Ice Particle Impacts on a Moving Wedge

Abstract

This work presents the results of an experimental study of ice particle impacts on a moving wedge. The experiment was conducted in the Adverse Environment Rotor Test Stand (AERTS) facility located at Penn State University. The wedge was placed at the tip of a rotating blade. Ice particles shot from a pressure gun intercepted the moving wedge and impacted it at a location along its circular path. The upward velocity of the ice particles varied from 7 to 12 meters per second. Wedge velocities were varied from 0 to 120 meters per second. Wedge angles tested were 0⁰, 30⁰, 45⁰, and 60⁰. High speed imaging combined with backlighting captured the impact allowing observation of the effect of velocity and wedge angle on the impact and the post-impact fragment behavior. It was found that the pressure gun and the rotating wedge could be synchronized to consistently obtain ice particle impacts on the target wedge. It was observed that the number of fragments increase with the normal component of the impact velocity. Particle fragments ejected immediately after impact showed velocities higher than the impact velocity. The results followed the major qualitative features observed by other researchers for hailstone impacts, even though the reduced scale size of the particles used in the present experiment as compared to hailstones was 4:1. Nomenclature ϕ = Time delay between the triggering of the pressure gun and the appearance of the frozen droplets at the desired height τ = Time delay between a triggering signal and the appearance of the rotor tip in the field of view α = Wedge angle AERTS = Adverse Environment Rotor Test Stand APL = John Hopkins University Applied Physics Laboratory D = Droplet diameter FAA = Federal Aviation Administration L= Distance from outer face of ice particle to wedge surface n-p = Frame of reference along the surface of the wedge, used for velocity calculations. s = Distance from (x c , y c ) to the point of impact t = Time it takes the particle starting at (x f ,y f ) to impact the wedge u = Horizontal velocity of the ice particle with respect to the x-y frame of reference v = Vertical velocity of the ice particle with respect to the x-y frame of reference V n = Velocity of the ice particle normal to the wedge surface Downloaded by UNIVERSITY OF ILLINOIS on October 1, 2015 | http://arc.aiaa.org |

Impact of a crushing ice particle onto a dry solid wall

“…The impact is observed using high-speed video systems. Many studies are focused on characterization of the kinematics of the post-impact fragments [2][3][4][5]. In particular, the restitution coefficient of the ice particles is measured [6,7].…”

Plans and Preliminary Results of Fundamental Studies of Ice Crystal Icing Physics in the NASA Propulsion Systems Laboratory

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“…Ice crystal ingested from the atmosphere likely break apart due to impacts with rotating and static surfaces inside the engine. Various studies are underway [8][9][10] suggesting that particles can catastrophically break apart with impacts at flight speeds. However, no one has yet measured the particle breakup inside a jet engine although studies 11 have begun to estimate such breakup based on these fundamental tests.…”

Ice crystal impact onto a dry solid wall. Particle fragmentation

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