Particles and unregulated emissions from heavy-duty engines

Sammanfattning: Nowadays, the diesel engine is a widely used power source with complex emissions. In order to find out the impact from diesel exhaust on health and environment, both regulated and unregulated exhaust gas emission have to be evaluated. Especially, emission obtained with new fuels and new techniques has to be evaluated properly to avoid an increased environmental impact. This thesis is based on following papers: In paper I, a contribution to the ongoing search for better and cheaper ignition improvers for facilitating the introduction of ethanol fuel was made. A new ignition improver, rapeseed methyl ester, RME, has been investigated and evaluated by means of design of experiments, combustion pulse measurements smoke and also, measurements of regulated exhaust emission. A general conclusion was that RME seems suitable for the task, i.e. ignition improvement. In paper II, a humid air motor system (HAM) for NOX reduction was investigated. Earlier studies have demonstrated that the system has capacity to lower NOX emissions from heavy duty diesel engines. The present study is directed to investigate the influence of the system on the emissions of particles and aldehydes, to monitor essential engine parameters, water consumption, and to verify the reducing ability. The NOX reduction capability where verified to be 51 % without any optimization. Reports have stated that Fischer Tropsch (FT) fuels are high quality, low emission diesel fuel substitutes. The purpose of the study in paper III was to compare the emissions from a heavy-duty, Valmet, diesel engine running on a commercial available FT fuel, Eco-ParTM, with the emissions obtained when the same engine is running on a established low emission fuel, a low sulfur diesel fuel with low aromatic content, Swedish environmental class 1 (EC-1) diesel fuel. The complex nature of exhaust gas makes it impossible to analyze all aspects of emissions. The work in this thesis has been focused on particles and unregulated emissions, in order to elucidate other aspects of emission than the one obtained with regulated emissions. Particles have been analyzed, partly as smoke in paper I and partly as particle size and distribution in paper II. Volatile Organic Compounds, VOC, are included in the summarized value of total hydrocarbon. Furthermore, the individual compounds that build up VOC occur at low levels in the exhaust gas, different methods may also have to be used, which makes analyses difficult and cumbersome. Therefore can effects regarding this class of compounds sometimes be neglected and unexplored. Additional analyses of VOC, two aldehydes, were carried out in paper II. VOC were also analyzed in paper III, nineteen compounds frequently occurring in exhaust was gas chosen for investigation together with the regulated exhaust gas components. Totally, was four aldehydes and fifteen individual hydrocarbons analyzed in paper III, besides HC, NOX, and CO, which were analyzed during all carried out investigations (I-III). Somewhat poorer emissions, smoke, HC, NOx, and CO, were obtained from the new ethanol fuel, though the increase was compensated by other positive effects. Large effects, mainly increases, could be seen for particle number and large reductions could be noticed for aldehydes in paper II. VOC were reduced, in favor and in large extent in the evaluation of the Fisher Tropsch fuel, paper (III). But large differences could also bee noticed in the behavior between individual compounds in the exhaust gas.