This work presents the results of an experimental study of ice particle impacts on a flat plate made of glass. The experiment was conducted at the Ballistics Impact Laboratory of NASA Glenn Research Center in 2014 and is part of the NASA fundamental research efforts to study physics of ice particles impact on a surface, in order to improve understanding of ice crystal ingestion and ice accretion inside jet engines. The ice particles, which were nominally spherical ranging in initial diameter between 1 and 3.5 millimeters, were accelerated to velocities from 20 to 130 m/s using a pressure gun. High speed cameras captured the pre-impact particle diameter and velocity data as well as the post-impact fragment data. The initial stages of ice particle breakup were captured and studied at 1,000,000 frames per second with a high speed camera imaging at a plane normal to the impact surface. Fragment separation for equivalent diameter measurements was investigated at 50,000 frames per second with a camera normal to and below the impact area.
Initial results led to modifications in the experimental setup to improve the field of view and the resolution. In the modified experimental setup, a single-frame 29 megapixel camera located above the target was used to capture the fragment data. Repeat runs were conducted for ice particles with a diameter in the range between 2.4 and 2.8 millimeters, impacting at velocities between 30 and 74 meters per second. The fragment areas were measured and the corresponding equivalent diameters and histogram distribution were calculated. The average mean equivalent diameter was found to decrease with average velocity. The histograms for equivalent diameter distribution were non-normal with long tails, with most of the fragments having equivalent diameters concentrated toward the minimum value of the fragment size that could be measured. Factors affecting the accuracy of the data are identified and discussed.
