Conceptual Development of Quiet Turbofan Engines for Supersonic Aircraft

This is a joint thermodynamic and acoustic study of engines for next-generation supersonic aircraft. It explores e xed-cycleconceptswith potentialforquiettakeoffand efe cientcruise.Thee owpath issimple, withoutmechanical suppressors.Thestrategyistotakearepresentativestate-of-the-artmilitaryturbofanengineandincreaseitsbypass ratio to a moderate value. The engine core stays the same. Three exhaust cone gurations are considered: mixed e ow,coaxialseparatee ow,andeccentricseparatee ow.Engine-cycleanalysispredictsthermodynamicperformance and nozzle exhaust conditions at takeoff and Mach 1.6 cruise. Subscale experiments duplicate the static exhaust conditionsattakeoff powerand measurethefar-e eld sound.Flyoverperceived noiselevelsareestimated fora twinengineaircraftin the120,000-lb class.In termsofeffectiveperceivednoiselevel (EPNL),theeccentricarrangement is 6.5 dB quieter than the mixed-e ow arrangement and 5 dB quieter than the coaxial cone guration. Spectral- and time-domainanalysesindicatethattheeccentricexhaustisfreeofstrongMachwaveradiation.Theacousticbenee t of the eccentric arrangement, combined with faster climb afforded by the modie ed engine, leads to a reduction of 14 dB in EPNL. Compared to the baseline engine, the specie c fuel consumption of the modie ed engine is about 13% less at subsonic climb and 3% less at supersonic cruise.