Experimental Investigation of Turbulence-Chemistry Interaction in High-Reynolds-Number Turbulent Partially Premixed Flames

Abstract

Air Force Materiel Command REPORT DOCUMENTATION PAGEForm Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. (From 09-30-2014 To 03-29-2016 REPORT DATE (DD-MM-YYYY) 06-25-2016 REPORT TYPE Final Report DATES COVERED TITLE AND SUBTITLE[U] Experimental investigation of turbulence-chemistry interaction in high-Reynolds-number DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release, distribution unlimited SUPPLEMENTARY NOTES ABSTRACTThe project focused on implementing the photodissociation-based method for simultaneous two-dimensional imaging of mixture fraction and temperature in turbulent nonpremixed/partially premixed flames. Mixture fraction is an important variable in understanding and modeling turbulent mixing and turbulence-chemistry interaction, two key processes in such flames. Previous techniques are limited by one or more factors including the assumption of simplified flame chemistry, the use of non-inert tracer species, and the use of Raman scattering, thereby incapable of providing two-dimensional mixture fraction imaging in flames. Recently, a new method based on photodissociation of iodine containing species, two-photon laser-induced fluorescence (LIF) of atomic iodine, and Rayleigh scattering was developed by the PI and colleagues at Clemson University, enabling accurate simultaneous two-dimensional imaging in turbulent flames for the first time. The research activities focused on the technical issues in implementing the method, including achieving accurate iodine seeding level, eliminating the interference from LIF of molecular iodine excited at 532 nm and from OH excited at 298 nm, and determination of the system response. Two-dimensional imaging was performed in laminar and turbulent partially premixed methane flames to demonstrate the capability of the new measurement system.