FLAME STABILIZATION OVER ATSUJI BURNER BY FOUR-STEP CHEMICAL REACTION

摘要

This investigation applies a four-step chemical kinetics mechanism to implement the original combustion model developed by Chen and Weng (Combustion Science and Technology, Vol. 73, pp. 427-446, 1990). Comparing the blowoff curve of Tsuji (Progress in Energy and Combustion Science, Vol. 8, p. 93, 1982) with that of Chen and Weng reveals that this study yields a much better prediction than that in the latter reference. Also, the data in this study has an excellent agreement with the measured data of Dreier et al. (Berichtc der Bunsen-Gesetlschaft―Physical Chemistry, Vol. 90, pp. 1010-1015, 1986). The interested parameter is the inflow velocity U_(in). As U_(in) increases, the envelope diffusion flame, wake flame, liftoff flame, and another wake flame appear in that order before complete extinction. The formal wake flame is transformed from the envelope diffusion flame and the other is from the liftoff flame. The existence of a liftoff flame is verified by a corresponding experimental observation (Tsa et al., 2003). The maximal liftoff height is 1.7D when U_(in) is 1.05 m/s, and this height is maintained up to U_(in)= 1.09 m/s. Then the height declines gradually as the inflow velocity increases, which is a process that can be regarded as flashback. No recirculation flow exists behind the cylindrical burner for these liftoff flames. A transition from liftoff to wake flame occurs between 1.13 to 1.15 m/s. The wake flame reappears at U_(in)=1.16 m/s. Finally, the flame is extinguished completely when U_(in) > 2.12 m/s. The flame's lifting and dropping back is explained.