基于声学模态分析的燃气锅炉热声振荡研究

Study on Combustion Instability of a Gas Boiler Based on Acoustics Analysis

针对某350 k W燃气工业锅炉出现的压力振荡现象开展了实验与模拟研究。实验研究了不同过量空气系数条件下锅炉炉膛的压力波动特征,结果表明:炉膛内压力波动表现出低频振荡特征,过量空气系数范围为1.19~1.59时,炉膛压力振荡峰值频率为25.6~24.3 Hz;结合CFD燃烧过程数值模拟和声学模拟,计算了实验工况条件下锅炉系统空腔的声学模态,计算中考虑了锅炉系统空腔的温度分布对声学模态的影响,计算得到二阶声学模态频率范围为24.2~27.5 Hz,与实验得到的炉膛的压力波动峰值频率区间一致,且锅炉尾部换热器和排烟管道对锅炉系统空腔声学模态有较大影响,说明CFD方法结合空腔的声学模态分析可用于预测热声耦合的特征频率。

The occurrence of combustion instability of a 350 k W gas boiler was studied via experiments and simulations.The pressure fluctuations with different excess air conditions were achieved by experiments and the negative relationships were found.When the excess air coefficients were varied from 1.19 to 1.59,the main frequency of combustion chamber pressure oscillation decreased from 25.6 to 24.3 Hz.Combined with CFD simulation analysis,the acoustic modes were achieved which range from 24.2 Hz to 27.5 Hz.The acoustic modes were significantly influenced by temperature distribution.The experimental data of second-order acoustic modes was validated by simulations.The output structure of the boiler had great effect on acoustic modes,indicating the occurrence of the coupling between the pressure fluctuations and acoustic modes.