Hildenbrand, F.; Schulz, Christof; Sick, V.; Josefsson, G.; Magnusson, I.; Andersson, O.; Alden, M.:

Laser spectroscopic investigation of flow fields and NO-formation in a realistic SI engine

In: SAE Techn. Paper Series 980148, Jg. SP-1352 (1998) ; Advanced Converter Concepts for Emission Control, S. 1-10
Zeitschriftenaufsatz / Fach: Maschinenbau
This paper presents results from a quantitative character-ization of the NO distribution in a SI engine fueled with a   stoichiometric iso-octane/air mixture. Different engine   operating conditions were investigated and accurate   results on NO concentrations were obtained from essen-tially   the whole cylinder for crank angle ranges from igni-tion   to the mid expansion stroke. The technique used to   measure the two-dimensional NO concentration distribu-tions   was laser induced fluorescence utilizing a KrF exci-mer   laser to excite the NO A-X (0,2) bandhead. Results   were achieved with high temporal and spatial resolution.   The accuracy of the measurements was estimated to be   30% for absolute concentration values and 20% for rela-tive   values. Images of NO distributions could also be   used to evaluate the flame development. Both the mean   and the variance of a combustion progress variable could   be deduced. The engine used in the investigation was a   one cylinder version of a Volvo N1P engine equipped with   good optical access. Using the same engine and the   same operating conditions, data on the in-cylinder flow   field was also obtained using particle imaging velocime-try.   The comprehensive and detailed data base generated in   the present work is currently being used for detailed vali-dation   and improvements of models for numerical simula-tion   of engine combustion and emission formation.   Nitric oxide is one of the most important combustion gen-erated   pollutants with impact on the environment and on   human health. Internal combustion engines play a major   role in the overall production of this species even though   the use of catalytic converters has significantly lowered   NO emissions from gasoline engines in recent years.   However, in order to reduce emissions even further and   to meet future emission regulations, new and improved   engines need to be developed. Improved aftertreatment   systems and improved engine control will solve part of   the problem but lower NO emissions in the raw exhaust   would lead to a significant reduction of net emissions,   particularly during transients and cold starts. For gasoline   engines running with a lean fuel/air mixture special prob-lems   are encountered since no satisfactorily efficient   aftertreatment system is yet available. Therefore, new   developments of the basic combustion system are neces-sary   to reduce the amount of NO formed during the   energy conversion. These developments would be   greatly facilitated by a detailed knowledge of the basic   physical and chemical processes in internal combustion   engines.   This paper presents the application of different laser-based   diagnostics for measurements of basic combus-tion   phenomena in a commercial gasoline engine