| Currently,hydrogen energy has become a powerful grip to achieve the goal of carbon peak and carbon neutral in China due to its advantages of high energy density and non-polluting use.Among them,liquid hydrogen has become the optimal form of hydrogen mass storage or long-distance transportation with its ideal mass hydrogen storage density and volume hydrogen storage density.However,there is less research on the evaporation and release of liquid hydrogen in a dynamic state,especially in road transportation conditions,and in road transportation mostly in crowded areas,if the timing and location of release are not properly chosen,it may pose a threat to people’s life and property safety.Therefore,it is very important to carry out the research on the release characteristics of liquid hydrogen storage tanks based on dynamic evaporation prediction.In this paper,the evaporation and release characteristics of liquid hydrogen under road transportation conditions are studied,including the establishment of a computational fluid dynamics model for dynamic evaporation of liquid hydrogen and a solid model for a 40-foot ISO liquid hydrogen tank,analysis and study of the effects of different factors on the tank pressure and nondestructive storage time of liquid hydrogen,and discussion of the changes in tank pressure under actual road driving conditions.The main research works and innovations of the dissertation are as follows.(1)A computational hydrodynamic model for dynamic evaporation of liquid hydrogen and a solid model for a 40-foot ISO liquid hydrogen tank were established.The VOF method,the standard k-ε model and the Hertz-Knudsen formula are used to capture the fluid motion patterns and calculate the phase variables based on the set of basic equations of fluid mechanics.After comparing with the experimental data of NASA’s liquid hydrogen spherical tank self-pressurization,the calculation results of the model have good consistency and passed the validity verification.After determining the tank size and structure,the heat transfer of the outer tank,support structure,insulation layer and insulation structure for the inner tank was analyzed,from which the heat leakage power of the inner tank in the tank was determined,and certain simplifications were made to the tank to finally form a solid model of the 40-foot ISO liquid hydrogen tank.(2)The effects of three types of factors on the evaporation of the liquid hydrogen tank were analyzed and studied.The factors such as filling rate,shaking and heat leakage were analyzed and determined to have a great influence on the evaporation of liquid hydrogen tank,and a total of seven simulation experiments in four categories were designed to investigate the influence of different factors and their combinations on the evaporation of liquid hydrogen in the tank by comparing the relationship of temperature,pressure and evaporated hydrogen mass with time under different working conditions.The results show that the high filling rate can prolong the tank box non-destructive storage time,and the shaking condition can affect or even destroy the thermal stratification structure to a certain extent,but it also raises the fluid internal energy level,instead of increasing the growth rate of gas phase space pressure.(3)The dynamic evaporation of the liquid hydrogen tank under the actual road transportation conditions was investigated.According to the driving conditions of the semi-trailer,the”city working cycle” and ”high speed working cycle” were selected as the actual road driving conditions of the liquid hydrogen trailer,and the simulation experiments were carried out under different filling rates and heat leakage scales.The results show that the repeated starting and stopping of the vehicle on the city road will increase the pressure increase rate,but the small shaking at high speed can reduce the pressure increase rate of the liquid hydrogen tank at rest by12%;avoid the high speed and high acceleration of the vehicle as much as possible,otherwise it may cause the sudden pressure increase.(4)Provide suggestions for the road transportation of liquid hydrogen as well as the release while transporting to reduce the frequency of liquid hydrogen releases and losses,and to further improve the safety and efficiency of large-scale liquid hydrogen storage and transportation. |
