Airborne Interferometric Cloud Particle Imager: Instrumentation and Applications to Icing Wind Tunnel

An instrument for characterizing icing cloud particles in wind tunnels is urgently needed to enhance the understanding of aircraft icing mechanisms. Measuring multiscale and multiphase icing cloud particles presents significant challenges, particularly under extreme environmental conditions. Interferometric particle imaging (IPI) has been established as an effective technique for analyzing multiphase cloud particles. In this work, an advanced instrument, Airborne Interferometric Cloud Particle Imager (AICPI), has been developed and validated by accurate calibration and a wide range of applications. AICPI’s optical-mechanical–electronic-thermal integrated design ensures reliable operation in icing wind tunnels. Validation experiments, conducted using a monodisperse droplet generator and a high-speed microscopic imaging system, confirmed that AICPI achieves a relative size measurement error of less than 5%. AICPI was deployed in one normal temperature wind tunnel and two industrial icing wind tunnels with test section dimensions ranging from $0.6\times 0.6$ m to $3.0\times 2.0$ m, wind speeds up to 50 m/s, and temperatures as low as $- 14~^{\circ }$ C. In practical applications, the AICPI measures particle sizes in the range of 10– $200~\mu $ m. Results from wind tunnel tests demonstrate the instrument’s feasibility for particle size measurement and phase discrimination in mixed-phase cloud fields.