Investigation in Calibration Procedures for Portable and Stationary Solid Particle Number Measurement Systems

The Particle Measurement Programme (PMP) established under the United Nations Economic Commission for Europe has developed the solid particle number (PN) measurement methodology, which has relatively higher sensitivity than the particulate matter measurement protocol. The first PN emission regulation was introduced in 2011. The stationary PN measurement system (PMP system) has been applied in the chassis and the engine test cells. In recent years, real driving emissions (RDE) measurement is attracting attention. Portable emissions measurement systems for PN measurement (PN-PEMS) which can be installed on vehicles during RDE testing are available now. The European RDE regulation requires validation of PN-PEMS by comparing emission measurement results with a stationary PMP system on a chassis dynamometer prior to the on-road emissions testing. Measurement differences between the PN-PEMS and the PMP system has to be within the tolerance defined by the regulation. Therefore, equivalency in measurement results of the PN-PEMS to the PMP system is required. However, a PN-PEMS does not generally have the same system configuration as a PMP system. In addition, a PN-PEMS has different calibration procedures from a PMP system. There is concern that such equipment differences cause measurement differences between a PN-PEMS and a PMP system under specific solid particle size distributions. In this study, size dependent particle number detection efficiencies of a PN-PEMS, which is equipped with a condensation particle counter as a particle number detector, and a PMP system have been evaluated. In addition, the calibration procedure of the PN-PEMS was applied to the stationary PMP system in order to observe the difference in performance caused by the procedure. Finally, PN emission measurement tests have been performed by utilizing the PMP system calibrated by the PN-PEMS procedure and the PN-PEMS. The influence to actual engine exhaust measurement by the difference in the calibration procedures is discussed.