Simultaneous measurement of conserved and reactive scalars in turbulent diffusion flames for assessment of PDF models
- Chung-Hua Polytechnic Inst., Hsin Chu (Taiwan, Province of China). Dept. of Mechanical Engineering
- Vanderbilt Univ., Nashville, TN (United States). Dept. of Mechanical Engineering
Simultaneous measurements of temperature, major species concentrations (H{sub 2}, O{sub 2}, N{sub 2}, H{sub 2}O), and OH concentration have been made in turbulent swirled and unswirled hydrogen jet diffusion flames. These quantities are measured nonintrusively by Raman scattering and predissociative fluorescence induced by a KrF narrowband excimer laser. From the experimental results of the major and minor species concentrations, the simultaneous values of the mixture fraction f and the reaction progress variable q are calculated for each laser pulse assuming a partial-equilibrium model. The measured mean and root-mean-square (rms) OH concentrations are compared to equilibrium and partial-equilibrium values predicted from the instantaneous temperature and major species concentration measurements. The comparisons show strong super-equilibrium OH values in both swirled and unswirled flames. Assumed shape joint probability density function (pdf) combustion models commonly assume that f and q are statistically independent. This assumption is evaluated by calculating the correlation coefficient between f and q from simultaneous measurements of f and q in swirled and unswirled turbulent diffusion flames. The mixture fraction and the reaction progress variable are found to be highly correlated in all the flames, suggesting that statistical independence is a poor assumption. Thus, assumed shape joint pdf models of turbulent combustion that assume statistical independence may incorrectly predict radical concentrations and other nonequilibrium effects.
- OSTI ID:
- 93263
- Report Number(s):
- CONF-940711--
- Country of Publication:
- United States
- Language:
- English
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