Efficacy of ancillary fluid injection technique for mitigation of vortex rope in hydraulic turbines: A review

Current work is devoted to experimental investigations of behavior of precessing vortex rope in a draft tube model of hydraulic turbine. We used combination of stationary and freely rotating swirlers as a hydro turbine model. Such construction provides velocity distribution on the draft tube inlet close to distribution in natural hydraulic turbines operated at non-optimal conditions. The phenomenon of precessing vortex rope reconnection with further formation of vortex ring was founded in this experimental research using high-speed visualization technique. Synchronization of highspeed visualization and pressure measurements allowed us to relate pressure shock on the draft tube wall with vortex ring moving along wall.

Download Full-text

Flow-Feedback Method for Mitigating the Vortex Rope in Decelerated Swirling Flows

Journal of Fluids Engineering ◽

10.1115/1.4023946 ◽

2013 ◽

Vol 135 (6) ◽

Cited By ~ 21

Author(s):

Constantin Tănasă ◽

Romeo Susan-Resiga ◽

Sebastian Muntean ◽

Alin Ilie Bosioc

Keyword(s):

Swirling Flow ◽

Flow Instability ◽

Pressure Fluctuations ◽

Water Injection ◽

Operating Regime ◽

Experimental Investigations ◽

Vortex Rope ◽

Practical Applications ◽

Wall Pressure Fluctuations ◽

Hydraulic Turbines

When reaction hydraulic turbines are operated far from the design operating regime, particularly at partial discharge, swirling flow instability is developed downstream of the runner, in the discharge cone, with a precessing helical vortex and its associated severe pressure fluctuations. Bosioc et al. (2012, “Unsteady Pressure Analysis of a Swirling Flow With Vortex Rope and Axial Water Injection in a Discharge Cone,” ASME J. Fluids Eng., 134(8), p. 081104) showed that this instability can be successfully mitigated by injecting a water jet along the axis. However, the jet discharge is too large to be supplied with high pressure water bypassing the runner, since this discharge is associated with the volumetric loss. In the present paper we demonstrate that the control jet injected at the inlet of the conical diffuser can actually be supplied with water collected from the discharge cone outlet, thus introducing a new concept of flow feedback. In this case, the jet is driven by the pressure difference between the cone wall, where the feedback spiral case is located, and the pressure at the jet nozzle outlet. In order to reach the required threshold value of the jet discharge, we also introduce ejector pumps to partially compensate for the hydraulic losses in the return pipes. Extensive experimental investigations show that the wall pressure fluctuations are successfully mitigated when the jet reaches 12% of the main flow discharge for a typical part load turbine operating regime. About 10% of the jet discharge is supplied by the plain flow feedback, and only 2% boost is insured by the ejector pumps. As a result, this new approach paves the way towards practical applications in real hydraulic turbines.

Download Full-text

Gas- and Fluid-Injection Technique

Specialized Injection Molding Techniques ◽

10.1016/b978-0-323-34100-4.00003-1 ◽

2016 ◽

pp. 107-164

Author(s):

Hans-Peter Heim

Keyword(s):

Fluid Injection ◽

Injection Technique

Download Full-text

EFFECT OF BRINE‐GAS MIXTURE ON VELOCITY IN AN UNCONSOLIDATED SAND RESERVOIR

Geophysics ◽

10.1190/1.1440670 ◽

1976 ◽

Vol 41 (5) ◽

pp. 882-894 ◽

Cited By ~ 191

Author(s):

S. N. Domenico

Keyword(s):

Uniform Distribution ◽

Wave Velocity ◽

Pore Space ◽

Compressional Wave ◽

Fluid Injection ◽

Injection Technique ◽

Compressional Wave Velocity ◽

Modified Technique ◽

Uniform Size ◽

Unconsolidated Sand

Gas in an unconsolidated sand reservoir encased in shale often results in a dramatic increase in amplitude of the seismic reflection from the shale/gas‐sand interface. Unfortunately, reflection amplitude appears not to vary linearly with water (brine) saturation, and thus cannot be used to estimate gas quantity. Previously presented theoretical velocity computations, for a Tertiary sedimentary section, which demonstrate that compressional‐wave velocity in an unconsolidated gas sand varies nonlinearly with brine saturation, qualitatively agree with laboratory velocity measurements on a sand specimen composed of pure quartz grains. However, significant departure of measured and theoretical velocities at high brine saturation indicates that the technique for partially saturating the sand specimen by flowing a gas‐brine mixture through the specimen does not provide a sufficiently uniform distribution. The gas preferentially seeks larger pores. In a subsequent experiment on a specimen composed of spherical glass beads of nearly uniform size, the previous, as well as a modified, fluid injection technique was used. For the latter, brine only was injected into the pore space previously filled with a mixture of gas and brine in nearly equal proportions. This resulted in a more uniform distribution of the gas‐brine mixture. For approximately equal brine saturations, this modified technique resulted in a measured compressional‐wave velocity approximately one‐half of the velocity measured for the previously used fluid injection technique. This result implies that if the gas‐brine mixture is uniformly distributed in a reservoir, the fluid compressibility is the weighted‐by‐volume average of the constituent compressibilities.

Download Full-text

Application of Computer Graphics Flow Visualization Methods in Vortex Rope Investigations

Energies ◽

10.3390/en14030623 ◽

2021 ◽

Vol 14 (3) ◽

pp. 623

Author(s):

Ondřej Urban ◽

Michaela Kurková ◽

Pavel Rudolf

Keyword(s):

Computer Graphics ◽

Three Dimensional ◽

Cfd Simulations ◽

Vortex Rope ◽

Eddy Simulation ◽

Resultant Data ◽

Computational Fluid Dynamics Cfd ◽

Hydraulic Turbines ◽

Visualization Techniques ◽

Backflow Zone

Computer graphics visualization techniques for application on data from Computational Fluid Dynamics (CFD) simulations of the vortex rope, a phenomenon present in hydraulic turbines operating in off-design conditions, were devised. This included not only objects for visualization (what to visualize) but also methods of the visualization itself (how to do it). By means of advanced methods based particularly on volume rendering of Eulerian fields in combination with Lagrangian objects, various phenomena were captured, such as the motion of the vortex rope or the backflow zone. The data came from simulations using a scale-resolving hybrid turbulence model, the Stress-Blended Eddy Simulation. In such detailed simulations and other applications involving complex three-dimensional structures, proper visualization methods are needed to leverage the content captured in the resultant data.

Download Full-text