“recent activities at kathmandu university

1Kathmandu University [email protected]

“Recent Activities at Kathmandu University

for Minimizing Sediment Erosion in

Hydraulic Turbines”

Biraj Singh Thapa, PhD

Faculty In-Charge, Turbine Testing Lab

Asst. Professor, Department of Mechanical Engineering

Kathmandu University, Nepal

[email protected]

01, June 2018

mailto:[email protected]


Area: 147,181 km²

Population: 29 Million;

Growth rate: 1.24%;

Infant mortality rate: 28.9 /1,000

Life expectancy: 70 yrs. (60 yrs. in 2001)

Languages: 123 as mother tongue

Religions: 10 Major. Hindu 81%;

Buddhist 9%

Literacy rate: 63.9%

GDP per Capita: USD 730

(China: USD 8,123 )

Electricity consptn. per capita: 140 kWh

(China 4,000 kWh)

Nepal: Some Facts


The Water Tower of Asia

3

RiverLength

(km)

Fall

(m)

Avg flow

(m3/s)

Gross

(GW)Built%

Yellow 5464 4800 2571 28 6.1

Yangtze 6300 5042 30166 197.24 53.4

Mekong 4350 5224 16000 53

Salween 2815 5350 4978

Irrawaddy 2170 147 13000 25.3 15

Brahmaputra 2900 5210 19300 206

http://www.21stcentech.com/climate-change-impact-major-rivers-asia/

Glaciers are twenty times of the European Alps

Feeds 1.5 billion people in nine countries.

Koshi 720 3500 2166 22.35 <0.5

Gandaki 630 6268 1760 20.65 <0.5

Karnali 1080 3962 2990 36.18 <0.5

Ganges 2525 3892 16648 13 14.2

Sutlej 1500 4575 500

Indus 2900 4255 6600

Wikipedia, 2016

www.meltdownintibet.com


Hydropower Development Trends

1911, Nepal

Pharping Hydro Power Project

2*250 kW

2017: 0.8 GW (1.7% of TF)

1912, China

Shilongba Hydroelectric Power Station

2*240 kW

2017: 331 GW (40% of TF)

2002, Nepal

Kaligandaki A Hydroelectric Power Station

144 MW

2003, China

Three Gorges Dam Power Station

22,500 MW

Nepal lacks the experience for building a larger scale hydropower plants


Status of Hydropower Development in Nepal

Ref: Department of Electricity Development, Government of Nepal, 2017

Hydropower Development Opportunities

Some major hydropower projects that are in

advanced stage of development in Nepal

S.N. ProjectsCapacity

(MW)

1 Budhi Gandaki Hydropower Project 1,200

2 Upper Karnali Hydropower Project 900

3 Arun III Hydropower Project 900

4 Tamakoshi III 650

5 Upper Marsyangdi II 600

6 West Seti 750

7 Nalsingad Hydropower Project 410

8 Dudhkoshi Hydropower Project 300

9 Upper Trishuli 1 Hydropower Project 216

Total 5,926

Nepal need to generate hydropower development professionals and technicians

S.N.Summary status of

hydropower development

No. of

projects

Capacity

(MW)

1 Completed projects 80 937.31

2 Projects under construction 57 4935

3Issued construction

licenses for generation

148 4322.59

4 Issued survey licenses 289 13397.85

5Application received for

survey licenses

23 2084.16

Total (2-5) 24,739.56


Sediment erosion in Hydro turbines

23 MW*2 Francis runner at Chawa Powerplant, Chile

Ref: O.G. Dahlhaug

Runner inlet

Ref: Bhilaganga III HEP, 2016

8MW*3 Bhilaganga III HEP,

India

Guide vane

Ref: O.G. Dahlhaug

4 MW*3 Francis runner at

Jhimruk Hydroelectric

Center, Nepal

Runner outlet

Runner inletRunner outlet

Ref: Wikipedia

Ref: O.G. Dahlhaug

2.5 MW*2 Pelton runner

at Adhi Khola Hydropower

Plant, Nepal

Erosion in Pumps in Yello

River, China Ref: Qian


Kathmandu University (KU)

KU Vision Statement:

To become a world class university devoted to bringing knowledge and

technology to the service of mankind

Facts:

• Established July 1991

• Autonomous and self-sustainable public institution

• 7 Faculties: School of Engineering, Science, Management, Medical Sciences,

Education, Arts and School of Law.

• 4,000 students in constituent campuses 7,500 students are in affiliated colleges


KU’s Focus in Renewable Energy

Target Areas for R&D:➢ Hydropower

➢ Renewable Energy Technology (Solar, Biomass, Biogas)

Means:Platform Resources:

➢ Specialized Laboratories • Turbine Testing Lab

• High Voltage Lab

• Stove Testing Lab

• Geo Energy Testing Lab

➢ Center of Excellence • Aquatic Ecology Center

• Center for hydro turbine studies

➢ Training Centers • Technical Training Center

➢ Business Incubation Center

Academic Programs:

➢ Civil Engineering: Specialized in Hydropower

➢ Mechanical Engineering: Specialized in Hydropower

➢ Masters and Masters by Research in Civil,

Electrical, Mechanical and Environmental

Engineering

➢ PhD level Research in in Civil, Electrical,

Mechanical and Environmental Engineering


Early R&D of Hydro Turbines at KU

• R&D activities in several miniature turbine laboratories 2002-2005

a) Demo Francis turbine designed by student team

b) Flow visualization in Pelton bucket at miniature laboratory

c) 800 W Propeller Turbine designed and tested at Pico turbine

test laboratory

a b c


Erosion measurement test rig at KU

waterpower lab

Erosion Test Conditions

50 m/s 45o

Water jet

R&D at KU Against Sediment Erosion (2002-2005)



RDA Cavitation and Erosion study Erosion test of HVOF coating Erosion patter generated by sand erosion

a. Raw image of sand

particles

b. Cropped image

of single sand

c. Edge boundary of

single sand

d. Shape and size distribution

of sediment particles

a. c.b. d.


Design Optimization of Francis Turbine (2010-2012)

Numerical study of design optimization

Design 1 Design 2 Reference


Laboratory Experiments on Erosion Testing

• RDA at KU was used to quantify the

erosion rates in model blades

• Both reference and optimized designs of

Francis runner were tested

Rotating Disc Apparatus


Turbine Testing Lab at KU (2011)

Specifications:

• 30 m Open System Head

• 150 m Closed System Head

• 500 l/s Maximum Flow

• 300 kW Maximum Testing Capacity

• 300 m3 Lower Reservoir

• 100 m3 Upper Reservoir

• 5000 kg EOT Crane Capacity

Inaugurated on 10 November 2011 by

then Norwegian Ambassador to Nepal

Total USD 1.3 Million

www.ku.edu.np/ttl

http://www.ku.edu.np/ttl


Development of sediment erosion resistant Francis turbine

Stay ring with stay vane Spiral Casing Sections

Casted Runner Blades

Guide vanes

Assembly of the runner blades

Turbine in test rig at TTL

TTL: A Milestone for Design of Francis Turbine

Complete runner

CAD Model

Hydraulic Design and Optimization


Effects of sediment erosion in guide vanes of Francis turbine


Francis turbine

Operational range of Francis turbine

Spiral Casing

Draft Tube Cone

Governing Ring

Guide Vanes

Stay Vanes

Runner

Labyrinth

seals

Stay Ring

Lower Cover

Upper Cover

Tu

rbin

e S

ha

ft

Svartisen Power Plant, Norway

Francis turbine Components


Guide vane

250 MW*6 Francis turbine at

Nathpa Jhakri Powerplant, IndiaRef: H.K. Sharma, 2010

Cover Plate

48 MW*3 Francis turbine at Kaligandaki

A Hydroelectric Center, Nepal, Ref: B. Chhetri, 2013

Runner

outlet

Turbine design philosophy and challenges

Research ProblemSediment Erosion = f(Velocity3)


Erosion of GV trailing edge

A

C

B

D

Flow

Ref: R. Koirala, B. Thapa, H. P. Neopane, B. Zhu, and B. Chhetry, "Sediment erosion in guide vanes of Francis turbine:

A case study of Kaligandaki Hydropower Plant, Nepal," Wear, vol. 362–363, pp. 53-60, 2016.

Formation of GV clearance gap Measurement locations

Clearance gap in GV trailing edgeClearance gap in GV leading edge

545

mm

Problem status


Dry clearance gap from design

Flow with sediments causes erosion

Increases the size of the gap

Leakage flow due to pressure difference Disturbances in the

main flow

Reduction in efficiency

Increase in erosion

Research hypothesis


To study the effects of sediment erosion in hydro turbines, with the focus on the flow around the guide vanes of a low specific speed Francis turbine.

The specific objectives of this work are:

• Investigate the characteristics of leakage flow between the guide vanes and the cover plates

• Investigate effects of the leakage flow on velocity distribution in the distributor

GV clearance gap Erosion at runner inlet

Research objectives


Experimental methods


Control parameters for design optimization

Parameters Symbol Unit Value

Tangential velocity at runner inlet Cu-Rin m/s 40.72

Radial velocity at runner inlet Cm-Rin m/s 9.7

Velocity Components in Francis turbine

Design & optimization of cascade

Design optimization of flow cascade


Average discharge = 0.155 m3/s (±0.15%)

Velocity at runner inlet (Vref) = 33.23 m/s

Lowest pressure inside test section = 213.8 kPa

The test setup

The Waterpower Laboratory

Norwegian University of Science and Technology

Trondheim, Norway


11 pressure taps along

mid span of TGV

Pressure measurements at TGV mid-span

14 pressure taps at wall along TGV

pressure and suction surfaces

Pressure tap at

runner inlet position

Test section cover plate

Pressure measurements at TGV wall

Sampling rate = 5 Hz

Min. number of samples = 1000

Maximum uncertainty = ±0.05%

Pressure measurements


PIV measurement section and positons

Trigger rate = 4 Hz

Time delay (dt) = 75 μs

Spatial resolution = 4.7 mm

Min. number of image pairs= 100

PIV Measurement span relative to runner blade

Clearance gap size= 0, 0.5, 1.5, 2, 3 mm

GV profile design= NACA 0012

Velocity measurements


Unprocessed PIV image of flow field Distribution of bad vectors in flow field

PIV approach


PIV Convergence tests

……. C-RinRef

PIV measurement repetition tests

PIV approach


Results and Discussions


Flow around GV-Reference Case


Velocity vectors along GV mid-span Velocity vectors along CG 2 mm

Effects of clearance gap on flow field


Pressure along GV surface

Pressure difference between GV surfacesTorque on GV shaft

Velocity vectors along CG-2 mmIntensities of crosswise velocity from CG

Crosswise leakage flow from CG

Pressure distributions and effects


Flow conditions at runner inlet for CG 2 mm

𝑹𝒆𝒍𝒂𝒕𝒊𝒗𝒆 (𝒓𝒆) =𝒇𝒍𝒐𝒘 𝒑𝒂𝒓𝒂𝒎𝒆𝒕𝒆𝒓 𝒘𝒊𝒕𝒉 𝑪𝑮

𝒇𝒍𝒐𝒘 𝒑𝒂𝒓𝒂𝒎𝒆𝒕𝒆𝒓 𝒘𝒊𝒕𝒉𝒐𝒖𝒕 𝑪𝑮

Effects on ‘Cu’ Effects on ‘Cm’ Effects on ‘W’

Effects on ‘β’


Vorticity due to leakage flow from CG 2 mm

measured at 4 mm away from walls

Vortex filament

Guide vane

Flow channel

Observation of vortex filament from CG 2 mm

Study of vorticity


Vortex flow from CG 2 mm

GV

Vortex observed

in the cascade

Clearance gap

Runner blade

Study of vorticity


Symmetric NACA profile for guide vanes

High pressure difference towards trailing edge

Erosion in trailing edge and secondary flows

Increase in clearance gap, inducing strong crossflow

Higher relative velocity and lower tangential velocity

Higher erosion and lowered runner efficiency

Explanation of observations


NACA 2412 at 0.5mm NACA 4412 at 0.5mm NACA 0012 at 0.5mm

Velocity (m/s), PIV

a) b) c)

At designed condition, the vortex from leakage flow in NACA4412 is straight

downstream of the trailing edge, which inferred no cross flow through the gap.

Alternative design of GV


Vortices, CFD

At -5 deg

At 5 deg

At 0 deg

Upgrading to 3 GV rig

To enable testing in different

opening angles

To make the velocity field

more periodic – more similar

to real turbines

NACA0012 NACA0012 NACA4412NACA4412

NACA0012 NACA4412

Development of three GV cascade


• Francis turbines designed with standard methods are not

suitable for sediment-laden projects

• Design of guide vane can play important role to minimize

sediment erosion in turbine components

• Guide vane clearance gap should never reach to critical size

• Choice of guide vane axis location should be carefully done in

sediment- laden projects

• More studies are necessary to make future market sustainable

Recommendations


Thankyou for your kind attention

References to the original work:

1. B.S. Thapa, O.G. Dahlhaug, B. Thapa, “Flow measurements around guide vanes of Francis turbine: A PIV

approach”, Renewable Energy (2018), vol. 126, 177-188.

2. B.S. Thapa, O.G. Dahlhaug, B. Thapa, “Effects of sediment erosion in guide vanes of Francis turbine”, Wear

(2017), vol 390–391, 104-112.

3. B.S. Thapa, O.G. Dahlhaug, B. Thapa, “Sediment erosion induced leakage flow from guide vane clearance gap in

a low specific speed Francis turbine”, Renewable Energy (2017), vol. 107, 253-261.

4. B.S. Thapa, C. Trivedi, and O. G. Dahlhaug, “Design and development of guide vane cascade for a low speed

number Francis turbine,” J. Hydrodynamics, Ser. B (2016), vol. 28, 840-847.

5. B.S. Thapa, O.G. Dahlhaug, B. Thapa, “Sediment erosion in hydro turbines and its effect on the flow around

guide vanes of Francis turbine” Renewable and Sustainable Energy Reviews (2015), vol. 49, 1100-1113.

6. B.S. Thapa, B. Thapa, O.G. Dahlhaug, “Current research in hydraulic turbines for handling sediments”, Energy

(2012), Vol. 47, vol. 1, 62–69.

7. B.S. Thapa, B. Thapa, O.G. Dahlhaug, “Empirical modelling of sediment erosion in Francis turbines, Energy

(2012), Vol. 41, vol. 1, 386-391.

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