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International Journal of Fluid Mechanics Research
ESCI SJR: 0.206 SNIP: 0.446 CiteScore™: 0.5

ISSN Печать: 2152-5102
ISSN Онлайн: 2152-5110

Выпуски:
Том 46, 2019 Том 45, 2018 Том 44, 2017 Том 43, 2016 Том 42, 2015 Том 41, 2014 Том 40, 2013 Том 39, 2012 Том 38, 2011 Том 37, 2010 Том 36, 2009 Том 35, 2008 Том 34, 2007 Том 33, 2006 Том 32, 2005 Том 31, 2004 Том 30, 2003 Том 29, 2002 Том 28, 2001 Том 27, 2000 Том 26, 1999 Том 25, 1998 Том 24, 1997 Том 23, 1996 Том 22, 1995

International Journal of Fluid Mechanics Research

DOI: 10.1615/InterJFluidMechRes.v37.i5.60
pages 459-469

Effect of Particle Separation and Sand Erosion in a Hydraulic Turbine

Bhola Thapa
Department of Mechanical Engineering, Kathmandu University, Kathmandu, Nepal

Краткое описание

Sand erosion is one of the major operational problems of hydropower plants in the Himalayan Rivers. Size is the main factor responsible for particle transport and erosion. For the particles flowing in the curved path or swirl flow, centrifugal force is caused by tangential component of absolute velocity while drag force is caused by absolute velocity. The equilibrium of these two forces gives critical diameter of the particle which will be rotating in the orbit. Such critical diameter is a function of the drag coefficient, specific gravity of the particle, radius at which the particle is moving and ratio of particle velocity in peripheral direction to the absolute velocity of water. Particles larger than the critical diameter move away from the center of the flow path and thus hit the wall whereas but smaller particles flow along with the water. The swirl flow test rig was designed and developed at Norwegian University of Science and Technology to study the effect of particle separation. This test rig simulates the flow in between guide vane outlet and runner inlet of Francis turbine. The flow of particle in the swirl flow was observed by naked eye and high speed video camera. The value of coefficient of drag from this experiment was found to be in between 0.1 -0.2 and compared well with literature data against particle Reynolds number. In the full opening position, the guide vanes can be fixed from 10 to 40° which creates strong swirl. For the turbine of radius 1m at inlet, sand particles of diameter larger than 2 mm will stay rotating in swirl flow damaging guide vanes positioned around 10°. At higher Reynolds number and drag coefficient 0.1, even small particles of 1 mm size will stay rotating and hitting the guide vane wall. The experimental setup helps to develop operational guidelines for Francis turbine operating with large sand particles. If the particle size in the water is larger than the critical particle size, the turbine should not be operated at low guide vane opening. The experimental observation reveals that smaller turbines are more prone to sand erosion.

ЛИТЕРАТУРА

  1. Thapa, B., Sand Erosion in Hydraulic Machinery.

  2. Chevallier, P. and Vannes, A. B., Effect on a Sheet Surface of an Erosive Particle Jet upon Impact.

  3. Tabakoff, W., Hamed, A., and Metwally, M., Effect of Particle Size Distribution on Particle Dynamics and Blade Erosion in Axial Flow Turbines.

  4. Thapa, B. and Brekke, H., Effect of Sand Particle Size and Surface Curvature in Erosion of Hydraulic Turbine.

  5. Brekke, H., Design and Operation of Medium and High Head Turbines.

  6. Thapa, B. and Skare, P. E., Inspection Report: Fortune Power Plant.

  7. Spurk, J. H., Fluid Mechanics.


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