Challenges of future aircraft propulsion: A review of distributed propulsion technology and its potential application for the all electric commercial aircraft

Aerodynamic technologies to improve aircraft performance

The noise goal of the Silent Aircraft Initiative, a collaborative effort between industry, academia and government agencies led by Cambridge University and MIT, demands an airframe design with noise as a prime design variable. This poses a number of design challenges and the necessary design philosophy inherently cuts across multiple disciplines involving aerodynamics, structures, acoustics, mission analysis and operations, and dynamics and control. This paper discusses a novel design methodology synthesizing first principles analysis and high-fidelity simulations, and presents the conceptual design of an aircraft with a calculated noise level of 62 dBA at the airport perimeter. This is near the background noise in a well populated area, making the aircraft imperceptible to the human ear on takeoff and landing. The all-lifting airframe of the conceptual aircraft design also has the potential for a reduced fuel burn of 124 passenger-miles per gallon, a 25% improvement compared to existing commercial aircraft. A key enabling technology in this conceptual design is the aerodynamic shaping of the airframe centerbody which is the main focus of this paper. Design requirements and challenges are identified and the resulting aerodynamic design is discussed in depth. The paper concludes with suggestions for continued research on enabling technologies for quiet commercial aircraft.

/pdf/airframe-design-for-silent-aircraft-2rnk944b2k.pdf

Airframe Design for "Silent Aircraft"

Electrification of the propulsion system has opened the door to a new paradigm of propulsion system configurations and novel aircraft designs, which was never envisioned before. Despite lofty promises, the concept must overcome the design and sizing challenges to make it realizable. A suitable modeling framework is desired in order to explore the design space at the conceptual level. A greater investment in enabling technologies, and infrastructural developments, is expected to facilitate its successful application in the market. In this review paper, several scholarly articles were surveyed to get an insight into the current landscape of research endeavors and the formulated derivations related to electric aircraft developments. The barriers and the needed future technological development paths are discussed. The paper also includes detailed assessments of the implications and other needs pertaining to future technology, regulation, certification, and infrastructure developments, in order to make the next generation electric aircraft operation commercially worthy.

/pdf/a-review-of-concepts-benefits-and-challenges-for-future-1rye8t7l0d.pdf

A review of concepts, benefits, and challenges for future electrical propulsion-based aircraft

A system noise assessment of a hybrid wing body configuration was performed using NASA's best available aircraft models, engine model, and system noise assessment method. A propulsion airframe aeroacoustic effects experimental database for key noise sources and interaction effects was used to provide data directly in the noise assessment where prediction methods are inadequate. NASA engine and aircraft system models were created to define the hybrid wing body aircraft concept as a twin engine aircraft with a 7500 nautical mile mission. The engines were modeled as existing technology, in production, bypass ratio seven turbofans. The baseline hybrid wing body aircraft was assessed at 26.4 dB cumulative below the FAA Stage 4 certification level. To determine the potential for noise reduction with relatively near term technologies, seven other configurations were assessed beginning with moving the engines two fan nozzle diameters upstream of the trailing edge and then adding technologies for reduction of the ...

/pdf/hybrid-wing-body-aircraft-system-noise-assessment-with-38lslhe1id.pdf

Hybrid Wing Body Aircraft System Noise Assessment with Propulsion Airframe Aeroacoustic Experiments

This paper presents an assessment of the performance of an embedded propulsion system in the presence of distortion associated with boundary layer ingestion. For fan pressure ratios of interest for civil transports, the benefits of boundary layer ingestion are shown to be very sensitive to the magnitude of fan and duct losses. The distortion transfer across the fan, basically the comparison of the stagnation pressure non-uniformity downstream of the fan to that upstream of the fan, has a major role in determining the impact of boundary layer ingestion on overall fuel burn. This, in turn, puts requirements on the fidelity with which one needs to assess the distortion transfer, and thus the type of models that need to be used in such assessment. For the three-dimensional distortions associated with fuselage boundary layers ingested into a subsonic diffusing inlet, it is found that boundary layer ingestion can provide decreases in fuel burn of several per cent. It is also shown that a promising avenue for mitigating the risks (aerodynamic as well as aeromechanical) in boundary layer ingestion is to mix out the flow before it reaches the engine face.

/pdf/performance-of-a-boundary-layer-ingesting-bli-propulsion-3390bkcayq.pdf

A. P. Plas

Papers

Performance of a Boundary Layer Ingesting (BLI) propulsion system

Performance of a boundary layer (BLI) propulsion system