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CFD modelling of the performance of various wind turbine rotors with experimental verification
Author(s)
Barnard, Daniel Rudolph
Date Issued
2021
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
The Blade Element Momentum Method (BEMM) is often used in the initial design of horizontal
axis wind turbine (HAWT) rotors. The BEMM has many simplifying assumptions and
limitations, therefore simulation and testing are essential for a successful design. Climate
change concerns and the depletion of fossil fuels have created a global imperative for
increased use of renewable energy. An important source of renewable energy is wind which
is mostly harvested by means of large HAWTs.
This research was focussed on performance comparison of two, almost identical, small HAWT
rotors. The first rotor was designed using the conventional BEMM. The second was designed
using an adapted BEMM which is currently under research at Cape Peninsula University of
Technology (CPUT). A particular area of interest was the performance of HAWT rotors at low
(off-design) wind speeds. Performance comparison of these two rotors by simulation and
physical testing at half the design wind speed was the central objective of this research.
Research included the creation of solid models for Computational Fluid Dynamics (CFD)
simulation and manufacturing of the conventional and Adapted (ADP) rotors for physical
testing. The vehicle-top mounted test rig and instrumentation were built for physical testing to
capture the power output of the rotors. Flow through the rotors and rotor power output were
analysed using ANSYS Fluent software. CFD simulation results and physical test result were
interpreted and compared. Procedures for the solid modelling and the CFD analysis formed
part of the output of this research.
Simulation predicted a 1.06 % increase and physical test results revealed a 6.06 % increase
of peak performance for the ADP rotor. Physical results had lower power output than the
simulation results due to losses present during field testing. The power output and power
coefficient curves of the simulation and field test were compared for each rotor. An unexpected
outcome from physical test results was that the ADP rotor power peak occurred at a
significantly higher rotational speed than the power peak of the standard (STD) rotor due to
the ADP rotor’s design change. The field tests produced lower measured power output
compared to the CFD predicted power output which was likely due to the oversized generator.
Although we were not able to accurately measure the absolute power, we were still able to
make use of the relative electrical power output to make the comparison between the ADP
and Standard (STD) rotor characteristics.
Simulation and physical results confirmed that the ADP rotor outperformed the STD rotor at
peak performance rotational speed. It is recommended that the ADP design approach be
considered for rotors that have a hub ratio in the region of 20 %. Further recommendations were also made for solid modelling, simulation, the vehicle-top mounted test rig and aspects
of the methodology.
axis wind turbine (HAWT) rotors. The BEMM has many simplifying assumptions and
limitations, therefore simulation and testing are essential for a successful design. Climate
change concerns and the depletion of fossil fuels have created a global imperative for
increased use of renewable energy. An important source of renewable energy is wind which
is mostly harvested by means of large HAWTs.
This research was focussed on performance comparison of two, almost identical, small HAWT
rotors. The first rotor was designed using the conventional BEMM. The second was designed
using an adapted BEMM which is currently under research at Cape Peninsula University of
Technology (CPUT). A particular area of interest was the performance of HAWT rotors at low
(off-design) wind speeds. Performance comparison of these two rotors by simulation and
physical testing at half the design wind speed was the central objective of this research.
Research included the creation of solid models for Computational Fluid Dynamics (CFD)
simulation and manufacturing of the conventional and Adapted (ADP) rotors for physical
testing. The vehicle-top mounted test rig and instrumentation were built for physical testing to
capture the power output of the rotors. Flow through the rotors and rotor power output were
analysed using ANSYS Fluent software. CFD simulation results and physical test result were
interpreted and compared. Procedures for the solid modelling and the CFD analysis formed
part of the output of this research.
Simulation predicted a 1.06 % increase and physical test results revealed a 6.06 % increase
of peak performance for the ADP rotor. Physical results had lower power output than the
simulation results due to losses present during field testing. The power output and power
coefficient curves of the simulation and field test were compared for each rotor. An unexpected
outcome from physical test results was that the ADP rotor power peak occurred at a
significantly higher rotational speed than the power peak of the standard (STD) rotor due to
the ADP rotor’s design change. The field tests produced lower measured power output
compared to the CFD predicted power output which was likely due to the oversized generator.
Although we were not able to accurately measure the absolute power, we were still able to
make use of the relative electrical power output to make the comparison between the ADP
and Standard (STD) rotor characteristics.
Simulation and physical results confirmed that the ADP rotor outperformed the STD rotor at
peak performance rotational speed. It is recommended that the ADP design approach be
considered for rotors that have a hub ratio in the region of 20 %. Further recommendations were also made for solid modelling, simulation, the vehicle-top mounted test rig and aspects
of the methodology.
Additional information
Thesis (MEng (Mechanical Engineering))--Cape Peninsula University of Technology, 2021
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