Simultaneous measurement of temperature and fuel mole fraction using acetone planar induced fluorescence and Rayleigh scattering in stratified flames

The use of acetone as a tracer for planar laser induced of fluorescence (PLIF) measurements is very popular both for mixing investigations and for premixed or partially premixed combustion systems when evaluating the local mixture fraction (or equivalence ratio) in the fresh gases. The local structure of a flame front can be investigated by using Rayleigh scattering, and this technique has been quite frequently used in combustion. We present here an application of simultaneous imaging of temperature and fuel mole fraction with both acetone PLIF and Rayleigh scattering techniques. The strong influence of temperature on fluorescence signals can be corrected if the local temperature is known. Simultaneously, the contribution of the acetone Rayleigh cross-section can be evaluated through the local value of acetone mole fraction. An iterative process enables the fuel mole fraction (in the limit of the preheat zone) and temperature fields to be obtained in a reactive configuration. The technique is limited by the maximum temperature that can be corrected and by the tracer specificities. Tests in laminar homogeneous stabilized flames and in stratified stabilized flames demonstrate the ability to record the instantaneous flame structure and fuel mole fraction field. Finally, the paper presents correlations of the local flame thickness with the local methane mole fraction, which underline the strong influence of large scales of the equivalence ratio on the local flame structure.