pelton wheel prac1.docx

8/19/2019 Pelton Wheel Prac1.docx

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Hydraulics

Machines III

a m e : L I S B O A

S t u d e n t o : 2 1 4 1 0 1 8 1 9

P r a c t i c a l 1

W h e e l


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1. Aim

• To investigate the operating characteristics (shaft-power, input power, torque,

overall efficiency and flow rate) against the bucet speed.

!. Apparatus

• "ydraulic bench• #elton wheel apparatus

• $top watch

• Tachometer

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FRANCIS TURBINE

INTRODUCTION: The Francis turbine is an inward fow reaction turbine whichwas designed and developed by the American engineer James B Francis Francisturbine has a purely radial fow runner! the fow passing through the runner hadvelocity component only in a plane o" the normal to the a#is o" the runner

$eaction hydraulic turbines o" relatively medium speed with radial fow o" waterin the component o" turbine are runner

DIAGRAM:

CONSTRUCTION DETAILS OF FRANCIS TURBINE:

%omponents o" the Francis turbine&'

( Pen sto)e& * It is a large si+ed shaped! where the water is provided to theturbine runner "rom the dam

( ,croll casing& * Penstoc)s connected to and "eeds water directly into an annularchannel surrounding the turbine runner The channel is spiral in its layout

( -uide vanes& * A series o" air"oil shaped vanes called the guide vanes arearranged inside the casing to "orm a number o" fow passages between thecasing and the runner blades -uide vanes are .#ed in position /they do notrotate with rotating runner0

( -uide wheel and governing mechanism& * It changes the position o" guideblades to a1ect variation in the water fow rate in the wa)e o" changing load

conditions on the turbine 2hen the load changes3 the governing mechanismrotates all the guide blades about their a#is through the same angle so that thewater fow rate to the runner

( $unner and runner blades& * $unner o" the Francis turbine is a rotor which haspassages "ormed between the drat tube and scroll casing

( 4ra"t tube& * A"ter passing through the runner3 the water is discharged to thetail race through a gradually e#panding tube

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WORKING OF FRANCIS TURBINE: The amount o" water "alls on the vanes/buc)ets0 o" the runner The turbine rotor is called runner $unner revolves atconstant with the help o" governing mechanism The runner sha"t is connectedwith the generator! thus the electricity is produce with the help o" generatorAnd the water is discharge "rom the tail race

THEORY OF OPERATION: The Francis turbine is a reaction turbine3 whichmeans that the wor)ing fuid changes pressure as it moves through the turbine3giving up its energy A casement is needed to contain the water fow Theturbine is located between the high pressure water source and the low pressurewater e#it3 usually at the base o" a dam

The inlet is spiral shaped -uide vanes direct the water tangentially to therunner This radial fow acts on the runner vanes3 causing the runner to spin Theguide vanes /or wic)et gate0 may be ad5ustable to allow e6cient turbineoperation "or a range o" water fow conditions

As the water moves through the runner its spinning radius decreases3 "urther

acting on the runner Imagine swinging a ball on a string around in a circle I" thestring is pulled short3 the ball spins "aster This property3 in addition to thewater7s pressure3 helps inward fow turbines harness water energy

At the e#it3 water acts on cup shaped runner "eatures3 leaving with no swirl andvery little )inetic or potential energy The turbine7s e#it tube is specially shapedto help decelerate the water fow and recover )inetic energy

APPLICATION: Francis Inlet ,croll3 -rand %oulee 4am 8arge Francis turbinesare individually designed "or each site to operate at the highest possiblee6ciency3 typically over 9:; They are best suited "or sites with high fows andlow to medium head Francis Turbines are very e#pensive to design3

manu"acture and install3 but operate "or decadesIn addition to electrical production3 they may also be used "or pumped storage!where a reservoir is .lled by the turbine /acting as a pump0 during low powerdemand3 and then reversed and used to generate power during pea) demand

Francis turbines may be designed "or a wide range o" heads and fows This3along with their high e6ciency3 has made them the most widely used turbine inthe world

%. &ethod

'nitialie the apparatus and place it on top of the channel of the hydraulic bench. ouple the pipe of the apparatus to the hydraulic bench. *nsure that the pony brae is freed from the drum. +ero each spring balance. Then after, $witch on the pump and slowly open the flow control valve on the

hydraulic bench.

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Adust the nole control on the apparatus until the turbine runs at maimumspeed.

se the tachometer to measure the speed of wheel. &easure the inlet pressure and determine the water flow rate. Adust the pony brae so that the spring-balance reading 1 / 1 0

Tae the measurements for the speed, flow rate, the inlet pressure head and thereadings on the spring-balance.

epeat the procedure as 1 is increased in intervals. epeat the above procedure for second case where flow rate is changed.

2. #resentation of results

ase1

,et 1 ! % 2 3

RPM 1%4! 1%11 1!!3 115% 167!

ωrad / s ?>@

@@

@>

@>

>@

?

:= := :C :?

W 1−W 2( N ) ? ? =C C=

r¿

Drumradius¿¿

: : : : :

T ( N .m) ::C= ::@ :


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alculations of, , 1: !, torque, , ;low rate, , and efficiency. The calculationsof the first set will be taen as an eample on how the characteristics were calculated in

each set <

Angular velocity

w=2π

60×1362

¿142.628 rad/s

;or effective force on drum

w1−w2=2−0.2

/ 1.=0

Torque

T =(W 1−W 2 ) r

¿ (2−0.2)30×10−3

¿0.054 Nm

;low rate (>)

Q=v

t 1m3=1000l

¿

0.03

5.45 3 l=0.03m3

¿550.459×10−6

m3/ s

'nput power

Pw= ρgQH

¿(1000)(9.81)(550.459×10−3)(6)

¿32.4W

?utput #ower

Pm=T ×w

¿0.054×142.628

¿7.702W

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?verall efficiency

ɳ 9 / Pm

Pw×100

/7.7

32.4×100

¿ !%.2 9

3. @raphs


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9/15

C/'$ 2

An0/% &$"(!

ω=2

π × N 60

E2 π ×1717

60

1.6784 %/*9'

Toue

2< * 2> E > * :< E 16

T E /2< * 2>0 G r

E


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• 6ciency

ƞovr

= P

!T

P¿

¿ 10.24942.909

×100

236

,et < > = C RPM

(Vl) =>9:9 =>CC? ===9@ == :C:= :C :C>?

Input Power

P

(¿¿w= ρgQH )¿

2

9 9 9 9 9

Power output Pm(W ) out 8 =9 9 = = =@? C>@

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G%/p;'

,ha"t P

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Input Po

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Torue /

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Dverall

onclusion

;rom the practical report that has been done, it was clear that the shaft power is inversely

proportional to rotational speed of the bucet speed of the pelton wheel. ?n the otherhand the bucet speed is directly proportional to the input speed to the pelton wheel. As

the speed increase the overall efficiency decreases and lastly torque and bucet speed areinversely proportional

'n conclusion ' can say the practical eperiment was successful. "owever not for all

characteristics needed to be calculated .the graphs including overall efficiency, input shaft

power and flow rate shows irregular shapes. The caption of time played a vital role in this practical, the irregular shapes of these graphs were due to incorrect and inadequate

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caption of time which results unreliable results. 'n order to prevent such errors during

practical conduction, there must be number of students taing readings, and the

eperiment must be repeated as well.

eferences

• ;luid mechanics #art ! ; &eyer • www.wiipedia.com

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pelton wheel prac1.docx

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