A NURBS-Based Optimization Tool for Axial Compressor Cascades at Design and Off-Design Conditions

Abstract

Optimization techniques based on evolutionary strategies have become a general procedure in the industrial and academic worlds for the aero-mechanical design of turbomachinery blades. The airfoil geometry, parameterized using NURBS curve model, has been optimized minimizing the loss at both design and off-design working conditions, guaranteeing also the mechanical requirements. In the present work the authors, using a genetic algorithm (GA)-based tool, have explored the design space of modern axial flow compressor profiles reaching the target of better performance. The outlet flow angle and the mechanical-related quantities have been taken into account as design constraints. A fully integrated software procedure has been developed and applied to the redesign of existing airfoils in two different ways. The first redesign has been performed only at design condition while a further redesign has been implemented taking into account also two reference off-design conditions in order to increase the useful operating range. These reference off-design conditions are automatically obtained by using a loss curve model recently presented by the authors for prescribed velocity distribution airfoils. The computational tool has been applied for the optimization of the UKS-31 stator midspan section showing improved aerodynamic performance for both single and multi-point analysis.