Correlation of measurements OH*, CH*, C2* and H2O with changing signal of Electrical Capacitance Tomography system in the reaction zone of methane/air premixed flames

Research into the application of Electrical Capacitance Tomography (ECT) carried out in the Laboratory of the Aircraft Engines Division at Warsaw University of Technology has shown that it is applicable to recognition of various flames. Several cases were tested using the ECT system and the system successfully created cross sectional images of premixed and diffusion flames. Studies were then conducted which significantly increased the functionality of the system. This article describes experimental studies that afforded insight into the effects of the degree of ionization generated during the combustion process on the changing signal of the ECT system. Research was carried out in an experimental stand consisting of a burner, 6 and 12 electrodes capacitance sensors and an optical spectrometer. Burner injection was used to obtain stability of combustion. Two rotameters were installed in the inlet of the burner. The flow rate of air and methane was used to determine the composition of the combustible mixture formed in the mixing chamber. A grating spectrometer was used to perform a detailed analysis of combustion processes and to detect various types radicals. This experimental test focused on measuring chemiluminescence intensities and possible correlations of the OH*, CH*, C-2* and H2O with air/methane ratio. The data from the ECT system and optical spectrometer was then analyzed. It was found that the strong correlations between the peak intensity of OH*, CH*, C-2* and H2O in the reaction zone to the equivalence ratio could be used to investigate the local flame stoichiometry.