Chitravathi Pump Storage Project (500 MW)
Hydraulic Design - Power Intake Structure
Chitravathi PSP Upper Intake Design
1.0
Design Inputs:
2.0
Normal Operation (100%)
=
Full Reservoir Level (FRL)
=
300.38 m3/s
495.00 m
Min. Drawdown Level (MDDL)
=
460.00 m
Penstock Diameter, D (Circular)
=
7.70 m
No of Penstock
=
1.00 nos
Design Calculations:
2.1
Flow Characteristics
Normal Operation (100%)
Total design discharge
Discharge through each Intake
Flow velocity in Intake tunnel/HRT
2.2
300.38 m3/s
300.38 /1
300.38 m3/s
6.45 m/s
=
=
=
=
Required Bellmouth Opening
Cross sectional area of tunnel, A
=
0.7854 x 7.7^2
46.57 m2
0.60
=
Coefficient of contraction, C c (as per IS 9761:1995)
=
Inclination of intake (with horizontal), Ø
Required Opening Area, Ao
=
=
0.00
A/(Cc . CosΦ )
=
46.566 / (0.6 x Cos 0)
77.70 m2
=
2.3
Bell Mouth Shape Calculations
Gate Size:
Deeply seated intake structure which subjected to water head of;
55.0 m
Provided Gate Size:
Gate Width, w
=
8.5 m
Gate Height, h
=
8.5 m
Number of bays, n
=
Area provided at gate section,
=
Bellmouth Shapes:
a) Elevation (roof/bottom)
=
a1
1.1
b1
0.291
Height of opening, he
Hence, required width of opening,
*h =
=
*h =
=
=
=
1.0 nos
72.3 m2
 x 

a 

 1 
2
 y 

b 

 1 
2
1.1*8.5
9.40
0.291 x 8.5
2.50
2*b1 + h
1
m
m
m
m
=
2.5*2 + 8.5
13.50 m
Ao / he
=
77.7 / 13.5
=
5.80 m
Chitravathi Pump Storage Project (500 MW)
Hydraulic Design - Power Intake Structure
be
=
8.50 m
b) Plan
2
Sides profile
 x 
 y

a 
 
b
 2 
 2
=
a2
0.6 *be =
1
4.70 m
0.2143 *be =
0.2143 x 8.5
=
Width of opening,
2
0.55 x 8.5
=
b2




1.80 m
=
(2*b2 + w)
=
12.1
=
12.1 m
width is more than require hence ok
Hence area provided
=
163.35
hence ok
Note: The side profiles for intake have been proposed in reference to IS 9761:1995
2.4
Intake Submergence:
Proposed Intake Sill level
=
440.00 m
Intake approach invert level
=
440.00 m
Center Line Elevation
=
440 +2.5+ 8.5/2
=
MDDL EL 460.0
EL 11.00
 x

 a1
9.40 m
H = 13.2 m
2

 y
  

 b1



446.800 m
2
1
2.500 m
Flow
7.70 m
EL 446.800
2.500
440.00
9.40 m
Elevation
4.700
1.800
 x 


 a 
 2 
2
 y 

 

 b2 
2
 1
8.500
Flow
12.10
7.70 m
Plan
INTAKE STRUCTURE - GENERAL ARRANGEMENT
[ NOT TO SCALE]
i) As per IS 9761:1995
=
Submergence depth, S
Hence, S
=
460 - 446.8
13.20 m
Chitravathi Pump Storage Project (500 MW)
Hydraulic Design - Power Intake Structure
Determination of Froude Number, Fr
=
V/gD
a) Flow Area at Intake Gate
=
(8.5 x 8.5)
72.30 m2
46.60 m2
=
b) Flow Area at HRT
=
Minimum area of above shall governs the submergence.
Normal Operation (100%)
Velocity of flow at Intake Gate
=
Froude No, Fr
300.38 / 72.3
=
4.20 m/s
=
4.2 / Sqrt (9.81 x 7.7)
=
0.480
Overloading Operation (110%)
Velocity of flow
=
Froude No, Fr
300.38 / 72.3
=
4.20 m/s
=
4.2 / Sqrt (9.81 x 7.7)
=
0.480
Since Froud Number 'Fr' is more than 1/3, considered as medium/small size installation
H/D
Normal Operation (100%)
=
0.50
=
0.5 + 2 x 0.48
=
1.50
Minimum invert required
Normal Operation (100%)
Required Invert level
=
=
Take additional depth for saftey
=
Invert level at entrance
=
460 - 1.5 x 7.7 - 7.7/2
442.10 m
2.00 m(assumed)
440.00 m
ii) As per Gordon Formula
Min. submergence over tunnel crown,
=
S = C*V*[D/g]0.5
where,
Gordon's Coefficient, c
1.7
; for symmetrical approach
2.3
; for asymmetrical approach
Normal Operation (100%)
considering asymmetric approach, s
=
=
Minimum invert required
=
=
1.7 x 4.2 x (7.7 / 9.81)^0.5
6.33 m
460 - 6.33 - 7.7
445.97 m
Take additional depth for saftey
=
Invert level at entrance
=
443.00
2.00 m(assumed)
Hence, sill level is adequately provided at elevation;
=
440.00 m
Chitravathi Pump Storage Project (500 MW)
Hydraulic Design - Power Intake Structure
2.5
Trash Rack Layout Arrangement
Intake approach floor level
=
Permissible velocity - Mechanical Cleaning
=
440.0 m
1.50 m/s
Net area excluding trash rack
=
65%
Clogging % (for design)
=
30%
Flow depth at MDDL
=
460 - 440
=
20.00 m
Provide 5 bays of 4.5 m width
Width provided
=
Gross area of flow
=
22.50 m
20 x 22.5
450.00 m2
292.50 m2
=
=
Net area of flow
Net area in clogged condition
AKN/mB
Fixed Support
Support
Fixed 256
along
BA KN/m
B z-direction
=
=
292.5 x (1 - 0.3)
KD
59 C
C
x 2yC
D204.75 D
C
59
m
zD
Check for velocity
Flow velocity
=
Discharge / Area of flow
Velocity on gross area
=
300.38 / 450
=
0.70 m/s
Velocity on net area
=
1.03 m/s
Velocity on net area in clogged condition
=
1.47 m/s
<
1.50 m/s
No of bays
=
5.00
No of intermediate piers
=
4.00
Width of Intermediate piers
=
2.00 m
No. of side pier
=
2.00 m
Width of side pier
=
3.00 m
Clear width
=
22.50 m
Total width provided
=
36.50 m
Trash rack Dimensions
3.0
Reference:
1. IS 9761:1995 (Reaffirmed 2000), “Hydropower Intakes – Criteria for hydraulic design”.
2. IS 11388:1995 (Reaffirmed 2000), “Recommendation for design of Trash Racks for Intakes”.
3. IS 11570:1985, “Criteria for Hydraulic Design of Irrigation Intake Structures”.
OK