The polytropic efficiency and pressure ratio values at the different
operating points relevant to the un-deformed and
deformed impeller are shown in Fig. 12 (blade type A) and 13
(blade type B), where the flow coefficient is defined as
φ = Q
ND3 . (3)
The polytropic efficiency of the compressor stage is defined
as
ηp
H H s sTT
T T
H H =
( ) − − ( ) − ( ) −
( )
( ) −
3 1
3 13 1
3 1
3 1
ln . (4)
The pressure ratio is defined as the ratio of the diffuser exit
static pressure and the impeller inlet total pressure.
Π = P
P
3
01
.