A newly developed Forward Illumination Light Extinction (FILE) soot measurement technique was applied in a constant volume spray chamber to study the effects of ambient temperature and oxygen concentration on soot evolution in diesel combustion. The FILE technique with the capability of two-dimensional time-resolved quantitative soot measurement provides the much-needed information to investigate the soot formation mechanism. The ambient temperatures of 1200K, 1000K and 800K were tested to study the temperature effects on soot formation. A decrease of ambient temperature results in a longer ignition delay, which promotes a larger premixed combustion zone combining with higher heat release rates. The change of ambient temperature from 1200K to 800K increases the fuel portion burnt in the premixed combustion period. At 800K, combustion is dominated by the premixed combustion and much less soot is formed. Diesel combustion with 21% and 15% ambient oxygen concentration was also studied. With lower ambient oxygen concentration, the combustion process is basically not changed, but expands into a longer time span with a lower heat release rate. The lower heat release rate results in a lower flame temperature, which benefits the NOx emission control. However, with about the same amount of soot within the flame, and much longer soot life, soot has more chance to escape to the exhaust.

This content is only available via PDF.
You do not currently have access to this content.