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EFFECTS OF TRANSPORT PROPERTIES AND FLAME UNSTEADINESS ON NITROGEN OXIDES EMISSIONS FROM LAMINAR HYDROGEN JET DIFFUSION FLAMES
Title
EFFECTS OF TRANSPORT PROPERTIES AND FLAME UNSTEADINESS ON NITROGEN OXIDES EMISSIONS FROM LAMINAR HYDROGEN JET DIFFUSION FLAMES.
Creator
Park, Doyoub, Chen, Ruey-Hung, University of Central Florida
Abstract / Description
Experimental studies on the coupled effects of transport properties and unsteady fluid dynamics have been conducted on laminar, acoustically forced, hydrogen jet diffusion flames diluted by argon and helium. The primary purpose of this research is to determine how the fuel Lewis number and the flow unsteadiness play a combined role in maximum flame temperature and affect NOx emission from jet diffusion flame. The fuel Lewis number is varied by increasing/decreasing the mole fraction of...
Show moreExperimental studies on the coupled effects of transport properties and unsteady fluid dynamics have been conducted on laminar, acoustically forced, hydrogen jet diffusion flames diluted by argon and helium. The primary purpose of this research is to determine how the fuel Lewis number and the flow unsteadiness play a combined role in maximum flame temperature and affect NOx emission from jet diffusion flame. The fuel Lewis number is varied by increasing/decreasing the mole fraction of diluents in the fuel stream. Therefore, maximum flame temperatures and then NOx emission levels were expected to differ for Ar- and He-diluted flames. In an investigation of unsteady flames, two different frequencies (10 and 100 Hz) were applied to observe a behavior of NOx emission levels and flame lengths by changes of unsteady fluid dynamics and transport properties.
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Date Issued
2005
Identifier
CFE0000646, ucf:46535
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000646
Laser Spark Ignition of Counter-flow Diffusion Flames: Effects of diluents and diffusive-thermal properties
Title
Laser Spark Ignition of Counter-flow Diffusion Flames: Effects of diluents and diffusive-thermal properties.
Creator
Sime Segura, Fidelio, Deng, Weiwei, Chen, Ruey-Hung, Kapat, Jayanta, University of Central Florida
Abstract / Description
A pulsed Nd:YAG laser is used to study laser spark ignition of methane counter-flow diffusion flames with the use of helium and argon as diluents to achieve a wide range of variations in transport properties. The global strain rate and Damk(&)#246;hler number on successful ignition were investigated for the effects of Lewis number and transport properties, which are dependent on the diluent type and dilution level. A high-speed camera is used to record the ignition events and a software is...
Show moreA pulsed Nd:YAG laser is used to study laser spark ignition of methane counter-flow diffusion flames with the use of helium and argon as diluents to achieve a wide range of variations in transport properties. The global strain rate and Damk(&)#246;hler number on successful ignition were investigated for the effects of Lewis number and transport properties, which are dependent on the diluent type and dilution level. A high-speed camera is used to record the ignition events and a software is used for pre-ignition flow field and mixing calculations. It is found that the role of effective Lewis number on the critical global strain rate, beyond which ignition is not possible, is qualitatively similar that on the extinction strain rate. With the same level of dilution, the inert diluent with smaller Lewis number yields larger critical global strain rate. The critical Damk(&)#246;hler number below which no ignition is possible is found to be within approximately 20% for all the fuel-inert gas mixtures studied. When successful ignition takes place, the ignition time increases as the level of dilution of argon is increased. The ignition time decreases with increasing level of helium dilution due to decreases in thermal diffusion time, which causes rapid cooling of the flammable layer during the ignition process. However, the critical strain for ignition with helium dilution rapidly decreases as the dilution level is increased. The experimental results show that with the increase of strain rate the time to steady flame decreases, and that with the increase of dilution level time for the flame to become steady increases. For the same level of dilution, the time for steady flame is observed to be longer for He-diluted flames than for Ar-diluted flames due to its thermal diffusivity being larger than that of Ar.
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Date Issued
2012
Identifier
CFE0004295, ucf:49467
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004295