Assessment of In-Use Solid Particle Number Measurement Systems against Laboratory Systems

Euro VI regulations in Europe and its adaptors recently extended the regulation to include Particle Number (PN) for in-use conformity testing. However, the in-use PN Portable Emissions Measurement System (PEMS) is still evolving and has higher measurement uncertainty when compared against laboratory-grade PN systems. The PN systems for laboratory require a condensation particle counter (CPC). Thus, in this study, a CPC-based Horiba PN-PEMS was selected for performance evaluation against the laboratory-grade PN systems. This study was divided into four phases. The first two phases’ measurements were conducted from the Constant Volume Sampler (CVS) tunnel where the brake-specific particle number (BSPN) levels of 10^10-12 and 10¹³ (#/bhp-h) were measured from the engines equipped with diesel particulate filter (DPF) and without DPF, respectively. In comparison against PN systems, PN-PEMS, on average, reported 14% lower BSPN from 82 various tests for the BSPN levels of 10^10-11. In the case of engine-out (EO) BSPN levels (10¹³), PN-PEMS, on an average, reported 8% lower from 66 tests. The short-term repeatability and reproducibility of the solid particles measured by PN-PEMS were evaluated with the two non-DPF engines in the second phase of the study. Repeatability and reproducibility were below 3.5% and 15%, respectively. In the third phase, PN-PEMS measured from the raw location and PN system measured from the partial flow sampling system (PFSS). For 53 different tests of 10^10-11 BSPN levels, PN-PEMS, on average, reported 15% lower measurements. In the final phase, PN-PEMS performance was evaluated on the chassis dynamometer where it reported 10-20% higher than the PN system. A diffusion charger (DC) PN-PEMS utilized in the final phase, reported two to six times higher PN due to overestimation of urea solid particles whenever selective catalyst reduction (SCR) temperature was above 250°C. From more than 200 various test data for this overall study, on average, Horiba PN-PEMS reported a 12% lower BSPN than the laboratory-grade PN system.