| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 103 === In this research, a novel centralized microwave jet burner system is proposed that can be used as a test platform to enable direct studies of plasma assisted combustion (PAC) under various operation conditions and combustible mixtures. Computed results are obtained using the GRI3.0 mechanism and the Premix code of the CHEMKIN package. According to the simulation, when the dilution inert N2 in the oxidizer stream (air) is replaced by Ar, it is observed that the laminar burning velocities and adiabatic flame temperature are higher up to 40cm / s and 200K~300K, respectively. In the case of N2 replaced by Ar, the chemical effect is almost negligible and the heat capacity seems to possess the predominant effect on the flame characteristics. Spectroscopic characterizations of the burner have been conducted using digital imaging and optical emission spectrum. PAC of premixed methane/O2/N2 and methane/O2/Ar mixtures have been investigated at different fuel equivalence ratios and various microwave power. The continuous microwave plasma jets are generated successfully by the design of centralized microwave burner with a sharp-tip electrode as an antenna. The optical emission spectrum results show that with the initiation of a plasma flame by microwave, emission intensity peaks of the OH (A2Σ+) radicals can be observed both in the methane/O2/N2 and methane/O2/Ar mixtures. A comparison of the OH (A2Σ+) emission intensity profile shows that the intensity of OH radical in methane/O2/Ar mixtures is three orders of magnitude larger than that in methane/O2/N2 mixture. Experimental results also show that the minimum energy of the microwave energy requirements in maintaining a plasma ball is reduced by about 50% in methane/O2/Ar mixtures. Namely, the flame enhancement by applying an non-equilibrium plasma is more efficient when the dilution inert N2 in the oxidizer stream (air) is replaced by Ar. The coupling efficiency of the dilution inert in the oxidizer stream plays an important role in the flame enhancement mechanism for the PAC system.
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