Hydroxyl time-scale correlations in turbulent counterflow nonpremixed flames

Krishna K. Venkatesan, Galen B. King, Normand M. Laurendeau, Michael W. Renfro

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Time-series measurements of OH concentration have been obtained in turbulent counterflow nonpremixed H2/CH4/air flames to study the influence of turbulence parameters on the dynamics of such flames by independently varying the Reynolds number (Re) and global strain rate (SR). The autocorrelation functions from the measured time series are found to be self-similar and can be fully characterized by their integral time scales. The integral time scale displays a power law dependence on both Re and SR. At lower strain rates, fluctuations in the OH layer are nearly independent of Reynolds number. An increase in SR changes the spatial displacement of OH, paving the way for faster fluctuations of the OH layer at higher Reynolds numbers. Both the bulk strain rate and Reynolds number scale linearly with the jet exit velocity (U). Furthermore, the combined effect of SR and Re on the integral time scale behaves approximately as U-1.35 in these counterflow nonpremixed flames. Hence, the Re-1.4 dependency previously observed for the OH integral time scale in jet diffusion flames is likely due to a combined effect of jet exit velocity on both strain rate and Reynolds number. Finally, stochastic time-series simulations are used to examine the relationship between time scales for OH and mixture fraction in turbulent nonpremixed flames. We thus demonstrate that integral time scale for mixture fraction is considerably greater for opposed-jet as compared to free-jet flames.

Original languageEnglish
Pages (from-to)787-811
Number of pages25
JournalCombustion Science and Technology
Volume179
Issue number4
DOIs
StatePublished - Apr 2007

Bibliographical note

Funding Information:
Received 14 April 2005; accepted 18 October 2006. This work was supported by the National Science Foundation, with Dr. Linda Blevins serving as technical monitor. We thank Dr. Andreas Dreizler and Dr. Dirk Geyer (Technische Universität, Darmstadt) for providing us with the counterflow burner used for the measurements reported in this study. *Address correspondence to [email protected] Finally, stochastic time-series simulations are used to examine the relationship between time scales for OH and mixture fraction in turbulent nonpremixed flames. We thus demonstrate that integral time scale for mixture fraction is considerably greater for opposed-jet as compared to free-jet flames.

Keywords

  • Counterflow nonpremixed flames
  • OH concentrations
  • Time-series

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • General Physics and Astronomy

Fingerprint

Dive into the research topics of 'Hydroxyl time-scale correlations in turbulent counterflow nonpremixed flames'. Together they form a unique fingerprint.

Cite this