Handbook of Turbomachinery Second Edition Revised - Ventech!

Figure 12 Smith’s chart for stage zero-clearance total-to-total efficiency as
function of mean-radius flow and loading coefficient. (Replotted from Ref. 11
with permission of the Royal Aeronautical Society).
measured efficiency for 70 turbines. All the turbines have a constant axial
velocity across the stage, zero incidence at design point, and reactions
ranging from 20% to 60%. Reynolds number for the turbines range from
100,000 to 300,000. Aspect ratio (blade height to axial chord) for the tested
turbines is in the range of 3–4. Smith’s chart does not account for the effects
of blade aspect ratio, Mach number effects, or trailing-edge thickness
variations. The data have been corrected to reflect zero tip clearance, so the
efficiencies must be adjusted for the tip clearance loss of the application.
Sieverding [10] considers Soderberg’s correlation to be outdated but
still useful in preliminary design stages due to its simplicity. In Soderberg’s
[12] correlation, blade-row kinetic energy losses are calculated from
ðVoÞ 2
ideal
V2 o
V2 o
¼ x
¼ 105
Rth
Copyright © 2003 Marcel Dekker, Inc.
1=4
ð1 þ xrefÞ 0:975 þ 0:075 cx
n h io
1
h
ð52Þ