Four laboratories, Institut Francais du Petrole (IFP), PSA Peugeot-Citroen, Renault, and Union Technique de l'Automobile, du Motocycle et du Cycle (UTAC), have conducted an interlaboratory test to evaluate the performances of the condensation particle counter (CPC). The technical program was based on tests carried out on four passenger cars, one gasoline and three diesel ones, tested on the New European Driving Cycle (NEDC). The regulated pollutants are also measured, as indicators of test repeatability and good working conditions. The 1.96RSD reproducibility values of the total particle number determined by CPC on NEDC are 87, 58, 41, and 220%, respectively, for the Euro4 gasoline, Euro3 diesel, Euro4 diesel, and Euro3 diesel plus DPF (diesel particulate filter) vehicles. The CPC repeatability and reproducibility are poorest at lower particle numbers. The CPC performances, in terms of reproducibility, are comparable but generally not much better than the reproducibility of particulate matter emissions determined by the gravimetric method.

The electrical low-pressure impactor (ELPI) is employed to measure the particle number and size distribution of the exhaust gas of internal combustion engines. If appropriate values of particle density are available, the emitted particle mass may be estimated with this method. For this work, three Euro3 passenger cars (one gasoline car operating under stoichiometric conditions, one diesel car, and one diesel car equipped with a diesel particulate filter, DPF) were tested on the New European Driving Cycle. The exhaust particles were measured using the current European regulations (gravimetrie method) and estimated from the ELPI particle number and size distribution. Different particle density values were used to estimate the particle mass using all ELPI stages or only some of them. The results show that the particle mass estimated with ELPI is quite well correlated with the mass collected on filters in the case of a Euro3 diesel passenger car without a diesel particulate filter; however, this method fails to estimate the particle mass emitted from gasoline or DPF-equipped diesel passenger cars.

The Particulate Measurement Programme (PMP) works on the development of an improved method for the exhaust particulate matter (PM) measurement, which can include, if feasible and necessary, the measurement of particle number. The French PMP subgroup, composed of IFP, PSA Peugeot-Citroen, Renault, and UTAC, has defined a measurement protocol based on electrical low-pressure impactor (ELPI) and conducted an interlaboratory test to evaluate its performances. The technical program was based on tests carried out on three Euro3 passenger cars (one gasoline operating under stoichiometric conditions, one Diesel, and one Diesel equipped with a diesel particulate filter (DPF)) that were tested on the New European Driving Cycle (NEDC). The regulated pollutants are also measured, as indicators of test repeatability and good working conditions. The interlaboratory reproducibility value of the tunnel background tests is quite high (337%) due to low particle numbers. The repeatability values increase at low particle numbers independently of the vehicle used. On the NEDC, the reproducibility of total particle number is 59, 47, and 131% for the gasoline, Diesel, and DPF-equipped Diesel vehicles, respectively (compare to 67, 29, and 164% for PM collected on filters). These results show that the protocol used in this study allows a reliable measurement of exhaust particle number in the case of vehicles emitting at least two orders of magnitude more than the tunnel background. In the other cases, the measurement variability is too high, especially for regulatory purposes, without taking into account other metrological aspects, such as calibration.

INTER-LABORATORY TEST OF EXHAUST PARTICLE NUMBER MEASUREMENT USING CPC AND ELPI E. Zervas, P. Dorlhène, J.C. Momique, R. Monier, L. Forti, M. Pasquereau, H. Ing, B. Lopez4 Renault, PSA Peugeot Citroën, IFP, UTAC ABSTRACT The French Particulate Measurement Programme (PMP) subgroup, composed by IFP, PSA Peugeot-Citroën, Renault and UTAC, has conducted an inter-laboratory test to evaluate the performances of CPC (Condensation Particle Counter). The technical program was based on tests carried out on four passenger cars, tested on the New European Driving Cycle (NEDC). Electrical Low Pressure Impactor (ELPI) is also used to determine the total particle number and the particle distribution. The regulated pollutants are also measured, as indicators of test repeatability and good working conditions. INTRODUCTION Currently, there are many methods for the particle number and/or size determination. The most common used in the case of vehicle exhaust gas are the Electrical Low Pressure Impactor (ELPI), the Scanning Mobility Particle Sizer (SMPS) and Particle Counters, but many others are also presented in literature. SMPS has a very good particle size resolution. However; it has an insufficient resolution time (some minutes), and thus, it cannot be used for transient particle measurement on the NEDC. Last year, another inter-laboratory exercise was conducted from the same group in order to determine the performances of ELPI. Continuing this work, the current article presents the evaluation of CPC performances. EXPERIMENTAL SECTION Four passenger cars were used in this study: a Euro4 gasoline PC operating under stoichiometric conditions (vehicle 1), a Euro3 Diesel PC (vehicle 2), a Euro4 Diesel PC (vehicle 3) and a Diesel PC equipped with DPF (vehicle 4). Fuels with less than 10 ppm of sulphur were used for this study. The same lubricant (<0.4% of sulphur), was used for all four vehicles. For each vehicle, three tests were performed on the New European Driving Cycle (cold start), and regulated pollutants and CO2 emissions were measured according to current European regulations. Particle number was measured using a TSI 3022A CPC. A DEKATI ELPI, covering particle cut size from 8 nm to 10 μm, was also used. Two additional DEKATI diluters were used in series to dilute the sample gas. The first diluter was put in front of ELPI (dilution 10 times, heated at 120°C with hot nitrogen or air). The second one was put in front of CPC (to achieve total dilution 100 times, not heated). Tunnel backgrounds (blanks) were recorded during 20 minutes before and after each test. These values were not subtracted from the particle number of vehicles measurements. The particle numbers of the tunnel background tests are expressed in 1/Km using the same CVS volume and distance as a NEDC test. The intra-laboratory variability (ILV) is expressed as the relative standard deviation (RSD) of the measured values. The repeatability and reproducibility between the four laboratories are calculated following the ISO 5725 standards. In this work, the intra-laboratory variability, reproducibility and repeatability is expressed as 1.96*RSD (confidence interval of 95%). RESULTS AND DISCUSSION Emissions of regulated pollutants and CO2 Figure 1 of the poster shows the emission of regulated pollutants and CO2 of the four vehicles. The emissions of CO, HC, NOx and PM are within the regulatory limits. The 1.96*RSD repeatability values are within 3-11%, 9-22%, 2-34%, 7-103% and 1-3% for the CO, HC, NOx, PM and CO2 respectively and the corresponding reproducibility values are within 11-64%, 19-97%, 1335%, 19-200% and 1-3% respectively. The gasoline vehicle and the DPF equipped Diesel PC have high RSD values of PM emissions due to their very low levels, which are close to the blanks. Another reason for the higher RSD values of the vehicle 4 is that only two laboratories performed these tests. Particle number of the tunnel background tests The particle number of the tunnel backgrounds is very low: from 7x10 to 2x10 1/Km

Within the framework of atmospheric aerosol study, evaluation of the contribution of the particle source to global atmospheric pollution is a challenge that requires an improvement in the knowledge of particulate matter. As a part of this knowledge improvement, this study has been focused on particles emitted from diesel vehicles. Two light-duty diesel vehicles were studied for particulate matter size distribution and associated polycyclic aromatic hydrocarbon (PAH) content. A diffusional and inertial spectrometer was used, allowing particles from 7.5 nm to 15 μm to be collected and analysed. Teflon-coated glass fibre filters were employed as collector substrates, and weighed prior to and after sampling. Each of them was extracted with methylene chloride in an accelerated solvent extractor, cleaned on a silica gel micro-column and analysed for PAH by gas chromatography/mass spectrometry using internal standards for quantitation. Both analytical and sampling methods were validated. The highest particle mass was found to be emitted at 0.2 μm for the direct injection engine and 0.07 μm for the indirect injection engine. PAHs were found to be essentially distributed on particles in the accumulation mode, at about 0.2 μm, and high molecular weight PAH distributions were found to be bimodal or trimodal, depending on the engine injection.