EXPERIMENTAL WORK ON FLOW OF STEAM. 139
The losses resulting from increased skin friction were very
considerable. With one set of movable buckets only, the
loss amounted to 6 per cent-that is, the impulse at 100 pounds
initial gage pressure was only 94 per cent of the impulse for
smooth buckets at the same pressure. The curves, Fig. 51,
show the relation between the impulse as received upon smooth
and upon rough buckets respectively. The runs made with
two extra sets of rough buckets placed before the set of mov-
able buckets show very much increased losses and indicate
that the loss is directly proportional to the number of sets
added. The investigators plotted a curve (not reproduced.
here) based on this indication, and concluded that, calling the
smooth buckets 100 per cent efficient, the following would.
result from the addition of successive sets of rough buckets
of the kind employed in the experiments.
One set smooth buckets..
rough
<
06
Two sets rough
Three "
Four "
Efficiency.
100 per cent.
94
82
(
61
58
12**
07
This means that if the working fluid were caused to pass
through four sets of such rough buckets as used, before strik-
ing the single movable row of rough buckets, the impulse
upon the latter would be less than half of what would be obtained
with one set of smooth buckets acted upon directly by the
jet from the nozzle.
The following inferences are drawn from the experimental
work discussed in the preceding pages:
1. Rate of flow, by weight, is greater through an orifice
with rounded entrance than if the entrance is sharp-cornered
or only slightly rounded.
2. Rate of flow, by weight, is decreased by the addition of
a nozzle. either diverging or straight, to the discharge side of
the orifice.
