Parallel steady/unsteady flow simulations of an 8.5-stage axial compressor

Both the steady and unsteady Reynolds averaged Navier–Stokes (RANS) simulations play a crucial role in the aerodynamic performance prediction and design of multi-stage axial compressors. Although the current industrial standard for such simulations is mainly based on the steady RANS method with the single passage per row model, the high-fidelity unsteady RANS (URANS) method with the full annulus passages per row model is able to capture even more flow details. However, the resulting huge computational burden restricts the URANS simulations of axial compressors to small stage counts, simplified passage models and scaled-down machine sizes. In this work, parallel algorithms are adopted to speed up the RANS/URANS simulations of a full-scale state-of-the-art 8.5 stage axial compressor with 0.76 billion grid elements. Simulation results highlight that the steady/unsteady predictions of aerodynamic performance agree well with the test data within the errors of 1–2 %, and the inter-row interface treatments of steady mixing plane approach and unsteady sliding mesh approach satisfy the interface flux conservation tightly. Comparing with the circumferential mixing treatment in steady approach, the unsteady full annulus model is demonstrated to have the advantages of continuous transfer of the flow wake and shock wave across the inter-row interfaces. The underestimation of radial transport in the steady approach is explained by the fact that the axial vorticity across the rotor/stator interfaces is altered significantly resulting from the circumferential uniformity treatment of the spanwise velocity. This work is valuable for the further development and design of a new generation of air processing unit and aeronautic engine compressors.