Design Optimization And Electro-Thermal Coupling Characteristics Study Of Ammonia Fuel Cell Engine

“Zero-carbon”transportation is what the“two-carbon”goal should encompass,with a commitment to national end-use carbon emissions of up to 15%.As a clean and efficient secondary energy source,hydrogen is the most ideal“zero carbon”fuel,which will strongly support the realization of carbon neutral carbon peak in China in the future.However,due to its low bulk density,high risk and high price,there are still transportation problems that prevent the industrialization of hydrogen fuel.As a“zero-carbon”hydrogen energy carrier,ammonia storage and transportation is simpler,safer and more stable than hydrogen,and its volumetric hydrogen-carrying capacity exceeds that of liquid hydrogen.Therefore,ammonia storage and transportation can effectively solve the transportation problem of hydrogen and has great potential in energy power.Compared with ammonia internal combustion engine,ammonia fuel cell engine has great advantages in NOx emission and energy conversion efficiency,which is the innovative development direction of next generation fuel cell engine.In view of the strong heat absorption characteristics of ammonia catalytic decomposition reaction,this thesis pioneers the design optimization and electro-thermal coupling characteristics study of ammonia fuel cell engine.By establishing a two-dimensional single-cell model,the effects of structural design optimization,operation condition optimization and different fuel components on the electro-thermal coupling characteristics of ammonia fuel cell engine are described.The main conclusions are as follows:The power density is maximum when the anode thickness is 300μm,and the power density is similar at 400μm anode thickness.The increase of anode thickness starts to decrease the output power of the battery,but it has a certain improvement on the heat dissipation as well as heat distribution of the battery.The larger the electrolyte thickness,the further the oxygen ion transport path,the lower the battery output power and the increased ohmic heat generated.When pure ammonia is used as fuel,the inlet temperature increases,which is beneficial to the output power of the cell and the net heat of the cell increases.When the inlet temperature is 650°C and 700°C,the whole battery’s low temperature area is at the tail of the battery,and when the inlet temperature is 750°C,800°C and 850°C,the whole battery’s low temperature area moves forward to the fuel inlet.As the operating voltage decreases,the net heat of the battery increases and the average temperature of each structure of the battery increases.When the operating temperature is 800°C and the operating voltage is around 0.5 V,the net heat of the battery is zero.As the fuel flow rate increases,the power density continues to increase.When the fuel flow rate increases from1.5 m/s to 2.5 m/s,the increase in power density has been relatively flat,but it can take away more heat from the cell and reduce the cell temperature.Using NH₃:N₂=1:1 as the fuel,the net heat of the cell is zero when the inlet temperature is maintained at 800°C and the cell voltage is around 0.7 V.When NH₃:H₂=1:1（3%water content）was used as fuel,the average temperature of the cell structures was closer and the average rate of the ammonia-catalyzed decomposition reaction reached a stable value when the operating voltage was around 0.5 V.