Centrifugal compressor return channel shape optimization using adjoint method

Abstract

This thesis describes the construction of an automated gradient-based optimization process using the adjoint method and its application to centrifugal compressor return channel loss reduction. A proper objective function definition and a generalized geometry parametrization and manipulation algorithm were developed, and the appropriate adjoint equations and boundary conditions were derived for internal flow of an axisymmetric incompressible laminar flow. The adjoint-based gradient calculation was then validated against finite-difference calculations and embedded in a quasi- Newton optimization algorithm. An optimal design was proposed, which achieved an approximately 5% performance improvement compared to the baseline design in an incompressible laminar flow. The geometry was assessed in a compressible turbulent flow at the actual Mach number and Reynolds number and found to yield a 11% performance improvement for an axisymmetric channel with a previously optimized geometry.