FACULTY OF ENGINEERING
Design of a small hydro Kaplan turbine with a self-sealing rotor S. Annerel, J. Vierendeels, E. Dick Ghent University Belgium
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Overview • • • • •
Motivation and initial design Sealing rotor Rotor flow analysis Diffuser flow analysis Off-design performance
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Motivation • Turbine that can cope with flow rate variation from design flow rate to zero flow rate • Needs movable rotor that allows complete sealing • Like variable opening valve with extraction of power • Complete flexibility in flow rate • 6 locations on river Sambre in Belgium Flow rate: 5.5 m3/s to 20 m3/s Head: 4.40 m to 1.70 m
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Initial design
Head (m)
3.60
Flow Rate (m³/s)
16.0
Outer diameter (m)
2.00
Inner diameter (m)
0.80
Rotational speed (rpm)
130
Number of blades
12
Lenght diffuser (m)
4.00
Outlet diameter diffuser (m)
2.75
Shaft power (kW)
395
Total efficiency (-)
0.70
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Initial design • Multiple stream tube analysis ‣ Simple radial equilibrium inlet and outlet ‣ No work exchange between streamtubes ‣ Expressed for nine blade sections
• Resulting design:
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Overview • • • • •
Initial design Sealing rotor Rotor flow analysis Diffuser flow analysis Off-design performance
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Obtaining rotor sealingness • Initial design ‣ Rated flow:
‣ Closed:
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Means to reach sealingness • • • •
Stacking (lean and sweep) is not efficient Solidity distribution: large chord at hub Thickness distribution: large thickness at hub Camber distribution: zero camber at hub, large camber at tip • Untwist rotor: large incidence at hub (10.8˚) and negative incidence at tip (-2˚)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Obtaining rotor sealingness • Closed at tip and hub
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Obtaining rotor sealingness • Adjustment of stagger angles: max 1.7˚
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Blade form
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Final design
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Overview • • • • •
Initial design Obtaining rotor sealingness Rotor flow analysis Diffuser flow analysis Off-design performance
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rotor flow analysis: CFD package FLUENT Flow domain
Inlet Plane Interior Plane (Inlet→Blade) Periodic Plane Interior Plane (Blade→Outlet)
Inlet 600mm
Outlet Plane
Blade
Outlet1 300mm 300mm
600mm
Outlet2
550mm 287mm
1050mm
1050mm 400mm
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Blade surface grid
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rotor flow analysis • CFD Analysis (SRF, k-ω SST, EWT)
‣ Radius 475mm ‣ Big incidence, but lower than expected ‣ No separation ↑ Relative Velocity Magnitude Vector (m/s) ← Static Pressure Contour (Pa)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rotor flow analysis
‣ Radius 700mm
↑ Relative Velocity Magnitude Vector (m/s) ← Static Pressure Contour (Pa)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rotor flow analysis ‣ Radius 925m ‣ Almost zero incidence (small negative incidence)
↑ Relative Velocity Magnitude Vector (m/s) ← Static Pressure Contour (Pa)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rotor flow analysis Suction side
Static Pressure Contour (Pa)
Relative Velocity Magnitude Vector (m/s)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Flow distribution stream tube analysis
Stream tube
hub
Radius ( m)
0.4
0.475
0.55
0.625
0.7
0.775
0.85
0.925
1
u ( m/s)
5.445
6.466
7.487
8.508
9.529
10.551
11.572
12.593
13.614
c1a ( m/s)
6.813
6.583
6.394
6.233
6.094
5.971
5.862
5.764
5.675
w1u ( m/s)
2.046
3.182
4.297
5.399
6.489
7.571
8.647
9.717
10.782
c2a ( m/s)
6.021
6.074
6.094
6.095
6.087
6.072
6.054
6.033
6.011
w2u ( m/s)
6.619
7.15
7.80
8,.514
9.282
10.094
10.938
11.801
12.676
tip
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Flow distribution CFD analysis
CFD
hub
tip
Radius ( m)
0.4
0.475
0.55
0.625
0.7
0.775
0.85
0.925
1
c1a ( m/s)
4.981
6.011
5.944
5.961
6.022
6.098
6.165
6.200
5.106
w1u ( m/s)
2.305
3.249
4.384
5.472
6.563
7.626
8.692
9.737
10.586
c2a ( m/s)
5.360
6.430
6.238
6.087
5.920
5.880
6.128
5.994
4.930
w2u ( m/s)
7.002
7.645
8.395
9.250
10.104
11.035
11.842
12.697
12.931
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rotor flow analysis
CFD
hub
tip
radius ( m)
0.4
0.475
0.55
0.625
0.7
0.775
0.85
0.925
1
ΔW ( m²/s²)
25.577
28.423
30.028
32.144
33.743
35.966
36.456
37.267
31.924
Work extracted by turbine is bigger than intended Flow is aligned to tip section: more flow rate, more work Unloading of the hub (fortunate)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Performance • Diffuser recovery factor 0.70 • Stream tube analysis: Q= 16 m3/s, H= 3.60 m Pshaft= 387 kW, ηglob = 0.69 • CFD-analysis Pshaft= 540 kW, Q= 16 m3/s, H= 4.40 m ,ηglob = 0.74 (with mechanical losses: ηglob = 0.72) → rematching necessary
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Rematching
• Work extracted by turbine is too big → allow bigger flow rate • Open stator and open rotor α = 26.5˚ → 23˚ , βtip= 63.5 ˚ → 60˚ Some loss of efficiency ηglob ≈ 0.70
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Overview • • • • •
Initial design Obtaining rotor sealingness Rotor flow analysis Diffuser flow analysis Off-design performance
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser design • Geometry
Velocity Inlet
Mixing Plane Inlet Blade Cone
Pressure Outlet
Diffuser 370mm
600mm
4000mm
400mm
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser analysis • CFD Analysis (Mixing plane, k-ω SST) ‣ Static Pressure Contour(Pa)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser design • CFD Analysis (Mixing plane, k-ω SST) ‣ Radial Velocity Magnitude Contour (m/s)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser design • CFD Analysis (Mixing plane, k-ω SST) ‣ Axial Velocity Magnitude Contour (m/s)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser performance verification Analysis planes Inlet rotor →
←Outlet rotor ←Inlet diffuser
Outlet diffuser →
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser performance: pressure recovery factor
Diffuser maps: LR
L R2
AR
A4 A2
L
4
1 1 2 2 2 Dtip Dhub 2 0.82 2 2 2 2 R4 1.37 2.235 2 R2 0.91652
Cp
0,700
4.364
Cp 0.700
CFD analysis: Cp
p4 p2 1 2 v 2 2
p2 11468.77Pa p4 1608.21Pa v2 6.112 m s
Cp 0.700
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Diffuser performance: α = 26.5˚ → 20˚: post-swirl Velocity variation
Inlet diffuser
Outlet diffuser
Axial Velocity (m/s) → Tangential Velocity (m/s) ↓
Inlet diffuser
Outlet diffuser Inlet diffuser = mixing plane
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Outlet diffuser
Overview • • • • •
Initial design Obtaining rotor sealingness Rotor flow analysis Diffuser flow analysis Off-design performance
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Off-design performance: α = 26.5˚ → 20˚ ; β = 63.5˚ → 78˚; Q=8 m3/s (H=3.20 m) • Rotor ‣ Velocity Vector Fields: No separated flow!
↑ Relative Velocity Magnitude Vector (m/s) at radius 475mm
← Relative Velocity Magnitude Vector (m/s) at radius 925mm
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Off-design performance: ηglob = 0.60 • Diffuser ‣ Static Pressure Contour (Pa)
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent
Conclusion • Design of an axial hydro turbine with a movable rotor and blade shape such that the rotor can be completely closed was successful • Rated conditions: Q= 16 m3/s, H= 3.60 m Pshaft= 390 kW, ηglob = 0.70 • Half flow rate: ηglob = 0.60
Department of Flow, Heat and Combustion Mechanics – www.FloHeaCom.UGent.be Ghent University – UGent