494 APPLIED MECHANICS 
15° to 25° in outward flow and parallel flow turbines. ¢, varies from = 
10° to 25°. ¢ ae 
Areas of Passages.—A, and A,=areas of guide passages and wheel 4 
INWARD 
FLOW 
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passages respectively at exit, measured at right angles to direction of 
flow. 
If m is the number of passages, and b the distance between the 
crowns, then, referring to Fig. 796, the area of 
the passages referred to above is A=ndb. If t 
denotes the thickness of the guides or vanes, 
then, approximately, 
n(d + t) = sin 6, and A = (2rr sin 6 ~ nt)b. 
2rr 
The ratio A,+A, may be assumed in 
commencing the design of a turbine. A,+A, varies from 0°5 to 1 in 
outward flow turbines, and from 0°6 to 1°5 in inward flow turbines. 
In parallel flow turbines A,~+ Ag, is usually about 1. 
Fig. 796. 
