Abstract
Currently, standards governing particle emissions are mass based. However, in future regulations particle mass concentrations approach sensitivity limits of mass based measurement methods, e.g. filter sampling and TEOM©.
The new base for standards in the future could be particle number or active surface concentration for given particle size range, since these measures have been reported to relate to fine particle health effects. Furthermore, it is desirable for the new method to measure real time emissions, since the transient test cycles are becoming practice in emission measurements.
Dekati Ltd. has developed an on-line active surface monitor (ASMO). This device has a selectable precut impaction stage in the inlet. After the precut stage, the incoming particles are charged with a corona charger with determined charging efficiency and subsequently the total charge carried by the collected particles is measured with a high accuracy electrometer.
ASMO provides information on active surface area. Simultaneously, the measured ASMO current result is the same as integrated ELPI current (ELPI= Electrical Low Pressure Impactor, manufactured by Dekati Ltd.). Consequently, ASMO and ELPI measurements can be repeated for various vehicles and measurement conditions and the results can be compared.
In this study, the road tests have been simulated by using the vehicle dynamometer, and sampling has been made by using VERL full-size dilution tunnel. Sampling method during on real road testing should closely mimic the methods applied during laboratory testing. However, since the resources for e.g. pressurised dilution air, cooling water etc. are not available during on road testing, the sampling method needs design and construction.
In this preliminary study the technical construction of on-board particle monitoring device is described in more detail. In addition to that measured data will be presented and discussed