Date of Award
5-14-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
There is pressing need for emissions reduction and an increase in efficiency for the next generation of commercial aircraft in order to reduce the environmental impact of the aviation sector and combat global climate change. The implementation of alternative fuels as well as new engine and wing designs are actively being explored as methods to reduce emissions. This thesis analyzes the implementation of hydrogen fuel, a transonic truss braced wing and active flow controls as means to improve the performance of a medium range commercial airliner. The widespread adoption of cryogenic liquid hydrogen (LH2) fuel as a green alternative to Jet A has the potential to drastically reduce the environmental impact of aviation. Although liquid hydrogen has higher energy density than jet fuel, high volume cryogenic tanks are necessary requiring a reevaluation of traditional aircraft design. A high aspect ratio transonic truss braced wing (TTBW) has inherent aerodynamic benefits, improved lift-to-drag ratio, in comparison to traditional cantilever wings. Active flow controls in the form of co-flow jets (CFJ) are evaluated as a method to further improve the performance of the transonic truss braced wing. Initial design starts with the fuel tank configuration design and drag optimization of external liquid hydrogen fuel tanks using a MATLAB code. A matrix of configurations is considered with varying volume fuel tanks and fuselage designs. The tradeoff between internal and external fuels tanks is evaluated for efficient hydrogen fuel storage. The aircraft design and analysis tool RDSWin is used to assess aircraft performance in conjunction with aerodynamics, propulsion, and weight estimation methods. The aircraft performance analysis shows the drag reduction of internal tanks in comparison to external stores. The transonic truss braced wing is shown to reduce aircraft fuel burn in comparison to a cantilever wing with similar airfoils. The B767 fuselage with TTBW and internal LH2 tanks is found to have the best potential for a future zero carbon emission liquid hydrogen powered aircraft. Next, the accuracy of numerical methods and turbulence models necessary for further analysis and improvements in aerodynamic performance are examined. Computational fluid dynamics (CFD) is performed using ANSYS Fluent on the NASA juncture flow aircraft model and the ONERA M6 transonic wing model to evaluate the performance of turbulence models in calculating complex flows with separation and shock. This research also analyzes the accuracy of various turbulence models with nonlinear quadratic constitutive relation (QCR) for eddy viscosity in comparison to the linear Boussinesq assumption. The final phase focuses on the integration of the CFJ into a TTBW. Parametric setups are created to sweep through varying angles of attack and jet momentum coefficients. The RAE2822 transonic airfoil is simulated in 2D with and without CFJ in comparison to published data for validation of numerical methods, boundary conditions and grid techniques. The airfoil with and without CFJ is then scaled to the crank chord of the TTBW and simulated at cruise conditions. Large scale 3D simulations are run on the TTBW with and without CFJ to analyze the effect of the truss and active flow controls on aerodynamic performance. It is determined that CFJ can further improve aerodynamic efficiency during cruise for a TTBW.
Language
English (en)
Chair
Ramesh Agarwal