Gradient-Free Aerodynamic Optimization With Structural Constraints and Surge Line Control for Radial Compressor Stage

Abstract

Abstract The concept and design of High Temperature Heat Pumps (HTHP) including their components for specific temperature needs is a time consuming and interdisciplinary task. Especially, the design of compressor geometries has a big impact on the overall performance and the initial costs of the system. For this reasoning, in this work an automated aerodynamic gradient-free optimization including structural constraints for the geometry of a radial compressor impeller blade as well as diffusor vane geometry for water steam, that is applied in a reverse Rankine cycle based HTHP, is presented. Objective of the optimization is the isentropic efficiency in the aerodynamic design point (ADP) of the compressor. Constraints for the pressure ratio, mass flow rate and limits for stresses in blade and disk geometry satisfy requirements of the cycle simulation of the whole HTHP system and structural needs. The optimization method is based on evolutionary algorithms and stochastical surrogate models. Additionally, a highly throttled operating point is regarded to achieve an acceptable distance to the surge line. These types of optimization problems are often characterized by lots of unconverged iterations due to unstable computational fluid dynamic simulations (CFD). To encounter this, a study of the optimization process with different surrogate models is presented. The results are discussed with respect to convergence history as well as objective and constraint improvement.