Investigation on the particle loss and applicability of aviation nvPM measurement methodology for wide particle size ranges

The precise measurement of non-volatile Particulate Matter (nvPM) is outlined in aviation engine emissions regulations by the International Civil Aviation Organization (ICAO). However, assessing particle losses in the sampling and transfer unit presents challenges, raising concerns about the system's reliability. Moreover, nvPM emissions from small and medium aircraft engines, with thrust not exceeding 26.7 kN, vary widely in size, adding complexity to the measurement process. To provide a comprehensive analysis of particle losses in the sampling and transfer subsystems, this study established a test bench equipped with a nanoparticle generator. The generator simulates nvPM emissions from medium and small aircraft engines and can consistently produce nvPMs with a wide range of concentrations (10³-10⁷/cm³) and size distributions (20–160 nm). Thermophoretic loss verification experiments were conducted within the sampling pipeline under significant temperature differences, investigating the effects of particle size, temperature gradient, and airflow rate on thermophoretic particle losses. The experimental results demonstrated good agreement with the predictions of the model proposed by United Technologies Research Centre (UTRC). After correcting for temperature, the experimental data showed a maximum disparity of 2% under typical engine exhaust conditions, validating the predictability of the thermophoretic loss model for various engine types. Furthermore, verification experiments for particle diffusion and bending losses were performed. Comparative analysis with the UTRC model revealed nvPM inertial deposition under laminar flow conditions with low Reynolds numbers (Re). As the Re increased, the measured data more closely aligned with the simulations. Bending losses due to secondary flow patterns ranged from 1% to 10%, depending on particle size and flow rate. This finding supports the applicability of aviation nvPM measurement methods across a wide particle size range. This research provides theoretical support for future nvPM measurements on various aircraft engines, laying the groundwork for improved accuracy and reliability in emissions monitoring.