Fluid Mechanics and Thermodynamics of Turbomachinery, 5e

Stage loading coefficient, y =DW/U 2
3.0
2.0
1.0
0
h tt = 0.82
120∞
e R = 140∞
Axial-flow Turbines: Two-dimensional Theory 111
0.84
0.92
0.5 1.0 1.5
Flow coefficient, f = c x /U
highest efficiencies being obtained at the lowest values of f and y, except that higher
efficiencies are obtained at higher values of the stage loading but at reduced values of
the flow coefficient.
Total-to-static efficiency of stage with axial velocity at exit
100∞
A single-stage axial turbine will have axial flow at exit and the most appropriate
efficiency is usually total-to-static. To calculate the performance, eqn. (4.10a) is
used:
With axial flow at exit, c1 = c 3 = c x, and from the velocity diagram, Figure 4.12,
0.86
80∞
0.88
0.90
FIG. 4.11. Design point total-to-total efficiency and rotor flow deflection angle for a
zero reaction turbine stage.
60∞
40∞
0.86
0.84
0.82