Book Description

This thesis (a) establishes the design trades and limitations of supersonic transport propulsion systems in terms of take-off noise reduction, (b) identifies the attributes, quantifies the potential, and assesses the impact of advanced take-off trajectories designed for noise reduction, and (c) formulates a reduced-order model to scale these results for supersonic transport of different size classes and cruise Mach numbers. The propulsion system design trades established in this thesis show that clean- sheet engines do not enable supersonic transport to meet current subsonic transport noise limits when using conventional take-off trajectories. The impact of derivative engines on the cumulative noise levels is found to be small (1.4 EPNdB). In fact, regardless of whether a clean-sheet or derivative engine is selected, a Mach 1.4 business jet is shown to exceed the current cumulative noise limit by at least 15.5 EPNdB. Further noise reduction of the jet noise dominant engines is prevented by the fan size constraint imposed to limit wave drag during supersonic cruise. Advanced trajectories are proposed to reduce take-off noise by capitalizing on excess engine thrust and improved aerodynamic efficiency at higher take-off speeds. These novel trajectories use (i) automatic continuous control of thrust and high-lift devices, (ii) increased take-off speed, and (iii) reduced cut-back altitude, compared to conventional trajectories currently used for subsonic transport. For the aircraft examined, although these trajectories reduce the 65 dB-A community noise contour area by 63.8%, they only reduce cumulative certification noise by 10.6 EPNdB, which is insufficient to meet current subsonic transport noise limits. Additionally, advanced trajectories with the lowest community noise do not yield the lowest certification noise, which warrants re-examination of supersonic transport noise standards. On the contrary, engine NO[subscript x] standards are representative for supersonic transport using advanced take-off trajectories and thus do not need to be modified, as the impact of these trajectories on the mass of NO[subscript x] emissions during climb-out is small (16.1%). Last, a first-of-its-kind reduced-order model for supersonic transport take-off noise scaling shows that, as cruise Mach number increases, supersonic transport take-off noise levels increase while the thrust cut-back noise reduction potential decreases. This scaling rule enables equally stringent standard setting for noise certification of supersonic transport across a broad range of size classes and cruise Mach numbers.