Recently imposed regulations by the International Maritime Organization (IMO) include a 16% reduction in Nitric Oxides (NO(x)) emissions between 2000 and 2011 for low-speed large marine Diesel engines, and an 80% reduction by 2016 for the Emission Control Areas (ECAs). Current research efforts for reducing NO(x) in large marine engines consider multiple injection strategies, water addition, Exhaust Gas Recirculation (EGR) and catalytic converters. In the present work, the potential for NO(x) emissions reduction in a large two-stroke marine Diesel engine by means of Direct Water Injection (DWI), as well as intake water addition, is studied using Computational Fluid Dynamics (CFD) simulations. The modeling platform is a modified version of the CFD code KIVA-3V. For a given fuel injection profile, the effect of water mass on NO(x) emissions is first investigated, and compared to a reference case of zero water mass. The results indicate that Direct Water Injection is substantially more effective than intake water addition. Next, a variation of fuel injection profiles (for both techniques), as well as of water injectors' locations (for DWI) is performed; the effects on NO(x) and soot emissions, as well as on Specific Fuel Oil Consumption (SFOC) are quantified. For the cases of unmodified fuel injection, representative results indicate that a reduction in NO(x) of approximately 85% is achieved with DWI, and of 60% with intake water addition, for water mass levels of 50% and 200% of the injected fuel mass, respectively. Under those conditions, SFOC is increased by approximately 4.5% and 2.0%, respectively, accompanied by non-negligible increase in the emitted soot levels. By systematically varying the locations of the water injectors, as well as fuel injection timing, it has been possible to maintain the same levels of NO(x) emissions reduction, with milder penalties in SFOC and soot emissions. The present detailed study suggests that: (a) the 2016 NO(x) emission standards could be met by proper water injection strategies, (b) further improvements in emissions levels and engine performance would be feasible in terms of optimized water and fuel injection, based on rigorous optimization studies.
Computational study of In-cylinder NO(x) reduction in a large marine diesel engine using water injection strategies
2010
10 Seiten, 16 Bilder, 23 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
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