Numerical simulation of three-dimensional flow in a one-stage centrifugal compressor with a diffuser of variable geometry has been performed using the ANSYS CFX 10 code. The computations were conducted using steady and unsteady flow formulations and employing the RANS two-equation turbulence models. Steady-state flow simulations in the compressor were done for two vaned diffuser geometries with different radial gaps. A detailed comparison with the experimental data reported in the literature for different operating points of the “Radiver” test case compressor is presented and discussed. Good agreement of the computed velocity field with the measurements data is obtained at the impeller exit. Downstream of the diffuser vane, prediction quality depends on the operating point. Transient simulations performed for the best operating point of the compressor did not improve considerably predictions of flow characteristics in the diffuser as compared to the steady-state approach.

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