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CFD Analysis of a Uni-directional Impulse Turbine for Wave Energy Conversion
Title
CFD Analysis of a Uni-directional Impulse Turbine for Wave Energy Conversion.
Creator
Velez, Carlos, Ilie, Marcel, Lin, Kuo-Chi, Qu, Zhihua, University of Central Florida
Abstract / Description
Ocean energy research has grown in popularity in the past decade and has producedvarious designs for wave energy extraction. This thesis focuses on the performance analysis of auni-directional impulse turbine for wave energy conversion. Uni-directional impulse turbines canproduce uni-directional rotation in bi-directional flow, which makes it ideal for wave energyextraction as the motion of ocean waves are inherently bi-directional. This impulse turbine iscurrently in use in four of the world...
Show moreOcean energy research has grown in popularity in the past decade and has producedvarious designs for wave energy extraction. This thesis focuses on the performance analysis of auni-directional impulse turbine for wave energy conversion. Uni-directional impulse turbines canproduce uni-directional rotation in bi-directional flow, which makes it ideal for wave energyextraction as the motion of ocean waves are inherently bi-directional. This impulse turbine iscurrently in use in four of the world's Oscillating Wave Columns (OWC). Current research todate has documented the performance of the turbine but little research has been completed tounderstand the flow physics in the turbine channel. An analytical model and computational fluiddynamic simulations are used with reference to experimental results found in the literature todevelop accurate models of the turbine performance. To carry out the numerical computationsvarious turbulence models are employed and compared. The comparisons indicate that a lowReynolds number Yang-shih K-Epsilon turbulence model is the most computationally efficientwhile providing accurate results. Additionally, analyses of the losses in the turbine are isolatedand documented.Results indicate that large separation regions occur on the turbine blades whichdrastically affect the torque created by the turbine, the location of flow separation is documentedand compared among various flow regimes. The model and simulations show good agreementwith the experimental results and the two proposed solutions enhance the performance of theturbine showing an approximate 10% increase in efficiency based on simulation results.
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Date Issued
2011
Identifier
CFE0004173, ucf:49049
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0004173
Large Eddy Simulations with a Tabulated Conditional Moment Closure Moment Closure Model for Turbulent Premixed Combustion with Heat Loss
Title
Large Eddy Simulations with a Tabulated Conditional Moment Closure Moment Closure Model for Turbulent Premixed Combustion with Heat Loss.
Creator
Velez, Carlos, Vasu Sumathi, Subith, Martin, Scott, Kassab, Alain, Das, Tuhin, University of Central Florida
Abstract / Description
The Tabulated Premixed Conditional Moment Closure (T-PCMC) method has been shown to provide the capability to predict turbulent, premixed methane flames with detailed chemistry and reasonable run times in a RANS/URANS adiabatic environment. Here the premixed T-PCMC method is extended in a Large Eddy Simulation (LES) framework for non-adiabatic premixed flames, allowing heat loss to occur in the mixture before, during and after combustion. It is proposed that the LES framework is a more...
Show moreThe Tabulated Premixed Conditional Moment Closure (T-PCMC) method has been shown to provide the capability to predict turbulent, premixed methane flames with detailed chemistry and reasonable run times in a RANS/URANS adiabatic environment. Here the premixed T-PCMC method is extended in a Large Eddy Simulation (LES) framework for non-adiabatic premixed flames, allowing heat loss to occur in the mixture before, during and after combustion. It is proposed that the LES framework is a more suitable representation for both chemical and turbulent scales in premixed combustion. By resolving the high energy turbulent scales and modeling the small scale turbulence, it is expected that the resolution of the turbulence and transient effects are better captured in a LES framework leading to better predictions of the mixing rate and consequently the reaction rate, which is the main focus and source of error in combustion modeling. The LES T-PCMC model is implemented using the open source CFD software OpenFOAM for its open access to C++ source code and large library of turbulence and thermo-physical models. The proposed model validated with PIV and Raman measurements of a turbulent, enclosed reacting flame of a single jet and backward facing step geometry. The DLR data sets provide both unity (E.g.Methane) and non-unity (E.g. Hydrogen) Lewis number fuels, allowing for the proposed numerical model to be validated against both unity and non-unity Lewis # flames. Velocity, temperature and major/minor species are compared to the experimental data. Once validated, this model is intended to be useful for designing lean premixed combustors for gas turbines which operate primarily in the corrugated premixed combustion regime, where chemical and turbulent time scales are of the same order requiring adequate models for their interaction.LES results match the experimental data better than the Reynolds Averaged Navier-Stokes (RANS/URANS) solution and is able to better resolve the transient features of the flame with an increase in run time of only 50 %, when compared to URANS.
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Date Issued
2015
Identifier
CFE0006234, ucf:51058
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006234