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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH Vol. 2. No. 6. November, 2010, Part II

OPTIMIZATION ON PENSTOCK DIMENSION OF AMPEL GADING HYDRO ELECTRICAL POWER, INDONESIA

Endang Purwati1, Herlien Indra Wahyun2

1Water Resources Department, 2Civil Engineering Department, Faculty of Engineering,

Brawijaya University, Malang (INDONESIA)

ABSTRACT This paper studied the optimization dimension of penstock of hydro electrical power. The case study was at

Ampel Gading, Tawangsari Weir at Grojogan River, Indonesia. The methodology consisted of dimensioning optimi-zed penstock diameter due to hydraulics structure constraints. Diameter and thickness of the penstock were desig-ned at this study. Result was used to build the hydraulic structure of hydro electrical power at this location.

Key words: penstock; diameter; thickness 1. INTRODUCTION Local hydraulic phenomena to the vicinity of channel junction are of considerable practical importance as

they may be effect the flow condition in the combining channel [1]. A circular cross section has long been recog-nized as a very efficient section for the transport of fluids. However, it does not imply that the same cross section is suitable for stimulating pipelines [2]. The question of solvability of pipe networks requires some clarification. There is no restriction on the number of the equality constraints and associated parameter calculations as long as a one-to-one relation is maintained [3].

Project of Ampel Gading hydro electrical power was intended to build a power station that used a natural po-tency advantage region. This research plan was to dimension penstock that was crucial part of water power electri-cal structure. Penstock was usually made of steel material which was able to sustain high pressure and bearer flow from the head race to turbine. The research constitute a diameters as a treatment and then analyzed an optimum diameter pipe (concordant to economical and technical aspect), and determined a thickness of pipe for tension control regarded to the permit tension. (σ < σijin ).

2. MATERIALS AND METHODS Tawangsari Spillway at Bebek River and Grojogan Spillway at Grojogan River still at the region that could

use for supplying electric and it got a discharge of 5 m3/s at Ampel Gading hydro electrical power. Gross head was 229,20 m to get up electrical power, set down at downstream river. The length of water way from storage to penstock L = 307 m. The power could be get up 9602.334 KW, so that was hoped to give electrical capacity addition.

The steps of this study was to analyze 1) theoretical power; 2) theoretical diameter; 3) head losses that were instead of major and minor head losses, this section was intended to get effective head; 4) economical diameter of penstock, this section was carried out by analyzing water hammer and optimum diameter of penstock; 5) minimum thickness of penstock (pipe was made of steel).

Some formulations were used to design penstock. The formulations that were used in this study were as below [4]:

Daaland formula was used to calculate pipe diameter D = 0,176 466.0)(

effHP .

Wave velocity was calculated with the formula:

.1

1

ED

kgw

c

The formula of pipe thickness:

tEpD

EbEc .11

.

3. RESULTS AND DISCUSSION Theoritical power: P = 9,8 η. Q. Heff (kw), Q = 5,0 m3/s, hydraulic efficiency was 95 %, H brutto = 229,20 m,

Heff = 217,74 m. P = 9602,334 Kw = 12867,1276 HP. Diameter of penstock: D = 0,176. (74,2171276,12867 ) 0,466 = 1,18 m.

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Diameter of penstock due to empirical formula: 1,18 m. Economical diameter was trialed and was got at approximately 1,18 m and it was selected the economics one, the calculation was as Table 1, 2, 3, 4, and 5

Table 1. Total of head losses at UpStream

Dn (m) 1,00 1,20 1,40 1,60 1,80 2,00

hf 0,4934 0,3869 0,3151 0,2637 0,2254 0,1958

he 0,103 0,050 0,027 0,016 0,001 0,007

hb 0,103 0,050 0,027 0,016 0,001 0,007

hv 0,310 0,150 0,081 0,047 0,030 0,019

hl 1,009 0,637 0,450 0,343 0,257 0,229

Table 2. Total of head losses at Down Stream

Dn (m) 1,00 1,20 1,40 1,60 1,80 2,00

hf 0,627 0,492 0,400 0,335 0,286 0,249

he 0,103 0,050 0,027 0,016 0,001 0,007

hb 0,103 0,050 0,027 0,016 0,001 0,007

hv 0,310 0,150 0,081 0,047 0,030 0,019

hl 1,143 0,742 0,535 0,414 0,318 0,282

Table 3. Analyzing of economical pipe at Up Stream

Dn (m) 1,0 1,2 1,4 1,6 1,8 2,0minimum thickness (m) 0,007 0,007 0,007 0,007 0,007 0,007weight of pipe 34,0770 45,4606 58,3668 72,7958 88,7476 106,2220value of pipe[@Rp.1,106/ton]head losses (m) 1,009 0,637 0,450 0,343 0,257 0,229power losses (kw) 44,497 28,092 19,845 15,126 11,334 10,099energy losses (kwh) 384453,216 242712,288 171460,800 130691,232 97923,168 87254,496value of energy head losses[@Rp.168/kwh]Total value 98.665.140 86.236.264 87.172.214 94.751.927 105.198.692 120.880.755economical ranking 4 1 2 3 5 6

88.747.600 106.222.000

16.451.092 14.658.75528.805.414 21.956.127

58.366.800 72.795.80034.077.000 45.460.600

64.588.140 40.775.664

Table 4. Analyzing of economical pipe at Down Stream

Dn (m) 1,0 1,2 1,4 1,6 1,8 2,0minimum thichness (m) 0,007 0,007 0,007 0,007 0,007 0,007weight of pipe 43,2900 57,7512 74,1468 92,4768 112,7412 134,9400alue of pipe[@Rp.1,106/ton]head losses (m) 1,143 0,742 0,535 0,414 0,318 0,282power losses (kw) 50,406 32,722 23,594 18,257 14,024 12,436energy losses (kwh) 435510,432 282719,808 203847,840 157743,936 121165,632 107448,768alue of head energy losses[@Rp.168/kwh]Total value 116.455.753 105.248.128 108.393.237 118.977.781 133.097.026 152.991.393economical ranking 3 1 2 4 5 6

112.741.200 134.940.000

20.355.826 18.051.39334.246.437 26.500.981

74.146.800 92.476.80043.290.000 57.751.200

73.165.753 47.496.928

Table 5. Stress of Pipe No Type of stress Stress (kg/cm2)

I Strees of Tangent 339,233 II Strees paralel to pipe as a Stress due to pipe position 75,391 b Stree due to the empty weight of pipe 0,581 c Stress due to the move between pipe and position 1183,443 d Stress due to pressure force at the expand connection 36,346

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INTERNATIONAL JOURNAL Of ACADEMIC RESEARCH Vol. 2. No. 6. November, 2010, Part II

4. CONCLUSIONS Based on analyzing as above, economical diameter penstock was 1.40 m, the thickness = 7.0 mm and

stress was 1339.431 kg/cm2 (< ultimate stress = 1.400 kg/cm2). The result was due to the pressure of water hammer and it was controlled with the existing stress.

REFERENCES

1. Chan-Lin Chin and David W. Murray. 1992. Variation of Velocity Distribution along Non uniform Open-Channel Flow. Journal of Hydraulic Engineering, Vol 118, No 7, page 993-1100

2. George C. Christodoulou. 1993. Incipient Hydraulic Jump at Channel Junction. Journal of Hydraulic Engineering, Vol 119 No 3, page 409-421

3. Yee Meng Chiew. 1992. Effect of Spoilers on Scour at Submarines Pipelines. Journal of Hydraulic Engineering, Vol 119 No 9, page 1311-1317

4. Weber, N.B. 1971. Fluid Mechanics for Civil Engineers. New York: John Wiley # Sons, Inc.