The Friction Coefficient of Fractal Aggregates in the Continuum and Transition Regimes

A methodology is introduced for friction-coefficient calculations of fractal-like aggregates that relates the friction coefficient to a solution of the diffusion equation. Synthetic fractal aggregates were created with a cluster-cluster aggregation algorithm. Their fiction coefficients were obtained from gas molecule-aggregate collision rates that were calculated with the COMSOL Multiphysics software. Results were compared and validated with literature values. The effect of aggregate structure on dynamical properties of the aggregate, in particular mobility, was also studied. Both the fractal dimension and the fractal prefactor are required to characterize fully an aggregate.JRC.F.8-Sustainable Transpor

Real Driving Emissions testing: A game-changer for NOx to promote cleaner vehicles in the EU

The gap between the goal set by the regulation (i.e. the “limits”) and the real vehicle emissions on road was an issue, regarding in particular the excess of nitrogen oxides on diesel vehicles. The isue was highlighted by JRC tests from 2012 and came to the attention of the public during the “diesel gate” in 2015. Investigations from the European Parliament revealed that the situation was caused by a combination of weaknesses in the vehicle emissions testing procedures and the enforcement system. Prior to the diesel gate, the European Commission had already launched scientific studies and worked on more stringent testing procedures for emissions since 2007 based on testing under real driving conditions using portable equipment: the Real Driving Emissions (RDE). Euro 6 vehicles type approved applying RDE testing procedure emit substantially less NOx emissions compared to vehicles type approved before the introduction of this new testing procedure.JRC.C.4 - Sustainable, Smart and Safe Mobilit

Manipulating vehicle emissions: state of play after Dieselgate

In the 2010s, it was found that some vehicle manufacturers were using illegal defeat devices, meaning that measurements of vehicle emissions made under regulated laboratory testing conditions were inaccurate. The issue came to the attention of the public during the Dieselgate scandal in 2015. An investigation by the European Parliament revealed that the situation was caused by a combination of shortcomings in emissions testing procedures and failure to enforce the relevant laws. With the aim of ending the use of defeat devices, the European Commission, as a first step, proposed the introduction of the real driving emissions test at type approval. Since 2016, vehicle manufacturers have also been obliged to declare any deactivation/modulation of the emissions control system, referred to as an auxiliary emissions strategy, that may take place outside the regulated conditions (driving conditions, temperature, altitude) of the real driving emissions test. The Commission and the Joint Research Centre, as part of their market surveillance duties, have been closely monitoring the enforcement of these new rules adopted in the aftermath of Dieselgate to limit the risk of defeat devices being used. No evidence of the use of a defeat device has been found since 2020.JRC.C.4 - Sustainable, Smart and Safe Mobilit

European market surveillance of motor vehicles

This report presents the results for the work conducted by the JRC as European Commission contribution to the market surveillance and regards emissions from motor vehicles in 2022. Primarily targeted towards the bodies acting in the EU market surveillance, it presents emissions test results and compliance findings. This document also discusses lessons learned during the application of testing procedures, with a view to share best practices with the participating authorities and potentially, to draw the path towards future policy updates. The document is structured in three main chapters: the requirements set by Regulations and methodologies for their verification (Part A), the test results and compliance outcome of the activities conducted by the Commission (Part B) and an overview of the main findings (Part C). Part A focuses on the requirements to be fulfilled by the vehicles and provides the main elements, further details being available in the regulatory texts. For some requirements, the verification cannot be made using type-approval procedures. Ad-hoc procedures are proposed and are likely to be revised making use of the experience gained. Part B presents the emissions test results and compliance findings for the individual vehicles analysed by the JRC during the year 2022. Part C is a summary of the findings and a tentative to draw recommendations from the lessons learned, with a view to identifying the most critical items and to improving the efficiency of the whole market surveillance testing process.JRC.C.4 - Sustainable, Smart and Safe Mobilit

European market surveillance of motor vehicles

This report presents the results for the work conducted by the JRC as European Commission contribution to the first year of market surveillance and regarding emissions from motor vehicles. The document is structured in three main chapters: the requirements and methodologies for their verification (Part A), the test results and compliance outcome for the activities conducted by the Commission (Part B) and an overview of the main findings (Part C). Part A focuses on the requirements to be fulfilled by the vehicles and provides the main elements, further details being available in the regulatory texts. For some requirements, the verification cannot be made using the type approval procedure (e.g. durability, OBD). In such a case, ad-hoc procedures are proposed and are likely to be revised on a yearly basis making use of the experience gained. Part B presents the emissions test results and compliance findings for the individual vehicles analysed by the JRC during the last year. Part C is a summary of the findings and a tentative to draw recommendations from the lessons learnt, with a view to identifying the most critical items (e.g. which requirements have the highest risk not to be fulfilled) and to improving the efficiency of the whole process.JRC.C.4 - Sustainable Transpor

Impact of Material on Response and Calibration of Particle Number Systems

In Europe and Asia, vehicle emissions regulations include a number limit for particles larger than 23 nm, which might be reduced to 10 nm in the future. A particle number system (LABS) consists of a volatile particle remover (VPR) and a particle number counter (PNC). However, it is not simple to derive the combined penetration (efficiency), because the parts are calibrated separately at different sizes and with different materials. On the other hand, portable emissions measurement systems (PEMS) for real-driving emissions (RDE) testing or counters for periodical technical inspection (PTI) of vehicle exhaust are calibrated as complete units with soot-like aerosol. The aim of this study is to estimate the efficiency of a LABS using different materials (soot, graphite, salt, silver, emery oil), typically used for the calibration of LABS, PEMS or PTI counters. The results show that appropriate selection of the calibration material is important in order to have representative of the reality efficiencies. The impact is very high for 23 nm systems, but less critical for 10 nm systems. The estimation of a mean size based on the ratio of 23 nm and 10 nm measurements and the correction of the losses in the sub-23 nm region are also discussed

Comparison of Particle Sizers and Counters with Soot-like, Salt, and Silver Particles

Vehicle emission regulations in Europe and many Asian countries include a particle number limit. The number concentration is measured, typically, with condensation particle counters (CPCs). For research purposes, the size distributions provide useful information. Scanning mobility particle sizers (SMPSs) accurately provide the size distribution but are not suitable for transient aerosol. Engine (fast) exhaust particle sizers (EEPSs) cover this gap, but with less accuracy. Fast size distribution instruments are commonly used in the research and development of engines. In the last few years, instrument algorithms have been improved, but studies assessing the improvements are limited, in particular in their lower size range, around 10–20 nm, and for soot-like aerosol. In this paper, we compared the three instruments using salt, silver, diffusion flame soot (CAST), and spark discharge graphite particles. Moreover, vehicle exhaust number concentration measurements with EEPSs over a seven-year period were presented. In terms of particle concentration, EEPS overestimated, on average, 25% compared to CPC, in agreement with previous studies. Its accuracy for mean particle size determination was better than 5 nm compared to SMPS. The agreement between the instruments was satisfactory but the uncertainty increased at low concentrations and larger particle sizes, showing that there is still room for further improvements. Experimental challenges, such as low concentration levels of modern vehicles, losses in the diluters, use of photometric mode by the CPCs, and the material impact, are also discussed

Impact of material on response and calibration of particle number systems

In Europe and Asia, vehicle emissions regulations include a number limit for particles larger than 23 nm, which might be reduced to 10 nm in the future. A particle number system (LABS) consists of a volatile particle remover (VPR) and a particle number counter (PNC). However, it is not simple to derive the combined penetration (efficiency), because the parts are calibrated separately at different sizes and with different materials. On the other hand, portable emissions measurement systems (PEMS) for real-driving emissions (RDE) testing or counters for periodical technical inspection (PTI) of vehicle exhaust are calibrated as complete units with soot-like aerosol. The aim of this study is to estimate the efficiency of a LABS using different materials (soot, graphite, salt, silver, emery oil), typically used for the calibration of LABS, PEMS or PTI counters. The results show that appropriate selection of the calibration material is important in order to have representative of the reality efficiencies. The impact is very high for 23 nm systems, but less critical for 10 nm systems. The estimation of a mean size based on the ratio of 23 nm and 10 nm measurements and the correction of the losses in the sub-23 nm region are also discussedJRC.C.4 - Sustainable Transpor