72 EMMET—THE CURTIS STEAM TURBINE. [April 2, 
Velocity is imparted to the steam in an expanding nozzle so 
designed as to efficiently convert nearly all the expansive force, 
between the pressure limits used, into velocity in the steam itself. 
After leaving the nozzle, the steam passes successively through two 
or more lines of vanes on the moving element, which are placed 
alternately with reversed vanes on the stationary element. In pass- 
ing successively through these moving and stationary elements, the 
velocity acquired in the nozzle is fractionally abstracted, and 
largely given up to the moving element. Thus the steam is first 
thrown against the first set of vanes of the moving element, and 
then rebounds alternately from moving to stationary vanes until it 
is brought nearly to rest. By this means a high steam velocity is 
made to efficiently impart motion to a comparatively slowly moving 
element. The nozzle is generally made up of many sections adja- 
cent to each other, so that the steam passes to the wheels in a broad 
belt when all nozzle sections are in flow. ; 
This process of expansion in nozzle and subsequent abstraction 
of velocity by successive impacts with wheel vanes is generally 
repeated two or more times, the devices for each repetition being 
generally designated as a stage. ‘There may be various numbers of 
stages and various numbers of lines of moving vanes in each stage. 
The number of stages and the number of lines of vanes in a stage 
are governed by the degree of expansion, the peripheral velocity 
which is desirable or practicable, and by various conditions of 
mechanical expediency. 
Generally speaking, lower peripheral speeds entail more stages, 
more lines of vanes per stage, or both. Our general practice is to 
so divide up the steam expansion, that all stages handle about equal 
parts of the total power of the steam. 
The losses and leakages of the earlier stages take the form of 
more heat or more steam for the later stages, and are thus in part 
regained. Much water of expansion, which might occasion loss 
by re-evaporation, is drained out of each stage into that which 
succeeds it. 
The governing is effected by successive closing of nozzles and 
consequent narrowing of the active steam belt. The cut shows 
part of the nozzle open and part closed ; the arrows showing space 
filled by live steam. In the process of governing, the nozzles of the 
later stages may or may not be opened and closed so as to maintain 
an adjustment proportional to that of the first stage, which is 
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