Experimental Characterization of Premixed Flame in Gas Turbine Combustor With Spectroscopy and RGB Analysis

Abstract

Gas turbine combustion has been one of the principal sources for power generation and propulsion systems. Recent research thrust on flame monitoring for characterization of flame behavior has gained prominence for several reasons — notably for performance of combustor in aerospace propulsion and power plant applications, reduction in pollutant levels like NOx, and fire safety engineering, Lean air-fuel mixture leads to efficient combustion with lesser emissions, albeit with risk of Lean blow out (LBO). Flame monitoring is done to find out LBO point-which occurs by progressively varying the Air-fuel ratio or equivalence ratio. The current paper monitors the characteristics of lean premixed, swirl-stabilized, LPG fueled, dump combustor with the help of spectroscopy and high resolution camera images. Chemiluminescence is being used for determination of combustion characteristics. The spectroscopic peaks for chemical species like - OH* and CH* radicals and water vapor are found at varying parameters like air-fuel premixing and equivalence ratio. Blow off characteristics which occur in gas turbine combustor when going from rich to lean mixture are investigated. The comparison of the averaged red, green and blue (R, G, B) values has been done by graphical representation. The spectroscopic data are co-related with the RGB analysis results- and the location of spectroscopic peaks of intensities and their correspondence with electromagnetic spectrum in investigated. The behavior of peak intensities of Red, Green, Blue alongwith irradiation by chemical species – with the change in parameters like air flow rate, fuel flow rate or equivalence ratio and the extent of air-fuel premixing are investigated. Metrics for detecting the approach of impending LBO are proposed from the spectroscopic results.