Study on adjoint-based optimization method for multi-stage turbomachinery

Abstract

Adjoint-based optimization method is a hotspot in turbomachinery. First, this paper presents principles of adjoint method from Lagrange multiplier viewpoint. Second, combining a continuous route with thin layer RANS equations, we formulate adjoint equations and anti-physical boundary conditions. Due to the multi-stage environment in turbomachinery, an adjoint interrow mixing method is introduced. Numerical techniques of solving flow equations and adjoint equations are almost the same, and once they are converged respectively, the gradients of an objective function to design variables can be calculated using complex method efficiently. Third, integrating a shape perturbation parameterization and a simple steepest descent method, a frame of adjoint-based aerodynamic shape optimization for multi-stage turbomachinery is constructed. At last, an inverse design of an annular cascade is employed to validate the above approach, and adjoint field of an Aachen 1.5 stage turbine demonstrates the conservation and areflexia of the adjoint interrow mixing method. Then a direct redesign of a 1+1 counter-rotating turbine aiming to increase efficiency and apply constraints to mass flow rate and pressure ratio is taken.