Optimization of Fuel Injection Nozzles for the Reduction of NOx Emissions in Medium-speed Marine Diesel Engines(Diesel Engines, Performance and Emissions, NOx Strategies)

Abstract

Mtmerical simulations and erperimentshave been carried out to investigate the etilect ofjuel itv'ection nozales on the combustion and NOx formation processes in medium-speed marine diesel engines. SPray and combustion phenomena were examined numerically usingFl/RE code. PPZive breakup and Zeldovich modlels were adopted to describe the atomization characteristics and IVCix formation processes. spray visualization erperiment was pecformed in the constant-volume highpressure chamber to verCtv the numerical results on the spray characteristics such as spray angie and spray tip penetration. nme-resolved spray behaviors were captured by high-speed digital camera and analyzed to extract the injbrmation on the spray parameters. Mtmerical analysis oj' juel injection system was also pet:formed to get theprqfiles ctLfitel itv'ection rate, which should be given as an imput datafor the combustion analysis.IVItmerical results were verijied with experitnental clata such as cylinderpressure, R()HR (ZRate ofHleat Releasel and NOx emission. FinalCM the efiZicts qifitel injection nozzles on the enginepel;ibrmance were investigatednumerically to ,find the optimum nozzleparameters such as.fiiel injection angle, nozzle hole diameter and number qf-nozzle holes. From this stuciji the optimumjuel injection nozzle (}iozzle hole diameter, O.32 mm, number ofnozzle holes, 8 andjuel injection angle. 148 Y wasseleeted to reduce beth the.fbel consumption and IVOx emission. 7he reasonfor this selection could be explained.fi'omthe highestjuei-air mixing in the earlyphase ofinjection due to the longest spray tippenetration and the highest heat release rate oj}er j9O A 1:DC due to the increased injection duration.