Date of Award
5-9-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
In the effort to combat climate change worldwide, the aviation industry faces particularly complex design challenges in designing new, emission free vehicles. One potential solution to this problem is the use of hydrogen fuel as a means of propulsion. Hydrogen fuel has many benefits over traditional jet fuel such as a higher gravimetric energy density; however, it requires the aircraft to carry large, pressurized, cryogenic fuel tanks. This thesis examines the design challenges, potential solutions, and the analysis methods for the design of a short to medium range hydrogen powered commercial airliner. To accomplish this goal, a comprehensive conceptual design and analysis code called WUADS (Washington University Aircraft Design Software) is developed. WUADS employs a combination of empirical and numerical methods to analyze an arbitrarily input aircraft’s overall weight, propulsive efficiency, and aerodynamic performance. This code is first validated on several existing aircraft to verify the accuracy of the analysis and optimization methodology of WUADS, then it is used to analyze several configurations of hydrogen powered aircraft. The first hydrogen powered configuration tested is a medium range airliner based on the performance metric of the Boeing 737-800, which makes use of propulsion through direct hydrogen combustion. The Preliminary analysis shows that the optimal placement of the required cryogenic hydrogen fuel tanks is inside the fuselage. With this knowledge, a hydrogen powered aircraft configuration is designed and optimized with an extended fuselage to fit the fuel tanks. This configuration demonstrates a clear increase in efficiency over the Boeing 737-800. Next, the design of an electric hydrogen fuel cell powered configuration is analyzed. A system architecture for the electrified powertrain and its required subcomponents is developed and modelled to determine the propulsive efficiency of such a design. These models are used to test three configurations of hydrogen fuel cell powered aircraft which are based on the Cessna 208 Caravan, the Bombardier CRJ-200, and the Boeing 717-200. The models employed for the hydrogen fuel cell powertrain are first validated on the Cessna 208 configuration. Next, the projected component efficiencies at technology levels in the near future are tested on the Bombardier CRJ-200 configuration where it is determined that a hydrogen fuel cell powered aircraft could be highly efficient and technologically viable by the year 2035. Finally, the Boeing 717-200 configuration is used to analyze a hydrogen fuel cell powered configuration’s efficiency against a hydrogen combustion powered configuration at different design ranges. A truss braced wing model is also employed for additional increases to the efficiency. It is determined that the hydrogen fuel cells are effective in design ranges shorter than 2000 nmi; however, the hydrogen combustion may be required beyond this range. With these geometrically optimized designs, a more detailed analysis of the aerodynamic shape optimization of the wing is performed. Both the airfoil and twist distribution across the wing are optimized using machine learning based optimization methods. In this analysis, highly efficient, supercritical airfoils are designed using Bayesian optimization. An artificial neural network model is employed in attempt to increase the computational efficiency and is found to provide near optimal results. The 2D to 3D airfoil mapping methods are then employed to optimize the airfoil distribution of an entire transonic wing.
Language
English (en)
Chair
Ramesh Agarwal