Hydro-power plant equipped with Pelton turbines: basic experiments relating to the influence of backpressure on the design

Abstract

Free-jet turbines working under backpressure conditions represent an economical alternative to conventional hydro-electric plant configurations. However, the air introduced into the tailwater generates an air/water mixture. Its reaction to a rising ambient pressure is at present being studied at the above Institute. This report deals with the effect an increase in ambient pressure has on the volume and consistency of the two-phase mixture and the rise velocity of air bubble swarms. In addition, a test set-up is described which was used to study the physical reaction of the water/air mixture to a change in ambient pressure conditions. The results and their effects on the configuration of free-jet turbines working under backpressure are discussed.

The state-of-art of design and research for Pelton turbine casing, weight estimation, counterpressure operation and scientific challenges

“…For example, the largest Pelton turbines in the world (in Bieudron, hydraulic head 1,869 m and design flow rate 25 m 3 /s), were designed to supply naturally 6 m 3 /s of air to the turbine casing [ 42 ]. However, little is known about the influence of overpressure on air/water mixtures produced by a plunging free jet, as occurring in Pelton turbines [ 43 ]. One additional challenge is the understanding of the detrainment of air that might occur during counterpressure operation (also called backpressure) operation [ 41 ].…”