Abstract
Knowing the process of generating exhaust emissions and the determination of influential parameters are important factors in improving two-stroke slow-speed marine engines, particularly for further reductions in fuel consumption and stringent regulations on the limitation of nitrogen oxide emissions. In this article, a model of a marine low-speed two-stroke diesel engine has been developed. Experimental and numerical analyses of the nitrogen monoxide formations were carried out. When measuring the concentration of nitrogen oxides in the exhaust emissions, the amount of nitrogen dioxide (NO2) is usually measured, because nitrogen monoxide is very unstable, and due to the large amount of oxygen in the exhaust gases, it is rapidly converted into nitrogen dioxide and its amount is included in the total emission of nitrogen oxides. In this paper, the most significant parameters for the formation of nitrogen monoxide have been determined. Model validation was performed based on measured combustion pressures, engine power, and concentrations of nitrogen oxides at 50% and 75% of maximum continuous engine load. The possibilities of fuel consumption optimization and reduction in nitrogen monoxide emissions by correcting the injection timing and changing the compression ratio were examined. An engine model was developed, based on measured combustion pressures and scavenging air flow, to be used on board by marine engineers for rapid analyses and determining changes in the concentration of nitrogen oxides in exhaust emissions. The amount of nitrogen oxide in exhaust emissions is influenced by the relevant features described in this paper: fuel injection timing and engine compression ratio. The presented methodology provides a basis for further research about the simultaneous impact of changing the injection timing and compression ratio, exhaust valve opening and closing times, as well as the impact of multiple fuel injection to reduce consumption and maintain exhaust emissions within the permissible limits.
Highlights
The impact of exhaust emissions on the environment and air pollution from ships has attracted a great deal of attention in the last few decades, especially from 1995 until today.Due to the properties of the combustion process typical of marine two-stroke slow-speed engines and the use of heavy fuels, merchant fleets release a significant amount of nitrogen oxides, NOx
When measuring the concentration of nitrogen oxides in the exhaust emissions, the amount of nitrogen dioxide (NO2 ) is usually measured, because nitrogen monoxide is very unstable, and due to the large amount of oxygen in the exhaust gases, it is rapidly converted into nitrogen dioxide and its amount is included in the total emission of nitrogen oxides
The in-cylinder pressure was successfully compared with experimental measurements, indicating that the proposed computational fluid dynamics (CFD) approach can simulate the compression/expansion process with a good degree of accuracy. These results provide interesting information to improve two-stroke engines because the scavenging process plays a crucial role in pollution levels, performance, and efficiency
Summary
The impact of exhaust emissions on the environment and air pollution from ships has attracted a great deal of attention in the last few decades, especially from 1995 until today. Due to the properties of the combustion process typical of marine two-stroke slow-speed engines and the use of heavy fuels, merchant fleets release a significant amount of nitrogen oxides, NOx. Knowledge of the generation, quantity and impact of exhaust emissions on human health and the environment is an important factor in the improvement of marine engines, and for the adoption of legislation to limit the emission of harmful substances. Emissions of pollutants from ships in international transport in the European Union Emissions of pollutants from ships in international transport in the. Eu2 of 29 ropean Union (Baltic Sea, North Sea, Northeast Atlantic, Mediterranean and Black Sea) in 2000 were estimated at 3.3 million tons of nitrogen oxides (NOx). 2030, emissions of from pollutants showed an increase of about 40–50% This that waters in 2030,will emissions of pollutants from from international maritime transport inmeans.
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