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Research of Aviation PM Technologies, mOdelling and Regulation

Periodic Reporting for period 1 - RAPTOR (Research of Aviation PM Technologies, mOdelling and Regulation)

Reporting period: 2019-11-01 to 2020-10-31

Scientists and regulators have an increasingly profound understanding of the complex nature of Particulate Matter (PM) in ambient air. Aircraft particulate emissions, as emissions of nvPM from other sources, are subject to regulation. Within the last ICAO-CAEP cycle, CAEP/11, a new standard for LTO nvPM mass and number for engine with rated thrust greater 26.7 kN was developed, the first standard of its kind. In-production regulatory limit values for nvPM mass and number are set at a level to allow in production engines to pass and act as an anti-backsliding standard. However, there remains uncertainty in the methodology surrounding the effects of ambient conditions, fuel composition and sampling system calibration and loss corrections. Furthermore, the regulation does not address the effects on the global atmosphere by excluding volatile PM, cruise conditions and the contribution of PM by smaller engines and engines rated on shaft speed. These factors, along with the potential impact of emerging technologies, need to be considered for a future European roadmap for improving current nvPM methodologies and future nvPM measurement technologies and regulation beyond the current cycle CAEP/12.

RAPTOR has brought together a consortium of interdisciplinary experts in the fields of measurement, modelling and health to provide a synergy of the current and future impacts of aircraft nvPM and to provide robust support to key stakeholders going beyond the current CAEP cycle. An overview of the perceived needs and roadmap (aligned with other EC regulations and guidelines) for action on aircraft engine PM regulation, measurement, modelling and future technology adoption. To provide a framework to assist EASA and the EU commission in future regulation, policy and guidelines.

RAPTOR contributes to the following areas related to aviation PM emissions: measurement uncertainties and regulation at engine exit plane (WP4); modelling transport, dispersion and transformation of engine emissions (WP5); and health impacts (WP6). WP3 aims to coordinate, communicate and provide a regulatory overview of these technical work packages.

The project expected outcome is:

Aim 1: Synergize current aircraft engine PM understanding and produce a roadmap for future advancements:
• Establish a coherent overview of the current state-of-the-art research efforts regarding measurement, modelling and health impacts of aircraft engine PM. Identified uncertainties, gaps and interdependencies will aid development of a roadmap (aligned with other EC regulations and guidelines) for action on aircraft engine PM regulation, measurement, modelling and future technology adoption.
• Provide a framework to assist EASA and the EU commission in future regulation, policy and guidelines.

Aim 2: Quantification and reduction of uncertainty in CAEP/11 nvPM emission standard:
• Use historic and combustor rig testing data to support improvement of current CAEP/11 standards, assessing potential correction methodologies towards accurate prediction of aircraft engine exit nvPM and subsequent airport LAQ modelling for consideration during CAEP/12 and beyond. (Using a small-scale combustor rig testing)
Aim 3: Improved understanding of the health impacts of aircraft engine nvPM:
• Determine a more nuanced understanding of the potential impact of ultrafine PM emitted from aircraft engines on health outcomes and provide contextual evidence and advice to the regulatory community in developing future EC guidance and standards.
WP3 has supported and worked alongside the technical WP to ensure high level engagement of the regulatory and policy making community and develop a roadmap to help narrow knowledge gaps. As RAPTOR outcomes are delivered appropriate communication and dissemination routes will be utilised to ensure the efficient and effective engagement with the end user community. The pace of WP3 is effectively dictated by the rhythms of the technical work packages – as these have been, to some extent, slowed by the impact of COVID-19.

As work in WP4 progresses, the outputs aim to reduce uncertainties associated with measurements undertaken for engine certification measurements, including calibration uncertainties. In line with the original schedule M4.2 has been completed by ONERA investigating the impact of sulphur and aromatics using a CAST burner. Limited appraisal of existing data from currently unregulated engines has been undertaken by ZAHW with this data being combined into the dataset

Under WP5, A literature survey has been undertaken regarding emissions and modelling of PM at the various scales (airport scale, national scale, continental scale and global scale) to identify the current state of knowledge as well as the gaps that still exist. The review and underpinning the citation management system (Zotero) data will continue to be added to during the project. First steps have been undertaken to improve and update in the framework of a test evaluation the national emission inventory of the Netherlands (CLEO) in view of aircraft-related PM emissions

Under WP6; Working towards a turbine emission database, first a literature survey on physicochemical characterization was conducted. A comprehensive search string was applied in Scopus and a library containing approximately 100 research papers was compiled and a literature database was created, which gives an overview on the sampling details such as engine type, used fuel, power settings and types of physicochemical analysis. From this library, 27 research papers contained extensive data on chemical analysis of turbine emissions, and these papers were subsequently examined for input for the turbine emissions database. It is important to note that only a select number of research papers were suitable for input, as only a select number of research papers contained numerical data.
RAPTOR partners have submitted information papers to both ICAO and SAE. To date 3 information papers and presentations have been made to regulatory stakeholders.

The emission database was created in Microsoft Excel, in which each engine type is represented by a dedicated tab. This allows for comparing e.g. different fuel types fir the same engine. Each tab shows information about: fuel type, engine power settings, PM/compounds analysed, concomitant emission indices and the corresponding references. A new emission database available on turbine engine emissions can be utilized in emission modelling and assessment of health effects. This emission database, along with (the limited) published toxicity data on turbine engine emissions, could allow for an assessment of critical factors that affect the hazard of the emission mixture.

RAPTOR has established links with several other European projects including AVIATOR , TUBE and FACTS and reached out to work alongside the US funded ASCENT programme.