实验研究不同燃烧工况对燃烧自激振荡及音频特征的影响

Experimental Study of the Influence of Various Combustion Conditions on the Self-excited Oscillation and Acoustic Characteristics of the Combustion

以甲烷为燃料,在具有GE燃机6B喷嘴的1/3模拟燃烧室中,研究了燃烧室空气流量和当量比的变化对燃烧自激振荡压力波动的影响以及燃烧发出的音频信号的特征。实验结果显示:在3组不同入口空气流量工况下,随着当量比的增加,燃烧室经历了稳定—自激振荡—稳定的燃烧过程,且3组过程所历时的变化趋势保持一致;在不同的流量下,当量比为0.61工况时产生了最强烈的自激振荡,同时振荡的压力波动幅值和频率随燃烧室入口空气流量的增加而增大;通过FFT(快速傅里叶变换)计算发现,在有明显自激振荡的工况中,动态压力与音频信号的幅值均大幅超过稳定燃烧工况,同时音频信号的一个特征频率与动态压力信号的特征频率重合。

With the methane serving as the fuel,studied was the influence of changes in the air flow rate and equivalent ratio of a combustor on the fluctuation of pressure in the said combustor when the self-excitation and oscillation occur during the combustion process and also investigated were the characteristics of acoustic frequency signals emitted from the combustion in a model combustor scaled down in a proportion of 1: 3 and installed with the nozzles from GE6 B frame gas turbines. The test results show that under three groups of operating conditions of the compressor having different air flow rates at the inlet,with an increase of the equivalent ratio,the variation law of the combustion in the combustor in operation will keep unchanged,i. e. stable-self-excited oscillation-stable. At various air flow rates,under the operating condition when the equivalent ratio equals to 0. 61,the combustion in the combustor will produce a most violent self-excited oscillation and at the same time,the amplitude of the fluctuation in pressure and frequency caused by the oscillation will increase with an increase of the air flow rate at the inlet of the combustor. It has been found through the FFT( fast Fourier transform) calculation that under the operating conditions when an obvious self-excited oscillation occurs,the amplitudes of the dynamic pressure and acoustic frequency signals will exceed by a large margin those under the operating conditions with a stable combustion and at the same time,a characteristic frequency of the acoustic frequency signals will be in agreement with that of the dynamic pressure signals.