Research

Mistuning with aerodynamic coupling

As the blades deployed in turbomachines are subjected to high mechanical and thermal loads, these components must be manufactured with great precision. Despite this, small defects can occur, which become apparent during operation through disruptive vibration phenomena. This “mistuning” can have a negative impact on the acoustic behaviour and service life of the machine. Therefore, FVV initiated the first project on mistuning in 1993 and has since conducted numerous projects, thereby helping to bring this phenomenon under control from a technical perspective. One open question was how the blades in a blade ring influence one another via the fluid flowing through – in combination with non-linear coupling via frictional contact. Vibration and turbomachine experts from Leibniz University in Hanover collaborated to analyse the vibrations caused by the coupling of aerodynamics and structural mechanics in the “Mistuning with Aerodynamic Coupling I/II” project.

» Research on the phenomenon of mistuning is helping to improve our understanding of the resonance passages in turbomachine impellers, and thus contributing to operating safety. «
Dr.-Ing. Harald Schönenborn (MTU Aero Engines)

Motivation

Efficient turbomachines are playing a key part in the transition to greener energies. In order to guarantee safe operation despite mistuning, the blades, or blisks (blade-integrated disks) were previously designed with greater material thicknesses than would have been necessary based on the residual operating loads. However, this hinders efforts to further increase turbomachine efficiency. An ideal aerodynamic design is only possible if the mistuning effects that occur during operation can be calculated at an early stage of development.

» Our goal is to use experimental validation to make the ROMI simulation software – which was developed within the scope of FVV projects – ever more accurate. «
Prof. Dr.-Ing. Jörg Wallaschek (Institut für Dynamik und Schwingungen (IDS) | Leibniz Universität Hannover)

Methodology

The empirical basis for the further development of the simulation software was created via experiments performed at the involved institutes at the Leibniz University in Hanover. At the Institute of Dynamics and Vibration Research (IDS), an idealised turbine stage was agitated via magnetism in a vacuum in order to determine structural-mechanical couplings. On a test bench at the Institute of Turbomachinery and Fluid Dynamics (TFD), experiments were performed with a fluid flowing through, while taking the damping effect of the fluid into account. The findings gained through these experiments were then used to revise the modelling of the mistuning effect.

Result

The FVV project, which was completed at the end of 2019, significantly improved the existing ROMI (Reduced Order Model for Mistuned Turbine Blades) simulation program. By coupling the aerodynamics with the structural dynamics of the shroud or blade root, the increase in vibration amplitudes can now be predicted more accurately. The results also show that vibration behaviour is largely influenced by the relative movements of the blade roots in the mounting slots. ROMI is a non-commercial tool which can be used both in subsequent research projects and in the development of highly efficient turbomachines.

Documentation

Mistuning with Aerodynamic Coupling | Mistuning of bladings with aerodynamical and structural couplings | Funding No. 1164

Mistuning with Aerodynamic Coupling II | Mistuning of bladings with aerodynamical and structural couplings | Funding No. 1269

Themis

Status
Finalised

Programme
Public & FVV Funding

Budget
534.000,00 EUR

Time Period
2014-03-31 to 2016-12-30 Part I
2017-06-30 to 2019-12-30 Part II

Research Association for Combustion Engines (FVV) eV

Lyoner Strasse 18
60528 Frankfurt am Main
Germany

German Research Foundation (DFG) eV

Kennedyallee 40
53175 Bonn
Germany

Industry

Dr.-Ing. Harald Schönenborn
MTU Aero Engines AG

RTD Performers

1 | Institute of Dynamics and Vibration Research (IDS) - Leibniz Universität Hannover | I + II

Head of research:
Prof. Dr.-Ing. Jörg Wallaschek

2 | Institute of Turbomachinery and Fluid Dynamics (TFD) - Leibniz Universität Hannover | I + II

Head of research:
Prof. Dr.-Ing. Jörg Seume

Leibniz University Hannover

Institute of Dynamics and Vibration Research (IDS)

Appelstrasse 11
30167 Hanover
Germany

Leibniz University Hannover

Institute of Turbomachinery and Fluid Dynamics (TFD)

Appelstrasse 9
30167 Hanover
Germany

Projectmanagement

Dirk Bösel

FVV
+49 (0) 69 6603 1531
+49 (0) 69 6603 2531


Research Association for Combustion Engines eV

Lyoner Strasse 18
60528 Frankfurt am Main
Germany
T +49 69 6603 1345