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Journal ArticleDOI

Identification of Critical Net Positive Suction Head From Noise and Vibration in a Radial Flow Pump for Different Leading Edge Profiles of the Vane

01 Dec 2013-Journal of Fluids Engineering-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 135, Iss: 12, pp 121301
TL;DR: In this paper, experimental investigations concerning cavitation in radial flow pump for three different leading edge profiles of the vane were carried out in an open circuit system and the results revealed that the noise and vibration were better predictors of inception and development of cavitation.
Abstract: Experimental investigations concerning cavitation in radial flow pump for three different leading edge profiles of the vane were carried out in an open circuit system. The operating condition of the radial flow pump under cavitating case was understood by measurement of noise and vibration along with the pump parameters for various speeds and flow rates. The outcome of the experimental results revealed that the noise and vibration were better predictors of inception and development of cavitation. Further observation inferred from critical net positive suction head (NPSH) curve of 3% head drop and critical NPSH value of noise and vibration are presented.
Citations
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Journal ArticleDOI
Dazhuan Wu1, Peng Yan1, Xin Chen1, Peng Wu1, Shuai Yang1 
TL;DR: In this article, the effects of TE modification on the performance and internal flow of a mixed-flow pump are investigated through computational fluid dynamics (CFD) analysis, and the results show that TE modification significantly improves pump efficiency in the high flow rate region by more than 10%.
Abstract: Modern pumps are designed to guarantee a sufficiently large operating range or to satisfy the performance requirements relative to more than one operating point. This study applies trailing-edge (TE) modification method based on TE rounding in the suction surface to widen the operating range of a mixed-flow pump. The effects of TE modification on the performance and internal flow of the mixed-flow pump are investigated through computational fluid dynamics (CFD) analysis. Local Euler head distribution is introduced to reveal the pattern of energy growth along the blade-aligned (BA) streamwise location. A pump model with TE modification is tested, and numerical results agree well with experimental data. The results show that TE modification significantly improves pump efficiency in the high flow rate region by more than 10%. The best pattern of normalized local Euler head distribution (NLEHD) is a convex curve of nearly constant growth rate. The overall heads are also improved, and the flow near the exit of the impeller exhibits better uniformity. This finding demonstrates that a small change in the TE of the impeller can influence flow structure in most areas of impeller channels and that the local Euler head distribution is closely related to pump efficiency. TE modification can effectively improve the performance of the mixed-flow pump with high flow rate.

39 citations

Journal ArticleDOI
TL;DR: An ameliorative algorithm-united algorithm for cavitation vibration analysis is proposed on the basis of short time Fourier transform (STFT) and Wigner-Ville distribution (WVD) as discussed by the authors.
Abstract: Cavitation is a challenging flow abnormality that leads to undesirable effects on the energy performance of the centrifugal pump and the reliable operation of the pump system. The onset and mechanism of a phenomenon that results in unsteady cavitation must be realised to ensure a reliable operation of pumps under the cavitation state. This study focuses on cavitation instability at normal flow rate, at which point the unsteady cavitation occurs as the available net positive suction head (NPSHa) falls below 5.61 m for the researched pump. An ameliorative algorithm–united algorithm for cavitation vibration analysis is proposed on the basis of short time Fourier transform (STFT) and Wigner–Ville distribution (WVD). The STFT–WVD method is then tested using vibration data measured from the centrifugal pump. The relationship between vibration and suction performance indicates that the inception and development of cavitation can be effectively detected by the distribution and intensity of the united algorithm at the testing points. Intermediate frequency components at approximately 6 kHz fluctuate initially with the development of cavitation. A time–frequency characteristic is found to be conducive to monitoring the cavitation performance of centrifugal pumps.

34 citations

Journal ArticleDOI
TL;DR: In this article, the influence of cavitation process on different frequency bands in a centrifugal pump with slope volute was analyzed and it was proved that cavitation has a significant impact on low frequency signals.
Abstract: Cavitation is one of the instability sources in centrifugal pump, which would cause some unexpected results. The goal of this paper was to analyze the influence of cavitation process on different frequency bands in a centrifugal pump with slope volute. And special attention was paid to low frequency signals, which were often filtered in the reported researches. Results show that at noncavitation condition, vibration level is closely related to flow structure interior pump. At partial flow rates, especially low flow rates, vibration level increases rapidly with the onset of rotating stall. At cavitation condition, it is proved that cavitation process has a significant impact on low frequency signals. With cavitation number decreasing, vibration level first rises to a local maximum, then it drops to a local minimum, and finally it rises again. At different flow rates, vibration trends in variable frequency bands differ obviously. Critical point inferred from vibration level is much larger than that from 3% head drop, which indicates that cavitation occurs much earlier than that reflected in head curve. Also, it is noted that high frequency signals almost increase simultaneously with cavitation occurring, which can be used to detect cavitation in centrifugal pump.

33 citations


Cites methods from "Identification of Critical Net Posi..."

  • ...Christopher and Kumaraswamy [6] used noise and vibration signals to identify critical net positive suction head in a radial flow pump....

    [...]

Journal ArticleDOI
TL;DR: In this article , a thorough review of hydraulic pump as turbine cavitation dynamics and influencing parameters is presented, as well as the future research directions for hydraulic pump-as-turbine cavitation.
Abstract: With the increasing adoption of renewable energy sources globally, hydropower contributes significantly to energy generation through various schemes ranging from big to small-scale plants. In small-scale hydropower plants, the preference for reverse-operated pumps (known as pump as turbines or PATs) over small-scale hydroturbines has increased. However, apart from the associated economic advantages, PATs, like any other hydraulic machinery, are not free from common problems such as cavitation. Cavitation is a phenomenon in which air bubbles are formed within the fluid medium due to substantial local pressure drop and their eventual collapse causes material erosion and degrades the overall machine efficiency. Several studies have focused on PAT conventional operating mode, while its reverse mode just begun to gain research interest. Nevertheless, cavitation remains a common problem in PATs at various hydro-sites. Therefore, to analyze PAT cavitation performance and highlight the differences between its two operating modes in terms of their development mechanisms, this article presents a thorough review of PAT cavitation dynamics and influencing parameters, as well as the future research directions. It is found that PAT reverse mode is more prone to cavitation, but more damages would occur in the conventional mode. Nevertheless, modifying the PAT geometric design parameters can considerably improve its cavitation performance. However, this approach has not been sufficiently investigated for PAT reverse operating mode and hence requires further research. Note that the terms “PAT conventional mode,” “PAT pumping mode,” and “pump” are equally used throughout this paper. • Studies on cavitation performance in hydraulic pumps as turbines (PATs) are reviewed. • Both pump and turbine modes are considered in the review. • PATs are found to have gained importance due to their applicability in remote areas. • PAT reverse mode operations require high heads and flows; prone to cavitation. • Geometric design modification is widely used for PAT cavitation performance improvement.

30 citations

Journal ArticleDOI
Jiaxing Lu1, Shouqi Yuan1, Yin Luo1, Jianping Yuan1, Banglun Zhou1, Sun Hui1 
01 Jun 2016
TL;DR: The research reveals the occurrence and development of cavitation in the centrifugal pump which has been confirmed through experiments and numerical simulation, and the typical frequency of pump inlet pressure pulsation could be regarded as around 30 Hz in the severe cavitation conditions.
Abstract: Concerning the development of cavitation in a centrifugal pump, numerical simulations and experimental investigations have been carried out in a closed hydraulic test rig. The internal flow characteristics and pressure pulsation at pump inlet and outlet have been analyzed during the process of cavitation development. The results of the research reveal the occurrence and development of cavitation in the centrifugal pump which has been confirmed through experiments and numerical simulation. The degree of pump cavitation could be monitored through pump inlet and outlet pressure pulsation. Compared with pump outlet pressure pulsation, pump inlet pressure pulsation is more sensitive to the change of cavitation. According to the results of the investigation, the typical frequency of pump inlet pressure pulsation could be regarded as around 30 Hz in the severe cavitation conditions. Meanwhile, the pump head dropped by 0.77% from noncavitation conditions which could be regarded as a symbol of incipient cavitation.

30 citations


Cites background or methods from "Identification of Critical Net Posi..."

  • ...The most common method used to identify the presence of cavitation was based on the observations of the drop in head and 3% head drop from noncavitation was regarded as the critical cavitation.(1) In addition, other techniques for pump fault diagnosis including cavitation monitoring were well established....

    [...]

  • ...Cavitation is one of the most important problems which should be considered in designing and operating a pump, especially when the rotating speed of pump increases.(1) Severe damage could be caused on the surface of flow channels and stability of system could be affected by cavitation....

    [...]

References
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Book
24 Jun 2005
TL;DR: In this article, a theoretical derivation of pump geometry associated with the maximum attainable efficiency at the design point efficiency penalties due to departures from the "optimum" configuration pump performance at off design conditions performance adjustments by modifications and rework of the pump on test.
Abstract: Classification of centrifugal pumps, pump losses theoretical derivation of pump geometry associated with the maximum attainable efficiency at the design point efficiency penalties due to departures from the "optimum" configuration pump performance at off design conditions performance adjustments by modifications and rework of the pump on test.

64 citations

Journal ArticleDOI
TL;DR: In this paper, the start-up of a centrifugal pump is characterized by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed both a the inlet and outlet of the pump.
Abstract: The start-up of rocket engine turbopumps is generally performed only in a few seconds It implies that these pumps reach their nominal operating conditions after only a few rotations During these first rotations of the blades, the flow evolution in the pump is governed by transient phenomena, based mainly on the flow rate and rotation speed evolution These phenomena progressively become negligible when the steady behavior is reached The pump transient behavior induces significant pressure fluctuations which may result in partial flow vaporization, ie cavitation An existing experimental test rig has been updated in the LML laboratory (Lille, France) for the start-ups of a centrifugal pump The study focuses on cavitation induced during the pump start-up Instantaneous measurement of torque, flow rate, inlet and outlet unsteady pressures, and pump rotation velocity enable to characterize the pump behavior during rapid starting periods Three different types of fast start-up behaviors have been identified According to the final operating point, the start-up is characterized either by a single drop of the delivery static pressure, by several low-frequency drops, or by a water hammer phenomenon that can be observed both a the inlet and outlet of the pump A physical analysis is proposed to explain these three different types of transient flow behavior

61 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that there is a discrete frequency tone within the audible noise spectra, which is in strong correlation with development of the cavitation process in the pump.

60 citations

Book
18 Mar 1999
TL;DR: Centrifugal and Rotary Pumps as mentioned in this paper offers both professionals and students a concise reference detailing the design, performance, and principles of operation of the different pumps types defined by the Hydraulic Institute.
Abstract: Centrifugal and Rotary Pumps offers both professionals and students a concise reference detailing the design, performance, and principles of operation of the different pumps types defined by the Hydraulic Institute. From historical background to the latest trends and technological developments, the author focuses on information with real-world prac

60 citations

Book
01 Jan 1991
TL;DR: Generation ofVA phenomena and wear processes failure oriented process signals and measures of VA phenomena diagnostic inference examples of the implementation of diagnostics in industry advance problems of VA diagnostics.
Abstract: Generation of VA phenomena and wear processes failure oriented process signals and measures of VA phenomena diagnostic inference examples of the implementation of diagnostics in industry advance problems of VA diagnostics.

51 citations