An unsteady pressure measurement system was developed to measure the unsteady pressure field of an axial fan. The fan unsteady pressure fields of an inlet and outlet were obtained at three axial positions for seven-radial directions. The results showed that there is a relatively long response time for pressure drop both in inlet and outlet sections during the fan start-up. The measurements also showed that, due to the vortex shedding from the trailing edge of each fan blade, the fan outlet unsteady pressure distributions have a primary frequency related to the fan operating frequency. The time-dependent pressure measurements showed that pressure distributions of inlet and outlet during the fan start-up were severely unsteady and the main variation frequency of the pressure is much smaller than the fan rotational frequency. The pressure measurement on the fan blades showed that the pressure oscillations were mainly dominated by the vortex shedding from the fen blades. A flow visualization study was also performed to validate the flow characteristics near the blade surface. A complete set of time-dependent pressure measurements along the blade fan surfaces, fan inlet and outlet are suitable for an axial fan database for an industrial use as well as CFD code validation.

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