Exploration and assessment of the environmental design space for commercial aircraft and future technologies

Abstract

Design and regulatory initiatives for aircraft noise and emissions should appreciate the integrated nature of the aircraft system. The computational ability exists to consider environmental and traditional performance objectives of aircraft concurrently. This context of multi-disciplinary system design is named the Environmental Design Space (EDS) and is studied in this thesis with an integrated aircraft-engine conceptual design framework. With this tool, the objectives of this thesis were to assess the fidelity and level of uncertainty of the design framework, to characterize the tradeoffs between aircraft noise, emissions and aircraft performance and to evaluate the system-level impacts of a future noise reduction technology. Assessment of the EDS framework was accomplished with a probabilistic model assessment methodology. The assessment involved the selection of stochastic inputs and generation of output distributions through Monte Carlo simulations. A sensitivity analysis of the key drivers of uncertainty and the user-defined input distributions is also provided. This methodology was applied to one of the framework modules, the NASA Engine Performance Program (NEPP), and found that the modeling error was subsumed within the modeling uncertainty. A sensitivity study indicated that the component efficiencies had the largest impact on the output distribution. When the level of NEPFP uncertainty was propagated to the system level, the resulting coefficient of variance for fuel burn was 4.1%. The tradeoffs between the competing EDS objectives were characterized through Pareto fronts generated by multi-objective genetic algorithms.

(cont.) The quantification of these trades for a given aircraft, 8 dB in cumulative EPNL vs. 8kg of LTO-NO[sub]x for example, give designers and regulators supporting information for their decisions. A future noise reduction technology, fan trailing edge blowing, was also evaluated at the system level. A probabilistic analysis of the technology design in the EDS framework revealed poor tolerance of engine cycle variability. A robust design procedure was employed, and showed that while the technology offered a flyover noise reduction of 11.9 dB, it incurred a fuel burn and LTO-NO[sub]x penalty of 2.8% and 11.0%, respectively.