Design inquiry of an ultra-high-pressure-ratio component of multi-stage axial flow compressors

For increasing the overall pressure ratio from 50∶1 to 70∶1 of the high bypass ratio turbofan engine, a 5-stage ultra-high-pressure-ratio axial-flow component with pressure ratio of 2.2∶1 was designed, and connected to the exit of a 10-stage high-pressure compressor with pressure ratio of 23∶1. The feasibility to improve the overall pressure ratio with a complete axial-flow configuration was explored. The design was implemented through the process including component 1-D overall aerodynamic design, S2 through-flow inverse problem and blade modeling and 3-D computational fluid dynamics verification. The specific methods such as positive pre-whirl at each stage, large-deviation-angle rotor tip and positive bowed stator were used in the process. Under the condition of achieving the prescribed aerodynamic design parameters, it’s recommended to set the rotor tip clearances to 0.2 mm rather than 0.3 mm, otherwise the compressor stall margin would drop significantly and its stable working range would be narrowed due to the geometric characteristics of large hub-tip ratio and the relatively larger rotor tip clearances. In the terms of structure, the design may lead to some issues that must be solved before the compressors enter into service, such as a huge number of blades and the higher machining costs of each stage.