Interpretation of Stall Precursor Signatures

Brandstetter, Christoph; Ottavy, Xavier; Paoletti, Benoît; Stapelfeldt, Sina

doi:10.1115/1.4051709

Cited by 15 publications

(13 citation statements)

References 26 publications

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“…The paper has received a lot of attention, but it delivers few physical explanations regarding the nature of these disturbances or the mechanisms by which fluid and structure couple. (In the authors' opinion, the interpretation in this paper is misleading, and an interpretation of the measured data which is consistent with the latest understanding of NSV is possible [10]). Kielb et al [5] provided a physical explanation of NSV in the front stages of a compressor rig.…”

supporting

confidence: 57%

Analysis of a Linear Model for Non-Synchronous Vibrations Near Stall

Brandstetter

Stapelfeldt

2021

IJTPP

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Non-synchronous vibrations arising near the stall boundary of compressors are a recurring and potentially safety-critical problem in modern aero-engines. Recent numerical and experimental investigations have shown that these vibrations are caused by the lock-in of circumferentially convected aerodynamic disturbances and structural vibration modes, and that it is possible to predict unstable vibration modes using coupled linear models. This paper aims to further investigate non-synchronous vibrations by casting a reduced model for NSV in the frequency domain and analysing stability for a range of parameters. It is shown how, and why, under certain conditions linear models are able to capture a phenomenon, which has traditionally been associated with aerodynamic non-linearities. The formulation clearly highlights the differences between convective non-synchronous vibrations and flutter and identifies the modifications necessary to make quantitative predictions.

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supporting

confidence: 57%

Analysis of a Linear Model for Non-Synchronous Vibrations Near Stall

Brandstetter

Stapelfeldt

2021

IJTPP

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“…Within the mentioned broadband hump around EO 8, which is visible at OP DS4 in the WPT spectra of both configurations, distinct frequency peaks at EO 7.2 and EO 8.8 establish. These peaks indicate the presence of convective disturbances with nearly constant propagation speed in the stationary frame of reference, which is determined by the aerodynamics of the mean flow [33]. Rodrigues et al [28] have shown that it lies within 55 and 60 % of the rotational speed for the fan investigated here, what corresponds to a propagation velocity of…”

Section: Aeroelastic Behaviormentioning

confidence: 53%

“…The reduction in massflow from OP DS2 to OP DS4 results in rising noise levels and in the formation of a broadband hump around EO 8. This broadband hump denotes the presence of convective disturbances as described by Rodrigues et al [28] and Brandstetter et al [33].…”

Section: Unsteady Aerodynamicsmentioning

confidence: 67%

“…Due to a modulation of this frequency at the rotor blades, strong peaks around the BPF are visible for the configuration, for which the 14 Hz peak is observed. In addition, scattering of the acoustic mode causes sidebands around the BPF with distances of multiple integer EO (see [33] for details). Besides these differences at OP DS2 and OP DS3 related to the acoustic mode, it is noticed that noise levels are identical for both configurations.…”

Section: Unsteady Aerodynamicsmentioning

confidence: 99%

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Influence of a Turbulence Control Screen on the Aerodynamic and Aeroelastic Behavior of a UHBR Fan

Schneider

Paoletti

Ottavy

et al. 2022

Volume 8A: Structures and Dynamics — Aerodynamics Excitation and Damping; Bearing and Seal Dynamics; Emerging Methods in Engine

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A composite fan stage representative of a modern Ultra High Bypass Ratio (UHBR) architecture has been investigated experimentally on a novel test facility at Ecole Centrale de Lyon. For these experiments, a turbulence control screen (TCS), a hemisphere, consisting of honeycomb and wiremesh panels, was installed in front of the rig in order to ensure homogeneous, disturbance-free inflow conditions. This kind of screen was developed in the early 1970 years to investigate flight-noise on static test beds. Today, they are commonly used in aero-engine and fan tests, because they improve the accuracy of acoustic measurements and provide more reproducible performance tests. However, the influence of such screens has been investigated only from an acoustic point of view in the past. This study presents a back-to-back comparison of measurements with and without the TCS, which allows a characterization of the effects on aerodynamic and aeroelastic behavior of the fan stage. The investigation was carried out for multiple stable operating points on two different speed lines to obtain a global image of the influence at part and design speed. The utilization of steady and unsteady instrumentation in different axial and circumferential duct positions allows a detailed analysis of similarities and differences of the configuration without and with the TCS and provides insight into underlying physical mechanisms.

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“…One frequently cited study of the topic links the excitation of structural vibration modes to socalled 'rotating instabilities', aerodynamic disturbances which propagate around the circumference, but offered few physical explanations regarding the physical mechanisms driving fluidstructure coupling [2]. The interpretation in this paper is misleading, and an interpretation of the measured data which is consistent with the latest understanding of NSV is possible [3]. Kielb et al [4] provided a physical explanation of 'nonsynchronous vibrations' in the front stages of a compressor rig, occurring at part-speed.…”

Section: Introductionmentioning

confidence: 82%

Suppression of Nonsynchronous Vibration Through Intentional Aerodynamic and Structural Mistuning

Stapelfeldt

Brandstetter

2021

Journal of Turbomachinery

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Non-synchronous vibrations (NSV) arising near the stall boundary of compressors are a recurring and potentially safety-critical problem in modern axial compressors and fans. Recent research has improved predictive capabilities and physical understanding of NSV but prevention measures are still lacking. This paper addresses this by systematically studying the influence of aerodynamic and structural mistuning on NSV. This is achieved by incorporating mistuning effects in a validated linear model, in which individual blade modes are modelled as single-degree of freedom mass oscillators coupled by a convected aerodynamic disturbance term. The results demonstrate that both structural and aerodynamic mistuning are effective. While structural mistuning improves stability by preventing aero-structure lock-in, aerodynamic mistuning, which locally reduces the tip blockage, attenuates the aerodynamic disturbance causing NSV. In the latter case, the circumferentially-averaged conditions are shown to be most influential, while the pattern plays a minor role. A combination of moderate aerodynamic and structural mistuning (1%) was also found to be effective. These findings are relevant for design decisions, demonstrating that small blade-to-blade variations can suppress NSV.

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Interpretation of Stall Precursor Signatures

Cited by 15 publications

References 26 publications

Analysis of a Linear Model for Non-Synchronous Vibrations Near Stall

Analysis of a Linear Model for Non-Synchronous Vibrations Near Stall

Influence of a Turbulence Control Screen on the Aerodynamic and Aeroelastic Behavior of a UHBR Fan

Suppression of Nonsynchronous Vibration Through Intentional Aerodynamic and Structural Mistuning

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