Parameterization and design of transonic compressor blades

Abstract

Economical and environmental requirements are driving the development of more efficient aircraft engines. For the compressor this has led to fewer stages and higher pressure ratios. To be able to fulfill these requirements while maintaining high efficiency and high stability, off design performance must be considered early in the blade design process. Recently, a new set-based design method accounting for stability at part speed as well as efficiency at the design point has been developed. This method makes use of a global optimizer where the end result is an optimal set of compressor stages, i.e. a pareto-front, which shows the trade-off between efficiency and stability. However, the optimal solutions are highly dependent on the blade parameterization tool as it sets the limitations to the allowed design space. In order push the pareto-front towards higher efficiency and higher stability, a new blade parameterization tool is developed where Bezier curves are used to represent the blade geometries. This tool, called Polly, is written in Matlab and is introduced into the existing workflow. To investigate its capabilities it is used to re-design the rotor and stator profiles positioned at 95% span of the first stage rotor of the low pressure compressor called Blenda. The investigation shows that the new parameterization is able to generate more efficient and stable blades compared to the current blade generator, called Volblade. One reason is that the suction side and pressure sides are created independently of each other, but at a cost of more parameters and longer optimization time.