Full Report Pelton Turbine

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INTRODUCTION These are two types of turbines, reaction and the impulse, the difference being the

manner of head conversation. In the reaction turbine, the fluid fills the blade passages and the head change or pressure drop occurs within the runner. An impulse turbine first converts the water head through a nozzle into a high- velocity jet, which then strikes the buckets is essentially at constant pressure. Impulse turbines are ideally suited for high power and relatively low power. The Pelton turbine used in this experiment is an impulse turbine. This turbine consists of three basic components as shown in Figure 1, a stationary inlet nozzle, a runner and a casing. The runner consists of multiple buckets mounted on a rotating wheel. The jet strikes the buckets and imparts momentum. The buckets are shaped in a manner to divide the flow in half and turn its relative velocity vector nearly 180º .

Figure 1.0 : Pelton wheel The primary future of the impulse turbine is the power production as the jet is deflected by the moving buckets. Assuming that the speed of the exiting jet is zero (all of the kinetic energy of the jet is expended in driving the buckets), negligible head loss at the nozzle and at the impact with the buckets ( assuming that the entire available head is converted into the jet velocity ), the energy equation applied to the control volume shown in Figure 1 provides the power extracted from the available head by the turbine.

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2.0 1. 2. 3. 4. 5. 6. 7. 8. 9.

OBJECTIVE To learn the design and function of a Hydraulic turbine To determine the impulse turbine characteristic To determine the power curves characteristic To produce the data of output power and torque against speed To test the output performance at different nozzle setting To determine the optimum efficiency point To compare the mechanical and electrical power To determine the generator efficiency

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3.0

THEORY Pelton wheels are the preferred turbine for hydro-power, when the available water

source has relatively high hydraulic head at low flow rates, where the Pelton wheel geometry is most suitable. Pelton wheels are made in all sizes. There exist multi-ton Pelton wheels mounted on vertical oil pad bearings in hydroelectric plants. The largest units can be over 400 megawatts. The smallest Pelton wheels are only a few inches across, and can be used to tap power from mountain streams having flows of a few gallons per minute. Some of these systems use household plumbing fixtures for water delivery. These small units are recommended for use with 30 metres (100 ft) or more of head, in order to generate significant power levels. Depending on water flow and design, Pelton wheels operate best with heads from 15–1,800 metres (50–5,910 ft), although there is no theoretical limit.

The specific speed is the main criterion for matching a specific hydroelectric site with the optimal turbine type. It also allows a new turbine design to be scaled from an existing design of known performance. (dimensioned parameter), where: 

= rpm



= Power (W)



= Water head (m) 3



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= Density (kg/m3) APPARATUS 1. Pelton Turbine instrument

2. Optic tachometer

3. Stopwatch

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PROCEDURE 1. Switch on belt brake on the value of W1. 2. Make sure to lift the ball before switch on the pump 3. Then, switch on the pump 4. Open the value controller from the minimum level to the maximum level. 5. Based on the highest pitched sound produced, record the pressure reading. 6. Then get the reading of rpm 7. Get the reading of W2 8. Pull down the ball in the turbine drum 9. The time was taken until the volume reach 5L 10. After time was recorded, lift the ball again 11. Fully closed the value controller 12. Switch off the pump 13. Repeat all the step by using range of 1.5N to 6.0N

RPM

1067.

9021.

8211.4

7678.3 7351.8 6658.1 6402.8 6318.6 4848

ω

0 111.7

9 944.7

859.90

804.07 769.88 697.23 670.50 661.68 507.7

(rad/s)

4

7 5

W1

0

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

(N) W2

0

2.3

2.9

3.6

4.2

4.8

5.2

5.6

7.1

(N) W 1−W 2

0

1.3

1.4

1.6

1.7

1.8

1.7

1.6

2.6

30

30

30

30

30

30

30

m Pm

0

36.85

36.12

38.60

39.26

37.65

34.20

31.76

55.78

(W) Rotation

0

0.039

0.042

0.048

0.051

0.054

0.051

0.048

0.078

τ( N m ¿ Volume

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

5.0

(litre) Time

27

28

27

30

27

26

25

27

27

(s) Flowrate

0.000

0.000

0.0001

0.0001 0.0001 0.0001 0.0002 0.0001 0.000

( m3 /s ¿ Pressure

19 21

18 21

9 21

7 21

9 21

9 21

0 21

9 21

7 21

39.14

37.08

38.11

35.02

39.14

39.14

41.20

39.14

35.02

0

101.9

94.78

110.22 100.31 96.19

83.01

81.14

159.2

(N) Drum radius x

30

30

10−3

(m 3

H O¿ Pw (W) Efficienc y

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η (%) 6.0 RESULT AND DATA ANALYSIS

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ω (rad/s) Example: RPM = 8211.4 ω = RPM x

2π 60

= 8211.4 x

2π 60

= 859.90 rad/s w 1−w 2 (N) Example: w 2 = 2.9 w 1 = 1.5 w 1−w 2

= 1.5 - 2.9 = 1.4 N

Rotation, τ (Nm) Drum Radius = 30 x 10−3 Example: w 1−w 2 = 1.4 N τ (Nm) = w 1−w 2 (N) x Drum Radius = 1.4 x (30 x 10−3 ) = 0.042 Nm Pm (W) Example: ω = 859.90 rad/s Rotation,τ = 0.04 Nm Pm

=ωxτ

= 859.90 x 0.042 = 36.12 W

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Flowrate ( m3 /s ¿ Volume

= 5.0 liter = 5.0 / 1000 = 0.005 m3

Example: Times = 30 s Q

= volume ( m3 ) / time (s) = 0.005 m3 / 27 s = 1.85 x 10−4

Pw

m3 /s

(W)

Pressure

= 21 m H 3 O

Example: Q

= 1.85 x 10−4

m3 /s

Pw (W) = ρgHQ = 1000 x 9.81 x 21 x (1.85 x 10−4 ) = 38.11 W Efficiency, η (%) Example: Pm (W) = 36.12 W Pw (W) = 38.11 W η=(

Pm ) x 100 Pw

= (36.12 / 38.11) x 100 = 94.78 %

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DISCUSSION The working principle of Pelton wheel turbine is water flows along the tangent to the

path of the runner. Nozzles direct forceful streams of water against a series of spoon-shaped buckets mounted around the edge of a wheel. As water flows into the bucket, the direction of the water velocity changes to follow the contour of the bucket. When the water-jet contacts the bucket, the water exerts pressure on the bucket and the water is decelerated as it does a "u-turn" and flows out the other side of the bucket at low velocity. In the process, the water's momentum is transferred to the turbine. This "impulse" does work on the turbine. For maximum power and efficiency, the turbine system is designed such that the water-jet velocity is twice the velocity of the bucket. A very small percentage of the water's original kinetic energy will still remain in the water however, this allows the bucket to be emptied at the same rate it is filled, thus allowing the water flow to continue uninterrupted. From the results obtained, we can see how Pelton Wheel reacts to different kind of input. Different flow rates give different value of work input. The slower the flow rates, the larger the work being put into the wheel. The efficiency of the slower flow rates is also better than faster one. The speed of the wheel also dropped when much weight being dropped until it stopped suddenly when the weight is too much for it to go against.

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CONCLUSION As a conclusion from the experiment that had been performed, we can conclude that

different range of flow rates and rotational speeds influences the performance of Pelton wheel turbine. The combination of flow rate and jet velocity manipulates the power or work input. The bigger the diameter nozzle the faster the flow rates but lower in velocity jet. Therefore we need the perfect combination of both. In general, impulse turbine is high-head, low flow rate device. So we can assume that our experiment is successful due to the result we obtained. The best performance of the turbine can be known from the average speed of the turbine, for the turbine with the load need higher average speed compared to turbine without load to get the best performance of the turbine. For the maximum power of the turbine produced showed that with load in turbine can get higher power compared to the turbine without load.

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REFERENCE 1. http://www.eternoohydro.com/turbines/impulse-turbines.html? gclid=Cj0KEQjwmpW6BRCf5sXp59_U_ssBEiQAGCV9GtmL1k8wnprX_F_OO AGCN3PI4-B3JnDuAgDpY2dk650aAi5g8P8HAQ 2. https://en.wikipedia.org/wiki/Pelton_wheel

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