Quantitative hydroxyl time-series measurements from a set of stable and extinguishing turbulent opposed-flow partially premixed CH 4/air flames are used to investigate the effect of Reynolds number and fuel-side equivalence ratio on the structure of turbulent partially premixed flames. The hydroxyl (OH) integral time scale, computed from the autocorrelation function, is used to characterize OH fluctuations and is found to reach a minimum at the axial location of peak OH. Analyses of the duration of and period between bursts in the OH time series are used to examine the dynamics of flame-front motion. In general, with increasing Reynolds number (Re), the distribution in OH burst times shifts towards smaller time scales. A hydroxyl intermittency parameter is also defined from the bursts to quantify the presence or absence of OH. For flames with the same fuel-side equivalence ratio, the hydroxyl intermittency at peak OH remains almost constant when going from stable to extinguishing flames. However, histograms portray an increase in burst separation times for flames displaying occasional extinction events. Hydroxyl time series for a partially premixed flame at a fuel-side equivalence ratio of 2.0 and Re = 6650 are synthesized by using mixture-fraction simulations based on calculated state relationships for OH versus mixture fraction (f). The laminar-flamelet model is employed to explore relations between OH and f so as to predict trends in mixture-fraction time scales.
|Number of pages
|Flow, Turbulence and Combustion
|Published - Apr 2006
Bibliographical noteFunding Information:
Acknowledgements This project was supported by the National Science Foundation, with Dr. Linda Blevins serving as technical monitor. Dirk Geyer and Andreas Dreizler kindly acknowledge financial support through Sonderforschungsbereich 568, Project B1.
- OH concentrations
- Opposed-flow partially premixed flames
ASJC Scopus subject areas
- Chemical Engineering (all)
- Physics and Astronomy (all)
- Physical and Theoretical Chemistry