System noise assessment of a tube-and-wing aircraft with geared turbofan engines

Abstract

The Airbus A320neo family and the Bombardier CSeries can come equipped with a geared turbofan of increased bypass ratio. Such an engine concept promises reduced engine noise generation if compared to conventional turbofan engines with lower bypass ratios. As a result, the dominance of other noise sources on-board of an aircraft with geared turbofan engines are emphasized and will become more relevant. Consequently, to get an understanding of the modified noise source ranking due to the new engine concept, a noise assessment of the overall aircraft noise as received on the ground is essential, i.e., a so called system noise assessment. For this study a DLR & TU Braunschweig aircraft design synthesis process with integrated noise prediction capabilities is applied. An interface to process external input data allows the implementation of high-fidelity simulation results for the geared engine concept into the overall simulation process, i.e. including all required engine parameters for the noise prediction. The focus lies on the comparison of existing engine concepts and their impact on the overall vehicle design, flight performance, and ultimately the system noise. The noise assessment is not limited to the overall vehicle noise as received on the ground but moreover the dominance and ranking of all individual noise sources is discussed. A direct comparison and evaluation of the flight performance and the system noise of the different vehicle variants under consideration is presented. Among the vehicle variants, one aircraft is adapted to better match the engine concept. A geared turbofan engine concept will come with an inherent and advantageous implication on the overall aircraft performance, i.e., reduced specific fuel consumption. Since such beneficial characteristics are identified in the simulation results, the overall vehicle design is consequently adapted to fully exploit these characteristics. Furthermore, several known measures to reduce the airframe noise contribution are simulated on board of the vehicles under consideration. The system noise assessment will identify the impact of these technologies on the overall aircraft noise for each variant. Finally, the geared turbofan engine is also installed on board of an earlier low-noise aircraft concept featuring engine noise shielding. The impact of the new engine in combination with shielding effects is assessed. It is demonstrated that the influence of low-noise airframe measures in combination with geared turbofan aircraft concept are promising, especially on an airframe architecture dedicated to engine noise shielding.