old generator turbin pelton

Turbine Design

Turbines can be divided into two categories based on their principle of operation:

Impulse turbine- Operates in air, driven by jet(s) of water that remain at atmospheric pressure before and after making contact with the runner blades.

Reaction turbine- Rotor is fully immersed in water and enclosed in a pressure casing. Runner blades are profiled so that pressure differences across them impose lift forces, which cause the runner to rotate.

Turbine Type	Head Classification:
Impulse	High (>50m) Pelton Turgo Multi-jet Pelton	Medium (10-50m) Crossflow Turgo Multi-jet Pelton	Low (<10m) Crossflow
Reaction		Francis (spiral case)	Francis (open-flume) Propeller Kaplan

Impulse turbines

Impulse turbines tend to be better for microhydro projects (especially in developing countries) for several reasons:

• More tolerant of sand and other particles in the water.
• Better access to working parts.
• No pressure seals or glands around the shaft.
• Easier to fabricate and maintain.
• Better part-flow efficiency.
• Unsuitable for low-head sites.

Pelton Turbine

A Pelton turbine is jet-fed water from a nozzle attached to the penstock. The water flows from the nozzle tangential to the path of the runner. Pelton turbines are the most efficient impulse turbines and can be designed with a single jet or multiple jets.

Crossflow Turbine

Water passes transversely through in a crossflow turbine, rather than axially or radially. The crossflow turbine has lower efficiency than the Pelton turbine, but its design is suitable for a wide range of heads and power ratings. Additionally, it can be easily manufactured with limited materials (e.g. the runner blades can be fabricated from lengths of pipe cut into strips).

(http://www.ossberger.de/cms/en/hydro/) 


(European Communities, Layman's Guidebook on how to develop a small hydro site)
smb:https://wiki.thayer.dartmouth.edu