| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 84 === Comparison of the flame characteristics of
"jet flame" and "jet flame in the wake" is carried out in
this research. Results show that the temperature of "jet
flame in the wake" is higher than "jet flame", implying
that the "jet flame in the wake" has a better combustion
conversion efficiency. On the other hand, the existence of
wake flame of "jet flame in the wake" provides heat
source to stabilize the flame. Measurements of concentration of
combustion products also show the same trend. The turbulence
intensity and wake intensity of "jet flame in the wake"
increase with increase of Reynolds number. Under higher Reynolds
number case, there is a better mix between fuel and air and a
higher concentration in the wake. Therefore, there is a
better combustion conversion efficiency under higher
Reynolds number condition. The velocity of the fuel jet and
Reynolds number also determine whether the combustion is primary
in the wake or in the jet. Experiments also show that the
interaction between jet and wake enhances the flame limit, e.
g., the blow-off velocity of the "jet flame" is about 2m/s,
but at the "jet flame in the wake" is about 18m/s. This
indicates that the flame stability limit can be improved
in the conventional combustion device by providing an extra
flameholding mechanism.
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