Investigation of Flow Instabilities Leading to Non-Synchronous Vibration of Compressor Blades

Result code in IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F46747885%3A24220%2F24%3A00012594" target="_blank" >RIV/46747885:24220/24:00012594 - isvavai.cz</a>

Result on the web

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DOI - Digital Object Identifier

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Result language

angličtina

Original language name

Investigation of Flow Instabilities Leading to Non-Synchronous Vibration of Compressor Blades

Original language description

The long and slender blades in modern turbomachines, especially in front stages of large compressors and last stages of turbines, are subjected to high and unsteady aerodynamic loads. Flow-induced vibration of the blades may occur due to multiple types of aeroelastic instabilities, including coupled-mode flutter or non-synchronous vibration. In the latter case, the oscillation onset does not occur due to unstable fluid-structure interaction, but as a result of a coherent fluid dynamic instability, typically at higher incidence angles and reduced frequencies. The current study investigates the coherent instabilities in flow past an isolated profile, potentially leading to non-synchronous vibration, by experimental techniques and numerical simulations. In a test rig designed for investigation of flutter in a linear blade cascade, an isolated compressor blade profile was mounted at incidence angles ranging between 10-40 deg and Mach numbers spanning from low incompressible to transonic flow regimes. The blade was instrumented with miniature Kulite pressure transducers with pressure ports distributed over the suction side of the blade. In addition to time-resolved pressure measurements, the flow field and shock wave structure near the blade was recorded using shadowgraphic and schlieren techniques by a high-speed camera. The flow field was also modeled using a 3D unsteady Large Eddy Simulation. For low angles of attack, a weakly irregular flow instability due to oscillation of the normal shock is detected at certain conditions, with two frequency peaks around 50 and 100 Hz. At medium angles of attack, the spectra of the Kulite pressure transducers contain a single peak roughly corresponding to the frequency of Strouhal vortex shedding, i.e. between 650-750 Hz. At high angles of attack and Mach numbers, Strouhal vortex shedding disappears and a new peak occurs in the spectra at a significantly lower frequency below 100 Hz. This low-frequency peak seems to be caused by oscillation of the separation zone boundary, forming a convergent-divergent channel and accelerating the flow to supersonic velocity.

Czech name

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Czech description

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Type

O - Miscellaneous

CEP classification

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OECD FORD branch

20304 - Aerospace engineering

Project

<a href="/en/project/LUAUS23231" target="_blank" >LUAUS23231: Origins and mechanisms of flutter and non-synchronous vibration in modern turbomachines operating at wide range of regimes</a><br>

Continuities

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Publication year

2024

Confidentiality

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů