Temperature measurements were performed at 5 kHz using chirped-probe pulse (CPP) femtosecond coherent anti-Stokes Raman scattering (CARS) thermometry of nitrogen in a piloted spray burner. The effect of airblast velocity on axial temperature profiles along the centerline of dilute spray flames for a fixed liquid loading was examined. The Sydney Needle Spray Burner (SYNSBURNTM) delivered 75 g/min liquid acetone through a 686-µm-ID needle recessed 80 mm upstream of the exit plane into a 10-mm-ID air-blast tube flowing air at velocities of 36 to 66 m/sec. At each data point (17 heights for each of 6 flames) 2300 shots were acquired, which generated approximately 400 ms of temperature history after data processing and filtering. The CPP fs-CARS temperature measurement technique and system performance are discussed. Precision and accuracy error of the technique are assessed between 2 and 6% over the temperature range of interest. Average temperature profiles are discussed and show clear trends of lower peak temperatures with air-blast velocity. Trends in normalized temperature fluctuations over two regimes were observed and are discussed. Fourier analysis of the calibration flame from previous research identified a strong oscillation at 273.4 Hz, but was not present for any calibration flames used for data presented in this paper. Power spectral densities of temperature histories showed no dominant frequencies below 1,000 Hz. Further data sets with radial and axial profiles have been taken at other needle recess lengths for acetone and ethanol sprays as well as premixed methane flames, and sooting ethylene diffusion flames.
|Title of host publication
|10th U.S. National Combustion Meeting
|Eastern States Section of the Combustion Institute
|Published - Jan 1 2017