The Effect of Air Throttle on Combustion Process and Emission Formation in Marine Lean-Burn Gas Engines (original) (raw)

Enhancing the marine propulsion system's performance is one of the crucial issues that has received noteworthy attention due to the current strict emission legislation. A fundamental improvement without an additional after-treatment system is employing natural gas fuel in lean-burn combustion. Lean combustion may improve the thermal efficiency in a stable condition, but a real ship works in a time-varying inflow on the propeller, and the engine must afford high-efficiency combustion against the fluctuating load. Stable combustion in a lean-burn marine gas engine is guaranteed by installing controllers on the air and the fuel pipes to regulate airfuel ratio and engine speed. The present study aimed to investigate the influence of adding an air throttle during the engine's lower loads and its effectiveness during a time-varying load. A thermodynamics model of spark ignition engine with an imposed constant and transient load is presented. The results revealed that using a throttle in the lower loads may improve the engine fuel consumption and emission formation during steady-state, but, in transient condition, it showed a negligible impact on the brake specific fuel consumption and unburned hydrocarbon emission formation.