Abstract
This work analyzes NOx reduction in a marine diesel engine using ammonia injection directly into the cylinder and compares this procedure with water injection. A numerical model based on the so-called inert species method was applied. It was verified that ammonia injection can provide almost 80% NOx reduction for the conditions analyzed. Furthermore, it was found that the effectiveness of the chemical effect using ammonia is extremely dependent on the injection timing. The optimum NOx reduction was obtained when ammonia is injected during the expansion stroke, while the optimum injection timing using water is near top dead center. Chemical, thermal, and dilution effects of both ammonia and water injection were compared. The chemical effect was dominant in the case of ammonia injection. On the other hand, water injection reduces NOx through dilution and, more significantly, through a thermal effect.
Highlights
Nowadays, diesel engines rule the transportation sector and power most of the ships in the world
Results about nitrogen oxides (NOx) reduction are exposed and results obtained from the artificial inert species method
The ammonia injection took place 58.4◦ CA ATDC. This value was chosen because it provides the maximum NOx reduction, as will be shown below
Summary
Diesel engines rule the transportation sector and power most of the ships in the world. The disadvantages of SCR are its price, poor durability of catalysts, and deposition of particulate on the catalyst These disadvantages are not present in SNCR, but this procedure is limited to a narrow temperature range with optimal temperatures that are much higher than those characteristic of flue gas from diesel engines [10]. Comprehensive investigations have been reported about SNCR analyzing parameters such as temperature, the molar ratio (NH3/NO) [20], residence time, oxygen level, initial NOx, combustibles, and so on [21,22], verifying that the most important factor for NOx reduction is the temperature Based on this result, Miyamoto et al [23] proposed to reduce NOx emissions by injecting ammonia or urea directly into the cylinder.
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