Project Final

Malampuzha Hydel Plant Project Report’ 08- 09

Dept. of Mechanical Engg Page 1 Govt. Engg. College, Thrissur

1. I�TRODUCTIO�

Hydro power is the largest renewable energy resource being used

for the generation of electricity. In India, hydro power projects with a

station capacity of up to 25 megawatt (MW) each fall under the category

of small hydro power (SHP). India has an estimated SHP potential of

about 15 000 MW, of which about 11% has been tapped so far.

Here we take up an analysis of the technical inefficiency, time and

cost overruns in the Malampuzha mini Hydel power project. This is of

very significance in the present context of arguments by the government

in favour of private sector participation in power generating capacity

addition, under the pretext of a resources crunch. The government is said

to be under a tight constraint of severe funds scarcity and hence incapable

of undertaking new projects for power development. However, we will

find that this argument is flimsy to the extent that the government is

actually over-spending on each of the projects undertaken.

Each project involves immense cost overrun, and the machines

implemented are of inferior quality. Had the government been able to

implement each project efficiently within the normally expected

constraints of time and cost, then it could have saved huge resources and

hence undertaken a large number of additional projects. The problem is in

the inefficiency of management, to forecast the needs and to find the best

for the state, coupled with the political economy of corruption. This

paper, has the limited objective of bringing into light this aspect.



2. HISTORICAL PERSPECTIVE

Evolution of Modern Turbine from the Water Wheel

The water turbine has a rich and varied history and has been

developed as a result of natural evolutionary process from the

waterwheel. The water turbine was originally used for direct drive of

machinery; its use for the generation of electricity is comparatively

recent. Much of its development occurred in France. England had cheap

and plentiful sources of coal which sparked the industrial revolution in

the eighteenth century, but Nineteenth century France had only water as

its most abundant energy resource. To this day houille blanche ‘ white

coal’ is the term for water power.

Bernard Forest de Belidor, a Hydraulic and Military Engineer

authored (1737-1753) the monumental 4 Volume architecture

Hydraulique, a descriptive compilation of Hydraulic Engineering

information of every sort.

The water Wheel described by Belidor departed from convention

by having a vertical axis of rotation and being enclosed in along

cylindrical chamber in approximately one meter in diameter. Large

quantities of water, supplied from a tapered sluice at a tangent to the

chamber, entered with considerable rotational velocity. This pre-swirl

combined with the weight of water above the wheel was the driving

force. The original tub wheel had an efficiency of only 15%-20%.

Water Turbine development proceeded on several fronts from

1750- 1850. The classical Horizontal-axis waterwheel was improved by

such Engineers as John Smeaton (1724-1792) of England, who used the

first avowed model experiments in this endeavor and also played an

important role in windmill development, and Jean Victor Poncelet (1788-



1867) of France. These improvements resulted in waterwheels having

efficiencies in the range of 60% -70 %.

At the same time reaction turbines were being considered by

several workers. The great Swiss Mathematician Leonhard Eular (1707 –

1783) investigated the theory of operation of these devices. A practical

application of the concept was introduced in France in 1807 by Mannoury

de Ectot (1777 – 1822). His machines were, in effect, radial outward-flow

machines. The theoretical analysis of Claude Buridin ( 1790 – 1893), a

French professor of mining engineering who introduced the word

‘turbine’ in engineering terminology, contributed much to our

understanding of shock-free entry and exit with minimum velocity as the

basic requirements for high efficiency

A student of Buridin, Benoit Fourneyon (1802 – 67), put his

teacher’s theory to practical use, which led to the development of high

speed outward flow turbines with efficiencies of the order of 80 percent.

Fourneyron developed some 100 turbines in france and elsewhere in

Europe. Fourneyron turbines, successful as they were, lacked flexibility

and were only efficient over a narrow range of operating conditions. The

modern Francis turbine is the result of this line of development. At the

same time, European engineers addressed the idea of axial flow

machines, today which are represented by propeller turbines of both fixed

pitch and the Kaplan type.

Just as the vertical axis hub wheels of Belidor evolved into

modern reaction turbines of the Francis and Kaplan type, development of

the classical horizontal axis waterwheel reached its peak with the

introduction of impulse turbine. The seeds of development were sown in

1826 when Poncelet described the criteria for an efficient waterwheel.

These ideas were cultivated in the late nineteenth century by a group of

California engineers that included Lester A. Pelton (1829-1908).



His name was given to the pelton wheel, which consists of a jet or

jets of water impinging on an array of specially shaped buckets closely

spaced around the periphery of a wheel. Thus, the relatively high speed

reaction turbines trace their roots to the vertical axis tub wheels of

Belidor, where as the pelton wheel can be considered as a direct

development of the more familiar horizontal axis waterwheel.



3. MALAMPUZHA HYDEL PROJECT

– A� OVERVIEW

Malampuzha, one of the first projects planned in the State to

generate electricity from water let out from an irrigation dam. The

contract for the design, supply and installation works were awarded to a

private firm which allegedly had no previous experience in such projects.

A mini Hydel project of 2.5 MW with an annual generation of 5.6

MU, this scheme envisages construction of a power station on the

downstream side of the existing irrigation dam (owned by the State

PWD) to utilize the irrigation release. Started in 1987 and expected to be

online by 1989, this mini project is now expected to be commissioned ‘in

the near future’. After 12 years with a time overrun of about 10 years as

in 1999-2000, the capital cost was revised from the original Rs. 295 lakhs

to Rs. 679 lakhs – an increase of about 130 per cent. Now it has reached

an alarming value of 697 lakhs- a total increase of 136 percent!

The civil work was done by the KSEB. Though the company

started the erection work in 1992, it took as many as four years to attempt

at a trial run. However, during the trial run, some defects were noticed in

the butterfly valve. In 1997, another trial run was tried, but again during

the run, a valve disc got broken. In 2004 it was brought into operation but

after working for 200 days it malfunctioned. The shaft of the turbine was

broken, and from that day to present it remains non-functional.



4. BASIC DEFI�ITIO�S

4.1 DEFI�ITIO� OF HEAD

4.1.1 Effective Head (�et Head)

The effective head is the net head available to the turbine unit for

power production. This head is the static gross head, the difference

between the level of water in the Forebay/impoundment and the tail water

level at the outlet, less the hydraulic losses of the water passage as shown

in Fig. 1.1. The effective head is used for all power calculations. The

hydraulic losses can vary from essentially zero to amounts so significant

that the energy potential of the site is seriously restricted.

In general a hydraulic loss of one velocity head (V2/2g) or greater

would not be uncommon. The hydraulic losses through the turbine and

draft tube are accounted for in the turbine efficiency.

4.1.2 Gross Head (Hg)

It is the difference in elevation between the water levels of the

forebay and the tailrace.

4.1.3 Maximum Head (Hmax)

It is the gross head resulting from the difference in elevation

between the maximum forebay level without surcharge and the tailrace

level without spillway discharge, and with one unit operating at speed no-

load (turbine discharge of approximately 5% of rated flow). Under this

condition, hydraulic losses are negligible and nay be disregarded.



4.1.4 Minimum Head (Hmin)

It is the net head resulting from the difference in elevation between

the minimum forebay level and the tailrace level minus losses with all

turbines operating at full gate.

4.1.5 Design Head (Hd)

It is the net head at which peak efficiency is desired. This head

should preferably approximate the weighted average head, but must be so

selected that the maximum and minimum heads are not beyond the

permissible operating range of the turbine. This is the head which

determines the basic dimensions of the turbine and therefore of the power

plant.

4.1.6 Rated head (Hr)

It is the net head at which the full-gate output of the turbine

produce the generator rated output in kilowatts. The turbine nameplate

rating usually is given at this head. Selection of this head requires

foresight and deliberation.

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4.2 CLASSIFICATIO� A�D TYPES OF TURBI�ES

Turbines can be either reaction or impulse types. The turbines type

indicates the manner in which the water causes the turbine runner to

rotate. Reaction turbine operates with their runners fully flooded and

develops torque because of the reaction of water pressure against runner

blades. Impulse turbines operate with their runner in air and convert the

water’s pressure energy into kinetic energy of a jet that impinges onto the

runner buckets to develop torque.

Reaction turbines are classified as Francis (mixed flow) or axial

flow. Axial flow turbines are available with both fixed blades (Propeller)

and variable pitch blades (Kaplan). Both axial flow (Propeller & Kaplan)

and Francis turbines may be mounted either horizontally or vertically.

Additionally, Propeller turbines may be slant mounted. Out of this we are

interested in Axial flow (Kaplan& Tubular) turbines only.

4.2.1 AXIAL FLOW TURBI�ES

Axial flow turbines are those in which flow through the runner is

aligned with the axis of rotation. Axial flow hydraulic turbines have been

used for net heads up to 40 meters with power output up to 25 MW.

However, they are generally used in head applications below 35 meters

Tubular turbine (S-type). S-turbines are used below 30 meters head and 8

MW capacity. Specific mechanical designs, civil construction, and

economic factors must be given full consideration when selecting among

these three axial flow turbine arrangements.



Propeller Turbines -

A propeller turbine is one having a runner with four, five or six

blades in which the water passes through the runner in an axial direction

with respect to the shaft. The pitch of the blades will be fixed. Principal

components consist of a water supply case, wicket gates, a runner and a

draft tube.

The efficiency curve of a typical fixed blade Propeller turbine

forms a sharp peak, more abrupt than a Francis turbine curve. Propeller

turbines may be operated at power outputs with flow from 40-105% of

the rated flow. Discharge rates above 105% may be obtained; however,

the higher rates are generally above the turbine and generator

manufacturers’ guarantees.

Kaplan Turbines (Vertical)

A Kaplan Turbine is one having a varying blade pitch. For these

units the peak efficiency occurs at different outputs depending on the

blade setting. An envelope of the efficiency curves cover the range of

blade pitch settings forms the variable pitch efficiency curve. This

efficiency curve is broad and flat. . The conventional propeller or Kaplan

(variable pitch blade) turbines are mounted with a vertical shaft.



Fig. 2: Kaplan turbine (vertical)

The vertical units are equipped with a wicket gate assembly to

permit placing the unit on line at synchronous speed, to regulate speed

and load, and to shutdown the unit. The wicket gate mechanism units are

actuated by hydraulic servomotors. Small units may be actuated by

electric motor gate operators. Variable pitch units are equipped with a

cam mechanism to coordinate the pitch of the blade with gate position

and head. Digital control envisages Control of wicket gates and blade

angle by independent servomotors coordinated by digital control.

Fixed blade units are less costly than variable pitch blade turbines;

however, the power operating ranges are more limited. Four blade



designs may be used up to 12 meters of head, five blade designs to 20

meters and six blade designs to 35 meters. In general, peak efficiencies

are approximately the same as for Francis turbines.

Many units are in satisfactorily operation from 60 to 140% of

design head. Efficiency loss at higher heads drops 2 to 5% points below

peak efficiency at the design head and as much as 15% points at lower

heads. Variable pitch propeller turbines without wicket gates are called

Semi Kaplan turbine.

Kaplan Features

• Simple designs for ease of erection and simple foundation details

• Low cost solutions for exploiting low head potential

• Water lubricated shaft bearing system

• Entire range of Kaplan runners available in three, four, five & six

blades

• Simplified interface with powerhouse structure to reduce overall

civil costs

Tubular turbines

Tubular or tube turbines are horizontal or slant mounted units with

propeller runners. The generators are located outside of the water

passageway. Tube turbines are available equipped with fixed or variable

pitch runners and with or without wicket gate assemblies. Performance

characteristics of a tube turbine are similar to the performance

characteristics discussed for propeller turbines. The efficiency of a tube

turbine will be one to two % higher than for a vertical propeller turbine of

the same size since the water passageway has less change in direction.



Fig 3: Tubular turbines (Horizontal Kaplan)

The performance range of the tube turbine with variable pitch blade

and without wicket gates is greater than for a fixed blade propeller turbine

but less than for a Kaplan turbine. The water flow through the turbine is

controlled by changing the pitch of the runner blades.

When it is not required to regulate turbine discharge and power

output, a fixed blade runner (propeller) may be used. This results in a

lower cost of both the turbine and governor system.. Several items of

auxiliary equipments are often necessary for the operation of tube



turbines. All tube turbines without wicket gates should be equipped with

a shut off valve automatically operated to provide shut-off and start-up

functions.

Tube turbines can be connected either directly to the generator or

through a speed increaser. The speed increaser would allow the use of a

higher speed generator, typically 750 or 1000 r/min, instead of a

generator operating at turbine speed. The choice to utilize a speed

increaser is an economic decision. Speed increasers lower the overall

plant efficiency by about 1% for a single gear increaser and about 2% for

double gear increaser. (The manufacturer can supply exact data regarding

the efficiency of speed increasers). This loss of efficiency and the cost of

the speed increaser must be compared to the reduction in cost for the

smaller generator. It is recommended that speed increaser option should

not be used for unit sizes above 5 MW capacity.

The required civil features are different for horizontal units than for

vertical units. Horizontally mounted tube turbines require more floor area

than vertically mounted units. The area required may be lessened by slant

mounting, however, additional turbine costs are incurred as a large axial

thrust bearing is required. Excavation and powerhouse height for a

horizontal unit is less than that required for a vertical unit.

Standard Tube turbines of Bharat Heavy Electrical based on

runner diameter is shown in Figure 2.



Fig. 4: Tubular Turbine

�omenclature

1. Runner

2. Main inlet valve

3. valve servomotor

4. stay valve

5. Runner chamber

6. Turbine bearings

7. Shaft seal

8. Draft tube

9. gear box

10. Generator

11. Generator bearing

12. Runner bearing



4.3 SPECIFIC SPEED (�s)

The term specific speed used in classifying types of turbines and

characteristics of turbines within types is generally the basis of selection

procedure. This term is specified as the speed in revolutions per minute at

which the given turbine would rotate, if reduced homologically in size, so

that it would develop one metric horse power at full gate opening under

one meter head. Low specific speeds are associated with high heads and

high specific speeds are associated with low heads. Moreover, there is a

wide range of specific speeds which may be suitable for a given head.

Selection of a high specific speed for a given head will result in a

smaller turbine and generator, with savings in capital cost. However, the

reaction turbine will have to be placed lower, for which the cost may

offset the savings. The values of electrical energy, plant factor, interest

rate, and period of analysis enter into the selection of an economic

specific speed.

Commonly used mathematically expression in India for specific speed

is power based (English System) is as follows:

�s = � √Pr ÷ (Hr) 5/4

Where N = revolutions per Minute

Pr = power in metric horse power at full gate opening – (1 kW =

0.86 metric hp)

Hr =rated head in m.

The specific speed value defines the approximate head range

application for each turbine type and size. Low head units tend to have a

high specific speed, and high-head units to have a low specific speed.



Flow based metric system for specific speed (Nq) used in Europe is given

by equitation below.

�q = �Q0.5÷H0.75

Where Nq = Specific Speed

N = Speed in rpm

Q = Flow in cubic meters/second

H = Net Head in meters

Specific speed (metric HP units) range of different types of turbines is as

follows:

Table 1: The range of specific speed for various turbines.

TURBI�ES SPECIFIC SPEED

Fixed blade propeller turbines 300 – 1000

Adjustable blade Kaplan turbines 300 – 1000

Francis turbines 65 - 445

Pelton Turbine 16-20 per jet*

Cross flow turbine 12-80 per jet*

* For multiple jets the power is proportionally increased

The basic graph between Specific speed Vs Head is given below

(Fig. 5)

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4.4 EFFICIE�CIES OF A TURBI�E (η)

The different types of efficiencies are

1. Hydraulic efficiency

2. Mechanical efficiency

3. Volumetric efficiency

4. Overall efficiency

4.4.1 Hydraulic efficiency ηh:

It is defined as the ratio of power given by water to the runner of a

turbine to the power supplied by the water at the inlet of the turbine. Thus

mathematically

ηh = Power delivered to the runner = R.P Power supplied at inlet W.P

Where R.P = runner power

W.P = water power

4.4.2 Mechanical efficiency – ηm

The power delivered by water is transmitted to the shaft of the

turbine. But due to the mechanical losses cent percent power won’t be

delivered at the shaft. The ratio of power available at the shaft to that

delivered to the runner is defined as the mechanical efficiency of the

turbine. Mathematically,

ηm = Power at the shaft of the turbine = S.P

Power delivered by turbine R.P

Where S.P= Shaft power



4.4.3 Volumetric efficiency – ηv

The volume of water striking the runner of a turbine is slightly less

than the volume of the water supplied to the turbine. Some volume of the

water is discharged to the tail race without striking the runner of the

turbine. Thus the ratio of the volume of the water actually striking the

runner to the volume of water supplied to the turbine is defined as the

volumetric efficiency.

Ηv = Volume of water actually striking the runner Volume of water supplied to the turbine

4.4.4 Overall efficiency – ηo

It is defined as the ratio of power available at the shaft of the

turbine to the power supplied by the water at the inlet of the turbine. It is

written as:

ηo = Volume available at the shaft of the turbine = S.P Power supplied at the inlet of the turbine W.P

S.P × R.P = ηh× ηm R.P × W.P

ηo= ηh× ηm



4.5 U�IT QUA�TITIES

In order to predict the behavior of a turbine working under varying

conditions of head, speed, output, and gate opening, the results are

obtained in terms of quantities which may be obtained when the head on

the turbine is reduced to unity. The conditions of the turbine under unit

head are such that the efficiency of the turbine remains unaffected. The

followings are the three important unit quantities which must be studied

under unit head:

i) unit speed

ii) unit power

iii) unit discharge

4.5.1 Unit Speed

The unit speed is defined as the speed of the turbine working under

a unit head (i.e. under a head of 1m). It is denoted by Nu

�u = � √H

Where N = Speed of a turbine under a head H

4.5.2 Unit Discharge

It is defined as the discharge of the turbine, which is working under

unit head (i.e. under a head of 1m). It is denoted by Qu. the expression for

unit discharge is given as

Qu = Q

√H

Where Q = Discharge through the turbine under a

head H



4.5.3 Unit Power

It is defined as the discharge of the turbine, which is working under

unit head (i.e. under a head of 1m). It is denoted by Pu. the expression for

unit discharge is given as

Pu = P H3/2

Where P = Power developed by a turbine under a head H

Use of unit quantities (�u, Qu, Pu)

If a turbine is working under different head the behavior of the

turbine can be easily known from the values of the unit quantities.

Let H1, H2 ,H3, H4, H5…be the different heads under which turbine

works

Then, �u = �1 = �2

√H √H

Qu = Q1 = Q2

√H √H

Pu = P1 = P2 H3/2 H3/2

Thus if the rated speed, rated discharge, rated head, rated power are

known then we can find out the unit quantities and there by find the

speed, discharge and power for different heads.



4.6 CAVITATIO� I� TURBI�ES

When the pressure in any part of the flow passage reaches

the vapour pressure of the flowing liquid, it starts vaporizing and small

bubbles of vapour form in large numbers. These bubbles (or vapour-filled

pockets or cavities) are carried along by the flow, and on reaching the

high pressure zones these bubbles suddenly collapse as the vapour

condenses to liquid again. Due to sudden collapsing of bubbles or cavities

the surrounding liquid rushes into fill them. The liquid moving from all

directions collides at the center of the cavity, thus giving rise to very high

local pressure, which may be as high as 686.7MN ̸ m2. Any solid surface

in the vicinity is also subjected to these intense pressures. The alternate

formation and collapse of vapour bubbles may cause severe damage to

the surface which ultimately fails by fatigue and the surface becomes

badly scored and pitted. This phenomenon is known as cavitation which

is found to occur in turbines as well as in various hydraulic structures

such as penstocks, gates, valves, spillways etc.

In reaction turbines the cavitation may occur at the runner

exit or the inlet to the draft tube where the pressure is considerably

reduced. Due to cavitation the metal of the runner vanes and the draft

tube is gradually eaten away in these zones, which results in lowering

the efficiency of the turbine. As such the turbine components should be

so designed that as far as possible cavitation is eliminated. In order to

determine whether cavitation will occur in any portion of the turbine,

D.Thoma of Germany has developed a dimensionless parameter called

Thoma’s cavitation factor σ which is expressed as

σ = ( Ha- Hv – Hs ) ̸ H 4.6.1



Where H is atmospheric pressure head; H is vapour pressure head; H is

suction pressure head (or height of runner outlet above tail race); and H is

working head of the turbine. Complete similarity in respect of can be

ensured if the value of σ is same in both the model and prototype.

Moreover it has reduced up to a certain value up to which its efficiency

n0 remains constant. A further decrease in the value of σ results in a

sharp fall in ηo. The value of σ at this turning point is called the critical

cavitation factor σc. The value for σc for different turbines may be

determined with the help of following empirical relationships:

For Francis Turbines

σc = 0.625 { Ns /380.78}2

For Propeller turbines

σ c = 0.28+{ (1/7.5) { Ns /380.78}3 } 4.6.2

For Kaplan turbines, values of σc obtained in the above equation

should be increased by 10%.

In the above expression Ns is in (r.p.m, kW, m) units. However if

Ns is in (r.p.m, h.p, m) units, the expression for σc would be as follows:

For Francis turbines

σc = 0.625 { Ns /444}2

For Propeller turbines

σ c = 0.28+{ (1/7.5) { Ns /444}3 }

Again for Kaplan turbines, value for σc obtained by the above

equation should be increased by 10%

4.6.1 Suction Specific Speed.

In addition to Thoma’s criterion the consideration of suction

specific speed provides another very useful criterion for establishing

similarity in respect of cavitation in the turbines. The suction specific



speed S may be defined as the speed of a geometrically similar turbine

such that when it is developing a power equal to 1 kilowatt (or in metric

units equal to 1 metric horse power ) the total suction head Hsv is equal to

1m (in absolute units). According to this definition the expression for

suction specific speed may be obtained by replacing H, given in the

equation for the specific speed, by total suction head Hsv. Thus

S = (N√P) ⁄ Hsv5/4 4.6.3

By having the same value of suction specific speed for the model

and the prototype turbines the similarity in respect of cavitation can be

established

The total suction head Hsv can be expressed as

Hsv = Ha− Hv –Hs 4.6.4

And hence from the equation 4.6.1

Hsv = σH 4.6.5

By substituting the value of Hsv in the equation 4.6.3, we get

S = (N√P) ⁄ (σ H)5/4 Or

σ = (Ns ⁄ S)4/5 4.6.6

Equation 4.6.6 represents the relation between the two parameters σ and

S, both of which are useful for establishing a similarity in respect of

cavitation in the model and prototype turbines. However, the concept of

suction specific speed is more commonly used in case of pumps.

Cavitation protection is an important criterion in Kaplan turbine

blade design. In Kaplan turbines cavitation occurs at a number of



different locations, notably at the blade leading edge, on the blade suction

side, in both tip and hub gaps and on the discharge ring. Cavitation can

result in frosting or pitting in the above-mentioned locations. Its severity

depends on design and operating regime of the machine. Cavitation itself

is primarily a local effect.

The discharge ring cavitation often occurs in a number of discrete

circumferential patches corresponding to the number of guide vanes. At

first sight this is surprising, because we assume that the low pressure

zones caused by the rotating blades are responsible for the cavitation.

Therefore any effect would be expected to occur at the entire

circumference of the discharge ring. Since that is not the case, we can

conclude that unsteady flow behavior driven by the rotor-stator

interaction of the guide vanes and blades have to be responsible for the

effect. Due to the various physical effects involved, unsteady two-phase

flow with highly locally refined meshes is required for the numerical

simulation of the Kaplan turbine cavitation phenomena

4.7 HYDRO-TURBI�E GOVER�I�G SYSTEM

Governor control system for Hydro Turbines is basically a feed

back control system which senses the speed and power of the generating

unit or the water level of the forebay of the hydroelectric installation etc.

and takes control action for operating the discharge/load controlling

devices in accordance with the deviation of actual set point from the

reference point. Governor control systems of all units suitable for isolated

operation are a feed back control system that controls the speed and

power output of the hydroelectric turbine. Water level controllers can be

used for grid connected units. Governing system comprises of following

sections.



a) Control section

b) Mechanical hydraulic Actuation section

The control section may be mechanical; analogue electronic or

digital. Actuator can be hydraulic controlled, mechanical (motor) or load

actuator. Load actuator are used in micro Hydel range; mechanical (motor

operated) may be used say up to 1000 kW unit size. Hydro actuators are

mostly used.

Figure 6: PLC circuit system

Type of Governor Control Section

• Mechanical Controller • Electro-Hydraulic Governor – Analogue Electronics • Electro Hydraulic Governor – Digital Governors

Electro Hydraulic Governor – Digital Governors

In digital governor, digital controller is used in turbine governing

system. This is also PID controller. Digital control hardware running an

application programme accomplishes the required control function with

this system. Digital controllers used for turbine governing system are

very flexible and can be used for functions not directly related to the

turbine governing control function. Present day trend is to use digital



governing control system in hydroelectric units. The major advantages of

microprocessor based system over the earlier analogue governors (based

on solid state electronic circuitry) are higher reliability, self diagnostic

feature, modular design, flexibility of changing control functions via

software, stability of set parameters, reduced wiring and easy remote

control through optical fibre cables. Microprocessor based governor

control system are capable of carrying out the following control functions

in addition to speed control during idle run , operating in isolated grid;

interconnected operation and islanding operation.

• Control the power output depending on variation in grid frequency

i.e load frequency control

• Joint power control of a number of generating units in a power station

• Power control as per water levels in Fore-bay and/or Tail-race

• Automatic Starting / Stopping by single command

• Fast response to transient conditions

• Control from remote place Supervisory Control And Data Acquisition

(SCADA)

Personnel Computers (PC) /Programmable Logic Controller

(PLC) based Digital Governors

Modern control schemes also utilise personal computers (PCs) in

conjunction with PLC control systems. The PCs are utilized with man-

machine interface (MMI) software for control display graphics, historical

data and trend displays, computerized maintenance management systems

(CMMS), and remote communication and control. In addition, the PLC

programming software is usually resident on the PC, eliminating the need

for a separate programming terminal implement or changes the PLC

software coding. A PC also can be used for graphical displays of plant



data, greatly enhancing operational control. Standard Microsoft-based

graphical display software packages are available for installation on a

standard PC. The software package can be utilized on the PC to create

specific powerhouse graphical displays based upon real-time PLC inputs.

These displays typically include control displays with select-before-

execute logical, informational displays for plant RTD temperatures, or

historical trending plots of headwater, tail water, and flow data. Modems

with both dial-out and dial-in capabilities can be located in the PC, the

PLC, or both to provide off-site access to plant information. These

modems may also be utilised to control the plant operation from a remote

location.

Programmable Logic Controller (PLC) type plant controllers with a

manually operated back up system combined with PC based SCADA

system are used as Governors and for Plant control and data acquisition.

This makes the system costly but reliability is stated to be good and can

be used for small hydro generation control. It is considered that dedicated

digital control systems which is digital P.C. based can perform all

functions of governing, unit control and protection as well as for data

storage and can be more economical, dependable and are being

manufactured in U.S.A., Europe, India and other countries. These

dedicated systems with back up manual control facility of speed control

in emergency by dedicated semi automatic digital controllers can be an

option and is also recommended for UNDP-GEF projects in India.

Monitoring and control and data acquisition system (SCADA system) can

be a part of the P.C. based digital governor and generation control

equipment. Provision of data storage of one month with 16 MB of Ram

memory and a 540 to 850 MB Hard Drive as part of the PC based

governing and control system should be provided. This data could be

retrieved on a floppy drive after one month for examination. As the



communication links develop the data can also be transmitted via a

Modem to a remote point for examination and supervisory control.

Auxiliary control normally forms a part of digital governor. It is further

recommended that water jet diverters of emergency closure of inlet valves

be provided to avoid over speeding to runaway in case of governor failure

emergency.



5. TECH�ICAL DESCRIPTIO�

5.1 GE�ERAL DETAILS

The turbine is horizontal shaft semi- Kaplan (tubular, S-shaped) of

standardized design with movable runner blades and fixed guide vanes.

The system has one elbow of cylindrical and straight axially symmetric

draft tube.

The turbine shell is a tubular type with 6 fixed guide vanes. For

mechanical stability of the Turbine, 2 sets of rods, welded to embedded

sole plates and a concrete block around the turbine casing is provided.

The runner of the Kaplan Turbine include a Hub made of cast steel 13/4

Chromium nickel S.S blade with 2 bush bearings

The shaft line is supported by a concrete pedestal and reinforced by

a third set of rods, located under the thrust bearing. It constituted by a

hollow shaft on the runner side bolted to the solid shaft on the Generator

side. The shaft line is oil immersed and never in contact with water.

The turbine has a simplified oil system with pump supplying oil to

the blade control mechanism under high pressure. The oil flows in the

bearing, then in the Turbine casing and finally in the tube which act as a

cooler. The oil is then directed to the thrust- block and to the upstream

bearing before returning to the oil tank.



Figure 8: Turbine’s major components

5.2 TURBI�E’S MAJOR COMPO�E�TS

5.2.1 Distributor

The distributor is embedded in concrete and welded at the upstream

side, to the elbow type inlet duct. A casing containing mechanical items is

held by six guide vanes. It also consist of a controllable blade runner, a

servomotor oil distributing system, a casing and a thrust block connected

by a tube inside which the shaft lines rotates. It also consists of a sliding

throat ring which is capable of retracting into the draft tube.



5.2.2 Shaft Line

The shaft line constituted by a hollow shaft on the runner side

bolted to the solid shaft on the generator side. The shaft on the runner

side forms the servo motor cylinder. The shaft line is supported by

spherical roller bearing. The thrust towards the downstream side due to

the pressure on the runner is taken by thrust bearing thrust block support

and clamping nut. The shaft line is oil immersed and never in contact

with water.

5.2.3 Runner

The runner includes a hub made of alloy steel.13/4 Chromium

Nickel S .S Blades with two bush bearings. Blade water tightness is

ensured by the lever connected to the blade by oil seal. The blades are

driven by the lever connected to the blade by cotter-pin. The motion is

ensured by a conventional Kaplan link and the stem system which

includes 4 connecting stem, 4 clevises and a bronze head (Bracket). The

power transmission to the shaft line is carried out by 4 keys. The runner is

arrested by a hydraulic / lock nut

The system operates as follows: the pressurization of the space

between the hub and the sealing ring nut put the shaft on the runner side

in tension. Then it is sufficient to tighten sealing ring lock nut manually

and to allow the pressure to drop to attain the required clamping

5.2.4 Shaft Seal

The seal is of mechanical type. It includes 2 mechanical seal rings

adhering to the seal support. This bronze part can slide depending on the

mechanical seal wear and tear. The casing sealing is ensured by oil seal

(Solosele G seal). The seal support and the mechanical seal ring are

forced against the friction plate by a spring ring and by the water



pressure. The mechanical seal leakage of water is recovered by a channel

passing through the arm and draining out through a 50 mm diameter pipe.

Even when the mechanical seal is worn out the seal support is supported

by butt-strap, thereby avoiding any contact between any fixed parts and

rotating parts

5.2.5 Blade Control System

The blades are controlled by the cross head motion. The cross head

is connected to the blade control system which acts as a piston head in the

shaft, on the runner side. The rotation forces due to the links and stem are

taken up by two guides on the runner cap. The oil pressure is applied to

either side of the piston through holes drilled in the shaft. The shaft

rotating pipes are connected to the distributor fixed pipes through a

system of three floating bush which are mounted on the shaft with a very

close clearance and intended to minimize oil leakage outside the blade

control system.

5.2.6 Oil Station and Oil Systems

The turbine includes two different oil systems whose supply is

ensured by hydraulic power pack and lubrication oil supply unit. When

blade operating order is given the solenoid valve is energized in one of

the directions and the oil flows to the servomotor through one of both

pipes. The servomotor oil return is directed into the solenoid valve

towards the system.

The lubricating oil supply unit ensure the 3 bar pressure that no

over pressure will never occur in the turbine. In this way, the lubricating

is never interrupted. The oil flows in the bearing, then in the Turbine

casing and finally in the tube acting as a cooler. The oil is then directed to

the thrust block and to the upstream bearing before returning to the oil



tank. A pressure gauge on the thrust block permits to visualize the

internal pressure of the lubricating system in the turbine.

5.2.7 Draft Tube

The draft tube is a pipe of gradually increasing area which connects

the outlet of the runner to the tail race. It is used for discharging water

from the exit of the turbine to the tail race. The draft tubes also have the

following purposes:

• It permits a negative head to be established at the outlet of

the runner and thereby increase the net head on the turbine.

• It converts large proportion of kinetic energy rejected to the

tail race into useful pressure energy.

The draft tube used here is a horizontal conical draft tube with an

inlet diameter of 2000mm and outlet diameter of 37600mm.this helps in

creating a suction pressure which helps in the successful discharge of the

fluid.

5.2.8 Penstock

The penstock is used to bring water from the reservoir to the

turbine. It gets connected to the distributor of the turbine system. A

cylindrical hollow tube of 2000mm diameter is used here. It also consists

of bellows at the elbows. These elbows are dynamically inefficient.



5.2.9 ELECTRICAL EQUIPME�TS

Typically these includes:-

• Generator & its Auxiliaries

• Switchgear Panels

• Cables

• Generator Transformer

• Switchyard Layout & Structures

• Instrument Transformer

• Circuit Breaker

• Disconnecting Switch

• Lightning Arrester

• Control & Protection Panels of Generator & Transformer

• Automation of Turbine, Control & Protection

• Supervisory Control And Data Acquisition (SCADA)

• Illumination of Power house & Switchyard

• Ventilation system

• Fire Fighting Equipment

5.3 TECH�ICAL DETAILS

Turbine:

1. Type : Upstream elbow Semi Kaplan

Make : BEACON NEYPRIC

2. Rated Head : 14.4 m

3. Rated Discharge : 23.14 m3/s



4. Rated output : 2950 kW

5. Rated Speed : 375 rpm

6. Runaway Speed : 1050 rpm

7. Runner

a) Diameter : 1900 mm

b) Number of blades : 4 No.s

c) Hub Diameter : 810 mm

d) Material

(i) Runner : 13 /4 Chromium Nickel S S

(ii) Hub : Cast Steel

8. Turbine Bearing : Thrust bearing 620*340*170

Spherical Roller 440*260*144

9. Coupling type : Resilient

(i) H-660-Low speed

(ii) H-660-High speed

Make : WELLMAN

10. Inlet Valve

a) Type : Butterfly

b) Operation : Hydraulic

c) Diameter : 1850 mm



Make : FOURESS

11. Maximum head : 24.8 m

12. Minimum head : 8.3 m

Generator:

1. Make : JYOTHI

2. Capacity : 2.5MW

3. Gen. Voltage : 11000 V

4. Type of excitation : Static

5. Generation : 5.6M. Units/ year (Anticipated)

Dam:

1. Full reservoir level : 115.09 m

2. Min. draw down level : 99.5 m

3. Gross storage : 236.7 Mm3

4. Live storage : 226.5 Mm3



6. HYDEL PLA�T –PRESE�T SITUATIO�

The Malampuzha mini Hydel project is a non-working dead

investment. The project, since its completion, has worked only for 200

days.

The problem of the Hydel plant starts from its selection of the

turbine. The selection of the turbine must have been done on the basis of

specific head and the required power and available head.

�s = � √Pr ÷ (Hr) 5/4 6.1

Where N=speed of rotation (rpm)

Pr = Rated power

Hr = Rated head

From the technical description given we obtain the values

N =375rpm

Pr =2950kW

Hr =14.4m

Therefore Ns= 375 ×√2950 ÷ 14.4 = 726.08

�s =726.08

For this specific speed, the most suited turbine was a vertical

Kaplan turbine with Syphon intake. But unfortunately they have placed

a horizontal semi Kaplan turbine.

A horizontal semi Kaplan turbine has a flow in axial direction. It

has fixed guide vanes and movable runner vanes. These kinds of turbines

need a specific speed of 1000-1250. Although it can work on the given

specific speed the efficiency of the system will be under objection



Table 2: comparison of two types of Turbine

S �o. Parameter TUBULAR (SEMI KAPLA�)

VERTICAL WITH SIPHO� I�TAKE

1 Inlet Valve Required Not Required

2 Draft tube gate Required Not Required

3 Drainage pump Required Not Required as setting is above maximum tail race level

4 Dewatering pump Required Not Required as setting is above tail race

5 Cost of civil work High Low

6 Efficiency 1% higher

Table 2: Comparison between Tubular and Vertical Kaplan with siphon

intake

6.1 Calculation based on the log book values

Table 3: log book calculation

Head

(m)

Discharge

(cussecs)

Discharge

(m3/sec)

Power

(kw)

Efficiency

(%)

21.36 550 15.576 2300 70.47

25.3 520 14.726 2300 62.93

23.7 540 15.293 2300 64.69

22.4 500 14.16 2300 73.92

21.4 550 15.576 2300 70.34

20.4 550 15.576 2300 73.79



Sample Calculation (Set. �o: 4)

Water Level = 112m

Net Head (H) = Water level - Runner level - Tail race level

= 112 - 88 - 1.6

=22.4m

Discharge (Q) = 500 cussecs

= 500 * 0.02832

= 14.16 m3/sec

Output Power = 2300 kw

Efficiency = S. P/ρgQH

Where ρ = density of water = 1000kg/m3

g = acceleration due to gravity = 9.81 m/s2

Efficiency = 2300*1000/1000*9.81*14.16*22.4

=0.7392

= 73.92 %

According to Beacon Neyrpic, the manufactures of the turbine,

Rated Head = 14.14 m

Rated Power = 2950 kw

Rated Discharge = 23.3 m3/sec

So efficiency for this system is

Efficiency = 2950*1000/1000*9.81*14.14*23.3

=0.9127

= 91.27 %



The efficiency of the turbine in general working condition is

obtained to be less than the efficiency stated by the manufacturer. These

may be due to the problems with the following components of the system

1. Penstock

2. Draft Tube

3. Inlet Shutter

4. Flow Meter

1. Penstock

The penstock that they use there right now is a double elbowed one for

which the efficiency is too low. Also there is only one butterfly valve to

stop the flow of water towards the Turbine. This may cause problem

during maintenance work. Also if the butterfly valve fails, we cannot

control the flow of water to the Turbine The butterfly valve is

hydraulically controlled.

2. Draft tube

The draft tube mounted here is a conical draft tube. All low-head, high

discharge turbines has to be given amply dimensioned draft tubes. This

draft tube must be suitably designed. The height of the draft tube was too

great and hence the water pressure around the runner became so low. This

creates cavitation problems, and it is necessary to mount the runner below

tail-race level. The negative head created by the draft tube is too low. The

draft tube is not designed to fulfill the maximum head of the Turbine

3. Inlet shutter

As mentioned, the flow of inlet water is completely controlled by

the butterfly valve. A failure to this valve will result in complete failure

of the project. In order to nullify this, we can create an inlet gate or a



shutter which can control the flow at the beginning itself. This helps in

the maintenance work of the dam.

4. Flow meter

The flow meter is a pre- requisite for the proper functioning of the

turbine. As we know the efficient working of the turbine is mainly

controlled by the head available and the discharge. This discharge or the

flow rate is calculated using the flow meter. A flow meter calculates the

rate of flow of liquid through the penstock and this value is fed into the

PLC circuit which controls the blade angle. Depending upon the

discharge or flow rate the PLC circuit changes the blade angle so as to

obtain the required rpm.

But this flow meter was missing in the project site. That means

there was no control of the flow of liquid through the turbine.



7. TECH�ICAL FEASIBLITY OF THE

PROJECT

Since the basic structure of the plant is already built, a wide range

change of the structure is not possible, i.e. we can’t now change the

horizontal Kaplan into a vertical Kaplan with siphon intake. So the

technical feasibility study of the plant will be restricted to the present

situation existing over there.

One of the major limitations we came up during our project is:

i) Non- operational system

ii) Flow meter

iii) Net head calculation

iv) Mechanical and electrical losses

v) Fixed guide vanes

vi) Blade angle

7.1 �on- operational system

Since the complete system is non-operational we couldn’t take the

readings from the system. Some readings such as the flow rate, runner

speed, blade angle etc could only be found out during its operation. So

such values should be assumed. This can be done in two ways; either we

can rely upon the technical details provided by the manufacturer or find

out the values which we obtained during its operation (The log book

values). We opted for the log book values.



7.3 Flow meter

As discussed earlier, the flow meter was missing in the project site.

This was one of the major limitations for our project. The values we

obtained from the log book were calculated using Canal Discharge

method. As we know, the major parameters for a Kaplan turbine are

discharge, head and speed. The relation between these three are

controlled or regulated by a flow meter. Three flow meters must be

placed- near the inlet, near the distributor and near the draft tube. These

three flow meters will give us the actual flow rate and also the pressure

drop (energy drop) occurring along the system. It also helps us to find out

the velocity of flow of water through the system.

7.4 �et head calculation

The net head is calculated as the difference of dam water level

and the tail race level, which is a false reading. The net head is the

difference between gross head and frictional head loss. This frictional

head loss is not calculated in the reading. So the head reading has to be

revised.

7.5 Blade angle

The blade angle of the turbine has to be provided by the

manufacturers. These blade angles must be fed into the PLC circuit and

the circuit controls the movement of the blade according to the varying

discharge. But here, no details about the blade angles have been provided

by the manufacturer. Due to these technical limitations the operators are

changing the blade angles by trial and error method.



7.6 Fixed guide vanes

The Kaplan turbine used here is a horizontal semi Kaplan turbine.

It has fixed guide vanes .These fixed guide vanes are set at a particular

angle by the manufacturer which cannot be changed. The exit angle of the

guide vanes may not be the same as that of the inlet angle of the runner.

This obstructs the shock-free flow of the water into the runner. This

produces turbulence by which the hydraulic efficiency of the turbine is

reduced.

It has been found out that the rated power is obtained at a discharge

of 17 m3/sec (rated discharge) and 19.5m head (rated head). This was

found out during its 200 days of operation. This increase in head is

mainly due to the change in the net head range which varies from 15m-

25m head.

So all the calculation for the efficiency improvement will be based

on these values

Rated Power= 2950kW

Rated head=19.5m

Rated discharge=17 m3/sec



8. EFFICIE�CY IMPROVEME�T

η= shaft power / water power =S.P/ ρ g QH

The efficiency of the turbine can be increased by

i) Increasing discharge

ii) Increasing head

iii) Increasing shaft power

But as you can see the efficiency is inversely proportional to the

head and discharge. This may make us to feel that the above statement is

false. But what happens is that when head is increased the discharge

through the pipe will be increased. Now this head and discharge are

directly proportional to the power.

In the case of Kaplan turbine the efficiency of the turbine is

assumed to be constant and the value of shaft power is found out. Hence

the concept of increasing efficiency generally implies to the improvement

of shaft power for a given head. For this first we will find out the shaft

power developed at different heads (for a given efficiency) Let the rated

efficiency be 90%

Shaft power and discharge calculation using Qu and Pu

Qu= Q1/√H1= Q2√H2 = …….

Pu= P1/H13/2= P2/H2

3/2 = …….

Here rated power is 2950 kW = P (Since rated power will be equal to

rated output at maximum efficiency)

Rated discharge is 600cusecs = 600*.02831=16.99= 17m3/sec = Q



Rated head= 19.5m = H

Efficiency for the given parameters

η= S.P/W.P

η= 2950/9.81*17*19.5 = 90 %

Qu = Q/√H = 17/√19.5 = 3.80 Qu= 3.80

Pu = P/√H3 = 2950/√18.62 = 34.26 Pu= 34.26

Table 5: Calculation of Plant Factor

HEAD

(m)

DISCHARGE

(m3/sec)

POWER

(kW)

PLANT

FACTOR (%)

15 14.91 1990.32 67.46

16 15.40 2192.64 74.33

17 15.87 2401.30 81.40

18 16.33 2616.35 88.68

19 16.78 2837.38 96.18

20 17.22 3064.30 100.00

21 17.64 3296.97 100.00

22 18.06 3535.26 100.00

23 18.46 3779.02 100.00

24 18.86 4028.13 100.00

25 19.25 4282.50 100.00

The plant factor is assumed to be 100% for power values higher

than the rated power.



But discharge cannot be varied in this manner as it produces highly

varying torque on the shaft. Hence the discharge is kept constant for

certain specific heads and not varied for a particular range of head. Now

the discharge is reduced by closing the inlet of the penstock. This will

reduce the power as the power is proportional to discharge also.

Generally a Hydel plant is defined by its plant factor. Plant factor is

defined as the ratio of power generated to the rated power.

i.e. Plant factor = Power generated Rated power

.

i) Calculation of velocity of flow through the turbine

The velocity of the flow can be found out from the formula

Q = π/4(Do2-Dh

2) ×V1

Where Q = discharge through the runner

Do = Runner outer diameter

Dh = diameter of hub

V1 = velocity of flow at inlet.

For this calculation let’s take the rated discharge.

So Q = 17 m3/sec

Do= 1900mm = 1.9 m

Dh = 810mm = 0.81 m

Therefore V1= 7.32 m/sec



ii) Calculation of frictional head loss

The frictional head loss can be calculated by

∆ Hf = V12/2g

Where g = 9.81m/sec2

∆ Hf = 2.74m

iii) Calculation of net head

The net head is the head available to the turbine unit for power

production. This head is the static gross head, the difference between the

level of water in the Forebay/impoundment and the tail water level at the

outlet, less the hydraulic losses of the water passage.

i.e. ∆ H = ∆ Hg - ∆ Hf

Where ∆ H = net head

∆ Hg = gross head = water level – tailrace level

∆ Hf = frictional head

Therefore ∆ H = (water level- 89.6- 2.74)

= (water level – 92.34)



9. IMPROVISATIO� �EEDED

The efficiency of a low head Kaplan turbine (as in our case)

generally depends upon the draft tube loss and the runner loss. The runner

loss is mainly due to the improper blade angles. The draft tube losses are

generally based on the cavitation problems.

9.1 I�STALL A FLOW METER

Controlling the flow rate of liquid is a key control mechanism for

any Kaplan plant. There are many different types of devices available to

measure flow.

Flow meters are classified on the basis of the parameter which is

used for flow measurement. They are mainly classified into three. They

are:

1. Head Type:

I. Orifice Plates

II. Rotameters

III. Venturi Tubes

2. Velocity Type

I. Magnetic

II. Vortex

III. Differential Pressure Meter

3. Displacement

I. Turbine Meter

Out of these we suggest the installation of turbine flow meter or

differential pressure meter



Differential-Pressure Meters

Design overview:

While many different types of differential-pressure flow meters are

available, this discussion will focus on one type. The technology

discussed here involves the measurement of a pressure differential across

a stack of laminar flow plates. During operation, a pressure drop is

created as fluid enters through the meter's inlet. The fluid is forced to

form thin laminar streams, which flow in parallel paths between the

internal plates separated by spacers.

The pressure differential created by the fluid drag is measured by a

differential-pressure sensor connected to the top of the cavity plate. The

differential pressure from one end of the laminar flow plates to the other

end is linear and proportional to the flow rate of the liquid.

What makes this technology unique is the linear relationship

between differential pressure, viscosity and flow, which is given by the

following equation

Q = K [P1-P2)/µµµµ]

where (units vary per approach):

Q = Volumetric flowrate

P1 = Static pressure at the inlet

P2 = Static pressure at the outlet

µµµµ = Viscosity of the fluid

K = Constant factor determined by the geometry of the restriction



Variances in temperature and pressure, which often cause errors in

variable-area flow meters, can be easily handled by adding a pressure

sensor (separate from the differential-pressure sensor in the basic design)

and a temperature sensor to the design, and correct the flow readings to

standard pressure and temperature (77°F and 1 atm). Typical accuracy for

the design is ±2-3% fullscale.

Advantages:

As with mass flow meters, the differential-pressure meter has no

moving parts to wear out.

For control applications, these meters are available with a built-in

proportioning valve for onboard or remote control of the flow rate. With a

wide variety of flow ranges and models for both gases and liquids, the

differential-pressure meter is one of the most versatile designs currently

on the market.

Turbine Meters

Design Overview:

Many designs exist for turbine flow meters, but most are a

variation on the same theme. As fluid flows through the meter, a turbine

rotates at a speed that is proportional to the flow rate. Signal generators,

usually located within the rotor itself, provide magnetic pulses that are

electronically sensed through a pickup coil and calibrated to read flow

units. In some designs, an integral display may show both the flow rate

and the total flow since power-up.

Because of the rotating blades in a turbine meter, the output signal

will be a sine wave voltage (V) of the form:



V= K ωωωω sin (� ωωωω t)

where:

K = The amplitude of one sine wave

ωωωω = The rotational velocity of the blades

� = The number of blades that pass the pickup in one full rotation

t = Time

Because the output signal is proportional to the rotational velocity

of the turbines—which, in turn, is proportional to the liquid flow—the

signal is easily scaled and calibrated to read flow rate and flow

totalization. Turbine flow sensors generally have accuracies in the range

of ±0.25-1% full-scale.

Advantages:

The main advantages of the turbine meter are its high accuracy

(±0.25% accuracy or better is not unusual) and repeatability, fast response

rate (down to a few milliseconds), high pressure and temperature

capabilities (i.e., up to 5,000 psi and 800°F with high-temperature pick

coils), and compact rugged construction. Some manufacturer's have taken

turbine meter design to the next level by incorporating advanced

electronics that perform temperature compensation, signal conditioning

and linearization, all within a few milliseconds.

Disadvantage:

The disadvantage of the turbine meter is that is relatively expensive

and has rotating parts in the liquid stream. And, most turbine meters need

a straight section of pipe upstream from the flow meter in order to reduce



turbulent flow. This may make installation a challenge in small areas.

However, some newer turbine meters reduce or eliminate the amount of

straight pipe required upstream, by incorporating flow straighteners into

the body of the unit.

Another disadvantage in some designs is a loss of linearity at the

low-flow end. Low-velocity performance and calibration can be affected

by the natural change in bearing friction over time. However, today's self-

lubricated retainers, low-drag fluid bearings, and jeweled-pivot bearings

all help to reduce the friction points, thereby allowing for greater

accuracy and repeatability in lower-flow applications.

9.2 EXCAVATE THE SITE DEPTH TO 85 M

By excavating the total depth of the project site into 85 m, the

minimum head from which the power can be generated will be

lowered to 8.3 m; i.e. we can generate power even at a water level of

97m. This helps the plant to generate power even at the worst

condition of draught.

9.3 I�TRODUCE MOVABLE GUIDE VA�ES RATHER THA�

FIXED O�ES

As mentioned earlier, the fixed guide vanes will not give a

shock free entrance of water stream into the runner at every angle.

This results in poor efficiency or decreased runner power. This is a

great loss. So the fixed guide vane has to be changed into a movable

guide vane.



To control these movable vanes, we have to include a PLC

circuit which controls the blade angle of the guide vanes. This PLC

circuit must be developed designed and should be installed by the

manufacturers itself.

The PLC circuit of the runner vane and the guide vane can be

incorporated. Since, for the shock-free entrance of the water stream,

the outlet angle of the guide vane and the inlet angle of the runner

vane must be equal. So by using a suitable PLC circuit we can control

both the runner and the guide vane angles together and there by

produce higher efficiency rates.

9.4 USE OF A� S-SHAPED DRAFT TUBE

The conical draft tube placed over there is a horizontal conical

draft tube whose efficiency is under suspicion. The efficiency of this type

of draft tube is dependent on the angle of the diverging walls. Small

divergence angles require long diffusers. Here a small diffuser has been

used. This can be made into fully functional by shanging the divergence

angle to about 15 degrees rather than the typical optimum value of about

7 degrees.

The horizontal conical tube is neither having the required divergent

angle nor the required length. So this conical draft tube can be changed

into a S-shaped draft tube. The feature in favour for the S-shaped draft

tube is the flexibility of placing the runner above the tail race level. This

helps in the maintenance work and also in increasing the net head without

causing cavitational problems.



10. CO�CLUSIO�

The Malampuzha dam at present is a dead investment. Among the

many flaws that make it, we decided to focus on the major three:

1. The turbine efficiency at the time of working was only around 70%

as opposed to the rated efficiency of 90%

2. The basic construction caused cavitation problems in the draft tube

3. Since there was no flow meter to measure the flow rate, the blade

angles were adjusted on the basis a trial and error method.

Providing answers to these problems would be a start towards

renovation of the Hydel project.

With a view towards increasing efficiency, we redesigned the

construction so that the output efficiency becomes 90%

Suggestions put forth include:

1. Increasing head by lowering draft tube

2. Replacing semi-Kaplan with a full Kaplan turbine

3. Installation of flow meter at the start of penstock, inlet of runner

and inlet of draft tube

4. A PLC circuit is set-up to take the readings from the flow meter

and make corresponding changes to the blade angles.



BIBILIOGRAPHY

1. Beacon Neyrpic turbine operation and maintenance manual

2. Dr.R. K. Bansal, Fluid Mechanics and Hydraulic Machines

3. Dr. P. N. Modi & Dr. S. M. Seth, Hydraulics and Fluid Machines

including Hydraulic Machines

4. S. Ramamrutham & R. Narayan, Hydraulics Fluid Mechanics &

Fluid Machines

5. Roger E. A. Arndt, Ceaser Farell & Joseph M. Wetzel, Small And

Mini Hydropower Systems by

6. Indian Institute of Technology, Roorkee , Guide For Selection of

Turbine and Governing System For Small Hydro Power

7. www.wikipedia.com

Project Final

Documents

malampuzha

laminar flow

metric horse

conical draft

fixed guide

suction specific

variable pitch

frictional