1903.] EMMET—THE CURTIS STEAM TURBINE. fa 
always the primary source of governing. Some improvement of 
light-load economy may be effected by maintaining a relative 
adjustment of all nozzles; but in many cases the practical differ- 
ence in economy is not great, and automatic adjustment of nozzle 
opening in later stages is dispensed with in the interest of sim- 
plicity. In some machines an approximate adjustment is main- 
tained by valves in later stages, which open additional nozzles in 
response to increases of pressure behind them. ‘These are used as 
much for limiting the pressures in stage chambers as for maintain- 
ing the light load economy. 
The principle of the Curtis steam turbine is susceptible of appli- 
cation to a variety of purposes. Within the scope of this paper I 
intend to give only a general idea concerning existing designs for 
its application to electric generators. Its development, even for 
this purpose, is very recent, and will doubtless be subject to impor- 
tant future improvements. In its present state, however, it embod- 
ies many important advantages, as has already been stated. The 
most important of these advantages is the high steam economy 
which it affords under average conditions of service. This economy 
is shown by the accompanying curves, which are derived from 
actual tests of the first commercial machine of this type which was 
completed. This machine drives a dynamo of 600 Kw. capacity. 
The curves give its performance at a speed of 1500 R.P.M., which 
is a safe and practical speed for commercial operation, and which 
corresponds to a peripheral velocity of about 420 feet per second. 
The results, with superheat, given in these curves are not derived 
actually from tests of this turbine, but are plotted from data 
obtained on smaller turbines. They correspond to the results 
obtained on turbines of other types and are undoubtedly reliable. 
Curve 1 shows the steam consumption of this machine in pounds 
per kilowatt-hour output at various loads and under the conditions 
stated, the lower curve giving the steam consumption at various 
loads with 150 degrees superheat. 
Curve 2 shows the results which could be obtained from.this tur- 
bine if it were operated with high pressure and a high degree of 
superheat, these conditions of operation being perfectly practical 
with the machine, while with steam engines the use of such high 
temperatures would with ordinary constructions be prohibitive. 
The results shown by these curves are better than any heretofore 
produced by steam turbines of any make or size, and are very much 
