Experiment Name: Study Performance characteristics test of a Pelton Turbine.
∆h= Difference in pressure gauge reading of venturimeter in terms of head.
Objective:
(i) To study different components of a Pelton Turbine.
(ii) To obtain the operating characteristics of the Pelton Turbine.
(iii) To find the efficiency of the Pelton Turbine.
Apparatus Used:
1. Pelton Turbine,
2. Pressure Gauges,
3. Venturimeter,
4. Brake drum.
Specification:
Rated Supply head (H)=30 metre
Rated Discharge (Q)= 500 lpm
Normal Speed (N)= 1000 rpm
Maximum Jet diameter = 22mm
Theory:
It is a type of tangential flow impulse turbine used to generate electricity in the hydroelectric power plant. This turbine was discovered by the American engineer L.A. Pelton.
Pelton turbine working principle is that, here high speed jets of water emerge from the nozzles that surround the turbine. These nozzles are arranged such a way that the water jet will hit the buckets at splitters, the center of the bucket where the water jet is divided into two streams. The two separate streams then flow along the inner curve of the bucket and leave in the opposite direction that it came in. This change in momentum of the water creates an impulse on the blades of the turbine, generating torque and rotation in the turbine.
The energy available at the inlet of the Pelton turbine is only kinetic energy. The pressure at the inlet and outlet of the turbine is atmospheric pressure. This type of turbine is used for the high head.
Experimental procedure:
1. The Pelton turbine is placed on the sump tank level and a pump used for supply water to the turbine.
2. Set venturimeter to measure the flow rate to the turbine. The gate valve is placed at the inlet side of the turbine to regulate supply head.
3. A spear and nozzle arrangement is used to control amount water supply to the turbine bucket.
4. Check lubrication of the ball bearings, and make sure the pipelines are free from foreign particles.
5. Close the gate valve and the spear at the turbine inlet and make the hanger load free.
6. Start the pumpand then gradually open the gate valve and check the supply head by the reading of the pressure gauge.
7. Slowly open the spear by hand wheel for steady rotation of turbine.
8. Note down Pressure gauge reading.
9. Hang the load on the hanger. And due to the applied load the speed of the turbine will be decreased,
11. Now adjust the speed by changing the spear opening.
Observations:
input power:-
The input power
Pinput = γQH/1000 KW
Where,
γ= ρg= specific weight of water,
Q= Discharge in m³/sec,
H= Supply head in meter.
A1= Inlet area of the venturimeter.
A2= Throat area of the venturimeter.
Cd= Discharge coefficient of the venturimeter = 0.962
Output power:-
The output power Poutput =2πNReTg/(60×1000) KW
Where,
N= Turbine shaft rotational speed r.p.m.
Re= Effective radius of the brake drum.
T= Net brake load.
Data to be collected before starting the experiment:-
Temperature of the water= 20°C,
Density of the water (ρg)= 1000 kg/m³
Venturimeter inlet diameter (D1) = 0.05 m
Venturimeter throat diameter (D2) =30 m
Brake Drum diameter (D)= 0.2 m
Rope diameter (t)= 0.016 m
Effective radius Re= (D/2+t)= (0.2/2) + 0.016= 0.116 m
Weight of the rope and hanger (Wi)= 1 kg.
Note:- Sample pelton turbine calculation are shown below for input power and efficiency calculation.
Required Graph to be plotted:
A. Input Power vs Discharge.
B. Efficiency vs Discharge.
Note:- Both graphs are drawn on the same graph paper for better understanding.To draw a continuous proper graph some point of reading is to be ignored.
FAQ:
1. Draw the schematic diagram of the setup.
Figure- Pelton turbine setup.
2. Identify each components of Pelton turbine and briefly state the function of each component.
Parts of Pelton Wheel Turbine:-
1. NOZZLE WITH SPEAR ARRANGEMENTS- The water comes out from the circular guide mechanism through nozzle. Then the water Jet strikes the bucket.A conical needle called spear operates manually or automatically inside the nozzle in axial direction to regulate the flow.
2. RUNNER WITH BUCKET- Runner consists of a circular disc, on the Periphery of which the vanes or bucket is fixed. The water jet strikes the bucket and power is generated.
3. CASING- The casing generally made of cast or fabricated parts but does not perform any hydraulic function. it is used to safeguard the runner against accident and to prevent splashing of water.
4. BREAKING JET- In order to bring the runner to rest in a short time, an opposite jet is used for reducing the speed of the runner called Breaking jet.
3. Provide sample calculation.
4. Write Advantages and Disadvantages of Pelton wheels Impulse Turbine and pelton turbine application.
Pros:-
1. Simple in construction and easy to maintain.
2. They work at atmospheric pressure so no problem of leakage.
3. High efficiency.
4. It is easy to assemble.
Cons:-
1. This is not suitable for low-pressure streams by a high flow rate.
2. Impulse turbines are large in size compare to others.
3. Efficiency decreases with time.
4. Initial cost is high.
Applications:-
It's used for hydro-power when the available water source has a relatively high hydraulic head at low flow rates.
5. Why Pelton turbine is high head turbine?
The Pelton turbine is design to face the enormous kinetic energy of water jet. So the energy present at the inlet of the Pelton turbine is mostly and heavily kinetic energy that is why it is known as high head turbine.
Written by- SOUMIK.