design of components of francis turbine p m v subbarao professor mechanical engineering department...
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Design of Components of Francis Turbine
P M V SubbaraoProfessor
Mechanical Engineering Department
Detailing to Infuse Reaction….
Specific speed in rpm4
5H
PNN s
P in hp & H in meters
Selection of Speed of A Turbo Machine
Hzfforz
Np
503000
Zp : Number of pairs of poles of the generator
Design of Any Selected Francis Turbine Unit
• Different capacities for each sub-group.• Design for Normal Head.• Assume an overall efficiency: 94 – 96%• Calculate the required flow rate.
HgQP Francis
General Layout of A Hydro Power Plant
Power Tunnel:Diameter: 15000mmLength= 746mSlope= 1 in 120Actual velocity: 5.563m/s
Power Tunnel
hgD
fVS
2
4 2
0
Channel Bed Slope
P
ADh
4
Penstock : Consider Velocity equal to Actual Site Velocity
penstock
penstockfriction gd
fLVHxh
2
4 2
2
9.0Re
74.57.3
log
0625.0
hD
kf
Pipe Material Absolute Roughness, emicron
(unless noted)
drawn brass 1.5drawn copper 1.5commercial steel 45wrought iron 45asphalted cast iron 120galvanized iron 150cast iron 260wood stave 0.2 to 0.9 mm
concrete 0.3 to 3 mm
riveted steel 0.9 to 9 mm
Estimate net Head available at the inlet turbine casing
Dimensions of Guide Vane Wheel
Group NO.
Unit SizeMW
Degree of Reaction, %
Dpenstock
mVpenstock
m/sHead loss
m
1
135.9
35
2 40
3 45
4
203.9
35
5 40
6 45
Design of Spiral Casing
Rcasing
Risv
dpenstock
Q
Inlet to Stay vanes
Guide vanes R
ing Stay vanes Ring
Runner
Design of the Guide VanesHow to choose the guide vane angle egv at full load
11344 2 egv
egv
Q
gH2/
gHQQ 2/
Specifications of Guide Vanes
• Slow Runner: Ns=60 to 120
– Begv/Dmgv=0.033 – 0.04
• Normal Runner: Ns = 120 – 180
– Begv/Dmgv=0.125 to 0.25
• Fast Runner: Ns = 180 to 300
– Begv/Dmgv=0.25to 0.5L: length of vane
L=15 to 30% of Degv
Dimensions of Guide Vane Wheel
Group NO.
Unit SizeMW
Degree of Reaction, %
Digv, m Degv, m Bgv, m
1
135.9
35
2 40
3 45
4
203.9
35
5 40
6 45
Design of the Guide Vane Outlet Angle
• The outlet angle can be calculated by assuming a vortex from the flow in the gap between the runner and the guide vanes
nwigv
nwegv igvegv
rVrV
egvegvfegv BD
QV
regv
rigv
Begv
Select appropriate value of n
Design of the Details of Stay Vanes
StayVaneinletStayVaneinletwGuideVaneinletGuideVaneinletw rVrV
rexit stay Vane
rinlet Stay Vane
Besv
Theory of Relatively Whirling flow:
Bisv
isvn
wisvesvn
wesv rVrV
isvSratyVaneinletStayVaneinletf BD
QV
penstockStayVaneainlet VV
At any angle , the radius of casing is:
penstockisv dRR2casing
A full spiral is generally recommended for high head 300m, semi-spiral is recommended for low heat <50m.
2QQ
In general =1.0, however corrected using CFD.
Performance of Casing : Loss of Total Pressure
Rcasing
Risv
dpenstock
Q
The losses in the spiralcasing as a sum f distributed losses and the exit losses
exitflscfscf hhh ,,,
g
V
d
lh sc
chspelscf 2
2
,,
222
2
, 8 isvisvexitf Bgr
Qh
02.001.0 25.01.0
Gap losses
Friction losses in the spiral casingand stay vanes
Guide vane losses
Friction losses
Runner losses
Draft tube losses
Number of Guide/stay Vanes
Ns Z=8 10 12 14 16 18 20 24
<200
Dge,mm
<250 250 - 400
400 - 600
600 - 800
800 - 1000
1000 1250
1250 1700
>1700
>200 <300 300 - 450
450 - 750
750 - 1050
1050 1350
1350 1700
1700 2100
>2100
Validation of the Guide Vanes DesignDegree Overlapping of the guide vanes
Low Overlap High Overlap
Specifications of Guide Vanes
L: length of vane
L=15 to 30% of Degv
Minimum Number of Guide/stay Vanes
Ns Z=8 10 12 14 16 18 20 24
<200
Dge,mm
<250 250 - 400
400 - 600
600 - 800
800 - 1000
1000 1250
1250 1700
>1700
>200 <300 300 - 450
450 - 750
750 - 1050
1050 1350
1350 1700
1700 2100
>2100
The Runner
Velocity triangles
rri
rre
Uri
Vwi
Vri
Vfi
Vai
Ure
Vwe
Vre
Vfe
Vae
i
i
ee
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
Diameter of guide vane shaft Vs Runner Inlet Diameter
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/
D1
DRI
DRE
07,129,0 RI
mgv
D
D
gH2/
Dmgv
Design of the Runner VanesHow to choose the number of vanes
• The number of guide vanes has to be different from the number of runner vanes.
Integerz
z
VanesRunner
VanesGuide
Ub
Vwi
Vai
VfiVri
Ub
Vwi
Vai Vfi
Vri
VwiUb
Vai
Vfi
Vri
Inlet Velocity Triangles Vs Ns
Low Specific Speed : Slow Francis Runner
Vwi
Vai
Vfi
Inlet Velocity Triangles Vs Ns
Low Specific Speed : Normal Francis Runner
Vwi
Vai
Vfi
Inlet Velocity Triangles Vs Ns
High Specific Speed : Fast Francis Runner
Vwi
Vai
Vfi
Specifications of Runner
• Slow Runner: Ns=60 to 120 to 250
– Kui = 0.62 to 0.68 to
– Bgv/Dmgv=0.04 – 0.033• Normal Runner: Ns = 120 – 180
to 32.50
– Kui = 0.68 to 0.72 – Bgv/Dmgv=0.125 to 0.25
• Fast Runner: Ns = 180 to 300 to 37.50
– Kui = 0.72 to 0.76 to
– Bgv/Dmgv=0.25to 0.5
Velocity triangles
rri
rre
Uri
Vwi
Vri
Vfi
Vai
Ure
Vwe
Vre
Vfe
Vae
i
i
ee
rU
UU
r
rire
13o < e < 22o
Design for Maximum Power
draftfte
RETEtwatmare
RE pV
gzgzgHpV
p ,
22
22
Net Positive Suction Head, NPSH
NPSH required
g
Ub
g
VaNPSH refre
R
22
22
15.005.0
15.105.1
b
a
Turbines
Dimensions of the outlet
g
UbUa
g
Ub
g
VaNPSH reererefre
R 2
tan
22
2222
13o < e < 22o
1,05 < a < 1,150,05 < b < 0,15
Highest value for highest head
Extra head to be converted into kinetic energy:
Remaining head to be used :
extraremainingrire HH
g
VV
2
22
Preferred Exit Velocity Triangle:
13o < RE < 22o
DRI
DRE
Available Inlet velocity Triangle
Runner Design
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