chanju-i model test report

8/3/2019 Chanju-I Model Test Report

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B FOURESS

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LIMITED

MODEL TEST REPORT

PROJECT : CHANJU-I

(3 x 12000 KW + 17% OL)

Doc No: CHANJU-I-MTR

Rev. : - Nil -

Date : 9-12-2011

Page: 1 of 18

Model Test Report of

Vertical Type Francis Turbine

Project: CHANJU-I

(3 12000 K R t d 17% OL)


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INDEX

Clause No. Title

1.00 Introduction to Laboratory facilities

2.00 Model turbine

2.01 Similarity Criteria

2.02 Selection of Turbine model for Chanju-I

2.03 Model Description2.03.1 Spiral Casing

2.03.2 Guide Vane

2.03.3 Draft Tube

2.03.4 Runner

2.03.5 Shaft and Bearings

2.04 Model Details

3.00 Experimental Investigations

3.01 Test Objectives

3.02 Model Installation

3.03 Experiments

3.03.1 Normal Performance Tests

3.03.2 Runaway Tests

3 03 3 Cavitations Tests


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NOMENCLATURESymbol Description Unit

H Net Head across the turbine Metres

Q Discharge m/s

N Speed rpm

D Runner Diameter Metres

Efficiency Percent

Guide Vane opening Degree

Fr Froudes Number

V Absolute velocity m/s

g Acceleration due to gravity m/s

Re Reynolds Number

Coefficient of kinematics viscosity m/sCp Pressure coefficient

PPressure kgf/m

Density kg/mU Peripheral Velocity m/s

Efficiency Scale Effect PercentPt Output or mechanical power HP or kW

/D Surface roughness expressed in termsof runner diameter

/DTip clearance expressed in terms of

r nner diameter


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1.00 INTRODUCTION TO LABORATORY FACILITIES:

Today no hydraulic machine can be manufactured and put into successful operation

without a preceding phase of theoretical and experimental research. The complexity of

the hydraulic phenomena occurring in the machinery under different operating

conditions and the required accuracy of the performance date necessities careful testing

of models in special test stands. The results of mode test investigations can be used:

(a) As original and main data for selection of main full-scale turbine parameters and

prediction of efficiency, cavitations, force and pulsation characteristics.

(b) For the stress calculations of the turbine and hydro generator coupled with turbine.

(c) For the verification and improvement of the applied hydro - dynamic methods of

calculations.

(d) To check and improve the existing scale-up formulae.

Our Technology provider M/s. G.E.Energy Ltd., Sweden, operate an extensive

hydraulic research facility. Since 1914, this laboratory is responsible for basichydraulic research and development and maintains highest level of research facilities.

Today it is one of the best of its kind in the World and often they are engaged for

contractual model testing and experimental research in the field of hydraulics, including

cavitation studies.

The test equipment is located in the laboratory main block, which has a length of 40m,

a width of 12m and a height of 12m.


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The laboratory has various test facilities available as given below: (Refer annexure 4)

1. Open flume test stand for testing of Kaplan and low head Francis models.

2. Low head cavitation tunnel for efficiency and cavitation testing of low head turbines.

3. High head cavitation tunnel for Francis and reversible pump turbines.

4. Pump test tunnels for axial, diagonal and mixed flow pumps.

5. Various other facilities for simulation studies and other hydraulic research activities.

2.00 MODEL TURBINE :

2.01 SIMILARITY CRITERIA

Homologous model tests on water turbines are based on well proven similitude criteria

which can be summed up into the relation :

Cp : Pressure coefficient

Fr : Froude number

Re : Reynolds number

U : Peripheral velocity

V : Absolute velocity

/D : Surface roughness expressed in terms of runner diameter /D : Tip clearance expressed in terms of runner diameter

Th C i i


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Where

Q = Discharge in m/s.

D = Diameter of runner in metres.

H = Head in Meters.

N = Speed in rpm

Subscripts :

m = Model Turbine

p = Prototype

2.02 SELECTION OF TURBINE MODEL FOR CHANJU-I

Extensive research and development activities undertaken have resulted in many model

turbine configurations. As such our collaborators have designed various models

suitable for low head applications. Deciding model size and testing parameters was

done adhering to the recommendations of International Electro- technical Commission(IEC 193 & IEC 995)

On the basis of site data indicated, we have chosen L-202-22-712 model among various

models available. A detailed design was carried out to arrive at the main turbine

parameters such as runner diameter, speed and determining the general layout of the

hydro unit from these model test reports.

O d i h i L 202 22 712 d l h t i ti f thi j t it


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2.03.2Guide Vane

The Guide Vane serves to change the discharge through turbine. It consists of a system

of evenly arranged 24 Nos. of guide vanes along its circumference. These vanes are

designed with appropriate shape & profile. Turning all the vanes on the same angle by

means of special Kinematics mechanism will vary the angular momentum and the flow

pattern before the runner resulting in the variations of the discharge.

The Guide Vane is circular in shape and hence supplies water to the runner in the

oblique direction decreasing the velocity unevenness in the flow at the entrance of the

runner. The axes of the vanes are located on a cylindrical surface and each vane has

different sections of the Guide Vane, varying cross sections of the vanes, overall shape

of the Guide Vane offers specific hydraulic advantages.

2.03.3 Draft Tube

The draft tube is the last hydraulic element of a reaction turbine which considerably

effects both the turbine performance and the arrangement. In general the hydrauliccharacteristics of draft tube depends on its shape and dimensions as well as flow

patterns at its entrance. The most important suction element of the turbine i.e. draft

tube serves the following purposes :

(a) to conduct the flow from the runner to the tailrace with minimum energy losses

(b) to facilitate setting of the runner above the tailrace without loss of head

(c) to transform the kinetic energy of flow at the exit of runner into additional vacuum

b hi d it th t i t id bl d th ki ti l t th it f


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The turbine shaft transmits the torque and is subjected to axial and torsional loads. The

axial load is mainly due to axial water pressure force. The shaft could also be subjected

to lateral forces because of unbalance in the rotating parts. The shaft is designed for

critical speed of well above the expected runaway speed of the turbine. Suitable

bearings to absorb the axial thrust and other radial loads are provided.

2.04 MODEL DETAILS

RUNNER

Number of Runner vanes 15

Tip diameter 250 mm

Vane height 47 mm

SPIRAL CASING

Spiral inlet dia. 463 mm

No of stay vanes 12 NosStay vanes pitch circle dia 415 mm

Guide Vane

Shape and included angle Aerofoil

Guide vane PCD 415 mm

No. of guide vane 24

Vane height 47 mm

V l t t d 0 1


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3.0EXPERIMENTAL INVESTIGATIONS3.01 TEST OBJECTIVES

Advanced and reliable model investigations are employed for identifying the

performance characteristics of the turbine that can also form basis to develop new

designs with better efficiency, cavitation, pulsation and other characteristics and

advanced turbine spaces, modern hydro dynamic methods of calculations. Since the

accuracy of model investigations influence considerably the reliability of turbine

characteristics and guarantees for full-scale turbines, the demands on the tests stands

and their instrumentation are increasing.

As emphasised in Section 3.01, number of factors have influence on the similarity to

exist between model and prototype flows, the main idea is to fulfil the most important

similarity requirements and carryout the model investigations simulating the field

conditions as for as possible. Hydraulic parameters and turbines characteristics are

determined by various elements of the turbines space which are calculated or selectedon the basis of numerous assumptions. Moreover, they are designed usually without

taking into account the mutual influence on their individual characteristics. It is for

these reasons that the final assessment of the developed turbine can be made by careful

and detailed tests on the model.

On the basis of similarity laws, a number of turbine models for different heads (specific

speeds) have been developed in laboratories and are used for geometrically similar full-

l bi i h i i f d l F h h f ll i


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The assembly of the complete turbine model, which involved precise matching of

various components relative to recesses, clearance and water tightness, was

accomplished independently outside test rig. The total assembly along with its base

was then installed on the test rig accurately.

3.03 EXPERIMENTS

Exhaustive experimental studies were undertaken to establish the normal performance,

runaway features, and cavitation characteristics of the model in its entire operating

range. The model speeds are changed so as to cover a wide range of unit speeds

varying from 43 to 48. A test head of 35 m was chosen during normal performance test

of the model. For a good statistical average, more number of readings was recorded on

the parameters at a reasonable time interval. The values then were averaged out over a

period by noting small fluctuations if any due to supply voltage and frequency

fluctuations or any other reasons.

3.03.1 NORMAL PERFORMANCE TESTS:

These tests determine the normal efficiency characteristics of the model turbine under

non - cavitating conditions for various guide vane angle opening () ranging from 6 to20. The general efficiency characteristics of the model corresponding to this are

enclosed in the report. The procedure adopted in the normal performance tests is

briefly recapitulated below.

For a predetermined value of unit speed, the individual performance test consisted of

operating the model at various angles. For every test point, readings were recordedfor model discharge, rotational speed, torque, etc., for determination of brake horse

d h d li F h b i i d i


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3.03.2 RUNAWAY TESTS:

Runaway tests were conducted for various guide vane opening to find out the most

stringent conditions in respect of speed for the generators shaft design. A suitable test

head was adopted during these studies taking into consideration the mechanical strength

of various materials used, flow conditions in the draft tube as well as general limitations

imposed by safe model operation. Fig. 2 shows the results of the runaway tests for

various guide vane openings.

3.03.3 CAVITATION TESTS

These test series were conducted in respect of selected optimum cam conjugation points

established during normal efficiency tests, the main objective being the study of effects

of cavitation on the behaviour of the machine. The procedure adopted in a cavitation

test is briefly recapitulated below.

For a predetermined values of guide vane opening angles, and model speed, the

experimental programme commenced under non - cavitating conditions with a highsigma value initially. Thereafter the operating sigma value was reduced step by step to

induce cavitation by lowering the absolute pressure in the test installation with the help

of auxiliary vacuum circuit. For each test point, output or mechanical power, input or

hydraulic power, unit speed, efficiency, unit discharge and the cavitation coefficient

were calculated. Curves were then plotted for establishing the relationship between

thoma sigma versus unit discharge for each set point of N11, . The effect ofcavitation on the turbine performance was also simultaneously noted. As cavitation

ld d b d b f i i i d h hi f i l


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For arriving at values of prototype efficiencies and corresponding power outputs for

comparison with the guaranteed values, Moodys transposition formula was used in

calculating the majoration percentage at the point of peak efficiency on the model. This

majoration percentage correction was then applied equally at all other related measured

model efficiency values on the general efficiency values on the general efficiency

diagram for predicting prototype performance under the stipulated conditions.

Moodys formula which is widely adopted for Francis turbines and takes into account

variation in both head and diameters is as given below.

Moodys Formula = (1-m) {1-(Dm/Dp)

0.2}


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Annexure-I

Performanc e Ca lculations based on Mod el test Results

A. Data:

Turbine Type Vertical type Francis turbineModel Turbine Data :

1. Mo del Number L 202-22-7122. Mod el Hea d 35 m3. Model Runner Diame te r 0.250 m

Protot ype Turbine Data :

1. No. of units x Rating 3 x 12000 kW2. Rate d turbine outp ut Prat 12371.1 kW3. Runne r Diam eter D 910mm4. Rate d hea d Hrat 236.67 m5. Rated spe ed n 750rpm6. Ra ted d isc ha rge Q rat 5.682 m/s7. Ma ximum turbine outp ut Pma x 14474.2 kW

8. Ma ximum disc harge Qma x 6.695 m/s

9. Ma c hine Ce nte r line eleva tion 1189.05 m

10. Minim um Ta il Wat er Level 1192.05 m

11. Ma x Hea d Hma x 246.00m


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Where Q Disc ha rge in m/ s

D Runner d iame te r in me ters

H Hea d in me ters

the refo re Unit d isc ha rge Q11 = 6.695 / 0.91 * 236.670.5

= 0.526 m/s

From G enera l effic ienc y cha rac te ristic c urve L 202-22-712 (Fig.1),

for Q11 = 0.526 m/s, mod el efficienc y m = 91.30%.

Then p roto type effic ienc y p = m +

= 91.30% + 1.82%

= 93.12%

Turbine rated output (kW) Prat = 9.81xQxHx p kW

= 9.81 x 6.695 x 236.67 x 0.9312 kW

= 14474.2 kW.

4. Ca vitation co effic ient = {(Hb - Hv) - Hs}/ Hrat

where = Cavitation c oefficient c orrespo nding to rat ed disc harge a t rated hea d (Thiswill be read from the model cavitation limit curve L 202-712 (Fig. 2)and in this c ase is0.04 for Q 11 = 0.526 m/ s.

Hb = Barome tric p ressure (8.92 m)


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Where n11 = 70 c orrespond ing to G V ang le of 15.3% from the c urve L 202-22-712 (Fig.3).

= N11 x sq rt (Hma x) / D

With 5% margin =

1206 rpm

1266.8 rpm

6. Sp iral Casing

The sp ira l ca sing is designed based on the d esign used in the m od el L 202-22-712 which is bee n

sca led up . From mo del the spira l ca sing d iam eter will be 1.016 x D =1.016 x 0.910 = 0.925m

7. Butt erfly va lve

The inlet of the spiral casing is the referenc e for the selec tion o f the Butte rfly va lve size. Here the

spiral inlet comes to 925mm. However 1200 mm valve is considered based on tender

requirement.

Given be low are the e ffic iencies at d ifferent % of load s at rate d he ad :

Sl. % of Load / Mo del Turbine Sc a le Proto typ e Turbine

No (Turbine out

put in kW)

Q11

(m/s)

N11

(rpm)

Model

Efficiency

(%)

Effect Considered

(%)

Q

(m/ s)

Prototyp

e

Effic ienc

y (%)

1 117%

(14474.2)

0.526 44.36 91.30% 1.82 6.695 93.12%

2 110% 0.4901 44.36 92.00% 1.82 6.247 93.82%


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chanju-i model test report

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