Experimental Analysis of lean premixed natural gas-air high swirl flame chemiluminescence and flame spectrum in visible wavelengths

According to necessity of measuring combustionparameters of a combustion system such as gas turbinesusing simple and practical methods, in this paper,chemiluminescence of lean premixed natural gas-air highswirl flame of a high swirl burner which is a prevalentburner for gas turbines is analyzed. Visible wavelengthrange of the spectrum is then compared with flame color,using flame image processing and study of RGBcomponents of flame image, especially for excitedspecies such as CH* and C2*. Results are analyzed atatmospheric pressure condition, equivalence ratio rangeof 0.4 to 0.8 (lean state), nominal power of 21 kW andswirl number of 0.69. The results from spectroscopyshow that because of gaseous lean premixed combustion,chemiluminescence intensities of excited species aremuch smaller in visible wavelengths. Also in mentionedequivalence ratio range, reaction zone average intensitiesof CH* and C2* chemiluminescence have the same trendof total reaction zone average intensities of blue andgreen color respectively. In the end, a fourth-orderpolynomial was introduced to obtain reaction zoneaverage intensities of CH* and C2* chemiluminescence,using blue and green color intensities respectively andthis can be done only by using a digital camera

Keywords:

High swirl flame , Chemiluminescence , Image processing , Lean premixed combustion