Session: 31-01 Tandem Design

Paper Number: 153120

Experimental and Numerical Evaluation of a Highly-Loaded Multistage Low-Speed Axial Compressor Featuring Tandem Stator Vanes: Part 3 — Robustness Investigation of Inlet Pressure Profile Variations 

An increase of aerodynamic loading of today's traditionally designed compressors is strongly limited as the geometry of the aerofoils used is already highly optimized. However, fundamental research has shown that a significantly higher loading can be achieved using tandem aerofoil configurations. This enabling innovative technology opens up new opportunities for increasing the specific work per stage beyond that of traditionally designed compressors whilst maintaining a high level of efficiency. For a given compressor pressure ratio, the tandem vane concept can be expected to significantly reduce the length and stage count of a compressor, with corresponding benefits for the architecture and cycle of future aircraft engines. New blading concepts are therefore investigated numerically and experimentally on a 3.5-stage low-speed compressor design, simulated in CFD and validated on the FRANCC research test rig. The design of the research compressor is targeted at rear stages of axial high-pressure compressors, consisting of an inlet guide vane and three stages with conventional rotors and tandem stator vanes. This paper series presents results of an investigation of the operational behavior, the steady-state and time-resolved flow field at design and degraded total pressure inlet profile conditions.

Part 3 of this paper series investigates the operational behavior robustness when subjected to variation in the inlet flow profile mainly with the increase in boundary layer thickness in the end wall region.

This paper investigates the robustness of a 3.5-stage highly loaded low-speed axial compressor with tandem stator vanes subjected to different inlet boundary layer distributions. Numerical results are presented in addition to experimental investigation to provide a better understanding of the underlying phenomena. For a proper comparison, the boundary conditions and the geometry are kept the same between the numerical and experimental approaches. The speedline characteristics are shown along with radial profiles to quantify the influence of different inlet boundary layer thicknesses. This paper also emphasizes the development of endwall blockage in a multistage system and the study of secondary flow characteristics in the rotor and stator affected by the variation of the inlet profile.

Part 1 and Part 2 of the paper series investigated the operational behavior and flow structure at the design configuration. Readers are advised to follow them to have a more in-depth understanding of the investigation.

With a comparison between the numerical and experimental investigation, the results show good agreement at the stator exit, however, the rotor exit has a mismatch showing that the rotor has more local throttling in the experiment. This is more clearly visible with an offset in the exit flow angle at the rotor exit. The speedline shows a higher efficiency for the experimental in comparison with the numerical. With a different inlet profile, the above-mentioned observations continue to be present. The differences with the variation of the inlet profile are pronounced until the first rotor, after that the differences appear to be less prominent. The speedlines of the different inlet profiles follow similar trends and operating range.

For the endwall blockage behavior, the agreement between the numerical and experimental results diminishes as one moves downstream. In addition, the effect of variation in inlet condition does not appear to have a major influence on the development of the endwall blockage behavior.

Presenting Author: Sagnik Banik Technical University of Munich, Institute of Turbomachinery and Flight Propulsion

Presenting Author Biography: Scientific Reseracher at Chair of Turbomachinery and Flight Propulsion, Technical University of Munich.

Authors:

Sagnik Banik Technical University of Munich, Institute of Turbomachinery and Flight Propulsion
Daniel Jäger Technical University of Munich, Institute of Turbomachinery and Flight Propulsion
Volker Gümmer Technical University of Munich, Institute of Turbomachinery and Flight Propulsion