| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 105 === In this work, the innovative burner with v-shaped circular impinging structure was proposed. An experimental study was conducted to investigate the influence of burner structure on the feature of premixed propane flame. The design applied in the burner may reduce the consumption of fuel and improve the performance simultaneously. There are two main sections in this thesis. Firstly, the superior performance was verified through the comparison between v-shaped circular impinging burner and circular planar burner. The v-shaped circular impinging structure was beneficial to the numerous characteristics of combustion. The experimental results exhibited that blue flame (ϕ = 1.0) was the most stable flame type in the four types identified and was less influenced by surrounding flow filed from the high-resolution pictures took. This mechanism of impinging flame extended the stable operating region and effectively reduced the limit of blow-out flame and lift-off flame happening because of the preheated effect. Based on distribution of the temperature field, the high temperature zone was more concentrated and around 50 ℃ higher than circular planar burner. The v-shaped impinging structure in the rectangular outlet region enhanced the speed of chemical reaction by high temperature and made the unburned gas effectively blend in the central region. Furthermore, the computed results of non-intrusive diagnostics (PIV) revealed that the velocity and vorticity of v-shaped circular impinging burner were dramatically strengthened double compared to circular planar burner due to thermal buoyancy and shear stress. The mixing of unburned gas was proved by computing the horizontal velocity. There were also numerous vortices observed in the pictures of visualization, they swirled the outside air to the combustion field and increased the mixing of fuels and oxidants. According to the theoretical analyses and the experimental results discussed above, the increased flame interaction caused by the impinging structure takes several advantages to flame feature relative to circular planar burner.
Based on the results of the first section, the v-shaped circular impinging burner was redesigned and discussed in the second section. The overall size was minified to reduce the interval between flames, and the angle of impinging was changed to find a suitable angle used in v-shaped circular impinging structure. The results show that the highest temperature was measured when the impinging angle was 60 degree. However, the highest magnitudes of velocity and vorticity were measured when the impinging angle was 30 degree. It seems possible that these results are due to different angles of impinging and chemical reaction. Therefore, what the angle of impinging should be chosen is dependent on the objective of use. This research may be the significant reference for the industrial and domestic applications using v-shaped circular impinging structure.
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