A TECHNIQUE FOR MIXTURE FRACTION IMAGING IN TURBULENT NONPREMIXED FLAMES

A technique is presented for making instantaneous, two-dimensional mea surements of the mixture fraction in turbulent nonpremixed flames. The technique uses acetaldehyde fluorescence imaging and Rayleigh imaging to determine the mixture fraction in an iterative manner. Preliminary experimental results for the mixture fraction and its gradient in a t urbulent acetaldehyde flame are presented. To verify the degree to whi ch the acetaldehyde fluorescence tracks the fuel concentration, simult aneous fluorescence and fuel Raman scattering measurements are perform ed. The strength of the signals from the Rayleigh scattering and the f uel fluorescence allows computations of the mixture fraction high in s patial resolution and low in noise, thus making determination of the s calar dissipation feasible.