Unsteady behavior of a radial fan in a pulsating flow field

The unsteady behavior of a radial fan in a pulsating flow field was studied experimentally. In a pulsating flow, compressor and turbine operating points do not match their steady performance curve, but exhibit a hysteresis loop instead. The shape of the hysteresis loop depends on the pulsating frequency. Measurements to calculate the Bode diagram of the fan and the phase lag of pressure and flow rate indicate that the phase lag controls the hysteresis loop. Moreover, to clarify the influence of air column resonance, the diffuser pump test was performed as a basic study. Computational fluid dynamics (CFD) analysis of the radial fan was carried out, and its results were compared with the experiment results. The unsteady curve calculated by CFD formed a hysteresis loop as observed in the experiment results.