Characterization of Flame Behavior and Blowout Limits at Different Air Preheating Temperatures in Plasma Assisted Stabilized Combustor

This study investigates the flame characterization near to lean blowout (LBO) limits at different pre-heating temperatures in lifted swirl methane-air plasma discharge stabilized flame. The combustor was equipped with a needle-ring type plasma actuator driven by a sinusoidal generator at 20 kHz directly coupled with methane-air premixed flame close to the injector exit. The needle electrode connected with high voltage (HV) and the nozzle acted as a grounded electrode. The electrical characterizations of combustion characteristics and LBO measurements have been carried out at different plasma power, air preheating temperatures, and air mass flow rates. Flame shape and intensity in the flame area have been analyzed based on the images acquired by using a high-resolution camera. Acoustic measurements were performed using high sensitivity microphone. Furthermore, post-processing of the microphone data involved the application of Fast Fourier Transform (FFT) and the wavelet decomposition to identify and characterize any periodic phenomena present in the system. It has been perceived that when the plasma is on, LBO limits were extended significantly. The maximum reduction of equivalence ratio at LBO was noticed in terms of percentage (79.4%) at 40% voltage amplitude, T = 373 K, and ma = 6 m3/h. Proper orthogonal decomposition was implemented on the high-speed chemiluminescence images and the frequency analysis of the time coefficients of the modes of the POD permits the identification of the dominant frequency ranges in the different operating conditions. The results were in good agreement with the findings of the FFT and Wavelet analysis on the microphone measured signals.