Rijke管热声振荡声学特性数值模拟

Numerical Simulation of Acoustic Characteristics of Thermoacoustic Oscillation in a Rijke Tube

为了探究热声振荡发生的因素及机理,建立了Rijke管热声模型,采用稳定有限元方法对频域线性欧拉方程进行数值求解,在考虑平均流速及火焰处温度梯度的情况下,分析了火焰热释放、平均流速和燃烧响应模型对Rijke管声学特性的影响。结果表明,火焰热释放对Rijke管纵向模态的本征频率影响显著,本征频率随火焰热释放的提高而增大;平均流速更易对增长率产生影响,其随平均流速的增大而下降;纵向模态的本征频率及增长率随燃烧响应模型中时滞的变化呈周期性变化;横向模态的声学特性主要与平均流速有关。

In order to research the factors and mechanisms of thermoacoustic oscillations,a Rijke tube thermoacoustic model was established,and the stable finite element method was used to numerically solve the frequency domain linear Euler equation.Considering the average flow field velocity and the temperature gradient at the flame,the effects of flame heat release,average flow Mach number and combustion response model on the acoustic characteristics of Rijke tubes are analyzed.The results show that the flame heat release has a significant effect on the eigenfrequency of the longitudinal mode of the Rijke tube,and the eigenfrequency increases with the increase of the flame heat release;the average flow Mach number is more likely to have an impact on the growth rate,which varies with the average flow Mach number increase and decrease;the eigenfrequency and growth rate of the longitudinal mode change periodically with the time lag in the combustion response model;the acoustic characteristics of the transverse mode are mainly related to the average flow Mach number.