Range of Application for Micro Pelton Turbines
The Pelton turbine installations described in this treatise are substantially smaller than the ones described above. These turbines can be manufactured locally with good results. Different methods and various materials are described for the manufacturing of the buckets or of the runner as well as for different nozzle arrangements and the regulating mechanism.
Various constraints limit the application range for locally manufactured Pelton turbines. For instance with higher heads problems may arise with the penstock. Here not only the static pressure is relevant, but pressure waves may occur when the conduit is filled, or when the turbine is started or regulated. This can have disastrous consequences. High heads also imply high rotational speed which may cause problems with the rotor due to centrifugal forces in connection with dynamic forces. Larger wheels are generally built for higher discharge rates, which implies larger nozzles and buckets.
In the context of this publication only very small, locally manufactured Pelton turbines are dealt with. The application range of these should be within the following, reduced limits (see illustration 3):
maximum head:
300-200 m, limit set by dynamic and hydraulic forces on the buckets, torque on the shaft
minimum head:
10 m, limit set by small discharge and power output, large dimensions of wheel and low RPM
minimum discharge:
0,5lt/s, limit set by the small size of bucket
minimum power output:
O. 1 kW, limited power application
maximum power output:
50 kW, limited by size of turbine and design limits
minimum jet diameter:
4 mm, limit set by small size of buckets and by difficulty to concentrate the jet
maximum jet diameter:
80 mm, limit set by large size of buckets
These limits are not compulsory, but can be taken as guidelines, taking into consideration the local conditions for manufacturing, such as availability of materials, casting facilities, testing equipment and others.
In comparison to what is said in chapter 1.2 on the latest developments of Pelton turbines, these limits considerably restrict the application range of micro Pelton turbines. But they still open a new, interesting field for the local fabrication of turbines.