A method for accelerating durability testing of fuel cells for vehicles
The accelerated durability test method for automotive fuel cells addresses inefficiencies in existing methods by combining simulation and testing to accurately simulate real-world conditions, ensuring reliable and efficient durability verification.
Patent Information
- Application Number
- CN202111528279.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2021-12-14
- Publication Date
- 2024-12-20
- Estimated Expiration
- 2041-12-14
AI Technical Summary
Existing durability testing methods for automotive fuel cells are inefficient, fail to consider system control strategy defects, and do not accurately reproduce actual operating conditions, leading to inconsistent and unreliable durability evaluations.
An accelerated durability test method that combines simulation and actual testing at various stages of vehicle development, using vehicle energy distribution models and statistical analysis to derive operating conditions, and minimizing load fluctuations to simulate real-world usage scenarios.
Enables high-accuracy, efficient, and flexible durability verification for fuel cell systems, reducing development time and costs by simulating real-world conditions and providing statistical durability results.
Smart Images
Figure CN114114028B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of fuel cell detection, and in particular to an accelerated durability testing method for a fuel cell for a vehicle. Background Art
[0002] Proton exchange membrane fuel cells are power generation devices that directly convert hydrogen and air into electricity through electrochemical reactions. In the commercialization of fuel cells, durability is one of the important issues to be solved. Due to the long life of automotive fuel cells, especially commercial vehicles, they need to be more than 10,000 hours or even more than 20,000 hours. Durability testing equivalent to usage time is obviously not a good choice. Because this will greatly extend the product development cycle and greatly increase development costs, these are not acceptable to companies developing products and end customers. Therefore, the demand for accelerated durability testing methods has emerged. At the same time, for end customers, especially before the mass production stage, they are often more concerned about a certain configuration of fuel cell models and the average durability of the system. This is because the future use and revenue of future vehicles can be measured through the statistical durability level.
[0003] There are many methods for durability research and accelerated testing in current research and public information. However, the following problems are common:
[0004] 1. Accelerated durability testing is performed based on known failure modes, but errors such as system control strategy defects cannot be considered. At the same time, the impact between failures cannot be reproduced in the test, which is inconsistent with the actual situation and cannot be objectively evaluated. For example, patent CN 108417868 A uses a combination of weights and attenuation conditions, and patent CN200710100151.4 can obtain durability through segmented characterization and linear superposition;
[0005] 2. The fuel cell stack test conditions are artificially formulated without a good logical chain support and are basically disconnected from the actual situation. They can be used as durability test standards, but they are of no help in actual durability. For example, patent CN109683093 A and the load conditions released by some OEMs all have strong human factors. Different stacks can use the same conditions to compare their durability levels, but it is impossible to obtain lifespan conditions close to those in actual operation.
[0006] 3. Online durability prediction is a prediction for a specific vehicle, rather than a statistical conclusion. For example, the Class A patent 109683093 focuses more on the future life prediction based on a specific case model and the specific object system being tested. It does not meet statistical requirements and cannot achieve accelerated testing.
[0007] Therefore, it is necessary to start from commercial applications and solve the durability evaluation of a fuel cell vehicle with a certain configuration and the installed fuel cell system with statistical results. Summary of the invention
[0008] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an accelerated durability test method for automotive fuel cells, which can make an accurate durability evaluation with statistical results for a fuel cell vehicle with a certain configuration and the fuel cell system installed therein.
[0009] The purpose of the present invention can be achieved by the following technical solutions:
[0010] A durability accelerated testing method for a fuel cell for a vehicle, which completes accelerated durability verification by combining a model and a test, and is implemented in a system design stage, a system function verification stage, a whole vehicle design stage, or a whole vehicle function verification stage.
[0011] When durability verification begins at the system design stage, the operating conditions and offset operating conditions required in the test are derived from simulation calculations;
[0012] When durability verification begins at the system function verification stage, the operating conditions and offset operating conditions required in the test are derived from actual tests;
[0013] When durability verification begins at the vehicle design stage, the load conditions required in the test are derived from simulation calculations;
[0014] When durability verification begins at the vehicle function verification stage, the load conditions required in the test are obtained using actual operation test methods.
[0015] The method of the present invention specifically comprises the following steps:
[0016] S1: Based on the input road spectrum and vehicle power system configuration data, the fuel cell system load output condition is obtained through the whole vehicle energy distribution model simulation.
[0017] The vehicle energy distribution model calculates the motor torque and speed required to meet the road spectrum based on vehicle dynamics. On this basis, the fuel cell load output condition is finally obtained through the motor spectrum, power battery charge and discharge curve, and fuel cell output power curve.
[0018] Furthermore, in the process of obtaining the load output working condition of the fuel cell, the SOC value of the lithium battery is kept within a window of small values, that is, shallow charging and shallow discharge are performed to reduce the variable load of the fuel cell.
[0019] S2: Through fuel cell system simulation or actual fuel cell system testing, the fuel cell system load output condition obtained by S1 is input, and the stack inlet parameters are calculated through online sensors or simulation based on system component characteristics to form the relationship between the inlet parameters and time, which corresponds to the fuel cell system load output condition.
[0020] The stack inlet parameters include air / hydrogen parameters and coolant parameters. The air / hydrogen parameters include flow rate, temperature, humidity and pressure. The coolant parameters include flow rate and pressure.
[0021] S3: Count the frequency of the climate type in which the vehicle is running during the entire life cycle of the fuel cell, and then obtain the deviation of the fuel cell stack operating conditions from normal temperature during the startup and full operating conditions. Specifically:
[0022] Obtain the frequency of the vehicle's operating climate state during the entire life cycle of the fuel cell, including multiple factors that affect the durability of the fuel cell stack, such as sub-zero low-temperature startup and high-temperature load, and place the fuel cell system in a statistically representative climate state, that is, the system gas inlet and the system initial state are consistent with the climate state environment. Through system simulation or actual testing, obtain the deviation of the fuel cell stack operating conditions during the startup phase, the full operating condition phase and normal temperature.
[0023] S4: Count the most likely operation schedule for the vehicle, that is, obtain the number of vehicle starts, shutdowns and hot starts per day, as well as the running time after starting, in order to obtain the impact of start-stop on the durability of the fuel cell system over the entire life cycle.
[0024] S5: According to the statistical results of climate conditions and vehicle operation time, the durability test of the fuel cell stack is converted from time units to the number of cycle conditions, and each data is classified into operating conditions with different offsets and start times, and then combined to form a preliminary stack durability test condition.
[0025] S6: Artificially eliminate the load and operating conditions in the preliminary battery stack durability test conditions and keep them in a steady state to obtain the final accelerated durability test conditions and complete the durability verification.
[0026] Furthermore, in S1, when simulating the energy distribution model of the whole vehicle, the items related to the energy configuration of the whole vehicle include vehicle weight, drive motor MAP, power battery capacity, discharge curve and fuel cell system polarization curve and DCDC efficiency. The energy distribution actions of the whole vehicle include making the fuel cell output energy flow to the motor, or flow to the lithium battery for charging; the lithium battery output discharges to the motor or receives charging from the fuel cell, and the motor is in a power-using or power-off state. The load output conditions of the fuel cell system when the vehicle is fully loaded and unloaded are obtained through the simulation of the energy distribution model of the whole vehicle.
[0027] The vehicle fuel cell durability accelerated testing method provided by the present invention has at least the following beneficial effects compared with the prior art:
[0028] 1) The method of the present invention can realize accelerated durability verification in the system design stage, system function verification stage, vehicle design stage or vehicle function verification stage through computer simulation or experimental testing, or a combination of the two, that is, a combination of model and test; through fuel cell system simulation or actual testing of the fuel cell system, high-accuracy durability acceleration test results can be obtained for a certain vehicle model and operating area, and the verification method is simple, efficient and flexible.
[0029] 2) In the process of obtaining the load output working condition of the fuel cell, keeping the lithium battery SOC value within a small value window, that is, shallow charging and shallow discharge, can reduce the fuel cell load variation, and by compressing the stable working condition, the durability verification efficiency can be greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS
[0030] Figure 1 The schematic diagram of the principle of the durability accelerated testing method of a fuel cell for a vehicle of the present invention;
[0031] Figure 2 It is a schematic diagram of the working condition of CHTC-B Chinese city bus in the embodiment;
[0032] Figure 3 The load simulation result diagram of a fuel cell system of a 12-meter bus based on CHTC-B in the embodiment, wherein sub-figure (a) is an empty load simulation result diagram, and sub-figure (b) is a fully loaded load simulation result diagram;
[0033] Figure 4 It is a single-cycle load condition diagram analyzed from a single-day operation, where sub-diagram (a) is a single-cycle load condition diagram A, and sub-diagram (b) is a single-cycle load condition diagram B;
[0034] Figure 5 This is a diagram showing the range of climate change and the division of climate conditions in Beijing in the embodiment. DETAILED DESCRIPTION
[0035] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should belong to the scope of protection of the present invention.
[0036] Example
[0037] The present invention relates to an accelerated durability test method for a vehicle fuel cell. The durability of a fuel cell generally refers to the durability of a fuel cell stack in a fuel cell system. Since the durability verification needs to last for a long time, the start time of the durability verification can vary greatly. According to the time sequence of the development of components and the whole vehicle, the durability verification can be implemented in the system design stage, or the system function verification stage, or in the whole vehicle design stage or the whole vehicle function verification stage. This means that the conditions and resources available at different starting time points are different. The applicability is also fully considered in the present invention. When the system is in the design stage and the durability study begins, the operating conditions and offset operating conditions required in the test are derived from simulation calculations; when the system is in the function verification stage, it is recommended that the operating conditions and offset operating conditions are derived from actual tests for greater accuracy; when the whole vehicle is in the design stage and the durability verification begins, the load conditions required in the test are derived from simulation calculations; when the whole vehicle is in the function verification stage and the durability verification begins, it is recommended that the load conditions be obtained by the actual operation test method.
[0038] In order to obtain the statistical average durability, the present invention completes the accelerated durability verification by combining the model and the test. First, by inputting the road spectrum, the vehicle power system configuration can obtain the output load condition of the fuel cell system through the simulation of the vehicle energy distribution model. The model is mainly based on the vehicle dynamics calculation to meet the motor torque and speed required by the road spectrum. Further, on this basis, the load output condition of the fuel cell is finally obtained through the motor spectrum, the power battery charge and discharge curve and the fuel cell output power curve. In general, in order to achieve high durability of the fuel cell, the load fluctuation constant load output is reduced as much as possible. At the same time, in the process of obtaining the load output condition of the fuel cell, it is necessary to keep the lithium battery SOC value in a smaller window as much as possible, that is, shallow charging and shallow discharge. In the present invention, the input road spectrum includes but is not limited to the Chinese city bus condition road spectrum CHTC-B.
[0039] Then, through the simulation of the fuel cell system or the actual test of the fuel cell system, the required load condition obtained in the first step is input, and the stack inlet parameters are obtained through online sensors or simulation calculations based on the characteristics of system components. The air and hydrogen parameters include at least: flow rate, temperature, humidity and pressure. The coolant parameters include at least: flow rate and pressure. Finally, the relationship between the time and the above parameters is formed, and corresponds to the load condition.
[0040] Furthermore, the frequency of the vehicle's operating climate conditions during the entire life cycle of the fuel cell is investigated and counted, mainly including sub-zero low-temperature startup and high-temperature loads, which may have a durable impact on the stack. According to the method in the previous step, the fuel cell system is placed in the statistically representative climate state, that is, the system gas inlet and the system initial state are consistent with the climate environment. In this way, the deviation of the stack operating conditions from normal temperature during startup and even the full operating stage can be tested. Similarly, the above results can also be obtained through system simulation methods.
[0041] In order to further understand the impact of fuel cell system start-stop on durability during the entire life cycle, it is also necessary to investigate and count the most likely operation schedule of the vehicle, that is, the number of vehicle starts and stops per day, the number of hot starts, and the running time after starting.
[0042] Based on the above statistical results, the durability test of the fuel cell stack was converted from time to the number of cycle conditions. Through the statistics of climate and vehicle operation time, it was finally classified into operating conditions with different offsets and the number of starts. Thus, the preliminary fuel cell stack durability test conditions were formed.
[0043] Since the fuel cell has little effect on durability under the conditions of stable load and stable operating conditions, the state where the load and operating conditions are both in a steady state is artificially eliminated in the above preliminary durability conditions. Thus, the final accelerated durability test conditions are obtained.
[0044] In order to facilitate understanding of the technical details involved in the method of the present invention, this technical solution is provided, but it does not mean that it is limited to the content of this solution. In this case, the durability acceleration test method based on fuel cell city buses was completed.
[0045] The road map used in this embodiment is the China City Bus Condition Road Map (CHTC-B), which is developed by China Automotive Technology and Research Center Co., Ltd. The time driving speed diagram drawn by the road map is as follows: Figure 2 shown.
[0046] The selected vehicle is a 12-meter bus. The items related to the energy configuration of the whole vehicle include: vehicle weight, drive motor MAP, power battery capacity and discharge curve, fuel cell system polarization curve, and DCDC efficiency. From the time-speed curve, the driving force demand of the motor can be easily obtained through vehicle dynamics. Furthermore, the main actions in the energy distribution of the whole vehicle include allowing the fuel cell output energy to flow to the motor, or to the lithium battery for charging; while the lithium battery outputs to the motor for discharge or receives charging from the fuel cell, and the motor is in a state of power consumption or power stop. In order to extend the life, the fuel cell load variation is minimized as much as possible during energy control to reduce the large range of SOC value changes of the lithium battery. Through simulation, the load output of the fuel cell system when the vehicle is fully loaded and unloaded can be obtained respectively. Such as Figure 3 As shown in the figure, P m,ele Refers to the load condition of the bus driving motor; P fc Refers to the power output load of the fuel cell system. A brief description is shown in Table 1:
[0047] Table 1 Fuel cell system load output power when the vehicle is fully loaded and unloaded
[0048] P1 share P2 share Load change times Fully loaded 0 100％ 0 No load 23％ 77％ 6 times
[0049] From the table above, we can see that the fuel cell output power value is only related to the average power consumption, and has nothing to do with the vehicle speed and road spectrum changes. This also indirectly shows that the energy configuration of the vehicle is very good. From the fuel cell failure mode, we can know that the load-related attenuation mainly includes the load value and the number of load changes. Therefore, the fuel cell system load condition is also related to the vehicle operation time statistics during actual operation.
[0050] The following are the statistics of vehicle pre-rotation.
[0051] Table 2 Vehicle operation schedule model
[0052]
[0053]
[0054] From the simulation results, we can know that the working condition covers 11 hours of load changes. However, it is difficult to obtain a deterministic result for the actual number of passengers in the vehicle. Considering that the final fuel cell load must be between the above range, we chose to calculate the average value. That is, P2 is adjusted to 89%, P1 is adjusted to 11%, and the number of load changes remains unchanged. Thus, the single-cycle load condition of the fuel cell system can be obtained, such as Figure 4As shown. It should be noted that, since the steady state will be compressed later, the match between the steady state time length and the simulation result is not considered. However, due to the lunch break of the vehicle operation, the difference between cold engine start and hot engine start is increased, which may affect the operating condition deviation and the final life. The working condition is artificially decomposed into two different single-cycle load conditions, named A and B respectively, as shown in Figure 4 As shown in sub-figure (a) and sub-figure (b).
[0055] Furthermore, the fuel cell system is tested in real time under the load conditions of the above-mentioned single-cycle load conditions A and B, and the operating conditions of the fuel cell stack are tested online, and a complete operating condition spectrum is obtained through the test data. The difference between the two in the test is that the starting cooling temperature of the single-cycle load condition B is higher than that of the single-cycle load condition A. This value depends on the temperature of the area where the fuel cell system is located and the layout of the heat dissipation. The operating condition spectrum mainly includes at least the changing trends of the following parameters over time. Among them, the air and hydrogen parameters at least include: flow rate, temperature, humidity, and pressure. The coolant parameters at least include: flow rate and pressure. In the working conditions, the operating conditions and loads are in a one-to-one correspondence. This means that the operating conditions of the stack have been complete, and they will be referred to as operating conditions A and operating conditions B in the future.
[0056] Furthermore, climate temperature statistics are made for the cities where the vehicle is planned to operate. According to the degree of influence of the fuel cell on the temperature, the climate of Beijing is statistically analyzed in this embodiment and divided into four climate types. At the same time, the number of days corresponding to the four types of climate types throughout the year can be statistically analyzed, that is, the proportion of days, as shown in Table 3. The principle of climate classification depends on the sensitivity of the fuel cell system control to environmental conditions, which is mainly reflected in the changes in the operating conditions of the fuel cell stack. The scope of climate change in Beijing and the division of climate conditions are as follows: Figure 5 shown.
[0057] Table 3 Temperature and humidity statistics for four climate types
[0058]
[0059] Furthermore, according to the fuel cell system being tested under the selected environmental conditions, new corresponding operating condition A-operating condition B are obtained through load condition A-load condition B. Thus, a new operating condition matrix is formed as shown in Table 4.
[0060] Table 4. Matrix number and corresponding relationship of stack operation condition
[0061] Climate conditions Load Condition A Load Condition B Merge Name Climate conditions 1 1#-A 1#-B 1#-AB Climate Condition 2 2#-A 2#-B 2#-AB Climate Condition 3 3#-A 3#-B 3#-AB Climate conditions 4 4#-A 4#-B 4#-AB
[0062] Since the A and B conditions under each climate condition occur in series, they can be directly combined and expressed, as shown in Table 4. At present, the measurement time of the four operating conditions obtained is 10 hours. Since the attenuation of the fuel cell can be ignored under stable conditions, this part of the time can be greatly shortened. The reduced conditions can be marked as 1'#-AB, 2'#-AB, 3'#-AB, 4'#-AB. In order to restore the impact of the attenuation of the previous operating conditions on the subsequent operations, the operating conditions are arranged in the order of the four seasons, and finally the following sequence is formed.
[0063] Table 5 The sequence form obtained by arranging the working conditions in the order of the four seasons
[0064]
[0065] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person familiar with the technical field can easily think of various equivalent modifications or substitutions within the technical scope disclosed by the present invention, and these modifications or substitutions should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.
Claims
1. A method for accelerating the durability test of a fuel cell for a vehicle, characterized in that: This method completes the accelerated durability verification by combining models and tests, and is implemented in the system design stage, system function verification stage, vehicle design stage or vehicle function verification stage; When durability verification begins at the system design stage, the operating conditions and offset operating conditions required in the test are derived from simulation calculations; When durability verification begins at the system function verification stage, the operating conditions and offset operating conditions required in the test are derived from actual tests; When durability verification begins at the vehicle design stage, the load conditions required in the test are derived from simulation calculations; When the durability verification begins at the vehicle function verification stage, the load conditions required in the test are obtained by the actual running test method; The method comprises the following steps: 1) Based on the input road spectrum and vehicle power system configuration data, the fuel cell system load output condition is obtained through vehicle energy distribution model simulation; 2) Through fuel cell system simulation or actual fuel cell system testing, the fuel cell system load output condition obtained in step 1) is input, and the stack inlet parameters are calculated through online sensors or simulation based on system component characteristics to form a relationship between the inlet parameters and time, which corresponds to the fuel cell system load output condition; 3) Count the frequency of the climate types in which the vehicle operates during the entire life cycle of the fuel cell, and then obtain the deviation of the fuel cell stack operating conditions from normal temperature during the startup and full operating conditions; 4) Count the most likely operation schedule for the vehicle, that is, obtain the number of vehicle starts and stops, the number of hot starts, and the running time after starting, so as to obtain the impact of the start and stop of the fuel cell system on the durability during the whole life cycle; 5) According to the statistical results of climate conditions and vehicle operation time, the durability test of the fuel cell stack is converted from time units to the number of cycle conditions, and each data is classified into operating conditions and start times with different offsets, and then combined to form a preliminary stack durability test condition; 6) Artificially eliminate the load and operating conditions in the steady-state conditions in the preliminary battery stack durability test conditions, obtain the final accelerated durability test conditions and complete the durability verification; In step 1), the vehicle energy distribution model calculates the motor torque and speed required to meet the road spectrum based on vehicle dynamics, and on this basis, the load output condition of the fuel cell is finally obtained through the motor spectrum, the power battery charge and discharge curve, and the fuel cell output power curve; In the process of obtaining the load output working condition of the fuel cell, the SOC value of the lithium battery is kept within a small value window, that is, shallow charging and shallow discharge to reduce the variable load of the fuel cell; In step 2), the stack inlet parameters include air / hydrogen parameters and coolant parameters, the air / hydrogen parameters include flow rate, temperature, humidity and pressure, and the coolant parameters include flow rate and pressure; The specific content of step 3) is: Obtain the frequency of the vehicle's operating climate state during the fuel cell's entire life cycle, including multiple factors that affect the durability of the fuel cell stack, including sub-zero low-temperature startup and high-temperature load, and place the fuel cell system in a statistically representative climate state, that is, the system gas inlet and the system initial state are consistent with the climate state environment. Through system simulation or actual testing, obtain the deviation of the fuel cell stack operating conditions at the startup stage, the full operating stage, and normal temperature; In step 1), when simulating the energy distribution model of the whole vehicle, the items related to the energy configuration of the whole vehicle include vehicle weight, drive motor MAP, power battery capacity, discharge curve and fuel cell system polarization curve and DCDC efficiency. The energy distribution actions of the whole vehicle include making the fuel cell output energy flow to the motor, or flow to the lithium battery for charging; the lithium battery output discharges to the motor or receives charging from the fuel cell, and the motor is in power consumption or power stop state. The load output conditions of the fuel cell system when the vehicle is fully loaded and unloaded are obtained through the simulation of the energy distribution model of the whole vehicle.