Guide vanes in Francis turbines
Transcript of Guide vanes in Francis turbines
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Guide vanes in Francis turbines
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El Cajon, HONDURAS
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Revelstoke, CANADA
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P = 169 MWH = 72 mQ = 265 m3/SD0 = 6,68 mD1e = 5,71mD1i = 2,35 mB0 = 1,4 mn = 112,5 rpm
La Grande 3, Canada
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La Grande 3, Canada
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La Grande 3, Canada
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Guide vane cascade, Francis
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Guide Vane End Seals
• High efficiency• Less erosion• Less leakage in closed pos.
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Guide vanes
Main function:Adjust the turbine load
The guide vanes consist of number of blades that can be adjustedin order to increase or reduce the flow rate through the turbine. The vanes are arranged between two parallel covers normal to the turbine shaft.
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Pressure distribution and torqueLL
DD
Torque
Arm
LL
DD
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Guide vanes in closed position
ZDl 0⋅π
= lBHgF 00 ⋅⋅⋅⋅ρ=
000 aFMTorque ⋅==
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Guide vanes in open positionTr
ailin
g ed
ge
Trai
ling
edge
Contour of the guide vane
Pressure distribution along the contour of the guide vane:
⋅⋅ξ
∑−⋅
−=
⇓
+⋅
+=
g2c
g2cHh
lossesg2
chH
22
2
Pressure distribution can be found using Bernoulli’s equation:
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Pressure distribution along the contour of the guide vane:
Stagnation-Point at Leading Edge
Small flow rateLarge flow rate
Guide vane contour
gc⋅2
2
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Variation of the torque when the guide vane opening changes:
( )020
m fQ
DM2C α=⋅ρ⋅⋅
=
α0
3
4
1
2
Sin α0
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c m1
cm145s H
Horsepowernn ⋅=
α0nsPowerplantα0nsPowerplant
38365Solbergfoss34198Nore II37346Gravfoss23113Grønsdal
36,5308Fiskumfoss18104Røssåga40,5308Fiskumfoss1378Mesna31,5269Iverland1372Hol I38,5264Oltesvik1269Nedre Vinstra27,5208Dynjafoss1266Skjærka
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38365Solbergfoss14
34198Nore II7
31,5269Iverland10
38,5264Oltesvik9
27,5208Dynjafoss8
36,5308Fiskumfoss12
40,5308Fiskumfoss11
37346Gravfoss13
α0nsPowerplant
23113Grønsdal6
18104Røssåga5
1378Mesna4
1372Hol I3
1269Nedre Vinstra
2
1266Skjærka1
The guide vane maximum angle α0 at full load
NB: This is for Norwegian designed GE-turbines
45s HHorsepowernn ⋅=
Specific speed, ns
Guide vane angle
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The servo’s work
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The servo has to:Take care of the torque from all guide vanesfor all guide vane angles
The torque consist of:Hydraulic torqueFriction torque
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Hydraulic torque
20m
QDC2M
⋅ρ⋅⋅
=
( )0m fC α=
The hydraulic torque can be found from a CFD-analysis
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Friction torque
( )Z
DBHd,fM ff
⋅⋅⋅⋅µ⋅αΩ±=
d
ff (Ω,α)= empirical valueµ = friction factor
H = Head
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Stroke
Friction
Closing
Opening
Hydraulic forces
Fully
ope
n
Opening
High head Francis turbineMeasurements of the servo’s work
Forc
e in
100
0 kg
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Horse shoe vortex damage
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Cavitation damage
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Sand erosion in the guide vanes
Jhimruk Hydro Power Plant
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Head coverHead cover
k
Bottom cover
Guide vane shaft
Head cover
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Z
Y
1 2
The deflection of the head cover
H = 435, P = 25 MW
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Reduction of clearance
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Efficiency of repaired turbine
[MW]
H = 430 m
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Design of the Guide Vane Inlet Angle
• The inlet angle can be calculated by assuming a free vortex from the flow coming from the spiral casing
StayVaneinletStayVaneinletuGuideVaneinletGuideVaneinletu rCrC ⋅=⋅
BDQCGuideVaneinlet
GuideVaneinletm ⋅⋅=π Dinlet Guide Vane
rinlet Stay Vane
B
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Design of the Guide Vane Outlet Angle
• The outlet angle can be calculated by assuming a free vortex from the flow in the gap between the runner and the guide vanes
110 rCrC uou ⋅=⋅
00 BDQCmo ⋅⋅
=π
D0
r1
B0
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Design of the Guide VanesHow to choose the number of vanes
• The number of guide vanes has to be different from the number of runner vanes.
Integerzz
VanesRunner
VanesGuide ≠
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Design of the Guide VanesHow to choose the number of vanes
• The number of guide vanes has to be different from the number of runner vanes.
Integerzz
VanesRunner
VanesGuide ≠
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Design of the Guide VanesHow to choose the guide vane maximum
angle α0 at full load
( )11344 2 +Ω⋅+Ω⋅−⋅=oα
α
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Design of the Guide VanesOverlapping of the guide vanes
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Design of the Guide VanesNumber of guide vanes
16
18
20
22
24
26
28
30
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6
Speed Number
Num
ber o
f Gui
de V
anes
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Design of the Guide VanesDiameter of guide vane shaft
1,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6
Speed number
Dia
met
er R
atio
D0/D
1
D1
D2
07,129,01
0 +Ω⋅=DD
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Statement of ProblemGivens Net head…………..….201.5m
Flow rate…………...2.35m3/sTurbine speed….1000rpm
Work out Design of Runner, Guide vanes,Stay vanes, Spiral casing andDraft tube
Compare Design output with Jhimruk turbines
Calculations - based on hydraulic principles only,
Thickness of runner blades - neglected,
Designs of components - done for the best efficiency point,
Other several assumptions - mentioned locally in calculations.
Design Considerations
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Design of Guide Vanes
.
1,0
1,1
1,2
1,3
1,4
1,5
1,6
1,7
0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6
Speed numberD
iam
eter
Rat
io D
0/D1
D
1
D
2
07,129,01
0 +Ω⋅=DD
Diameter of guide vane axisD0 = D1 (0.29 Ω+1.07)
−−−−⋅=Ω Qω
602 n⋅⋅
=πω
gH2/ωω =−−
66.1=−−ω
gHQQ 2/=−−
319.0=Ω
Chosen:Nos. of guide vanes z =20
mD 011.10 =
037.0=−−
Q
−−−−⋅=Ω Qω
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Design of Guide Vanes
.
Tangential and meridional velocities
05.11
)(CuC gvou = smC gvou /64.39)( =
smC gvom /58.8)( =
Assuming gap between runner and guide vanes5% of the runner inlet diameter.
[ (( )
∗−∗
=
απ
11
)( )Cosz
Qt
DBC
gvogvo
gvom
tan α(gvo) = Cm(gvo)/Cu(gvo)α(gvo) = 12.210
Value of αgvo in full guide vane open position is selected 180
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Design of Guide Vanes
.
Velocities at outlet, axis and inlet of guide vanes(depending on varing values of α and t)
Outlet agvo=12.210 tgvo=5mmCm(gvo) = 8.582 m/secCu(gvo) = 39.65 m/secCgvo = 40.56 m/sec
Axis agvc=28.040 tgvc=30mmCm(gvc) = 9.521m/secCu(gvc) = 17.87 m/secCgvc = 20.25 m/sec
Inlet agci=340 tgvi=15mmCm(gvi) = 7.864 m/secCu(gvi) = 11.65 m/secCgvi = 14.06 m/sec
Cm(gvi)=7.86 m/secCgvi=14.06 m/sec
Cu(gvi)=11.65 m/secCgvc=20.25 m/secCm(gvc)=9.521 m/secCu(gvc)=17.87 m/sec
Cgvo=40.56 m/sec
Cm(gvo)=8.58 m/secCu(gvo)=39.65 m/sec
L = 204
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Design of Guide Vanes
Guide vane at DesignPosition = 12.21°
Guide vane at closed position
Guide vane at Max. openPosition = 18°
.
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Guide vanesGuide vanesGuide vanesGuide vanesGuide vanesGuide vanes
Runner inlet (Φ 0.870m)
Guide vane outlet for designα) (Φ 0.913m)
ClosedPosition
Max. Opening Position
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R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanes
R a d i a l v i e wrunner guide vanes and stay vanesR a d i a l v i e wrunner guide vanes and stay vanes
Water from spiral casing
Water particle