Session: 31-01 Tandem Design

Paper Number: 151343

Experimental and Numerical Evaluation of a Highly-Loaded Multistage Low-Speed Axial Compressor Featuring Tandem Stator Vanes: Part 2 — Rotor Flow Field and Unsteady Flow
Phenomena 

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.

The present part 2 of the paper series focuses on the conventionally designed rotor within the research compressor. This rotor is designed for a wide operating range and benefits from the distribution of aerodynamic loading towards the stator implied by the flow path design. Still, the rotor is designed at a high level of loading. Due to this high loading at a moderate flow coefficient it shows the effect of double leakage in the tip region. This paper aims to investigate phenomena of the time-resolved rotor flow field.

Therefore, measurements are taken in the second stage of the 3.5-stage research compressor, up- and downstream of the rotor using hot-wire technique. For a comparison to the steady state flow field, five-hole probe measurements are available. Additionally, an array of fast-response pressure sensors is located in the casing of the rotor domain to obtain the flow field at the rotor tip.

The time-resolved casing pressure profile shows the pressure distribution across the rotor passage, the position and extent of the pressure minimum and maximum. In addition, the rotor tip leakage vortex can be identified in this pressure profile. A localization of the trajectory of the tip leakage vortex shows that it hits the neighboring rotor blade, representing double leakage. The hot-wire measurements are first used to investigate the time-resolved flow field downstream of the rotor and the secondary flow structures in the rotor passage. Furthermore, the measurements will improve the understanding of the interactions between the tandem stator and the conventional rotor of the current built, including details about the time dependent tandem gap flow and secondary flow structure variations.

Furthermore, the analysis of the rotor flow in this built will be the baseline for future tests, where a fully tandem configuration will be investigated.

Presenting Author: Patrick Steudel Technical University of Munich, Institute of Turbomachinery and Flight Propulsion

Presenting Author Biography: Patrick Steudel studied mechanical engineering and aerospace at the Technical University of Munich. He got engaged with flight propulsion during his Bachelor’s thesis. Following that, he joined the Institute of Turbomachinery and Flight Propulsion at Technical University Munich as a student assistant and later as a researcher.
There, he supported the buildup of the new low-speed axial compressor test rig “FRANCC” at the institute. Since the commissioning of the rig, he continued to support the experimental investigations there, being mainly responsible for aerodynamic probes and their calibration. He will then continue the testing activities with a new setup of the FRANCC featuring a fully tandem-blade configuration, consisting of hybrid rotors and tandem stators. His research focus lies on the investigation of the multistage behavior and unsteady flow phenomena of the hybrid rotor design.
In addition to his research activities, he supports a practical course on testing in fluid machinery and flight propulsion.

Authors:

Patrick Steudel Technical University of Munich, Institute of Turbomachinery and Flight Propulsion
Daniel Jäger Technical University of Munich, Institute of Turbomachinery and Flight Propulsion
Lukas Selmayr Technical University of Munich, Institute of Turbomachinery and Flight Propulsion
Volker Gümmer Technical University of Munich, Institute of Turbomachinery and Flight Propulsion