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

Asi, pues, la tasa de1 flujo es simplemente el pro-
ducto de1 tiea de entrada y el componente radial de
velocidad:
(18) Q = (fn ; CR) 82 G$Y
Donde f represents la fraction de1 espacio libre en
el paso de entrada (fk 0,195). Asi, pues,
De la ecuacion de Euler, la torsi6n es
T = f&J (r;V2 cos al - r2V2 cos q)
por lo que
(20) T = CT )’ D3H
La velocidad de la maquina esti relacionada con la
velocidad periferica. De donde
2"l
(211 VI = 7
(ra.ra.;s por
Fin~mente. la potencia desarrollada es propor-
cional a la torsi6n y la velocidad. Por io que
(23) P = c, Y 02 Gg
Eliminando el diametro D entre las ecuaciones (22)
y (23) se obtiene la velocidad especifica definida coma
(24) N, =
ludF
p’/2[gH]5’4
From the Euler equation, the torque is
=I- = eQ (rlV2 cos al- r2V2 cos 42)
thus
(20) T = CT y D3H
The speed of the machine is related to the tip
speed. Hence
2”l
(21) Y = D (radianslsecj
(22)
V5g-l
l/J = C” D
Finally, the power developed is proportional to
torque and speed. Thus
(23)
P = CP Y D2 &ji$
Eliminating diameter D between Eqs. (22) and
(23) yields the specific speed defined as
(24) N,=
d=F-
e r/,[gH]514
N, in Eq. (24) is non-di.mensional. In normal prac-
tice, the specific speed has units and is defined
as
(25) ns =
n \/Bhp
(H)5/4
where n, Bhp, and H are rpm, English Bhp and ft
in the English system of units or rpm, Metric Bhp
and meters in the metric system. The conversion
is as fo!!owc* .I V.
N, en la ecuacion (24) no es dimensional. En la “S = 43.5 Ns (English Units)
practica normal, la velocidad especifica tiene
unidades y se define coma
(25) ns = ni&
“S = 193.1 Ns (Metric units using metric
horsepower)
“S = 166 Ns (Metric units using KW for power)
(H)5/4 Thus a turbine manufactured in Japan and
tested in Europe would have a specific speed 4.4
times higher than the same turbine tested in the
don& n, Bhp, y H son rpm, Bhp de1 sistema ingks y U.S.! One can only guess what the specific speed
pies en el sistema ingles de unidades o rpm, Bhp de1 will be on the moon!
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