SAE AIR7382

This document, expanding upon AIR6037A, provides technical specifications and operational protocols for instruments commonly used to measure aircraft engine nonvolatile Particulate Matter (nvPM) Particle Size Distributions (PSDs). For each instrument type, its functionality, calibration, uncertainties, and known limitations are discussed to support the development of procedures that help ARP6320B nvPM system operators reliably determine PSDs. Practical setup considerations, such as sample conditioning and instrument positioning, are highlighted, together with guidelines for maintenance, data correction, and quality control to minimize measurement uncertainty. This SAE Aerospace Information Report (AIR) provides guidelines and multiple possible options for performing particle size measurements in ARP6320B nonvolatile Particulate Matter (nvPM) systems in parallel with nvPM mass and number measurements. It outlines several state-of-the-art methods for measuring aircraft engine exhaust nvPM Particle Size Distributions (PSDs) and discusses some of the uncertainties associated with different measurement techniques, calibration practices, and sampling location and conditioning. The goal of this information report is to advance the nvPM particle size measurement process for aircraft turbine engines. While aircraft engine PSDs provide useful engineering information for evaluating combustion technologies, their primary benefit may be in improving system loss correction. Accurate system loss correction is essential for estimating engine-exit concentrations, enabling comparisons across engine technologies, supporting environmental monitoring, and becoming increasingly important as modern engine technologies and sustainable aviation fuels produce smaller nvPM. Using a measured PSD can significantly reduce uncertainty in estimating size-dependent system loss correction factors (kSL_num and kSL_mass) compared to the current ARP6481A methodology. Based on the available data, the ARP6481A methodology can underestimate system loss correction factors by as much as 67% compared to methods using measured PSD due mostly to uncertainties inherent to the measured nvPM number and mass. In contrast, kSL_num and kSL_mass derived from measured PSD have been shown to exhibit a variability ≤10%, influenced by the method, particle size instrument type, or model used. AIR6504A describes methodologies for using measured PSD to calculate system loss correction factors and includes a calculation tool. This AIR also explores the applicability of using PSD measurements to derive nvPM number and mass emissions. A summary of currently available PSD measurement technologies and instrument-specific recommendations is provided in Section 10 and Table 1.