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GPPS Beijing19

16th - 18th September 2019

[225] Recent Insights into the Flow Topology Around Highly Loaded Tandem Vanes

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→ Alexander Heinrich
→ Dieter Peitsch

TU Berlin, Germany

Published: Beijing, 16th-18th September 2019

DOI 10.33737/gpps19-bj-225

Abstract

A large share in the weight of aero engines is attributed to the compressor module. Weight savings are crucial for the increase of overall propulsion system efficiencies. This has led to a steady reduction of stage counts in axial compressors, implying a constant increase in stage pressure ratios. The so called tandem blade configuration represents an innovative approach. The blades within a row are being replaced by pairs of blades placed successively in the streamwise direction, leaving a slot between the front blade’s trailing edge and the rear blade’s leading edge. Thus, separation from the blade suction side can be shifted towards higher incidences.

The work presented here is supported by experimental investigations which were conducted at a 2D linear stator cascade at the Chair for Aero Engines at the Technische Universit¨at Berlin. In the course of the experiments two different tandem configurations with a different Load Split (LS) setting are compared against a conventional single reference blade. All blades are designed as controlled diffusion airfoils (CDA) for a mach number Ma = 0:6 with an elliptical leading edge and a 50° turning angle. Wake flow measurements with a miniature fivehole- probe and multi-coloured oil flow visualisations are used to investigate the influence of the aerodynamic loading on the blade performance and the associated losses. This paper expands on previous findings as it includes a detailed analysis for negative incidence angles and a variation of the tangential (pitchwise) displacement of the two blade rows. The results of the oil flow visualisation complemented by wake flow measurements show the development of the secondary flow structures and the impact of varying Load Splits. In addition, the usage of multi-coloured oil flow allows a clear differentiation between origin and trajectory of different flow structures. By the use of tandem blades the losses can be, especially in the midspan region, significantly reduced. In contrast to the single reference blade, the working ranges of the tandem configurations exceed the reference stability limits even for negative inflow angles but remain below the improvements for positive incidence angles. Furthermore the influence of the percent pitch variation on the loss production and flow guidance has been identified.

View full paper as pdf

 

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