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Mixing and soot formation processes in transient gas jet flame
Technical Paper
2000-05-0075
Sector:
Language:
English
Abstract
A transient gas jet and its flame are the most fundamental
phenomena of a transient spray and its flame breaking out in a CI
engine and an SI engine with the direct injection system. In the
case of CNG and LNG engines, the fuel itself is just gaseous state.
The 2-LIF technique was applied to the transient gas jet to obtain
the mixing process between the surroundings and it, and the
simultaneous application of LII and LIS techniques were applied to
the transient gas jet flame to obtain the soot formation
process.
The conclusions drawn from the experiments are: (1) The vortices
structure of the jet has the close relation to the tendency of the
relative fuel concentration. (2) At the upstream, the entrained
surroundings are very small near the jet axis, however, they
increase as the location goes to the jet periphery. (3) As the
location goes farther from the nozzle outlet, there appears the
unevenness due to the small fluorescent intensity. (4) At the
medium region, the unevenness at the jet periphery is distinguished
and the surroundings enter even at the region of the jet axis. (5)
The surroundings existing at the jet tip region diffuse more
remarkably. (6) A great deal of soot with very small size are
generated at the upstream. (7) The relative soot diameter increases
and the relative soot number density decreases due to the
coalescence and the condensation as the location goes farther from
the nozzle outlet. (8) At the flame tip region, the large soot
appears and the relative soot number density increases as the time
is passing. (9) The tendency of the rate of the area of medium-size
soot to the whole area of soot corresponds to that of the temporal
change in the relative mean soot number density.