design and development of a reversible pump turbine test rig

Ravi Koirala et al.: Design and Development of a Reversible Pump Turbine Test Rig

Rentech Symposium Compendium, Volume 4, September 2014 80

Design and Development of a Reversible Pump Turbine Test

Rig

Ravi Koirala*1, Sailesh Chitrakar

1, Niroj Maharjan

1, Nikhel Gurung

1, and Bishnu Prasad Aryal

1

1Turbine Testing Laboratory, Kathmandu University, Nepal

Abstract—Turbine testing for the performance analysis of the

design has been one of the mostly accepted and widely used

methods in the current trend of Research and Development.

Reversible Pump Turbine [RPT] is a new concept in turbine design

for Nepalese scenario, which addresses the need of the pump

storage and its role for compensating the current demand. In this

paper, an RPT designed for Chilime Hydropower Plant is scaled

down to a small model, fabricated and an RPT test rig is designed

and developed for testing of the turbine in dual (turbine and pump)

mode.

This paper explains the model down methodology along with

the test rig design and testing of the model turbine in the rig. The

scaling down process was performed following the basic norms of

the IEC 60193 guideline for the model testing. Although the rig is

designed to be operated in dual mode, theinitial priority in this

paper has been given to the turbine mode, wherean initial

measurement has been completed. The measuring equipment like

pressure transducers, flow meter, torque transducer and

tachometers are installed in the rig and data are taken through the

Data Logger. Moreover, design and development of the test rig and

testing strategies have been focused, which will provide a platform

for rigorous testing of the turbine in future.

Index Terms—Turbine testing, Performance analysis, RPT,

IEC, Turbine Mode

I. INTRODUCTION

There has always been a vast difference between the

design and operational point of turbines. Majority of

turbines are designed at Best Efficiency Point (BEP), but are

mostly operated in off design conditions because of varying

load and flow on seasonal and/or daily basis. Under this

operational scenario, it is always difficult to predict the

performance of a turbine on site since this may vary with the

conditions. Hence, it is of great importance to carry out

laboratory testing to measure the performance of the turbine

at several operating conditions.

This study is a part of Renewable Nepal Project carried

out at Turbine Testing Lab, Kathmandu University, which is

related to the capacity development of utilization of

Reversible Pump Turbine (RPT) in Nepalese Hydropower.

RPT or Pump storage are the systems designed to take

benefit of the load variation in daily load cycle, where it

fulfills the peak demand by utilizing the excess energy at off

demand time to pump the water to upper reservoir [1].

Hydropower plants in Nepal during monsoon have an excess

amount of water supply while in dry season, it is difficult to

meet the minimum of water required to run all the units.

*Corresponding author: [email protected]

There are several sites in Nepal, having two rivers flowing

close to one another at different head. By using an RPT unit

as a link between such rivers, water can be pumped from

lower reservoir to the upper reservoir during dry season to

meet the flow of the turbine in the main unit with less

amount of energy needed to pump, due to the head

difference. While in monsoon when the water supply is

more, the excess amount of water is sent through the RPT

generating an excess amount of electricity [2].

Particularly, operational process of turbine is a complex

phenomenon, but testing it is another complex issue. Setting

a laboratory facility to estimate the performance of a turbine

requires the flow loop, head and flow control, safety

systems, load control, turbine and moreover measuring

equipment like flow meter, pressure transducers, tachometer,

and torque transducer.

Under this project, an RPT was designed considering the

case of Chilime Hydropower Plant [3]. In this paper, the

details regarding the model development, test facility setup

and testing in turbine mode are presented. A chart showing

the details of the whole project and the scope of this paper is

clarified in Figure 1.

II. MODEL TURBINE DESIGN AND

FABRICATION

The prototype RPT turbine was designed based upon the

major design parameters from Table 1. The design was

performed on a MATLAB based Graphical User Interface

[GUI] program designed to provide the 3D runner profile as

output [4].

TABLE I: DESIGN PARAMETER FOR

PROTOTYPE

Symbol Parameter Unit Value

H Head m 270

Q Flow m3/s 4

Zpoles Number of poles - 3

h Efficiency - 0.96

The model turbine for the RPT was designed following

the similarity of dimensionless numbers between prototype–

model based on IEC 60193 guideline. Although the design

prepared afterwards lacks some of the basic features of IEC,

this approach can provide an estimation of the performance.

For a model and prototype to be similar, following

dimensionless numbers must be conserved in the two

designs [5].



Fig. 1: Workflow of the overall project and scope of this paper

Same discharge factor, (QED)A = (QED)B

Where discharge factor is given by;

Q�� =Q�

D��gh

Same speed factor, (nED)A = (nED)B

Where speed factor is given by;

n�� =nD

�gh

Same Thoma’s number, σA = σB

Where Thoma’s number is given by;

σ� = NPSE

�gh

From the above equations, the parameters of a model

with 1.6 kW and 1500 rpm were calculated and major

operating variables as shown in Table 2 were obtained.

TABLE II: OPERATING VARIABLES OF THE MODEL

Symbol Parameter Unit Value

N Speed rpm 1500

P Power kW 1.6

Hm Model Head m 12.06

Qm Model flow m3/s 0.02043

Dmo Outer diameter m 0.117

SF Scale factor - 0.17

The model turbine thus generated are to be tested in lab

hence it is important to calculate the velocity triangle to

identify the test conditions. Velocity triangles in the model

and the prototype are related to each other by a factorial

term called Reducing Parameter [RP] which is numerically

given by,

R� = �2gH�

Once this reducing parameter is multiplied to the reduced

velocity component then the magnitude of velocity is

obtained where the direction is similar to the prototype. The

velocity triangle is shown in Figure 2.

Fig. 2: Velocity triangle of the model turbine

Based on the above calculated basic operational features,

the guide vanes, draft tube and spiral casing were designed.

All these components were provided with other mechanical

features as shown in Figure 3.



Fig. 3: Cross sectional view of the model turbine

The designed model turbine was manufactured in a local

industry in Nepal. The runner blade with an allowable

casting tolerance was initially printed with a 3D printer

available in the lab and later, this pattern was used as a

reference while forging a metal block. Figure 4 explains the

methodology for runner manufacturing together with the

final product. Similarly, the guide vanes were casted and the

developed surface of the draft tube and spiral casing were

bent and welded. Other supporting parts were machined.

III. TEST RIG DESIGN AND DEVELOPMENT

For the hydro-mechanical facility, two 5 Hp pumps were

used to generate the head in the loop. The head delivered by

the pump is controlled using a by-pass valve as shown in

Figure 5. The diameter of the pipe was selected based on the

pump rating considering the static head delivered by the

pump. Two diffusers were fitted in the loop at the pump

outlet and spiral casing inlet to match the flow and minimize

the losses. All these components are mounted over a

rectangular sump tank and water is circulated in the loop.

TABLE III: DESCRIPTION OF THE HYDRO-MECHANICAL COMPONENTS

S.N. Particular Description Unit

Feed Pump

1 Power 5 Hp

2 Head 24 m

3 Flow 16 & 6 lps

Piping specification

4 Pipe diameter 75 mm

The electromechanical features are governed by a 2 kVA

synchronous generator connected to loads at its output. This

feature makes the test rig flexible in terms of estimation in

part load and full load conditions as well. Turbine is

connected to the generator using a flexible spider coupling

system. The turbine has a facility to manually operate the

guide vane.

A test rig for hydraulic turbine is designed to test the

behavior against the exposed conditions where they are

provided with constant flow maintaining the flow features

along with the measuring equipments. The rig is installed

with the Pressure Transducers, Flow-meter, Torque

Transducer and Tachometer.

3.1 Measuring Equipment in the rig

i. Pressure transducer and gauge

Pressure transducer from Sensys was installed at the inlet

of the turbine to measure the pressure. A Data Logger of

Graphtec was used along with an excitation adapter for data

acquisition of the excited system. Figure 6a) shows the

pressure transducer used and its arrangement. The pressure

given by this transducer is identified using the equation

P = I − 4

8

Where, I is the current reading from the data logger and

P is the respective pressure. At the outlet of the runner, a

vacuum gauge was used to measure the suction pressure.

ii. Flow meter

An ultrasonic flow meter of Shenitech – 200H was used

for the flow measurement. This model has a feature to get

attached at the outer diameter of the pipe with the help of

strong magnet on its sensor. The receptor ends of the sensor

are applied with grease to prevent disturbances in the

ultrasound created and receive the proper signal.

iii. Torque transducer and tachometer

Torque transducer with the range of operation from 0 –

30 Nm and tachometer with the required range are used to

measure the torque and speed in the system. Since both of

them have their respective data logger, the display can be

observed on it.

IV. TEST METHODOLOGY

Experimental study refers to the controlled study of

expected phenomena and suitable presentation of acquired

data. It is almost impossible to control and relevantly

represent data unless a protocol plan is made. Unlike other

technical approaches, testing methodology in a rig is not

always similar. It mainly depends on the design of the rig.

Hence, a clear and concise methodology before conducting

the test was defined.

The operating head, flow, speed and torque are major

topics of interest, whose measurements are necessary to

compute the performance of the turbine. Figure 7 shows the

detail methodology for testing and computation.

An initial stage testing has been completed till date. The

testing was performed at a full guide vane opening and a

part flow condition. The mechanical efficiency was

calculated from the flowchart as shown in Figure 8. An

efficiency of 67 % was achieved in the given operating

condition. Next step in this project will be to conduct testing

at various operating conditions of head, flow and guide vane

angles, and to draw a hill chart diagram through

combination of the results.

Rentech Symposium Compendium, Volume

Fig.

Fig.

Plastic Model

Fabricated runner

Flow meter

Pressure sensor

Torque Transducer


Rentech Symposium Compendium, Volume 4, September 2014

Fig. 4: Turbine Fabrication Processes and final product

Fig. 5: Schematic view of rig and Developed rig system

Forging Process Forged Structures

Fabricated turbine

Final product from manufacturers

Design and Development of a Reversible Pump Turbine Test Rig

83

Blades generated after

Forging

Final product from manufacturers



a) Pressure Transducer b) Flow meter

c) Tachometer d) Torque meter

Fig. 6: Measuring equipment used in the rig

Fig. 7: Methodology of conducting the test

Fig. 8: Calculation of mechanical efficiency for each sampling



V. CONCLUSION

This paper presents an approach of conducting scale

down model turbine testing in the lab. The works presented

in this paper was a part of a project which contains design

and development of Reversible Pump Turbines. Such a

turbine was designed in the earlier activities of the project,

whereas in this paper, a test rig for the scale down turbine

was designed and developed. The scale down model turbine

was locally manufactured and the test rig setup was prepared

in the lab using measuring equipment needed for testing.

A rigorous testing procedure was developed in this

paper, which is suitable for preparing a hill chart diagram of

the turbine when operated at several ranges of operating

conditions. This paper also showed an initial stage test value

of efficiency at one operating condition. With few

modifications in the current rig, this rig is capable of testing

even in the pump mode. This includes a motor in the place

of generator, guide vane and draft tube modifications.

However, the work done in this paper was successful in

establishing a skeleton for conducting a systematic,

thorough and accurate testing in future.

ACKNOWLEDGEMENT

The authors express their sincere gratitude to Kathmandu

University and Renewable Nepal Program for providing the

funding needed for this project. The authors are grateful to

all the personnel, experts, technicians, students and

companies who were involved in this project. A special

thanks to Chilime Hydropower for motivating research

oriented activity and supporting in all possible ways.

REFERENCES

[1] B. Steffen, "Prospects for pumped-hydro storage in Germany,"

University of Duisburg-Essen (Campus Essen), Germany, 2011

[2] N.Maharjan, S. Chitrakar, N. Gurung, R.Koirala, "Pumped storage

concept and its potential application in Nepalese hydropower context

– A case study of Chilime Hydropower Plant, Rasuwa, Nepal,"

APCMET-Emerging Energy Technology Perspectives - A Sustainable

Approach, ISBN: 978-93-83083-73-2, New Delhi, 2014.

[3] N. Maharjan, S. Chitrakar, R. Koirala, “Design of Reversible Pump

Turbine for its prospective application in Nepal”, International Journal

of Scientific and Research Publications, 2014.

[4] Eltvik, M.,Thapa, B.S., Dahlhaug, O.G., and Gjosaeter, K.,

“Numerical analysis of effect of design parameters and sediment

erosion on a Francis runner”, Fourth International Conference on

Water Resources and Renewable Energy Development in Asia,

Thailand, 2012

[5] IEC-60193 document, “Guideline for model testing of Hydraulic

Turbines and Pumps”

BIOGRAPHIES

Mr. SaileshChitrakar is currently working as a Project Co-ordinator in

Turbine Testing Lab. He completed his Masters from a Erasmus Mundus

Program in Turbomachinery and Aeromechanics from Royal Institute of

Technology, Sweden and University of Liege, Belgium.

Mr. Ravi Koirala is a graduate of Mechanical Engineering from

Kathmandu University. He is currently working as a Researcher in Turbine

Testing Lab.

Mr. NirojMaharjan is a graduate of Mechanical Engineering from

Kathmandu University and past Researcher in Turbine Testing Lab.

Mr. NikhelGurung is a graduate of Mechanical Engineering from

Kathmandu University and past Researcher in Turbine Testing Lab.

Mr. Bishnu Prasad Aryal is a graduate of diploma in Mechanical

Engineering from BTI. He is currently working as a Technician in Turbine

Testing Lab.

design and development of a reversible pump turbine test rig

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