Multiscalar measurements of turbulence-chemistry interactions in nonpremixed flames

Selected results from experiments conducted over the past several years involving simultaneous multiscalar point measurements in turbulent nonpremixed flames are reviewed in this paper. In these experiments, spontaneous Raman scattering and Rayleigh scattering measurements of the major species and temperature were combined with laser-induced fluorescence measurements of minor species. The most important feature of these experiments is that they provide detailed data on the instantaneous relationships among species concentration, temperature, and derived scalar quantities that reflect the state of mixing or the progress of reaction. The data allow quantitative comparisons of the thermochemical states in turbulent flames with those in idealized representations, such as steady strained laminar flames, perfectly stirred reactors, or adiabatic equilibrium. The data may also be compared with results (measured or calculated) from unsteady laminar flames and from direct numerical simulations (DNS) of turbulent reacting flows. such comparisons provide insights into the fundamental nature of turbulence-chemistry interactions, and they allow one to examine the validity of some of the basic assumptions that turbulent combustion models are built upon. Furthermore, these data allow quantitative evaluations of the predictive accuracy, strengths, and limitations of a wide variety of combustions models.