Bourns Hall

Lea D. Chen Department of Mechanical & Industrial Engineering and National Advanced Driving Simulator The University of Iowa A Joint Experimental and Numerical Study of Stabilization of Diluted Methane Non-Premixed Laminar Flames in Co-Flowing Air Abstract A joint experimental and numerical study of the stabilization limits of laminar non-premixed flames was conducted. A methane and nitrogen mixture (50% on volume basis) was used as the fuel. The primary objective of this study was to determine the effect of buoyancy on the stabilization of round, laminar, gas-jet non-premixed flames in a coflow air duct. Experiments were conducted in both microgravity and normal-gravity environments. The results were used to map the liftoff and blowout stabilization limits as a function of the fuel and air velocities for these environmental conditions. The experimental results verified the hypothesis that substantially greater velocities are required to destabilize the flame in microgravity. The increase in air velocity required to induce liftoff in microgravity (compared to normal gravity) was roughly equal to the increase required to induce blowout in microgravity. Furthermore, the air velocity increase was relatively independent of the fuel flow, except at low fuel flows. At high fuel flows, the microgravity flames tend to immediately blow out after lift off, in agreement with the free-jet theory of Chung and Lee (1991) for fuels with a Schmidt number less than 0.7. However, stable lifted flames were achieved within a coflow duct in microgravity at low fuel flows and in normal gravity, different from that predicted by Chung and Lee (1991) but consistent with Ghosal and Vervisch (2001). A numerical code with adaptive mesh refinement was developed and used to solve the transport equations, including the finite rate chemistry based on a four-step reduced mechanism. The numerical calculation was able to predict the qualitative flame behavior and blowout conditions in zero gravity. The calculated blowout conditions were in quantitative agreement with microgravity results for fuel jet velocity below 0.2 m/s, but only in qualitative agreement for higher fuel jet velocities. Also will be presented are the experimental results of the effects on the flame stabilization when different inert species is used to replace nitrogen in the fuel stream. Biosketch L.-D. Chen, Director of the National Advanced Driving Simulator (NADS) and Professor of the Department of Mechanical and Industrial Engineering at The University of Iowa, earned his baccalaureate degree in mechanical engineering from The National Taiwan University, Taipei, Taiwan, in 1974, and his masters of science and doctoral degrees from The Pennsylvania State University, University Park, Pennsylvania in 1979 and 1981, respectively. After receiving his doctoral degree at Penn State, Chen was appointed a research associate at the Applied Research Laboratory and a non-tenure track assistant professor of mechanical engineering at Penn State. Chen joined the faculty of The University of Iowa in 1982 as an assistant professor in mechanical engineering, and was promoted to associate professor with tenure in 1986 and professor in 1991. Chen was appointed the interim department chair of mechanical engineering in 1992, department chair in 1993-1998. In 1998, he was appointed the NADS Interim Director and NADS Director in 1999. He is also the Director of the National Science Foundation’s Industry/University Cooperative Research Center for Virtual Proving Ground Simulation at The University of Iowa, 2003-present, and Iowa Site Director, 2001-present. Chen’s research interest includes experimentation and simulation of combustion and propulsion systems, fuel cells, airbags, and person-in-the-loop simulation. His research has been funded by government and industrial sources, including the National Science Foundation, the Air Force Office of Scientific Research, the Air Force Research Laboratory, the Office of Naval Research, and the National Aeronautics and Space Administration (NASA). Chen’s NASA project was selected as one of the investigations that were on-board of the US NASA Mission STS-87/USMP-4 in November/December 1997. Industrial sponsors include Deere & Co., GM, Honda Motor Company, Cummins Engine and ConocoPhillips Company. Chen teaches both undergraduate and graduate level courses at The University of Iowa, and developed new courses in the mechanical engineering (ME) curriculum, including fuel cells and combustion and propulsion courses. Chen is currently the faculty coordinator of the Elective Focus Area in Energy and Utilization in the ME undergraduate curriculum at The University of Iowa. Chen has co-authored or authored more than 100 technical publications, and is active in national ad international professional societies. Chen is a member of the American Society for Engineering Education, American Society of Mechanical Engineers, American Society of Automotive Engineers, American Institute of Aeronautics and Astronautics, Transportation Research Board and other societies, and The Combustion Institute. He has been on the Board of Advisors of the Central States Section of The Combustion Institute (CSSCI) since 1998. He is currently the Chair-Elect of the CSSCI (2003-2004) and will be the Chair of the CSSCI for 2005 to 2009. Monday, July 19, 2004 Bourns Hall, Room A265 10:45 a.m.-11:30 a.m. (Refreshments will be served at 10:30 a.m.)