Chemiluminescence and DGV measurements on a premixed industrial burner for gas turbines

It is shown that DGV and CH chemiluminescence measurements can be easily combined. By changing one interference filter, using one of the DGV cameras and the DGV optical probe for the visible spectral range CH chemiluminescence measurements are performed with the same optical set up. Even though the CH chemiluminescence intensity is more sensitive to the stoichiometry compared to OH chemiluminescence it gives a time and cost saving volumetric overview on the variation in time of the local heat formation. An application example demonstrates the capability of visualizing the overall flame structure to assure the correct flame symmetry before applying more cost-intensive techniques. Using a standard PC sound card, the microphone signal from the combustor and the camera trigger are recorded allowing a comparison of burner conditions in matters of combustion oscillation frequency, frequency stability and microphone signal amplitude stability over a time period. Probably as a consequence of an asymmetry in the gas supply the studied flame of the test burner showed an asymmetric heat formation and unstable oscillation frequencies. The flame asymmetry was verified also by OH chemiluminescence measurements. Due to the trigger instability it was impossible to realize phase resolved velocity measurements with the standard set up for DGV in flames. Nevertheless time averaged velocity measurements of the flow field were performed which showed in contrast to the chemiluminescence results highly symmetric velocity fields. The signal to background scattering intensity ratio of the DGV set up was improved by the use of black exhaust colour for surface stray light reduction and a water cooled light trap