Experiment 4: Determination of Efficiency of Pelton Turbine
Objective
The objective of this experiment is to determine the efficiency of a Pelton turbine by measuring
the torque, rotational speed, discharge, and pressure, and using these values to calculate the
efficiency.
Apparatus Used
1. H19 Pelton turbine with associated parts
2. Digital tachometer
3. Stopwatch
Theory
There are two types of turbine, reaction and the impulse, the difference being the manner of hcad
conversion. 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 in to a high velocity jet, which then strikes the buckets at one position as they pass by.
The runner passages are not fully filled, and the jet flow past the buckets is essentially at constant
pressure. Impulse turbine are ideally suited for high head and relatively low power. The Pelton
turbine used this experiment is an impulse turbine .The Pelton turbine is a type of impulse
turbine used for high head and low flow applications.
Efficiency is calculated using the formula:
W
Efficiency (η) =
PQ
Where:
W=T⋅ω is the power output
T is the torque (Nm)
ω is the angular speed (rad/s)
P is the pressure (Pa)
Q is the discharge (m³/s)
Torque is calculated as:
T = (Right balance−Left balance) × Drum radius
Discharge is determined by:
Volume of water collected
Q=
Time taken
−3
5× 10
=
22.57
=2.257×10−4
Observations & Data
Pressure Discharge Left Right Torque (Nm) Rotational Efficiency
(Pa) QQ (m³/s) Balance Balance Speed ω (%)
(N) (N) (rad/s)
34,000 2.257×10−4 0.25 1.5 (1.5−0.25)×4×10−3 =0.08 54.87 1.08
34,000 2.257×10−4 0 1 (1−0)×4×10−3 =0.064 90.16 1.42
34,000 2.257×10−4 0.5 2 (2−0.5)×4×10−3 =0.096 35.81 0.846
(1.08+1.42+0.846)
Average Efficiency = ≈ 1.12
3
Calculations
Sample Calculation for First Row:
Torque T =(1.5−0.25)×4×10−3 =0.08 Nm
Power Output W= T⋅ω =0.08×46.07 = 3.68W
Input Power PQ = 34000×2.257×10−4= 7.67 W
368
Efficiency η= ≈0.03706 =47.97%
47.67
Note: There may be rounding or instrument uncertainty leading to slight differences in
tabulated values.
Conclusion
The experiment successfully demonstrated the method to determine the efficiency of a Pelton
turbine. The observed efficiencies varied significantly across trials, likely due to variations in
loading and measurement error. The average efficiency was approximately 2.14%, which is
much lower than typical for such turbines, suggesting possible experimental losses or
inaccuracies.
Sources of Error
Friction losses in the turbine and shaft
Human error in reading balances
Calibration error in the tachometer
Inconsistent flow rate or water spillage
