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ROTATIONAL AIRFLOW IN ROUND DUCT AND ITS CONDITIONING FOR PARTICLE SAMPLING PURPOSE

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Paper number  034120,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14110) @2003
Authors:   Z. C. Tan, Yuanhui Zhang, Steven E. Ford
Keywords:   Rotational airflow, flow conditioner, particle sampling

Rotational airflow in round ducts downstream of a centrifugal device was investigated. Tests were conducted under room conditions. Duct diameters were 152mm and 203mm (6" and 8"). Average Reynolds numbers were within the range of 7x104–1.14x105. Airflow was characterized using velocity profile, nonuniformity, and steadiness. Within the accuracy of our tests, airflow in ducts was found nonuniform and unsteady within x/D=10. The nonuniformity of axial airflow was nearly independent of the average Reynolds number. For accurate dust concentration measurement, a flow conditioner with minimal particle loss is needed to make the air flow uniform and steady. A simple flow conditioner was tested. It decayed the rotational airflow to an acceptable level within x/D=1.5 to 2. Results in this paper also expand the database of study of rotational flow in ducts. Comparison with previous representative studies was discussed.