Aerothermodynamic Off-Design Performance Study of a Fixed Double Bypass Duct Turbofan Engine

In this paper, a turbofan engine with double bypass duct (DBP) was studied at design point and off-design conditions. This engine is a separate exhaust, two spool turbofan engine with bleed, turbine cooling, power extraction, and convergent exhaust nozzles. Bypass ratio of main and secondary duct is equal one. Also, a typical turbofan engine with one bypass duct is considered as the benchmark case (simple engine) and its bypass ratio is 2. Simulation results show that DBP engine produces 5.4% thrust more than the simple engine at M=0.8 and altitude of 9296.4 m (design point). DBP engine thrust is more than the simple engine at SL altitude and 9296.4 m at off-design conditions in all flight Mach numbers ranging from 0 to 0.8. Moreover, the double bypass duct engine SFC is lower than the simple engine at prementioned off-design conditions. Thrust per mass flow rate (F/m ̇) was also studied. By increasing F/m ̇, specific fuel consumption is decreased for both engine types. Another interesting finding is that at constant F/m ̇, DBP engine SFC is lower than simple engine at all flight altitudes.