Within a research project, measures to reduce smoke and particulate emissions from marine engines, especially during low and transient loads, are investigated. The potential of flexible common rail systems for smoke-reduced combustion in marine engines is evaluated scientifically. Analyses results of injection, mixture preparation, combustion and emission generation processes are presented. At Rostock University, compact common rail injectors are mounted to a pressurised research chamber with optical accesses to investigate injection processes and fuel sprays at engine-relevant conditions. An ICCD-camera is applied to analyse macroscopic fuel spray properties for the load range of marine diesel engines. Optical data are analysed to determine macroscopic spray parameters (spray-cone angle, spray length, spray-tip velocity, spray volume). Droplet size and velocity distributions for different regions in the spray are determined by Laser-PDA, a technique based on laser-light scattering at spray droplets. Systematic measurements are made to determine the influence of injection parameters (rail pressure, injection duration, cylinder air density, multiple injections) on spray properties for different marine fuels. The results allow adjustment of injection parameters of flexible common rail systems for smokereduced combustion at low loads. Conditions causing excessive soot emissions (insufficient droplet breakup, wallfilm generation) can be detected and avoided. Simultaneously, investigations of the complex combustion and emission generation processes are done at WTZ Rosslau GmbH. A single cylinder mediumspeed research engine (240 mm stroke, 160 mm bore) is equipped with the same common rail injector as used at Rostock University. Smoke emissions during low and transient loads are caused by oxygen lack. Such conditions are reproduced at the research engine by reduced charge air pressure of the aux-iliary blower. The influence of charge air pressure on combustion and emission generation processes is investigated first. Parameters are then varied to reduce smoke at reduced charge air pressure. The smoke reduction potential of rail pressure adaptation, injection tim-ing and multiple injection is analysed. Finally, injection strategies with partly-homogeneous fuel-air mixtures are investigated. Optical measurements of flame temperatures and soot concentration inside the cylinder are done for all variations. Filter smoke numbers (FSN), particulates (mass, composition, size distribution) and gaseous emissions are measured giving insight into emission generation mechanisms. During periods of deficient air, incomplete soot oxidation causes increasing soot pro-portions in particles and increasing FSN. The particulate emissions can decrease partly due to smaller hydrocarbon content. Therefore, exhaust opacity depends highly on particle com-position and does not correlate with particulate emission. Minimised soot generation and maximised soot oxidation is possible even at oxygen lack, by improved fuel droplet and mix-ture distribution and intensified transport processes inside the cylinder. Based on relationships between engine operation conditions and spray properties, injection parameters can be adapted for emission-reduced operation at all loads without sig-nificant consumption trade-offs. Results are comprehensive data for modelling injection and combustion processes and for development and verification of simulation models. With such models, new NOX and soot reduction technologies can be derived. The common rail technol-ogy proves to be an efficient tool to control the combustion process over the whole engine operation range.
Measures to reduce smoke and particulate emissions from marine diesel engines using compact common rail injectors
2007
16 Seiten, 25 Bilder, 13 Quellen
Conference paper
Storage medium
English
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