Small Decentralized Hydropower Program National ... - Cd3wd.com

Esto puede expresarse Gmodamente en tkrminos
de1 sigma de Thomas
HDv
(50) OT = --ii-
thus the maximum turbine set!ing above tailwater is
(54)
P atm PV
zBmax = y - y - OTC H
wherein OTC is obtained from Fig. 15. ZBmax can
donde HDv es la caida neta de succi6n positiva y H, be negative implying that the turbine must be set
la &da disponible. El valor ctitico de 0-r es una fun- below the tailwater elevation.
ci6n de la velocidad especifica, tal coma se ilustra en As an example, consider a 500 kW machine
la figura 15. operating at 500 rpm under a head of IO meters.
14 = ;1p1/2 (rpm, Hp, ft)
j-$5/4
20 30 60 100 200 300
NO CiMtation
Francis Turbines
0.011 I I I I I
0.4 0.8 1.6 3.2 6.4
cd112
N, =- (non-dimensional)
(g f-4314
Figura 15 Indice de Cavitacih coma Funcih de la Velocidad Especifica
Figure 15 Cavitation Index as a Function of Specific Speed
141