Abstract
A typical dynamic characteristic of horizontal axis wind turbine shows
up under yaw condition. Prediction accuracy is low for momentum-blade
element theory and related engineering prediction model. In order to
improve the prediction accuracy of dynamic load characteristics, the
whole wind turbine models, based on the experiment about MEXICO (model
experiments in controlled conditions) rotor in 2006, are established by
three-dimensional software called Pro/E. under different yaw conditions,
i.e. yaw angle of 0, 15, 30 and 45 degree. ICEM CFD (integrated
computer engineering and manufacturing code for computational fluid
dynamics) is applied to grid division. The rotating domain containing
rotor part is meshed into hexahedral grids, and the static domain
containing part of wheel hub, tower and outflow field is meshed into
tetrahedral grids. When the grid size of the first layer of blade
surface is set as 5×10-6 m to ensure the first dimensionless size near
the wall Y+<0.5 on the wall, the 2 numbers of grids are determined by
the error of axial load on the airfoil in the 60% section of blades,
which respectively are 6 572 451 and 2 961 385. The aerodynamic
performance of models under rated condition is simulated by ANSYS CFX
with the turbulence model of SST (shear stress transport), high
resolution is chosen as advection scheme, and transient rotor stator as
the domain interface method. The results are converted into data,
processed and analyzed by MATLAB. Finally the following conclusions are
drawn. The distributions of pressure coefficients along the airfoil
chord in different blade sections calculated by CFD method are in good
agreement with the experimental measurements, and the error on the
suction surface of airfoil is mainly caused by stall separation
occurring on the pressure surface of airfoil. With the increasing of yaw
angle, the pressure coefficients of the suction side are increasing and
the location of minimum pressure coefficient moves to airfoil trailing
edge slightly. For the pressure side, the pressure coefficients increase
at first and then decrease, and the location of maximum pressure
coefficient moves to airfoil leading edge slightly. The axial load
coefficients and tangential load coefficients of blades first decrease
and then increase and then decrease again with the increase of the
azimuthal angle. With the increase of the yaw angle, the axial and
tangential load coefficients are both reduced. When the yaw angle is
within 30°, the relative error of axial load coefficients is in the
range of ±5% and the relative error of tangential load coefficients is
in the range of ±15%. CFD method is higher than BEM (blade element
momentum) method in forecasting accuracy of dynamic load calculation.
Under yaw condition, the hysteresis characteristic of airfoil lift and
drag in blade root is more remarkable than blade tip, while the
variation range of the angle of attack in blade root is much less than
that in blade tip. This characteristic must be considered when BEM
method is used to predict wind turbine performance. For axial inflow
condition, CFD method can well predict the average speed, but restricted
by turbulence model and the wake model, CFD calculation did not show
the velocity characteristics of rotating vortex shedding from wind
turbine impeller under yaw condition. The study provides a data support
to build up the forecast model on the engineering and provides the basis
for wind turbine design under yaw condition.
Original language | Chinese |
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Journal | Nongye Gongcheng Xuebao |
Volume | 31 |
Issue number | 16 |
Pages (from-to) | 78-85 |
Number of pages | 8 |
ISSN | 1002-6819 |
DOIs | |
Publication status | Published - 2015 |
Keywords
- Mechanical Engineering
- Agricultural and Biological Sciences (all)
- Computational fluid dynamics
- Dynamic stall
- Models
- Numerical analysis
- The velocity distribution
- The yaw angle
- Wind turbines
- Advection
- Aerodynamic stalling
- Aerodynamics
- Airfoils
- Angle of attack
- Axial loads
- Boundary element method
- Computation theory
- Computer integrated manufacturing
- Dynamic loads
- Electric power transmission networks
- Errors
- Fluid dynamics
- Forecasting
- MATLAB
- Shear stress
- Turbulence models
- Vortex flow
- Aero-dynamic performance
- Blade-element momentums
- Dynamic characteristics
- Dynamic stalls
- Horizontal axis wind turbines
- Hysteresis characteristics
- Shear-stress transport
- Yaw angles