Enhancing airworthiness compliance of measurement system for aircraft non-volatile particulate matter emissions and its suitability to sustainable aviation fuel application

The non-volatile particulate matter (nvPM) emitted by aircraft engines poses significant environmental and health challenges, prompting strict international airworthiness standards. However, previous studies have not sufficiently quantified system-level measurement errors, often directly applying commercial instruments designed for conventional aviation fuel (CAF) to Sustainable Aviation Fuels (SAFs). Given that SAF particles exhibit distinct characteristics, including smaller sizes, more concentrated distributions, and unique morphologies, the applicability of existing nvPM measurement systems requires rigorous evaluation. This study comprehensively evaluates the error sources across the dilution, transport, and measurement stages of the measurement chain and proposes compliance enhancement methods, including background pollution purification, instrument calibration, and a particle size distribution (PSD)-based loss correction model. These strategies reduced the uncertainty of the DF1 dilution factor by 73.8% and the relative error of the Condensation Particle Counter (CPC) to 2.124%. Additionally, a PSD-based fitting correction was developed to address penetration losses, achieving a correlation coefficient (R²) exceeding 0.95. Experimental validation using RP-3 and HEFA-SAF demonstrated that these methods effectively improved measurement repeatability and accuracy, reducing the Coefficient of Variation (CV) of the Emission Index (EI) by over 50% and the measurement error by 24%. Notably, the study confirms that SAF exhibits significantly different microscopic characteristics compared to traditional fuel, showing a reduction in peak particle size by approximately 50%, a decrease in number concentration by one order of magnitude, and a more uniform size distribution indicated by reduced Geometric Mean Diameter (GMD) and Geometric Standard Deviation (GSD). However, under high thrust conditions, the higher proportion of ultrafine particles in SAF emissions increases sensitivity to transport losses, highlighting the necessity of expanding the CPC detection limit in future standards and adopting a unified loss correction model based on full particle size spectra. This work provides a validated framework for improving the accuracy of nvPM measurements and supports the integration of PSD into airworthiness certification.