. The method comprises the following steps: determining aviation environment variables; establishing an influence transfer function of the aviation environment on the C-type component of the fuel cell; establishing an influence transfer function of the performance of the C-type component on the performance of the cell stack; establishing a relation between the performance of the DC-DC transformer and the performance of the C-type component and the performance of the cell stack; and determining a failure standard and judging whether the fuel cell system fails or not, and establishing an influence transfer function of the aviation external environment on the performance of the fuel cell system. According to the method, the possible failure of the proton exchange membrane fuel cell system is quickly and accurately simulated under the aviation application scene, the reliability of the fuel cell system in the design and manufacturing process is strictly controlled, and support is provided for the application of the fuel cell system in the aviation field.

Description

Technical Field

[0001] The invention belongs to the field of aviation and relates to a fuel cell system failure simulation method under aviation application. Background Art

[0002] The proton exchange membrane fuel cell (PEMFC) is an energy conversion device that directly generates energy from hydrogen and oxygen through an electrochemical reaction. It has great potential in the electrification process of aircraft due to its clean and efficient characteristics.

[0003] Fuel cell systems are highly complex and involve multiple subsystems working together. Generally, the subsystems can be divided into key components such as gas supply system, temperature control system, battery stack, DC-DC transformer, etc. The degradation and failure of any component may affect the final performance output. In practical applications, most components of fuel cell systems have been verified and applied in other industries, which provides a certain reference for their application in the aviation field. Therefore, a comprehensive evaluation of the fuel cell system can be carried out from the equipment level.

[0004] At the same time, in the aviation field, the safety and reliability of equipment are extremely high. Under its stringent safety requirements, simulation of whether the fuel cell system fails in a specific aviation environment is essential, which helps to strictly control the reliability of the fuel cell system during the design and manufacturing process and provide support for its application in the aviation field. Determining its performance degradation in a specific scenario through failure simulation carried out in the design stage is the premise and basis for its application in the aviation environment. Summary of the invention

[0005] The purpose of the present invention is to provide a method for simulating failure of a fuel cell system under aviation application, so as to quickly and accurately simulate possible failures of a proton exchange membrane fuel cell system under aviation application scenarios.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A failure simulation method for a proton exchange membrane fuel cell system in aviation applications based on a component level includes the following steps:

[0008] Step 1: Identify aviation environmental variables.

[0009] Establish the environment set E under typical operating conditions of aircraft operation = {E 1 ,E 2 ,E 3 ...E n}. Each E i Represents different types of aviation environments, such as temperature, pressure, humidity, tilt, vibration, acceleration, etc.

[0010] Step 2: Establish the transfer function of the impact of the aviation environment on the C-type components of the fuel cell.

[0011] 2.1 The proton exchange membrane battery stack is regarded as the core energy conversion component of the proton exchange membrane fuel cell system, defined as a Class A component, which is the source of electrical energy; the DC-DC transformer is regarded as a key component of energy management, defined as a Class B component, which is used to achieve effective distribution and optimization of electrical energy; the remaining components are regarded as auxiliary components, defined as Class C components, the purpose of which is to provide a suitable operating environment for the battery stack. This step needs to establish the transfer function of the environmental set's impact on the performance of Class C components;

[0012] 2.2 The performance of Class C components is defined as Per C = {P 1 ,P 2 ,P 3 ...P n}, where each P i Represents the performance of a Class C component, including the temperature, pressure, humidity and other signals it provides to the battery stack, which are all affected by the environmental set. According to their basic working principles, the performance P i0 It can be expressed by formula (1):

[0013] P i0 =f(E 1 ,E 2 ,E 3 ...E n ) (1)

[0014] 2.3 For each C-type component, when some parameters in the environment set E exceed their normal operating range (Base), the performance of the fuel cell will be limited or affected by the maximum operating capacity. This impact is defined as eff E , which can be calculated by formula (2):

[0015]

[0016] At this time, the performance definition of type C components can be calculated by formula (3), and its main purpose is to control the boundary conditions of the battery stack.

[0017] P i =f(E 1 ,E 2 ,E 3 ...E n )·eff E (3)

[0018] Step 3: Establish the transfer function of the impact of the performance of Class C components on the performance of the battery stack.

[0019] 3.1 The basic working principle of a fuel cell stack is that hydrogen and oxygen undergo a redox reaction to generate electrical energy and thermal energy. The overall reaction formula can be expressed as:

[0020]

[0021] Its electric energy value can represent the performance output Per of the fuel cell stack under certain conditions. A , which consists of a given current value I and a corresponding generated voltage value V stack Calculated. V stack is the theoretical voltage V nernst , activation loss V act 、Ohm loss V ohmic , concentration loss V conc The function can be calculated by formula (5):

[0022] V stack =V nernst -V act -V ohmic -V conc (5)

[0023] 3.2 Theoretical voltage V nernst In the ideal case when no heat is generated, at a certain stack temperature T st and gas pressure The theoretical value that can be generated is:

[0024]

[0025] 3.3 Activation loss V act The energy loss is caused by the activation energy barrier of the electrode reaction, which is usually controlled by the reaction kinetics on the electrode surface. In addition to the design parameters of the fuel cell, it is mainly affected by T st And the I influence, that is:

[0026] V act =f(T st ,I) (7)

[0027] 3.4 ohm loss V ohmic is the voltage loss due to the resistance R of the electrolyte and electrode materials, where

[0028]

[0029] σ=f(T st ,RH) (9)

[0030] Where T mem is the temperature of the proton exchange membrane, σ is the conductivity of the membrane, which is related to T st , relative humidity RH. So it can be written as:

[0031] V ohmic =f(T mem ,T st ,RH) (10)

[0032] 3.5 Concentration loss V conc Energy loss due to the decrease in reactant concentration. Due to the limitation of diffusion effect, if the consumption rate of reactants exceeds the rate of their replenishment in the electrolyte, it will lead to a decrease in concentration and voltage loss. It is usually related to T st Related to I, it can be written as:

[0033] V conc =f(T st ,I) (11)

[0034] 3.6 Therefore, the performance output of the proton exchange membrane fuel cell stack Per A It can be calculated by the formula:

[0035]

[0036] Where T st and T mem The heat flow Q is controlled by the temperature control system, and I is controlled by the system control strategy. Therefore, equation (12) can be rewritten as:

[0037]

[0038] The independent variables on the right are all included in the Per formed in step 2 C middle.

[0039] Step 4: Establish the performance relationship between the DC-DC converter and the C-type components and battery stack

[0040] The DC-DC transformer will change the duty cycle D according to the demand, thereby adjusting the Per A The voltage signal in is converted to the required value, that is,

[0041]

[0042] At the same time, V DC It will also supply power to the C-type components. Therefore, when it is in an abnormal working state, it will also affect the performance of the C-type components. At this time, the performance of the C-type components is calculated by the formula:

[0043] P i =f(E 1 ,E 2 ,E 3 ...E n )·eff E ·eff DC (15)

[0044] The remaining power is delivered to the load as the output of the DC-DC and fuel cell system. sys ,Right now

[0045]

[0046] Step 5: Determine failure criteria and determine failure

[0047] The performance output of the proton exchange membrane fuel cell system under the designed working environment is Per base As a standard, set the failure standard ineff stand , calculate Per sys and Per base The ratio of ineff stand Compare and judge whether it is invalid at this time, that is,

[0048]

[0049] At the same time, after considering the time t, the failure situation within a certain period of time can be obtained. base and Per sys The size and mean of the difference can be further used to obtain the current failure severity.

[0050] After completing the above steps, we can establish the transfer function of the impact of the external aviation environment on the performance of the fuel cell system, and based on the failure criteria, we can complete the construction of the fuel cell system failure simulation model for aviation applications.

[0051] The beneficial effects of the present invention are:

[0052] The present invention simulates whether the fuel cell system fails in a specific aviation environment, which helps to strictly control the reliability of the fuel cell system during the design and manufacturing process, and provides support for its application in the aviation field. Rapid and accurate simulation of possible failures of proton exchange membrane fuel cell systems in aviation application scenarios, and determining the performance degradation in specific scenarios through failure simulations carried out in the design phase, is the premise and basis for its application in aviation environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a flow chart of a method for simulating failure of a fuel cell system in aviation applications.

[0054] Figure 2 This is a schematic diagram of the path of environmental impact on the output of the fuel cell system. DETAILED DESCRIPTION

[0055] A fuel cell system failure simulation method for aviation applications builds a proton exchange membrane fuel cell system failure model to determine the failure of the proton exchange membrane fuel cell system. The proton exchange membrane fuel cell system includes a battery stack component, a DC-DC transformer component, and an auxiliary device component. Consider the possible failure conditions of the system caused by temperature, pressure, and humidity. The flow chart is as follows Figure 1 The method for building a fuel cell system failure simulation model for aviation applications is as follows:

[0056] Step 1: Establish the environment set E = {T, P, RH} under typical operating conditions of the aircraft, where T represents the ambient temperature, P represents the ambient pressure, and RH represents the ambient humidity.

[0057] Step 2: Establish the transfer function of the impact of the aviation environment on the compressor, humidifier, and radiator components.

[0058] The battery stack is defined as a Class A component, the DC-DC transformer is defined as a Class B component, and the air compressor, humidifier, and heat sink are defined as Class C components. This step establishes the output performance Per of the aviation environment E for Class C components. C The influence transfer function.

[0059] 2.1 Air compressor output P com The air temperature T air_out and pressure P air_out , as shown in formula (18), which can be controlled by the pressure ratio π of the air compressor and is affected by T and P.

[0060]

[0061] 2.2 Humidifier output P Hum is the relative humidity RH of the air out and water vapor partial pressure P H2O , as shown in formula (19), which is the mass flow rate M of water added to the air water_in Control, affected by the relative humidity RH, P and T of the environment.

[0062]

[0063] 2.3 Radiator output P Radi is the heat dissipation q between the battery stack and the external environment, thus affecting the battery stack temperature T st As shown in formula (20), it is controlled by the heat transfer coefficient h between the battery stack and the external environment and is affected by the ambient temperature T.

[0064] q=h(T st -T) (20)

[0065] 2.4 For the above three C-type components, when some parameters in the environment set E exceed their normal operating range (Base), they will often be affected by π, M water_in The value range of h is limited, and its actual working ability is affected. This influence is defined as eff E ; Among them, the air compressor and the radiator are powered by a DC-DC transformer. When the transformer is not in operation, its operation may be affected to a certain extent. This effect is defined as eff DC , at this time, Per C It can be calculated by formula (21), and its output provides certain boundary conditions for the battery stack.

[0066] Per C (P com ,P Hum ,P Radi )=f(E)·eff E ·eff DC (twenty one)

[0067] Step 3: Establish the transfer function of the impact of the performance of Class C components on the performance of the battery stack.

[0068] 3.1 The basic working principle of a fuel cell stack is that hydrogen and oxygen undergo a redox reaction to generate electrical energy and thermal energy. The overall reaction formula can be expressed as:

[0069]

[0070] Its electric energy value can represent the performance output Per of the fuel cell stack under certain conditions. A , which consists of a given current value I and a corresponding generated voltage value V stack Calculated. V stack is the theoretical voltage V nernst , activation loss V act 、Ohm loss V ohmic , concentration loss V conc The function can be calculated by formula (5):

[0071] V stack =V nernst -V act -V ohmic -V conc (twenty three)

[0072] 3.2 Theoretical voltage V nernst In the ideal case when no heat is generated, at a certain stack temperature T st and gas pressure The theoretical value that can be generated can be calculated by formula (24):

[0073]

[0074] 3.3 Activation loss V act The energy loss is caused by the activation energy barrier of the electrode reaction, which is usually controlled by the reaction kinetics on the electrode surface. In addition to the design parameters of the fuel cell, it is mainly affected by T st The influence of I and I can be calculated by the formula:

[0075]

[0076] 3.4 ohm loss V ohmic is the voltage loss due to the resistance R of the electrolyte and electrode materials, where

[0077]

[0078] σ=f(T st ,RH) (27)

[0079] Where T mem is the temperature of the proton exchange membrane, σ is the conductivity of the membrane, which is related to T st , relative humidity RH. So it can be written as:

[0080] V ohmic =f(T mem ,T st ,RH) (28)

[0081] 3.5 Concentration loss V conc Energy loss due to the decrease in reactant concentration. Due to the limitation of diffusion effect, if the consumption rate of reactants exceeds the rate of their replenishment in the electrolyte, it will lead to a decrease in concentration and voltage loss. It is usually related to T st Related to I, it can be written as:

[0082]

[0083] 3.6 Therefore, the performance output of the proton exchange membrane fuel cell stack Per A It can be calculated by the formula:

[0084]

[0085] Where T st and T mem The heat flow q is controlled by the temperature control system, and I is controlled by the input command and control strategy. Therefore, equation (12) can be rewritten as:

[0086]

[0087] The independent variables on the right are all included in the Per formed in step 2 C (Pcom ,P Hum ,P Radi )middle.

[0088] Step 4: Establish the performance relationship between the DC-DC converter and the C-type components and battery stack

[0089] The DC-DC converter receives the current and voltage from the battery stack and distributes it to the high-voltage power supply circuit in the fuel cell system and the external load in proportion to the demand. A The voltage signal in is converted to the required value, that is,

[0090]

[0091] The current and voltage supplied to the load are the output Per of the DC-DC transformer. B (V load ,I load ), which is also the output Per of the entire fuel cell system sys .Per sys ,Per A ,Per B ,Per C The relationship between E is shown in formula (33). sys The impact path is as follows Figure 2 shown.

[0092]

[0093] Step 5: Determine failure criteria and determine failure

[0094] The performance output of the proton exchange membrane fuel cell system at 25 degrees Celsius, 1 standard atmosphere, and 50% relative humidity is Per base As a standard, set the failure standard ineff stand is 80%, calculate Per sys and Per base The ratio of ineff stand Compare and determine whether the working state is failed or not, that is,

[0095]

[0096] At the same time, by considering the time t, that is, the dynamic performance of the fuel cell system, the failure of the fuel cell system within a certain period of time can be obtained. base and Per sys The size and mean of the difference can be further used to obtain the current failure severity.

[0097] The present invention conducts rapid and accurate simulation of possible failures of proton exchange membrane fuel cell systems in aviation application scenarios, which helps to strictly control the reliability of fuel cell systems during the design and manufacturing process and provide support for their application in the aviation field.

Claims

1. A method for simulating failure of a fuel cell system in aviation applications, characterized in that: The following steps are involved: Step 1: Determine the aviation environment variables; establish the environment set E = {E1, E2, E3...E n }, where each E i Represents different types of aviation environments, including temperature, pressure, humidity, tilt, vibration, acceleration; Step 2: Establish the transfer function of the impact of the aviation environment on the C-type components of the fuel cell; 2.1 The proton exchange membrane battery stack is regarded as the core energy conversion component of the proton exchange membrane fuel cell system, defined as a Class A component, which is the source of electrical energy; The DC-DC transformer is regarded as a key component of energy management and is defined as a Class B component, which is used to achieve efficient distribution and optimization of electrical energy; The remaining components are considered auxiliary components, defined as Class C components, which provide a suitable operating environment for the battery stack; 2.2 The performance of Class C components is defined as Per C = {P1,P2,P3...P n }, where each P i Represents the performance of a Class C component, including the temperature, pressure, and humidity signals it provides to the battery stack, which are all affected by the environmental set. i0 It is expressed by formula (1): P i0 =f(E1,E2,E3...E n ) (1) 2.3 For each C-type component, when some parameters in the environment set E exceed their normal operating range Base, the performance of the fuel cell is limited or affected by the maximum operating capacity. This impact is defined as eff E , calculated by formula (2): At this time, the performance definition of the C-type component is calculated by formula (3), the purpose of which is to control the boundary conditions of the battery stack; P i =f(E1,E2,E3...E n )·eff E (3) Step 3: Establish the transfer function of the impact of the performance of type C components on the performance of the battery stack; 3.1 The working principle of the fuel cell stack is that hydrogen and oxygen undergo a redox reaction to generate electrical energy and thermal energy. The overall reaction formula is: The electrical energy value represents the performance output Per of the fuel cell stack. A , which consists of a given current value I and a corresponding generated voltage value V stack Calculated, V stack is the theoretical voltage V nernst , activation loss V act 、Ohm loss V ohmic , concentration loss V conc The function is calculated by formula (5): V stack =V nernst -V act -V ohmic -V conc (5) 3.2 Theoretical voltage V nernst In the ideal case when no heat is generated, at a certain stack temperature T st and gas pressure The theoretical value that can be generated is: 3.3 Activation loss V act It is the energy loss caused by the activation energy barrier of the electrode reaction, which is controlled by the reaction kinetics on the electrode surface and is affected by T st And the I influence, that is: V act =f(T st ,I) (7) 3.4 ohm loss V ohmic is the voltage loss due to the resistance R of the electrolyte and electrode materials, where σ=f(T st ,HR) (9) Where T mem is the temperature of the proton exchange membrane, σ is the conductivity of the membrane, RH is the relative humidity, V ohmic =f(T mem ,T st ,RH) (10) 3.5 Concentration loss V conc Energy loss caused by the decrease in reactant concentration. Due to the limitation of diffusion effect, if the consumption rate of reactants exceeds the rate of their replenishment in the electrolyte, it will lead to a decrease in concentration and voltage loss, which is usually related to T st Related to I, written as: V conc =f(T st ,I) (11) 3.6 Therefore, the performance output of the proton exchange membrane fuel cell stack Per A Calculated by the following formula: Where T st and T mem The heat flow Q is controlled by the temperature control system, and I is controlled by the system control strategy, so equation (12) is rewritten as: The independent variables on the right are all included in the Per formed in step 2 C middle; Step 4: Establish the performance relationship between the DC-DC transformer and the C-type components and the battery stack; The DC-DC transformer changes the duty cycle D according to the demand, thereby adjusting the Per A The voltage signal in is converted to the required value, that is, At the same time, V DC Power is supplied to the C-type components, so when it is in an abnormal working state, the performance of the C-type components is affected. At this time, the performance of the C-type components is calculated by the formula: P i =f(E1,E2,E3...E n )·eff E ·eff DC (15) The remaining power is delivered to the load as the output of the DC-DC and fuel cell system. sys ,Right now Step 5: Determine the failure criteria and judge the failure; The performance output of the proton exchange membrane fuel cell system under the designed working environment is Per base As a standard, set the failure standard ineff stand , calculate Per sys and Per base The ratio of ineff stand Compare and judge whether it is invalid at this time, that is, After completing the above steps, we can establish the transfer function of the impact of the external aviation environment on the performance of the fuel cell system, and based on the failure criteria, we can complete the construction of the fuel cell system failure simulation model for aviation applications.

2. The method for simulating failure of a fuel cell system in aviation applications according to claim 1, characterized in that: In step 1, an environment set E = {T, P, RH} under typical operating conditions of the aircraft is established, where T represents the ambient temperature, P represents the ambient pressure, and RH represents the ambient humidity.

3. The method for simulating failure of a fuel cell system in aviation applications according to claim 1, characterized in that: In step 2, the air compressor, humidifier, and heat sink are defined as Class C components; Air compressor output P com The air temperature T air_out and pressure P air_out , as shown in formula (18), which is controlled by the pressure ratio π of the air compressor and is affected by T and P; Humidifier output P Hum is the relative humidity RH of the air out and water vapor partial pressure P H2O , as shown in formula (19), which is determined by the mass flow rate M of water added to the air water_in Control, affected by the relative humidity RH, P and T of the environment, Radiator output P Radi is the heat dissipation q between the battery stack and the external environment, thus affecting the battery stack temperature T st , as shown in formula (20), which is controlled by the heat transfer coefficient h between the battery stack and the external environment and is affected by the ambient temperature T; q=h(T st -T) (20)。 4. The method for simulating failure of a fuel cell system for aviation applications according to claim 1, characterized in that: In step 5, the performance output Per of the proton exchange membrane fuel cell system under the conditions of 25 degrees Celsius, 1 standard atmospheric pressure, and 50% relative humidity is base As a standard, set the failure standard ineff stand is 80%, calculate Per sys and Per base The ratio of ineff stand Compare and determine whether there is failure in this working state.

5. The method for simulating failure of a fuel cell system for aviation applications according to claim 1, characterized in that: In step 5, after adding the factor of time t, the failure situation within a certain period of time is obtained, and the Per base and Per sys The size and mean of the difference can be used to obtain the current failure severity.

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