Restriction for the ELPI in diesel particulate measurements

A dynamic phenomenon that occurs with the measurement of a diluted diesel-s oot aerosol with an electrical low-pressure impactor (ELPI) was studied. An experimental setup for measuring the performance of diesel particulate fil ters was used for this purpose. Impactor overloading is thought to be respo nsible for this dynamic phenomenon. SEM analysis indicates that the fluffy or fractal structure of the diesel-soot aerosol is responsible for rapid ov erloading. A fluffy bed of particles on the impactor surface filters the pa rticle-laden gas stream as it passes over the impactor surface. This phenom enon could lead to improper use of the ELPI and thereby it poses a restrict ion for this application. Users in the field should be aware of this phenom enon because the transient response signal from the ELPI could easily be mi sinterpreted as a start-up effect whereas, in reality, the ELPI is used imp roperly. The use of oil-soaked sintered collectors can be a solution for th is problem. (C) 2001 Elsevier Science Ltd. All rights reserved.