Growing environmental concerns, such as global warming due to the emission of the
greenhouse gas CO2 by automotive power plants, lead to the need for cleaner and fuel
saving combustion systems. Direct injection combustion systems applied to the spark
ignited engine might be a way to improve the efficiency particularly by reducing
pumping and heat losses during part load while maintaining the advantages of high power
density and engine speeds during high loads [Zhao, Lai et al., 1999]. Initially, wall
guided combustion systems were pursued, but high hydrocarbon and soot emissions led
to the investigation of spray guided systems. Here a higher degree of stratification is
possible, which yields improved emissions [Drake, Fansler et al., 2004; Honda,
Kawamoto et al., 2004]. Nonetheless, due to high oxygen availability and locally rich
mixture, the nitric oxide formation is comparably high. This is detrimental as the widely
employed exhaust aftertreatment by a three way catalytic converter is inefficient for
overall lean mixtures. NO storage catalytic converters are widely employed, but require
rich exhaust gas to reduce the stored NO. This is generated by operating the engine
homogeneous-rich for a brief period of time, which of course comes with a fuel
consumption penalty [Tamura, Kikuchi et al., 2001; Krebs, Pott et al., 2002]. A reduction
of in-cylinder nitric oxide is desirable to minimize the number of regeneration cycles.
Hence the understanding of in-cylinder NO formation is important, so that the necessary
scientific background for improvement of the combustion system is provided. An
assessment of the NO formation process inside the engine exclusively by drawing
conclusions from engine out emissions is difficult, because of the highly inhomogeneous
nature of the stratified charge combustion process. Also, due to high cyclic variability
cycle resolved measurements are desirable, which conventional emissions analyzers are
not capable of. 汽车发动机多参量测试系统 PLIF平面激光诱导荧光火焰燃烧检测系统 德国LaVision PIV/PLIF粒子成像测速场仪
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