Feasibility study on the extension of the Real Driving Emissions (RDE) procedure to Particle Number (PN) : chassis dynamometer evaluation of portable emission measurement systems (PEMS) to measure particle number (PN) concentration: phase II

This report presents the results of Phase II evaluation of Particle Number (PN) Portable Measurement Systems (PEMS). 8 PN-PEMS were compared with legislation compliant PN systems connected to the tailpipe and the dilution tunnel (CVS). In total 7 Gasoline Direct Injection (GDI), 3 Port Fuel Injection (PFI), 2 Diesel Particulate Filter (DPF) equipped vehicle, 1moped and 3 motorcycles were tested with >130 test cycles. The results confirmed the findings of Phase I: Diffusion Charging (DC) based systems are a feasible option to measure PN and thermal pre-treatment is necessary to avoid volatile artefacts. At least two of the DC based PN-PEMS showed good agreement with the reference PMP system (#1, #3). A third one (#4) also had very good behaviour, but higher scatter. The best performing PN-PEMS had differences from the reference instrument at the tailpipe within -25% and +30% with a scatter of 20%.. The differences from the reference system at the dilution tunnel were within -35% and +50% (scatter 25%) (including all technologies tested); slightly higher due to the particle transformation processes that take place between the tailpipe and the dilution tunnel, exhaust flow accuracy and time alignment. It was also shown that a well calibrated PN-PEMS can cover a wide range of engine technologies with similar differences to the reference system. Based on the experimental data new PN-PEMS efficiencies were recommended for the technical requirements. The CPC based PN-PEMS had issues (prototypes). However, one CPC based PN-PEMS, which arrived late in the program, had behaviour equivalent to the reference systems and better real time comparability with the reference systems compared to the DC based systems. Further evaluation of the system after the campaign with another 10 vehicles confirmed these findings.