Experimental investigation of flame state transition in a gas turbine model combustor by analyzing noise characteristics

Abstract

Hysteresis of flame transition from lifted (V-shaped) to flat form is studied in a gas turbine model combustor by using acoustic measurements in connection with infrared thermometry and visual recordings. The impacts of varying several parameters including the shape of the fuel injector, flow rates, confinement (i.e., combustion chamber), and air preheat on flame shape transition and the corresponding acoustic behavior are studied using experimental measurements. It is shown that the flat flame produces noise at two dominant frequencies (related to the acoustics and hydrodynamic instabilities), and these frequencies could be used for flame shape transition prediction from the V-shaped flame, which produces different frequencies. Time–frequency wavelet analysis of the generated noise shows highly non-stationary behavior with mode hoppings for both flame states. The results show that the flame state transition hysteresis is highly dependent on the parameters that change the details of flow near the baseplate, and in this way, the higher flow rates, air preheat, and round slit injector intensify the transition hysteresis. Also, the presence of the combustion chamber was shown to be very effective in reducing the studied hysteresis.