Exploring a Database of Optimal Airfoils for Axial Compressor Design

Abstract

Ensuring a high degree of commonality among a range of products can dramatically decrease development costs. This paper aims to generate a highly versatile compressor airfoil family that covers most applications in the core compression system of aircraft engines and stationary gas turbines. This airfoil family is generated by filling a database with optimized airfoil shapes. The database is structured in seven dimensions, denominated as 'design requirements': blade stagger angle, pitch-chord ratio, profile area and the following design point properties: inlet Mach number, Reynolds number, streamtube contraction and aerodynamic loading. Additional constraints are imposed to ensure that feasible airfoils exist for each set of requirements. These constraints include limitations for profile area depending on inlet Mach number and limits for axial Mach number. To fill this seven-dimensional space, a large number of airfoils is generated by means of numerical optimization at discrete points in this space. The target is to find airfoil shapes that have low losses and ensure stable operation over wide incidence ranges. Design and off-design performance is evaluated with the blade-to-blade flow solver MISES. The solver is well established among industry and research and it is validated to a high degree by experiments. To verify the optimization strategy, it is tested on a set of existing compressor airfoils. The optimized geometries of four of the airfoils under investigation are found in the appendix. The database offers a wide variety of airfoils for different applications. Airfoils for sub- and supersonic inflow are covered as well as airfoils suited for placement at hub or casing. The benefit of using airfoils optimized for their specific purpose over having generic airfoil shapes is discussed as well. In future, this airfoil database will be used to study novel concepts for aircraft engines.