Citation

Alvarez M, Kreeger RE, Palacios J. Int. J. Impact Eng. 2019; 123: 70-76.

Copyright

(Copyright © 2019, Elsevier Publishing)

DOI

10.1016/j.ijimpeng.2018.09.008

PMID

unavailable

Abstract

Operations in ice crystals conditions are a threat to commercial aviation. The ingestion of ice crystals can affect different aircraft probes but can also affect jet engines. As fully frozen ice crystals enter an engine, partial melting occurs on the low-pressure compressor region of the engine, and ice accretion could occur on warm surfaces due to the presence of water coupled with the cooling capacity of the unfrozen portion found on the particles. Understanding the fundamental fracture dynamics that occur when partially melted ice crystals impact a surface is needed for model development and verification. To experimentally measure such fracture/splashing dynamics, a test rig was designed and fabricated to observe the impacts of partially melted ice particles. Ice particles ranging from 403 µm to 1028 µm were suspended on an ultrasonic levitator and were allowed to melt under natural convection. A fluorescence-based technique was used to quantify the water content of the melting ice particle in real time. A pneumatic launcher was automatically triggered at a requested water content to ice ratio, and a stainless steel impactor was launched at speeds ranging from 2.8 ms−1 to 65.5 ms−1. The impacts were recorded with a high-speed camera at 75,000 frames per second. The qualitative behavior of these impacts was observed, and an empirical model to determine the threshold velocity for an ice particle to fracture for varying water contents to ice ratios was proposed. From this empirical model, when the water content ratio was 79%, the impact velocity required to fracture a particle increased by 81% from the value obtained for fully frozen cases. Moreover, a new technique to measure the water content of a melting ice particle based on the diameter of the ice core observed post impact was conducted. The post-impact direct measurement technique was compared to the real-time fluorescence-based water content quantification technique to asses its accuracy and to understand partial melting quantification uncertainties.

Language: en

Keywords

Engine icing; Ice crystals; Icing; Mix-phased conditions; Water content quantification