Effect of Bypass Ratio on Optimal Fan Outer Pressure Ratio and Performance for Turbofan Engines

  • Rui XueEmail author
  • Jun Jiang
  • Anthony Jackson
Original Paper


This study was carried out to explore the effect of bypass ratio on optimal fan outer pressure ratio and the performance of turbofan engine with the same engine core. The member of Rolls-Royce Trent family, Trent-XWB, is chosen as the baseline engine. Based on the published data, a model for the simulation of engine performance was set up. Then, a series of engine models with different bypass ratios were established based on the same Trent-XWB engine core and the way to get optimal fan outer pressure ratio was derived. It was concluded that for the fixed engine core, when the bypass ratio was chosen, there would be one optimal outer pressure ratio existing which could make the thrust maximum and the specific fuel consumption reach minimum. By comparing the performance of the turbofan engines with different bypass ratios, it shows that the increase of bypass ratio results in higher thrust and lower specific fuel consumption. However, the additional cost like the increase of both drag and weight needs to be taken into account at the preliminary design stage in practice.


Bypass ratio study Optimal fan outer pressure ratio Engine performance 



Bypass ratio


Combustor outlet temperature


Fan inner pressure ratio


Fan outer pressure ratio


High pressure compressor pressure ratio


Intermediate pressure compressor pressure ratio


Intermediate pressure compressor


International standard atmosphere


Low pressure


Overall pressure ratio


Pressure ratio


Specific fuel consumption


Sea level static


Air mass flow rate



This work has been supported by the National Natural Science Foundation of China (Grant No. 51706170) and China Postdoctoral Science Foundation (Grant no. 2017M623185).

Compliance with ethical standards

Conflict of interest

The authors declare that there is no conflict of interest.


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Copyright information

© The Korean Society for Aeronautical & Space Sciences 2019

Authors and Affiliations

  1. 1.State Key Laboratory for Strength and Vibration of Mechanical Structures, Shaanxi Engineering Laboratory for Vibration Control of Aerospace StructuresSchool of Aerospace, Xi’an Jiaotong UniversityXi’anPeople’s Republic of China
  2. 2.AECC Xi’an Aero-Engine Control CompanyXi’anPeople’s Republic of China
  3. 3.Centre for Propulsion EngineeringCranfield UniversityBedfordshireUK

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