SOOTCERT: Measurement of soot particles with state-of-the-art methods as a basis for a new certification approach

Kurzfassung

The emission of particulate matter from aircraft engines, their potential impacts on Earth’s climate and human health, and state-of-the-art methods for measuring particulate matter in aircraft engine exhaust are high up on the agenda of research activities as well as of international bodies like ICAO, FAA, and EASA. There are parallel ongoing activities as part of the CAEP process, at the FAA framed into the PM roadmap, and recently within EASA and within the German Federal Ministry of Transport, Building and Urban Affairs (BMVBS), Aviation and Space Division. On the request of ICAO, the SAE E-31 Committee on Aircraft Exhaust Emissions Measurement has worked in the past years towards new measurement approaches for particulate matter from aircraft engines. A consensus has been achieved on the methods which are in principle available for this task. However, there is ongoing discussion on the appropriate measures for particle emissions with respect to aerosol-cloud interaction (climate impact) and adverse human health effects. An even more pressing issue are appropriate measurement approaches for volatile, thermally instable particles which so far are postponed from the approach chosen by the SAE E-31 committee because of unsolved technical questions, although these particles are considered relevant for human health aspects e.g., by US EPA. This report summarises the BMVBS funded activities for the development of a new particle matter emissions regulation for new aircraft engines. It incorporates recent activities of the authors in the framework of ICAO / CAEP and SAE E-31 committee work in order to align the selected approach with international ongoing activities. The conclusions concerning potential particle metrics and related limiting values are: 1. The non-volatile combustion particle fraction is correlated to engine technology. This fraction is stable because it does not depend on sample handling as long as particle coagulation and losses to the sample line walls are avoided. 2. The consideration of volatile particulate matter emissions suffers from the lack of knowledge of the contributing compounds. However, volatile particulate mass is predominantly linked to fuel sulphur and atmospheric conditions during plume dilution rather than to engine technology. 3. Potential precisely accessible particle properties are particle number and particle mass. Particle number, because the scientific debate on health effects of particulate matter focuses on insoluble nanometer-sized particles by number. Particle mass, because current air quality regulations focused on particle mass. 4. A limiting value will have to be related to the rated thrust, irrespective of the measured variable, i.e. mass and/or number, so that it is defined analogous to other already existing limiting values.