关键词: 预混火焰;热声耦合振荡;线性扰动分析;燃烧动力学

Abstract: Combustion oscillations are phenomenon usually encountering during the engine operation and it is dangerous for engine operation.Combustion oscillations are induced by coupling between unsteady heat release and pressure perturbations.The dynamical processes of natural gas premixed combustion were examined by varying fuel-air equivalence ratio;power loads and boundary conditions.Under each condition,the equivalence ratio range of stable combustion was obtained and the variations of oscillation modes were analyzed.It was shown that the oscillation frequencies would increase with the decrease of equivalence ratio.At the atmosphere pressure,the combustion oscillations will disappear near the lean blow out limits and the frequencies will change in the range between 500 Hz and 1000 Hz.The combustion stable range turns into narrow when the outlet is close to the choking conditions.The shorter length of the inlet boundary,the higher frequency of the pressure oscillations.The power loads also have significant influences on the frequencies of oscillations and their amplitudes.Meanwhile,the dynamical processes of natural gas combustion were also studied by linear perturbation theory.The oscillation modes were analyzed.

Key words: Premixed combustion;Thermo-acoustic instabilities;Linear perturbation theory;Combustion dynamics