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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/42759

Title: 燃燒器受外部聲波擾動的流場行為與燃燒特性
Flow Behaviors and Flame Characteristics of Combustors Using External Acoustic Excitation
Authors: Wu, Kuan-Yu
吳冠諭
Contributors: NTOU:Department of Mechanical and Mechatronic Engineering
國立臺灣海洋大學:機械與機電工程學系
Keywords: 聲波擾動;外部激擾;火焰高度;燃燒效率
acoustic perturbation;external turbulence;flame height;ombustion efficiency
Date: 2014
Issue Date: 2017-05-24T08:23:18Z
Abstract: 本實驗利用揚聲器安置在燃燒器旁邊,並且改變揚聲器的電壓和其頻率來改變其流場特性,像是增強其紊流強度來增進燃料與空氣混和的效果,並且分析其調製效果所需的輸入條件。在冷流場實驗過程中,使用雷射光頁輔助煙線流場觀測技術,使複雜的流場結構展現出來。再以二維熱線風速儀分析流場速度分輛,並使用一維熱線風速儀量測其頻率特性,來得知個特徵模態及其混和能力。在燃燒實驗過程中使用了拍照攝影、熱電偶溫度測量,來測量其燃燒場特徵模態、火焰高度以及溫度分布。 經由上述實驗方式,在等溫流場裡,固定輸入正弦坡及電壓10伏特進,隨著不同機擾頻率、環噴流速度的變化,可將不同激擾頻率所調制的流場特徵模態分為六種:噴流流場中單純中心噴流時沒受激擾影響的A模態(mode A)、能夠讓噴流流場產生近似渦漩模態的B模態(mode B)、噴流流場因為被揚聲器的頻率主導而產生類似揚聲器外型的C模態(mode C)、噴流流場中央產生類似渦漩崩潰(vortex breakdown)的D模態(mode D)、跟D模態差不多但是產生崩潰的位置提高的E模態(mode E);最後是單純的渦漩模態(Vortex-shedding)F模態(mode F)。其中發現在噴流模態(Jet flow)中將揚聲器電壓用10伏特,訊號產生器為產生正弦波10 Hz影響流場效果最為顯著。則在渦漩模態(Vortex-shedding)中影響較不明顯。根據等溫流場所得之,影響流場效果最大的頻率為10 Hz因此在火焰場裡,發現噴流火焰模態(Jet flame)、閃爍火焰模態(Flickering flame)以及跳脫火焰模態(Lifted flame)裡能夠有效降低火焰高度從10%到最高到30%不等,火焰溫度可以降低10K到50K不等。其中在閃爍火焰模態(Flickering flame)之中是火焰高度減少最多的區域,則其中在跳脫火焰模態(Lifted flame)是降低最多的區域。
The experiment places a speaker aside a combustor and modifies its voltage and frequency to change its flow field characteristics, which seems to enhance the turbulence strength so as to improve the effect of mixing fuel and air, and it also analyzes the required input conditions of the regulated results. In the cold flow field experiments, laser light sheet is adopted to assist the mist-plume technique in flow field observation to display the complicated structure of flow field. Then, it utilizes the 2D hot-wire anemometer to analyze the velocity component in the field and one dimensional hot-wire anemometer to measure the frequency characteristics, so as to obtain a flow mode and its hybrid capacity. In the experiment, it takes photos and utilizes thermocouple thermometer to measure the flame mode, flame height and temperature distributions of combustion filed. From the above-mentioned experiments, it finds that in the isothermal flow field, if the sine wave and voltage of 10 V are input regularly, as the turbulence frequency and ring jet speed change, the characteristic mode of flow field regulated in line with different turbulence frequency can be divided into six types: Mode A that is the pure center jet and not affected by the turbulence in the jet flow field, Mode B that can make the jet flow field generate mode similar to vortex, Mode C similar to the appearance of speaker generated by the frequency of speaker in the jet flow field, Mode D similar to the vortex breakdown generated in the center of jet flow field, Mode E is similar to Mode D but its position of breakdown is upper, and Mode F which is the pure vortex-shedding mode. In which it finds when speaker voltage is set as 10 V in the jet flow, the signal generator produces a sine wave of 10 Hz, which has the most significant influence on the flow field performance but its influence on that in vortex-shedding mode is not obvious. Based on the findings obtained in isothermal flow field, the frequency which exerts the largest effect on flow field is 10 Hz, thus it finds in the flame flow field, the flame height can be effectively reduced by 10-30% in the jet flame, flickering flame and lifted flame modes, and the flame temperature can be lowered by 10K-50K. Wherein, the reduction of flame height is maximum in flickering flame mode while the minimum in lifted flame mode.
URI: http://ethesys.lib.ntou.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=G0010172070.id
http://ntour.ntou.edu.tw:8080/ir/handle/987654321/42759
Appears in Collections:[機械與機電工程學系] 博碩士論文

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