Effect of overlapping and space between stages of a three-bladed double-stage Savonius hydrokinetic turbine for low flow speed perennial river application

ABSTRACT

Savonius-like hydrokinetic turbine (SAHT) in low-speed flow streams of perennial rivers is not much explored. In this paper, a triple-bladed double-stage SAHT is designed, and its performance is investigated for low flow speeds within 0.45–0.65 m/s under the effect of blade overlapping (within 10–20% in each stage), turbine diameter (within 208–234 mm), and without and with space between the stages (5.0 mm) at different operating speed ratios. Different combinations of design and operating input parameters are studied to obtain a reliable assessment of SAHT performance. After analyzing the results, the best conditions of input parameters and output performance parameters are reported in their nondimensional forms for future use of the obtained results. The torque produced by the turbine increased with the applied brake load, leading to its maximum value at the highest brake load 0.83 times the maximum load. The highest coefficient of performance is obtained as 0.086 at a space 0.25 times the maximum space (i.e. 20 mm), overlapping 15%, brake load 0.83 times the maximum load, tip speed ratio 0.276. And for this, the corresponding power 0.85 times the maximum power (i.e. 0.201 W) at free-stream flow speed of 0.85 times the maximum flow speed (i.e. 0.65 m/s) is obtained. The present turbine with space and overlapping exhibits better performance than some available SAHT designs of single/double stage, two-blade/multi-blade with/without overlap configurations. The novelty of the work is that an improved SAHT has been developed for low-flow speed perennial river applications in the band of low tip speed ratios by combining design conditions like double-stage, space between stages, and overlapping.

KEYWORDS:

• Savonius-alike hydrokinetic turbine
• brake loads
• coefficient of performance
• flow speed
• overlapping
• space between stages

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Notes on contributors

Kanak Chandra Sarma

Kanak Chandra Sarma did his B.E. in Mechanical Engineering from Jorhat Engineering College in 1996, M.Tech in Thermal Engineering from NIT Silchar in 2013, and pursuing PhD in Mechanical Engineering from NIT Silchar since 2015.

Agnimitra Biswas

Dr. Agnimitra Biswas did his B.E. in Mechanical Engineering from Regional Engineering College Silchar in 2001,M.Tech in Thermal Engineering from NIT Silchar in 2007, and PhD in Mechanical Engineering from NIT Silchar in 2010.His research area was Vertical Axis Wind Turbines using experimental and computational methods. He has more than 13 years of teaching and research experiences. Presently he is working as an Associate Professor in ME Department, NIT Silchar since August 2022.

Biswajit Nath

Biswajit Nath did his B.E. in Mechanical Engineering from Anna University Chennai in 2012,M.Tech in Thermal Engineering from Karunya Institute of technology and Sciences Coimbatore in 2020, and pursuing PhD in Mechanical Engineering from NIT Silchar since 2021.

Rahul Dev Misra

Professor Rahul Dev Misra received his B.E. in Mechanical Engineering from Jorhat Engineering College under Dibrugarh University in 1991, M.Tech. in Energy Studies from Indian Institute of Technology Delhi in 1996, and Ph. D. in Thermal Engineering from Indian Institute of Technology Roorkee in 2004.He has served NIT Silchar as Lecturer from 1992 to 2004, as Assistant /Associate Professor from 2004 to 2010, as Professor from 2010 to 2018 and as Professor (HAG) from 2018 till date.