<title>Analysis of combustion flame in a DI diesel engine</title>

Abstract

Diesel engines are useful for commercial vehicles because of low fuel consumption and CO<SUB>2</SUB> emissions that cause the greenhouse effect. However, it is necessary for environmental conservation to develop clean combustion. For thirty years, the combustion phenomena of diesel engines using combustion chamber visualization techniques have been widely studied by many researchers. Since in-cylinder flame temperature affects directly on NOx characteristics in engines, this phenomena has been studied in detail in multi-cylinder diesel engines using a new method to measure the in-cylinder temperature distribution by a two color method. Typical two color methods for two dimensional temperature distribution have used negative color films as recording media. So it took several days to analyze the flame temperature. However since the new system consists of a CCD camera and computer, the analyzing time is reduced to about 10 minutes. Parametric studies on injection timings, engine loads, intake valve layouts, and EGR rates using multi-cylinder commercial engines were carried out to investigate the effect of the flame temperature on NOx concentration. Each parameter study showed that the maximum temperature which occurred in a local stoichiometric combustion area of flame is correlative with NOx emissions rather than mean temperature.