The Influence of Different Total Pressure Profile Inlet Distributions on the Performance of a Turbine Vane Frame With Splitter Vanes

A turbine vane frame (TVF) is a component located in between the high-pressure and the low-pressure turbine of future aeroengines. It combines the aerodynamic purposes of a turbine center frame (TCF) and the stator vane row of the first low-pressure turbine stage in one component. Further, it is also used to house structural components and instrumentation, and to guide oil pipes and wires to the inner part of the engine. With the usage of a TVF, the size and weight of the engine can be reduced, and therefore, its efficiency increased. Combined with other technologies, this can help to reach the goals and roadmap demanded by the Strategic Research and Innovation Agenda (SRIA) to reduce the CO2 emissions per passenger kilometer compared to the year 2000 by 75% in the year 2050.

From an aerodynamic point of view, a TVF is a complex component with multiple problematic areas where flow detachments can occur. The TVF investigated in the present paper shows a small separation at the shroud endwall in experimental research. By choosing the right turbulence model, this separation can be reproduced with CFD simulations. However, the separation was very susceptible to different inlet boundary conditions like the total pressure profile distribution and the turbulence intensity. The present paper investigates the influences of multiple inlet total pressure distributions on the secondary flows, boundary layers and the flow field in general in the turbine vane frame. Further, it deals with the impact of the changes in the flow field on the performance of the turbine vane frame. Depending on the design and the operating point of aerodynamic components upstream of the TVF, the total pressure profiles can vary in a significant way. Different concentrations of the total pressure provoke different distributions of the losses in the TVF and therefore impact the performance of the component. Also, different shapes of the total pressure profile at the endwalls affect the boundary layers and therefore impact the secondary flows in the TVF.

In the present paper, two key characteristics describing a simple total pressure profile are investigated: The boundary layer thickness and the skewness of the profile. The description of the effects of those profiles on the TVF can help the design engineers to improve the design of a TVF and upstream components to increase efficiency. A key aspect of the paper is to describe the physical mechanisms of secondary flow and losses in the TVF and if and how separations affect the performance of the TVF.