Novel cycles deployment study for a silent aircraft

Aircraft noise is nowadays considered a pollutant like exhaust gases. Moreover, future requirements for aircraft certification impose a remarkable reduction in noise emission in the next 20 years. Since current technologies are insufficient to achieve the target, new technologies have to be developed, both for engines and airframes. In this paper, three novel engine cycles have been studied from a preliminary and theoretical point of view, considering noise and fuel consumption reduction as key design drivers. The innovative cycles analysed are: Variable Fan Nozzle Area (VFNA), Constant Volume Combustor (CVC) and Inter Cooled Recuperated (ICR). A parametric analysis has been performed for each one of them in order to select the best cycle; then, the three optimums have been compared. The designed VFNA engine provides the largest reduction in jet noise (64%) in comparison to the baseline, whilst the CVC has the lowest fuel consumption. However, both use two fans per engine, with weight and drag penalties. A further noise reduction is obtained installing the engines upon the wings, and not beneath them as in conventional designs. Obtained results show that noise shielding technique is responsible for a 20 dB decrease in OASPL, leading to a noise level, perceived on the ground, lower than 60 dB. This value implies a full satisfaction of the new environmental laws. Finally, the three propulsion systems have been installed on a medium range, twin engine aircraft and its flight performance has been evaluated. Simulations establish the superiority of the novel cycles against the baseline, in terms of reduced fuel consumption for the given mission.