Simulation Research on the Injection Strategy of a Diesel-Ammonia Dual-Fuel Marine Engine

Currently, most ships still rely on fossil fuels as themain sourcefor marine engines. However, diesel as a fuel for marine engines isno longer sufficient to meet the economic requirements of shippingand emission restrictions imposed by regulations as a result of thedepletion of fossil fuels and the pollution generated by their burning.This research examined the viability of employing hydrogen-carryingfuel ammonia (NH3) in marine engines to develop a low-carboncombustion technology, to address the carbon emission problem of marinediesel engines. The results demonstrate that a greater proportionof ignition fuel must be injected into the burning of ammonia dueto its higher ignition energy requirements. And ammonia has a highevaporation rate, so it is important to properly extend the injectionduration to lower the combustion rate and keep the maximum explosionpressure in the cylinder under control. If the injection durationof the original engine's diesel mode is maintained in dual-fuelmode, the explosion pressure in the cylinder can increase by morethan 5 MPa, exceeding the limit of the original engine. However, byextending the original engine duration, the maximum explosion pressurereturned to the original engine level. The starting point of the in-cylindercombustion can be efficiently regulated by changing the injectiontiming. Under typical injection intervals, the heat released rate(HRR) curve shifted with ammonia injection time, and rough combustionoccurred only when the injection interval between the ignition fueland ammonia was too short. According to the simulation, with all otherconditions held constant, the optimal fuel injection strategy maintainsthe in-cylinder pressure of the engine at the diesel engine'soriginal level in the dual-fuel mode. Additionally, it reduced carbonemissions by over 90% and NOx emissions by approximately 70% comparedwith the original diesel engine.

Automated summary

Currently, most ships still rely on fossil fuels as the main source for marine engines. However, diesel as a fuel for marine engines is no longer sufficient to meet the economic requirements of shipping and emission restrictions imposed by regulations. This research examined the viability of employing hydrogen-carrying fuel ammonia (NH3) in marine engines to develop a low-carbon combustion technology, to address the carbon emission problem of marine diesel engines.