Development of the ball-spine inverse design algorithm to swirling viscous flow for performance improvement of an axisymmetric bend duct

In the present study, the ball-spine inverse design algorithm is developed for swirling viscous flow regime to improve the performance of an axisymmetric 90-degree bend duct between the radial and axial diffuser of a centrifugal compressor. Performance improvement of the 90-degree bend duct is accomplished to increase its pressure recovery without separation. First, the effects of geometric parameters on flow separation are numerically studied and a safe margin is obtained for prevention of flow separation and stall. Then, the safe margin is enlarged to reach a higher pressure recovery via the shape modification of duct walls. The shape modification process integrates the BSA as shape modification algorithm and an axisymmetric flow analysis code as flow solver. Shape modification process is carried out by improving the current wall pressure distribution and applying it to the inverse design algorithm. Results show merits and robustness of the BSA for duct design in swirling viscous flow regime whereby the pressure recovery coefficient of the 90-degree bend duct increases up to 7%.