本研究使用自行開發之流體自激振盪器，利用實驗方法，探討自激振盪器對平面噴流火焰及鈍體分歧噴流火焰之燃燒性能的改善。藉由自激振盪器的流場調制，改變流場動量傳輸的方式，將軸向動能轉換至橫向，增強燃料的擴散特性，同時增強燃燒器尾流的紊流強度及迴流效應，使得中心燃料噴流與兩側空氣噴流能快速地混合，進而提高燃燒效率。藉由火焰拍照攝影技術、溫度量測、燃燒氣體濃度量測、火焰流場PIV量測等實驗方法，研究非預混的三種燃燒器(平面噴流、鈍體分歧噴流及自激振盪噴流)的火焰行為、溫度、濃度、燃燒當量比及火焰流場結構、速度方向、流線、速度分佈、燃燒熱釋放率等物理現象，分別予以分析與比較。任一燃燒器皆存在三種主要的特徵模態：附著火焰、過渡火焰及跳離火焰模態。附著火焰為火焰根部附著在燃燒器上。過渡火焰為火焰根部呈現不穩定的跳離與再附著於燃燒器上。跳離火焰為火焰根部跳離燃燒器。實驗結果顯示自激振盪噴流燃燒器在相同的中心燃料噴流與空氣噴流下，火焰長度最短，火焰溫度分佈中的最高火焰溫度值最大，CO2濃度分佈最寬且濃度值最大，CO與C3H8濃度分佈最窄且濃度值最小，而且最大燃燒當量比φmax最小。在火焰流場結構方面，自激振盪噴流燃燒器在火焰流場有最大的平均橫向速度、剪應力、橫向及軸向的紊流強度，顯示自激振盪噴流燃燒器在燃燒時有最大的動能傳遞，增加火焰流場的擴散、混合與捲入效應，使燃燒化學反應更完全。自激振盪噴流燃燒器的燃燒熱釋放率比鈍體分歧噴流燃燒器大1.9 ~ 2.8%，比平面噴流燃燒器大8.4 ~ 9.9%，此結果顯示自激振盪噴流燃燒器的燃燒性能為最佳。

A self-sustained oscillating-jet burner for improving the combustion of the plane-jet burner and bifurcated-jet burner was developed and studied. The oscillation frequency, flame behavior, thermal structure, combustion-product distributions, and velocity distributions of the oscillating-jet flame were experimentally examined and compared with the non-oscillating bifurcated-jet and plane-jet flame. The flame behavior was studied with instantaneous and long-exposure photography. The temperature distributions were measured with a fine-wire thermocouple. The combustion-product concentrations were detected with a gas analyzer. The velocity distributions were measured with particle image velocimetry (PIV). Three characteristic flame modes (attached flame, transitional flame, and lifted flame) were identified in the domain of the Reynolds number of fuel jet flow and Reynolds number of co-flowing air. The results showed that the length of the oscillating-jet flame was reduced by about 6.7% and 56.6% when compared to that of the bifurcated-jet and plane-jet flames, respectively. The transverse temperature profiles of the oscillating-jet flame presented a wider spread than the bifurcated-jet and plane-jet flames did. The oscillating-jet flame’s maximum temperature was about 100 oC and 250 oC higher than that of the bifurcate-jet and plane-jet flames. The oscillating-jet flame presented a larger CO2 concentration, the smaller unburned C3H8 and CO concentrations, a larger velocity fluctuation, and larger heat release ratio when compared to the bifurcated-jet and plane-jet flames. The experimental results revealed that the combustion in the oscillating-jet flame was more complete than that in the bifurcated-jet and plane-jet flames, which displayed that the oscillating-jet burner improved the combustion of bifurcated-jet burner and plane-jet burner.

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