Browsing by Author "Chen, Young-Da"

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High-efficiency combustion of natural gas with 21-30% oxygen-enriched air
(2010-09-01)
Wu, Kuo-Kuang
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Chang, Yu-Cheng
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Chen, Chiun-Hsun
;
Chen, Young-Da
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機械工程學系
This investigation was aimed at studying the influence of 21-30% oxygen concentration on the heating rate, emissions, temperature distributions, and fuel (natural gas) consumption in the heating and furnace-temperature fixing tests. Increase in the oxygen concentration led to a more rapid heating rate and lesser fuel consumption due to lower levels of the inert gas (N(2)). When the oxygen concentration was increased from 21% to 30%, the heating rate was increased by 53.6% in the heating test and the fuel consumption was reduced by 26.1% in the furnace-temperature fixing test. Higher oxygen concentrations yielded higher flame temperature; hence, the NO(x) emission increased with increasing oxygen concentration. However, the increase of NO(x) emission in the furnace-temperature fixing test was less than that in the heating test. Moreover, the NO(x) emission was more sensitive to the excess oxygen at higher oxygen levels. The CO(2) concentration in the flue gas increased linearly with the oxygen concentration. Additionally, the temperature distributions became progressively nonuniform with increasing oxygen concentration because the convective heat transfer coefficient was altered. (C) 2010 Elsevier Ltd. All rights reserved.
Transient behaviors of a flame over a Tsuji burner
(2008-12-01)
Chen, Young-Da
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Chen, Da-Da
;
Chen, Chiun-Hsun
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機械工程學系
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Department of Mechanical Engineering
The present study investigated numerically the physical mechanisms underlying the transient behaviors of the flame over a porous cylindrical burner. The numerical results showed that a cold flow structure at a fixed inflow velocity of U (in) = 0.6 m/s in a wind tunnel could be observed in two co-existing recirculation flows. Flow variations occur repeatedly until t = 4.71 s, and then a vortex existed steadily behind the burner and no shading occurred. The ignition of flammable mixture led to a rapid rise in gas temperature and a sudden gas expansion. When it reached the stable envelope flame condition, U (in) is adjusted to an assigned value. Two blow-off mechanisms were identified. It was also found in the study flame shapes with buoyancy effects agreed with the ones observed experimentally by Tsai. Furthermore, the lift-off flame would appear briefly between the envelopes and wake ones, and was stabilized as a wake flame.