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Recently, it was reported that the atmospheric pollution levels of nitrogen dioxide (NO2) and particulate matter (PM) are not decreasing despite the introduction of stricter vehicle emission regulations. The difference between conditions of the test cycles defined by the vehicle emission regulations and the real driving can contribute to the differences between expected and actual pollution levels. This has led to the introduction of in-use vehicle emission monitoring and regulations by means of a portable emission measurement system (PEMS). An optimized on-board PM analyzer was developed in this study. The on-board PM analyzer is a combination of a partial flow dilution system (PFDS) particulate sampler and a diffusion charger sensor (DCS) for real-time PM signals. The measuring technology and basic performance of the analyzer will be explained. Acceleration of the vehicle can cause uncertainty of flow measurement in the PM sampler.

The particle number (PN) emission regulation has been implemented since 2011 in Europe. PN measurement procedure defined in ECE regulation No. 83 requires detecting only solid particles by eliminating volatile particles, the concentrations of which are highly influenced by dilution conditions, using a volatile particle remover (VPR). To measure PN concentration after the VPR, a particle number counter (PNC) which has detection threshold at a particle size of 23 nm is used, because most solid particles generated by automotive engines are considered to be larger than 23 nm. On the other hand, several studies have reported the existence of solid and volatile particles smaller than 23 nm in engine exhaust. This paper describes investigation into a measurement method for ultrafine PNCs with thresholds of below 23 nm and evaluation of the VPR performance for the particles in this size range. The detection efficiency of an ultrafine PNC was verified by following the ECE regulation procedure.