The combined investigation of the flame dynamics of an industrial gas turbine combustor using high-speed imaging and an optically integrated data collection method

In this paper, innovative investigation of the flame dynamics of an industrial gas turbine combustor using high-speed imaging and flame luminosity measurement has been reported. Both digital and optical integration methods have been applied to study the flame dynamics of an unstable combustion mode, which has a fixed peak frequency around 105 Hz. It is found that the light emission of the seeded combustion possesses the same dominant peak frequency as the acoustic emission. On the other hand the natural flame light emission failed to match the spectrum of the acoustic emission due to signal drop-out, which is a common problem for direct imaging of unseeded flame. The paper has demonstrated that the transition from stable to unstable combustion could be captured successfully by high-speed imaging using a pre-trigger mode. Three stages of transition from stable combustion mode to unstable mode have been identified. In stage one, the flame luminosity and fluctuation increased gradually, which could be assumed as the incipiency of the instability. In stage two, there was a sudden and sharp burst in flame luminosity, which indicates that the combustion process was becoming very intense in the middle of transition. In the third stage, the drastic flame luminosity dissipated slightly and oscillated with constant amplitude and the combustion locked to unstable combustion mode. The two applied techniques have been cross-checked with reference to the unique peak frequency observed.