Study On Dynamic Characteristics Of Hydrogen Energy Ship Fuel Filling Process

In recent years,with the improvement of ecological environment protection awareness and the continuous fermentation of energy shortage crisis,the low-carbon transformation of the shipbuilding industry is imminent.With its unique advantages of efficient energy utilization and zero pollution,hydrogen fuel cell technology has great potential in promoting the deepening of green shipping concept and realizing the " double carbon goal " in the future.However,the problem of hydrogen filling and storage is still one of the bottlenecks restricting the industrial application of fuel cell ships.The completion of the hydrogenation operation of the ship’s high-pressure hydrogen storage system in a short time will cause a sharp increase in the temperature in the hydrogen storage bottle,and the high temperature will lead to a decrease in the hydrogen storage density,which will affect the ship’s endurance.At the same time,it will change the mechanical properties of the fiber composite material on the outer wall of the hydrogen storage bottle,causing unpredictable consequences such as hydrogen leakage and explosion.At present,the standard specification of ship hydrogenation is not mature,the production specifications of hydrogen storage bottle manufacturing enterprises are different,and the operation of hydrogenation station is not streamlined.How to realize rapid,efficient and large-scale filling of ship hydrogen fuel and improve the safety of hydrogen energy application in ships is an urgent problem to be solved.Therefore,it is of great theoretical significance and practical value to carry out simulation research on rapid refueling of hydrogen energy ship fuel and optimize hydrogenation control strategy.Based on the CFD analysis software Fluent,the fluid-solid coupling method is used in this thesis to simulate the rapid hydrogenation process of ships.It is devoted to exploring the temperature distribution and temperature rise evolution law in hydrogen storage bottles,providing a theoretical basis for the design of ship hydrogenation schemes,which is of great significance for the formulation of relevant specifications and standards and the safe application of hydrogen energy in ships.The main research results include:(1)In order to explore the influence of overheating of high-pressure hydrogen storage bottles in hydrogenation operation,the simulation results of rapid filling process of different types of hydrogen storage bottles are discussed.First of all,through the analysis of the thermodynamic behavior of the filling process of the hydrogen storage system,it is determined that the phenomenon of hydrogen temperature rise is caused by many factors,such as the heat released by the hydrogen compression effect in the hydrogen storage bottle,the heat produced by the hydrogen Joule-Thomson effect,the conversion of hydrogen kinetic energy into internal energy and the heat exchange between the bottle and the environment.Secondly,on this basis,the construction of 140 L marine hydrogen storage bottle model,the setting of boundary conditions and related verification work are completed,and the rationality and accuracy of the model are determined.The simulation results show that rapid hydrogenation causes the gas temperature to rise rapidly and exceed the relevant standard threshold.The temperature distribution in the bottle is not uniform,and a local high temperature area appears at the tail of the bottle.Through the hydrogen flow trace,it can be seen that the temperature distribution is closely related to the gas flow,and the hydrogen pressure at the bottom of the bottle is the main reason for the temperature rise.The hydrogen temperature began to decrease after entering the stable stage,while the wall temperature of the bottle continued to rise to about 350 s and reached the peak.Due to the high specific heat capacity and low thermal conductivity of the lining HDPE material of the type IV hydrogen storage bottle,the heat is accumulated,resulting in poor heat dissipation capacity.The temperature rise is much higher than that of the type III bottle,and the harm of safe hydrogenation is greater.Compared with the nominal working pressure of 35 MPa hydrogen storage bottle,the temperature rise of 70 MPa ship hydrogen storage system is worse.(2)The effects of hydrogenation conditions and hydrogen storage bottle structure design on the temperature rise of ship rapid filling process are studied.Optimizing the structural design of ship hydrogen storage bottles(such as inlet pipe diameter,aspect ratio,water volume,bottle wall thickness,etc.)can affect the hydrogen jet and swirl flow,thereby improving the temperature distribution in the bottle.Among them,the inlet pipe diameter and the wall thickness of the bottle have little effect on the temperature rise of the hydrogen storage bottle and the length-diameter ratio design has a great influence.The gas flow in the320 L ultra-large volume bottle is almost not constrained by the geometric shape of the hydrogen storage bottle,and the increase of the actual heat dissipation area and volume ratio is beneficial to heat dissipation.Different hydrogenation conditions and ship energy demand can adopt targeted hydrogen storage bottle design to maximize its inhibition of temperature rise.The influence of initial pressure on the final gas temperature rise in the filling parameter conditions is approximately linearly decreasing,and the increase of inlet temperature and filling rate will lead to a significant increase in temperature rise.The hydrogenation station can control the temperature by controlling the inlet temperature and hydrogenation time.(3)An effective hydrogenation temperature control strategy for 70 MPa ship hydrogen storage system is proposed.During the filling process of 70 MPa high-pressure hydrogen storage bottle,the temperature rise peaks of aluminum alloy liner,CFRP and GFRP appeared at about 294 s,296 s and 313 s,respectively,and the peaks are 68.26 °C,68.24 °C and66.85 °C,respectively,which exceeded the temperature rise threshold of relevant filling standards.Based on the temperature variation law of the 70 MPa hydrogen storage bottle in the hydrogenation stage and the stable stage,combined with the influence of different hydrogenation conditions and environmental factors on the temperature rise,a hydrogenation flow control strategy,a hydrogenation pre-cooling strategy,and a hydrogen pre-cooling and boost rate coupling filling strategy are proposed.The hydrogenation scheme coupled with the slow-fast boost mode and the segmented pre-cooling can improve the pre-cooling temperature level,save equipment investment and pre-cooling energy consumption under the premise of ensuring the hydrogenation time,thereby saving the filling cost.