| Summary: | 碩士 === 大仁科技大學 === 環境管理研究所 === 98 === This thesis focuses on the effect of exit spacing on noise levels in the audible range generated by a multiple-jet nozzle with conical profile. It has been shown that, for a multiple-jet nozzle, the exit spacing can have an adverse effect on noise levels in the audible range. If this effect can not be minimized, the use of multiple-jet nozzles to control industrial jet noise will see limited applications. In this work, instead of on a flat plane, we distribute nozzle exits on a conical surface to decrease the interaction between neighboring jets.
All multiple-jet nozzles tested have exits with 1-mm diameter. We vary the diameter of the circle on which the nozzle exits are distributed to change the exit spacing. Noise spectra are compared with those for nozzles with exits on a flat plane. Results show that the conical profile effectively delays the merging the neighboring jets and lessen the trend of spectrum moving toward the lower frequencies. Although exit spacing is still a major factor in determining noise levels in the audible range, its effect is less pronounced for conical nozzles than for nozzles with exits on a flat plane.
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