Numerical Simulation Study On Combustion Process Of High-pressure Direct Injection Ammoniadiesel Dual Fuel Marine Low Speed Engine

With the concern of environment protection and the global warming,the low carbon energy will become developing trend of the energy and power industry.The marine low-speed engine as power source of the most sea-goes shipping for its economy and high reliability,which bears the most overseas trade transport working.But the traditional marine low-speed engine uses diesel burning for its power source and the combustion of diesel will brings large amount of CO₂.To solve the CO₂ emission problem during the engine working,the application of ammonia as the fuel of marine low-speed engine becomes the center of people’s attention.This paper investigates the application of the combustion mode of high pressure direct-injected diesel ignite the high pressure direct-injected ammonia.The center diesel spray ignites the ammonia spray injected by surrounding uniform located ammonia injectors.This arrangement has a high flexibility to control the combustion and ignition effect well.To offer the space for arranging the center diesel injector,the single exhaust valve should be adjusted into four exhaust valves.For the diesel spray flame to ignite the ammonia spray,which injected by large nozzle,its spray and flame characteristics are still unknow.The paper firstly researched the development of large nozzle spray and flame.then the model of rapid compression and expansion machine was established.And analyzed the weakness of diesel and ammonia spray in same direction for the dual fuel engine.The spray mode that diesel injector is located in the center and diesel ammonia are injected in opposite direction is taken.Then the ammonia injection timing and direction of domestic made low-speed engine are researched.The result shows that it is easy for the ammonia flame to be quenched after the flame hit the wall.The sensitivity of ammonia flame to temperature is higher than the diesel flame.For the application of ammonia in engine,the ammonia injection earlier can increase the amount of premixed ammonia and increase the indicated thermal efficiency.And three ammonia spray mutual interference in the cylinder center can increase the ammonia combustion rate.The ammonia energy account for diesel can reach the 98%for ammonia-diesel dual fuel engine.