Experimental Methods Applied in a Study of Stall Flutter in an Axial Flow Fan

Gill, John; Capece, Vincent R.; Fost, R. B.

doi:10.1155/2004/596706

Cited by 5 publications

(6 citation statements)

References 16 publications

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“…The flow will separate and reverse from the last stage blade because of the effect of the diffuser of stator blades and the centrifugal force of rotor blades [1]. A large range of separation vortices is formed on the pressure surface, which causes a dramatic change of the blades dynamic stress [2][3][4], as well as blades vibration [5][6][7][8]. When the volume flow decreases to a certain extent, the last stage blades will go into the steam blast condition, which leads to a sudden temperature increase and the over-temperature deformation of the blade surface [9].…”

Section: Introductionmentioning

confidence: 99%

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

et al. 2019

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The inlet steam flow of steam turbine is obviously reduced and even in the state of small volume flow when the thermal power unit is involved in peak load operation, which greatly influences the safety of steam turbine. The last stage flow field of steam turbine under small volume flow condition is calculated by the CFX to study the formation, development, influencing range, and the variation rule of the flow separation vortex cores. The results show that the flow separation vortices appear near last stage blade at 30% of the rated volume flow. With the decrease of volume flow, the flow separation vortices gradually spread to the root of blade. When the volume flow decreases to 8% of the rated volume flow, the flow separation vortices almost occupy the whole blade. The position of the flow separation vortex cores shifts from 72.7% of the relative blade height to 49.1%. The results of this paper lay a foundation for the safety analysis of the last stage blade in the steam turbine under the small volume flow condition.

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Section: Introductionmentioning

confidence: 99%

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

et al. 2019

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“…The background theory of this study owes much to the work of Mengle [3]. When only concerned with frequency shifts due to reference frame change from rotating to stationary, Kurkov [1,2] and other researchers [3,4] derived practically the same equations, but Mengle's study may be the only one that also handles the amplitude characteristics of airborne acoustic waves emitted by the blade vibration. Mengle derived the following formula for frequency shifts in rotating blade vibration observed from a stationary frame, first displayed adopting the same nomenclature used in [3].…”

Section: Review Of Mengle's Theorymentioning

confidence: 97%

“…Theories pertaining to blade vibration detection on rotating parts by sensors installed on a stationary reference have existed since the 1980s [1][2][3][4]. Most of the research, however, deals with compressor-stage flutter detection and characterisation, i.e., non-integral modes.…”

Section: Introductionmentioning

confidence: 99%

Pulsation and Vibration Measurement on Stator Side for Turbocharger Turbine Blade Vibration Monitoring

Ando

2020

IJTPP

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Mechanically robust turbine design with respect to blade vibration is challenging when dealing with nozzle-ring fouling and wear. Especially for engines operating with heavy fuel oil (HFO), the nozzle rings of the turbocharger turbines are prone to severe degradation in terms of contamination with unburned fuel deposits. This contamination will lead to an increased excitation of blade resonances in comparison to the nominal design. Due to the statistical character of contamination, long-term monitoring of blade vibration amplitudes would be beneficial. In the harsh environment of HFO operation, however, conventional blade vibration measurement techniques, such as those using strain gauges or blade tip timing, cannot work reliably for a long period. Thus, the objective of this research is to develop a method that enables the monitoring of turbine blades using pulsation or vibration sensors installed on the stator side. Almost a dozen turbines, both radial and axial, have been examined in order to determine a proper measurement chain/position and analytical method. Even though the challenges specific to the turbocharger turbine application—that high-frequency (up to 50 kHz) acoustic radiation from turbine blades has to be detected by a sensor on the stator side—were demanding, in the course of the investigations several clear examples of turbine blades engine-order resonance detection were gathered. Finally, the proposed method has been tested successfully in a power plant for over one year.

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“…Asynchronous vibration is presented as a coherent trace over the blue background denoting the noise floor. The average assembly amplitude and nodal diameter of travelling wave responses can be found by observing the vibration from two different angular positions [46][47][48]:…”

Section: Asynchronous Vibrationmentioning

confidence: 99%

Non-Contact Measurement of Blade Vibration in an Axial Compressor

Przysowa

Russhard²

2019

Sensors

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Complex blade responses such as a rotating stall or simultaneous resonances are common in modern engines and their observation can be a challenge even for state-of-the-art tip-timing systems and trained operators. This paper analyses forced vibrations of axial compressor blades, measured during the bench tests of the SO-3 turbojet. In relation to earlier studies conducted in Poland with a small number of sensors, a multichannel tip-timing system let us observe simultaneous responses or higher-order modes. To find possible symptoms of a failure, blade responses in a healthy and unhealthy engine configuration with an inlet blocker were studied. The used analysis methods covered all-blade spectrum and the circumferential fitting of blade deflections to the harmonic oscillator model. The Pearson coefficient of correlation between the measured and predicted tip deflection is calculated to evaluate fitting results. It helps to avoid common operator mistakes and misinterpreting the results. The proposed modal solver can track the vibration frequency and adjust the engine order on the fly. That way, synchronous and asynchronous vibrations are observed and analysed together with an extended variant of least squares. This approach saves a lot of work related to configuring the conventional tip-timing solver.

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Experimental Methods Applied in a Study of Stall Flutter in an Axial Flow Fan

Cited by 5 publications

References 16 publications

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

Analysis on flow separation characteristics of last stage blade in steam turbine under small volume flow condition

Pulsation and Vibration Measurement on Stator Side for Turbocharger Turbine Blade Vibration Monitoring

Non-Contact Measurement of Blade Vibration in an Axial Compressor

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