| Faced with the growing energy shortages,environmental pollution,ecological deterioration,the development of clean and efficient new energy is the only way to solve the above problems.Hydrogen has become the most promising secondary energy of the new century for its advantages of broad source,nonpolluting and high combustion efficiency.Hydrogen fuel cell vehicle is an important application field of hydrogen energy,and is also the focus of research in the new energy automobile industry development plan.High pressure gaseous hydrogen storage,primarily for its technical simplicity,low energy consumption and fast filling-releasing rate,has become the most popular method.On-board compressed hydrogen storage system in the fuel cell vehicles,including high-pressure hydrogen storage cylinder,check valve,globe valve,pressure relief device(PRD)and other critical components,undergoes drastic pressure variation,temperature variation and erosion of hydrogen in the process of refueling,driving and parking,and has the potential risk of leakage or explosion.The traditional hydraulic pressure circulation test method can not simulate all above working conditions,therefore new and reasonable tests must be used to verify the performance of the on-board hydrogen storage system.As an important component of on-board compressed hydrogen storage system durability testing,hydrogen gas cycling test,which is one of the hydrogen storage system type testing explicitly requested by relevant standards suevaluating ch as GTR-HFCV,ISO,SAE,CSA,JARI,has been recommended as an effective method for the expected on-road performance of the compressed hydrogen gas(CHG)cylinder.During the cycling test,the rapid and simultaneous interior pressure and temperature swings and infusion of hydrogen into materials in actual use are simulated,and the evolution law of performance in the process of refueling,driving and parking is reproduced.The hydrogen gas cycling test is just the beginning in the world with scanty test equipment and data,and there is no test system meeting the international standard in China.This research is supported by the National High Technology Research and Development Program of China(863 Program)"High-pressure hydrogen storage,transportation and refueling security technology equipment and application demonstration"(No.2012AA051504)and the national basic research program of China(973 Program)"Damage mechanism of load bearing parts in high pressure gaseous hydrogen at room temperature"(No.2015CB057601).For the technical requirements of high-pressure hydrogen storage system durability testing,problems such as hydrogen temperature control method,system construction,energy-saving operation,are studied in this thesis.The main contents and innovative achievements are as follows:(1)The prediction model of temperature variation during the hydrogen gas cycling test of the compressed hydrogen storage system.Based on the state equation of real hydrogen gas,a thermodynamic model is presented for predicting the temperature variation during the hydrogen gas cycling by using mass conservation equation,energy conservation equation,convective heat transfer equation and heat conduction equation.The computing problem of convective heat transfer coefficient on the cylinder inner wall surface during cycling is solved.The test system with a nominal working pressure of 70MPa is successfully set up for the first time in China for simulating the temperature variation irn the fast refueling and slow discharging process.The critical technical problems such as the design of the combined valve,the seal of the interfaces between combined valve and cylinder and between thermocouples and cylinder,pre-cooling of hydrogen gas,refueling control and data acquisition are resolved.In order to validate the proposed prediction model,the single refueling process,the single discharging process and the whole gas cycling process are respectively simulated by the model,and the experiments in the same processes are conducted by the established test system.Comparisons between experimental and simulation results show that the thermodynamic model has higher precision in the hydrogen gas cycling test of the CHG cylinder.(2)Temperature control method during the hydrogen gas cycling process.Hydrogen temperature variations in the provisions of various current international standards are investigated,and the results show that the current standards have poor enforceability and the temperature easily exceeds the safe limits.In order to set feasible standards,the influence of cylinder type and cylinder size on temperature variation is studied.And the effect of the test operation factors-pressurization rate,discharging flow rate,ambient temperature,hydrogen pre-cooling temperature and circulation mode,on temperature variation is also studied.On the basis of above research results,the temperature control methods for different cylinders during the gas cycling test are proposed,which provide a reference for the drafting of on-board high-pressure hydrogen storage system durability testing.(3)Optimization design method of hydrogen cycling test system.By analyzing the building and operating costs,the optimization strategy of system,which includes high-pressure tank volume and pressure classification,cycling process optimization,compression and pre-cooling energy consumption optimization,is obtained.Considering the hydrogen gas state changes in the process of charging and discharging,pressure control,pre-cooling,compression,a thermodynamic model for the entire hydrogen cycling system is presented based on the proposed temperature prediction model of the CHG cylindbr.Using this model,the hydrogen pressure and temperature variations in all tanks,cylinders,pressure control devices,and the energy consumptions in pre-cooling and re-compress during the hydrogen gas cycling process,are simulated.Based on the established thermodynamic model of hydrogen gas cycling,the proposed optimization strategy of system is executed and analyzed,and is compared with the traditional design method.The results show that the optimal design method is more economic in energy consumption.(4)Construction of the hydrogen cycling test system.The critical technical problems such as high and low temperature environmental chamber design,cycling system control software development and pressurization system design are solved.The hydrogen gas cycling test system for the valves used in hydrogen environment is successfully built for the first time in China.And then the hydrogen gas cycling tests for the cut-off valve,check valve and low pressure cylinder are conducted respectively to verify the functionality of the system.The construction of the system provides experiences for the hydrogen gas cycling test of the CHG cylinder. |
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