Investigation of Equivalency between Laboratory-Grade and Portable Emissions Measurement Systems in Solid Particle Number Measurement Larger than 10 nm

The measurement protocol of solid particle number with the lower detection limit (D₅₀) at 10 nm (SPN₁₀) is planned to be implemented in European emission regulations by means of laboratory-grade measurement systems. Furthermore, SPN₁₀ measurement as the real driving emissions (RDE) regulations is under development by defining appropriate technical specifications for the portable emissions measurement system (PEMS). It is under discussion to implement SPN₁₀ limits as one of additional pollutants to the new European emissions regulations, so-called “Euro 7”. As the Consortium for ultra LOw Vehicle Emissions (CLOVE) has proposed, RDE testing by means of PEMS will be the primary means of emissions determination for certification purposes. Measurement equivalency between laboratory-grade emissions measurement systems and PEMS is still important due to the necessity of validation in laboratories before on-road testing by comparing determined emissions by both. The current draft technical requirements for SPN₁₀ measurement in laboratory and on-board allow certain difference in detection efficiencies, especially around the D₅₀ of 10 nm. However, good agreement in the efficiencies between the commercially available laboratory systems and PEMS was observed experimentally by using similar measurement principles based on condensation particle counters (CPCs). The results suggested that the difference in detection efficiencies for the applicable particle size range greater than 10 nm between the laboratory system and PEMS could be within ±10%. Moreover, it is found that the entire system detection efficiencies calibrated directly were equivalent to the calculated efficiencies by individual calibration coefficients of the volatile particle remover and the CPC defined by the regulations.