基于热声解耦方法的燃烧不稳定性预测

Prediction of the combustion instability based on the thermos-acoustic decoupling method

大型空气加热器易发生燃烧不稳定现象,造成加热器不能按预想状态工作,甚至失效。由于难以通过试验获得加热器燃烧室内部的精确参数,因此数值仿真是预测燃烧不稳定性的重要手段。通过对燃烧室内部燃烧-声学解耦的方式,分别计算火焰对声学扰动的响应和声学系统在热源扰动下的响应,将声学扰动下的燃烧响应表征为火焰传递函数,最终可获得燃烧室的不稳定模态频率并对其是否发生不稳定燃烧进行预测。结果表明:某型空气加热器的模态频率为1 389.9 Hz,且在声学模态上是稳定的;预测结果与试验结果符合较好,证明该方法具备良好的预测能力。

Large air heaters are prone to combustion instability, so that the heater cannot work at the expected operating conditions, even leading to failures. Because it is difficult to obtain accurate parameters inside the engine combustion chamber through experiments, numerical simulation is an important means to predict the unstable combustion process. In this paper, by decoupling the combustion-acoustic system inside the combustion chamber, the flame response to the acoustic disturbance and the acoustic system response to the heat source disturbance are calculated separately. The combustion response under the acoustic disturbance is characterized as the flame transfer function. Finally, the most unstable modal frequency in combustion chamber can be obtained. The results show that the modal frequency of the envisaged air heater is 1 389.9 Hz and is stable in the acoustic mode. The prediction results match the test results, proving that the method has good prediction ability.