Preliminary studies confirm the assumption that existing soot formation models need to be revised, or more detailed, phenomenological soot formation models have to be established - especially in regard of the precalculation of the soot emission of combustion engines with extreme parameters (high pressure injection, high EGR, high pressure charging). In order to generate the necessary basic knowledge, the Chair of Combustion Engines (LVK) developed a novel gas sampling probe which allows for the time-resolved taking of small soot samples from the combustion chamber. Compared to common gas sampling probes, the new probe features several particularities [6], such as a novel injection process of a probe head into the flame inner core for the sampling. The LVK's new gas sampling probe rendered extensive sampling series possible that show the formation and modification of soot during the combustion cycle. It was possible to take samples out of the combustion chamber at a time resolution of 1 msec. At the Department of Materials Science and Engineering (Institute of Microcharacterization WW7) in Erlangen a first soot sample series from the combustion chamber of a diesel engine was successfully analyzed and verified by means of TEM and EELS. Though the formation, growth and oxidation of primary soot particles was verified and correlated with combustion processes. Furthermore it was possible to discern characteristic modifications, from compact to fissured shapes, of generated soot agglomerates during combustion. Therefore a first modeling of the soot formation was identified. With a series of time-resolved samples that were taken at the identical operating point of the engine some months later, it was possible to prove the complete reproducibility of the soot sampling with the LVK gas sampling probe.
展开▼
