Two And Three Dimensional Measurements In Turbulent Nonpremixed Flames

As part of an ongoing research program aimed at developing techniques capable of quantitative imaging of mixture fraction and scalar dissipation in turbulent flames, three-scalar measurements were made in a turbulent nonpremixed flame. The use of nitrogen Raman scattering to detect a passive conserved scalar made it possible to increase confidence in the two-scalar technique based on simultaneous imaging of Rayleigh scattering and fuel Raman scattering. These experiments showed that proper parameterization of mixture fraction-dependent terms appearing in the expression for mixture fraction can improve accuracy for lean values of mixture fraction as well as those near stoichiometric. Additionally, a new experimental technique was investigated which allows the extraction of velocity information from laser-based scalar imaging in turbulent flows. Preliminary results from simultaneous particle-imaging velocimetry (PIV) and optical flow velocimetry showed that this technique has potential for unseeded velocity measurements compatible with the mixture fraction imaging. The optical flow approach was based on extracting velocity vectors from the intensity variations naturally present in inhomogeneous turbulent flow images of a mixing-dependent scalar quantity.