Abstract:

During the commissioning stage of the newly installed ethylene gas boiler, abnormal vibration and noise appeared in the air supply duct when the opening of the air supply fan valve reached over 37%. As the opening of the air valve increased, the vibration of the air duct and abnormal noise increased. The causes of abnormal vibration in the air supply duct were analyzed from the aspects of fan surge, uneven distribution of air flow field and Karman vortex resonance. Measures such as enhancing stiffness of the air duct, adding support rods in the air duct, and increasing guide plates in the variable diameter duct at the outlet of the air supply fan were taken, but no obvious effect was received. Removing the air heater and adding guide plates at the inlet and outlet of the air preheater achieved a certain effect. When the opening of the air valve reached 49%, the duct vibration and noise significantly increased, but the duct vibration could not be effectively eliminated. After calculation, it was confirmed that the consistency between the air preheater Karman vortex frequency and the air chamber inherent frequency was the main cause of violent vibration and noise of the air supply duct. By changing the width of the air preheater pipe box, adding the anti-vibration plate in the pipe box, changing the inherent frequency of the air chamber, reducing the Karman vortex effect, the violent vibration and noise of the air duct were eradicated.

Key words: ethylene gas boiler, air supply duct, violent vibration, noise, guide plate, Karman vortex, anti-vibration plate

摘要：

新安装的乙烯燃气锅炉在试车阶段，送风机风门开度达到37%以上时送风风道出现异常振动及声响，随着风门开度增大，风道振动及异响加剧。从风机喘振、空气流场分布不均及卡门涡流共振等方面对送风风道异常振动原因进行了分析。采取增强风道刚度、在风道中增设支撑杆、在送风机出口变径通道增加导流板等措施后，效果不明显。拆除暖风器，同时在空气预热器进出口处增加导流板，收到了一定效果，但当风门开度达到49%时，风道振动及噪音明显增大，未能有效消除风道振动。经计算，确认空气预热器卡门涡流频率与气室固有频率一致是送风风道剧烈振动及噪音产生的主要原因。改变空气预热器管箱宽度，在管箱中加装隔板，改变气室固有频率，降低卡门涡流效应，能根治风道剧烈振动及噪音。

关键词: 乙烯燃气锅炉, 送风道, 剧烈振动, 噪音, 导流板, 卡门涡流, 防振隔板