| The
prototype efficiency test for an operational unit is
the first step prior to the capacity-enlarging refurbishment.
Once the test is completed, the efficiency of the turbine-generator
unit can be assessed. Only by this means, can the refurbishment
results be testified. The prototype efficiency
of a unit cannot be measured directly by instruments.
By measuring the output, discharge, water head and
other parameters, the efficiency of the unit under
different working conditions can be calculated.
The ultrasonic wave method for the efficiency
test has a number of merits:
1. the measuring result is much more accurate
2. the sensors are much easier to fix
or remove
3. the flow field is not affected during
the test, and almost no additional head loss
4. the sensors respond instantaneously
and the momentary flow can be measured.
5. the automatic data-logging be achieved
and the measurements be made on line
6. cost effective
The measuring methods, conditions and
the accuracy of ultrasonic flow-meter:
| Measuring methods |
Conditions |
Accuracy(%) |
| Material |
Dia. of pipe |
Straight length of pipe |
| Internally sticking |
Various |
>=Ø1.2m |
Len. of upstream>=5D
Len. of downstream>=2D |
¡À0.5 |
| Externally sticking |
Penstock |
Ø0.1-3m |
Len. of upstream>=10D
Len. of downstream>=3D |
¡À1.0-1.5 |
| Open channel |
Various sections with the width
less than 1000m |
¡À1.5-2.0 |
Here, D is the diameter of the penstock
|
