Effect of direct water injection on combustion and emissions characteristics of marine diesel engines

Abstract

In this study, the effect of direct water injection (DWI) was investigated on the performance of marine diesel engine based on the three-dimensional simulation model. The water injection quantity, temperature and timing were researched on the in-cylinder pressure and temperature, indicated power and NOx emissions. Then, the DWI strategies were compared with the exhaust gas recirculation (EGR). The results showed that the in-cylinder pressure, temperature, indicated power and NOx emissions decrease with increasing of water quantity. Reductions in NOx emissions up to 55.6% were obtained after applying DWI to the engine at the compression stroke. The water injection temperature has a little effect on the combustion and emissions of marine engine. The indicated power decreased when the water injection timing in the compression stroke. However, the indicated power increased when the water injection timing in the late combustion phase. The water injection timing in the compression stroke has more potential in reduction NOx emissions. The NOx emissions with water injection in the compression stroke decreased by 40% compared to the value with water injection in the later combustion phase. The ability of DWI and EGR were researched on the solve the trade-off between power and NOx emissions. The results showed that the DWI strategy can reduce NOx emissions at the higher indicated power compared with the results of EGR.