INTER-LABORATORY TEST OF EXHAUST PARTICLE NUMBER MEASUREMENT USING CPC AND ELPI

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