Methodology for measuring exhaust aerosol size distributions from heavy duty diesel engines by means of a scanning mobility particle sizer

A study of the sources of variability in particle size measurements using a dilution minitunnel and a scanning mobility particle sizer (SMPS) has been conducted in order to obtain a comprehensive and repeatable methodology that can be used for measuring the particle size distribution of the exhaust aerosol emitted by a heavy duty diesel engine. The paper includes three experimental phases: an experimental analysis of the SMPS operating parameters' influence; an evaluation of the effect of dilution conditions, such as the dilution ratio and the dilution residence time; and a study of the influence of sampling factors, such as measurement stabilization and the effect of exhaust system pre-conditioning. An examination of the type and degree of influence of each studied factor is presented, recommendations for reducing variability are given and critical parameter values are identified to develop a measurement methodology of low uncertainty that could be applied to a further study concerning the effect of engine operating parameters on the exhaust particle size distribution.