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5.6 Laboratory Test of a Pelton Turbine
The maximum head and the flow rate of the pump are 24 m and 4 l/s at 2900 rpm.
Pump pressure, and so turbine inlet pressure, is controlled by means of a manual
valve. Flow rate is measured by a triangular weir between two reservoirs. Waves on
the water surfaces are damped with bulkheads. The turbine power is adjusted with
an eddy-current brake with a swinging suspended stator, kept in balance by a lever
arm. The bending of the arm is measured with strain gauges in a Wheatstone bridge
and is the measure for the torque. The eddy current brake excitation is set for torque
adjustment.
5.6.2 Measurements
The hydraulic input power of the turbine follows from
• The mass flow rate read out on the gauge of the highest reservoir, calibrated in
flow rate units ( Q in l/s).
• The static pressure within the supply duct to the injector, just upstream of the
turbine, read out on a metal manometer ( H in m water column).
• The dynamic pressure calculated from the velocity within the supply duct to the
injector, the duct diameter being 40.0 mm.
The manometric head in m water column is H m = H + v
2
/2g and the hydraulic power
available is P = ρ QgH m (the height difference between the nozzle exit and the tailwater is not taken into account).
The mechanical output power of the turbine follows from
• The rotational speed measured with a magnetic tachometer. A wheel with six
teeth rotates in front of a magnetic transducer and induces a voltage proportional
to the rotational speed. Voltage is read out analogously from a dial with pointer.
Read the 5000 rpm scale.
• The brake torque read out from the voltmeter in the Wheatstone bridge with
strain gauges connected to the brake arm. Read-out is in mKp. This is the old
DIN-notation for mkgf. The torque in Nm is found by multiplying by 9.81. This
factor may be rounded to 10. Setting the scale to 0.4 mKp and reading it as if it
were 4 Nm is a practical method.
5.6.3 Measurement Procedure
• Set the flow rate by opening the regulating needle from the fully closed position:
2, 4, 6, 8 or 10 rotations (4, 6 or 8 rotations yield the best efficiency).
• Vary the rotational speed of the turbine by adjusting the eddy current brake excitation from idle to maximum attainable load. Select eight operating points
5.6 Laboratory Test of a Pelton Turbine
The maximum head and the flow rate of the pump are 24 m and 4 l/s at 2900 rpm.
Pump pressure, and so turbine inlet pressure, is controlled by means of a manual
valve. Flow rate is measured by a triangular weir between two reservoirs. Waves on
the water surfaces are damped with bulkheads. The turbine power is adjusted with
an eddy-current brake with a swinging suspended stator, kept in balance by a lever
arm. The bending of the arm is measured with strain gauges in a Wheatstone bridge
and is the measure for the torque. The eddy current brake excitation is set for torque
adjustment.
5.6.2 Measurements
The hydraulic input power of the turbine follows from
• The mass flow rate read out on the gauge of the highest reservoir, calibrated in
flow rate units ( Q in l/s).
• The static pressure within the supply duct to the injector, just upstream of the
turbine, read out on a metal manometer ( H in m water column).
• The dynamic pressure calculated from the velocity within the supply duct to the
injector, the duct diameter being 40.0 mm.
The manometric head in m water column is H m = H + v
2
/2g and the hydraulic power
available is P = ρ QgH m (the height difference between the nozzle exit and the tailwater is not taken into account).
The mechanical output power of the turbine follows from
• The rotational speed measured with a magnetic tachometer. A wheel with six
teeth rotates in front of a magnetic transducer and induces a voltage proportional
to the rotational speed. Voltage is read out analogously from a dial with pointer.
Read the 5000 rpm scale.
• The brake torque read out from the voltmeter in the Wheatstone bridge with
strain gauges connected to the brake arm. Read-out is in mKp. This is the old
DIN-notation for mkgf. The torque in Nm is found by multiplying by 9.81. This
factor may be rounded to 10. Setting the scale to 0.4 mKp and reading it as if it
were 4 Nm is a practical method.
5.6.3 Measurement Procedure
• Set the flow rate by opening the regulating needle from the fully closed position:
2, 4, 6, 8 or 10 rotations (4, 6 or 8 rotations yield the best efficiency).
• Vary the rotational speed of the turbine by adjusting the eddy current brake excitation from idle to maximum attainable load. Select eight operating points