Simultaneous measurements of morphology, size distribution and concentration of ice crystals in icing wind tunnel with HACPI

The simulation of ice crystal icing at high altitudes in the icing wind tunnel holds significant value for the study of icing on the aero-engine, pitot probe and other components of aircraft. Concurrently, the measurement of ice crystals in the icing wind tunnel is an aspect that warrants attention. This study introduces the Holographic Airborne for Cloud Particle Imager (HACPI) based on in-line holography, and conducts a series of experiments in the icing wind tunnel at AVIC Chengdu CAIC Electronics Co., LTD. The icing wind tunnel is equipped with an ice crystal generation system (ICGS) that operates on a grinding-based method. The morphology, size distribution and concentration of the ice crystals are simultaneously measured under airspeeds of Mach 0.55 and Mach 0.62 with HACPI, the results indicate that the morphology of ice crystals generated by the ICGS exhibits randomness. It is observed that with an increase in particle size, the irregularity also increases, and the maximum size of the ice crystals produced can approach 1000 µm. Under two typical test conditions, the MVD are 202.4 µm and 247.7 µm, respectively, while the MMD are 103.7 µm and 166.9 µm. In addition, the IWC are 4.47 g/m³ and 6.67 g/m³. A close relationship is observed between the particle size distribution and concentration of the ice crystals and the operating frequency of the ICGS components. Furthermore, this work demonstrates the significant potential of digital holography in measuring ice crystals in icing wind tunnels.