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Nitrogen oxide (NOx) and particulate matter (PM) emissions of diesel vehicles are regarded as a source of air pollution, and there is a global trend to enforce more stringent regulations on these exhaust gas constituents in the early years of the 21st century. On the other hand, the excellent thermal efficiency of diesel engines is certainly a welcome attribute from the standpoints of conserving energy and curbing global warming. Recently, many research institutes around the world have been using high-efficiency direct-injection (DI) diesel engines to research emission control technologies. The authors have also been engaged in such research [1,2]. As a result of this work, we have developed a new combustion concept, called Modulated Kinetics (MK), that reduces NOx and smoke simultaneously due to low-temperature and premixed combustion characteristics, respectively, without increasing fuel consumption [3,4].

Coating the heat insulation materials on the combustion chamber walls is one of the solutions to reduce the cooling loss of internal combustion engines. In order to examine the coatings, the evaluation of the heat transfer coefficient and the analysis of the heat transfer phenomena on the heat insulated walls are important. Firstly, the highly-responsive wall temperature sensor is developed, and the instantaneous wall heat flux is measured to evaluate the heat transfer coefficient on the heat insulated walls. The results show that the Nusselt number on the heat insulated walls is less influenced by the Reynolds number variation than that on the metal walls. Secondly, the high speed µ-PIV is employed to analyze the various turbulent flow characteristics. The results show that the turbulent dissipation on the heat insulated walls is smaller than that on the metal walls.