Abstract

In search of improved efficiency, gas turbine engines are trending to higher overall pressure ratio (OPR) configurations. As OPR increases, the engine core size decreases. This introduces new design challenges as not all blading features are scalable. For example, the turbine blade trailing edge minimum allowable radius is a mechanical constraint. As the core size decreases, blade trailing edge radii reach a mechanical limit and cannot be further scaled. Consequently, as engine cores get smaller more aerodynamic blockage must be introduced to conserve the blading aspect ratio and meet the minimum allowable trailing edge radius design requirements. An alternative to increasing the blockage is to design with low aspect ratio blading. Low aspect ratio designs do decrease blockage but they also increase the secondary flows, resulting in highly three-dimensional turbine passage flow fields. These classes of flows require a design approach that addresses the three-dimensional effects. This paper provides an industry perspective on low aspect ratio turbine blade design optimization. The optimization is performed using an in-house adjoint-based computational fluid dynamics toolset. The toolset will be described in detail, as well as some of the lessons learned during application of the tool. The results show that an adjoint-based optimization approach can be used to significantly improve turbine efficiency for a low aspect ratio design.