International Journal of Smart Energy Technology and Environmental Engineering
Volume 5, Issue 1, March 2026
https://setee.globalpublisher.org/
The bypass ratio trade-off in modern turbofan engines: a technical, economic, and environmental review
Mohammadhossein Ebrahim ¹* , Ali Behzadi¹ , Ali Ghaniaraghi¹
1- Department of Mechanical Engineering, ST.C., Islamic Azad University, Tehran, Iran *Corresponding Author: mheb.mohsen@gmail.com
ABSTRACT
Turbofan engines, as the dominant propulsion technology in modern commercial and cargo aircraft, play a decisive role in operational efficiency, air transport economics, and the environmental impact of the aviation industry. This paper first introduces the operating principles and main components of the dual-flow turbofan engine, then examines its technical advantages and disadvantages in comparison with turbojet and turboprop engines. It further reviews the commercial, military, and industrial applications of turbofan engines and analyzes economic perspectives, including fuel cost, maintenance cost, and the savings achieved through modern technologies such as the Geared Turbofan. The final section addresses the environmental effects of turbofan engines, including CO2 and NOx emissions, and modern assessment approaches such as Exergo-Environmental and Life Cycle Assessment. The results indicate that despite remarkable progress in increasing bypass ratio and improving combustion efficiency, achieving the aviation industry’s long-term emission-reduction targets will require the simultaneous development of novel propulsion technologies and Sustainable Aviation Fuels (SAF).
Keywords:
Turbofan engine; Combustion efficiency; Bypass ratio; Environmental pollution; Economic analysis; Exergy
REFERENCES
- Ranasinghe K, Guan K, Gardi A, Sabatini R. Review of advanced low-emission technologies for sustainable aviation. Energy. 2019;188:115945. doi:10.1016/j.energy.2019.115945
- Aygun H, Turan O. Environmental impact of an aircraft engine with exergo-life cycle assessment on dynamic flight. J Clean Prod. 2021;279:123729. doi:10.1016/j.jclepro.2020.123729
- Balli O. Exergy modeling for evaluating sustainability level of a high by-pass turbofan engine used on commercial aircrafts. Appl Therm Eng. 2017;123:138-155. doi:10.1016/j.applthermaleng.2017.05.068
- Balli O, Sohret Y, Karakoc TH. The effects of hydrogen fuel usage on the exergetic performance of a turbojet engine. Int J Hydrogen Energy. 2018;43:10848-10858. doi:10.1016/j.ijhydene.2017.12.178
- Akdeniz HY, Balli O, Caliskan H. Energy, exergy, thermoecologic, environmental, enviroeconomic and sustainability analyses and assessments of the aircraft engine fueled with biofuel and jet fuel. J Therm Anal Calorim. 2023;148:3585-3603. doi:10.1007/s10973-023-11982-z
- Aygun H, Caliskan H. Environmental and enviroeconomic analyses of two different turbofan engine families considering landing and take-off (LTO) cycle and global warming potential (GWP) approach. Energy Convers Manag. 2021;248:114797. doi:10.1016/j.enconman.2021.114797
- Balli O, Caliskan H. Turbofan engine performances from aviation, thermodynamic and environmental perspectives. Energy. 2021;232:121031. doi:10.1016/j.energy.2021.121031
- Xue R, Jiang J, Jackson A. Effect of bypass ratio on optimal fan outer pressure ratio and performance for turbofan engines. Int J Aeronaut Space Sci. 2019;20:157-164. doi:10.1007/s42405-018-0134-z
- Chen L, Zafar A, Xu Z, Zhong S, Wang M, Fan Y, Zhang Y, Shi W, Hu X. Comparative analysis of emission reduction and combustion performance in aviation engines: The role of sustainable aviation fuel. Prog Aerosp Sci. 2025;101172. doi:10.1016/j.paerosci.2025.101172