Fluid Mechanics and Thermodynamics of Turbomachinery, 5e

110 Fluid Mechanics, Thermodynamics of Turbomachinery
Stage loading coefficient, y =DW/U 2
3.0
2.0
1.0
h tt = 0.82
Also, y =DW/U 2 = f(tan a2 + tan a3) = f(tan b 2 + tan b 3) = 2f tan b 2,
Thus, using the above expressions,
e = 140∞
0.84
From these expressions the flow angles can be calculated if values for y and f are specified.
From an inspection of the velocity diagram,
Substituting the above expressions into eqn. (4.9a):
120∞
0.92
0.5 1.0 1.5
Flow coefficient, f = cx /U
The performance chart shown in Figure 4.11 has been derived using the above expressions.
This is similar in its general form to Figure 4.10 for a 50% reaction, with the
100∞
0.86
0.90
0.86 0.84
FIG. 4.10. Design point total-to-total efficiency and deflection angle contours for a
turbine stage of 50% reaction.
0.88
80∞
0.82
60∞
40∞
20∞