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Flows in Complex Systems

Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone

[+] Author and Article Information
Alin Ilie Bosioc

 Center for Advanced Research in Engineering Science, Romanian Academy – Timisoara Branch, Bvd. Mihai, Viteazu 24, RO-300223, Timisoara, Romaniaalin@mh.mec.upt.ro

Romeo Susan-Resiga1

Hydraulic Machinery Department, “Politehnica”  University of Timisoara, Romania, Bvd. Mihai Viteazu 1, RO-300222, Timisoara, Romaniaresiga@mh.mec.upt.ro

Sebastian Muntean

 Center for Advanced Research in Engineering Science, Romanian Academy – Timisoara Branch, Bvd. Mihai Viteazu 24, RO-300223, Timisoara, Romaniaseby@acad-tim.tm.edu.ro

Constantin Tanasa

Research Center for Engineering of Systems with Complex Fluids,  “Politehnica” University of Timisoara, Bvd. Mihai Viteazu 1, RO-300222, Timisoara, Romaniacostel@mh.mec.upt.ro

1

Corresponding author.

J. Fluids Eng 134(8), 081104 (Jul 30, 2012) (11 pages) doi:10.1115/1.4007074 History: Received August 10, 2011; Revised June 14, 2012; Published July 30, 2012; Online July 30, 2012

The variable demand of the energy market requires that hydraulic turbines operate at variable conditions, which includes regimes far from the best efficiency point. The vortex rope developed at partial discharges in the conical diffuser is responsible for large pressure pulsations, runner blades breakdowns and may lead to power swing phenomena. A novel method introduced by Resiga (2006, “Jet Control of the Draft Tube in Francis Turbines at Partial Discharge,” Proceedings of the 23rd IAHR Symposium on Hydraulic Machinery and Systems, Yokohama, Japan, Paper No. F192) injects an axial water jet from the runner crown downstream in the draft tube cone to mitigate the vortex rope and its consequences. A special test rig was developed at “Politehnica” University of Timisoara in order to investigate different flow control techniques. Consequently, a vortex rope similar to the one developed in a Francis turbine cone at 70% partial discharge is generated in the rig’s test section. In order to investigate the new jet control method an auxiliary hydraulic circuit was designed in order to supply the jet. The experimental investigations presented in this paper are concerned with pressure measurements at the wall of the conical diffuser. The pressure fluctuations’ Fourier spectra are analyzed in order to assess how the amplitude and dominating frequency are modified by the water injection. It is shown that the water jet injection significantly reduces both the amplitude and the frequency of pressure fluctuations, while improving the pressure recovery in the conical diffuser.

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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 7

Reconstructed signal against acquired signal for MG0, MG1, MG2, and MG3 levels (left) and equivalent amplitude overlapped with Fourier spectra of pressure signal (right) in the case of swirling flow with vortex rope

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Figure 8

Equivalent amplitudes corresponding to levels from the test section (a) and Strouhal number (b) versus ratio Qjet /Q

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Figure 9

Dimensionless pressure signals for MG0 level for swirling flow with vortex rope (a) and 14% full water injection (b)

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Figure 10

Dimensionless pressure signal decomposition for swirling flow with vortex rope (a) and 14% water injection (b) in the length of the cone

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Figure 11

Pressure pulsations types’ distributions versus control jet discharge

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Figure 6

Pressure recovery coefficient comparison between the swirling flow with vortex rope regime and the full water injection 14% discharge of the main flow at all levels

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Figure 5

Evolution of the pressure recovery coefficient for MG1 (a), MG2 (b), and MG3 (c) levels depending on the Qjet /Q

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Figure 4

The test section with wall flash mounted pressure transducers on the rig (a) and the labels for each level (b)

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Figure 3

The visualization of the cavitating vortex rope from the discharge cone of the test section (a) and with water injection (b)

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Figure 2

The swirl apparatus and cross section with the main elements

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Figure 1

Experimental closed loop test rig installed in the Hydraulic Machinery Laboratory. Sketch of the test rig with the main elements.

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