الفهرس 
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Abstract
The negative implications of indiscriminate usage of fossil fuels lead to
many problems such as change the global climate. Wind energy is a
promising clean energy and it is a nonpolluting power generation method.
Wind turbines are renewable energy devices but are fraught with challenges
of low wind speeds and high turbulence intensity. In the populated regions the
natural wind speed is considered unreliable source to construct wind farms. A
promising idea is to exploit the rushed air emanated from an artificial
resource. One of these sources is air sucked and rushed out using electrical fan
that is used for ventilation purposes in commercial buildings.
In the present work, the study is introduced through trapping 3 blades of
Darrieus turbine between a flanged diffuser. The aim of the present work is to
enhance the aerodynamic performance of Darrieus turbine with non-impacting
on noise generation through a numerical prediction scheme for noise.
ANSYS- FLUENT 15.0 software is used for the numerical simulations. The
CFD procedures are achieved using two dimensional Unsteady “Reynolds
Averaged Navier Stokes equations” (URANS) with SIMPLE-Algorithm for
(P-V) Pressure-Velocity. 20 boundary layers with growth rate 1.2 from the
wall surface of the turbine blades to the viscous sub-layer and retaining the
maximum value of Y+<1. The height of the first layer in the normal direction
was found to be 1.5 m. wind speed is constant, equals to 8m/s through
the calculations and Reynolds number Re, is 2.168×
.
The numerical model is validated against experimental and numerical
published data. The optimum diffuser configuration is utilized to investigate
the effect of the conventional of NACA 0015, DU 06-W-200 and S1046
profiles on the performance as well as non-conventional J-shape design. The
previous step will be repeated one more time without wind lens (open
turbine). Three tip speed ratios (λ=1.3, 1.6 and 1.7), four different
configurations for each aerofoils type and four microphones locations are
studied and analyzed.
The aerodynamic analysis showed that location 1 (X/D=-0.3) is optimum
location of the diffuser on x-axis with respect to the turbine position. The
highest enhancement in power augmentation was by a factor of 2.24 obtained
from modified J-shape NACA0015 aerofoil enclosed by the flanged diffuser.
The results also revealed that the static torque coefficient for J-shape of
NACA 0015 with diffuser only has the best self-start capability by 1.70 times
the static torque coefficient obtained from conventional shape of NACA 0015
with diffuser along 360º of azimuth angle. Other effective parameters such as
flange height and solidity are investigated. It is concluded that the new Jshape profile is totally collapsed in front of the low solidity.
The aeroacoustics analogies showed that the modified J-shaped profile
without diffuser for all mentioned aerofoils types have the least noise intensity
than the rest of the other designs. It is noticed that the wind lens effect has
dramatically enhanced the performance of generated power, but it is much
noisy than the bare ones. The modified J-shaped profile is promising from
performance and aeroacoutics point of view under restricted working
conditions such as high solidity and low to moderate tip speed ratios for
Darrieus turbine. The most efficient suggested configuration to be installed
above electric fan that is used to discharge the air out of the building was
conventional DU06-W-200 aerofoil enclosed by flanged diffuser. The amount
of energy recovered per year obtained from it was 10.66 Mw.hr. operating
about 16 hr. daily. This system promotes the sustainability, energy
conservations and green technologies.