Influences Of Using Ammonia Fuel On The Power Output And Emissions Of Internal Combustion Piston Engines

The rapid development of internal combustion engine(ICE)has brought great changes to people’s lives and promoted the development of society.However,fossil fuel has caused serious environmental problems and intensified energy crisis.Ammonia is not only a kind of energy storage medium,but also a hydrogen carrying clean fuel which can be made from renewable energy.Ammonia only produces nitrogen and water under complete combustion.As a clean alternative fuel for internal combustion engine,ammonia has a bright future.For this reason,this paper focuses on two technical schemes of ammonia as the fuel of internal combustion engine.The first one is mixing ammonia with combustion promoter to reduce CO2 emissions.In this paper,the influence of different ammonia ignition modes is studied,and it is pointed out that ammonia is suitable for homogeneous charge compression ignition(HCCI).By analyzing the ignition conditions of ammonia fuel,it is found that the compress ratio of internal combustion engine needs to be more than 52 to reach the ignition temperature of ammonia,and ammonia needs to be mixed with combustion promoter.The combustion and emission characteristics of several common fuels blended with ammonia were investigated,propane blended with ammonia produces the highest combustion heat and the lowest carbon dioxide emission when the volume of gas and air is constant.Considering combustion characteristics,emission characteristics and energy density,propane is the best choice of combustion promoter.In addition,the influence of fuel blending with ammonia on engine power and the difference of different fueling modes of ammonia were analyzed.Gas phase ammonia injection will reduce the output power of engine.Blending with ammonia has the greatest influence on propane among listed fuel.When the ammonia content reaches 100%,the output power of engine will be reduced by 20.8%.Liquid phase fueling mode can improve the output power of the engine compared with gas phase fueling mode.For different fuels,the output power can be increased by 2.0%-2.5%for each 10%increase of ammonia blending ratio.However,liquid-phase ammonia injection will decrease the gas temperature in the cylinder and increase the compression ratio required for compression ignition,which has a negative impact on ammonia ignition.Finally,propane was selected as combustion promoter and a small amount of diesel was used for igniting.The reliability of ignition can be guaranteed without changing the compression ratio of commercial engines.Ammonia content can be increased to nearly 100%at room temperature and 20%-30%at-40℃.The other roadmap is a proposed on-board hydrogen generation system based on liquid ammonia using engine exhaust.Ammonia was cracked partially into hydrogen,then the hydrogen was used as combustion promoter.When the cracking temperature is 750K,the cracking ratio is 100%,and the energy consumption of vehicle hydrogen supply system accounts for 68.5%of the exhaust heat.In this scheme,the exhaust gas heat can meet the heat consumption of ammonia gasification and cracking.