Turbulence-Chemical Kinetic Interactions in Laboratory Flames.
Final rept. 16 Jan-15 Nov 70,
AEROCHEM RESEARCH LABS INC PRINCETON N J
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In order to determine the significant interactions between turbulence and charged species kinetics at high temperatures, charged species density fluctuations were investigated in a 1-atm turbulent propaneair flame. Measurements of mean and rms positive ion and electron densities, spatial correlations and power spectra, and mean velocity and temperature were taken in both clean and potassium-seeded flames. It was shown both theoretically and experimentally that the chemi-ion recombination rate in the clean turbulent flame is enhanced over the well-known laminar recombination rate as a result of fluctuations in positive ion and electron density. In addition, it was demonstrated theoretically that alkali-metal recombination should also be influenced by turbulent fluctuations. The dominant source of charged species fluctuations was found to be radial gradients of the mean positive ion and electron concentrations. One indication of this was the increase in turbulent intensity with increasing seeding level. The correlations and power spectra of the fluctuations were found to be similar to those measured for nonreactive species. The correlation coefficients are exponential the power spectra exhibit a -2 power dependence on frequency within the inertial-convective subrange. No influence of ionization nonequilibrium on the correlations or spectra was observed. This is consistent with the observation that the chemical time scales are greater than the turbulent time scales in this flame. Author
- Plasma Physics and Magnetohydrodynamics