Description of the research subjects

The Department of Hydraulic Machinery, established on the 1st March 2007, continues

research works formerly conducted in the Department of Hydraulic Turbo machinery Tests

and Diagnostics and partly in the Department of Cavitation and Hydraulic Machinery Design,

which were in organization structure of The Centre for Mechanics of Liquids until the end of

February 2007 year. At the present moment Department currying out fundamental and applied

research works in the areas of design, operation and diagnostic tests of hydraulic

turbomachinery as well as modelling unsteady liquid flows in closed conduit and around

bodies.

Development of numerical methods for analysis and design of flow systems of hydraulic

turbines and impeller pumps, investigation on mathematical description of phenomena and

unsteady processes in hydraulic machines flow systems and improvement in the technique of

flow rate measurements in hydrotechnical and hydropower machines and devices are

comprise research subjects cultivated in the Department for longer time. These subjects are

essential for hydropower engineering and especially for small hydropower plants (SHP)

which are renewable energy sources. So far untapped hydropower potential of polish rivers

relates in great fraction to the low heads. In order to rationally take the advantage of possessed

potential it is necessary to develop relatively high efficient and inexpensive hydraulic turbines

constructions. Trying to face the needs of SHP in the Department there is an aspiration to

work up an special construction of small hydraulic turbines appropriate for low and ultra low

heads which would be characterized by high energy efficiency and very low production cost.

This study will be based on modern technique and methodology including three dimensional

computations of the liquid flow through turbine blade systems. Until now, collected were

abundant practical skills in designing small hydraulic turbines and comprehensive experience

of analyzing two dimensional flow through their blade systems, as a basis for new design

methods, moreover earlier began works on three dimensional flow analysis are intensively

developed .

It is planning to develop own original software for three-dimensional flow modelling by

means of vortex singularities method multiple validated in ship propellers applications. In

order to better understand phenomena appearing in liquid flow and to confirm reliability of

developed computer programs the Departments’s laboratory rigs will be exploited which

could be specially modernized and build up within bounds of possibility.

Primary purpose of research works concerning transient phenomena in flow systems of

hydraulic turbines and impeller pumps is improvement and development of numerical

methods for prediction the course of these phenomena. Practical importance of elaborated

methods is related to counteraction unfavorable conditions as excessive pressure changes

produced by water hammer effect or induced by vortex shedding under resonance conditions

severe increase in vibration amplitude of flown past elements. Such phenomena reduce

working life and operational reliability of elements of fluid-flow hydraulic systems and often

pose a serious threat of substantial failures. As especially dangerous situations taking place

in hydraulic pipeline systems should be consider cases when transient pressure decrease

results in appearance of cavitation zones, which are regions of liquid stream discontinuity.

Such situations can occur during quick opening/closing of valves or starting/stopping the

impeller of pumps or hydraulic turbines,

when as a consequence of wave processes produced by water hammer in the closed conduits

pressure at some section drops below its critical value, close to liquid evaporation pressure of

at a given temperature. Cavitation zones which appear during this process die away after some

time. Usually there are multiple emergence and disappearance of these zones. The

phenomena occurring under this conditions – i.e. transient cavitation or liquid column

separation – are almost always accompanying by rapid pressure changes which are reasons for

a large number of failures and occasionally total damages to the elements of the hydraulic

system. Avoidance or partial reduction of such changes could in crucial manner influence

upon increase augmentation of working life and operational reliability of flow systems

elements. Current knowledge concerning predictability of these phenomena is still

unsatisfactory therefore require further investigations.

In its activity the Department holds a wide collaboration with industry. For the most part they

are the companies from the hydropower sector for which various research works and practical

engineering applications are made. These works encompass efficiency tests of hydraulic

turbines and impeller pumps using advanced measurements techniques, design of small

hydraulic turbines, investigations and evaluation of dynamic state of hydraulic units with

determinations theirs durability and working life, as well as technical expert opinions for

hydropower industry and other areas of the economy related to the problems of ascertainment

of causes of breakdowns and failures, preparation of devices and equipment for continuous

flow rate measurement in hydraulic turbines, preparation of laboratory rigs for investigation

on water power phenomena for outer partners.

The whole selection of research topics continued by the Department stem primarily from the

thorough diagnose and current needs of the waterpower engineering. Its topicality is

confirmed by considerable number of direct contracts with hydropower plants to research and

service works, and also large number of technical consultancies and expert opinions which

were given to investors and users of small hydro power units and for the others interested in

the development of hydro-energetic power industry in Poland. Advanced in theoretical

research works and collected experience enable to undertake more and more complicated

tasks set by domestic and foreign customers.

Research activity of the Department is perfectly placed in current polish and european

scientific and economic trends.

The offers list of research works and expert technical opinions for industry:

CONCEPTS OF INSTALLATION AND DESIGNS OF SMALL HYDRAULIC TURBINES,

IMPELLER PUMPS IN TURBINE REGIME

Example 1: The concept of small hydraulic turbine with propeller runner at siphon

installation - the Jaracz Hydropower Plant

Example2: Machine for energy recuperation in industrial installations

Pressure-reducing valve Installation conduit

T

Turbine Main valve

Zawór główny By-pass valve Valves coupling

Schematic diagram of impeller pump application, to run in reverse as turbine, in order

to energy recuperation which is losing in industry installation -- energy is wasted at

pressure-reducing valve as a consequence of throttling of the flow.

1510

1521

1526

n=1532

1515

n=1505

0.00

0.25

0.50

0.75

1.00

1.25

1.50

1.75

2.00

2.25

2.50

0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Q t/Q p [-]

,

Ht/

Hp [-

]

sprawność

spad H t /Hp

Optymalne parametry pompy

przy n = 1500 obr/min:

H p = 16 m sł. wody

Qp = 0.056 m3/s

Operation characteristics of pump 150 PJM 250 in turbine regime

TECHNICAL STATE ASSESSMENTS, TECHNOLOGIES

Examples:

Evaluation of technical state of flow systems of hydraulic turbines

Extension of working life of flow systems of hydraulic turbines and impeller pumps,

for instance by reinforcement the most strained constructional elements of such

systems

Evaluation of strength and working life of derivation pipelines supplying hydraulic

turbines

Evaluation of vibration state of rotating systems of hydraulic units

0.5 20.5 40.5 60.4 80.4 100.4 120.3 140.3 160.3 180.2 200.2 MPa

Case without additional reinforcement. Reduced stress (according to Huber-Mises hypothesis) in

shell of turbine branching – outer side, pressure load 415 kPa (for linear-elastic material).

0.308 11.68 23.05 34.41 45.78 57.15 68.52 79.89 91.26 102.6 114.0 MPa

Reduced stress (according to Huber-Mises hypothesis ) in shell of turbine branching no. 1

fortified with a fin (for linear-elastic material).

Strengthening fin at pipeline branching

INVESTIGATION OF POWER PROPERTIES (EFFICIENCY MEASUREMENTS) AND

DYNAMIC STATE OF HYDRAULIC UNITS IN HYDROPOWER PLANTS

Examples:

Field guaranty and acceptance tests (efficiency measurements) of hydraulic

turbines

Efficiency measurements of hydraulic turbines

Commissioning tests of hydraulic units after construction, modernization or

overhaul

Dynamic state tests of hydraulic units – measurements and evaluation of vibration

level in constructional elements, noise level and pressure pulsation under various

operation conditions

74

76

78

80

82

84

86

88

90

92

94

30 40 50 60 70 80 90

eff

icie

ncy o

f tu

rbin

e

[%]

turbine no. 1 (nonmodernized)

turbine no. 2 (modernized)

90

110

130

150

170

190

210

230

30 40 50 60 70 80 90 Pm [MW]

dis

ch

arg

e

[m3/s

]

turbine no. 2 (modernized)

turbine no.1 (nonmodernized)

Power characteristic of hydraulic turbines determined for one effective head on the

basis of test conducted using Gibson method

OPERATION INVESTIGATIONS OF PUMPI NG SETS -- EFFICIENCY AND FLOW RATE

MEASUREMENTS

pump systems and pumping stations of cooling water in conventional and

heatpower plants

preheated water pumps in heatpower plants

flow systems on marine ships

10

12

14

16

18

20

22

5000 7000 9000 11000 13000 Q [m 3 /h]

Hp

[m]

total head as a function of discharge

0.5

0.6

0.7

0.8

0.9

5000 7000 9000 11000 13000

Q [m 3 /h]

[-]

pump efficieny as a function of discharge

Operation characteristics of network water pump determined in one of the heatpower

plant (ultrasonic method of flow rate measurement)

TECHNICAL EXPERT OPINIONS

Determination of breakdown and failure causes of hydraulic machinery and devices

(cavitation failure, damages caused by destructive effect of water hammer, resonant

phenomena, and others).

Examples:

determine the causes of excessive hydraulic unit shaft vibration

determine the causes of shaft cracking of impeller pumps

recognize the causes of penstock rupture

recognize the causes of cracking of cut-off valves housing in various hydraulic flow

systems

control and calibration of ultrasonic flowmeters installed in derivation pipelines of

hydropower plants and other hydrotechnical objects

Disrupted penstock in the Łapino Hydropower Plant

Main scope of works :

In order to evaluate the technical state of the penstock after the failure and to determine the

causes of its burst, the case was subject to an extensive investigation, covering among others:

- non-destructive tests of the preserved penstock shell with a particular focus on the weld

joints,

- material tests of the broken penstock shell,

- analysis of the stress in the shell of the broken penstock section,

- analysis of hydraulic transients under conditions of failure,

- elaboration of guidelines for repair of the penstock and further operation of the power plant.

FLOW RATE MEASUREMENTS IN HYDROPOWER PLANTS

Examples:

preparation and application of the water hammer method (Gibson method) for flow

rate measurement in flow systems of hydraulic turbines and pump-turbines

development, fitting up and starting up the devices for continuous water flow rate

measurement in hydraulic turbines (Winter-Kennedy method and ultrasonic method)

Example of water hammer method (Gibson method ) application

Schematic diagram of supply system of turbines under investigation with marked

hydrometric sections using (which were used) in Gibson method

Localization of pressure taps at each pipeline section 1-1 and 2-2.

60º

10 m

Section 1-1 and 2-2

Manifold

Pressure tap

>3D 2D 2D

1-1 2-2

turbine no. 1

turbine no. 2

tower

reservoir butterfly

valvezawór

motylowy

Waterproof housing with pressure difference transducer installed inside.

Recorded and calculated time changes of values related to flow discharge measurement by

means of Gibson method

0

20

40

60

80

100

80 90 100 110 120 130 140

Y [

%]

Y - recorded wicket gate

opening

-4

0

4

8

12

16

80 90 100 110 120 130 140

Dp

1-2

, Dp

f [k

Pa

]

Dp f - calculated pressure

drop caused by friction in

penstock between sections

1-1 and 2-2

Dp1-2 - pressure difference

measured between penstock

sections 1-1 and 2-2

0

30

60

90

120

150

180

210

80 90 100 110 120 130 140

time t [s]

Q [

m3/s

]

Q - flow rate calculated

according Gibson method

venting valve

from manifold

in section 2-2

from manifold

in section 1-1

pipe with signal

cable inside

COMPUTATIONS OF WATER HAMMER PHENOMENA IN FLOW SYSTEMS OF

HYDRAULIC TURBOMACHERY

Examples:

optimisation of the wicket gate closing procedure in order to protect supply

pipeline form the excessive pressure increase, and turbine generator from the

excessive rotational speed increase,

analysis of various methods of the water hammer effects (mitigation or

attenuation) in order to choice the most advantageous technical solution,

reduction of the excessive pressure pulsation produced by water hummer in fluid-

flow system of pumps and turbines,

control of transient states of hydraulic machines in order to counteract the

unfavorable effects of water hammer.

Exemplary analysis of by-pass valve application in order to diminish water

hammer level

Supply pipeline

Draft tube By-pass valve

Zawór upustowy

Hydraulic turbine

Cut-off valve

odcinający

Down

rservoir

Upper

reservoir

Schematic diagram of by-pass valve application in hydraulic turbine system

1.2

1.3

1.4

1.5

1.6

1.7

0.00 0.05 0.10 0.15 0.20 0.25

D u [m]

pm

ax/p

0,

nm

ax/n

n [-

]

T k = 9 s T k = 15

s

T k = 7 s

p max /p o

n max /n n

without zamyknia wicket gates

closing

Maximum pressure in pipeline (pmax) and maximum rotational speed (nmax) versus by-pass valve

diameter Du for various closing times of wicket gates Tk

CONSTRUCTION OF LABORATORY RIGS Example:

Small size laboratory test rig for studying hydraulic transient in pipe systems with

measurement equipment.

Schematic diagram of laboratory rig for water hammer phenomena

investigation

1. Water-air reservoir, 2. Long pipeline winded up on the reel, 3. Quick closing valve,

4. Control valve, 5. Static pressure transducers, 6. Manometer or pressure gage

transducer with display unit, 7. Electromagnetic flowmeter.

1

6

2

7

5

4

5

4

Partially view of laboratory rig for investigation on pressure wave

propagation in closed conduit

2 – measurement pipeline (copper), 3 – steel reel, 4 – C-shape bar to fasten pipeline,

5 – supports of measurement pipeline, 6 – cutoff valve (ball valve), 7 – spring drive

of cut-off valve, 8 – control valve, 9 – pressure transducer, 10 – turbine flowmeter,

11– potentiometric transducer to record closing of cut-off valve.

2

3

4

5

6

5

7

5

1

1

5

8

5

1

0

9