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Research of Aviation PM Technologies, mOdelling and Regulation

Periodic Reporting for period 2 - RAPTOR (Research of Aviation PM Technologies, mOdelling and Regulation)

Reporting period: 2020-11-01 to 2022-04-30

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 regarding measurement, modelling and health impacts of aircraft engine PM. Identified uncertainties, gaps and interdependencies with a roadmap (aligned with other EC regulations 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.
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.
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. With the 6 months extension WP3 synthesised the WP4 outputs aiming to reduce uncertainties associated with measurements undertaken for engine certification measurements, including calibration uncertainties for regulatory purposes. These project outputs will aid the regulators in the maintenance, and updating where relevant, of the ICAO-CAEP Annex 16 Volume II and ETM Volume II guidance: Standards and Recommended Practices (Annex 16 Vol II, Part III, Chapter 4 and associated Appendices). The outcomes of RAPTOR will continue to be disseminated to ICAO-CAEP_WG3 and SAE E31 in the early months of the CAEP/13 cycle starting in March 2022.
Main gateway for accessing information and data associated with the RAPTOR program is the project website and ZENODO folders.

WP4, PM measurement was undertaken with three principal aims: understand uncertainty in current CAEP10/11 nvPM regulatory practices (D4.1); investigate the requirement of potential corrections to be considered towards reduced uncertainty during CAEP/12 (D4.2); Assess likely benefits future technologies and further regulation will offer in terms of reducing the impact of nvPM beyond CAEP/12. Limited appraisal of existing data from currently unregulated engines has been undertaken by ZHAW with this data being combined into the dataset. Aero-engine relevant RQL (rich-burn Quick-quench Lean-burn) combustor rig testing was performed at Cardiff University’s Gas Turbine Research Centre (GTRC) in December 2020 / February 2021 (M4.1 RQL Combustor Rig Test 1) and December 2021 (M4.3 RQL Combustor Rig Test 2).

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.

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.
Comparisons of the two compliant nvPM reference systems, during the aforementioned combustor tests, allowed parallel measurement of nvPM number, mass, and size distributions across a range of nvPM concentrations representative of modern aircraft turbine engines affording an assessment of both measurement uncertainty and impact of sampling system loss. Similarly, prescribed gaseous measurements (CO2, CO, NOx, UHC and SO2) were also undertaken.
The second test campaign, performed after a 12-month period permitted an assessment of system drift across the CAEP/11 specified calibration schedule.

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 allowed for comparing e.g. different fuel types for 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.