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Effect of Bypass Ratio on Optimal Fan Outer Pressure Ratio and Performance for Turbofan Engines
Ruixue Zhang,Jun Jiang,Anthony Jackson 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.1
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.
Rui Xue,Jun Jiang,Xing Zheng,Jian-liang Gong,Anthony Jackson 한국항공우주학회 2020 International Journal of Aeronautical and Space Sc Vol.21 No.2
With the development of civil aero-engines, the noise emission is now an essential issue to be considered during engine design. In this study, the preliminary design for a model fan, which was used for the fan noise estimation, was carried out. The fans with different bypass ratios, different tip speed as well as different aspect ratio were designed and the rough dimensions of the fan were obtained. Based on the dimension and performance of the fan, the effect of fan bypass ratio, tip speed, rotor blade numbers, and rotor–stator spacing on noise generation was investigated. The results indicate that the fan noise can be reduced as high as 10 dB by the increase of bypass ratios, and fewer rotor blade numbers and larger rotor–stator spacing are proved to be benefit to the fan noise reduction as well. However, lower tip speed does not achieve the noise reduction as expected. This is because more rotor blades are added to maintain the constant fan pressure ratio for the fan with lower tip speed. The study demonstrates that trade-off study should be carried out when considering fan noise reduction during engine design.