The near-field turbulent structure of double-concentric hydrogen-air jet diffusion flames, with or without swirl, has been investigated using conditionally sampled, three-component laser-Doppler velocimetry and coherent anti-Stokes Raman spectroscopy. The turbulent flame zone became thinner and shifted inward as the mean jet velocity was increased, whereas swirl created a radial velocity even at the jet-exit plane, thereby broadening and shifting the flame zone outward. The probability-density functions of velocity components, their 21 moments (up to fourth order), mean temperature, and root-mean-square temperature fluctuation were determined in the near field. The data can be used to validate advanced turbulent combustion models.
An experimental investigation of the effects of nozzle ellipticity on the flow structure of co-flow jet diffusion flames