Suppression of Nonsynchronous Vibration Through Intentional Aerodynamic and Structural Mistuning

Stapelfeldt, Sina; Brandstetter, Christoph

doi:10.1115/1.4052233

Cited by 4 publications

(5 citation statements)

References 28 publications

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“…In the presented study, an alternate pattern is applied by varying the sweep of the leading edge of every second blade. In [15] it is demonstrated, that the aerodynamic influence is mostly independent from the mistuning pattern, merely, structural mistuning is highly efficient in an alternating pattern for low mistuning amplitudes (1% frequency alternation). As stationary dual-passage RANS simulations are possible for this pattern, it was selected for the presented study.…”

Section: Intentional Aerodynamic Mistuningmentioning

confidence: 98%

“…As the fan can still operate at sufficient aerodynamic performance despite the part-span stall, this provides an efficient countermeasure against NSV. Additionally to this, the structural mistuning, which will be induced by the alternate sweep, will further reduce the sensitivity towards NSV as reported in [15]. Estimations based…”

Section: Part-speed Analysismentioning

confidence: 99%

“…A previous study [15] based on reduced order model analysis shows that intentional mistuning is effective to suppress convective non-synchronous vibration, either by varying blade eigenfrequencies or by alternating the aerodynamic behaviour of individual blades. The relevant flow structures develop close to the casing, near the leading edge and propagate around the circumference due to high blockage in the passage.…”

Section: Intentional Aerodynamic Mistuningmentioning

confidence: 99%

“…The aerodynamic design is comparable to the test case discussed in the present paper and hence of general interest for future low-speed architectures. The study in [15] has shown that specific types of asymmetry, either in form of structural (frequency) mistuning or geometric bladeto-blade variations (aerodynamic mistuning) can be successful to suppress NSV, building the basis for the study presented here.…”

Section: Introductionmentioning

confidence: 96%

See 3 more Smart Citations

UHBR Open-Test-Case Fan ECL5/CATANA: Numerical Investigation Near the Stability Limit Including Aerodynamic Mistuning

Fiquet

Ottavy

Brandstetter

2022

Volume 6B: Heat Transfer — General Interest/Additive Manufacturing Impacts on Heat Transfer; Internal Air Systems; Internal Coo

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Non-synchronous blade vibration (NSV) has received enormous attention in turbomachinery research, since it can be safety critical and its occurrence is less predictable than typical aeroelastic instabilities such as flutter. Typical for front stages of core compressors, NSV arises due to the propagation of one or multiple aerodynamic disturbances, traveling around the circumference and locking-in with structural blade vibration modes. Recent studies have shown, that modern low-speed fan architectures are also susceptible for this type of instability. With a specific focus on such aeroelastic instabilities, the open-test-case fan stage ECL5 has been designed by Ecole Centrale de Lyon. It is representative of near-future UHBR fan concepts with carbon-fibre composite blades. To prepare the experiments planned for 2022, unsteady full-annulus simulations have been carried out. Depending on rotation speed, the emergence of aerodynamic disturbances traveling around the circumference at a typical convective speed is observed, such as reported in studies on NSV on different configurations. These aerodynamic disturbances are identified as a possible source for non-synchronous vibration. At design conditions, an unstable aerodynamic behavior is observed, with part-span stall cells developing within the operating range predicted by RANS simulations. A study of intentional aerodynamic mistuning, in form of an alternating leading edge pattern is presented. At design speed, influence on steady performance and the onset of part-span stall is observed. At part-speed, the evolution of small-scale vortical disturbances, which can be responsible for the onset of NSV is affected significantly, providing a possible method to suppress NSV.

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Section: Intentional Aerodynamic Mistuningmentioning

confidence: 98%

Section: Part-speed Analysismentioning

confidence: 99%

Section: Intentional Aerodynamic Mistuningmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 96%

See 2 more Smart Citations

UHBR Open-Test-Case Fan ECL5/CATANA: Numerical Investigation Near the Stability Limit Including Aerodynamic Mistuning

Fiquet

Ottavy

Brandstetter

2022

Volume 6B: Heat Transfer — General Interest/Additive Manufacturing Impacts on Heat Transfer; Internal Air Systems; Internal Coo

View full text Add to dashboard Cite

show abstract

“…massflow and pressure ratio as well as on the analyzed eigenmode. Result of curve fit method for strain gauge measurement data at design speed Numerical simulations indicate an order of a few percent aerodynamic damping as long as no aeroelastic instability mechanism such as flutter or NSV [16] is present.…”

Section: Influence Of Modal Dampingmentioning

confidence: 99%

Experimental monitoring of vibrations and the problem of amplitude quantification

Schneider

Paoletti

Ottavy

et al. 2023

J. Phys.: Conf. Ser.

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Experimental monitoring of blade vibration in turbomachinery is typically based on blade-mounted strain gauges. Their signals are used to derive vibration amplitudes which are compared to previously determined modal scope limits, including a safety factor. According to industrial guidelines, this factor is chosen conservatively to ensure safe operation of the machine. For the experimental campaign with the open test case fan ECL5, which is representative for modern lightweight UHBR architectures, it is planned to conduct measurements close to the stability limit. These investigations require a close approach to the limit and hence demand for accurate quantification of vibration amplitudes to ensure secure operation without exhaustive safety margins. It is required that the surveillance is possible in real time and not only in post-processing. Historically, short-time Fourier transformations of vibration sensors are used, but the complex nature of coupled phenomena near the stability limit has an influence on the amplitude accuracy, depending on evaluation parameters. This was demonstrated in a previous study using fast response wall pressure transducers. The present study investigates the influence on blade vibration data of a modern composite material transonic fan. Different methods are compared, sensitivity to evaluation parameters is analyzed and guidelines are given for fast and robust surveillance of critical vibration modes.

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Unsteady Flow Structure of Rotating Instability in a 1.5-Stage Axial Compressor

Fujisawa,

Ohta,

Yamagami

et al. 2024

Journal of Turbomachinery

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Unsteady flow structure of the rotating instability (RI) in a 1.5-stage axial compressor is investigated through experimental and numerical analyses. In the tested compressor, the total pressure rise of the rotor stagnates at a certain flow coefficient before it increases again towards lower flow rate in a case involving a wide tip clearance. The RI appears beyond this stagnant point as the compressor is throttled. The RI indicates a gentle hump in the frequency spectra of wall pressure or the flow velocity near the tip in a range approximately 20 to 40% of the blade-passing frequency. As the flow rate decreases, the mode order of the RI increases, in contrast to more commonly reported tendency, while the propagation velocity remains constant. These features are well captured by DES of the half-annulus model. At its onset, RI is formed by the collision of the tip leakage vortex onto the pressure surface of the adjacent blade and subsequent vortex segmentation. This vortex structure spans two blade passages and propagates in the direction opposite to the rotor rotation. As the compressor is throttled, RI becomes more dominated by the circumferential propagation of vortex breakdown of tip leakage vortices, which occur simultaneously among neighboring passages with slight phase differences. The mechanism is discussed in relation to the temporal change in the blade tip loading. The frequency of vortex shedding increases with the reduction in flow rate and thus the increase in the number of RI disturbances.

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Suppression of Nonsynchronous Vibration Through Intentional Aerodynamic and Structural Mistuning

Cited by 4 publications

References 28 publications

UHBR Open-Test-Case Fan ECL5/CATANA: Numerical Investigation Near the Stability Limit Including Aerodynamic Mistuning

UHBR Open-Test-Case Fan ECL5/CATANA: Numerical Investigation Near the Stability Limit Including Aerodynamic Mistuning

Experimental monitoring of vibrations and the problem of amplitude quantification

Unsteady Flow Structure of Rotating Instability in a 1.5-Stage Axial Compressor

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