Case Study of Pump Failure Due to Rotor‐Stator Interaction

Ohashi, Hideo

doi:10.1155/s1023621x94000059

Cited by 40 publications

(16 citation statements)

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“…One of the main outputs of the modal analysis is the Frequency Response Function (FRF), which is the relationship between the response of the structure (in terms of vibration) and the dynamic force. This is particularly important when analyzing the dynamic response of the structure due to an exciting force with a frequency content close to one of the natural frequencies of the structure, since the response of the structure can be determined with precision and therefore resonance or fatigue problems, which have caused several failures in the past [5,6], could be avoided.…”

Section: Introductionmentioning

confidence: 99%

Accurate Determination of the Frequency Response Function of Submerged and Confined Structures by Using PZT-Patches†

Presas

Valentín

Valero

et al. 2017

Sensors

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To accurately determine the dynamic response of a structure is of relevant interest in many engineering applications. Particularly, it is of paramount importance to determine the Frequency Response Function (FRF) for structures subjected to dynamic loads in order to avoid resonance and fatigue problems that can drastically reduce their useful life. One challenging case is the experimental determination of the FRF of submerged and confined structures, such as hydraulic turbines, which are greatly affected by dynamic problems as reported in many cases in the past. The utilization of classical and calibrated exciters such as instrumented hammers or shakers to determine the FRF in such structures can be very complex due to the confinement of the structure and because their use can disturb the boundary conditions affecting the experimental results. For such cases, Piezoelectric Patches (PZTs), which are very light, thin and small, could be a very good option. Nevertheless, the main drawback of these exciters is that the calibration as dynamic force transducers (relationship voltage/force) has not been successfully obtained in the past. Therefore, in this paper, a method to accurately determine the FRF of submerged and confined structures by using PZTs is developed and validated. The method consists of experimentally determining some characteristic parameters that define the FRF, with an uncalibrated PZT exciting the structure. These parameters, which have been experimentally determined, are then introduced in a validated numerical model of the tested structure. In this way, the FRF of the structure can be estimated with good accuracy. With respect to previous studies, where only the natural frequencies and mode shapes were considered, this paper discuss and experimentally proves the best excitation characteristic to obtain also the damping ratios and proposes a procedure to fully determine the FRF. The method proposed here has been validated for the structure vibrating in air comparing the FRF experimentally obtained with a calibrated exciter (impact Hammer) and the FRF obtained with the described method. Finally, the same methodology has been applied for the structure submerged and close to a rigid wall, where it is extremely important to not modify the boundary conditions for an accurate determination of the FRF. As experimentally shown in this paper, in such cases, the use of PZTs combined with the proposed methodology gives much more accurate estimations of the FRF than other calibrated exciters typically used for the same purpose. Therefore, the validated methodology proposed in this paper can be used to obtain the FRF of a generic submerged and confined structure, without a previous calibration of the PZT.

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Section: Introductionmentioning

confidence: 99%

Accurate Determination of the Frequency Response Function of Submerged and Confined Structures by Using PZT-Patches†

Presas

Valentín

Valero

et al. 2017

Sensors

View full text Add to dashboard Cite

show abstract

“…If resonance occurs, damage can appear in the impeller and in fact, damage in this type of impellers was reported by several authors [1][2][3]. To avoid this kind of problem, it is of paramount importance to have an accurate understanding of the dynamic response of the impeller, especially when it is submerged in water.…”

Section: Introductionmentioning

confidence: 99%

Analysis of the dynamic response of pump-turbine impellers. Influence of the rotor

Egusquiza

Valero

Presas

et al. 2016

Mechanical Systems and Signal Processing

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a b s t r a c tThis paper deals with the dynamic response of pump-turbine impellers. A pump-turbine impeller is a complex structure attached to a rotor and rotating inside a casing full of water with very small clearances between the rotating and the stationary parts. The dynamic response of this type of structures is very complex and it is very much affected by the connection to the rotor as well as by the added mass and boundary conditions. As a consequence its calculation presents several uncertainties.First, the dynamic response of pump-turbine impellers is introduced. Second an experimental investigation in a real impeller attached to the rotor and inside the machine was carried out. For this investigation, the impeller of an existing pump-turbine unit with an installed power of 110 MW and a diameter of 2.87 m was studied. For a better analysis of the experimental results a numerical model using FEM was also built-up. Frequencies and mode-shapes were identified numerically and experimentally and the characteristics of the structural response analyzed.To determine the influence of the rotor and supporting structures on the impeller response the results were compared with the ones obtained with the same impeller but suspended (non-connected to the rotor). Experimental and numerical simulation were also used for this case. The changes in the dynamic response due to the rotor connection were determined.Finally the results obtained are compared with the results from other pump-turbine impellers of different designs and general conclusions about the dynamics of this type of structures are given.

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“…If same fluid force is generated when any of the blades of the impeller interacts with any of the vanes, it is well known that resonance is excited only when the next condition is satisfied (20) - (22) .…”

Section: Impeller Vibrationmentioning

confidence: 99%

“…Engineers know that fatigue failure of impellers in centrifugal compressors, blowers, and fans is a serious problem and need to be treated carefully (18), (19) , however, that of the impellers in centrifugal pumps has long been considered as a trivial problem since pump impellers have much large rigidity. With the increasing requirements for high speed, light weight and large capacity, fatigue failure problems in centrifugal pumps have become an important design aspect in many cases (20) , such as cooling pumps for power plants, large capacity pumps in pump stations, pump-turbines, etc. Nagafuji et al (21) studied the vibration of a rotating bladed disk interacting with nozzles located in the stationary side surrounding the disk.…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigations on Pressure Fluctuations and Vibration of the Impeller in a Centrifugal Pump with Vaned Diffusers

Guo

Maruta

2005

JSME international journal. Ser. B, Fluids and thermal engineer

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The pressure fluctuations acting on the impeller and the impeller vibration excited by the fluctuations were investigated in a centrifugal pump with several vaned diffusers. Firstly, the pressures both acting on the impeller and in the volute were measured simultaneously. It was demonstrated that both the volute static pressure and the pressure fluctuations on the impeller are uneven circumferentially (not uniform) under off-design operating conditions. At high flow rates, the pressure fluctuations are large in the front of the volute exit, where the static pressure is low. Secondly, the impeller vibration excited by the fluctuations was measured. It was found that resonance can be excited even when the resonance condition of rotor-stator interaction is not satisfied and sidebands occur in frequency spectra because of the circumferential unevenness of the fluctuations. Resonance can also be excited when a natural frequency of the impeller coincides with the frequencies of sidebands. Furthermore, the vibration wave is a traveling wave in the circumferential direction when resonance of a nodal diameter mode is excited, and the resonant frequency may depend on the traveling direction of the wave due to the inertia effect (added mass) of water.

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Case Study of Pump Failure Due to Rotor‐Stator Interaction

Cited by 40 publications

References 0 publications

Accurate Determination of the Frequency Response Function of Submerged and Confined Structures by Using PZT-Patches†

Accurate Determination of the Frequency Response Function of Submerged and Confined Structures by Using PZT-Patches†

Analysis of the dynamic response of pump-turbine impellers. Influence of the rotor

Experimental Investigations on Pressure Fluctuations and Vibration of the Impeller in a Centrifugal Pump with Vaned Diffusers

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