Assessment of Condensation Particle Counter-Based Portable Solid Particle Number System for Applications with High Water Content in Exhaust

The Particle Number–Portable Emission Measurement System (PN-PEMS) came into force with Euro VI Phase E regulations starting January 1, 2022. However, positive ignition (PI) engines must comply from January 1, 2024. The delay was due to the unavailability of the PN-PEMS system that could withstand high concentrations of water typically present in the tailpipe (TP) of CNG vehicles, which was detrimental to the PN-PEMS systems. Thus, this study was designed to evaluate the condensation particle counter (CPC)-based PN-PEMS measurement capabilities that was upgraded to endure high concentration of water. The PN-PEMS measurement of solid particle number (SPN₂₃) greater than 23 nm was compared against the laboratory-grade PN systems in four phases. Each phase differs based upon the PN-PEMS and PN system location and measurements were made from three different CNG engines. In the first phase, systems measured the diluted exhaust through constant volume sampler (CVS) tunnel. Data generated from the 15 test cycles reported −13(±5)% error from the PN-PEMS system. In the second phase, PN-PEMS was relocated to the TP location and reported an error of 10(±26)%. In the third phase, measurements were made from the raw test cell where PN-PEMS measured from the TP and PN system extracted samples from the partial flow dilution system (PFDS). Data from 31 test cycles reported a −5(±9)% error. In the final phase, the PN system also measured alongside PN-PEMS from the TP and the correlation further improved, and subsequently the error was reduced to −3(±7)%. Overall, data from 96 test cycles showed that PN-PEMS measured within ±15% of the PN system, which concluded that the CPC-based PN-PEMS is suitable for measuring CNG engine exhaust and the performance is equivalent to the measurements from diesel engines. This data suggests that the SPN₂₃ measurements from TP could provide better understanding of the real-world measurements.