Particle Measurement Programme (PMP) Light-Duty Inter-Laboratory Exercise: Repeatability and Reproducibility of the Particle Number Method

Abstract

A Euro 4 Light-Duty Diesel vehicle equipped with a diesel particulate filter (DPF) was circulated to 9 labs where repetitions of the current regulatory New European Drive Cycle (NEDC) were conducted. Regulated gaseous and improved (with cyclone, filter temperature 47 ± 5• C, constant filter face velocity, high precision balance at all labs) particulate mass (PM) measurements were also conducted. A reference particle number (PN) measurement system measuring non-volatile particles was circulated along with the test vehicle. Labs also tested their own PN systems built to comply with the reference system's performance specifications. The mean PN emissions level of the vehicle was below 1 × 10 11 particles/km. The intra-lab variability (repeatability) was ∼40% and the inter-lab variation was ∼25%. The study showed that the new PN method had similar variability to other gaseous pollutants such as carbon monoxide and hydrocarbons and better than the PM (intra-lab variability ∼55% and inter-lab ∼35%). Even with the improved PM method the emissions of the vehicle were similar to the background level (∼0.4 mg/km) and the method was subject to volatile artifact. The PN method showed greater sensitivity than the PM method as it could distinguish the DPF fill state or different preconditioning states of the vehicle. However, the PN emission level of the vehicle estimated by the reference system were on average 15% higher than any given lab's own system, indicating that the procedures and calibration designed for the standardization of performance should be precisely defined and followed. This work has been conducted in the framework of the PMP project (run under the auspices of the UNECE-GRPE). The authors would like to thank all the laboratories and companies that participated. In addition, Matter Engineering AG for providing the dilution system of the reference system, TSI Incorporated for providing the particle number counter of the reference system, and Dekati Ltd and Horiba for providing particle number systems at the labs that did not have their own. AECC receive thanks for providing the reference vehicle, Concawe for providing the fuel and the lubricant for the reference vehicle and AEA Technology Environment for the calibrations of the reference system. The authors would also like to thank Dr. Nikolaos Stilianakis for his insights on the statistical issues.Address correspondence to Jon Andersson, Ricardo UK, Chemistry Department, Shoreham Technical Centre, BN43 5FG, Shoreham-bySea, U.K. E-mail: Jon.Andersson@ricardo.com INTRODUCTIONThe established method to measure particle emissions for type approval tests is gravimetric analysis of filter samples, taken from a full exhaust flow dilution tunnel. However, for low-emission vehicles, which are already present in the market, concerns have been raised about the suitability of the method. For example Chase et al. (2004) showed that a major part of the collected mass consists of volatiles (volatile artifact). Tests at various laboratories have shown high variability for th...

Evaluation of the European PMP Methodologies during On-Road and Chassis Dynamometer Testing for DPF Equipped Heavy-Duty Diesel Vehicles

“…The 3790 COV for the UDDS improved to 22% with its one outlier point removed. The 3790 COV data with the outlier removed is in the same range of 24-59% reported for the intra-lab variance for the ILCE LD round robin (Giechaskiel et al 2008). The COVs of the lower cut point 3025As were all greater than that of the PM mass for the laboratory testing and ranged from 110 to 270%.…”

“…The European Community has launched an extensive multination research initiative under the auspices of the United Nation's Economic Commissions for Europe-Group of Experts on Pollution and Energy (UN-ECE-GRPE) to investigate a new PM regulation method (Andersson et al 2007a,b;Giechaskiel et al 2008;Bosteels et al 2007). The methodology developed under this program is the measurement of solid particle number above a particle size of 23 nanometers (nm) at 50% counting efficiency (D50).…”

Alternatives to the Gravimetric Method for Quantification of Diesel Particulate Matter near the Lower Level of Detection

“…PMP studies have shown that when adopting these limits, particle number concentration measurements are repeatable to approximately 20 -30%, but can be as low as 5% when the engine-out emissions are very stable, such as when the engine is not equipped with a filtration device that undergoes periods of regeneration that produce fluctuating particle concentrations. 75 Particle number concentrations are very accurately measured with CPCs and their measurement is NIST traceable. However, issues remain and the suggestions below are given to ensure the validity of measurements made on diesel exhaust aerosols.…”

The Potential of a Partial-Flow Constant Dilution Ratio Sampling System as a Candidate for Vehicle Exhaust Aerosol Measurements Leonidas Ntziachristos

“…However, it should be recognized that PMP was not designed to provide input to health studies but to develop a robust protocol leading to sensitive PM measurements with limited variability. 14 Thus, this would enable type-approval of vehicles and engines emitting very low PM mass concentrations, such as diesel vehicles equipped with particle filters (diesel particulate filters [DPFs]). Obviously, the limitations of this approach to provide informative input to health studies are well recognized.…”