Computational Methods and Experimental Measurements XV Wit Transactions on Modelling and Simulation
Experimental,Measurements,and ...
Transcript of Experimental,Measurements,and ...
Experimental Measurements and Numerical Simula4ons in a 3-‐Turbine Array of 45:1 Scale DOE RM1 Turbines
Alberto Aliseda!Danny Sale!
Teymour Javaherchi!Nick Stelzenmuller!
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
LABORATORY-SCALE ROTOR GEOMETRY
I Maximize chord-based Reynoldsnumber
I Choose foil to minimize Reynoldsnumber effects
I Match performance and optimum tipspeed ratio with blade-elementmomentum design code
I Attempt to match power extractionand wake characteristics at scale, notgeometry
0.2 0.4 0.6 0.8 10.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2x 10
5
r/R Normalized spanwise coordinate
Chord
−bas
ed R
eynold
s num
ber
U=0.5 m/s
U=0.7 m/s
U=0.9 m/s
U=1.1 m/s
Transition?
Solid lines represent DOE RM 1Dotted lines represent lab−scale rotor
DOE RM 1 Turbine Scaling down process!
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
LABORATORY-SCALE ROTOR GEOMETRY
I Maximize chord-based Reynoldsnumber
I Choose foil to minimize Reynoldsnumber effects
I Match performance and optimum tipspeed ratio with blade-elementmomentum design code
I Attempt to match power extractionand wake characteristics at scale, notgeometry
6 7 8 9 10 110
0.1
0.2
0.3
0.4
0.5
TSR
Eff
icie
ncy
Full−scale DOE RM 1 efficiency(predicted from BEMT)
Lab−scale DOE RM 1 experimental efficiency
Geometrically-scaled DOE RM 1 Turbine Performance!
6 7 8 9 10 110
0.1
0.2
0.3
0.4
0.5
TSR
Eff
icie
ncy
Full−scale DOE RM 1 efficiency(predicted from BEMT)
Lab−scale DOE RM 1 experimental efficiency
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
LABORATORY-SCALE ROTOR GEOMETRY
I Maximize chord-based Reynoldsnumber
I Choose foil to minimize Reynoldsnumber effects
I Match performance and optimum tipspeed ratio with blade-elementmomentum design code
I Attempt to match power extractionand wake characteristics at scale, notgeometry
Performance-scaled !DOE RM 1 Turbine!
DOE RM1 @ 45:1 scale Similarity based on performance curves
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
LABORATORY-SCALE TURBINE45 cm diameter rotor
Experimental CondiAons Rechord ~ 105 Tip Speed Ra4o (TSR) = 4.5-‐8
Blockage Ra4o = 20%
30
Figure 4.1: Photograph of the Bamfield Marine Science Centre flume
4.1.1 Flume dimensions and specifications
The BMSC flume has a width of 2 m, a depth of up to 1 m, and 12.3 m test section
length with full optical access. The pumps that drive the flow are capable of a
volumetric flow rate of approximately 1 m3/s, which results in a freestream flow speed
of 0.5 m/s. This flow speed was judged to be too slow to produce adequate Reynolds
numbers, which are shown to be Re ⇠ 60, 000 at this flow speed in Figure 3.3. To
increase the flow speed, and thus the Reynolds number, a partition was constructed
in the flume, which can be seen in Figure 4.1. This partition halved the flume width
from 2 m to 1 m, doubled the maximum flow speed, and doubled the blockage ratio.
Three Different Array ConfiguraAons 1. Array of two coaxial turbines.
2. Array of three coaxial turbines.
3. Array of three turbines with lateral offset.
Measurement LocaAons: Two Turbines Coaxially Mounted
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
TWO CO-AXIAL TURBINES AT VARIOUS SPACINGS
Performance for Two Coaxial Turbines: Experimental Measurements
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
TWO CO-AXIAL TURBINES PERFORMANCE
5.5 6 6.5 7 7.5 8 8.5 90
0.1
0.2
0.3
0.4
0.5
TSR
Eff
icie
ncy
Performance curves for two co−axially arranged turbinesat various separation distances
Upstream turbine
5D downstream turbine
8D downstream turbine
11D downstream turbine
14D downstream turbine
Performance of Two Coaxial Turbines: Comparison of Experiments and SimulaAons
WHAT IS TIDAL ENERGY? Background Design Experiment Single Turbine Results Array Results
TURBINE ARRAYS: THREE CO-AXIAL TURBINES
Measurement LocaAons: Three Turbines Mounted Coaxially
3-‐Turbine Coaxial Array Performance Comparison of Experiments and SimulaAons
Downstream separaAon 5D
EvoluAon of the available KineAc Energy Flux a 3-‐Turbine Coaxial Array
Downstream separaAon 5D
Evolution of TKE contours in a 3-Turbine Coaxial Array!
Downstream separaAon 5D
3-‐Turbine Offset Array Performance Comparison of Experiments and SimulaAons
3-‐Turbine Offset Array Performance LES SimulaAons
InvesAgaAon of the Flume Blockage Effect
ε = 20 % ε = 10 % ε = 5 % *
• Increase in blockage leads into increase in efficiency (verAcal shi[ of Cp curve).
• Increase in blockage shi[s the peak of efficiency toward higher TSR values
(horizontal shi[ of Cp curve).
Summary and Conclusions!
• Three Turbines Array present non-monotonic performance: third turbine has higher efficiency than middle turbine!
• Confinement plays a increasingly important role for higher number of turbines and lateral offset in the Array.!
• Agreement between experimental and numerical results is best for single turbine and optimum TSR. !
• Angular velocity fluctuations in the experiments, and enhanced wake recovery, not captured by simulations, leads to numerical/experimental divergence with lower TSRs, larger arrays and higher confinement.!
RMS of Normalized Rota4onal Velocity Temporal Evolu4on (TSR = 6.15, 7.16)
Array of Three Turbines with Lateral Offset
• ObservaAon of similar physics compared to results from array of two & three coaxial turbines.
• Downstream turbines’ efficiency increase monotonically with the TSR value.
3-‐Turbine 1/4D Lateral Offset Array Performance
Reynolds-‐number Dependent Performance
5 6 7 8 9 10 11 120.25
0.3
0.35
0.4
0.45
0.5
TSR
Eff
icie
ncy
Single turbine efficiency at various flow speeds, averaged over one minute
0.52 m/s flowspeed0.61 m/s flowspeed0.65 m/s flowspeed0.71 m/s flowspeed0.75 m/s flowspeed0.90 m/s flowspeed
Turbine Comparison for Performance
5 6 7 8 9 10 11 12 130
0.1
0.2
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0.4
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TSR
Eff
icie
ncy
Turbine 1Turbine 2Turbine 3
PIV Velocity Profiles in the Wake turbine
0.4 0.5 0.6 0.7 0.8 0.9 1 1.10
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
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Norm
aliz
ed v
erti
cal
dis
tance
fro
m c
ente
rlin
e
Normalized streamwise velocity
Rotor tip
Free surface
Streamwise velocity profiles for TSR 7
2D up
2D down
3D down
5D down
7D down
Results of BEM study (3/3) Effect of blockage on efficiency
• Blockage increases the efficiency. • Blockage shi[s the peak of efficiency to the right. • Blockage delays the peak of efficiency of the two downstream turbines.
Source : S. J. Miley’s catalog of airfoils
€
α(r)= arctanVinc(r )rω
+ β(r)
Angle of adack :
3-‐Turbine 1/4D Lateral Offset Array Performance
Downstream separaAon 5D