Dynamic and Flashback Characteristics of the Syngas Premixed Swirling Combustors

Abstract

Flashback and combustion thermoacoustic oscillation are two of the major problems in the lean premixed combustors of gas turbine, especially for hydrogen enriched syngas fuels. This paper introduced the experimental results regarding the characteristics research of thermoacoustic oscillation, dynamic heat release and flashback based on a premixed combustion experimental system. The critical flashback equivalence ratio and three dynamic parameters were tested in four types of combustor using eleven kinds of simulated syngas which have the same LHV. Partial flashback and full flashback are observed. With the increase of the hydrogen concentration, the critical equivalence ratio is decreasing and full flashback occurs more easily. The change of nozzle’s geometry structure has a consequent effect on the flashback characteristics. Flashback occurs more easily when the thermoacoustic oscillation is greater, and the corresponding critical equivalence ratio is smaller. Both flashback status and normal status are relative stable combustion within a certain range of equivalence ratio. As the generation and disappearance of the thermoacoustic oscillation and its amplitude-frequency characteristics somehow could be in some randomicity, the critical equivalence ratio is correspondingly not a constant. The dynamic chemiluminescence intensity which indicates the dynamic heat release has a good corresponding relationship in terms of amplitude and frequency characteristics with the dynamic pressure which indicates the thermoacoustic oscillation. Through power spectral density analysis, dynamic pressure and chemiluminescence intensity signals both reflect the dynamic characteristics of the combustor and can be applied in the research of the combustion instability, including the thermoacoustic oscillation characteristics, fluctuation of the chemical heat release rate and flashback characteristics and so on. The results and methods could give some reference to the development of hydrogen enriched gas turbines for future IGCC and poly-generation systems.