Fluid Mechanics and Thermodynamics of Turbomachinery, 5e

of diffusion of kinetic energy in the rotor and stator rows, significantly influences the
stage efficiency.
Thermodynamics of the compressor stage
Axial-flow Compressors and Fans 149
The specific work done by the rotor on the fluid, from the steady flow energy equation
(assuming adiabatic flow) and momentum equation is
(5.1)
In Chapter 4 it was proved for all axial turbomachines that h0rel = h + 1 – 2 w 2 is constant
in the rotor. Thus,
(5.2)
This is a valid result as long as there is no radial shift of the streamlines across the rotor
(i.e. U1 = U2).
Across the stator, h0 is constant, and
(5.3)
The compression process for the complete stage is represented on a Mollier diagram
in Figure 5.3, which is generalised to include the effects of irreversibility.
FIG. 5.3. Mollier diagram for an axial compressor stage.