Abstract
Keywords Photoacoustics, Exhaust soot measurement, Resonant acoustic cell, Transient measurement, Method comparison
Abstract - The reduction of particulate emission limits, as proposed e.g. in EURO IV and EURO V or in the US 2007 HD regulation, requires new tools for the tuning of engines and novel exhaust aftertreatment systems, like Diesel Particulate Filters (DPF), or Selective Catalytic Reduction (SCR) of Nitrogen Oxides. Time-resolved soot emission monitoring is one of the key features for such developments.
To meet this demand a new equipment for the on-line measurement of soot emitted by combustion engines has been developed. The instrument is based on the photoacoustic principle, which has been optimized to feature the following advantages over currently used soot measuring systems:
Moderate complexity
Design for simple use and installation in engine test cells
No cross-sensitivity to other compounds, like Hydrocarbons, Sulfates or NO2, from which other simple instruments currently used suffer.
The sensitivity of 5 µg/m3 is lower than the US particulate immission standard of 50 µg/m3 in ambient air, and the time resolution is 1 sec. This allows to determine accurately the emission from Diesel engines equipped with DPF or SCR.
In the paper first the principles of measurement are described, and then the verification of the specifications and results from measurements of very low soot concentration in the exhaust gas are presented.