Vehicle-mounted hydrogen cylinder fatigue life test system

Abstract

The invention relates to the field of hydrogen cylinder testing, and particularly provides a vehicle-mounted hydrogen cylinder fatigue life testing system which comprises a gas source subsystem, a high-pressure pressurization and storage subsystem, a test execution subsystem and a monitoring and control subsystem. The gas source subsystem intelligently switches gas source paths through a gas discharging column, and efficient cyclic utilization of externally supplied gas and recycled gas is achieved. The high-pressure pressurization subsystem provides a stable high-pressure air source through multi-stage compression; the test execution subsystem is provided with an environment bin and a hydrogen preheating and precooling unit to simulate various working conditions; the monitoring and control subsystem achieves accurate control over the inflation and deflation process through a feedforward-feedback composite control algorithm in combination with real-time temperature compensation and anti-integral saturation PID control. According to the invention, while the test economy and continuity are improved, the control precision of constant-speed hydrogen charging and the repeatability of test data in a full-pressure range are ensured, and the high-reliability fatigue test requirements of hydrogen cylinders with different pressure grades are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of hydrogen cylinder testing, in particular to a kind of vehicle-mounted hydrogen cylinder fatigue life test system. BACKGROUND

[0002] For the fatigue life test of vehicle-mounted hydrogen cylinder, the simple closed-loop control architecture of proportional valve and flowmeter is generally used to carry out the cycle test of hydrogen cylinder. In terms of system architecture, the gas supply system is insufficient in intelligentization, and cannot automatically switch the gas supply path according to the gas source pressure state, which affects the continuity and stability of the test. In terms of control method, during the inflation process, as the pressure in the cylinder continuously rises, the pressure difference between the cylinder and the gas source continuously decreases, and the flow naturally attenuates under the fixed valve opening, making it difficult to maintain the standard required uniform speed of hydrogen filling. In addition, due to the Joule-Thomson effect and compression heat, the temperature of hydrogen changes dramatically during the filling and discharging process, which seriously affects the measurement accuracy of the mass flowmeter. Furthermore, the simple PID control cannot cope with complex disturbances such as source pressure fluctuation and back pressure change, and the control accuracy and stability are not ideal. SUMMARY

[0003] To solve the above problems, the present application provides a kind of vehicle-mounted hydrogen cylinder fatigue life test system, which improves the test economy and continuity, ensures the control accuracy of uniform speed of hydrogen filling and the repeatability of test data in the whole pressure range, and meets the high reliability fatigue test requirements of hydrogen cylinders of different pressure grades.

[0004] The technical scheme of the present application provides a kind of vehicle-mounted hydrogen cylinder fatigue life test system, which comprises: A gas source subsystem for transmitting the gas provided by the gas source and the measured cylinder discharge gas recovered through the discharge pipeline to the high-pressure boosting and storage subsystem after equalizing the gas; A high-pressure boosting and storage subsystem comprising a high-pressure compressor set connected to the gas source subsystem through a pipeline, and a high-pressure gas storage tank connected to the high-pressure compressor set, the high-pressure compressor set boosts the gas from the gas source subsystem and stores it into the high-pressure gas storage tank, and the gas in the high-pressure gas storage tank is transmitted to the measured cylinder through the inflation pipeline; A test execution subsystem comprising a measured cylinder arranged in a cylinder test environment chamber, a hydrogen preheating and precooling unit arranged on the inflation pipeline, and proportional valves arranged on the inflation pipeline and the discharge pipeline, respectively; A monitoring and control subsystem comprising a flow monitoring unit arranged on the inflation pipeline and the discharge pipeline for real-time monitoring of the gas flow through the pipeline, a pressure monitoring unit for real-time monitoring of the pressure of the high-pressure gas storage tank and the internal pressure of the measured cylinder, and a test controller electrically connected to the flow monitoring unit, the pressure monitoring unit and the proportional valves, respectively; The test controller is configured to calculate a first feedforward valve opening degree by a first feedforward control model based on the pressure of the high-pressure gas tank and the internal pressure of the tested gas cylinder during the inflation process, and to calculate a first opening degree correction amount by a PID controller with the inflation pipeline mass flow reading after real-time compensation by temperature as feedback, and finally to superimpose the first feedforward valve opening degree and the first opening degree correction amount to generate the final control opening degree of the inflation proportional valve.

[0005] From the above technical solution, the present application has the following advantages: first, a complete gas circulation loop is constructed to improve the recycling efficiency of test gas, reduce hydrogen consumption and test running cost, and further intelligently switch the gas source output pipeline to ensure the continuity of the test process, thereby improving the overall test efficiency; second, the combination of feedforward and feedback is used, combined with physical model and real-time temperature compensation, to achieve constant mass flow control in the full pressure range, control the flow fluctuation of the hydrogen filling process in a small range, improve the accuracy of uniform speed hydrogen filling, and further improve the accuracy of test results; in addition, the feedforward control model can actively predict and compensate the disturbance caused by pressure and temperature changes, and the anti-integral saturation PID design ensures the stability of long-term operation, so that the system can adapt to the test requirements of hydrogen cylinders with different pressure grades such as 35MPa and 70MPa, and by eliminating the influence of temperature change on flow measurement, the accuracy and repeatability of test data are ensured, and the accuracy of test results is further improved. BRIEF DESCRIPTION OF DRAWINGS

[0006] In order to more clearly illustrate the technical solutions of the present application, the drawings required in the description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0007] Figure 1 A schematic diagram of a vehicle-mounted hydrogen cylinder fatigue life test system is provided for the embodiments of the present application.

[0008] Figure 2 A schematic diagram of the final control opening degree generation process for the test process. DETAILED DESCRIPTION

[0009] In order to make the application purpose, features and advantages of the present application more obvious and easy to understand, the technical solutions protected by the present application will be described in detail below with specific embodiments and drawings. Obviously, the following described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0010] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0011] Figure 1 A schematic diagram of a vehicle-mounted hydrogen cylinder fatigue life test system according to an embodiment of the application is shown in FIG. 1, which includes a gas source subsystem, a high-pressure boosting and storage subsystem, a test execution subsystem, and a monitoring and control subsystem. Figure 1 The gas source subsystem is configured to transmit the gas provided by the gas source and the gas recovered from the tested cylinder through the gas recovery pipeline to the high-pressure boosting and storage subsystem after equalizing. Specifically, the gas source subsystem includes a gas source, a gas release column, a recovery compressor, a low-pressure gas storage tank, and a medium-pressure gas storage tank. The gas source is connected to the inlet of the low-pressure gas storage tank through the first path of the gas release column and connected to the inlet of the medium-pressure gas storage tank through the second path of the gas release column. The inlet of the low-pressure gas storage tank is also connected to the tested cylinder through the gas recovery pipeline, and the outlet of the low-pressure gas storage tank is connected to the inlet of the medium-pressure gas storage tank through the recovery compressor. The outlet of the medium-pressure gas storage tank is connected to the high-pressure compressor set of the high-pressure boosting and storage subsystem through a pipeline. When the pressure of the gas source is higher than a preset pressure, the gas source gas is directly delivered to the high-pressure boosting and storage subsystem through equalization. Otherwise, the recovered gas and the low-pressure gas source gas are delivered to the high-pressure boosting and storage subsystem through equalization after being increased by the recovery compressor. Correspondingly, the test controller of the monitoring and control subsystem is configured to close the first path of the gas release column and open the second path when the pressure of the gas source is higher than a preset pressure threshold. When the pressure of the gas source is lower than the preset pressure threshold, the first path of the gas release column is opened and the second path is closed. The opening and closing of the pipeline can be controlled by proportional valves on the first path and the second path. In one specific embodiment, a long-pipe trailer is used as the gas source.

[0012] The gas source subsystem is configured to transmit the gas provided by the gas source and the gas recovered from the tested cylinder through the gas recovery pipeline to the high-pressure boosting and storage subsystem after equalizing. Specifically, the gas source subsystem includes a gas source, a gas release column, a recovery compressor, a low-pressure gas storage tank, and a medium-pressure gas storage tank. The gas source is connected to the inlet of the low-pressure gas storage tank through the first path of the gas release column and connected to the inlet of the medium-pressure gas storage tank through the second path of the gas release column. The inlet of the low-pressure gas storage tank is also connected to the tested cylinder through the gas recovery pipeline, and the outlet of the low-pressure gas storage tank is connected to the inlet of the medium-pressure gas storage tank through the recovery compressor. The outlet of the medium-pressure gas storage tank is connected to the high-pressure compressor set of the high-pressure boosting and storage subsystem through a pipeline. When the pressure of the gas source is higher than a preset pressure, the gas source gas is directly delivered to the high-pressure boosting and storage subsystem through equalization. Otherwise, the recovered gas and the low-pressure gas source gas are delivered to the high-pressure boosting and storage subsystem through equalization after being increased by the recovery compressor. Correspondingly, the test controller of the monitoring and control subsystem is configured to close the first path of the gas release column and open the second path when the pressure of the gas source is higher than a preset pressure threshold. When the pressure of the gas source is lower than the preset pressure threshold, the first path of the gas release column is opened and the second path is closed. The opening and closing of the pipeline can be controlled by proportional valves on the first path and the second path. In one specific embodiment, a long-pipe trailer is used as the gas source.

[0013] The high-pressure boosting and storage subsystem includes a high-pressure compressor set connected to the gas source subsystem through a pipeline. The high-pressure compressor set boosts the gas from the medium-pressure gas storage tank and stores it in the high-pressure gas storage tank. The gas in the high-pressure gas storage tank is transmitted to the tested cylinder through the gas charging pipeline. Specifically, the high-pressure boosting and storage subsystem includes two high-pressure compressors and one high-pressure gas storage tank. The outlet of the medium-pressure gas storage tank is connected to the high-pressure gas storage tank through the two high-pressure compressors, i.e., the gas in the medium-pressure gas storage tank is boosted by the two high-pressure compressors and then transmitted to the high-pressure gas storage tank.

[0014] The test execution subsystem includes the tested cylinder arranged in the cylinder test environment chamber, a hydrogen preheating and precooling unit arranged on the gas charging pipeline, and proportional valves arranged on the gas charging pipeline and the gas recovery pipeline, respectively.

[0015] The monitoring and control subsystem comprises: a flow monitoring unit arranged on the inflation pipeline and the deflation pipeline for monitoring the flow of gas flowing through the pipeline in real time, a pressure monitoring unit for monitoring the pressure of the high-pressure gas tank and the internal pressure of the measured gas cylinder in real time, and a test controller electrically connected with the flow monitoring unit, the pressure monitoring unit and the proportional valve.

[0016] The test controller is configured to, during the inflation process, calculate a first feedforward valve opening degree based on the pressure of the high-pressure gas tank and the internal pressure of the measured gas cylinder, take the inflation pipeline mass flow reading after real-time compensation of temperature as feedback, calculate a first opening degree correction amount through a PID controller, and finally superimpose the first feedforward valve opening degree and the first opening degree correction amount to generate the final control opening degree of the inflation proportional valve.

[0017] Further, the test controller is also configured to, during the deflation process, calculate a second feedforward valve opening degree based on the internal pressure of the measured gas cylinder and the pressure of the low-pressure gas tank, take the deflation pipeline mass flow reading after real-time compensation of temperature as feedback, calculate a second opening degree correction amount through a PID controller, and finally superimpose the second feedforward valve opening degree and the second opening degree correction amount to generate the final control opening degree of the deflation proportional valve.

[0018] Based on the vehicle-mounted hydrogen cylinder fatigue life test system of the embodiment, the process of vehicle-mounted hydrogen cylinder fatigue life test includes the following stages.

[0019] The first stage: system initialization and gas supply.

[0020] After the system is started, the test controller first monitors the output pressure of the long-pipe trailer (gas source). If the gas source pressure is higher than the preset threshold value: the controller instructs the pressure relief column to close the first path and open the second path, so that the high-pressure gas directly enters the medium-pressure gas tank for pressure equalization, and the medium-pressure gas source in the system is quickly established. If the gas source pressure is lower than the preset threshold value: the controller instructs the pressure relief column to open the first path and close the second path, so that the gas first enters the low-pressure gas tank for temporary storage.

[0021] The second stage: high-pressure gas preparation.

[0022] The gas from the medium-pressure gas tank enters the high-pressure boosting and storage subsystem. The gas flows through the 1# high-pressure compressor and the 2# high-pressure compressor in sequence, is boosted to the required high pressure (such as 90 MPa or 45 MPa) step by step, and is stored in the high-pressure gas tank for standby use.

[0023] The third stage: inflation test and precise control.

[0024] Environment simulation and gas pre-treatment: The test environment chamber starts to work, and the external environment of the tested cylinder is adjusted to the limit temperature required by the standard (e.g. -40°C to 85°C). Meanwhile, the hydrogen pre-heating and pre-cooling unit starts to work, and the hydrogen gas from the high-pressure storage tank is pre-treated to meet the required temperature of the filling gas.

[0025] High-precision constant-speed filling: The pre-treated high-pressure hydrogen gas flows to the tested cylinder through the filling pipeline. Meanwhile, the monitoring and control subsystem works all the time: the flow monitoring unit and the pressure monitoring unit collect the mass flow of the filling pipeline, the pressure of the high-pressure storage tank and the pressure inside the tested cylinder in real time; based on the above pressure parameters, the test controller quickly calculates the approximate opening of the filling proportional valve (corresponding to the first feedforward valve opening) through the first feedforward control model; at the same time, the test controller takes the accurate mass flow reading compensated by the temperature in real time as the feedback, and calculates the fine opening correction amount through the PID controller; finally, the feedforward opening and the feedback correction amount are superimposed to generate the final control command of the filling proportional valve, realizing accurate constant mass flow control and ensuring to meet the standard requirement of "uniform speed filling of hydrogen".

[0026] The fourth stage: gas discharge test and gas recovery.

[0027] After filling to the target pressure and maintaining the pressure, the gas discharge phase starts. The test controller controls the opening of the gas discharge proportional valve, and the high-pressure hydrogen gas in the tested cylinder flows out through the gas discharge pipeline. At this time, the flow monitoring unit monitors the discharge speed to ensure that it is not higher than the limit value of the EFV (fusible plug). The test controller also adopts a feedforward-feedback composite control strategy, dynamically adjusts the opening of the gas discharge proportional valve through the second feedforward control model and the PID control, and realizes safe and efficient gas discharge under the premise of meeting the standard requirements. The discharged gas is directly returned to the low-pressure storage tank, completing a cycle of gas recovery.

[0028] The fifth stage: gas recycling.

[0029] The recovered gas (and possibly supplemented low-pressure gas source gas) collected in the low-pressure storage tank is extracted and pressurized by the recovery compressor, and then delivered back to the medium-pressure storage tank. Thereafter, the gas will re-enter the second stage as the gas source of the high-pressure compressor set and be pressurized again for subsequent testing, thereby forming a closed gas circulation test loop, improving the economy and environmental protection of the test.

[0030] The sixth stage: cycle test and termination.

[0031] The third to fifth stages above constitute a complete test cycle. The test controller automatically and continuously executes the inflation-holding-deflation process according to the preset program, such as the number of cycles required by the standard, until the set number of cycles is reached or the gas cylinder fails. The system records all pressures, flow rates, temperatures, and control parameters throughout the process, generating a complete test report.

[0032] In an alternative embodiment, the first feedforward control model is constructed according to the dynamic relationship between the mass flow rate and the proportional valve opening, the pre-valve pressure, and the post-valve pressure. Specifically, the first feedforward control model is established through experiments, including the following steps.

[0033] a1) In the system calibration stage, set up an experimental parameter matrix covering the working range of the test system, including: within the working pressure range of the high-pressure gas storage tank, select multiple different pre-valve pressure points ; within the expected pressure range of the tested gas cylinder, select multiple different post-valve pressure points ; within the effective opening range of the proportional valve, select multiple different opening points .

[0034] b1) For each combination in the experimental parameter matrix , perform a steady-state flow data acquisition operation, including adjusting the system pressure to stabilize the pre-valve pressure at , the post-valve pressure at , and adjusting the proportional valve to the specified opening ; after the gas flow stabilizes, collect and record the mass flow meter reading after real-time temperature compensation at this time .

[0035] c1) Based on all the collected data points , generate the first feedforward control model through data fitting.

[0036] It should be noted that system calibration preparation is performed before the experiment, including connecting the high-pressure boosting and storage subsystem, test execution subsystem, and monitoring and control subsystem into normal working state, ensuring system sealing, and calibrating all sensors and flow meters.

[0037] In step c1), when the first feedforward control model is generated through data fitting, the fitting formula is constructed based on the valve flow equation in fluid mechanics, and the expression of the first feedforward control model is

[0038] In the formula, is the density of hydrogen gas at and the corresponding gas temperature.

[0039] is the flow coefficient, which is a function of the valve opening and pressure ratio , denoted as,

[0040] wherein, is a fitting constant obtained by regression analysis of the collected experimental data using the non-linear least squares method.

[0041] It should be noted that in practical applications, the flow coefficient is not a constant, but is related to the type of valve, Reynolds number (related to flow and viscosity), etc. To simplify and improve accuracy, the embodiment is expressed as a function of the valve opening and pressure ratio , as shown above. The final expression of the first feedforward control model is,

[0042] To reduce the computational burden of the controller, the calculation results of the above formula can be pre-calculated to form a three-dimensional query table stored in the memory of the controller. The three input dimensions of the query table are: , , , and the output is the corresponding feedforward valve opening . In real-time control, the controller quickly obtains the feedforward opening value from the query table by linear interpolation.

[0043] An optional implementation, the mass flow meter directly measures the volume flow value under the current working condition. To achieve accurate control of the hydrogen mass flow, the volume flow is compensated and converted to the mass flow under standard conditions . The compensation process is carried out in real time to eliminate the measurement error caused by the change in gas temperature.

[0044] Specifically, the mass flow meter reading after real-time temperature compensation is obtained by the following steps.

[0045] a2) Collect the instantaneous volume flow value of the working condition by the mass flow meter, and collect the absolute pressure of the gas within the preset range of the mass flow meter and the thermodynamic temperature of the gas by corresponding sensors, respectively.

[0046] b2) According to the absolute pressure and the thermodynamic temperature of the gas, the density of hydrogen under the current working condition is calculated using the real gas state equation.

[0047] ​Preferably, the calculation is performed using the modified Benedict-Webb-Rubin (MBWR) equation of state or a simplified fitting formula referenced to the NIST REFPROP database. The present embodiment uses an equation of state that includes a compressibility factor :

[0048] wherein is the density of hydrogen at the current operating condition, is the molar mass of hydrogen, is the ideal gas constant, is the compressibility factor of hydrogen at the pressure and temperature , the value of which is obtained by interpolation from a Z-P-T relationship data table preset in the test controller.

[0049] c2) multiplying the operating volume flow rate instantaneous value by the hydrogen density at the current operating condition to obtain a mass flow meter reading that is real-time compensated for temperature .

[0050] The present embodiment effectively eliminates the influence of density changes caused by changes in gas temperature and pressure on flow measurement by the above real-time compensation method, accurately converts the measurement value of the flow meter from the operating volume flow rate to the standard mass flow rate. This ensures that the flow feedback signal received by the control system is always the mass flow rate reflecting the true physical quantity throughout the charging and discharging process, especially during the temperature fluctuation stage, such as the temperature rise at the beginning of charging and the temperature drop at the beginning of discharging, thereby achieving high-precision "uniform speed hydrogen charging" control and improving the accuracy and reliability of the test results.

[0051] Figure 2 is a flowchart for generating the final control opening degree during the test process, based on the first feedforward control model and temperature compensation implementation, including the following steps.

[0052] S1, real-time acquisition of the current high-pressure gas tank pressure value and the internal pressure value of the measured gas cylinder , and acquisition of the operating volume flow rate instantaneous value, absolute pressure of the gas, and thermodynamic temperature of the gas at the current corresponding time.

[0053] S2, inputting the high-pressure gas tank pressure value , the internal pressure value of the measured gas cylinder , and the target mass flow rate to the first feedforward control model to calculate the first feedforward valve opening degree.

[0054] The output of the first feedforward control model is the theoretical valve opening degree required to reach the target mass flow rate , i.e. the first feedforward valve opening degree .

[0055] S3, based on the current corresponding time of the working condition volume flow instantaneous value, gas absolute pressure, gas thermodynamic temperature, through temperature real-time compensation calculation to get the gas pipeline mass flow reading .

[0056] S4, with the target mass flow As the set value, the gas pipeline mass flow reading As the process variable, through the anti-integral saturation PID controller to calculate the first opening correction.

[0057] The gas pipeline mass flow reading And the target mass flow Comparison, get flow deviation :

[0058] The flow deviation Input to an anti-integral saturation PID controller. The PID controller calculates the output first opening correction according to the following formula :

[0059] In the formula, , , The proportional gain, integral gain and differential gain, respectively.

[0060] S5, add the first feedforward valve opening and the first opening correction, and the sum is the final control opening of the gas proportional valve.

[0061] The final control opening , according to the value to control the opening of the proportional valve on the gas pipeline.

[0062] In an optional embodiment, based on the physical parameters of the gas cylinder and the charging and discharging rate, a lumped parameter temperature model is established to predict the average temperature or key point temperature of the gas cylinder in real time. The test controller uses the predicted temperature to correct the target flow set value , for example, when the predicted temperature approaches the 85°C upper limit, the target flow is reduced in advance and smoothly, rather than being reduced suddenly after the over-temperature alarm, to achieve safer "uniform speed" control.

[0063] Specifically, the test controller is also configured to perform a target mass flow control process based on the measured gas cylinder temperature field prediction, specifically including the following processes.

[0064] a3) Based on the physical parameters of the gas cylinder under test and real-time test data, the internal temperature of the gas cylinder under test is estimated in real time using a pre-built internal temperature field prediction model. The predicted model for the internal temperature field of the gas cylinder is expressed as follows:

[0065] in, and These represent the mass of the gas inside the gas cylinder and the mass of the inner liner, respectively. The rate of change of the average temperature of the measured gas cylinder. The specific heat capacity at constant pressure of hydrogen. The specific heat capacity of the inner liner material. The rate of energy change due to gas flow. This represents the heat loss rate of the tested gas cylinder to the environment.

[0066] The input parameters for the temperature field prediction model include: Gas cylinder physical parameters, gas cylinder volume Specific heat capacity of inner liner material The equivalent thermal conductivity of the composite material layer and wall thickness These parameters are stored as constants in the test controller; Real-time test data, current inflation mass flow rate Current pressure inside the gas cylinder And the ambient temperature inside the gas cylinder testing environment chamber. ; Gas thermophysical property data, specific heat capacity at constant pressure of hydrogen Joule-Thomson coefficient These data are stored in the test controller as data tables related to pressure and temperature.

[0067] Considering the computational load of real-time control, the lumped parameter method is preferred for establishing the temperature field prediction model. This model treats the gas cylinder and its internal gas as a whole, using the average temperature... To describe its thermal state.

[0068] Rate of energy change due to gas flow The calculation formula is as follows:

[0069] In the formula, The temperature of the injected gas is controlled by the hydrogen preheating and precooling unit. For gas density, The term characterizes the temperature change caused by the Joule-Thomson effect.

[0070] Heat loss rate of the tested gas cylinder to the environment The calculation can be simplified using Newton's law of cooling:

[0071] In the formula, The equivalent convective heat transfer coefficient, This represents the outer surface area of ​​the gas cylinder.

[0072] The test controller predicts the average temperature trend of the gas cylinder over a future period by solving the differential equations of the temperature field prediction model in real time. .

[0073] b3) Predict the temperature The target mass flow rate during inflation is compared with a preset temperature safety threshold, and the result is used to dynamically adjust the flow rate based on the comparison. This includes: if the predicted temperature If the temperature is below the minimum safe temperature threshold, maintain the original target mass flow rate. If the predicted temperature... If the temperature is not lower than the maximum safe temperature threshold, set the target flow rate to zero; otherwise, adjust the flow rate according to the predicted temperature. Reduce the target quality flow rate according to preset rules.

[0074] The preset rule can be a proportional function, for example:

[0075] in, The corrected target mass flow rate, The original target mass flow rate, The minimum safe temperature threshold, The maximum safe temperature threshold. The attenuation coefficient is between 0 and 1.

[0076] c3) The corrected target mass flow rate is input as a setpoint to the feedforward control model and PID controller to generate the final control opening of the inflation proportional valve.

[0077] The test controller is also configured to generate the final control opening of the venting proportional valve during the venting process through a second feedforward control model, temperature compensation, and a PID controller. The second feedforward control model is established in the same way as the first feedforward control model described above, and its model parameters are obtained independently through calibration experiments during the venting process. Temperature compensation and PID control are the same as in the inflation phase and will not be described further here.

[0078] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A vehicle-mounted hydrogen cylinder fatigue life testing system, characterized in that, The test control system comprises a gas source subsystem, a high-pressure boosting and storage subsystem, a test execution subsystem, and a monitoring and control subsystem. The gas source subsystem is configured to transmit the gas provided by a gas source and the gas recovered from a test gas cylinder to the high-pressure boosting and storage subsystem after equalization. The high-pressure boosting and storage subsystem comprises a high-pressure compressor set connected to the gas source subsystem via a pipeline and a high-pressure gas storage tank connected to the high-pressure compressor set. The test execution subsystem comprises a test gas cylinder arranged in a gas cylinder test environment chamber, a hydrogen preheating and precooling unit arranged on a charging pipeline, and proportional valves arranged on the charging pipeline and a discharging pipeline, respectively. The monitoring and control subsystem comprises a flow monitoring unit arranged on the charging pipeline and the discharging pipeline to monitor the flow rate of the gas flowing through the pipelines in real time, a pressure monitoring unit to monitor the pressure of the high-pressure gas storage tank and the internal pressure of the test gas cylinder in real time, and a test controller electrically connected to the flow monitoring unit, the pressure monitoring unit, and the proportional valves. The test control system is configured to calculate a first feedforward valve opening degree based on the pressure of the high-pressure gas storage tank and the internal pressure of the test gas cylinder during the charging process, use the charging pipeline mass flow rate reading after real-time temperature compensation as feedback, calculate a first opening degree correction amount by a PID controller, and finally superimpose the first feedforward valve opening degree and the first opening degree correction amount to generate a final control opening degree of the charging proportional valve.

2. The fatigue life test system of on-board hydrogen cylinder according to claim 1, characterized in that, The gas source subsystem comprises a gas source, a gas unloading column, a recovery compressor, a low-pressure gas storage tank, and a medium-pressure gas storage tank. The gas source is connected to the low-pressure gas storage tank inlet via a first path of the gas unloading column and to the medium-pressure gas storage tank inlet via a second path of the gas unloading column. The low-pressure gas storage tank inlet is also connected to the test gas cylinder via a discharging pipeline, and the low-pressure gas storage tank outlet is connected to the medium-pressure gas storage tank inlet via a recovery compressor.

3. The fatigue life test system of on-board hydrogen cylinder according to claim 1, characterized in that, The medium-pressure gas storage tank outlet is connected to the high-pressure compressor set of the high-pressure boosting and storage subsystem via a pipeline. When the gas source pressure is higher than a preset pressure, the gas source gas is directly delivered to the high-pressure boosting and storage subsystem by equalization, otherwise the recovered gas and the low-pressure gas source gas are delivered to the high-pressure boosting and storage subsystem by equalization after being increased by the recovery compressor. In the system calibration stage, the experimental parameter matrix covering the working range of the test system is set, including: in the working pressure range of the high-pressure gas tank, multiple different pre-valve pressure points are selected ; in the expected pressure range of the tested gas cylinder, multiple different post-valve pressure points are selected ; in the effective opening range of the proportional valve, multiple different opening points are selected ; For each combination in the experimental parameter matrix , a steady state flow data acquisition operation is performed, including adjusting the system pressure to stabilize the pre-valve pressure at , the post-valve pressure at , adjusting the proportional valve to the specified opening , and after the gas flow stabilizes, collecting and recording the mass flow meter reading at that time, real-time compensated for temperature ; Based on all the data points collected a first feedforward control model is generated by data fitting.

4. The fatigue life test system of on-board hydrogen cylinder according to claim 3, characterized in that, The test controller is further configured to close the first path of the gas unloading column and open the second path when the gas source pressure is higher than a preset pressure threshold, and to open the first path of the gas unloading column and close the second path when the gas source pressure is lower than the preset pressure threshold. wherein to be at and the density of hydrogen at the corresponding gas temperature; is the flow coefficient, which is a function of the valve opening and pressure ratio and is represented as, wherein are fitting constants obtained by regression analysis of the collected experimental data using a non-linear least squares method.

5. The fatigue life test system of on-board hydrogen cylinder according to claim 4, characterized in that, Temperature real-time compensated mass flow meter readings Obtained by the following steps: The first feedforward control model is constructed based on the dynamic relationship between the mass flow rate and the proportional valve opening degree, the pressure before the valve, and the pressure after the valve. The first feedforward control model is established through experiments, including the following steps: When the first feedforward control model is generated by data fitting, the fitting formula is constructed based on the valve flow equation in fluid mechanics, and the expression of the first feedforward control model is The instantaneous volume flow rate of the working condition is collected by a mass flow meter, and the absolute pressure and thermodynamic temperature of the gas within the preset range of the mass flow meter are collected by corresponding sensors, respectively. According to the absolute pressure and the thermodynamic temperature of the gas, the density of the hydrogen gas under the current working condition is calculated by using the real gas state equation; The working condition volume flow rate instantaneous value is multiplied by the hydrogen density under the current working condition to obtain a mass flow meter reading compensated in real time by temperature .

6. The fatigue life test system of on-board hydrogen cylinder according to claim 5, characterized in that, The first feedforward valve opening degree is calculated by a first feedforward control model based on the pressure of the high-pressure gas tank and the internal pressure of the measured gas cylinder, and the final control opening degree of the inflation proportional valve is generated by superimposing the first feedforward valve opening degree and a first opening degree correction amount calculated by a PID controller using the inflation pipeline mass flow rate reading compensated in real time by temperature as feedback, specifically including: Real-time acquisition of current high-pressure gas tank pressure value and the measured gas cylinder internal pressure value and the current corresponding time instant of the inflation pipeline working condition volume flow instantaneous value, gas absolute pressure, gas thermodynamic temperature; The high-pressure gas tank pressure value , the measured gas cylinder internal pressure value , and the target mass flow are input to the first feedforward control model to calculate the first feedforward valve opening degree; Based on the current corresponding time's working condition volume flow instantaneous value, gas absolute pressure, gas thermodynamic temperature, the gas charging pipeline mass flow reading is calculated through temperature real-time compensation ; The target mass flow rate The aeration line mass flow rate reading The first opening degree correction is calculated by a PID controller with anti-integral saturation The first feedforward valve opening degree and the first opening degree correction are added, and the sum is the final control opening degree of the inflation proportional valve.

7. The fatigue life test system of on-board hydrogen cylinder according to claim 6, characterized in that, The test controller is also configured to execute a target mass flow control process based on a measured gas cylinder temperature field prediction, specifically including: Based on the physical parameters and real-time test data of the measured gas cylinder, the internal temperature of the measured gas cylinder is estimated in real time through a pre-constructed internal temperature field prediction model of the gas cylinder ; the internal temperature field prediction model of the gas cylinder is represented as, wherein, and respectively are the mass of the gas inside the measured cylinder and the mass of the liner, is the rate of change of the average temperature of the measured cylinder, is the specific heat capacity of hydrogen at constant pressure, is the specific heat capacity of the liner material, is the rate of change of energy due to gas flow, is the rate of heat loss from the measured cylinder to the environment; comparing the predicted temperature with preset temperature safety thresholds and dynamically modifying the target mass flow of the gassing process in a feedforward manner depending on the comparison result , including: if the predicted temperature is less than a minimum temperature safety threshold, maintaining the original target mass flow, if the predicted temperature is not less than a maximum temperature safety threshold, setting the target flow to zero, otherwise reducing the target mass flow according to the predicted temperature in a preset rule; The corrected target mass flow is input as a set value to the feedforward control model and the PID controller to generate the final control opening degree of the inflation proportional valve.

8. The fatigue life test system of on-board hydrogen cylinders according to claim 1, characterized in that, The test controller is also configured to calculate a second feedforward valve opening degree by a second feedforward control model based on the internal pressure of the measured gas cylinder and the pressure of the low-pressure gas tank during the deflation process, and to generate the final control opening degree of the deflation proportional valve by superimposing the second feedforward valve opening degree and a second opening degree correction amount calculated by a PID controller using the deflation pipeline mass flow rate reading compensated in real time by temperature as feedback; the deflation proportional valve refers to a proportional valve arranged on the deflation pipeline.

9. The fatigue life test system of on-board hydrogen cylinder according to claim 8, characterized in that, The second feedforward control model is established in the same way as the first feedforward control model in claim 3 or 4.

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