| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系碩博士班 === 90 === Taking flame for heating source is the most widely way to obtain thermal energy. However, the relationship between the wall and flame play an important role while using the heating-flame. The mutual interaction between the flame and the heated surface is too complicated to explore in details. The effects of interaction, in terms of the separation distance between the jet flame and the horizontal wall, on the flame structure, the temperature distribution, the aerodynamics of the hot flow and the pollution formation are investigated.
The shadowgraph visualization and flame visualization technique are employed to observe the fame and the outer buoyant vortex structures. Therefore, calculations for the displacement and velocity of vortex are to explain the evolution of the one. For temperature gradient, we use the R-type thermocouple for temperature and observe the effect of the heat translation. Besides, for flame components, we use the technique of LIPF to measure the concentration of OH radical and use the gas analyzer for pollution concentration.
The results showed that when the horizontal wall is moved toward the flame, the variation of the flame structure could be observed in evidence. It is due to the outer buoyant vortices affected by horizontal wall and to vary flame structure. To make short of the matter, the effect of horizontal wall vary the flame structure, including variation of flame bulge and flame winding as wall as flame flutter. When the wall is getting close to flame, the flame bulge change from triangle-form to tetragon and get bigger in area of the flame. When the distance between wall and flame is close to the length of the flame, the flame tip has wind and flutter phenomenon. When the distance between the wall and flame is reduced, the distribution of the flame temperature is increased and the maximum temperature zone trend in the direction of the top wall. For OH radical distribution, it is dependent on the distance between the wall and flame. To shorten the distance is to increase the concentration of the OH radical. It is similar to the temperature distribution. For pollution opinion, the NOx emission has no obvious change, and CO emission is increase as the horizontal wall moves toward the flame. To sum up, the wall existence has an apparent variation of fundamental physical phenomenon to flame. It is an essential course to research the basis combustion.
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