A new turboelectric airliner concept, capable of delivering 17% better efficiency over 2050 projections for standard airliners, was unveiled Monday at the AIAA AVIATION Forum, and a University of Michigan Engineering team played a central role in its development. Yesterday’s technical talk on the project, including work from the U-M team, was delivered to a standing-room-only crowd.
The aircraft design project, led by the hybrid-electric aviation company Electra, is part of NASA’s Advanced Aircraft Concepts for Environmental Sustainability (AACES 2050) program.
The chief contribution by the U-M Aerospace Engineering team—led by Gökçin Çınar, assistant professor of aerospace engineering—was expanding the design space that the team could explore. Both she and Joaquim Martins, the Pauline M. Sherman Collegiate Professor of aerospace engineering, focus on multidisciplinary design and optimization, considering multiple aspects of the aircraft at once.
Multidisciplinary design and optimization
The aerodynamics and structure of the aircraft, as well as its propulsion and heat management systems, are deeply dependent on one another. For instance, changing the shape of the aircraft, or its weight distribution, affects where the engines should be placed and how much thrust they need to generate. Çınar and Martins coded extensions to NASA’s open-source Aviary aircraft design framework, supporting the simultaneous optimization of all three of these aspects of airplanes.
Using this approach, the team evaluated 20 different aircraft architectures and optimized these designs for over 100,000 scenarios. They found low-fidelity simulations preferred highly distributed propulsion—basically, many electric propellers along the wings and in the tail. However, their more advanced high-fidelity simulations demonstrated that the weight, drag and challenges dissipating heat tipped the scales to favor a different design.
“This was one of the findings we scrutinized most carefully, because it challenges some of the assumptions that have shaped parts of the electrified aircraft design literature,” Çınar said.
“Low-fidelity models and first-principles analysis remain essential for exploring large design spaces and down-selecting promising concepts early. But once the expected benefits are narrow and the modeling uncertainty is high, you need multi-fidelity analysis with greater subsystem granularity. That is what we were able to achieve together with Electra: we could move from broad concept exploration to a much more detailed understanding of when electrification actually buys its way onto the aircraft.”
In addition to the aircraft’s overall design, Venkat Viswanathan, professor of aerospace engineering at U-M, provided battery modeling to determine the power requirements and performance of battery packs, their size and weight, as well as heat dissipation and degradation over time. Max Li, U-M assistant professor of aerospace engineering, modeled likely future markets for aircraft, answering questions like, “When and for what routes will airline operators be looking to buy next-generation aircraft?” and “What are their requirements likely to be?”
Partially electrified for boundary-layer ingestion
Optimization pointed the Electra-led team toward a partially electrified design, with a conventional turbofan engine on each wing and electric fans near the rear of the fuselage. The concept uses a wider “double-bubble” fuselage first proposed by a Massachusetts Institute of Technology-led team, so the aircraft body itself contributes lift rather than simply carrying passengers. The electric fans accelerate the slower-moving air over the top of the aircraft, providing thrust while reducing the energy lost in the aircraft’s wake. Known as fuselage boundary-layer ingestion, this advanced design reduces the thrust that the underwing engines must generate.
Three more presentations on the project will be made at AVIATION today, with a panel discussion tomorrow. Ph.D. student Sinan Abdulhak received the Neil Y. Chen Memorial Best Student Paper Award for his market-modeling research.
The collaboration also included partners from across academia and industry, including American Airlines, Honeywell Aerospace, Lockheed Martin Skunk Works, Hinetics, Massachusetts Institute of Technology and University of California, Irvine.