Differential diffusion effects on measurements in turbulent diffusion flames by the Mie scattering technique

The effect of differential diffusion (DD) between fuel atoms and marker particles in Mie-scattering measurements of scalar parameters in turbulent flames is investigated theoretically, and techniques for error correction are proposed. The analysis method of Bilger (1981) is applied to a horizontal hydrogen jet flame at 151 m/sec into coflowing air at 15.1 m/sec, the jet Reynolds number (Rej) being 10,850. The results of error analysis are presented graphically and discussed. The DD effect is shown to be small for isothermal flows at Rej of 10,000 or more, but to be several percent for diffusion flames at the same Rej and large in the case of hydrogen diffusion flames at Rej below 10,000: the rms errors of mean mixture fraction and fluctuation exceed 10 and 20 percent, respectively. The generalized formulation used permits the application of these results to the correction of errors in published results or improved planning of future studies.