Development of techniques to characterize particulates emitted from gas turbineexhausts

Abstract

Particles emitted from aircraft play a role in the formation of contrails and it isessential to characterize them to understand the physical and chemical processesthat are happening. Current methods for measuring aircraft particulateemissions study the reflectance of samples collected in filter papers.Aseries of experiments to more fully characterize particulates has beenperformed on a small-scale gas turbine engine. An intrusive samplingsystem conforming to current ICAO regulations for aircraft emissionswas used with a scanning mobility particle sizer (SMPS). Non-intrusivemeasurements were made using laser induced incandescence (LII) andsamples were taken from the exhaust to analyse using a transmissionelectron microscope. Results obtained from different techniques showed goodagreement with each other. As engine power conditions increased, both theSMPS and LII indicated that the mass of soot had decreased. Differenceswere observed between measurements of diluted and undiluted samples.The mean particle size decreased with dilution but the size distributionbecame bi-modal.The study has shown how significant the samplingenvironment is for measuring particulates and careful techniques needto be used to ensure that accurate, consistent results can be obtained.