Diesel passenger car PM emissions: From Euro 1 to Euro 4 with particle filter Theodoros Tzamkiozis, Leonidas Ntziachristos * , Zissis Samaras Laboratory of Applied Thermodynamics, Aristotle University of Thessaloniki, P.O. Box 458, GR 54124, Thessaloniki, Greece article info Article history: Received 5 May 2009 Received in revised form 27 November 2009 Accepted 2 December 2009 Keywords: Particle number Exhaust emissions DPF Emission standard Particle density abstract This paper examines the impact of the emission control and fuel technology development on the emissions of gaseous and, in particular, PM pollutants from diesel passenger cars. Three cars in five configurations in total were measured, and covered the range from Euro 1 to Euro 4 standards. The emission control ranged from no aftertreatment in the Euro 1 case, an oxidation catalyst in Euro 2, two oxidation catalysts and exhaust gas recirculation in Euro 3 and Euro 4, while a catalyzed diesel particle filter (DPF) fitted in the Euro 4 car led to a Euro 4 þ DPF configuration. Both certification test and real- world driving cycles were employed. The results showed that CO and HC emissions were much lower than the emission standard over the hot-start real-world cycles. However, vehicle technologies from Euro 2 to Euro 4 exceeded the NOx and PM emission levels over at least one real-world cycle. The NOx emission level reached up to 3.6 times the certification level in case of the Euro 4 car. PM were up to 40% and 60% higher than certification level for the Euro 2 and Euro 3 cars, while the Euro 4 car emitted close or slightly below the certification level over the real-world driving cycles. PM mass reductions from Euro 1 to Euro 4 were associated with a relevant decrease in the total particle number, in particular over the certification test. This was not followed by a respective reduction in the solid particle number which remained rather constant between the four technologies at 0.86  10 14 km 1 (coefficient of variation 9%). As a result, the ratio of solid vs. total particle number ranged from w50% in Euro 1e 100% in Euro 4. A significant reduction of more than three orders of magnitude in solid particle number is achieved with the introduction of the DPF. However, the potential for nucleation mode formation at high speed from the DPF car is an issue that needs to be considered in the over all assessment of its environmental benefit. Finally, comparison of the mobility and aerodynamic diameters of airborne particles led to fractal dimensions dropping from 2.60 (Euro 1) to 2.51 (Euro 4), denoting a more loose structure with improving technology. Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The diesel engine has historically been the powertrain of choice for trucks, trains, ships and other heavy-duty applications world- wide, due to its advantageous characteristics over other concepts, namely efficiency, reliability and durability. More recently, and especially in Europe, diesel engines have also become widespread for passenger cars and light-duty trucks. Diesel car registrations increased from 13% of all car registrations in 1990e53% in 2007 (ACEA, 2009). The increasing penetration of diesel cars in the market forced regulations to introduce more stringent emission standards. Euro 1 standards were introduced in 1992 and then, gradually, Euro 2 in 1996, Euro 3 in 2000 and Euro 4 in 2005. Euro 5 is expected in 2010 which will require the use of a diesel particle filter (DPF) to reach the PM emission limit. The significant emission reductions over the years were achieved with a combination of engine design optimization, availability of refined fuels, and the use of exhaust aftertreatment devices. Diesel combustion is characterised by lean air-to-fuel ratios, which lead to very low total hydrocarbon (THC) and carbon monoxide (CO) emissions. On the other hand, the high combustion temperature is responsible for increased nitrogen oxides (NOx) production, while the diffusion combustion of fuel is responsible for elevated emissions of particulate matter (PM), compared to gasoline cars. Particular focus is given to NOx and PM emissions, because of their significant impact on both health and the envi- ronment (e.g. Dockery and Pope, 1994; Chapman, 2007). Regarding PM, a number of epidemiologic studies reviewed by the California Air Resources Board (ARB, 1998) confirm an association between ambient PM and adverse health outcomes, including mortality rates, respiratory related hospital admissions, asthma attacks, and aggravation of chronic diseases. Additionally, animal studies * Corresponding author. Tel.: þ302310996003; fax: þ302310996019. E-mail address: leon@auth.gr (L. Ntziachristos). Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv 1352-2310/$ e see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2009.12.003 Atmospheric Environment 44 (2010) 909e916