Unsteady pressure field investigation of an axial fan - blade unsteady pressure field measurement

摘要

A 1.829 in (6 ft) diameter industrial large flow-rate axial fan operated with 1770 rpm was studied experimentally in laboratory conditions. The flow characteristics near the fan blade surfaces were investigated by measuring the pressure distributions on the blade suction and pressure surfaces and the results were discussed by comparing with analytical formulations. Flow visualizations were also performed to validate the flow characteristics near the blade surface and demonstrated that the flow characteristics near the fan blade surface were dominated by the centrifugal force of the fan rotation, which result in strong three-dimensional flows. The time-dependent pressure measurement showed that the pressure oscillations on the fan blade were significantly dominated by vortex shedding from the fan blades. It was further demonstrated that the pressure distributions during the fan start-up were severely unsteady, and the main frequency variation of the static pressure was much smaller than the fan rotational frequency. The time-dependent pressure measurement when the fan operated at a constant speed showed that the magnitude of the blade pressure variation with time and the main variation frequency was much smaller than the fan rotational frequency. The pressure variations that were related to the vortex shedding were smaller than the fan rotational frequency. The complete set of blade-surface pressure measurements obtained can be used as a guide for performance improvements, vibration analysis, and CFD code validation.