Particulate sizing in gas turbine exhausts using a laser extinction technique

Abstract

The measurement of soot particulates densities in gas turbine engine and rocket exhausts is an area of continuing scientific investigation. Knowledge of exhaust plume soot concentration and sizing is critical for plume signature determination, currently a focus of theatre ballistic missile defense research. This thesis research investigates the development and initial calibration of an instrument that will determine soot particle densities in an exhaust plume, by measuring the absorbtion of a light beam transmitted through the plume. This instrument utilizes an argon ion laser, four passes through the exhaust plume, and a phase conjugate crystal to correct for aberrations in the transmitted beam. Several aspects of instrument layout and performance were investigated, and an initial calibration against a conventional probe sampling technique was performed, using an ethelyne air combustor as a soot source. While soot concentration measurements obtained with the instrument were internally consistent, the primitive sample probe used limited the opportunity to do an accurate comparison against a conventional method. The method requires further development, but shows significant promise for use in a jet engine test cell.