Multi-Objective Optimization of Turbofan Design Parameters for an Advanced, Single-Aisle Transport

Abstract

Considerable interest surrounds the design of the next generation of single-aisle commercial transports in the Boeing 737 and Airbus A320 class. Aircraft designers will depend on advanced, next-generation turbofan engines to power these airplanes. The focus of this study is to apply singleand multi-objective optimization algorithms to the conceptual design of ultrahigh bypass (UHB) turbofan engines for this class of aircraft, using NASA’s Subsonic Fixed Wing Project goals as multidisciplinary objectives for optimization. The independent propulsion design parameters investigated are aerodynamic design point fan pressure ratio, overall pressure ratio, fan drive system architecture (i.e., director geardriven), bypass nozzle architecture (i.e., fixedor variable-geometry), and the highand lowpressure compressor work split. NASA Project goal metrics – fuel burn, noise, and emissions – are among the parameters treated as dependent objective functions. These optimized solutions provide insight to the UHB engine design process and provide independent information to NASA program management to help guide its technology development efforts. This assessment leverages results from earlier NASA system concept studies conducted in 2008 and 2009, in which UHB turbofans were examined for a notional, nextgeneration, single-aisle transport. The purpose of these NASA UHB engine concept studies is to determine if the fuel consumption and noise benefits of engines having lower fan pressure ratios (and correspondingly higher bypass ratios) translate into overall aircraft system-level benefits for a 737 class vehicle.