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热声耦合振荡是在推进系统工作中经常遇到的危害系统工作及安全的现象。它是由非稳定燃烧放热和压力脉动互相耦合产生的系统振荡过程。通过对天然气预混燃烧过程中的热声耦合振荡现象进行了实验研究,分析了不同当量比、热负荷和进出口边界条件下天然气燃烧的动态过程,分析其稳定范围及振荡模态随影响因素的变化规律。结果显示振荡频率随着当量比的减小有所增加,但是没有发生模态变化。在常压条件、接近贫燃熄火极限时,热声耦合振荡现象消失,压力脉动频率跃升至500 Hz或1000 Hz附近的高频。燃烧室出口越接近阻塞条件,燃烧过程的稳定范围越小。同时入口边界位置越接近燃烧段,压力脉动频率越高。热功率变化也会对脉动频率和声压级数值产生影响。另外还采用线性扰动分析方法对天然气燃烧动态过程进行理论分析,进一步研究了不同条件下旋流预混燃烧的热声耦合振荡模态。
Thermoacoustic coupling oscillation is a phenomenon that is often encountered in the work of propulsion systems that endangers system operation and safety. It is produced by the unsteady combustion exotherm and pressure pulsation system oscillation process. The phenomenon of thermoacoustic coupling oscillation in natural gas premixed combustion process was studied. The dynamic process of natural gas combustion under different equivalence ratio, heat load, and import and export boundary conditions was analyzed. The stability range and oscillation mode were analyzed with the influencing factors The law of change. The results show that the oscillation frequency increases with the decrease of equivalence ratio, but no modal change occurs. Under atmospheric conditions, close to the lean burnout limit, thermoacoustic coupling oscillating disappears and the pressure pulsation frequency jumped to a high frequency around 500 Hz or 1000 Hz. The closer the outlet of the combustion chamber is to the clogging condition, the smaller the stable range of the combustion process. At the same time, the closer the inlet boundary position is to the combustion section, the higher the pressure pulsation frequency is. Thermal power changes also have an effect on the pulsation frequency and sound pressure level values. In addition, a linear perturbation analysis method is also used to analyze the combustion dynamics of natural gas. The thermoacoustic-coupled oscillation modes of the premixed combustion under different conditions are further studied.