Unsteady Aerodynamic Performance of a Centrifugal Compressor With Oscillating Downstream Static Pressure

In many applications, centrifugal compressors experience various kinds of downstream pressure disturbances which can lead to unstable operation even at the design operating condition. In this paper, 3-D numerical simulations have been carried out to understand the dynamic behaviors of the centrifugal compressor for the pulsation of downstream pressure disturbances and 1-D model using the method of characteristics has been developed to predict the behaviors more effectively. Static pressure disturbances with a frequency range from 25Hz to 1300 Hz and constant amplitude have been introduced at the diffuser exit. Static pressure rise and mass flow rate deviated from the quasi-steady characteristic as the frequency increased. The fluctuation of mass flow rate at the diffuser exit was amplified or attenuated depending on the disturbance frequency. The fluctuation was severely amplified at a specific frequency which seemed to be an acoustic resonance of the present compressor model including an inlet duct, a blade passage and a diffuser. The result of 1-D model showed good agreements with that of 3-D numerical simulation.