Energetic and Exergetic Analysis of High-Bypass Turbofan Engines for Commercial Aircraft: Part I—Operation and Performance

Despite substantial advances in turbofan engineering, a crucial gap persists: there remains the need for an all-inclusive comparative analysis that includes real-world operational data and evaluates the performance of modern turbofans used in aviation. Specifically, systematic investigations that examine the exergy and efficiency of turbofan engines for takeoff and cruise remain scarce. Further, the current literature needs to address rigorous performance assessments that include simultaneous consideration of the combined effects of ambient conditions (e.g., temperature, density, relative humidity), Mach number, and turbine inlet temperature on high-bypass turbofan engines used in modern, commercial aircraft. Energetic and exergetic analyses were conducted on five commercial high-bypass turbofan engines with different configurations for both takeoff and cruise flight modes. The computational thermodynamic models developed showed strong correlation with manufacturers’ specifications. Performance evaluations included variations in ambient conditions, altitude, Mach number, and turbine inlet temperature. Results demonstrate that three-spool engine architecture exhibits 70–71% reduction in exergy destruction between flight phases compared to 62.5% for two-spool designs, indicating greater operational adaptability. The combustion chamber emerged as the dominant contributor to irreversibilities, representing approximately 55–58% of overall exergy destruction during takeoff operations. Results demonstrate that increased ambient temperature and/or humidity increase both degraded exergetic efficiency and thrust-specific fuel consumption, and that Mach number and altitude influenced efficiency metrics through ram compression and density effects, while higher turbine inlet temperatures enhanced exhaust kinetic energy via increased thermal input. We show that cruise operations demonstrated superior exergetic efficiency (68–74%) compared with takeoff (47–60%) across all engine configurations. Our results confirm the fundamental trade-off in turbofan design: for long-range applications, high-bypass engines prioritize propulsive efficiency, while for power-intensive operations, moderate-bypass configurations deliver higher specific thrust.