Session: 36-01 Transition Ducts and Flow Interactions II

Paper Number: 103667

103667 - The Influence of Different Total Pressure Profile Inlet Distributions on the Performance of a Turbine Vane Frame With Splitter Vanes 

According to the goals and roadmap demanded by the Strategic Research and Innovation Agenda (SRIA) and specified in the “Flightpath 2050” report, a 75% reduction in CO2 emissions per passenger kilometer compared to the year 2000 technology standard must be available by 2050. To reach this target the efficiency of modern aero-engines has to be significantly increased, making design and concept changes necessary.

One concept to improve the efficiency goals of aero-engines and therefore help to reach the specified goals is a turbine vane frame (TVF). It is a transition duct in-between the high-pressure turbine (HPT) and the low-pressure turbine (LPT) and has three major purposes: guiding the flow to higher radii, incorporating the function of stator guide vanes of the first stage of the LPT, and passing structural components and oil pipes through the flow channel. The benefits of an aero-engine equipped with an aggressive TVF are the following; Due to the integration of the functionality of a stator vane row into the TVF not only the weight and the length of an aero-engine but also manufacturing costs can be reduced. A weight reduction leads directly to lower fuel consumption and therefore less CO2 emissions. Further, an increase in radius allows for a higher circumferential velocity of the LPT blades at lower rotational speeds of the shaft. A high circumferential speed of the blades is necessary to keep their aerodynamic loading low and avoid a high number of stages. However, a low rotational speed of the shaft is favorable to allow for a bigger fan in a direct drive aero-engine. Bigger fans make higher bypass ratios and therefore better fuel efficiencies of aero-engines possible. To achieve the best possible performance of an engine, equipped with a TVF, manufacturers try to push the aerodynamic design space and investigate the limits of such components.

From an aerodynamic point of view, a TVF is a complex component with multiple problematic areas where flow separations are possible to occur. The TVF investigated in the present paper is showing a small separation at the shroud endwall in experimental research. By finetuning the turbulence model this separation can be reproduced with CFD simulations. However, it was found the separation is very susceptible to different inlet boundary conditions like the total pressure profile distribution and the turbulence intensity. The present paper investigates the influences of such different 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 have therefore an impact on the performance of the component. Also, different shapes of the total pressure profile at the endwalls affect the boundary layers and have therefore a large impact on the secondary flows in the TVF. The present paper deals with an in-depth description of these effects. A key aspect of the paper will also be to describe the physical mechanisms of the separation at the shroud and to describe if and how this separation affects the performance of the TVF.

This work was carried out in the framework of the research project ReSiSTant. This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 760941. The authors gratefully thank the European Union for funding this project.

Presenting Author: Simon Pramstrahler Graz University of Technology

Presenting Author Biography: Born in Bolzano, Italy
Masters Degree in Mechanical Engineering at Graz University of Technology
PhD Student at Institute for Thermal Turbomachinery and Machine Dynamics

Authors:

Simon Pramstrahler Graz University of Technology
Christian Klemm Graz University of Technology
Andreas Peters GE Aerospace
Marios Patinios GE Aerospace
Mikel Lucas García De Albéniz Bionic Surface Technologies GmbH
Franz Heitmeir Graz University of Technology
Andreas Marn Graz University of Technology