Flow Evolution Through a Turning Midturbine Frame with Embedded Design

Abstract

The paper discusses the time-averaged flow of a new-concept turbine transition duct placed in a two-stage counter-rotating test turbine. As a possible architecture for the turbine transition duct of future engines, the structural vanes carrying the bearing loadings can be integrated with the first low-pressure vane row in one aerodynamically optimized wide-chord vane called the turning midturbine frame. To increase the flow uniformity and to decrease the unsteady content of the flow, a baseline turning midturbine frame is redesigned by embedding two splitter vanes into the strut passage. The discussion on the flowfield is based on numerical results obtained by computational fluid dynamics and validated by aerodynamic measurements. In particular, the splitters are seen playing a major role in suppressing the big structures generated by the struts and the secondary flows of the high-pressure turbine. On the other hand, new losses are introduced by the splitters. Such structures play a decisive role in the overall component performance; therefore, their effect should be properly understood. This work provides a deep insight into the flow physics of an embedded turning midturbine frame for next-generation aeroengines, which is seen as a promising architecture in order to compact the engine size while keeping component performance high. The present work can be considered as a first attempt to implement splitter blades into an already existing turning midturbine frame design, and its value lies in a thorough experimental and computational study on the losses and benefits of such a design.