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Abstract:The authors applied one-dimensional (1-D) simulation and 3-D Computational Fluid Dynamics (CFD) simulation to evaluate the potential of in-cylinder control methods on a low-speed 2-stroke marine engine to reach the International Maritime Organization (IMO) Tier 3 NO x emissions standards. Reducing the combustion temperature is an important in-cylinder measure to decrease NO x emissions of marine diesel engines. Miller-cycle and Exhaust Gas Recirculation (EGR) are effective methods to reduce the maximum combustion temperature and accordingly decrease NO x emissions. The authors' calculation results indicate that with a combination of 2-stage turbocharging, a mild Miller-cycle and 10% EGR rate, the NO x emissions can be decreased by 48% without the increased Specific Fuel Oil Consumption (SFOC) penalties; with a medium Miller-cycle and 10% EGR, NO x can be decreased by 56% with a slight increase of SFOC; with a medium Miller-cycle and 20% EGR, NO x can be decreased by 77% and meet IMO Tier 3 standards, but with the high price of a considerable increase of SFOC. The first two schemes are promising to meet IMO Tier 3 standards with good fuel economy if other techniques are combined.

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Abstract:Using low price heavy fuel oil (HFO) in high-speed diesel engines is a practical way to reduce running costs. However, most high-speed diesel engines' fuel systems and combustion systems cannot adapt to HFO. This causes the problem of deterioration of combustion performance. In order to solve this problem, the authors have modified the fuel injection system and combustion system of a high-speed diesel engine to use HFO. In addition, reducing the viscosity of HFO is necessary before it is fed into the engine. Because heating apparatus are not feasible for high-speed engine users, light diesel was blended with HFO to reduce the fuel viscosity. The blend is called HFO-L. Meanwhile, for the purpose of further reducing NO x emissions and soot emissions, water-emulsified HFO-L, named HLW, was used on the research engine. When fueled with 10% water content HLW, the engine presented the same power performance and thermal efficiency as the baseline engine fueled with light diesel. Due to the low price of HFO, the fuel economy of the engine was greatly improved. In addition, fueling HLW led to a considerable reduction of the engine's NO x emissions compared with the baseline engine.