695 / 2019-04-30 19:29:10

Experimental Study of Pressure Oscillation in Gas Boilers of Ultra-low NOx Combustion

ultra-low NOx combustion, flue gas recirculation, combustion instability, pressure oscillation

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Under some ultra-low NOx combustion conditions that introduce flue gas recirculation, the boiler has a surge phenomenon, which causes a flameout and seriously affects the safe and stable operation of the boiler. In this paper, the surge phenomenon in the ultra-low Nox combustion process of a small semi-industrial full premixed combustion test bench with flue gas recirculation device is studied, and the influence of flue gas recirculation rate on the pressure characteristics of the combustion process is analyzed. Besides, the effect of the uniformity of recycled flue gas and air on the surge of the combustion system is studied. The results show that with the increase of flue gas recirculation rate, the characteristic frequency of the pressure field of the combustion chamber tends to be obvious, and the maximum amplitude of the pressure spectrogram decreases first and then increases. When the recirculating flue gas and air are not uniformly mixed, the pressure vibrations in the combustion chamber and the flue gas recirculation pipe tend to be in the same frequency and in phase, resulting in a combustion surge phenomenon . The more uniform the mixing of the recirculated flue gas with the air, the larger the adjustable range of the flue gas recirculation rate during stable combustion. The pressure frequency is mainly distributed between 20-25Hz when the combustion is stable, and the pressure frequency is mainly distributed between 0-5Hz when the surge occurs.