EXPERIMENT NO.

To perform experiment on Pelton Wheel and hence to plot its characteristic curves

Apparatus

1. Pelton Wheel

2. Weights

3. Discharge Measuring Tank

4. Tachometer

5. Stop Watch

Related Theory

Introduction
In this type of turbine total energy of the fluid is converted into the kinetic energy in the form of jet of water
through nozzle and then the jet of water impinges on splitters of the series of buckets, which are mounted on
the wheel. A torque will be produced equal to the product of force and radius, which rotates the runner. As the
runner is keyed with the shaft, so mechanical energy is transmitted to the shaft and from there to the Braking
Drum. Impulse turbine is a tangential flow turbine.

Braking Torque
Product of lever arm length and weight or load is called Braking Torque. It is applied to the rotating drum to
apply brake on it.
T= W x L

Where, T is the braking torque, W is the weight in the pan and L is the lever arm.
Brake Horse Power (B.H.P.)
It is the output power available at the shaft of Pelton Wheel and is measured by applying brakes to the rotating
braking drum.

2𝜋𝑁𝑇
P0 = B.H.P = 60
Where, P0 is the output power or brake power, N is the r. p.m. of the shaft at braked position and T is the
braking torque.

1 H.P. is the rate of performing 550 ft-lbs of work per second. (1 H.P. = 746 watts).

Table: (4.1) Observation & calculation 100% Gate open

Parameter Value Unit
Hs 155 Ft of water
Z 20.2 Inch
H = Hs + Z 47.76 m of water
L 18 Inches
Temp 24 ℃
𝜸 9779.4 N/𝑚3
Tank Dimension 47.7 X 47.7 X 30.9 Inches
Tank Vol. 1.15 𝑚3
Time to fill the tank, t 66.74 Sec
Q= 𝒕
𝑽𝒐𝒍. 0.017 𝑚3 /𝑠
Pin = 𝜸𝑸𝑯 7840.1 watts

Table: (4.2) Observation & calculation 100% Gate open

Sr.no w T=wx N P0 =
𝟐𝝅𝑵𝑻 𝑷𝟎
Ƞ = 𝑷𝒊𝒏100
L (r.p.m) 𝟔𝟎
(watts) (%)
(n-m)
Lbs N
1 0 0 0 1360 0 0

2 5 22.25 10.17 1340 1427.7 18.0

3 10 44.5 20.35 1260 2684.9 33.8

4 15 66.75 30.52 1220 3899.4 49.1

5 20 89.0 40.69 1160 4943.6 62.3

6 25 111.25 50.86 1100 5859.8 73.8

 T(N-m) vs N (r.p.m)
60

50

40
T (N-m)

30

20

10

0
0 200 400 600 800 1000 1200 1400 1600
N (R.P.M)

Fig 4.1

Ƞ (%) VS N (R.P.M)
80
70
60
50
Ƞ (%)

40
30
20
10
0
0 200 400 600 800 1000 1200 1400 1600
N (R.P.M)

Fig 4.2

P0 vs N
7000

6000

5000
P0 (Watts)

4000

3000

2000

1000

0
0 200 400 600 800 1000 1200 1400 1600
N (R.P.M)

Fig 4.3
 Table: (4.3) Observation & calculation 50% Gate open

Parameter Value Unit

Hs 20.5 Ft of water
Z 20.2 Inch
H = Hs + Z 63 m of water
L 18 Inches
Temp 24 ℃
𝜸 9779.4 N/𝑚3
Tank Dimension 47.7 X 47.7 X 30.9 Inches
Tank Vol. 1.15 𝑚3
Time to fill the tank, t 123.2 Sec
Q= 𝒕
𝑽𝒐𝒍. 0.009 𝑚3 /𝑠
Pin = 𝜸𝑸𝑯 5544.9 watts

Table: (4.4) Observation & calculation 50% Gate open

Sr.no W T=wx N P0 =
𝟐𝝅𝑵𝑻 𝑷𝟎
Ƞ = 𝑷𝒊𝒏100
L (r.p.m) 𝟔𝟎
(watts) (%)
(n-m)
Lbs N
1 0 0 0 1450 0 0

2 5 22.25 10.18 1340 1428.5 25.8

3 10 44.5 20.34 1170 2492.1 44.9

4 15 66.75 30.52 1020 3260.0 58.8

5 20 89.0 40.69 800 3408.8 61.5

6 25 111.25 50.36 600 3195.6 57.6

 T(N-m) vs N (r.p.m)
60

50

40
T (N-m)

30

20

10

0
0 200 400 600 800 1000 1200 1400 1600
N (R.P.M)

Fig 4.4

P0 vs N
4000

3500

3000

2500
P0 (Watts)

2000

1500

1000

500

0
0 200 400 600 800 1000 1200 1400 1600
N (R.P.M)

Fig 4.5

Ƞ(%) VS N (r.p.m)
70

60

50

40
Ƞ (%)

30

20

10

0
0 200 400 600 800 1000 1200 1400 1600

N (R.P.M)

Fig 4.6
Indicated Horse Power (I.H.P.)
It is the input power supplied to the Pelton Wheel in hydraulic form.
Pin = 1 fl.P

Where, 7 is the specific weight of water, Q is the discharge through the nozzle and H is the head available at
the base of the nozzle (H = Hg + Z). I-Ig is the pressure head given by the Bourdon Gauge and Z is the
elevation correction.

Efficiency

It is the %age ratio between the output power available at the shaft of Pelton Wheel (B.H.P.) and input
power supplied to it (I.H.P.).
𝑷𝟎 (𝐁.𝐇,𝐏)
Ƞ = 𝑷𝒊𝒏 x 100 = 𝐗 𝟏𝟎𝟎
(𝐈.𝐇.𝐏)

Gate Opening
It is the opening of the nozzle mouth in %age. Suppose if 6 turns are required in anticlockwise direction for
100% gate opening then 3 turns in clockwise direction are required for 50 % gate opening.
This experiment is being performed on two gate openings i.e. 100% of 50%.

Characteristic Curves
It is the graphical representation of the response of Pelton Wheel at varying speed (O-Nmax) for efficiency,
output power and braking torque.
Characteristics curves are required to study the behavior of the machine under varying speed and to determine
the important parameters of the machine, like maximum efficiency of the machine, normal speed, maximum
braking torque, maximum power and maximum speed of the turbine etc.
A turbine is always designed and manufactured to work under a given set of conditions such as discharge,
head of water, speed, power generated, efficiency etc. but a turbine may have to be used under conditions
different than those for which it has been designed. It is essential that exact behavior of turbine under varied
conditions should be predetermined. This can be predicted graphically by means of the characteristic’s curves.
These curves are drawn for constant head and discharge or constant input power.
The characteristics curves are provided by the Manufacturer of the turbine and are essentially required at the
time of its purchase.

Normal Speed

It is the speed of the shaft of the turbine (r.p.m.) corresponding to its maximum efficiency.
 Procedure

1. Switch on the motor of the pump.

2. Adjust the spear headed needle to have the 100% gate opening. This can be achieved by completely
closing the valve and then opening it by 6 turns.
3. Note down the head available at the bourdon gauge.
4. Note down the atmospheric temperature and determine the specific weight of water corresponding
to that temperature.
5. Note down the r.p.m. of the revolving shaft with the help of Tachometer.
6. Observe time required to fill the tank of known volume.
7. Put some load on the pan and apply brakes to the drum by tightening the clamp, which will reduce
the r.p.m. of the shaft. Note down the weight applied and the corresponding speed into the table.
8. Repeat step no. 7 by taking load increments of 5 or 10 N till the r.p.m. are reduced to 600.
9. Repeat steps 2 to 8 for 50% gate opening, which can be achieved by turning the handle of spear
headed needle 3 turns in the forward direction.
10. Switch off the motor of the pump.

Precautions
 While applying brakes on the braking drum, do not forget to open the valve of the drum-cooling pipe
to avoid burning of the leather brake shoes.

Results
Results of the experiment (characteristics curves) are shown in Figures 4. And 4. in graphical form and in
Table 4.5 in tabular form.

Table: (4.5) Comparison of Results for two-gate openings

Description For 100% Gate opening For 50% Gate opening

Head (m of water) 47.76 63
Maximum Power (watts) 7010.5 3408.8
Maximum Efficiency (%) 88.3 61.5
Maximum Speed (R.P.M) 1360 1450
Normal Speed (R.P.M) 940 800
Maximum Torque (R.P.M) 101.73 50.86
Normal Torque (T0) (N-m) 71.21 40.69

COMMENTS: