| Summary: | 碩士 === 國立臺灣大學 === 機械工程學研究所 === 107 === Inspired from the aerodynamics of a shuttlecock, we proposed a new concept for the designing a diffuser burner with side-opening. The diffuser burner with and without side-opening structure were experimentally and.numerically analyzed under with and without a co-flow condition. We observed quantitative flame behavior and recorded the operating maps through direct flame images. The measurement of the flame temperature, chemiluminescence of free radicals and exhaust gas were also performed to assess the benefits of combustion efficiency of a diffuser burner with a side-opening structure. Through the particle image velocimetry (PIV) and the simulation of isothermal flow field in FLUENT, we analyzed the mechanism of stabilization and flow field structure.
In the first part, we adjusted the equivalence ratio of a premixed methane flame. The results show that the flame temperature slightly improved when a diffuser burner with a side-opening structure. When premixed methane flame has a lower equivalence ratio, transformed flame pattern would cause a decrease in air entrainment.
In the second part, we adjusted the flow rate of methane and co-flow velocity. The results show the flame stability and combustion efficiency of the diffuser burner with a side-opening structure is better than that of without a side-opening structure. The chemiluminescence intensity of free radicals and temperature along flame center line have greatly improved when a diffuser burner with a side-opening structure. As the co-flow velocity increasing, the flame length of both burner types was shortened, and the temperature within the high temperature area increased. Moreover, the distribution of free radicals not only concentrated toward burner tip but also increased its intensity, which makes a sufficient reaction of fuels and oxidant in the flame upstream when a diffuser burner with a side-opening structure. The results of measurement of exhaust gas show that a lower CO emission was achieved when a diffuser burner with a side-opening structure.
More fresh air injects into the diffusing section of a diffuser burner through side-opening structure under co-flow condition. Therefore, more supplied oxidant in this section causes an improvement of flame stability and combustion efficiency. The concept of side-opening structure of a diffuser burner offers an innovative reference for the future burner design.
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