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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - SUREAL-23 (Understanding and measuring SUb-23 nm particle emissions from direct injection engines including REAL driving conditions)

Teaser

Summary

A large proportion of the total number of particles emitted from direct injection engines are below 23 nm and although the EU aims to regulate those emissions and impose limits for new light duty vehicles, this is not yet possible due to the absence of accurate quantification methods, especially under real driving conditions. The main reason for this is the absence of adequate knowledge regarding the nature of sub-23 nm particles from different engine/fuel combinations under different operating conditions. SUREAL-23 aims to overcome such barriers by introducing novel measurement technology for concentration/size/composition measurements (Figure 1). The recently established supercontinuum laser technology will be coupled to photoacoustic analysis and will also be employed for photoelectric ionization aerosol charging to achieve real-time, composition size-specific analysis of the particles. In parallel, state of the art aerosol measurement techniques - such as supercritical DMA and induced current based technique - will be advanced for better compatibility with sub-23 nm exhaust particles as well as on-board use. The developed instrumentation will assess sub-23 nm particle emissions from both Diesel and GDI vehicles accounting for effects of the fuel, lubricants, aftertreatment and driving conditions for existing and near-future vehicle configurations. The most suitable concepts will be developed for PN-PEMS applications and evaluated accordingly. The project will provide 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. The project will deliver systematic characterization 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 consists of European and US organisations, which are leaders in the field of aerosol and particle technology.

Work performed

The work performed since the beginning of the project concerns three WPs. In the WP1, the instrumentation and the testing platforms to be used throughout the projects, were defined. A state-of-the-art review of the current status of the available instrumentation was delivered.
WP2 concerned the novel instruments development. Significant breakthroughs have been realized. It is the first time that a DMA attained such resolution level for sub-23 nm particles and response times in exhaust applications. Another significant achievement concerns the ICAD instrument capable of measuring particle number concentration based on the charging principle. The instrument fulfilled the requirements for sub-23 nm particle measurements, it is very light and compact with small electrical power requirements, making it ideal for PEMS. Both instruments, HM-DMA and ICAD are capable of hot measurements calling for minimal sampling system and have been validated both in lab and engine exhaust.
The first prototype of the sizing-CPC, a unique instrument, capable of combining particle size with particle number concentration measurements has also been developed and currently validated in the lab. This instrument, starting from lower TRL than the previously mentioned, after successful completion of the necessary evaluation steps, it brings unique capability in the measurements, also for PEMS.
The particle composition instruments (photoacoustic and photoelectric based) also started from lower TRLs, but their hardware was also ready as planned. Both of them are validated in the lab with promising results, integrating the high power lasers.
Last but not least, preparatory activities for the GDI engine test campaign have already been performed: design of the test campaign, commissioning of the instrumentation and preliminary tests are efficiently completed.
WP3 concerned the study on the nature of sub-23 nm particles from gasoline and Diesel engines. The work is ongoing and we have examined the effect of particular conditions (different fuels, fuel additives, lubricants, ethanol content, etc.) on the sub-23 particle number concentration and volatile content. WP3 also concerns the investigations on the proper sampling and treatment system. The projectâ€™s plan consisted of two pathways. The first pathway was to eliminate a big part of the complicated PMP-like dilution system. SUREAL-23 succeeded in that as we managed to deliver two instruments capable of hot measurements, as already explained. The second pathway concerned the development of an advanced dilution system, consisting of the typical two-stage diluters and the Volatile Particle Remover (VPR). An advanced design was followed based on an innovative ejector-type dilution system and a Catalytic Stripper (CS) as a VPR. The system has already been tested in the lab and engine exhaust is showing minimal particle losses and artefacts for the sub-23 nm area and excellent volatile and sulphur removal efficiency.

Final results

The progress beyond state of the art already attained is according to the projectsâ€™ goal. It is the first time that hot measurements from engine exhaust, using HM-DMA and ICAD, are realized, call only for a simple hot dilution step which does not imply any particular losses or artefacts and can apply to different engine exhaust environments and handled by not specifically trained technical personnel. Even more importantly, the electrical power and weight requirements are being removed from PEMS together with any ambiguities regarding artefacts.
Moreover, in the effort for improving exhaust conditioning capability, a Catalytic Stripper was developed and validated and found to attain and/or surpass PMP requirements regarding volatiles removal and particle penetration efficiency while having a much higher sulfur storage capacity than the state-of-the-art. This outcome, also with the hot sample measurement capability, may impact on the relative importance that will be attributed to the catalytic stripper as part of new standards for exhaust conditioning configurations.
The effectiveness of the HM-DMA instrument in hot and fast size-scanning operation generates the potential for some unforeseen impact in the approach to portable particle emissions measurement, since it now seems more feasible than initially expected that near real-time size classification will be possible for exhaust particles in the 10 â€“ 30 nm size range (potentially down to 5 nm). PEMS testing activity planned in the SUREAL-23 project second term will aim to provide some confirmation of this possibility and its potential impact.
With respect to SUREAL-23 impacts for sub-23 nm emissions beyond the engine/vehicle types specifically described in the project scope â€“ a possibility foreseen in the initial proposal due to the wider applicability of the instrumentation developed in the project â€“ there seems to be a specific possibility emerging in the case of other than Diesel and Gasoline ICE such as the natural gas engines. Recently released measurements, indicate that natural gas engines â€“ not regulated for particle emissions â€“ may be capable of regulation-worthy particle emission levels, especially in the sub-23 nm region and with a strong dependence on engine operation mode and lubricant formulation.