Yu Cai
(Advisor: Prof. Dimitri N. Mavris)

will defend a doctoral thesis entitled,

Multi-mission Sizing and Analysis Framework for Aircraft and Subsystem Architectures with Electrified Propulsion Systems in Conceptual Design

On

Wednesday, April 12th at 11:00 a.m. EDT

Weber Space Science and Technology Building, CoVE
https://gatech.zoom.us/j/95462996483?pwd=NlV3amx4YXpTU2t5eTZQUTZ5WlJIQT09

Abstract
Novel, revolutionary technologies for aircraft systems are expected to emerge in the coming decades in order to meet ambitious goals aimed at significantly improving fuel burn and emissions. Among these revolutionary technologies are electrified aircraft propulsion and electrified aircraft subsystems. While the aviation industry has been making progress in developing electrified subsystem architectures, which have demonstrated superior performance on recent commercial airliners, it remains unclear, with electrified propulsion system, what impacts will electrified subsystems have on vehicle sizing, how different subsystem architectures perform in off-design missions, whether all-electric subsystem architectures are optimal solutions, and how sensitive the predicted performance is with respect to modeling assumptions and evolving technological state-of-the-art.

This dissertation aims to develop a multidisciplinary design framework which enables designers to perform integrated vehicle and subsystem sizing at the conceptual design phase, with special emphasis on electrified propulsion system, more-electric subsystem architectures, and multi-mission performance assessment.

The first objective is to perform initial sizing of aircraft subsystems in parallel to aircraft and hybrid electric propulsion system sizing using suitable methods at the conceptual design stage. A graph-based representation of subsystem energy flow is demonstrated to accurately and most efficiently resolve the energy flow between subsystems for both conventional and electrified architectures. A comparative assessment between four subsystem architectures demonstrates that the proposed framework is able to perform subsystem sizing, propagate the impacts of the subsystem weights, drag penalty, and secondary power offtake to the mission level, and decompose the vehicle-level impacts due to individual subsystems.

The second objective is to evaluate the payload-range characteristics of hybrid-electric aircraft with electrified subsystem architectures and to compare the multi-mission performance across design candidates. By comparing the performance of subsystem architectures for off-design cost missions rather than for the design mission, the results are more representative for the projected market of the new vehicle design, and therefore will facilitate decision making regarding optimal subsystem architectures. A multi-objective assessment implies trade-off between the weight metrics and the efficiency metrics, which is primarily attributed to the electrification of ice protection system and the thermal management system.

The third objective is to assess sensitivities of performance metrics to epistemic uncertainty, technological state-of-the-art, vehicle-level design variables, and off-design mission parameters. The ability to vary these parameters and to propagate them into respective analysis modules in the design framework allow designers to quantify the impacts of various uncertainties on the predicted subsystem and vehicle performance. A sensitivity analysis shows that advancements in the battery technology changes the performance ranking of subsystem architectures. Examination of the payload-range characteristics reveals that the electrified subsystem architectures exhibit the most advantages in fuel and energy consumption when operating missions of short to medium range in comparison to the conventional architecture.

In the end, a subsystem architecture design space is explored with all the capabilities developed above. Assuming a technology level in the next decade for electric components, electrifying the actuation systems and the ice protection system is preferred to optimize the maximum takeoff weight, the operating empty weight, and the fuel and energy performance, while the thermal management system and the power generation and distribution system are desired to remain conventional. However, subsystem electrification offers a new operational strategy at the vehicle level, known as electric taxiing, which is found to boost the fuel and energy performance of compatible electrified subsystem architectures and results in a trade-off between the weights and the fuel and energy performance metrics.

Committee

• Prof. Dimitri N. Mavris – School of Aerospace Engineering (advisor)
• Prof. Daniel P. Schrage – School of Aerospace Engineering
• Prof. Brian J. German – School of Aerospace Engineering
• Prof. Gokcin Cinar – University of Michigan
• Dr. Jonathan C. Gladin – School of Aerospace Engineering