Handbook of Turbomachinery Second Edition Revised - Ventech!

expression:
Where
E ¼ uðV1 uÞð1 þ cos b 2Þ ð9Þ
u ¼ blade speed.
V1 ¼ jet speed.
b 2 ¼ blade angle at the exit.
The maximum power is obtained when b 2 is zero. However, when the blade
angle is zero, water exiting from one bucket would strike the back of the
succeeding bucket, so that the overall efficiency of the turbine would be
reduced. Hence, the value of b 2 is normally set to 10–158.
The bucket of a typical Pelton wheel is shown in Fig. 5. For reasons of
symmetry, the jet emerging from the nozzle is split into two parts and the
fluid is equally distributed in the hemispherical buckets. Theoretically the
centerline of the bucket, called the splitter, should be shaped like a cusp,
with the two hemispheres meeting at the center, making the angle of contact
of the two surfaces zero. However, this is not possible due to two reasons:
first because of the difficulty in manufacturing such an intersection, and
second because of the entrained sand and other abrasive particles in the jet,
which invariably erode the splitter surface. Typical dimensions of the bucket
Figure 5 Typical Pelton wheel dimensions.
Copyright © 2003 Marcel Dekker, Inc.