scholarly journals Optimization of Radial Impulse Turbine for Oscillating Water Column Wave Renewable Energy

2019 ◽  
Vol 8 (12) ◽  
pp. 5699-5703
Keyword(s):  
Water Column ◽  
Oscillating Water Column ◽  
Peak Efficiency ◽  
Impulse Turbine ◽  
Trapped Air ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Radial Turbine ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd

An oscillating water column (OWC) extracts the power of waves by trapping air above a water column. This trapped air is compressed and decompressed by the wave action flow inside a turbine power to the mechanical power during process, and it is important as the turbines are expected to operate in oscillating and reversing flows over a wide range of conditions. The objectives of this study are to determine and analyze the type of radial impulse turbine of OWC and to optimize the performance of a radial impulse turbine for OWC by using Computational Fluid Dynamics (CFD). This requires a comprehensive investigation on turbine configuration, turbine efficiency, OWC integration, and turbine operation with respect to climate condition. The outcome of this study to settle the main drawbacks of radial turbine namely lower peak efficiency and damping on OWC can be considered. Later, these problems will be further study to identify the behavior of the airflow through the machine, sources of energy loss, and impact of different parameters on the turbine performance.

scholarly journals Optimal design of air turbines for oscillating water column wave energy systems: A review

2017 ◽  
Vol 8 (1) ◽  
pp. 37-49 ◽  
Author(s):  
Tapas Kumar Das ◽  
Paresh Halder ◽  
Abdus Samad
Keyword(s):  
Water Column ◽  
Wave Energy ◽  
Guide Vane ◽  
Optimization Techniques ◽  
Maximum Efficiency ◽  
Oscillating Water Column ◽  
Peak Efficiency ◽  
Wells Turbine ◽  
Impulse Turbine ◽  
Operating Range

Oscillating water column wave energy harvesting system uses pneumatic power to run a turbine and generate power. Both reaction (mainly Wells turbine) and impulse type turbines are tested in oscillating water column system and the performances are investigated. Reaction turbines are easy to install, and the operating range is narrow and possesses higher peak efficiency. On the contrary, impulse turbines have the wider operating range and lower peak efficiency. Some of the key parameters for Wells turbine are solidity, tip clearance, and the hub-to-tip ratio. Significant performance improvement is possible by redesigning the turbines using optimization techniques. Till date, surrogate modeling and an automated optimization library OPAL are commonly used in optimization of oscillating water column air turbines. In this article, various types of oscillating water column turbines are reviewed, and optimization techniques applied to such turbines are discussed. The Wells turbine with guide vane has the maximum efficiency, whereas the axial-impulse turbine with pitch-controlled guide vane has the widest operating range. Turbines with optimized geometry have better overall performance than other turbines.

An Investigation Into the Non-Linear Effects Resulting From Air Cushions in the Orecon Oscillating Water Column (OWC) Device

2009 ◽  
Author(s):  
Jim L. Lye ◽  
David T. Brown ◽  
Fraser Johnson
Keyword(s):  
Water Column ◽  
Mooring Line ◽  
Oscillating Water Column ◽  
Trapped Air ◽  
Model Scale ◽  
Sea Bed ◽  
Structural Responses ◽  
Linear Effects ◽  
The Waves ◽  
Base Structure

When designing an Oscillating Water Column (OWC) device, the motions and structural responses in waves are of great interest. However, predictions of these motions are complicated by the presence of air chambers above a large proportion of the waterplane area. Modeling the stiffness provided by air cushions at model scale presents a number of problems as air stiffness does not scale according to the laws of Froude scaling. To-date, the closest analogy might be an air-lifted gravity base structure, or crane vessel. However, in an OWC device, the air is not trapped as it is allowed to vent through a turbine. As a result, in still water, none of the mass of the buoy is supported by the air column. However, as the buoy is subjected to waves of increasing height the influence of the air chambers on the motions response becomes more pronounced. Experiments into the behavior of structures with trapped air springs have focused largely on benign sea conditions as the air cushions are generally used in vessels or structures involved with installation operations or similar. In contrast, the behavior of an OWC device must be predicted in all conditions up to, and including, survival conditions. BPP-TECH are providing technical support to the designers of the Orecon MRC wave energy buoy. This buoy uses chambers of varying drafts to generate electricity from the waves. The buoy is tension moored to the sea bed in order to constrain the heave motions to maximize the air pressure within the chambers as waves pass. A series of tank tests were undertaken at the OCEANIDE facility in order to investigate the motions of the buoy while tension moored and also measure the mooring line tensions. This paper will focus on the methods used to represent the air chambers at model scale and will present the results of the tests. A variety of different orifice sizes were used in the test campaign in order to provide a spread of values that would offer an insight into the effect of the air chambers on the motions of the structure in waves.

scholarly journals DEVELOPMENT OF A NUMERICAL MODEL FOR THE STUDY OF AN OSCILLATING WATER COLUMN DEVICE CONSIDERING AN IMPULSE TURBINE

2019 ◽  
Vol 18 (1) ◽  
pp. 99
Author(s):  
A. L. dos Santos ◽  
L. A. Isoldi ◽  
L. A. O. Rocha ◽  
M. N. Gomes ◽  
R. S. Viera ◽  
...  
Keyword(s):  
Numerical Model ◽  
Energy Conversion ◽  
Water Column ◽  
Numerical Study ◽  
Velocity Ratio ◽  
Power Coefficient ◽  
Working Fluid ◽  
Speed Ratio ◽  
Oscillating Water Column ◽  
Impulse Turbine

The present work brings a numerical study of an energy conversion device which takes energy from the waves through an oscillating water column (OWC), considering an impulse turbine with rotation in the chimney region through the implementation of a movable mesh model. More precisely, a turbulent, transient and incompressible air flow is numerically simulated in a two-dimensional domain, which mimics an OWC device chamber. The objectives are the verification of the numerical model with movable mesh of the impulse turbine in the free domain from the comparison with the literature and, later, the study of the impulse turbine inserted in the geometry of the OWC device. In order to perform the numerical simulation on the generated domains, the Finite Volume Method (FVM) is used to solve the mass and momentum conservation equations. For the closure of the turbulence, the URANS (Unsteady Reynolds Averaged Navier-Stokes) model k-ω SST is used. To verify the numerical model employed, drag coefficients, lift, torque and power are obtained and compared with studies in the literature. The simulations are performed considering a flow with a Reynolds number of ReD = 867,000, air as the working fluid and a tip speed ratio of λ = 2. For the verification case, coefficients similar to those previously predicted in the literature were obtained. For the case where the OWC device was inserted it was possible to observe an intensification of the field of velocities in the turbine region, which led to an augmentation in the magnitude of all coefficients investigated (drag, lift, torque and power). For the case studied with the tip velocity ratio λ = 2, results indicated that power coefficient was augmented, indicating that the insertion of the turbine in a closed enclosure can benefit the energy conversion in an OWC device.

PHASE SHIFT METHODOLOGY ASSESSMENT OF AN AUTOMOTIVE MIXED FLOW TURBOCHARGER TURBINE UNDER PULSATING FLOW CONDITIONS

2015 ◽  
Vol 77 (8) ◽  
Author(s):  
M. H. Padzillah ◽  
S. Rajoo ◽  
R. F. Martinez-Botas
Keyword(s):  
Phase Shift ◽  
Flow Velocity ◽  
Combustion Engine ◽  
Bulk Flow ◽  
Phase Shifting ◽  
Power Matching ◽  
Cfd Models ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Computational Fluid Dynamics Cfd

The reciprocating nature of an Internal Combustion Engine (ICE) inevitably results in unsteady flow in the exhaust manifold. In a turbocharged engine, it means that the turbine is subjected to highly pulsating flows at its inlet. The finite time taken by the travelling pressure waves necessitates the need for phase-shifting method before any instantaneous parameter can be analyzed. In a turbocharger test-rig where the instantaneous isentropic power is evaluated upstream of the instantaneous actual power, one of the parameter has to be time-shifted in order to obtain meaningful instantaneous turbine efficiency. This research aims to compare two different methods of phase shifting which are by peak power matching and summation of sonic and bulk flow velocity. In achieving this aim, Computational Fluid Dynamics (CFD) models of full stage turbine operating at 20 Hz, 40 Hz, 60 Hz and 80 Hz have been developed and validated. Instantaneous efficiency was calculated at different locations and the order of calculated efficiency throughout the pulse is analyzed. Results have shown that phase shift using summation of sonic and bulk flow velocity indicated more reasonable efficiency values, thus the method could be used with high confidence for analysis involving unsteady turbine performance.

Prediction of Surface Roughness and Incidence Effects on Turbine Performance

1993 ◽  
Author(s):  
R. J. Boyle
Keyword(s):  
Surface Roughness ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Three Dimensional Flow ◽  
Dimensional Flow ◽  
Turbine Efficiency ◽  
Turbine Performance ◽  
Wide Range ◽  
Loss Models

The use of a Navier-Stokes analysis to predict the change in turbine efficiency resulting from changes in blade surface roughness or incidence flow angles is discussed. The results of a midspan Navier-Stokes analysis are combined with those from a quasi-three-dimensional flow analysis code to predict turbine performance. A quasi-three-dimensional flow analysis code was used to determine turbine performance over a range of incidence flow angles. This analysis was done for a number of incidence loss models. The change in loss due to changes in incidence flows computed from the Navier-Stokes analysis is compared with the results obtained using the empirical loss models. The Navier-Stokes analysis was also used to determine the effects of surface roughness using a mixing length turbulence model, which incorporated the roughness height. The validity of the approach used was verified by comparisons with experimental data for a turbine with both smooth and rough blades tested over a wide range of blade incidence flow angles.

Numerical Simulation of an Oscillating Water Column Problem for Turbine Performance

2018 ◽  
pp. 45-65
Author(s):  
Antonio Moñino ◽  
Encarnación Medina-López ◽  
Rafael J. Bergillos ◽  
María Clavero ◽  
Alistair Borthwick ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Water Column ◽  
Oscillating Water Column ◽  
Turbine Performance

A Tethered Multiple Oscillating Water Column Wave Energy Device: From Concept to Deployment

2002 ◽  
Author(s):  
John Chudley ◽  
Y. Ming Dai ◽  
Fraser Johnson
Keyword(s):  
Engineering Design ◽  
Water Column ◽  
Wave Energy ◽  
Phase Locking ◽  
Wave Climate ◽  
Oscillating Water Column ◽  
Impulse Turbine ◽  
Energy Device ◽  
Local Wave ◽  
The Individual

This paper discusses the research and design methodology employed in the development of a tethered Multiple Oscillating Water Column (MOWC) wave energy device – from concept to deployment. The fundamental aim of the project was the design and deployment of a scaled floating MOWC wave energy device capable of generating physical data from sea trials. The MOWC collector component incorporated oscillating columns connected to a self-rectifying impulse turbine via individual settling chambers. The device has a water draught of 12m and an air draught of 3m. It is of cylindrical design with an overall diameter of 4.4m, displacing 10t The present unit is rated to at 5 kW power output through restrictions of the internal airflows. Research indicates that a full-scale unit 5 times bigger than the scaled device would be capable of generating 500 – 750 kW in a moderately rough sea. The paper addresses the complex problems associated with floating MOWC devices and suggests methods to enable accurate modeling and matching of internal components. Topics discussed include: concept recognition, hydrodynamic motion interaction with OWC, local resource evaluation, turbine selection, power generation and dissipation, moorings, data monitoring, telemetry and performance evaluation. Mathematical simulations and tank testing were used to develop the concept to a stage where an engineering design could be generated. The use of mathematical modelling presented the project with several specific problems that have been highlighted within the paper. Tank testing enabled the project to overcome these difficulties and developed an engineering design tuned to the local wave climate. Initial research has indicated that the combination of individual Oscillating Water Columns (OWC) of different draughts increases the efficiency of this design when compared to a typical single OWC device. Results also indicated that the channeling of individual air masses through a self-rectifying impulse turbine would produce a self-regulated electrical output via phase locking of the individual columns.

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