Soot formation is one of the most complex phenomena in combustion science and
an understanding of the underlying physico-chemical mechanisms is important. This
work adopted both experimental and numerical approaches to study soot formation
in laminar counterfl
ow diffusion flames.
As polycyclic aromatic hydrocarbons (PAHs) are the precursors of soot particles,
a detailed gas-phase chemical mechanism describing PAH growth upto coronene for
fuels with 1 to 4 carbon atoms was validated against laminar premixed and counter-
flow diffusion fl
ames. Built upon this gas-phase mechanism, a soot model was then
developed to describe soot inception and surface growth. This soot model was sub-
sequently used to study fuel mixing effect on soot formation in counterfl
ow diffusion
flames. Simulation results showed that compared to the baseline case of the ethylene
flame, the doping of 5% (by volume) propane or ethane in ethylene tends to increase
the soot volume fraction and number density while keeping the average soot size
almost unchanged. These results are in agreement with experimental observations.
Laser light extinction/scattering as well as laser induced
fluorescence techniques
were used to study the effect of strain rate on soot and PAH formation in counterfl
ow
diffusion
ames. The results showed that as strain rate increased both soot volume
fraction and PAH concentrations decreased. The concentrations of larger PAH were
more sensitive to strain rate compared to smaller ones. The effect of CO2 addition on
soot formation was also studied using similar experimental techniques. Soot loading
was reduced with CO2 dilution. Subsequent numerical modeling studies were able to
reproduce the experimental trend. In addition, the chemical effect of CO2 addition
was analyzed using numerical data.
Critical conditions for the onset of soot were systematically studied in counterfl
ow
diffusion
ames for various gaseous hydrocarbon fuels and at different strain rates. A
sooting temperature index (STI) and a sooting sensitivity index (SSI) were proposed
to present the sooting tendencies of different fuels and their sensitivities to strain
rates.
| Identifer | oai:union.ndltd.org:kaust.edu.sa/oai:repository.kaust.edu.sa:10754/306502 |
| Date | 11 1900 |
| Creators | Wang, Yu |
| Contributors | Roberts, William L., Physical Science and Engineering (PSE) Division, Chung, Suk Ho, Im, Hong G., Raj, Abhijeet, Sarathy, Mani |
| Source Sets | King Abdullah University of Science and Technology |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Rights | 2014-11-30, At the time of archiving, the student author of this dissertation opted to temporarily restrict access to it. The full text of this dissertation became available to the public after the expiration of the embargo on 2014-11-30. |
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