Rapid design approach for U-bend of a turbine serpentine cooling passage

Abstract

The goal of this study is to propose a rapid design approach for designing a minimum pressure loss U-bend in a turbine internal cooling passage using topology optimization. The total pressure loss in the bend region is critical, as the presence of U-bend dominates the pressure loss so that it demands increased coolant feed pressure. However, it is challenging to come up with general design rule for U-bend with minimum pressure loss. The proposed rapid design approach can be applied as a 3D U-bend geometry optimization tool. The minimization of the total pressure loss is achieved by implementing topology optimization that uses a continuous adjoint approach with steepest-descent method. An incompressible steady-state flow (low-fidelity simulation) solver is applied for the design space, which is modeled as a porous medium with variable porosity. A series of design optimization in 2D and 3D is conducted at a Reynolds number of 100,000 based on the bulk inlet velocity. 3D U-bend configurations are produced by the proposed rapid design approach in a few hours.High-fidelity computational simulations are also carried out on the optimized 2D and 3D U-bend configurations to evaluate the proposed rapid design approach. The computational studies are performed by solving the compressible, turbulent steady-state Reynolds-averaged Navier-Stokes (RANS) equations applying two turbulence models: Spalart-Allmaras and Shear Stress Transport (SST) model. The high-fidelity simulations predict a relative improvement of maximum 26.8% in total pressure drop with respect to the 3D baseline configuration. The results indicate that the proposed approach can be reliable fast design tool for optimizing U-bend geometry in incompressible flow regime.