Abstract:

The effect of electric fields on the instability of laminar nonpremixed jet flames was investigated experimentally by applying the alternating current (AC) to a jet nozzle. We aimed to elucidate the origin of the occurrence of twin-lifted jet flames in laminar jet flow configurations, which occurred when AC electric fields were applied. The results indicated that a twin-lifted jet flame originated from cold jet instability, caused by interactions between negative ions in the jet flow via electron attachment as O2+e=O2– when AC electric fields were applied. A shedding frequency of jet stream due to AC driven instability showed a good correlation with applied AC frequency exhibiting a frequency doubling. However, for the applied AC frequencies over 80 Hz, the jet did not respond to the AC, indicating an existence of a minimum flow induction time in a dynamic response of negative ions to external AC fields. Detailed regime of the instability in terms of jet velocity, AC voltage and frequency was presented and discussed. Hypothesized mechanism to explain the instability was also proposed. Also, the effect of applying non-thermal plasma (NTP) (by adopting a dielectric barrier discharge) to a lean premixed model gas turbine combustor on flame stability and emissions of NOx and CO has been investigated experimentally by varying mixture nozzle exit velocity and equivalence ratio. Applying NTP to the combustor extended the lean flammable limit, and augmented the flame stability. It was also found that it resulted in increase of NOx emission slightly (however, having a maximum of 10 ppm) and reduction of CO emission significantly due to exalting complete burning. These results suggest that applying NTP to a gas turbine combustor should be a useful tool to simultaneously reduce both emissions of NOx and CO.

Brief Biography:

Dr. Jeong Park holds a B.S. degree in Mechanical Engineering from the Seoul National University (1987) and M.S. (1990) and Ph.D (1995) degrees in Mechanical Engineering from the Korea Advanced Institute of Science and Technology (KAIST). He was a post doctoral research associate at KAIST (1997-1999) and a guest researcher at the Tohoku University in Japan (1997-1998). He then joined the Korea Aerospace Research Institute as a senior researcher (1999-2000). He taught and studied the general area of flame structure in combustion field and rocket propulsion system (2000-2006) at Sunchon National University. He was a guest scientist at National Institute of Science and Technology in U.S.A. (2004-2005). He joined the Department of Mechanical Engineering at Pukyong National University in 2007. His research interests include flames, microgravity combustion, rocket engine, fire and explosion, coal combustion, and electric field assistant combustion. He was the recipient of Excellent Researcher of KOSEF (1997) and Young Investigators Awards at ASPACC-99. He has authored over 70 publications in SCI Journals. He is now a vice president in Korean Society of Combustion Engineers (KOSCO) and a vice president (2014-president) in Korean Society of Microgravity (KSM). He is the editor or in the editorial board of several journals.

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