Measurement of Dimensionless Extinction Constant of Soot Generated Using Various Fuels.
Measurement of Dimensionless Extinction Constant of Soot
Generated Using Various Fuels.
Zhou, Z.; Choi, M. Y.
Combustion Institute/Central and Western States (USA)
and Combustion Institute/Mexican National Section and
American Flame Research Committee. Combustion
Fundamentals and Applications. Joint Technical Meeting.
Proceedings. April 23-26, 1995, San Antonio, TX, Gore,
J. P., Editor(s), 87-91 pp, 1995.
Sponsor:National Institute of Standards and Technology,
combustion; soot; fuels; extinction; premixed flames;
Even though the soot volume fraction is a key property
for describing soot both in the flame and above the
flame, there has been little work to verify the accuracy
of measurements by light extinction techniques. Choi et
al studied the effects of source wavelength, scattering
by soot particles, light extinction by 'large' molecules
and the use of different indices of refraction reported
in the literature on the measurement of soot volume
fraction. The experiments indicated that the measured
soot volume fractions were sensitive to the absorption
constant (which was calculated using the reported
refractive indices). For example, at a wavelength of
632.8 nm, the absorption constant can vary by a factor
of two depending on the choice of indices of refraction.
The focus of this paper is on the use of an independent
method for characterizing soot volume fraction to assess
the accuracy and to calibrate the light extinction
method for soot generated using rich premixed flames.
In short, the method consists of isokinetically sampling
the soot at a known flow rate, measuring the mass of
soot collected, and determining the density of the soot
by helium pycnometry. The optical measurements can then
be calibrated with the gravimetric measurements. In
this manner, the dimensionless extinction constant can
be determined without making assumptions regarding the
optical properties of soot which can introduce
significant uncertainties. The accurate measurement of
the dimensionless extinction constant can improve the
usefulness of the optical extinction technique.