Preparation for Scaling Studies of Ice-Crystal Icing at the NRC Research Altitude Test Facility

This paper describes preparation for ice-crystal icing scaling work utilizing the Cascade rig at the National Research Council (NRC) of Canada\u2019s Research Altitude Test Facility (RATFac). Tests supporting this work and continuing the collaboration between NASA and NRC on ice-crystal icing took place between March 26 and April 11, 2012. The focus was on several aspects but emphasized characterization of the RATFac cloud including watercontent and test-section uniformity as well as particle-size measurements. Water content measurements utilized the Science Engineering Associates (SEA) Multi-Element probe while cloud uniformity measurements used light scattering from particles passing through a laser sheet. Finally, particle size-spectra measurements used two developmental shadowgraphsystems. Details of these measurements as well as selected results are presented. An analysis algorithm is presented that interprets mixed-phase measurements from the SEA probe using calibrations from individual water and ice clouds. The analysis is applied to one mixedphase data set generated with a glaciated cloud combined with supplemental water. The test section temperature was below freezing to prevent the natural melting of the ice crystals. The analysis algorithm relies on the measurement of test-section humidity to account for cloud evaporation. Results of the cloud-uniformity measurements using scattered light suggest that the measured intensity is a good first-order measurement of concentration, independent of the water phase. Steeper intensity gradients across the test section are observed with increasing ice-water content. For particle-size measurements, both shadowgraphy methods provide high-quality images of the particles. These images will be processed to establish particle-size distributions and morphology characteristics. The results from this work will help guide future ice-crystal icing research including scaling studies.Peer reviewed: YesNRC publication: Ye