MEASUREMENT OF DIMENSIONLESS SOOT EXTINCTION CONSTANT USING A GRAVIMETRIC SAMPLING TECHNIQUE

The dimensionless extinction constant, K-e, of post-flame soot from ri ch acetylene/air premixed flames was measured using a simultaneous gra vimetric-sampling and light extinction technique at a wavelength of 63 2.8 nm. The average value of K-e is 8.5 with a standard deviation of 0 .5. An important improvement in the present method include the reducti on in the uncertainty of the extinction pathlength and uniformity of t he soot concentration in the probed region. Several aspects of the exp erimental procedure which can potentially introduce errors in the meas ured K-e were evaluated. Results indicate that K-e is only moderately influenced by the sampling flowrate and that the variation is minimize d when flowrates are maintained close to isokinetic conditions. It is demonstrated that moisture condensation within the sampling probe, if disregarded, can produce large errors in K-e. (C) 1998 Elsevier Scienc e Inc. All rights reserved.