Stress sensitivity analysis for a wide-chord fan blade using an adjoint method

High-performance compressor design is best achieved with a good trade-off between aerodynamic and structural considerations, which requires efficient and accurate multidisciplinary design and optimization tools. As advanced compressors are defined with a large design space, their optimization is most efficiently achieved using a gradient-based approach, where the gradient can be computed using an adjoint method, at a cost nearly independent of the dimension of the design space. While the adjoint method has been widely used for aerodynamic shape optimization, its use for structural shape optimizations of compressor blades has not been as well studied. This paper discussed a discrete adjoint solver for structural sensitivity analysis developed within the open-source Computational Structural Mechanics (CSM) software CalculiX, and proposed an efficient stress sensitivity analysis method based on the Finite Element Method (FEM) using adjoint. The proposed method is applied to compute the stress sensitivity of a wide-chord fan blade in a high-bypass-ratio engine. The accuracy of the adjoint-based stress sensitivity is verified against central finite differences. In terms of computational efficiency, the adjoint approach is about 4.5 times more efficient than the conventional approach using finite differences. This works marks an important step towards fluid-structural coupled adjoint optimization of wide-chord fan blades.