| Summary: | 碩士 === 國立臺灣海洋大學 === 機械與機電工程學系 === 99 === Acoustic excitation was utilized to modulate the flame behaviors using various exciting frequencies and voltages. The speaker-type actuator was installed in the combustor to perturb the axial flow speed and then increase the turbulence of central fuel jet. Therefore, the mixing of air and fuel was promoted. In the experiments, a thermocouple, photograph recorder and gas analyzer were utilized to examine the characteristic flame modes, fame height, flame lift-off length, temperature distribution, heat release and the concentration distribution of exhausted gases.
Three flame modes were classified and denoted as – jet flame, lifted flame and blow off. As the input voltage (Eexc) was fixed at Eexc = 10 volt, the flame length was shortened; the flame became stable; the temperature profile was broadened; and the heat release can be increased with comparing those of a traditional combustor. Specifically, the highest temperature is approximately 1800K and the heat release was promoted about 74% with the addition of acoustic wave. Furthermore, the optimum heat release occurs at the exciting frequency (fexc) of 180 Hz and 720Hz. The radial distribution of exhausted gases indicated that the join of acoustic wave increased the combustion efficiency. Furthermore, the concentrations of monoxide (CO), carbon dioxide (CO2), oxygen (O2), and nitric oxide (NO) were decreased with comparing those without the effect of acoustic wave.
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