Session: 40-06 Turbine Flowpath Geometry Effects

Paper Number: 126475

126475 - The Development of Turbulence Quantities in Different Intermediate Turbine Duct Configurations 

The experimental investigation examined the influence of high turbulence intensity, large scales, and turbulence anisotropy on the turbulence decay within the mid-turbine duct (MTD). The paper focuses on two different test configurations of the mid-turbine duct, which is an annular S-shaped channel used in turbofan engines to guide the flow from the high-pressure turbine (HPT) at a smaller radius to the low-pressure turbine (LPT) at a higher radius. Two state-of-the-art mid-turbine duct concepts are in focus. The most common duct is the turbine center frame (TCF), featuring non-turning struts. The exit-to-inlet area ratio of the TCF is higher than one, leading to a flow deceleration through the duct.—On the other hand, the turbine vane frame (TVF), also known as the integrated concept, can be considered a direct evolution of the diffusion duct. The integrated concept involves replacing the function of the LP turbine’s first vane row by introducing turning struts within the MTD. However, the TVF-integrated struts and splitters cause an acceleration in the tangential flow direction while deceleration in the meridional direction occurs. The overall Mach number increases from the inlet to the exit within the component.

The present study obtained hot-wire anemometry measurements using a triaxial and single hot-film probe. The experiments were conducted in a two-stage, two-spool transonic turbine test rig at the Institute of Thermal Turbomachinery and Machine Dynamics at the Graz University of Technology, which includes relevant purge and turbine rotor tip leakage flow. The test setups include the same (HPT) stage, different mid-turbine ducts, and a low-pressure vane or blade row. Several methodologies were used to process the data and to obtain the autocorrelation function, integral length scale, and turbulence kinetic energy dissipation rate.

The turbulence quantities at the inlet to the ducts show the same characteristics in both configurations. The acquired measurement data illustrates different turbulent mixing within the mid-turbine duct. Moreover, the high turbulence quantities at the exit of the diffusing duct dominated the shroud region. In contrast, the flow field at the TVF exit is dominated by TVF secondary flow and vane wakes. These results acquired under engine realistic rig flow conditions enable a deeper understanding of the relationship between loss and turbulence quantities for different mid-turbine duct configurations.

Presenting Author: Asim Hafizovic Graz University of Technology

Presenting Author Biography: Asim Hafizovic is my name. I am a doctoral student at Graz University of Technology. In 2019, I received my master's degree in mechanical engineering from Graz University of Technology and began my Ph.D. in the same department. The experimental investigation of the flow field in a turbine centre frame (TCF) and turbine vane frame using hot-wire anemometry measurements is the topic of my Ph.D.

Authors:

Asim Hafizovic Graz University of Technology
Nicolas Krajnc Graz University of Technology
Filippo Merli von Karman Institute for Fluid Dynamics
Marian Staggl Graz University of Technology
Francesco Mangini Graz University of Technology
Patrick Zeno Sterzinger GE Aerospace, Advanced Aviation Technology
Andreas Marn Graz University of Technology
Emil Göttlich Graz University of Technology