Modern high bypass turbofan engines have single stage fans with a low hub-
An alternative single stage fan performance description employs the hypothesis that the overall fan performance is not affected by variations in bypass ratio. The overall fan performance map is completed by an additional table with core stream efficiency.
The enhanced single stage fan map is used as follows:
During cycle design calculations, when scaling the map, the bypass ratio as well as the pressure ratio and efficiencies for the core and bypass streams are known. Given or assumed values for fan tip speed, hub-
Smooth C 8.3 makes the creation of a core efficiency table simple. After smoothing the overall fan map click the Go to Secondary Map button.You will get an estimate for the core efficiency map which you can modify easily. Due to the low Mach numbers the core stream efficiency values will be higher than the overall efficiency of the fan. Furthermore, the efficiency islands will be wider.
Compare the overall fan map with overall efficiency contour lines and with core efficiency contour lines to see the difference.
More details about this enhanced fan performance model can be found in:
An Enhanced Off-