Bypass airflow estimation methods, devices, and reactor inlet airflow estimation methods

Abstract

This invention relates to the field of fuel cell engine control technology, specifically to a bypass air flow estimation method, device, and method for estimating inlet air flow. The bypass air flow estimation method includes: acquiring the correspondence between the bypass valve opening, actual pressure ratio, and standardized flow rate; acquiring the bypass valve opening, inlet air pressure, inlet air temperature, and ambient pressure of the target fuel cell's air system; calculating the actual pressure ratio of the bypass valve based on the acquired inlet air pressure and ambient pressure; determining the standardized flow rate of the bypass valve based on the bypass valve opening, actual pressure ratio, and correspondence; determining a correction coefficient based on the inlet air temperature, inlet air pressure, and ambient pressure; and correcting the standardized flow rate using the correction coefficient to obtain the bypass air flow rate of the bypass valve. This method enables the estimation of the bypass air flow rate of the fuel cell air system bypass valve without requiring additional flow meters, thus reducing costs.

Description

Technical Field

[0001] This invention relates to the field of fuel cell engine control technology, specifically to a bypass airflow estimation method, device, and stack airflow estimation method. Background Technology

[0002] Fuel cell vehicles represent a crucial direction for the development of new energy vehicles due to their advantages such as zero emissions, high efficiency, and rapid hydrogen refueling. The power of a fuel cell vehicle is primarily provided by a fuel cell engine, which mainly consists of multiple subsystems including the fuel cell stack, air supply subsystem, water and thermal management subsystem, hydrogen supply subsystem, and DC-DC converter. The fuel cell engine needs to maintain a certain flow rate and pressure at the fuel cell stack. The operating flow rate and pressure of the fuel cell are controlled in a closed loop by adjusting the air compressor speed and the back pressure valve opening.

[0003] In an air system, due to the characteristics of the air compressor, according to the flow-pressure ratio surge curve of the air compressor, when the flow rate and pressure exceed the surge line, the air compressor will experience obvious surge. Specifically, at low speeds, the pressure and flow rate fluctuate periodically, and at high speeds, obvious noise will be heard.

[0004] To achieve surge control in the air system, a bypass valve needs to be added at the inlet. Surge reduces the lifespan of the air compressor and affects the stable power output of the fuel cell engine. However, with the addition of a bypass valve, the inlet flow rate is not equal to the mass flow rate at the air filter because the air system only has a mass flow meter at the air filter. This makes closed-loop control of the inlet air flow rate uncontrollable. An effective method is to add a mass flow meter at the bypass point, but the high temperature of the air compressor outlet gas, coupled with prolonged exposure to high temperature and humidity, will affect the accuracy and stability of the flow meter, and adding a flow meter will increase system costs. Summary of the Invention

[0005] The purpose of this invention is to provide a bypass air flow estimation method, device, and stack air flow estimation method, which can estimate the bypass air flow of the bypass valve of the fuel cell air system without the need for additional flow meters, thus reducing costs.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides a bypass airflow estimation method, which is applied to the air system of a fuel cell, comprising:

[0008] Obtain the correspondence between the bypass valve opening degree, actual pressure ratio, and standardized flow rate;

[0009] Obtain the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the air system of the target fuel cell;

[0010] The actual pressure ratio of the bypass valve is calculated based on the obtained infeed air pressure and ambient pressure. The standardized flow rate of the bypass valve is determined based on the obtained bypass valve opening, the calculated actual pressure ratio of the bypass valve, and the corresponding relationship.

[0011] The correction factor is determined based on the infeed air temperature and infeed air pressure. The correction factor is then used to correct the standardized flow rate to obtain the bypass air flow rate of the bypass valve.

[0012] Furthermore, the correction factors include standard temperature correction factor, standard pressure ratio correction factor, and relative flow ratio correction factor.

[0013] Furthermore, the formula for calculating the standard temperature correction factor is as follows: In the formula: a1 is the standard temperature correction factor, T std T is the standard temperature. up This refers to the temperature of the air entering the reactor.

[0014] Furthermore, the formula for calculating the standard pressure ratio correction factor is as follows: In the formula: a2 is the standard pressure ratio correction coefficient, P std For standard pressure, P up This refers to the infeed air pressure.

[0015] Furthermore, the formula for calculating the relative flow ratio correction coefficient is as follows: In the formula: a3 is the relative flow ratio correction coefficient, P down Due to environmental pressures, P up denoted as the infeed air pressure, and k as the air adiabatic index.

[0016] Furthermore, the bypass air flow rate of the bypass valve The calculation formula is In the formula, For the bypass valve, a1 is the standard temperature correction factor, a2 is the standard pressure ratio correction factor, and a3 is the relative flow ratio correction factor.

[0017] Furthermore, a table showing the correspondence between the bypass valve opening degree, actual pressure ratio, and standardized flow rate was obtained through bypass valve calibration tests.

[0018] Furthermore, the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the air system are acquired through the fuel cell controller.

[0019] Secondly, the present invention provides a bypass airflow estimation device capable of performing the steps of the bypass airflow estimation method described above, including:

[0020] The first acquisition module is used to construct a table showing the correspondence between the opening degree of the bypass valve, the actual pressure ratio, and the standardized flow rate.

[0021] The second acquisition module is used to acquire the bypass valve opening, infeed air pressure, infeed air temperature and ambient pressure of the air system of the target fuel cell.

[0022] The first determining module calculates the actual pressure ratio of the bypass valve based on the acquired infeed air pressure and ambient pressure, and determines the standardized flow rate of the bypass valve based on the acquired bypass valve opening, the calculated actual pressure ratio of the bypass valve, and the corresponding relationship.

[0023] The second determining module determines a correction coefficient based on the infeed air temperature, infeed air pressure and ambient pressure, and uses the correction coefficient to correct the standardized flow rate to obtain the bypass air flow rate of the bypass valve.

[0024] Thirdly, the present invention provides a method for estimating the infeed air flow rate, which is applied to the air system of a fuel cell, comprising:

[0025] Obtain the air filter flow rate and bypass valve operating status of the air system of the target fuel cell;

[0026] When the bypass valve is in the closed state, the inlet air flow rate of the air system of the target fuel cell is the air filter flow rate;

[0027] When the bypass valve is in the open state, the inlet air flow rate of the air system of the target fuel cell is the difference between the air filter flow rate and the bypass air flow rate of the bypass valve, wherein the bypass air flow rate is obtained by the bypass air flow rate estimation method described above.

[0028] The present invention has the following unexpected beneficial effects:

[0029] 1. This invention estimates the infeed air flow rate of a fuel cell air system using a semi-physical empirical model of valves. Specifically, it utilizes the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the target fuel cell air system obtained during actual operation. The standardized flow rate of the bypass valve is obtained through a semi-empirical physical model of the valves, i.e., a table showing the correspondence between the bypass valve opening, actual pressure ratio, and standardized flow rate. Then, a correction coefficient is determined based on the infeed air temperature, infeed air pressure, and ambient pressure. This correction coefficient is used to correct the standardized flow rate, yielding the bypass air flow rate of the bypass valve. On the one hand, obtaining the bypass air flow rate through table lookup and correction eliminates the need for complex calculations; on the other hand, since the relevant data can be directly acquired by the fuel cell controller, there is no need to add an additional mass flow meter, reducing manufacturing costs.

[0030] 2. This invention obtains the infeed air flow rate by combining the air filter flow rate and the bypass valve operating status of the air system of the target fuel cell. By subtracting the bypass flow rate from the air filter flow rate, the infeed air flow rate when the bypass valve is open can be obtained, thereby ensuring closed-loop control of the infeed air flow rate when the bypass valve is open. Attached Figure Description

[0031] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention.

[0032] Figure 1 A schematic flowchart of the bypass airflow estimation method according to an embodiment of the present invention is shown.

[0033] Figure 2 A schematic diagram of the structure of the fuel cell air system according to an embodiment of the present invention is shown.

[0034] Figure 3 A graph of the relative flow ratio coefficient described in an embodiment of the present invention is shown.

[0035] Figure 4 A schematic diagram of the bypass airflow estimation device according to an embodiment of the present invention is shown. Detailed Implementation

[0036] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0037] In one embodiment, see Figure 1 As shown, this invention provides a bypass airflow estimation method, which is applied to the air system of a fuel cell, comprising:

[0038] Obtain the correspondence between the bypass valve opening, actual pressure ratio, and standardized flow rate.

[0039] Obtain the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the target fuel cell's air system.

[0040] The actual pressure ratio of the bypass valve is calculated based on the obtained infeed air pressure and ambient pressure. The standardized flow rate of the bypass valve is determined based on the obtained bypass valve opening, the calculated actual pressure ratio of the bypass valve, and the corresponding relationship.

[0041] The correction factor is determined based on the infeed air temperature and infeed air pressure. The correction factor is then used to correct the standardized flow rate to obtain the bypass air flow rate of the bypass valve.

[0042] This invention estimates the infeed air flow rate of a fuel cell air system using a semi-physical empirical model of valves. Specifically, it utilizes the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the target fuel cell air system obtained during actual operation. The standardized flow rate of the bypass valve is obtained through a semi-empirical physical model of the valve, namely, a table showing the correspondence between the bypass valve opening, actual pressure ratio, and standardized flow rate. Then, a correction coefficient is determined based on the infeed air temperature, infeed air pressure, and ambient pressure. This correction coefficient is used to correct the standardized flow rate, yielding the bypass air flow rate of the bypass valve. On the one hand, obtaining the bypass air flow rate through table lookup and correction eliminates the need for complex calculations; on the other hand, since the relevant data can be directly acquired by the fuel cell controller, there is no need to add an additional mass flow meter, reducing manufacturing costs.

[0043] The following is a detailed analysis and explanation of each step in the bypass airflow estimation method described in this invention.

[0044] Constructing a table relating the bypass valve opening, actual pressure ratio, and standardized flow rate is the core foundation of the entire estimation process. Under different load demands and environmental conditions, the bypass valve opening is finely adjusted. Simultaneously, high-precision pressure sensors and flow measurement equipment are used to accurately measure and record the corresponding actual pressure ratio and standardized flow rate. Noise-generating algorithms are employed to remove data, and methods such as multiple linear regression are used for data fitting and analysis, thereby establishing a scientific and accurate table of correspondences.

[0045] Obtaining the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the target fuel cell air system is a crucial prerequisite for ensuring accurate estimations. The bypass valve opening can be directly obtained through feedback signals from the electronic control system, directly reflecting the degree of bypass line opening. Infeed air pressure and temperature not only affect the electrochemical reaction rate inside the fuel cell but are also closely related to the physical properties of the gases. Ambient pressure refers to the pressure of the environment outside the fuel cell and is an important reference for calculating the actual pressure ratio; its value varies with factors such as altitude and climate conditions. To obtain high-precision data, the selected sensors must possess good stability, accuracy, and rapid response capabilities, and must be regularly calibrated and maintained to ensure data reliability.

[0046] The actual pressure ratio of the bypass valve is calculated based on the obtained inlet air pressure and ambient pressure. The formula is: Actual pressure ratio = Ambient pressure / Inlet air pressure. The actual pressure ratio clearly shows the pressure change of the gas on both sides of the bypass valve and is a key indicator for judging the gas flow trend. Based on the obtained bypass valve opening and the calculated actual pressure ratio, the corresponding standardized flow rate is obtained by looking up the corresponding value in a pre-built correspondence table.

[0047] Correction coefficients are determined based on the infeed air temperature, infeed air pressure, and ambient pressure. These correction coefficients are then used to correct the standardized flow rate, ultimately yielding the bypass air flow rate of the bypass valve. The corrected flow rate data more accurately reflects the bypass air flow rate under actual operating conditions, providing reliable data support for the precise control of the fuel cell air system.

[0048] The bypass airflow estimation method described in this invention, through comprehensive consideration and precise calculation of multiple parameters, can adapt to complex and ever-changing operating conditions, providing a scientific basis for the optimized control of fuel cell air systems and powerfully promoting the application and development of fuel cell technology in the field of clean energy.

[0049] In this embodiment, see Figure 2 As shown, the air system of the fuel cell includes a stack 1, an air filter 2, an air compressor 3, an intercooler 4, a shut-off valve 5, a back pressure valve 6, and a bypass valve 7. The air filter 2, the air compressor 3, the intercooler 4, and the shut-off valve 5 are sequentially connected to the air inlet of the stack 1. The back pressure valve 6 is connected to the air outlet of the stack 1. The pipeline between the shut-off valve 5 and the stack 1 is connected to the pipeline between the back pressure valve 6 and the stack 1 through the bypass valve 7. The air filter 2 is equipped with a flow meter 8 for collecting the air filter flow rate. The pipeline between the shut-off valve 5 and the air inlet of the stack 1 is equipped with a pressure sensor 9 for collecting the stack inlet pressure.

[0050] In a preferred embodiment of the present invention, the correction coefficients include a standard temperature correction coefficient, a standard pressure ratio correction coefficient, and a relative flow ratio correction coefficient.

[0051] Furthermore, the formula for calculating the standard temperature correction factor is as follows: In the formula: a1 is the standard temperature correction factor, T std T is the standard temperature. up This refers to the temperature of the air entering the reactor.

[0052] Furthermore, the formula for calculating the standard pressure ratio correction factor is as follows: In the formula: a2 is the standard pressure ratio correction coefficient, P std For standard pressure, P up This refers to the infeed air pressure.

[0053] Furthermore, the formula for calculating the relative flow ratio correction coefficient is as follows:

[0054] In the formula: a3 is the relative flow ratio correction coefficient, P down Due to environmental pressures, P up denoted as the infeed air pressure, and k as the air adiabatic index.

[0055] For example, see Figure 3 The graph shows the relative flow ratio coefficient. As can be seen from the graph, the relative flow ratio coefficient is related to the pressure ratio Pr.

[0056] In a preferred embodiment of the present invention, the bypass air flow rate of the bypass valve The formula for calculation is:

[0057] In the formula, For the bypass valve, a1 is the standard temperature correction factor, a2 is the standard pressure ratio correction factor, and a3 is the relative flow ratio correction factor.

[0058] In a preferred embodiment of the present invention, the correspondence between the opening degree of the bypass valve, the actual pressure ratio and the standardized flow rate is obtained through a bypass valve calibration test.

[0059] The bypass valve calibration test includes the following steps:

[0060] Step 1, Preparation of test equipment: The test equipment includes an actuator that can precisely control the opening of the bypass valve, a high-precision pressure sensor for measuring the infeed air pressure and ambient pressure, a flow measurement device (such as a mass flow meter) for measuring the standardized flow rate, and a data acquisition component for recording various data in real time during the test.

[0061] Step 2, Set Test Conditions: Based on the actual operating conditions that the fuel cell may face, determine a series of combinations of bypass valve opening, inlet air pressure, and ambient pressure. For example, the bypass valve opening is adjusted from 0% to 100% at preset intervals (such as 5%); the inlet air pressure and ambient pressure are set according to the actual conditions under different altitudes and loads.

[0062] Step 3, Data Acquisition: Under each set of operating conditions, wait for the system to run stably for a period of time to ensure the accuracy of the measurement data. Then, record the bypass valve opening, infeed air pressure, ambient pressure, and corresponding standardized flow rate using the data acquisition component. The data acquisition process needs to be repeated multiple times to obtain a sufficient number of data points.

[0063] Step 4: Calculate the actual pressure ratio: Based on the collected inlet air pressure and ambient pressure, calculate the actual pressure ratio for each operating condition according to the formula "actual pressure ratio = ambient pressure / inlet air pressure".

[0064] Step 5: Data processing and relation table construction.

[0065] Data cleaning: Due to external interference and other factors during the experiment, the collected data may contain noise or outliers. Therefore, it is necessary to clean the collected data to remove obviously unreasonable data points.

[0066] Data fitting: Use appropriate mathematical methods (such as multiple linear regression, polynomial fitting, etc.) to fit the cleaned data and find the mathematical relationship between bypass valve opening, actual pressure ratio and standardized flow rate.

[0067] Constructing a Relationship Table: The fitted mathematical relationships are transformed into a corresponding relationship table. Specifically, the bypass valve opening and actual pressure ratio are discretized, divided into intervals according to certain intervals, and then the corresponding standardized flow rate value is found in each interval and filled into the relationship table. With this setup, in practical applications, the standardized flow rate corresponding to different bypass valve openings and different actual pressure ratios can be quickly obtained by querying this relationship table.

[0068] In a preferred embodiment of the present invention, the bypass valve opening, infeed air pressure, infeed air temperature and ambient pressure of the air system are acquired by the fuel cell controller.

[0069] In one embodiment, see Figure 4 As shown, the present invention provides a bypass airflow estimation device, which can perform the steps of the bypass airflow estimation method described above. The estimation device 10 includes a first acquisition module 11, a second acquisition module 12, a first determination module 13, and a second determination module 14.

[0070] The first acquisition module 11 is used to acquire the correspondence between the opening degree of the bypass valve, the actual pressure ratio and the standardized flow rate.

[0071] The second acquisition module 12 is used to acquire the bypass valve opening, infeed air pressure, infeed air temperature and ambient pressure of the air system of the target fuel cell.

[0072] The first determining module 13 calculates the actual pressure ratio of the bypass valve based on the acquired inlet air pressure and ambient pressure, and determines the standardized flow rate of the bypass valve based on the acquired bypass valve opening, the calculated actual pressure ratio of the bypass valve, and the corresponding relationship.

[0073] The second determining module 14 determines a correction coefficient based on the infeed air temperature, infeed air pressure and ambient pressure, and uses the correction coefficient to correct the standardized flow rate to obtain the bypass air flow rate of the bypass valve.

[0074] In one embodiment, the present invention provides a method for estimating the infeed air flow rate, which is applied to the air system of a fuel cell, comprising:

[0075] Obtain the air filter flow rate and bypass valve operating status of the air system of the target fuel cell;

[0076] When the bypass valve is in the closed state, the inlet air flow rate of the air system of the target fuel cell is the air filter flow rate;

[0077] When the bypass valve is in the open state, the inlet air flow rate of the air system of the target fuel cell is the difference between the air filter flow rate and the bypass air flow rate of the bypass valve, wherein the bypass air flow rate is obtained by the bypass air flow rate estimation method described above.

[0078] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A method for estimating bypass airflow, characterized in that, Air systems used in fuel cells include: A table showing the correspondence between the bypass valve opening degree, actual pressure ratio, and standardized flow rate was obtained through bypass valve calibration tests. Obtain the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the air system of the target fuel cell; The actual pressure ratio of the bypass valve is calculated based on the obtained infeed air pressure and ambient pressure. The standardized flow rate of the bypass valve is determined based on the obtained bypass valve opening, the calculated actual pressure ratio of the bypass valve, and the corresponding relationship. The correction factor is determined based on the infeed air temperature, infeed air pressure and ambient pressure. The correction factor is then used to correct the standardized flow rate to obtain the bypass air flow rate of the bypass valve. The correction factors include standard temperature correction factor, standard pressure ratio correction factor, and relative flow ratio correction factor; The formula for calculating the standard temperature correction factor is as follows: In the formula: This is the standard temperature correction factor. T std Standard temperature, T up The temperature of the air entering the reactor; The formula for calculating the standard pressure ratio correction factor is as follows: In the formula: This is the standard pressure ratio correction factor. P std For standard pressure, P up This refers to the infeed air pressure. The formula for calculating the relative flow ratio correction factor is as follows: In the formula: This is a correction factor for the relative flow ratio. P down Due to environmental pressures, P up The infeed air pressure, k The air insulation index; The bypass air flow rate of the bypass valve The calculation formula is In the formula, For the standardized flow rate of the bypass valve, This is the standard temperature correction factor. This is the standard pressure ratio correction factor. This is the relative flow ratio correction factor.

2. The bypass airflow estimation method according to claim 1, characterized in that: The fuel cell controller acquires data on the bypass valve opening, infeed air pressure, infeed air temperature, and ambient pressure of the air system.

3. A bypass airflow estimation device, characterized in that, The steps for performing the bypass airflow estimation method as described in any one of claims 1 to 2 include: The first acquisition module is used to obtain a table showing the correspondence between the opening degree of the bypass valve, the actual pressure ratio, and the standardized flow rate through the bypass valve calibration test. The second acquisition module is used to acquire the bypass valve opening, infeed air pressure, infeed air temperature and ambient pressure of the air system of the target fuel cell; The first determination module calculates the actual pressure ratio of the bypass valve based on the acquired infeed air pressure and ambient pressure, and obtains the corresponding normalized flow rate of the bypass valve by looking up a table based on the acquired bypass valve opening and the calculated actual pressure ratio of the bypass valve. The second determining module determines a correction coefficient based on the infeed air temperature, infeed air pressure and ambient pressure, and uses the correction coefficient to correct the standardized flow rate to obtain the bypass air flow rate of the bypass valve. The correction factors include standard temperature correction factor, standard pressure ratio correction factor, and relative flow ratio correction factor; The formula for calculating the standard temperature correction factor is as follows: In the formula: This is the standard temperature correction factor. T std Standard temperature, T up The temperature of the air entering the reactor; The formula for calculating the standard pressure ratio correction factor is as follows: In the formula: This is the standard pressure ratio correction factor. P std For standard pressure, P up This refers to the infeed air pressure. The formula for calculating the relative flow ratio correction factor is as follows: In the formula: This is a correction factor for the relative flow ratio. P down Due to environmental pressures, P up The infeed air pressure, k The air insulation index; The bypass air flow rate of the bypass valve The calculation formula is In the formula, For the standardized flow rate of the bypass valve, This is the standard temperature correction factor. This is the standard pressure ratio correction factor. This is the relative flow ratio correction factor.

4. A method for estimating infeed airflow, characterized in that, Air systems used in fuel cells include: Obtain the air filter flow rate and bypass valve operating status of the air system of the target fuel cell; When the bypass valve is in the closed state, the inlet air flow rate of the air system of the target fuel cell is the air filter flow rate; When the bypass valve is in the open state, the inlet air flow rate of the air system of the target fuel cell is the difference between the air filter flow rate and the bypass air flow rate of the bypass valve, wherein the bypass air flow rate is obtained by the bypass air flow rate estimation method as described in any one of claims 1 to 2.

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