Emission spectroscopy of OH* has been utilized to measure temperatures in the wake of a bluff body stabilized conical turbulent premixed flame. Temperatures were determined based on the normalized intensities of two groups of unresolved rotational lines of OH* at 306.37 nm and 306.74 nm with respect to the one at 309.00 nm. This technique coupled with Abel's deconvolution enabled determination of spatial distribution of gas temperature through the bluff-body wake region at nominal mixture approach velocities of 11 and 16 m/s as a function of equivalence ratio and upstream oscillation frequency. Results indicate that the average recirculation zone temperatures are fairly uniform and correspond to 90% of the adiabatic flame temperature at a given equivalence ratio. Effect of flow modulation on the wake temperatures and its spatial distribution is not discernible except for 300 Hz case. A higher gradient of temperature exists in this case presumably due to the change in the recirculation zone structure around a Strouhal number between 0.2 and 0.3. The time-averaged profiles and thicknesses of the chemiluminescence zone of OH* were also determined from the emission data. It is found that the OH* intensity increases with increasing excitation frequency as well as widening of the profile and the peak location shifting to a slightly larger radial position.
展开▼
