On the structure of premixed flames subjected to extreme levels of turbulence
AARON W. SKIBA, DOCTOR OF PHILOSOPHY, AEROSPACE ENGINEERING
Developing next-generation propulsion and energy production devices that are efficient, cost-effective, and clean will require highly-accurate, robust, yet computationally tractable turbulent premixed combustion models. The accuracy and reliability of such models rest upon a deep fundamental understanding of the effects turbulence has on the structure and dynamics of turbulent premixed flames. However, such understanding is currently lacking, particularly at the high turbulent Reynolds number (ReT) conditions found in practical combustion devices. Thus, this dissertation aims to elucidate the fundamental effects of turbulence on the structure of premixed flames.
To this end, high-fidelity flame structure measurements were applied to premixed methane–air Bunsen flames subjected to extreme levels of turbulence. Specifically, 28 cases were studied with turbulence levels (u'/SL) as high as 246, turbulent Karlovitz numbers (KaT) as large as 533, and ReT values up to and 99,000. Average preheat layer thicknesses are found to increase with increasing u'/SL and with axial distance from the burner (x/D). In contrast, average reaction layer thicknesses did not vary appreciably with either u'/SL or x/D. The reaction layers are also observed to remain continuous; that is, local extinction events are rarely observed.
The results presented in this study, as well as those from previous studies of turbulent premixed flames, are used to assess previously accepted phenomenological hypotheses. Such hypotheses, heretofore, were thought to bound regimes in which particular classes of turbulent premixed combustion models were believed to be superior to others. Based on this assessment, new hypotheses are proposed that are both more physically sound and more consistent with experimental results than previous theories.
- Chair: Professor James F. Driscoll
- Cognate: Professor Volker Sick (Mechanical Engineering)
- Dr. Campbell D. Carter (Air Force Research Laboratory)
- Assistant Professor Mirko Gamba
- Associate Professor Venkat Raman
7. A.W. Skiba, T.M. Wabel, C.D. Carter, S.D. Hammack, J.F. Driscoll, “Premixed flames subjected to extreme levels of turbulence part II: Flame structure in temperature space and implications for models,” (In preparation for Combust. and Flame).
6. A.W. Skiba, C.D. Carter, S.D. Hammack, T. Lee, “Brief Communication: Multi-scalar imaging in turbulent premixed methane–air flames via readily assessable diagnostic equipment,” (In preparation for Combust. and Flame).
5. A.W. Skiba, T.M. Wabel, C.D. Carter, S.D. Hammack, J.E. Temme, J.F. Driscoll, “Premixed flames subjected to extreme levels of turbulence part I: Flame structure and a new measured regime diagram,” (submitted to: Combust. and Flame).
4. A.W. Skiba, T.M. Wabel, C.D. Carter, S.D. Hammack, J.E. Temme, T. Lee, J.F. Driscoll, “Reaction layer visualization: a comparison of two PLIF techniques and advantages of kHz-imaging,” Pro. Combust. Inst. 36 4593-4601
3. T.M. Wabel, A.W. Skiba, J.F. Driscoll, “Turbulent Burning Velocity Measurements – Extended to Extreme Levels of Turbulence,” Pro. Combust. Inst. 36 1801-1808
2. T.M. Wabel, A.W. Skiba, J.F. Driscoll, “Measurements to Determine the Regimes of Premixed Flames in Extreme Turbulence,” Pro. Combust. Inst. 36 1809-1816
1. A.W. Skiba, L. Zeng, B.K. Arbic, M. Müller, W.J. Godwin, “On the resonance and shelf/openocean coupling of the global diurnal tides,” Journal of Physical Oceanography 43, doi:10.1175/JPO-D-12-054.1, 1301-1324
Refereed Conference Proceedings with Presentations
6. A.W. Skiba†, T.M. Wabel, J.E. Temme, J.F. Driscoll, “Experimental Assessment of Premixed Flames Subjected to Extreme Turbulence,” 54th Aerospace Sciences Meeting, San Diego, California, January 2016
5. A.W. Skiba†, T.M. Wabel, J.E. Temme, J.F. Driscoll, “Measurements to Determine the Regimes of Turbulent Premixed Flames,” 51st Joint Propulsion Conference, Orlando, Florida, July 2015
4. T.M. Wabel†, A.W. Skiba, J.E. Temme, J.F. Driscoll, “Highly Turbulent Premixed Flame Structure – Integral Length Scale Effects,” 9th U.S. National Combustion Meeting, Cincinnati, Ohio, May 2015
3. J.E. Temme, A.W. Skiba†, T.M. Wabel, J.F. Driscoll, “Measurements of Premixed Turbulent Combustion Regimes of High Reynolds Number Flames,” 53rd Aerospace Sciences Meeting, Orlando, Florida, January 2015
2. J.E. Temme, A.W. Skiba, T.M. Wabel†, J.F. Driscoll, “Experimental Investigation of Premixed Turbulent Combustion in High Reynolds Number Regimes using PLIF,” 52nd Aerospace Sciences Meeting, National Harbor, Maryland, January 2014
1. E. Temme†, A.W. Skiba, T.M. Wabel, J.F. Driscoll, “Premixed Turbulent Combustion in High Reynolds Number Regimes – of Thickened Flamelets and Distributed Reactions,” 8th U.S. National Combustion Meeting, Park City, Utah, May 2013† Indicates presenter