The present paper investigates the leading edge (LE) undulations of a Wells turbine blade through numerical analysis. The aspiration for this modification came from humpback whales, which have uneven protrusions at the LE of their pectoral flippers. The flippers help whales to maneuver during swimming. The work is performed by using three-dimensional steady, incompressible Reynolds Averaged Navier-Stokes (RANS) equations with turbulent closer model. The LE of the turbine blades is modified with undulations of three different amplitudes: 1mm, 2.5mm, and 4mm. The results show that the undulation changes the turbine performance. The amplitude 2.5mm gives the peak performance. The comparison between blades with different amplitudes and the reference blade has been discussed throughout this study. © 2018, Turbomachinery Society of Japan. All rights reserved.

Abdus Samad

Department of Ocean Engineering

P. Madhan Kumar

Paresh Halder

Energy harvesting

Hydraulic turbines

Navier Stokes equations

TURBINE COMPONENTS

Turbines

WAVE ENERGY CONVERSION

Peak performance

PROFILE MODIFICATION

Reynolds averaged Navier Stokes (RANS)equations

TURBINE PERFORMANCE

UNDULATED BLADE

Wave energy

WAVE ENERGY HARVESTING

WELLS TURBINE

Turbomachine blades

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Wave Energy Harvesting Turbine: Effect of Hub-To-Tip Profile Modification

International Journal of Fluid Machinery and Systems

The oscillating water column (OWC), which is a wave energy extracting device, uses a bidirectional flow turbine to generate power. The device performance largely depends on the efficiency, torque and operating range of the turbine. The turbine with a larger operating range produces power during a wider wave height and period, both properties changing throughout the year or during each wave cycle. In this article, a numerical work relying on design optimization is reported to show the dependency of power extraction capability to the operating range of the turbine. Reynolds-averaged Navier-Stokes (RANS) equations were solved and a surrogate approximation model was constructed to find an optimal design. Design variables were blade sweep angles at the tip and mid sections. The objective function, to be maximized, is the torque coefficient. The optimal design delayed the flow separation and the peak efficiency dropped by 3.1%. At the same time, the relative power output and the relative stall point were increased by 29% and 18% compared to the reference case, respectively. © 2017 Elsevier Ltd

Renewable Energy

Improved design of a Wells turbine for higher operating range

The present work focuses multi-objective optimization of blade sweep for a Wells turbine. The blade-sweep parameters at the mid and the tip sections are selected as design variables. The peak-torque coefficient and the corresponding efficiency are the objective functions, which are maximized. The numerical analysis has been carried out by solving 3D RANS equations based on k-w SST turbulence model. Nine design points are selected within a design space and the simulations are run. Based on the computational results, surrogate-based weighted average models are constructed and the population based multi-objective evolutionary algorithm gave Pareto optimal solutions. The peak-torque coefficient and the corresponding efficiency are enhanced, and the results are analysed using CFD simulations. Two extreme designs in the Pareto solutions show that the peak-torque-coefficient is increased by 28.28% and the corresponding efficiency is decreased by 13.5%. A detailed flow analysis shows the separation phenomena change the turbine performance. © 2016 Society of Naval Architects of Korea.

Fulltext

International Journal of Naval Architecture and Ocean Engineering

Numerical optimization of wells turbine for wave energy extraction

The performance of an oscillating water column (OWC) wave energy system depends upon several factors including its turbine performance. OWC turbines have inherently low efficiency and low operating range. Through this work, the shape of a Wells turbine was tried to modify to enhance the efficiency and enlarge the operating range. A numerical investigation with steady state flow condition has been reported to change blade thickness from hub to tip. A new concept to combine NACA0015 and NACA0024 at the hub, the midspan and the tip section were developed and the blade was produced through smooth polynomial so that the blade will have different thickness along the span. A commercial code ANSYS-CFX® v14.5 was used for the simulations. The turbulence k-ω SST model was adopted and the reference turbine performances were compared with existing results reported in the literatures. It was found that a blade thinner at midspan gives lesser flow separation, which helps increasing the turbine performance. © 2015 The Authors. Published by Elsevier Ltd.

Procedia Engineering

Wave energy harvesting turbine: Performance enhancement

Delaying a stall improves the performance of any turbomachinery system. TC (tip clearance), which is used in a bi-directional flow Wells turbine of an ocean wave energy device, changes the flow pattern on the turbine blade suction surface, while changing or modifying the TC zone can help obtaining a delayed stall. In the present work, a new tip grooving scheme is introduced and the performance is compared for different tip groove depths and TCs of a Wells turbine. The performance is defined in terms of wider operating range or stall delay, power production and efficiency. The problem was solved by a numerical analysis technique. A multi-block meshing scheme was employed to generate structured and hexahedral elements in the computational domain and the flow was solved in ANSYS CFX® v14.5 by solving Reynolds-averaged Navier Stokes equations. It was found that the grooves improve the turbine operating range and power production as compared to those of the turbine without a groove. The groove depth of 3% of the chord length produced highest power and widest operating range. Using the circumferential groove, 26% increase in turbine power output for a particular operating point is achieved. © 2015 Elsevier Ltd.

Energy

High performance ocean energy harvesting turbine design-A new casing treatment scheme

Wells Turbine for Wave Energy Conversion : Effect of Trailing Edge Shape

Wave energy harvesting turbine: Effect of hub-to-tip profile modification

Journal	International Journal of Fluid Machinery and Systems
Publisher	Turbomachinery Society of Japan
Open Access	No