Aspirated compressor is a promising design concept to promote the working capacity of compression system and thus may result in an intensive interactions with adjacent rows, however, few extensive unsteady flow analysis have been conducted on this type of highly-loaded compressor. This work presents a three-dimensional numerical simulation of a low speed 1.5 stage low-reaction aspirated compressor (LRAC). The boundary layer suction is only implemented in the outlet vane to control the corner stall and boundary layer separation while no active flow control method is applied in the rotor. The total aspiration flow rate is around 3%. Both aspiration slot and plenum were integrated into the computational domain. Two operating points were selected with the aim to investigate the unsteady effects on the performance of the LRAC and to provide a preliminary unsteady description for this type of aspirated compressor. It is found that compared with the differences in 1D total aerodynamic parameters, evident departures are found in the radial distributions of stage outlet flow parameters between the steady and time-averaged results. For the unsteady case, the radial distributions of pitchwise-averaged parameters become more uniform due to the redistributed aspiration flow rate and the convection behavior of the rotor wake. For the aspiration scheme in the blade, although one-side-aspiration manner is applied, the aspiration flow rate presents a C-type distribution in the radial direction, and this tendency becomes more prominent for the forward slot and time accurate results. Besides, the fluctuation of aspiration flow rate is mainly focused on the upper span due to the intensive rotor outlet secondary flow here. Moreover, the potential effect of aspirated stator on rotor is also examined preliminarily. It is found that for the LRAC investigated in this paper, the rotor suction side is apt to be influenced by the downstream aspirated stator. Finally, some suggestions on the design of the aspirated compressor are provided.

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