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- Title
Effects of the blockage ratio due to hydrokinetic turbines for producing energy in irrigation channels.
- Authors
Martínez-Reyes, Javier; Hamed García-Villanueva, Nahún
- Abstract
In this paper, the effect of the blockage ratio generated by the hydrokinetic turbines upon the obtainable hydraulic power in an open channel is analyzed in order to validate part of the theory related to the calculation of the maximum obtainable power by the hydrokinetic turbines, by using porous discs in an experimental open channel. This analysis is supplemented with the study and characterization of the way in which is developed the wake, that is produced downstream, and the experimental results are compared with those of a one-dimensional numerical model. During the development of the experimental study, three different blockage ratios were analyzed, for which the hydraulic variables were kept fixed in the experimental open channel. Under these conditions, in order to characterize the behavior of the flow and obtain the components of the instantaneous velocity an acoustic Doppler velocimeter was utilized; and to measure the hydrodynamic thrust on the discs a load cell was employed. Among the main results it was found that the velocity in the zone of the far wake has a 90% recovery at approximately 12 diameters downstream from the disc. It is noteworthy that, at this distance, the turbulent intensity was 8%, while the mean turbulence intensity in the section of the open channel where the porous discs are located, before its placement, it was 5.7%. The power coefficients obtained for the different blockage ratios show a 59% increase between the lowest blockage ratio B1 = 0.090 and the highest B3 = 0.197. The differences between the power coefficients of the experimental tests and the maximums obtained with the onedimensional theory are 19.45% for the case of B1 = 0.090; 4.13% for B2 = 0.156; and 0.84% for B3 = 0.197. In general, according to the onedimensional theory, using a blockage ratio of around 0.20 the values of the power coefficient are similar to the maximums expected, and using lower values than 0.10, this coefficient falls by around 20% compared with the maximum theoretical coefficient.
- Subjects
TURBINES; SPEED of sound; IRRIGATION; SODIUM channels; CHANNEL flow; TURBULENCE
- Publication
Tecnología y Ciencias del Agua, 2020, Vol 11, Issue 3, p190
- ISSN
0187-8336
- Publication type
Article
- DOI
10.24850/j-tyca-2020-03-06