Observations of oscillatory motion in certain swirling flows

Chanaud, Robert

doi:10.1017/s0022112065000083

Cited by 133 publications

(54 citation statements)

References 13 publications

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“…It also indicates two straight grid lines, whose angles are 0 and 5 , to show the computational boundaries and specify the circumferential location of contour patterns easily. The previously mentioned spiral vortex appears as a low static pressure spot L. There is another low static pressure spot L2 due to another spiral vortex, whose formation mechanism is the same as the spiral vortex reported by Chanaud (1965) and Nishi et al (1982). It can be deduced as being generated in the shear layer on the tube wall in the swirling flow and going into the cavity between the disks.…”

Section: T Kishibe and S Kajisupporting

confidence: 70%

Swirling Flow Field inside a Hollow Turbine Shaftfor an Internal Cooling Air System

Kishibe

Kaji

1998

International Journal of Rotating Machinery

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The swirling flow field in an internal cooling air system in which the fluid passes through an inducer, a hollow turbine shaft, and a cavity between two disks (referred to as a wheel space) is solved using computational fluid dynamics and the pressure fluctuations on the hollow shaft wall surface are measured.The three-dimensional compressible Navier-Stokes equations are adopted and discretized by an implicit TVD scheme. The region of the cooling air system is divided into two computational domains: one from the inducer to the hollow shaft, and the other from the hollow shaft to the wheel space. In the analysis of the former computational domain, the roles of components such as inducer blades are shown. In the analysis of the latter, the existence of a rotating spiral vortex at the place where the swirling flow turns radially outward is shown and its characteristics are described.The main part of the internal cooling air system of a gas turbine is used as an experimental apparatus. Pressure sensors are embedded axially and circumferentially in the hollow turbine shaft to measure unsteady wall pressures. The existence and characteristics of the rotating spiral vortex are confirmed experimentally. The pressure fluctuations due to instability in the rotating wall boundary layer, whose waves propagate both in the positive and negative directions of the shaft rotation, are captured.

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Section: T Kishibe and S Kajisupporting

confidence: 70%

Swirling Flow Field inside a Hollow Turbine Shaftfor an Internal Cooling Air System

Kishibe

Kaji

1998

International Journal of Rotating Machinery

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“…Figure 3a depicts the design of the Slug Flow Expander (SFE). It was similar to models used in previous investigations studying the breakdown of an in-line pipe vortex [12,[17][18][19] and that of other researchers [13,20,21]. The SFE included a tangential inlet tube, cylindrical cavity, end caps, and a downstream tube.…”

Section: Methodsmentioning

confidence: 94%

Naturally-Forced Slug Flow Expander for Application in a Waste-Heat Recovery Cycle

Witt

Hugo

2014

Energies

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This paper investigates a slug-flow expander (SFE) for conversion of high-pressure gas/vapor into kinetic energy of liquid slugs.The energy transfer from high-pressure to kinetic energy is quantified using thrust plate measurements. Non-dimensional thrust data is used to quantify performance by normalizing measured thrust by thrust for the same water flow rate at zero air flow rate. A total of 13 expander configurations are investigated and geometries with the shortest cavity length and the smallest exit diameter are found to result in the largest non-dimensional thrust increase. Results show that thrust augmentation increases with the initiation of slug flow in the SFE. The analysis performed on the normalized thrust readings suggested that as the water and air flow were increased to critical conditions, the liquid slugs produced by the SFE augmented the thrust measurements. The final performance evaluation was based on linear regression of the normalized thrust measurements where slug flow was generated for each SFE architecture. Greater magnitudes of the slope from the linear regression indicated the propensity of the SFE to augment thrust. This analysis confirmed that for the SFE configurations over the range of values investigated, the SFE increased thrust up to three times its original value at no air flow. Given the inherent multiphase nature of the slug-flow expander, application to systems involving expansion of wetting fluids (water as part of a waste-heat recovery system) or air with water droplet formation (as part of a compressed-air energy storage system) could be considered.

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“…The case 'vortex breakdown' is mostly pertinent to the flows in the draft tube. Although earlier studies were done by [17 -20], it was the experimental studies in both air and water [21] that gave a unified descriptive theory for the breakdown as being attributed to the swirling flow.…”

Section: Vortex Breakdown In Swirl Flowsmentioning

confidence: 99%

Tiny bubbles challenge giant turbines: Three Gorges puzzle

Sheng-cai

2015

Interface Focus.

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Since the birth of the first prototype of the modern reaction turbine, cavitation as conjectured by Euler in 1754 always presents as a challenge. Following his theory, the evolution of modern reaction (Francis and Kaplan) turbines has been completed by adding the final piece of the element ‘draft-tube’ that enables turbines to explore water energy at efficiencies of almost 100%. However, during the last two and a half centuries, with increasing unit capacity and specific speed, the problem of cavitation has been manifested and complicated by the draft-tube surges rather than being solved. Particularly, during the last 20 years, the fierce competition in the international market for extremely large turbines with compact design has encouraged the development of giant Francis turbines of 700–1000 MW. The first group (24 units) of such giant turbines of 700 MW each was installed in the Three Gorges project. Immediately after commission, a strange erosion phenomenon appeared on the guide vane of the machines that has puzzled professionals. From a multi-disciplinary analysis, this Three Gorges puzzle could reflect an unknown type of cavitation inception presumably triggered by turbulence production from the boundary-layer streak transitional process. It thus presents a fresh challenge not only to this old turbine industry, but also to the fundamental sciences.

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Observations of oscillatory motion in certain swirling flows

Cited by 133 publications

References 13 publications

Swirling Flow Field inside a Hollow Turbine Shaftfor an Internal Cooling Air System

Swirling Flow Field inside a Hollow Turbine Shaftfor an Internal Cooling Air System

Naturally-Forced Slug Flow Expander for Application in a Waste-Heat Recovery Cycle

Tiny bubbles challenge giant turbines: Three Gorges puzzle

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