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Under the NASA University Leadership Initiative (ULI) program, a team of universities are collaborating on the advancement of technologies a hybrid turboelectric regional jet, with an intent to enter service in the 2030 timeframe. In the previous studies of the ULI program, the in-service benefits of the technologies under development were analyzed by integrating the technologies of interest to a 2030 regional jet with a hybrid turbo-electric distributed propulsion system. As the program has progressed, the projected performances for each technology and subsystem have been updated. This paper presents an update in the sizing and performance analysis of the regional jet with the hybrid turbo-electric distributed propulsion system, by integrating the updated values of the technologies and subsystems to the vehicle. The updates in this paper include the DC/AC conversion links, efficiency of generator and cabling losses, weight of the wires, the battery cooling through the environmental control system, motor and inverter cooling by the thermal management system, and the redundancy strategy of the propulsion system. The updates of the results from the integrated model include the overall efficiency of the propulsion system, mission fuel savings, mission energy flow distribution, and the optimal hybridization rate in climb and cruise. The overall fuel saving benefit for the target 600-nmi mission is 19.9% compared to the baseline aircraft.

A prediction method for fan/compressor discrete-frequency tone generation and transmission is presented. The method is based on internal unsteady aerodynamics, coupled with an acoustic field described in terms of spinning modes. The sound-pressure levels generated by the rotor alone and the wake interaction between adjacent blade rows are calculated. The analysis of the sound propagation in the duct in the presence of axial and circumferential flows is described and incorporated in the prediction method. The analytical results are compared with experimental data and are shown to be in good agreement.

A study of various fan/compressor noise reduction methods is presented. The analytical treatment of the basic mechanisms of fan/compressor noise generation is described. The results are presented in parametric form and indicate the effects of fan/compressor design, number of blades, vane/blade ratio, aerodynamic parameters, and blade row spacing on pure tone noise reduction. These results are based on nonsteady aerodynamic treatment of wake and potential interaction effects and theoretical extensions of spinning mode theories.

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