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ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
DEVELOPMENT OF A SPRAY BAR SYSTEM FOR THE SIMULATION OF SUPERCOOLED WATER DROPLETS IN THE NIDF CLIMATIC WIND TUNNEL
Submission Author:
Pedro Petindá , RJ , Brazil
Co-Authors:
Lígia Froening, Juliana Loureiro, Valter Aibe
Presenter: Pedro Petindá
doi://10.26678/ABCM.ENCIT2016.CIT2016-0435
Abstract
The Climatic Wind-tunnel of NIDF/COPPE/UFRJ was built in order to simulate extreme atmospheric cloud conditions, i.e., low temperature and high velocity turbulent flows under controlled humidity conditions. This paper presents the development of a spray bar system designed to simulate supercooled water droplets for ice-accretion investigation purposes. The spray bar system is comprised by six independently controlled nozzles, which are driven by separate compressed-air and liquid supply lines. Droplet diameter distribution and liquid water content inside the wind-tunnel can be varied through changes in the air pressure and liquid flow rate. The spray bar system was installed in a settling chamber located immediately upstream of the wind tunnel contraction. To investigate the uniformity of the simulated ice cloud a rectangular grid composed by 6mm diameter rods was installed on the middle of the 2m long test section. The droplet size distribution was measured under different flow velocities, temperatures and humidity. Mean flow and turbulence measurements were made with the aid of a PIV (Particle Image Velocimetry) system. The supercooled large droplets were characterized through a Shadow Sizer system. The wind tunnel temperature was monitored with a set of thermocouples and a humidity sensor. A special sampling probe was developed for the measurement of the liquid water content, which is an important parameter for the prediction of ice accretion on aircraft wings and empennages. This experimental database establishes the operating envelopes of the Climatic Wind-tunnel of NIDF and quantifies its capability to produce large droplet icing clouds. For general icing investigation purposes, the wind-tunnel results are compared with FAA icing certification criteria.
Keywords
Wind Tunnel, Turbulence, Spray, Droplet size distributions, icing
