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Effect of Air Quantity Distribution Ratio on Flame Height of Flue Gas Self-Circulation Burner
Author(s): Kai Xie, Yunjing Cui, Xingqi Qiu, Jianxin Wang
Keywords: Air quantity distribution; Central air; Swirling air; Secondary air; RFGR; Flame height
It is a difficult scientific problem of applied fluid mechanics that the flame is too long and does not match the furnace chamber in the small restricted heating space. This paper aims to investigate the effect of air quantity distribution ratio on the flame height of a flue gas self-circulation burner. In order to obtain a better combustion emission effect and a shorter flame height, a combustion head structure of small flue gas self-circulation is designed. Numerical simulation was employed to investigate the effect of the different distribution of central air, swirling air and secondary air on flame height. The periodic boundary condition model is adopted and the numerical model is compared and validated by experiment. Correlation analysis was used to determine the influence of air inlet ratio of each part on flame height and recirculating flue gas ratio (RFGR). Results show that the influence of different air quantity distribution on flame length is very significant. A reasonable central air ratio is a necessary condition for good combustion of this flue gas self-circulation burner. Secondary air can effectively increase the RFGR, and flame height was significantly shorter with the increase of RFGR, but when it increases to more than 12%, the flame length is basically no longer shortened. On the premise of stable combustion, when the ratio of central air, swirling air and secondary air respectively are 25%, 35%, 40%, the shortest flame length is gotten. This work reveals an influence mechanism of the flame height of small burner with flue gas circulation structure. These results can provide theoretical support and engineering design basis for the short flame problem in small restricted space.