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Understanding and measuring SUb-23 nm particle emissions from direct injection engines including REAL driving conditions

Periodic Reporting for period 2 - SUREAL-23 (Understanding and measuring SUb-23 nm particle emissions from direct injection engines including REAL driving conditions)

Reporting period: 2018-04-01 to 2019-12-31

A large proportion of the total number of particles emitted from direct injection engines are below 23 nm, and the EU aims to regulate those emissions and impose limits for new light-duty vehicles. Before SUREAL-23, accounting for sub-23 nm particles was not a straightforward choice due to the absence of accurate quantification methods, especially under real driving conditions. The project aimed to increase the knowledge regarding the nature of sub-23 nm particles from different engine/fuel combinations under various operating conditions. It also sought to overcome the relevant barriers by introducing novel measurement technology for concentration, size and composition measurements. In parallel, state of the art aerosol measurement techniques were advanced for better compatibility with sub-23 nm exhaust particles as well as onboard use. The developed instrumentation was used to assess sub-23 nm particle emissions from both Diesel and GDI vehicles accounting for effects of the fuel, lubricants, after-treatment and driving conditions for existing and near-future vehicle configurations. The most suitable concepts for onboard use have been evaluated accordingly. The project provided measurement technologies that will complement and extend established particle measurement protocols, sustaining the extensive investments that have already been made by industry and regulation authorities. It delivered a systematic characterisation of sub-23 nm particles to facilitate future particle emission regulations as well as to assess any potential trade-off between advances in ICE technology towards increased efficiency and emissions. The consortium consisted of European and US organisations, which are leaders in the field of aerosol and particle technology.
The developments concerned novel measurement instrumentation, the sampling methodologies, the knowledge on the nature of sub-23 nm particle emissions and the effect of engine/fuel technologies on particle emissions.
The target of the project was to develop measurement technologies, capable of accounting for sub-23 nm particles regarding number concentration, size and composition of particles. The Induced Current Aerosol Detector (ICAD), developed in SUREAL-23 is based on the fact that the conductivity of an aerosol after unipolar charging is approximately proportional to particle number concentration. ICAD provides particle number concentration, including sub-23 nm particles (down to 10 nm), in real-time and is capable for onboard measurements with high accuracy, repeatability and durability, comparable to the most advanced state-of-the-art systems. Also, the instrument requires minimal or no dilution system (i.e. no VPR) since it can measure hot samples (up to 180oC). The minimum dilution requirements, together with the minimal space and power requirements, making it ideal for PEMS applications. The Advanced Halfmini Differential Mobility Analyzer (HM-DMA), a super-critical DMA also developed in SUREAL-23, provides size-specific measurements. It demonstrated unprecedented resolution and extremely fast response. Even more importantly, the instrument is also capable of hot measurements calling for minimal sampling requirements without the losses and artefacts originating from the complexity of those systems. The losses and artefacts dominate the 10-23 nm particle size range, and therefore the above feature is of utmost importance. In the frame of SUREAL-23 project requirements, a variable wavelength UV photoelectric charger (UV-PEC) setup was designed and constructed for compositional studies of sub-23 nm particulate emissions. The instrument is able to reveal the Poly-Aromatic Hydrocarbons (PAHs) content on the particles' surface. PAHs are the key factors associating particle emissions with health risk. The device is also capable of real-time measurements and therefore.

SUREAL-23 extensively studied the nature of sub-23 nm particles. The effect of particular conditions on the sub-23 particle number concentration and the volatile content has been examined. The advancing of the particle sampling and treatment systems took place also within SUREAL-23 with the construction of a Catalytic Stripper (CS) for volatile particle removal.

An extensive test matrix was performed in engine dynos, chassis dynos and on-road (PEMS). It enabled to form a report documenting the project's recommendations in the light of coming regulations.

The project's results have been communicated through various dissemination and communication activities. SUREAL-23 managed to capitalise its research findings and reach a wide range of stakeholders including the public, scientists, policymakers and industry (9 papers to peer-reviewed journals, 31 participations in conferences and workshops, organisation of two very successful workshops, personnel training and links to the other relevant projects with joint testing campaigns).
The progress achieved notable progress beyond state-of-the-art. SUREAL-23 delivered instrumentation for accurate and reliable particle number size and composition measurements with exceptional characteristics such as the minimal sampling requirements (no need for complicated sampling and dilution system) and the downsizing of space and power requirements. These characteristics bring significant advances compared to current laboratory and PEMS.
The SUREAL-23 approach on the sampling and treatment of particles also brought significant breakthroughs. Hot sampling enables the exclusion of many parts of the current dilution systems minimising the particle losses and the creation of artefacts. Οn the other hand, the Catalytic Stripper developed within the project brings significant innovation compared to the current volatile particle removal technology.
The extensive test matrix accomplished during the project offered a significant amount of new knowledge for the nature of sub-23 nm particles. Also, many current and upcoming technologies have been examined, and new data on their particle emissions were analysed and published. This knowledge helped to formulate specific recommendations for the correct measurement of sub-23 nm particles and the regulation of those. SUREAL-23 demonstrated that sub-23 nm particles should be taken into account for most of the vehicles. Inclusion of sub-23 nm particles will enforce particle filters and clean-up existing combustion-based vehicles.
The project is expected to improve European innovation capacity. Since it helped to take into account and finally regulate sub-23 nm particles, it will also help to increase confidence in the ICE-powered vehicles. Avoiding to account for a part of the size spectra of particles, up to now, is decreasing confidence regarding the real health and environmental impact of the ICE vehicles. Improving the confidence of the measurements will enhance the environmental profile of the relative vehicles leading to significant advantages for the European industry.
Finally, the project spread light in the real nanoparticle emissions from contemporary and future engines. It is expected that will impact future regulations towards more efficient limits and measurement methods. The developed instrumentation will make vehicle exhaust testing simple and less costly, facilitating a wide adoption of concepts such as In-Serve-Conformity. The latter will, of course, have a positive impact on citizen's health and the city environment.