CN118431517A - Blocking diagnosis method for fuel cell air system - Google Patents

Abstract

The invention provides a blocking diagnosis method for an air system of a fuel cell, which belongs to the technical field of fuel cells, and comprises a blocking diagnosis method for an air system at the front end of a galvanic pile and a blocking diagnosis method for an air system at the rear end of the galvanic pile, wherein the front end blocking diagnosis method mainly comprises the steps of judging whether the deviation between the rotating speed of an actual air compressor and the rotating speed of a corrected air compressor is larger than a first threshold value or not and judging whether the air compressor is in surge or not; the rear end blockage judging method mainly comprises the steps of judging whether the deviation between the actual opening of the pressure regulating valve and the calibrated opening is larger than a second threshold value or not and judging whether the current air flow and the current pressure meet the working condition requirements or not. The method provided by the invention can be used for effectively and rapidly diagnosing whether the air system of the fuel cell system is blocked or not, and other additional auxiliary components are not needed, so that the diagnosis method is simple, rapid and efficient.

Description

A blockage diagnosis method for fuel cell air system

Technical Field

The present invention relates to the technical field of fuel cells, and more particularly to a blockage diagnosis method for a fuel cell air system.

Background technique

Proton exchange membrane fuel cells (PEMFC) are being vigorously developed as a new type of power device due to their advantages such as high system efficiency, low noise, zero emissions, and low-temperature cold start. Especially in the field of vehicle applications, fuel cell power systems are considered to be one of the greenest solutions for future vehicles. The proton exchange membrane fuel cell itself is a device that converts hydrogen and oxygen into electrical energy through the electrochemical reaction. Hydrogen undergoes an oxidation reaction in the anode catalyst to generate hydrogen ions and electrons. The hydrogen ions pass through the proton exchange membrane to reach the surface of the cathode catalyst layer. The transfer process requires carrying water for transmission and reacting with oxygen and the electrons generated at the anode through an external circuit to reach the cathode for reduction reaction to generate electrical energy. The heat generated during the reaction is taken away by the internal circulation of the coolant, and the optimal operating temperature of the fuel cell stack is generally around 60~80℃.

The normal operation of the fuel cell stack requires coordination with external auxiliary systems to ensure that the fuel cell stack can generate electricity continuously and stably. The general fuel cell system includes a fuel cell stack, a fuel cell air subsystem, a fuel cell hydrogen subsystem, a fuel cell cooling subsystem, a fuel cell electrical subsystem, and a fuel cell control system. The hydrogen subsystem and the air subsystem provide reactants for the fuel cell stack, and the cooling system ensures the stable operation of the stack. However, during the operation of the fuel cell system, the components and pipelines of the air system may be blocked due to system diagnosis or during the installation process. When there is a blockage between the front end of the stack and the air compressor, the air flow entering the stack will be reduced, which will cause the output performance of the stack to decrease. In severe cases, the stack will be irreversibly attenuated; in addition, when the tail end of the rear end of the stack is blocked, the air inlet pressure of the stack will continue to increase. Excessive pressure will cause irreversible damage to the internal structure of the stack. Both will eventually reduce the service life of the fuel cell system and affect the power generation state of the system. There is no method for diagnosing the blockage of the fuel cell air system in the existing technology.

Summary of the invention

The present invention provides a blockage diagnosis method for a fuel cell air system, so as to solve the problem that the prior art cannot judge the blockage of the air system.

In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a method for diagnosing blockage of a fuel cell air system, the method comprising a method for diagnosing blockage of a front-end air system of a fuel cell stack and a method for diagnosing blockage of a rear-end air system of a fuel cell stack, the method for diagnosing blockage of a front-end air system of a fuel cell stack comprising the following steps:

Step S11, the system is running stably and the air system stack front end blockage diagnosis instruction is activated;

Step S12, obtaining the air compressor speed and ambient temperature corresponding to the system operating conditions;

Step S13, judging whether the deviation between the actual operating air compressor speed and the corrected air compressor speed at the reference ambient temperature of 25° C. under the operating condition is greater than the set first threshold, if yes, go to step S14, otherwise go to step S11;

Step S14, determining whether the actual feedback speed of the air compressor is greater than or equal to the maximum operating speed of the air compressor, if yes, go to step S18, otherwise go to step S15;

Step S15, determining whether air compressor surge is triggered, if yes, go to step S20, otherwise go to step S16;

Step S16, obtaining the current air flow and pressure and determining whether they meet the target flow and pressure requirements under the current operating conditions, if yes, proceed to step S17, otherwise proceed to step S18;

Step S17, prompting that the front end of the battery stack is blocked and needs to be repaired;

Step S18, reduce the system output power, and go to step S19;

Step S19, determine whether the current set power of the system is less than the minimum output power of the system, if yes, go to step S20, otherwise go to step S11;

Step S20: Shut down the system to solve the problem of blockage at the front end of the battery stack.

Furthermore, the method for diagnosing blockage in the air system at the rear end of the fuel cell stack comprises the following steps:

Step S21, the system is running stably and the air system stack rear end blockage diagnosis instruction is activated;

Step S22, obtaining the opening of the pressure regulating valve corresponding to the operating condition;

Step S23, judging whether the deviation between the actual feedback opening of the pressure regulating valve and the calibrated opening of the pressure regulating valve is greater than a preset second threshold value, if yes, go to step S24, otherwise go to step S21;

Step S24, judging whether the actual feedback opening of the pressure regulating valve is greater than the maximum opening value, if yes, go to step S27, otherwise go to step S25;

Step S25, obtaining the current air flow and pressure and determining whether they meet the target flow and pressure requirements under the current operating conditions, if yes, proceed to step S26, otherwise proceed to step S27;

Step S26, prompting that the rear end of the stack is blocked and needs to be repaired;

Step S27, reduce the system output power, and go to step S28;

Step S28, determine whether the system setting power is less than the system output minimum power, if yes, go to step S29, otherwise go to step S21;

Step S29: Shut down the system to solve the problem of blockage at the rear end of the fuel cell stack.

Preferably, the first threshold value is 5%-10% of the corrected air compressor speed at the reference ambient temperature of 25° C. under the operating condition.

Preferably, the second threshold value is 20%-25% of the calibrated opening of the pressure regulating valve.

Preferably, the calculation formula for the corrected air compressor speed at the reference ambient temperature of 25° C. under the operating condition is as follows: , wherein _Ncorrection is the corrected air compressor speed at the reference ambient temperature of 25°C calibrated under various operating conditions of the fuel cell system, _NRef is the reference speed at the calibrated corrected speed of 25°C and 1atm, the actual ambient temperature is T, and the reference temperature is _TRef .

Compared with the prior art, the advantages and positive effects of the present invention are:

Based on two discoveries during the operation of the fuel cell system: if a blockage occurs between the air compressor and the inlet of the fuel cell stack, the operating speed of the air compressor will be higher than the preset speed of the corresponding operating condition; and if a blockage occurs at the air outlet of the fuel cell stack, the opening of the air pressure regulating valve will be higher than the preset opening of the corresponding operating condition. A blockage diagnosis method for the air system of the present invention is designed, which can effectively and quickly diagnose whether there is a blockage in the air system of the fuel cell system, and does not require other additional auxiliary components. The diagnosis method is simple, fast and efficient.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a structural diagram of a fuel cell system;

FIG2 is a flow chart of a method for diagnosing blockage in a front-end air system of a fuel cell stack according to the present invention;

FIG3 is a flow chart of a method for diagnosing blockage in a fuel cell stack rear-end air system according to the present invention;

FIG4 is a diagram illustrating the change in speed of the air compressor when the front end of the stack is blocked;

Figure 5 is a diagram illustrating the change in the opening of the pressure regulating valve when the rear end of the fuel cell stack is blocked.

Note in the figure:

Fuel cell air system 100, fuel cell stack 200, cooling subsystem 300, hydrogen subsystem 400, controller 500, ambient temperature sensor 101, air filter 102, air flow meter 103, air compressor 104, cooler 105, humidifier 106, air inlet pressure sensor 107, air inlet temperature sensor 108, pressure regulating valve 109, and muffler 110.

Detailed ways

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Embodiment 1: This embodiment provides a blockage diagnosis method for a fuel cell air system. As shown in FIG1 , the fuel cell system is composed of a fuel cell air system 100, a fuel cell stack 200, a cooling subsystem 300, a hydrogen subsystem 400, a controller 500, etc. The fuel cell air system 100 is equipped with an ambient temperature sensor 101, an air filter 102, an air flow meter 103, an air compressor 104, a cooler 105, a humidifier 106, an air inlet pressure sensor 107, an air inlet temperature sensor 108, a pressure regulating valve 109 and a muffler 110. The outside air passing through the air compressor 104 first passes through the air filter 102 to filter out impurities and harmful gases in the gas, and then the air flow meter 103 detects the flow rate entering the fuel cell stack 200 to adjust the air compressor 104. After the air is pressurized by the air compressor 104, the air temperature rises and cannot meet the use requirements of the fuel cell stack 200 for the air temperature. Therefore, the high-temperature air after pressurization passes through the cooler 105 to cool down to the working temperature required by the fuel cell stack 200 for the air, and the air inlet temperature sensor 108 is used to detect the temperature of the air inlet. The air with a certain temperature and pressure passes through the dry side of the humidifier 106 to meet the requirements of the fuel cell stack 200 for air humidity, and then enters the fuel cell stack 200 to work. The remaining wet air passing through the fuel cell stack 200 finally passes through the wet side of the humidifier 106 to humidify the pressurized dry air in the environment, and then passes through the pressure regulating valve 109 to exhaust into the atmosphere. The pressure regulating valve 109 is used to adjust the air inlet pressure of the fuel cell stack 200, and is detected by the air inlet pressure sensor 107; the controller 500 is mainly used to control the air compressor 104 and the pressure regulating valve 109 to work according to the specified instructions, and at the same time obtain the actual operating status of the air compressor 104 and the pressure regulating valve 109. The controller 500 also has a fuel cell air system 100 blockage diagnosis processor, which activates the air system blockage diagnosis instruction according to the operating status of the fuel cell system, and diagnoses online whether the air system is blocked.

As shown in FIG2 , the blockage diagnosis method for a fuel cell air system of this embodiment includes the following steps:

Step S11: When the system is running stably, the blockage diagnosis instruction of the air system at the front end of the fuel cell stack is activated.

Step S12: Obtain the air compressor speed and ambient temperature corresponding to the system operating conditions.

Step S13, determine whether the deviation between the actual operating air compressor speed and the corrected air compressor speed at the reference ambient temperature of 25°C under the operating condition is greater than the set first threshold, otherwise go to step S11, if yes, go to step S14, the first threshold value is 5% of the corrected air compressor speed at the reference ambient temperature of 25°C under the operating condition. Generally, the air compressor speed required for the operation of the fuel cell system is calibrated under a specific environment, and the speed corresponding to the temperature of 25°C and 1atm (101.325kPa ambient pressure) is corrected as the calibrated speed of the system operating condition. The system operating point shown in Figure 4 is the speed corresponding to the system operating point at 25°C and 1atm. The calibrated corresponding speeds under various operating conditions of the fuel cell system are all the speeds corresponding to 25°C and 1atm. When the ambient temperature deviates from 25°C, the calibrated corresponding speeds under various operating conditions of the fuel cell system are all the calibrated corrected speeds ( _Ncorrected ). The calibrated corrected speed is the reference speed (N _Ref ) at 25°C and 1atm multiplied by the actual ambient temperature (T) divided by the 1/2 power of the reference temperature (T _Ref ), and the formula is as follows:

.

Step S14, further determine whether the actual feedback speed of the air compressor is greater than or equal to the maximum operating speed of the air compressor, otherwise go to step S15, if yes, go to step S18. Because the speed of the air compressor will increase after the blockage occurs, when the maximum speed of the air compressor is triggered, the air compressor cannot meet the corresponding working condition operation; as shown in Figure 4, during the operation of the fuel cell, when the air compressor speed is at point D in Figure 4, after the blockage occurs, the speed of the air compressor increases, and it will deviate from point D to point E, at this time exceeding the maximum operating speed of the air compressor and cannot meet normal use.

Step S15, determine whether the air compressor surge is triggered, if yes, go to step S20, otherwise go to step S16. When a blockage occurs at the front end of the stack, especially at the low operating point of the fuel cell stack, the air compressor surge phenomenon is prone to occur. Figure 4 shows that when the system is operating normally, after a slight blockage occurs at point A, point A deviates to point B. At this time, the air compressor surge line has not been triggered. When a more serious blockage occurs, the operating point deviates from point A to point C. At this time, point C is outside the air compressor surge line, causing the air compressor to surge and unable to meet the working state. In Figure 4, the horizontal axis Q represents the air flow rate, and the vertical axis λ represents the air compressor pressure ratio.

Step S16, obtain the current air flow and pressure and determine whether they meet the target flow and pressure requirements under the current operating conditions. If yes, go to step S17, otherwise go to step S18.

Step S17, prompting that the front end of the battery stack is blocked and needs to be repaired.

Step S18, reduce the system output power, and go to step S19.

Step S19, determine whether the current set power of the system is less than the minimum output power of the system, if yes, go to step S20, otherwise go to step S11.

Step S20: Shut down the system to solve the problem of blockage at the front end of the battery stack.

As shown in FIG3 , the method for diagnosing blockage in the air system at the rear end of the stack includes the following steps:

Step S21, the system is running stably and activating the air system stack rear end blockage diagnosis instruction.

Step S22: Obtain the opening of the air pressure regulating valve corresponding to the operating condition.

Step S23, determine whether the deviation between the actual feedback opening of the air pressure regulating valve and the calibrated opening of the air pressure regulating valve is greater than a preset second threshold, if yes, go to step S24, otherwise go to step S21, the second threshold is 20% of the calibrated opening of the pressure regulating valve.

Step S24, determine whether the actual feedback opening of the air pressure regulating valve is greater than the maximum opening value, if yes, go to step S27, otherwise go to step S25. Because the maximum opening of the air pressure regulating valve has certain requirements, adjusting the opening beyond this opening will no longer work on the pressure control. In the implementation process, the maximum opening of the air pressure regulating valve is generally 90%, and it can also be other openings, depending on the characteristics of the air pressure regulating valve itself. In Figure 5, when a slight blockage occurs at the rear end, the air pressure regulating valve deviates from point G at point F, and a more serious blockage occurs at the rear end. The opening of the air pressure regulating valve will deviate to point H, which exceeds the maximum opening of the air pressure regulating valve and cannot be used continuously. In Figure 5, the horizontal axis P represents the air inlet pressure, and the vertical axis W represents the opening of the pressure regulating valve.

Step S25, obtain the current air flow and pressure and determine whether they meet the target flow and pressure requirements under the current operating conditions. If so, go to step S26, otherwise go to step S27. In Figure 5, the standard operating air pressure regulating valve opening is the air pressure regulating valve opening corresponding to each operating condition calibrated during the operation of the system. When blockage occurs, the air pressure regulating valve opening increases and deviates from the corresponding curve of the air pressure regulating valve opening after blockage.

Step S26, prompting that the rear end of the stack is blocked and needs to be repaired.

Step S27, reduce the system output power; generally, when a blockage occurs during the operation of the system, in order to improve the operating state of the system, the system power output is reduced to maintain the system running at a certain power instead of directly shutting down the system.

Step S28, determine whether the system setting power is less than the system minimum output power, if yes, go to step S29, otherwise go to step S21.

Step S29: Shut down the system to solve the problem of blockage at the rear end of the fuel cell stack.

Example 2: This example provides a method for diagnosing a blockage in a fuel cell air system, which includes a method for diagnosing a blockage in the front-end air system of the fuel cell stack with the same steps as in Example 1 and a method for diagnosing a blockage in the rear-end air system of the fuel cell stack with the same steps as in Example 1. This example differs from Example 1 only in that: the first threshold value is 8% of the corrected air compressor speed at the reference ambient temperature of 25°C under the operating condition; the second threshold value is 23% of the calibrated opening of the pressure regulating valve.

Example 3: This example provides a method for diagnosing a blockage in a fuel cell air system, which includes a method for diagnosing a blockage in the front-end air system of the fuel cell stack with the same steps as in Example 1 and a method for diagnosing a blockage in the rear-end air system of the fuel cell stack with the same steps as in Example 1. This example differs from Examples 1 and 2 only in that: the first threshold value is 10% of the corrected air compressor speed at the reference ambient temperature of 25°C under the operating condition; the second threshold value is 25% of the calibrated opening of the pressure regulating valve.

The above description is only a preferred embodiment of the present invention and does not limit the present invention in other forms. Any technician familiar with the profession may use the technical content disclosed above to change or modify it into an equivalent embodiment with equivalent changes and apply it to other fields. However, any simple modification, equivalent change and modification made to the above embodiment based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims (5)

1. A method for diagnosing a blockage in a fuel cell air system, characterized in that the method comprises a method for diagnosing a blockage in a front-end air system of a fuel cell stack and a method for diagnosing a blockage in a rear-end air system of a fuel cell stack, wherein the method comprises the following steps: Step S11, the system is running stably and the air system stack front end blockage diagnosis instruction is activated; Step S12, obtaining the air compressor speed and ambient temperature corresponding to the system operating conditions; Step S13, judging whether the deviation between the actual operating air compressor speed and the corrected air compressor speed at the reference ambient temperature of 25° C. under the operating condition is greater than the set first threshold, if yes, go to step S14, otherwise go to step S11; Step S14, determining whether the actual feedback speed of the air compressor is greater than or equal to the maximum operating speed of the air compressor, if yes, go to step S18, otherwise go to step S15; Step S15, determining whether air compressor surge is triggered, if yes, go to step S20, otherwise go to step S16; Step S16, obtaining the current air flow and pressure and determining whether they meet the target flow and pressure requirements under the current operating conditions, if yes, proceed to step S17, otherwise proceed to step S18; Step S17, prompting that the front end of the battery stack is blocked and needs to be repaired; Step S18, reduce the system output power, and go to step S19; Step S19, determine whether the current set power of the system is less than the minimum output power of the system, if yes, go to step S20, otherwise go to step S11; Step S20: Shut down the system to solve the problem of blockage at the front end of the battery stack. 2. The blockage diagnosis method for the fuel cell air system according to claim 1, characterized in that: the blockage diagnosis method for the air system at the rear end of the fuel cell stack comprises the following steps: Step S21, the system is running stably and the air system stack rear end blockage diagnosis instruction is activated; Step S22, obtaining the opening of the pressure regulating valve corresponding to the operating condition; Step S23, judging whether the deviation between the actual feedback opening of the pressure regulating valve and the calibrated opening of the pressure regulating valve is greater than a preset second threshold value, if yes, go to step S24, otherwise go to step S21; Step S24, judging whether the actual feedback opening of the pressure regulating valve is greater than the maximum opening value, if yes, go to step S27, otherwise go to step S25; Step S25, obtaining the current air flow and pressure and determining whether they meet the target flow and pressure requirements under the current operating conditions, if yes, proceed to step S26, otherwise proceed to step S27; Step S26, prompting that the rear end of the stack is blocked and needs to be repaired; Step S27, reduce the system output power, and go to step S28; Step S28, determine whether the system setting power is less than the system output minimum power, if yes, go to step S29, otherwise go to step S21; Step S29: Shut down the system to solve the problem of blockage at the rear end of the fuel cell stack. 3. The blockage diagnosis method for a fuel cell air system according to claim 1 is characterized in that: the first threshold value is 5%-10% of the corrected air compressor speed at a reference ambient temperature of 25°C under operating conditions. 4. The blockage diagnosis method for a fuel cell air system according to claim 2, characterized in that the second threshold value is 20%-25% of the calibrated opening of the pressure regulating valve. 5. The blockage diagnosis method for a fuel cell air system according to claim 1, characterized in that: the calculation formula of the corrected air compressor speed at the reference ambient temperature of 25° C. under the operating condition is as follows: Wherein, _Ncorrection is the corrected air compressor speed at the reference ambient temperature of 25°C calibrated under various operating conditions of the fuel cell system, _NRef is the reference speed at the calibrated corrected speed of 25°C and 1atm, the actual ambient temperature is T, and the reference temperature is _TRef .