Abstract/Details

Molecular-beam mass spectrometry of ethylene and cyclohexane flames


2005 2005

Other formats: Order a copy

Abstract (summary)

Molecular-beam mass spectrometry (MBMS) is a technique that is used to measure stable and radical species within flames, and thus it is a strong tool for understanding the formation and destruction pathways of precursors to PAH and soot. Using MBMS and modeling techniques, three well-chosen premixed flat flames have been characterized.

Fuel-lean ethylene flames with and without added allene were mapped to help elucidate the C3H3 self-combination route to benzene formation, and a cyclohexane flame was characterized due to the abundance of cyclohexane within real fuels such as gasoline. Benzene is the precursor to PAH and soot whose formation is the rate-limiting step, and thus knowledge of its formation route is paramount.

The flames characterized include an undoped fuel-lean (&phis; = 0.70), C2H4/O2/56.4% Ar flame (30.00±0.01 Torr and ub-300 = 30.6 cm/s), an allene-doped fuel-lean (&phis; = 0.69), 0.19 % C3H4/C2H 4/O2/56.54 % Ar flame (30.00±0.01 Torr and ub-300 = 30.6 cm/s), and a stoichiometric (&phis; = 1.00) cyclohexane/O2/32.5% Ar flame (30.00±0.01 Torr and ub-300 = 35.0 cm/s). Mole fraction profiles of 31, 35, and 70 stable and radical species were measured within the three flames, respectively. They are modeled with overall good agreement between the model and data.

Comparison of both fuel-lean ethylene flames shows that benzene was detected in the allene-doped flame but not in the undoped ethylene flame, strongly suggesting the importance of C3 routes to benzene. Reaction path analysis showed that benzene in the allene-doped flame is mainly formed through propargyl self-combination as described by the kinetics of Miller and Klippenstein (2003). Examination of the cyclohexane flame showed high concentrations of benzene. A reaction path analysis showed that benzene is mainly formed instead by the dehydrogenation of cyclohexane.

Experiments done at the Advanced Light Source of Lawrence Berkeley National Laboratory show that the isomeric C6H6 composition in the allene-doped flame consisted of 20% fulvene, 45% benzene and 35% 1,5-hexadiyne, while the cyclohexane flame consisted of 99.5% benzene and 0.5% fulvene. This difference in isomeric composition strongly points to the difference in benzene formation pathways in the two fuels.

Indexing (details)


Subject
Chemical engineering;
Analytical chemistry
Classification
0542: Chemical engineering
0486: Analytical chemistry
Identifier / keyword
Applied sciences; Pure sciences; Cyclohexane; Ethylene; Flames; Molecular beam mass spectrometry
Title
Molecular-beam mass spectrometry of ethylene and cyclohexane flames
Author
Law, Matthew E.
Number of pages
667
Publication year
2005
Degree date
2005
School code
0118
Source
DAI-B 66/11, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542382888, 0542382881
Advisor
Westmoreland, Phillip R.
University/institution
University of Massachusetts Amherst
University location
United States -- Massachusetts
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3193916
ProQuest document ID
304999837
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/304999837
Access the complete full text

You can get the full text of this document if it is part of your institution's ProQuest subscription.

Try one of the following:

  • Connect to ProQuest through your library network and search for the document from there.
  • Request the document from your library.
  • Go to the ProQuest login page and enter a ProQuest or My Research username / password.